101
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de Buck MHS, Jezzard P, Jeong H, Hess AT. An investigation into the minimum number of tissue groups required for 7T in-silico parallel transmit electromagnetic safety simulations in the human head. Magn Reson Med 2020; 85:1114-1122. [PMID: 32845034 DOI: 10.1002/mrm.28467] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/22/2020] [Accepted: 07/16/2020] [Indexed: 02/03/2023]
Abstract
PURPOSE Safety limits for the permitted specific absorption rate (SAR) place restrictions on pulse sequence design, especially at ultrahigh fields (≥ 7 tesla). Due to intersubject variability, the SAR is usually conservatively estimated based on standard human models that include an applied safety margin to ensure safe operation. One approach to reducing the restrictions is to create more accurate subject-specific models from their segmented MR images. This study uses electromagnetic simulations to investigate the minimum number of tissue groups required to accurately determine SAR in the human head. METHODS Tissue types from a fully characterized electromagnetic human model with 47 tissue types in the head and neck region were grouped into different tissue clusters based on the conductivities, permittivities, and mass densities of the tissues. Electromagnetic simulations of the head model inside a parallel transmit head coil at 7 tesla were used to determine the minimum number of required tissue clusters to accurately determine the subject-specific SAR. The identified tissue clusters were then evaluated using 2 additional well-characterized electromagnetic human models. RESULTS A minimum of 4-clusters-plus-air was found to be required for accurate SAR estimation. These tissue clusters are centered around gray matter, fat, cortical bone, and cerebrospinal fluid. For all 3 simulated models, the parallel transmit maximum 10g SAR was consistently determined to within an error of <12% relative to the full 47-tissue model. CONCLUSION A minimum of 4-clusters-plus-air are required to produce accurate personalized SAR simulations of the human head when using parallel transmit at 7 tesla.
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Affiliation(s)
- Matthijs H S de Buck
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Peter Jezzard
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Hongbae Jeong
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Maryland, USA.,Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Aaron T Hess
- Oxford Centre for Clinical Magnetic Resonance Research, Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom.,BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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102
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Park JS. Neuroman: Voxel Phantoms from Surface Models of 300 Head Structures Including 12 Pairs of Cranial Nerves. HEALTH PHYSICS 2020; 119:192-205. [PMID: 31855595 DOI: 10.1097/hp.0000000000001186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
For a precise simulation of electromagnetic radiation effects, voxel phantoms require detailed structures to approximate humans. The phantoms currently used still do not have sophisticated structures. This paper presents voxel and surface models of 300 head structures with cranial nerves and reports on a technique for voxel reconstruction of the cranial nerves having very thin and small structures. In real-color sectioned images of the head (voxel size: 0.1 mm), 300 structures were segmented using Photoshop. A surface reconstruction was performed automatically on Mimics. Voxel conversion was run on Voxel Studio. The abnormal shapes of the voxel models were found and classified into three types: thin cord, thin layers, and thin parts in the structures. The abnormal voxel models were amended using extended, filled, and manual voxelization methods devised for this study. Surface models in STL format and as PDF files of the 300 head structures were produced. The STL format has good scalability, so it can be used in most three-dimensional surface model software. The PDF file is very user friendly for students and researchers who want to learn the head anatomy. Voxel models of 300 head structures were produced (TXT format), and their voxel quantity and weight were measured. A voxel model is difficult to handle, and the surface model cannot use the radiation simulation. Consequently, the best method for making precise phantoms is one in which the flaws of the voxel and surface models complement each other, as in the present study.
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Affiliation(s)
- Jin Seo Park
- Department of Anatomy, Dongguk University School of Medicine, Republic of Korea
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103
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Ahn J, Hong SE, Kim H, Chun Y, Choi HD, Kim K, Andrés B, Choi J, Ahn S. COMPLIANCE TESTING FOR HUMAN BODY MODEL EXPOSURE TO ELECTROMAGNETIC FIELDS FROM A HIGH-POWER WIRELESS CHARGING SYSTEM FOR DRONES. RADIATION PROTECTION DOSIMETRY 2020; 189:13-27. [PMID: 32090242 DOI: 10.1093/rpd/ncaa008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 01/10/2020] [Accepted: 01/15/2020] [Indexed: 06/10/2023]
Abstract
Recently, a wireless charging system (WCS) for drones has been extensively studied, although standards for compliance testing of a WCS for drones have yet to be established. In this study, we propose methods for human exposure assessments of a WCS for drones by comprehensively considering the various positions of the system and the postures of human body models. The electromagnetic fields from a WCS are modeled and the internal quantities of the human body models, consisting of current density, internal electric field and specific absorption rate, are calculated. The incident fields around the WCS and the internal quantities are analyzed at 140 kHz, which is the operating frequency of the WCS applied. Results of an exposure assessment based on the confirmed worst-case scenario are presented. In addition, the internal quantities depending on the human body models and the material characteristics of the simplified models are also discussed using four different anatomical and simplified human body models.
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Affiliation(s)
- Jangyong Ahn
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
| | - Seon-Eui Hong
- Radio Technology Research Department, Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Haerim Kim
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
| | - Yangbae Chun
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
| | - Hyung-Do Choi
- Radio Technology Research Department, Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea
| | - Kibeom Kim
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
| | - Brito Andrés
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
| | - Junsung Choi
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
| | - Seungyoung Ahn
- The CCS Graduate School of Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejoen, Republic of Korea
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104
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Burke MJ, Joutsa J, Cohen AL, Soussand L, Cooke D, Burstein R, Fox MD. Mapping migraine to a common brain network. Brain 2020; 143:541-553. [PMID: 31919494 DOI: 10.1093/brain/awz405] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 10/15/2019] [Accepted: 11/11/2019] [Indexed: 11/14/2022] Open
Abstract
Inconsistent findings from migraine neuroimaging studies have limited attempts to localize migraine symptomatology. Novel brain network mapping techniques offer a new approach for linking neuroimaging findings to a common neuroanatomical substrate and localizing therapeutic targets. In this study, we attempted to determine whether neuroanatomically heterogeneous neuroimaging findings of migraine localize to a common brain network. We used meta-analytic coordinates of decreased grey matter volume in migraineurs as seed regions to generate resting state functional connectivity network maps from a normative connectome (n = 1000). Network maps were overlapped to identify common regions of connectivity across all coordinates. Specificity of our findings was evaluated using a whole-brain Bayesian spatial generalized linear mixed model and a region of interest analysis with comparison groups of chronic pain and a neurologic control (Alzheimer's disease). We found that all migraine coordinates (11/11, 100%) were negatively connected (t ≥ ±7, P < 10-6 family-wise error corrected for multiple comparisons) to a single location in left extrastriate visual cortex overlying dorsal V3 and V3A subregions. More than 90% of coordinates (10/11) were also positively connected with bilateral insula and negatively connected with the hypothalamus. Bayesian spatial generalized linear mixed model whole-brain analysis identified left V3/V3A as the area with the most specific connectivity to migraine coordinates compared to control coordinates (voxel-wise probability of ≥90%). Post hoc region of interest analyses further supported the specificity of this finding (ANOVA P = 0.02; pairwise t-tests P = 0.03 and P = 0.003, respectively). In conclusion, using coordinate-based network mapping, we show that regions of grey matter volume loss in migraineurs localize to a common brain network defined by connectivity to visual cortex V3/V3A, a region previously implicated in mechanisms of cortical spreading depression in migraine. Our findings help unify migraine neuroimaging literature and offer a migraine-specific target for neuromodulatory treatment.
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Affiliation(s)
- Matthew J Burke
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Harquail Centre for Neuromodulation and Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Toronto, ON, Canada.,Neuropsychiatry Program, Department of Psychiatry, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada
| | - Juho Joutsa
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Turku Brain and Mind Center, Department of Neurology, University of Turku, Turku, Finland.,Division of Clinical Neurosciences and Turku PET Center, Turku University Hospital, Turku, Finland
| | - Alexander L Cohen
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Louis Soussand
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Danielle Cooke
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Rami Burstein
- Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Michael D Fox
- Berenson-Allen Center for Noninvasive Brain Stimulation, Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.,Athinoula A. Martinos Centre for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
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105
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Kublanov VS, Borisov VI, Babich MV. Simulation the distribution of thermodynamic temperatures and microwave radiation of the human head. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2020; 190:105377. [PMID: 32065933 DOI: 10.1016/j.cmpb.2020.105377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 01/20/2020] [Accepted: 01/29/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND OBJECTIVE The influence of biophysical parameters on the formation of microwave radiation of the human head is poorly studied. Existing approaches to modeling microwave radiation of the human head have limitations associated with simplifying the geometry of human anatomy. The article proposes methodological solutions for numerical modeling of microwave radiation of the brain biological tissues using the geometry obtained from MRI data. METHODS The geometrical characteristics of biological tissues in model are determined using an MRI image of the head. The methodology proposed in the article allows simulation of a human body voxel models performed the Pennes bio-heat transfer equation using the Fenix software package. RESULTS Modeling evaluations have shown that anatomical tissues heterogeneities on the surface of the head form temperature gradient of up to 2.0 K, and changes of the microwave radiation up to 0.3 K. CONCLUSIONS Verification data made by IR thermograph practically coincide with the results of numerical modeling. The fluctuations of the brain microwave radiation are not only the result of thermal processes in its tissues, but are determined by the dynamics of its thermoregulation processes and are an indicator of changes in the physiological processes occurring in it.
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106
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Niederer SA, Aboelkassem Y, Cantwell CD, Corrado C, Coveney S, Cherry EM, Delhaas T, Fenton FH, Panfilov AV, Pathmanathan P, Plank G, Riabiz M, Roney CH, dos Santos RW, Wang L. Creation and application of virtual patient cohorts of heart models. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190558. [PMID: 32448064 PMCID: PMC7287335 DOI: 10.1098/rsta.2019.0558] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/06/2020] [Indexed: 05/21/2023]
Abstract
Patient-specific cardiac models are now being used to guide therapies. The increased use of patient-specific cardiac simulations in clinical care will give rise to the development of virtual cohorts of cardiac models. These cohorts will allow cardiac simulations to capture and quantify inter-patient variability. However, the development of virtual cohorts of cardiac models will require the transformation of cardiac modelling from small numbers of bespoke models to robust and rapid workflows that can create large numbers of models. In this review, we describe the state of the art in virtual cohorts of cardiac models, the process of creating virtual cohorts of cardiac models, and how to generate the individual cohort member models, followed by a discussion of the potential and future applications of virtual cohorts of cardiac models. This article is part of the theme issue 'Uncertainty quantification in cardiac and cardiovascular modelling and simulation'.
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Affiliation(s)
| | | | | | | | | | - E. M. Cherry
- Georgia Institute of Technology, Atlanta, GA, USA
| | - T. Delhaas
- Maastricht University, Maastricht, the Netherlands
| | - F. H. Fenton
- Georgia Institute of Technology, Atlanta, GA, USA
| | - A. V. Panfilov
- Ghent University, Gent, Belgium
- Laboratory of Computational Biology and Medicine, Ural Federal University, Ekaterinburg, Russia
| | - P. Pathmanathan
- Center for Devices and Radiological Health, U.S. Food and Administration, Rockville, MD, USA
| | - G. Plank
- Medical University of Graz, Graz, Austria
| | | | | | | | - L. Wang
- Rochester Institute of Technology, La JollaRochester, NY, USA
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107
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Meliadò EF, Sbrizzi A, van den Berg CAT, Steensma BR, Luijten PR, Raaijmakers AJE. Conditional safety margins for less conservative peak local SAR assessment: A probabilistic approach. Magn Reson Med 2020; 84:3379-3395. [PMID: 32492249 PMCID: PMC7540599 DOI: 10.1002/mrm.28335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 04/28/2020] [Accepted: 05/01/2020] [Indexed: 12/17/2022]
Abstract
Purpose The introduction of a linear safety factor to address peak local specific absorption rate (pSAR10g) uncertainties (eg, intersubject variation, modeling inaccuracies) bears one considerable drawback: It often results in over‐conservative scanning constraints. We present a more efficient approach to define a variable safety margin based on the conditional probability density function of the effectively obtained pSAR10g value, given the estimated pSAR10g value. Methods The conditional probability density function can be estimated from previously simulated data. A representative set of true and estimated pSAR10g samples was generated by means of our database of 23 subject‐specific models with an 8‐fractionated dipole array for prostate imaging at 7 T. The conditional probability density function was calculated for each possible estimated pSAR10g value and used to determine the corresponding safety margin with an arbitrary low probability of underestimation. This approach was applied to five state‐of‐the‐art local SAR estimation methods, namely: (1) using just the generic body model “Duke”; (2) using our model library to assess the maximum pSAR10g value over all models; (3) using the most representative “local SAR model”; (4) using the five most representative local SAR models; and (5) using a recently developed deep learning–based method. Results Compared with the more conventional safety factor, the conditional safety‐margin approach results in lower (up to 30%) mean overestimation for all investigated local SAR estimation methods. Conclusion The proposed probabilistic approach for pSAR10g correction allows more accurate local SAR assessment with much lower overestimation, while a predefined level of underestimation is accepted (eg, 0.1%).
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Affiliation(s)
- Ettore Flavio Meliadò
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Tesla Dynamic Coils, Zaltbommel, The Netherlands
| | - Alessandro Sbrizzi
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Department of Radiotherapy, Division of Imaging & Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bart R Steensma
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Peter R Luijten
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alexander J E Raaijmakers
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands.,Biomedical Image Analysis, Department Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
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108
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Assessment of Exposure to Electric Vehicle Inductive Power Transfer Systems: Experimental Measurements and Numerical Dosimetry. SUSTAINABILITY 2020. [DOI: 10.3390/su12114573] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
High-power inductive power transfer (IPT) systems for charging light and heavy electric vehicles pose safety concerns if they are installed in uncontrolled environments. Within the framework of the European Project EMPIR-16ENG08 MICEV, a wide experimental and numerical study was conducted to assess the exposure of the general public to IPT stray magnetic fields for two different exposure scenarios: (1) for an IPT model system derived from the SAE J2954 standard operating at 85 kHz for a light electric vehicle coupled with the model of a realistic car-body model; and (2) for an IPT model system with a maximum rated power of 50 kW at 27.8 kHz for a real minibus that was reproduced with some simplifications in two different 3D finite element method (FEM) simulation tools (Opera 3D and CST software). An ad hoc measurement survey was carried out at the minibus charging station to validate the simulations of the real bus station for both aligned and misaligned IPT coils. Based on this preliminary study, a safety factor was chosen to ensure a conservative dosimetric analysis with respect to the model approximations. As highlighted in this study, the vehicle-body serves as an efficient screen to reduce the magnetic field by at least three orders of magnitude close to the coils. By applying FEM, computed spatial distribution to the Sim4Life software, the exposure of three Virtual Population human anatomical phantoms (one adult, one child, and a newborn) was assessed. The three phantoms were placed in different postures and locations for both exposure scenarios. The basic restriction limits, established by the current guidelines, were never exceeded within the vehicles; however, the basic restrictions were exceeded when an adult crouched outside the minibus, i.e., near the coils, or when a newborn was placed in the same location. Borderline values were observed in the light car. In the case of the bus, limits coming from the Institute of Electrical and Electronics Engineers (IEEE) guidelines are never exceeded, while basic restrictions coming from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines are exceeded up to 12% for an adult and up to 38% for a newborn. This paper presents novel dosimetric data generated in an IPT system for heavy vehicles and confirms some of the literature data on light vehicles.
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109
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Winter L, Seifert F, Zilberti L, Murbach M, Ittermann B. MRI‐Related Heating of Implants and Devices: A Review. J Magn Reson Imaging 2020; 53:1646-1665. [DOI: 10.1002/jmri.27194] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Lukas Winter
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Frank Seifert
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica Torino Italy
| | - Manuel Murbach
- ZMT Zurich MedTech AG Zurich Switzerland
- Institute for Molecular Instrumentation and Imaging (i3M) Universidad Politécnica de Valencia (UPV) Valencia Spain
| | - Bernd Ittermann
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
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110
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Wi W, Park SM, Shin BS. Computed Tomography-Based Preoperative Simulation System for Pedicle Screw Fixation in Spinal Surgery. J Korean Med Sci 2020; 35:e125. [PMID: 32383365 PMCID: PMC7211513 DOI: 10.3346/jkms.2020.35.e125] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 03/01/2020] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND A preoperative planning system facilitates improving surgical outcomes that depend on the experience of the surgeons, thanks to real-time interaction between the system and surgeons. It visualizes intermediate surgical planning results to help surgeons discuss the planning. The purpose of this study was to demonstrate the use of a newly-developed preoperative planning system for surgeons less experienced in pedicle-screw fixation in spinal surgery, especially on patients with anatomical variations. METHODS The marching cubes algorithm, a typical surface extraction technique, was applied to computed tomography (CT) images of vertebrae to enable three-dimensional (3D) reconstruction of a spinal mesh. Real-time processing of such data is difficult, as the surface mesh extracted from high-resolution CT data is rough, and the size of the mesh is large. To mitigate these factors, Laplacian smoothing was applied, followed by application of a quadric error metric-based mesh simplification to reduce the mesh size for the level-of-detail (LOD) image. Taubin smoothing was applied to smooth out the rough surface. On a multiplanar reconstruction (MPR) cross-sectional image or a 3D model view, the insertion position and orientation of the pedicle screw were manipulated using a mouse. The results after insertion were then visualized in each image. RESULTS The system was used for pre-planning pedicle-screw fixation in spinal surgery. Using any pointing device such as a mouse, surgeons can manipulate the position and angle of the screws. The pedicle screws were easy to manipulate intuitively on the MPR images, and the accuracy of screw fixation was confirmed on a trajectory view and 3D images. After surgery, CT scans were performed again, and the CT images were checked to ensure that the screws were inserted properly. CONCLUSION The preoperative planning system allows surgeons and students who are not familiar with pedicle-screw fixation to safely undertake surgery following preoperative planning. It also provides opportunities for screw-fixation training and simulation.
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Affiliation(s)
- Woochan Wi
- Department of Computer Engineering, Inha University, Incheon, Korea
| | - Sang Min Park
- Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Byung Seok Shin
- Department of Computer Engineering, Inha University, Incheon, Korea.
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111
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Audenaert EA, Khanduja V, Claes P, Malviya A, Steenackers G. Mechanics of Psoas Tendon Snapping. A Virtual Population Study. Front Bioeng Biotechnol 2020; 8:264. [PMID: 32292780 PMCID: PMC7118580 DOI: 10.3389/fbioe.2020.00264] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/13/2020] [Indexed: 12/24/2022] Open
Abstract
Internal snapping of the psoas tendon is a frequently reported condition, especially in young adolescents involved in sports. It is defined as an increased tendon excursion over bony or soft tissue prominence causing local irritation and inflammation of the tendon leading to groin pain and often is accompanied by an audible snap. Due to the lack of detailed dynamic visualization means, the exact mechanism of the condition remains poorly understood and different theories have been postulated related to the etiology and its location about the hip. In the present study we simulated psoas tendon behavior in a virtual population of 40,000 anatomies and compared tendon movement during combined abduction, flexion and external rotation and back to neutral extension and adduction. At risk phenotyopes for tendon snapping were defined as the morphologies presenting with excess tendon movement. There were little differences in tendon movement between the male and female models. In both populations, abnormal tendon excursion correlated with changes in mainly the femoral anatomy (male r = 0.72, p < 0.001, female r = 0.66, p < 0.001): increased anteversion and valgus as well as a decreasing femoral offset and ischiofemoral distance. The observed combination of shape components correlating with excess tendon movement in essence presented with a medial positioning of the minor trochanter. This finding suggest that psoas snapping and ischiofemoral impingement are possibly two presentations of a similar underlying rotational dysplasia of the femur.
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Affiliation(s)
- Emmanuel A Audenaert
- Department of Orthopedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium.,Department of Trauma and Orthopedics, Addenbrooke's Hospital, Cambridge University Hospitals National Health Service Foundation Trust, Cambridge, United Kingdom.,Op3Mech Research Group, Department of Electromechanics, University of Antwerp, Antwerp, Belgium.,Department of Human Structure and Repair, Ghent University, Ghent, Belgium
| | - Vikas Khanduja
- Department of Trauma and Orthopedics, Addenbrooke's Hospital, Cambridge University Hospitals National Health Service Foundation Trust, Cambridge, United Kingdom
| | - Peter Claes
- Medical Imaging Research Center (MIRC), University Hospitals Leuven, Leuven, Belgium.,Department of Electrical Engineering/Processing Speech and Images, KU Leuven, Leuven, Belgium.,Department of Human Genetics, KU Leuven, Leuven, Belgium.,Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, VIC, Australia
| | - Ajay Malviya
- Department of Orthopedic Surgery and Traumatology, Northumbria National Health Service Foundation Trust, Newcastle upon Tyne, United Kingdom.,Department of Regenerative Medicine, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Gunther Steenackers
- Op3Mech Research Group, Department of Electromechanics, University of Antwerp, Antwerp, Belgium
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112
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Lloyd B, Farcito S, Cassarà A, Zhuang K, Neufeld E, Kuster N. SPARC: Development of Human and Rodent Neuro‐Functionalized Computational Anatomical Models with Detailed Mapping of Peripheral Nervous System. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.07492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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113
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Erturk MA, Panken E, Conroy MJ, Edmonson J, Kramer J, Chatterton J, Banerjee SR. Predicting in vivo MRI Gradient-Field Induced Voltage Levels on Implanted Deep Brain Stimulation Systems Using Neural Networks. Front Hum Neurosci 2020; 14:34. [PMID: 32153375 PMCID: PMC7044348 DOI: 10.3389/fnhum.2020.00034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 01/23/2020] [Indexed: 11/15/2022] Open
Abstract
Introduction MRI gradient-fields may induce extrinsic voltage between electrodes and conductive neurostimulator enclosure of implanted deep brain stimulation (DBS) systems, and may cause unintended stimulation and/or malfunction. Electromagnetic (EM) simulations using detailed anatomical human models, therapy implant trajectories, and gradient coil models can be used to calculate clinically relevant induced voltage levels. Incorporating additional anatomical human models into the EM simulation library can help to achieve more clinically relevant and accurate induced voltage levels, however, adding new anatomical human models and developing implant trajectories is time-consuming, expensive and not always feasible. Methods MRI gradient-field induced voltage levels are simulated in six adult human anatomical models, along clinically relevant DBS implant trajectories to generate the dataset. Predictive artificial neural network (ANN) regression models are trained on the simulated dataset. Leave-one-out cross validation is performed to assess the performance of ANN regressors and quantify model prediction errors. Results More than 180,000 unique gradient-induced voltage levels are simulated. ANN algorithm with two fully connected layers is selected due to its superior generalizability compared to support vector machine and tree-based algorithms in this particular application. The ANN regression model is capable of producing thousands of gradient-induced voltage predictions in less than a second with mean-squared-error less than 200 mV. Conclusion We have integrated machine learning (ML) with computational modeling and simulations and developed an accurate predictive model to determine MRI gradient-field induced voltage levels on implanted DBS systems.
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Affiliation(s)
- M Arcan Erturk
- Restorative Therapies Group, Implantables R&D, Medtronic PLC, Minneapolis, MN, United States
| | - Eric Panken
- Restorative Therapies Group, Implantables R&D, Medtronic PLC, Minneapolis, MN, United States
| | - Mark J Conroy
- Restorative Therapies Group, Implantables R&D, Medtronic PLC, Minneapolis, MN, United States
| | - Jonathan Edmonson
- Cardiac Rhythm Heart Failure, Device Product Engineering, Medtronic PLC, Minneapolis, MN, United States
| | - Jeff Kramer
- Restorative Therapies Group, Implantables R&D, Medtronic PLC, Minneapolis, MN, United States
| | - Jacob Chatterton
- Restorative Therapies Group, Implantables R&D, Medtronic PLC, Minneapolis, MN, United States
| | - S Riki Banerjee
- Restorative Therapies Group, Implantables R&D, Medtronic PLC, Minneapolis, MN, United States
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114
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Colella M, Camera F, Capone F, Setti S, Cadossi R, Di Lazzaro V, Apollonio F, Liberti M. Patient Semi-specific Computational Modeling of Electromagnetic Stimulation Applied to Neuroprotective Treatments in Acute Ischemic Stroke. Sci Rep 2020; 10:2945. [PMID: 32075993 PMCID: PMC7031527 DOI: 10.1038/s41598-020-59471-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 01/13/2020] [Indexed: 11/21/2022] Open
Abstract
Neuroprotective effects of pulsed electromagnetic fields (PEMFs) have been demonstrated both in vivo and in vitro. Moreover, preliminary clinical studies have been conducted and suggested PEMFs as a possible alternative therapy to treat acute ischemic stroke. In this work, we show that it's possible to build-up a patient semi-specific head model, where the 3D reconstruction of the ischemic lesion of the patient under treatment is inserted in the head of the human body model "Duke" (v.1.0, Zurich MedTech AG). The semi-specific model will be used in the randomized, placebo-controlled, double-blind study currently ongoing. Three patients were modelled and simulated, and results showed that each ischemic lesion experiences a magnetic flux density field comparable to the one for which biological effects have been attested. Such a kind of dosimetric analysis reveals a reliable tool to assess the correlation between levels of exposure and the beneficial effect. Thus, once the on-going double blind study is complete it will prove if PEMFs treatment triggers a clinical effect, and we will then be able to characterize a dose-response curve with the methodology arranged in this study.
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Affiliation(s)
- Micol Colella
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome "La Sapienza", Rome, Italy
| | - Francesca Camera
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome "La Sapienza", Rome, Italy
| | - Fioravante Capone
- Unit of Neurology, Neurophysiology, Neurobiology, Department of Medicine, Università Campus Bio-Medico di Roma, Rome, Italy
| | | | | | - Vincenzo Di Lazzaro
- Unit of Neurology, Neurophysiology, Neurobiology, Department of Medicine, Università Campus Bio-Medico di Roma, Rome, Italy
| | - Francesca Apollonio
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome "La Sapienza", Rome, Italy
- Pervasive Electromagnetics Lab, University of Rome Tor Vergata, Rome, Italy
| | - Micaela Liberti
- Department of Information Engineering, Electronics and Telecommunications (DIET), University of Rome "La Sapienza", Rome, Italy.
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Urban M, Orglmeister R. Surface Potential Simulation for Robust Electrode Placement by MRI Based Human Phantom with FEM Based Quasi-Static Solver for Bioimpedance Measurement .. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:3972-3977. [PMID: 31946742 DOI: 10.1109/embc.2019.8856954] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Estimating cardiac output (CO) and thoracic fluid content (TFC) by non-invasive measurement of thoracic electrical bioimpedance (TEB) is on the rise of becoming clinically established. Dynamic fluid management and detecting and trending excess quasi-static thoracic fluids are of particular interest to benefit the critically ill patient. While the advantages such as easy application and non-invasive assessment are intriguing, there are some challenges. In addition to artifacts due to the patient's movement, instability of the electrode-skin interfaces, the accuracy of the applied current and varying cable capacity because of motion, exact placement of electrodes - or lack thereof - must be considered. In particular the robustness of the electrode placement, i.e., the insensitivity to inaccuracy of electrode placement (actual sensor from the nominal). We propose a new technique for evaluation of electrode placement by simulation with MRI based human phantoms with FEM based quasi-static solver for bioimpedance measurement. Results: We identified alternative electrode positions which lead to an increase in robustness of bioimpedance measurements of up to 9.5 times compared to the standard electrode placement. Simulations suggested an improvement in ECG signal quality which was confirmed by a subject measurement.
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116
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Fiocchi S, Chiaramello E, Bonato M, Tognola G, Catalucci D, Parazzini M, Ravazzani P. Computational simulation of electromagnetic fields on human targets for magnetic targeting applications. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:5674-5677. [PMID: 31947140 DOI: 10.1109/embc.2019.8857364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In the last few years, the use of nanoparticles for therapeutic applications has attracted the interest of many scientists, who are looking for effective methods to target nanoparticles linked to drugs directly to the diseased organs. Among them, magnetic targeting consists of magnetic systems (magnets or coils) which can impress high gradient magnetic fields and then magnetic forces on the magnetic nanoparticles. Despite some studies have reported an effective improvement in drug delivery by using this technique, there is still a paucity of studies able to quantify and explain the experimental results. In this scenario, "in silico" models allow to analyze and compare different magnetic targeting systems in their ability to generate the required magnetic field gradient for specific human targets.In this paper we then evaluated, by means of computational electromagnetics techniques, the attitude of various ad-hoc designed magnetic systems in targeting the heart tissues of differently aged human anatomical models.
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117
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Arduino A, Bottauscio O, Brühl R, Chiampi M, Zilberti L. In silico evaluation of the thermal stress induced by MRI switched gradient fields in patients with metallic hip implant. ACTA ACUST UNITED AC 2019; 64:245006. [DOI: 10.1088/1361-6560/ab5428] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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118
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Abaci Turk E, Yetisir F, Adalsteinsson E, Gagoski B, Guerin B, Grant PE, Wald LL. Individual variation in simulated fetal SAR assessed in multiple body models. Magn Reson Med 2019; 83:1418-1428. [PMID: 31626373 DOI: 10.1002/mrm.28006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 08/23/2019] [Accepted: 08/30/2019] [Indexed: 11/06/2022]
Abstract
PURPOSE We generate 12 models from 4 pregnant individuals to evaluate individual differences in local specific absorption rate (SAR) for differing body habitus and fetal and maternal positions. METHODS Structural MR images from 4 pregnant subjects (including supine and left-lateral maternal positions) were manually segmented to create 12 body models by rotating the fetus, modifying the fat content, and altering the maternal arm position in 1 of the subjects. Electromagnetic simulations modeled at 3 Tesla determined the average and peak local SAR in the maternal trunk, fetus, fetal brain, and amniotic fluid. RESULTS We observed a significant range of fetal and maternal peak local SAR across the models (maternal trunk: 19.14-44.03 watts/kg, fetus: 9.93-18.79 watts/kg, fetal brain 3.36-10.3 watts/kg). We found that maternal body habitus changes introduced a significant variation in the maternal peak local SAR but not the fetal local SAR. However, the maternal position (either rotating the mother to left-lateral position or altering the arm position) introduced changes in fetal peak local SAR (range: 11.9-17.9 watts/kg). Rotating the fetus also introduced variation in the fetal and fetal brain peak local SAR. CONCLUSION The observed variation in SAR emphasizes the need for more anatomical models to enable better safety management of individuals during fetal MRI, including a wider range of gestational ages.
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Affiliation(s)
- Esra Abaci Turk
- Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children's Hospital, Boston, Massachusetts
| | - Filiz Yetisir
- Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children's Hospital, Boston, Massachusetts
| | - Elfar Adalsteinsson
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts.,Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts.,Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Borjan Gagoski
- Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children's Hospital, Boston, Massachusetts
| | - Bastien Guerin
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - P Ellen Grant
- Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children's Hospital, Boston, Massachusetts
| | - Lawrence L Wald
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts.,Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts
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119
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Capogrosso M, Gandar J, Greiner N, Moraud EM, Wenger N, Shkorbatova P, Musienko P, Minev I, Lacour S, Courtine G. Advantages of soft subdural implants for the delivery of electrochemical neuromodulation therapies to the spinal cord. J Neural Eng 2019; 15:026024. [PMID: 29339580 DOI: 10.1088/1741-2552/aaa87a] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE We recently developed soft neural interfaces enabling the delivery of electrical and chemical stimulation to the spinal cord. These stimulations restored locomotion in animal models of paralysis. Soft interfaces can be placed either below or above the dura mater. Theoretically, the subdural location combines many advantages, including increased selectivity of electrical stimulation, lower stimulation thresholds, and targeted chemical stimulation through local drug delivery. However, these advantages have not been documented, nor have their functional impact been studied in silico or in a relevant animal model of neurological disorders using a multimodal neural interface. APPROACH We characterized the recruitment properties of subdural interfaces using a realistic computational model of the rat spinal cord that included explicit representation of the spinal roots. We then validated and complemented computer simulations with electrophysiological experiments in rats. We additionally performed behavioral experiments in rats that received a lateral spinal cord hemisection and were implanted with a soft interface. MAIN RESULTS In silico and in vivo experiments showed that the subdural location decreased stimulation thresholds compared to the epidural location while retaining high specificity. This feature reduces power consumption and risks of long-term damage in the tissues, thus increasing the clinical safety profile of this approach. The hemisection induced a transient paralysis of the leg ipsilateral to the injury. During this period, the delivery of electrical stimulation restricted to the injured side combined with local chemical modulation enabled coordinated locomotor movements of the paralyzed leg without affecting the non-impaired leg in all tested rats. Electrode properties remained stable over time, while anatomical examinations revealed excellent bio-integration properties. SIGNIFICANCE Soft neural interfaces inserted subdurally provide the opportunity to deliver electrical and chemical neuromodulation therapies using a single, bio-compatible and mechanically compliant device that effectively alleviates locomotor deficits after spinal cord injury.
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Affiliation(s)
- Marco Capogrosso
- Center for Neuroprosthetics and Brain Mind Institute, School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland. Department of Medicine, Platform of Translational Neuroscience, University of Fribourg, Fribourg, Switzerland
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Yao A, Zastrow E, Cabot E, Lloyd B, Schneider B, Kainz W, Kuster N. Anatomical Model Uncertainty for RF Safety Evaluation of Metallic Implants Under MRI Exposure. Bioelectromagnetics 2019; 40:458-471. [PMID: 31396987 DOI: 10.1002/bem.22206] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 06/18/2019] [Indexed: 11/11/2022]
Abstract
The Virtual Population (ViP) phantoms have been used in many dosimetry studies, yet, to date, anatomical phantom uncertainty in radiofrequency (RF) research has largely been neglected. The objective of this study is to gain insight, for the first time, regarding the uncertainty in RF-induced fields during magnetic resonance imaging associated with tissue assignment and segmentation quality and consistency in anatomical phantoms by evaluating the differences between two generations of ViP phantoms, ViP1.x and ViP3.0. The RF-induced 10g-average electric (E-) fields, tangential E-fields distribution along active implantable medical devices (AIMD) routings, and estimated AIMD heating were compared for five phantoms that are part of both ViP1.x and ViP3.0. The results demonstrated that differences exceeded 3 dB (-29%, +41%) for local quantities and 1 dB (±12% for field, ±25% for power) for integrated and volume-averaged quantities (e.g., estimated AIMD-heating and 10 g-average E-fields), while the variation across different ViP phantoms of the same generation can exceed 10 dB (-68% and +217% for field, -90% and +900% for power). In conclusion, the anatomical phantom uncertainty associated with tissue assignment and segmentation quality/consistency is larger than previously assumed, i.e., 0.6 dB or ±15% (k = 1) for AIMD heating. Further, multiple phantoms based on different volunteers covering the target population are required for quantitative analysis of dosimetric endpoints, e.g., AIMD heating, which depend on patient anatomy. Phantoms with the highest fidelity in tissue assignment and segmentation should be used, as these ensure the lowest uncertainty and possible underestimation of exposure. To verify that the uncertainty decreases monotonically with improved phantom quality, the evaluation of differences between phantom generations should be repeated for any improvement in segmentation. Bioelectromagnetics. 2019;40:458-471. © 2019 Bioelectromagnetics Society.
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Affiliation(s)
- Aiping Yao
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland.,Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Earl Zastrow
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland
| | - Eugenia Cabot
- Federal Office of Communications (OFCOM), Biel, Switzerland
| | - Bryn Lloyd
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland
| | | | - Wolfgang Kainz
- Center for Devices and Radiological Health, Food and Drug Administration (FDA), Silver Spring, Maryland
| | - Niels Kuster
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland.,Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
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Thielens A, Bockstael A, Declerck S, Aminzadeh R, Aerts S, Botteldooren D, Martens L, Joseph W. Mobile phones: A trade-off between speech intelligibility and exposure to noise levels and to radio-frequency electromagnetic fields. ENVIRONMENTAL RESEARCH 2019; 175:1-10. [PMID: 31096087 DOI: 10.1016/j.envres.2019.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/05/2019] [Accepted: 05/06/2019] [Indexed: 06/09/2023]
Abstract
When making phone calls, cellphone and smartphone users are exposed to radio-frequency (RF) electromagnetic fields (EMFs) and sound pressure simultaneously. Speech intelligibility during mobile phone calls is related to the sound pressure level of speech relative to potential background sounds and also to the RF-EMF exposure, since the signal quality is correlated with the RF-EMF strength. Additionally, speech intelligibility, sound pressure level, and exposure to RF-EMFs are dependent on how the call is made (on speaker, held at the ear, or with headsets). The relationship between speech intelligibility, sound exposure, and exposure to RF-EMFs is determined in this study. To this aim, the transmitted RF-EMF power was recorded during phone calls made by 53 subjects in three different, controlled exposure scenarios: calling with the phone at the ear, calling in speaker-mode, and calling with a headset. This emitted power is directly proportional to the exposure to RF EMFs and is translated into specific absorption rate using numerical simulations. Simultaneously, sound pressure levels have been recorded and speech intelligibility has been assessed during each phone call. The results show that exposure to RF-EMFs, quantified as the specific absorption in the head, will be reduced when speaker-mode or a headset is used, in comparison to calling next to the ear. Additionally, personal exposure to sound pressure is also found to be highest in the condition where the phone is held next to the ear. On the other hand, speech perception is found to be the best when calling with a phone next to the ear in comparison to the other studied conditions, when background noise is present.
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Affiliation(s)
- Arno Thielens
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium; Berkeley Wireless Research Center, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, 2108 Allston Way, Suite 200, Berkeley, CA 94704, USA.
| | - Annelies Bockstael
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium; École d'orthophonie et d'audiologie, Université de Montréal, 7077 Av du Parc, Montréal, QC H3N1X7, Canada
| | - Sofie Declerck
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium
| | - Reza Aminzadeh
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium
| | - Sam Aerts
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium
| | - Dick Botteldooren
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium
| | - Luc Martens
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium
| | - Wout Joseph
- Department of Information Technology, Ghent University/iMinds, Technologiepark 126, Ghent B-9052, Belgium
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122
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Yao A, Zastrow E, Neufeld E, Kuster N. Efficient and Reliable Assessment of the Maximum Local Tissue Temperature Increase at the Electrodes of Medical Implants under MRI Exposure. Bioelectromagnetics 2019; 40:422-433. [DOI: 10.1002/bem.22208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 06/27/2019] [Indexed: 11/06/2022]
Affiliation(s)
- Aiping Yao
- Foundation for Research on Information Technologies in Society (IT'IS) Zurich Switzerland
- Swiss Federal Institute of Technology (ETH) Zurich Zurich Switzerland
| | - Earl Zastrow
- Foundation for Research on Information Technologies in Society (IT'IS) Zurich Switzerland
| | - Esra Neufeld
- Foundation for Research on Information Technologies in Society (IT'IS) Zurich Switzerland
| | - Niels Kuster
- Foundation for Research on Information Technologies in Society (IT'IS) Zurich Switzerland
- Swiss Federal Institute of Technology (ETH) Zurich Zurich Switzerland
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123
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Urban M, Orglmeister R. Evaluation of Electrode Setups by MRI Based Human Phantom with FEM Based Quasi-Static Solver for Bioimpedance Measurement . ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2019:3978-3982. [PMID: 31946743 DOI: 10.1109/embc.2019.8856693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Transthoracic electrical bioimpedance (TEB) measurement for acquiring of hemodynamic parameters e.g. stroke volume (SV) and cardiac output (CO) becomes commonly used. For precise and reliable measurement, a good understanding of the measurement system is needed to provide robust electrode placement, reproducible results, and large signal amplitudes. We propose an evaluation by MRI based human phantom with FEM based quasi-static solver for electrode placement in bioimpedance measurement. Placements according to Osypka, Cheetah and Bernstein et al. were simulated and compared with measurements taken from a (real) human subject. As a parameter for evaluation of signal quality, the percentage of current passing through the descending aorta from the overall injected current is measured. The placement according to Osypka results in 1.46 % of current flow through the descending aorta (Cheetah placement 1.12 %, Bernstein et al. placement 0.877 %) for the male human phantom DUKE. The simulation was compared with a real human subject (with comparable age, height, weight) by calculating the baseline impedance (Z0). The simulation seems to fit at best with Osypka placement, where the deviation between simulated baseline impedance and real human subject is 19.9 % (deviation for Cheetah 34.1 %, deviation for Bernstein 62.5 %). The simulation with MRI based human phantoms seems to be a very good basis for further investigations of current injection and bioimpedance measurement comprehension.
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124
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Jimenez H, Wang M, Zimmerman JW, Pennison MJ, Sharma S, Surratt T, Xu ZX, Brezovich I, Absher D, Myers RM, DeYoung B, Caudell DL, Chen D, Lo HW, Lin HK, Godwin DW, Olivier M, Ghanekar A, Chen K, Miller LD, Gong Y, Capstick M, D'Agostino RB, Munden R, Merle P, Barbault A, Blackstock AW, Bonkovsky HL, Yang GY, Jin G, Liu L, Zhang W, Watabe K, Blackman CF, Pasche BC. Tumour-specific amplitude-modulated radiofrequency electromagnetic fields induce differentiation of hepatocellular carcinoma via targeting Ca v3.2 T-type voltage-gated calcium channels and Ca 2+ influx. EBioMedicine 2019; 44:209-224. [PMID: 31160272 PMCID: PMC6604666 DOI: 10.1016/j.ebiom.2019.05.034] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/30/2019] [Accepted: 05/14/2019] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Administration of amplitude modulated 27·12 MHz radiofrequency electromagnetic fields (AM RF EMF) by means of a spoon-shaped applicator placed on the patient's tongue is a newly approved treatment for advanced hepatocellular carcinoma (HCC). The mechanism of action of tumour-specific AM RF EMF is largely unknown. METHODS Whole body and organ-specific human dosimetry analyses were performed. Mice carrying human HCC xenografts were exposed to AM RF EMF using a small animal AM RF EMF exposure system replicating human dosimetry and exposure time. We performed histological analysis of tumours following exposure to AM RF EMF. Using an agnostic genomic approach, we characterized the mechanism of action of AM RF EMF. FINDINGS Intrabuccal administration results in systemic delivery of athermal AM RF EMF from head to toe at levels lower than those generated by cell phones held close to the body. Tumour shrinkage results from differentiation of HCC cells into quiescent cells with spindle morphology. AM RF EMF targeted antiproliferative effects and cancer stem cell inhibiting effects are mediated by Ca2+ influx through Cav3·2 T-type voltage-gated calcium channels (CACNA1H) resulting in increased intracellular calcium concentration within HCC cells only. INTERPRETATION Intrabuccally-administered AM RF EMF is a systemic therapy that selectively block the growth of HCC cells. AM RF EMF pronounced inhibitory effects on cancer stem cells may explain the exceptionally long responses observed in several patients with advanced HCC. FUND: Research reported in this publication was supported by the National Cancer Institute's Cancer Centre Support Grant award number P30CA012197 issued to the Wake Forest Baptist Comprehensive Cancer Centre (BP) and by funds from the Charles L. Spurr Professorship Fund (BP). DWG is supported by R01 AA016852 and P50 AA026117.
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Affiliation(s)
- Hugo Jimenez
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Minghui Wang
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Jacquelyn W Zimmerman
- Department of Medicine, The Johns Hopkins School of Medicine, Baltimore, MD, United States of America; Division of Haematology/Oncology, The University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Michael J Pennison
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Sambad Sharma
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Trevor Surratt
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Zhi-Xiang Xu
- Division of Haematology/Oncology, The University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Ivan Brezovich
- Department of Radiation Oncology, The University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Devin Absher
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
| | - Richard M Myers
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States of America
| | - Barry DeYoung
- Department of Pathology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - David L Caudell
- Department of Pathology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Dongquan Chen
- Division of Preventive Medicine, The University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Hui-Wen Lo
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Hui-Kuan Lin
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Dwayne W Godwin
- Department of Neurobiology and Anatomy, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Michael Olivier
- Section of Molecular Medicine, Department of Medicine, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Anand Ghanekar
- Department of Surgery, University Health Network, Toronto, Ontario, Canada
| | - Kui Chen
- Toronto General Hospital Research Institute, Toronto, Ontario, Canada
| | - Lance D Miller
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Yijian Gong
- IT'IS Foundation, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - Myles Capstick
- IT'IS Foundation, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - Ralph B D'Agostino
- Department of Biostatistical Sciences, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Reginald Munden
- Department of Radiology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Philippe Merle
- Croix-Rousse University Hospital, Hepato-Gastroenterology and Digestive Oncology, Lyon, France
| | | | - Arthur W Blackstock
- Department of Radiation Oncology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Herbert L Bonkovsky
- Section on Gastroenterology, Department of Medicine, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Guang-Yu Yang
- Department of Pathology, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States of America
| | - Guangxu Jin
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Liang Liu
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Wei Zhang
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Kounosuke Watabe
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America
| | - Carl F Blackman
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America.
| | - Boris C Pasche
- Department of Cancer Biology, Wake Forest Baptist Medical Centre, Winston-Salem, NC, United States of America.
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125
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Clément J, Gruetter R, Ipek Ö. A combined 32-channel receive-loops/8-channel transmit-dipoles coil array for whole-brain MR imaging at 7T. Magn Reson Med 2019; 82:1229-1241. [PMID: 31081176 PMCID: PMC6618274 DOI: 10.1002/mrm.27808] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 04/17/2019] [Accepted: 04/18/2019] [Indexed: 12/24/2022]
Abstract
Purpose Multichannel receive arrays provide high SNR and parallel‐imaging capabilities, while transmit‐only dipole arrays have been shown to achieve a large coverage of the whole‐brain including the cerebellum. The aim of this study was to develop and characterize the performances of a 32‐channel receive‐only loop array combined with an 8‐channel dipole coil array at 7T for the first time. Methods The 8Tx‐dipoles/32Rx‐loops coil array was characterized by the SNR, g‐factors, noise correlation matrix, accelerated image quality, and B1+ maps, and compared with a commercial 1Tx‐birdcage/32Rx‐loops array. Simulated and measured B1+ maps were shown for the 8Tx‐dipoles/32Rx‐loops coil array and compared with the 8Tx/Rx dipole array. Results The in‐house built 32‐channel receive coil demonstrated a large longitudinal coverage of the brain, particularly the upper neck area. G‐factors and accelerated MR acquisitions demonstrated robust performances up to R = 4 in 2D, and R = 8 (4 × 2) in 3D. A 83% increase in SNR was measured over the cerebellum with the in‐house built 8Tx/32Rx coil array compared to the commercial 1Tx/32Rx, while similar performances were obtained in the cerebral cortex. Conclusions The combined 32‐channel receive/8‐channel transmit coil array demonstrated high transmit‐receive performances compared to the commercial receive array at 7T, notably in the cerebellum. We conclude that in combination with parallel transmit capabilities, this coil is particularly suitable for whole‐brain MR studies at 7T.
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Affiliation(s)
- Jérémie Clément
- LIFMET, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Rolf Gruetter
- LIFMET, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Department of Radiology, University of Geneva, Geneva, Switzerland.,Department of Radiology, University of Lausanne, Lausanne, Switzerland
| | - Özlem Ipek
- CIBM-AIT, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,School of Biomedical Engineering & Imaging, King's College London, London, United Kingdom
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126
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Shikhantsov S, Thielens A, Vermeeren G, Demeester P, Martens L, Torfs G, Joseph W. STATISTICAL APPROACH FOR HUMAN ELECTROMAGNETIC EXPOSURE ASSESSMENT IN FUTURE WIRELESS ATTO-CELL NETWORKS. RADIATION PROTECTION DOSIMETRY 2019; 183:326-331. [PMID: 30085262 PMCID: PMC6543880 DOI: 10.1093/rpd/ncy120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 05/28/2018] [Accepted: 07/23/2018] [Indexed: 06/08/2023]
Abstract
In this article, we study human electromagnetic exposure to the radiation of an ultra dense network of nodes integrated in a floor denoted as ATTO-cell floor, or ATTO-floor. ATTO-cells are a prospective 5 G wireless networking technology, in which humans are exposed by several interfering sources. To numerically estimate this exposure we propose a statistical approach based on a set of finite difference time domain simulations. It accounts for variations of antenna phases and makes use of a large number of exposure evaluations, based on a relatively low number of required simulations. The exposure was expressed in peak-spatial 10-g SAR average (psSAR10g). The results show an average exposure level of ~4.9 mW/kg and reaching 7.6 mW/kg in 5% of cases. The maximum psSAR10g value found in the studied numerical setup equals around 21.2 mW/kg. Influence of the simulated ATTO-floor size on the resulting exposure was examined. All obtained exposure levels are far below 4 W/kg ICNIRP basic restriction for general public in limbs (and 20 W/kg basic restriction for occupational exposure), which makes ATTO-floor a potential low-exposure 5 G candidate.
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Affiliation(s)
- Sergei Shikhantsov
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
| | - Arno Thielens
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
- University of California Berkeley, Department of Electrical Engineering and Computer Sciences, Berkeley Wireless Research Center, Berkeley, CA, USA
| | - Günter Vermeeren
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
| | - Piet Demeester
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
| | - Luc Martens
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
| | - Guy Torfs
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
| | - Wout Joseph
- Department of Information Technology, Ghent University/IMEC, Ghent, Belgium
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127
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Chiaramello E, Le Brusquet L, Parazzini M, Fiocchi S, Bonato M, Ravazzani P. 3D space‐dependent models for stochastic dosimetry applied to exposure to low frequency magnetic fields. Bioelectromagnetics 2019; 40:170-179. [DOI: 10.1002/bem.22179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 02/21/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Emma Chiaramello
- Istituto di Elettronica e di Ingegneria dell'Informazione e delle TelecomunicazioniCNRMilanoItaly
| | - Laurent Le Brusquet
- Laboratoire des Signaux et Systèmes (UMR CNRS 8506)Centrale Supelec, CNRS, Univ Paris‐SudUniversité Paris‐SaclayFrance
| | - Marta Parazzini
- Istituto di Elettronica e di Ingegneria dell'Informazione e delle TelecomunicazioniCNRMilanoItaly
| | - Serena Fiocchi
- Istituto di Elettronica e di Ingegneria dell'Informazione e delle TelecomunicazioniCNRMilanoItaly
| | - Marta Bonato
- Istituto di Elettronica e di Ingegneria dell'Informazione e delle TelecomunicazioniCNRMilanoItaly
- Dipartimento di ElettronicaInformazione e Bioingegneria DEIBPolitecnico di MilanoMilanoItaly
| | - Paolo Ravazzani
- Istituto di Elettronica e di Ingegneria dell'Informazione e delle TelecomunicazioniCNRMilanoItaly
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128
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Statistical Evaluation of Radiofrequency Exposure during Magnetic Resonant Imaging: Application of Whole-Body Individual Human Model and Body Motion in the Coil. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:ijerph16061069. [PMID: 30934647 PMCID: PMC6466328 DOI: 10.3390/ijerph16061069] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 03/20/2019] [Accepted: 03/21/2019] [Indexed: 11/16/2022]
Abstract
The accurate estimation of patient's exposure to the radiofrequency (RF) electromagnetic field of magnetic resonance imaging (MRI) significantly depends on a precise individual anatomical model. In the study, we investigated the applicability of an efficient whole-body individual modelling method for the assessment of MRI RF exposure. The individual modelling method included a deformable human model and tissue simplification techniques. Besides its remarkable efficiency, this approach utilized only a low specific absorption rate (SAR) sequence or even no MRI scan to generate the whole-body individual model. Therefore, it substantially reduced the risk of RF exposure. The dosimetric difference of the individual modelling method was evaluated using the manually segmented human models. In addition, stochastic dosimetry using a surrogate model by polynomial chaos presented SAR variability due to body misalignment and tilt in the coil, which were frequently occurred in the practical scan. In conclusion, the dosimetric equivalence of the individual models was validated by both deterministic and stochastic dosimetry. The proposed individual modelling method allowed the physicians to quantify the patient-specific SAR while the statistical results enabled them to comprehensively weigh over the exposure risk and get the benefit of imaging enhancement by using the high-intensity scanners or the high-SAR sequences.
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129
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Serralles JEC, Giannakopoulos II, Zhang B, Ianniello C, Cloos MA, Polimeridis AG, White JK, Sodickson DK, Daniel L, Lattanzi R. Noninvasive Estimation of Electrical Properties From Magnetic Resonance Measurements via Global Maxwell Tomography and Match Regularization. IEEE Trans Biomed Eng 2019; 67:3-15. [PMID: 30908189 DOI: 10.1109/tbme.2019.2907442] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
OBJECTIVE In this paper, we introduce global Maxwell tomography (GMT), a novel volumetric technique that estimates electric conductivity and permittivity by solving an inverse scattering problem based on magnetic resonance measurements. METHODS GMT relies on a fast volume integral equation solver, MARIE, for the forward path, and a novel regularization method, match regularization, designed specifically for electrical property estimation from noisy measurements. We performed simulations with three different tissue-mimicking numerical phantoms of different complexity, using synthetic transmit sensitivity maps with realistic noise levels as the measurements. We performed an experiment at 7 T using an eight-channel coil and a uniform phantom. RESULTS We showed that GMT could estimate relative permittivity and conductivity from noisy magnetic resonance measurements with an average error as low as 0.3% and 0.2%, respectively, over the entire volume of the numerical phantom. Voxel resolution did not affect GMT performance and is currently limited only by the memory of the graphics processing unit. In the experiment, GMT could estimate electrical properties within 5% of the values measured with a dielectric probe. CONCLUSION This work demonstrated the feasibility of GMT with match regularization, suggesting that it could be effective for accurate in vivo electrical property estimation. GMT does not rely on any symmetry assumption for the electromagnetic field, and can be generalized to estimate also the spin magnetization, at the expense of increased computational complexity. SIGNIFICANCE GMT could provide insight into the distribution of electromagnetic fields inside the body, which represents one of the key ongoing challenges for various diagnostic and therapeutic applications.
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130
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Li C, Ye Z, Wei Y, Wu T. An optimized block forward-elimination and backward-substitution algorithm for GPU accelerated ILU preconditioner in evaluating the induced electric field during transcranial magnetic stimulation. Bioelectromagnetics 2019; 40:278-284. [PMID: 30888704 DOI: 10.1002/bem.22178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 02/17/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Congsheng Li
- China Academy of Information and Communications Technology, Beijing, China
| | - Zhenfei Ye
- China Academy of Information and Communications Technology, Beijing, China
| | - Yiwen Wei
- Beijing University of Posts and Telecommunications, Beijing, China
| | - Tongning Wu
- China Academy of Information and Communications Technology, Beijing, China
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131
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Models and Indicators to Assess Thermal Sensation Under Steady-state and Transient Conditions. ENERGIES 2019. [DOI: 10.3390/en12050841] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The assessment of thermal sensation is the first stage of many studies aimed at addressing thermal comfort and at establishing the related criteria used in indoor and outdoor environments. The study of thermal sensation requires suitable modelling of the human body, taking into account the factors that affect the physiological and psychological reactions that occur under different environmental conditions. These aspects are becoming more and more relevant in the present context in which thermal sensation and thermal comfort are represented as objectives or constraints in a wider range of problems referring to the living environment. This paper first considers the models of the human body used in steady-state and transient conditions. Starting from the conceptual formulations of the heat balance equations, this paper follows the evolution occurred during the years to refine the models. This evolution is also marked by the availability of increasingly higher computational capability that enabled the researchers developing transient models with a growing level of detail and accuracy, and by the validation of the models through experimental studies that exploit advanced technologies. The paper then provides an overview of the indicators used to characterise the local and overall thermal sensation, indicating the relations with local and overall thermal comfort.
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132
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Chung BS, Jeon CY, Huh JW, Jeong KJ, Har D, Kwack KS, Park JS. Rise of the Visible Monkey: Sectioned Images of Rhesus Monkey. J Korean Med Sci 2019; 34:e66. [PMID: 30833883 PMCID: PMC6393759 DOI: 10.3346/jkms.2019.34.e66] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 01/29/2019] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Gross anatomy and sectional anatomy of a monkey should be known by students and researchers of veterinary medicine and medical research. However, materials to learn the anatomy of a monkey are scarce. Thus, the objective of this study was to produce a Visible Monkey data set containing cross sectional images, computed tomographs (CTs), and magnetic resonance images (MRIs) of a monkey whole body. METHODS Before and after sacrifice, a female rhesus monkey was used for 3 Tesla MRI and CT scanning. The monkey was frozen and sectioned at 0.05 mm intervals for the head region and at 0.5 mm intervals for the rest of the body using a cryomacrotome. Each sectioned surface was photographed using a digital camera to obtain horizontal sectioned images. Segmentation of sectioned images was performed to elaborate three-dimensional (3D) models of the skin and brain. RESULTS A total of 1,612 horizontal sectioned images of the head and 1,355 images of the remaining region were obtained. The small pixel size (0.024 mm × 0.024 mm) and real color (48 bits color) of these images enabled observations of minute structures. CONCLUSION Due to small intervals of these images, continuous structures could be traced completely. Moreover, 3D models of the skin and brain could be used for virtual dissections. Sectioned images of this study will enhance the understanding of monkey anatomy and foster further studies. These images will be provided to any requesting researcher free of charge.
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Affiliation(s)
- Beom Sun Chung
- Department of Anatomy, Ajou University School of Medicine, Suwon, Korea
| | - Chang-Yeop Jeon
- National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Korea
| | - Jae-Won Huh
- National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Korea
- Department of Functional Genomics, KRIBB School of Bioscience, Korea University of Science and Technology, Daejeon, Korea
| | - Kang-Jin Jeong
- National Primate Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju, Korea
| | - Donghwan Har
- College of ICT Engineering, Chung Ang University, Seoul, Korea
| | - Kyu-Sung Kwack
- Department of Radiology, Ajou University School of Medicine, Suwon, Korea
| | - Jin Seo Park
- Department of Anatomy, Dongguk University School of Medicine, Gyeongju, Korea
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133
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Hamnerius Y, Nilsson T, Friman E. Evaluating exposure from electric fields in a high voltage switchyard according to the EU directive. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2019; 39:150-160. [PMID: 30693868 DOI: 10.1088/1361-6498/aaf817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
An assessment according to Directive 2013/35/EU of exposure in a 400 kV switchyard has been performed. Part of the body was exposed to electric field strength above the high action level. We therefore performed simulations of the electric fields induced in the body to assess these accoding to the exposure limit values (ELVs). The simulations show that as long as the body is not grounded nor touching any grounded metallic objects, worker exposure is compliant with the directive. When grounded metallic objects are touched with hand or foot the ELV are exceeded. The ELV is exceeded already at very low contact currents (2-3 μA) in the finger. If not appropriate measures are taken, this would lead to a severe limitation of the work tasks that can be performed in switchyards.
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Affiliation(s)
- Yngve Hamnerius
- Dept. of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
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134
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Bluem P, Van de Moortele PF, Adriany G, Popović Z. Excitation and RF Field Control of a Human-Size 10.5-T MRI System. IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2019; 67:1184-1196. [PMID: 31749460 PMCID: PMC6867708 DOI: 10.1109/tmtt.2018.2884405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This paper presents an investigation of methods for improving homogeneity inside various dielectric phantoms situated in a 10.5 T human-sized MRI. The transmit B1 (B 1 + ) field is excited with a quadrature fed circular patch-probe and a 12 element capacitively-loaded microstrip array. Both simulations and measurements show improved homogeneity in a cylindrical water phantom, an inhomogeneous phantom (pineapple), and a NIST standard phantom. The simulations are performed using a full-wave finite-difference time-domain solver (Sim4Life) in order to find theB 1 + field distribution and compared to the gradient recalled echo image and efficiency result. For additional field uniformity, the wall electromagnetic boundary conditions are modified with a passive quadrifilar helix. Finally, these methods are applied in simulation to head imaging of an anatomically correct human body model (Duke, IT'IS Virtual Population) showing improved homogeneity and specific absorption rate for various excitations.
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Affiliation(s)
- Patrick Bluem
- Department of Electrical, Computer and Energy Engineering, University of Colorado, Boulder, CO 80309-0425 USA
| | | | - Gregor Adriany
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN 55455
| | - Zoya Popović
- Department of Electrical, Computer and Energy Engineering, University of Colorado, Boulder, CO 80309-0425 USA
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135
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Destruel A, Fuentes M, Weber E, O'Brien K, Jin J, Liu F, Barth M, Crozier S. A numerical and experimental study of RF shimming in the presence of hip prostheses using adaptive SAR at 3 T. Magn Reson Med 2019; 81:3826-3839. [PMID: 30803001 DOI: 10.1002/mrm.27688] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 01/17/2019] [Accepted: 01/20/2019] [Indexed: 12/25/2022]
Abstract
PURPOSE Parallel transmission techniques in MRI have the potential to improve the image quality near metal implants at 3 T. However, current testing of implants only evaluates the risk of radiofrequency (RF) heating in phantoms in circularly polarized mode. We investigate the influence of changing the transmission settings in a 2-channel body coil on the peak temperature near 2 CoCrMo hip prostheses, using adaptive specific absorption rate (SAR) as an estimate of RF heating. METHODS Adaptive SAR is a SAR averaging method that is optimized to correlate with thermal simulations and limit the temperature to 39°C near hip implants. The simulated peak temperature was compared when using whole-body SAR, SAR10g , and adaptive SAR as a constraint for the maximum allowed input power. Adaptive SAR was used as a fast estimate of temperature to evaluate the trade-off between good image quality and low heating near the hip implants. Electromagnetic simulations were validated by simulating and measuring B1 maps and electric fields in a phantom at 3 T. RESULTS Simulations and measurements showed excellent agreement. Limiting whole-body SAR to 2 W/kg and SAR10g to 10 W/kg resulted in temperatures up to 49.3°C and 40.7°C near the hip implants after 30 minutes of RF exposure, respectively. Predictions based on adaptive SAR limited the temperature to 39°C, and allowed to improve the B1 field distribution while preventing peak temperatures near the hip implants. CONCLUSION Significant RF heating can occur at 3 T near hip implants when parallel transmission is used. Adaptive SAR can be integrated in RF shimming algorithms to improve the uniformity and reduce heating.
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Affiliation(s)
- Aurelien Destruel
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia.,Centre for Advanced Imaging, University of Queensland, St. Lucia, Australia
| | - Miguel Fuentes
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia.,Population Health Research on Electromagnetic Energy, School of Public Health and Preventive Medicine, Monash University, Clayton, Australia
| | - Ewald Weber
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia
| | - Kieran O'Brien
- Centre for Advanced Imaging, University of Queensland, St. Lucia, Australia.,Siemens Healthcare, Brisbane, Australia
| | - Jin Jin
- Siemens Healthineers USA, Los Angeles, California
| | - Feng Liu
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia
| | - Markus Barth
- Centre for Advanced Imaging, University of Queensland, St. Lucia, Australia
| | - Stuart Crozier
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia
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136
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Guerin B, Iacono MI, Davids M, Dougherty D, Angelone LM, Wald LL. The 'virtual DBS population': five realistic computational models of deep brain stimulation patients for electromagnetic MR safety studies. Phys Med Biol 2019; 64:035021. [PMID: 30625451 PMCID: PMC6530797 DOI: 10.1088/1361-6560/aafce8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We design, develop, and disseminate a 'virtual population' of five realistic computational models of deep brain stimulation (DBS) patients for electromagnetic (EM) analysis. We found five DBS patients in our institution' research patient database who received high quality post-DBS surgery computer tomography (CT) examinations of the head and neck. Three patients have a single implanted pulse generator (IPG) and the two others have two IPGs (one for each lead). Moreover, one patient has two abandoned leads on each side of the head. For each patient, we combined the head and neck volumes into a 'virtual CT', from which we extracted the full-length DBS path including the IPG, extension cables, and leads. We corrected topology errors in this path, such as self-intersections, using a previously published optimization procedure. We segmented the virtual CT volume into bones, internal air, and soft tissue classes and created two-manifold, watertight surface meshes of these distributions. In addition, we added a segmented model of the brain (grey matter, white matter, eyes and cerebrospinal fluid) to one of the model (nickname Freddie) that was derived from a T1-weighted MR image obtained prior to the DBS implantation. We simulated the EM fields and specific absorption rate (SAR) induced at 3 Tesla by a quadrature birdcage body coil in each of the five patient models using a co-simulation strategy. We found that inter-subject peak SAR variability across models was independent of the target averaging mass and equal to ~45%. In our simulations of the full brain segmentation and six simplified versions of the Freddie model, the error associated with incorrect dielectric property assignment around the DBS electrodes was greater than the error associated with modeling the whole model as a single tissue class. Our DBS patient models are freely available on our lab website (Webpage of the Martinos Center Phantom Resource 2018 https://phantoms.martinos.org/Main_Page).
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Affiliation(s)
- Bastien Guerin
- Radiology, Massachusetts General Hospital, Charlestown, MA, United States of America
- Harvard Medical School, Boston, MA, United States of America
| | - Maria Ida Iacono
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, United States of America
| | - Mathias Davids
- Radiology, Massachusetts General Hospital, Charlestown, MA, United States of America
- Computer Assisted Clinical Medicine, Heidelberg University, Heidelberg, Germany
| | - Darin Dougherty
- Harvard Medical School, Boston, MA, United States of America
- Psychiatry, Massachusetts General Hospital, Charlestown, MA, United States of America
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, United States of America
| | - Lawrence L Wald
- Radiology, Massachusetts General Hospital, Charlestown, MA, United States of America
- Harvard Medical School, Boston, MA, United States of America
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137
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George Xu X. Innovations in Computer Technologies Have Impacted Radiation Dosimetry Through Anatomically Realistic Phantoms and Fast Monte Carlo Simulations. HEALTH PHYSICS 2019; 116:263-275. [PMID: 30585974 DOI: 10.1097/hp.0000000000001007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Radiological physics principles have not changed in the past 60 y when computer technologies advanced exponentially. The research field of anatomical modeling for the purpose of radiation dose calculations has experienced an explosion in activity in the past two decades. Such an exciting advancement is due to the feasibility of creating three-dimensional geometric details of the human anatomy from tomographic imaging and of performing Monte Carlo radiation transport simulations on increasingly fast and cheap personal computers. The advent of a new type of high-performance computing hardware in recent years-graphics processing units-has made it feasible to carry out time-consuming Monte Carlo calculations at near real-time speeds. This paper introduces the history of three generations of computational human phantoms (the stylized medical internal radiation dosimetry-type phantoms, the voxelized tomographic phantoms, and the boundary representation deformable phantoms) and new development of the graphics processing unit-based Monte Carlo radiation dose calculations. Examples are given for research projects performed by my students in applying computational phantoms and a new Monte Carlo code, ARCHER, to problems in radiation protection, imaging, and radiotherapy. Finally, the paper discusses challenges and future opportunities for research.
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Affiliation(s)
- X George Xu
- JEC 5049, Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180
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138
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Kainz W, Neufeld E, Bolch WE, Graff CG, Kim CH, Kuster N, Lloyd B, Morrison T, Segars P, Yeom YS, Zankl M, Xu XG, Tsui BMW. Advances in Computational Human Phantoms and Their Applications in Biomedical Engineering - A Topical Review. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2019; 3:1-23. [PMID: 30740582 PMCID: PMC6362464 DOI: 10.1109/trpms.2018.2883437] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Over the past decades, significant improvements have been made in the field of computational human phantoms (CHPs) and their applications in biomedical engineering. Their sophistication has dramatically increased. The very first CHPs were composed of simple geometric volumes, e.g., cylinders and spheres, while current CHPs have a high resolution, cover a substantial range of the patient population, have high anatomical accuracy, are poseable, morphable, and are augmented with various details to perform functionalized computations. Advances in imaging techniques and semi-automated segmentation tools allow fast and personalized development of CHPs. These advances open the door to quickly develop personalized CHPs, inherently including the disease of the patient. Because many of these CHPs are increasingly providing data for regulatory submissions of various medical devices, the validity, anatomical accuracy, and availability to cover the entire patient population is of utmost importance. The article is organized into two main sections: the first section reviews the different modeling techniques used to create CHPs, whereas the second section discusses various applications of CHPs in biomedical engineering. Each topic gives an overview, a brief history, recent developments, and an outlook into the future.
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Affiliation(s)
- Wolfgang Kainz
- Food and Drug Administration (FDA), Center for Devices and Radiological Health (CDRH), Silver Spring, MD 20993 USA
| | - Esra Neufeld
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland
| | | | - Christian G Graff
- Food and Drug Administration (FDA), Center for Devices and Radiological Health (CDRH), Silver Spring, MD 20993 USA
| | | | - Niels Kuster
- Swiss Federal Institute of Technology, ETH Zürich, and the Foundation for Research on Information Technologies in Society (IT'IS), Zürich, Switzerland
| | - Bryn Lloyd
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland
| | - Tina Morrison
- Food and Drug Administration (FDA), Center for Devices and Radiological Health (CDRH), Silver Spring, MD 20993 USA
| | | | | | - Maria Zankl
- Helmholtz Zentrum München German Research Center for Environmental Health, Munich, Germany
| | - X George Xu
- Rensselaer Polytechnic Institute, Troy, NY, USA
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139
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140
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Neufeld E, Lloyd B, Schneider B, Kainz W, Kuster N. Functionalized Anatomical Models for Computational Life Sciences. Front Physiol 2018; 9:1594. [PMID: 30505279 PMCID: PMC6250781 DOI: 10.3389/fphys.2018.01594] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 10/24/2018] [Indexed: 11/20/2022] Open
Abstract
The advent of detailed computational anatomical models has opened new avenues for computational life sciences (CLS). To date, static models representing the anatomical environment have been used in many applications but are insufficient when the dynamics of the body prevents separation of anatomical geometrical variability from physics and physiology. Obvious examples include the assessment of thermal risks in magnetic resonance imaging and planning for radiofrequency and acoustic cancer treatment, where posture and physiology-related changes in shape (e.g., breathing) or tissue behavior (e.g., thermoregulation) affect the impact. Advanced functionalized anatomical models can overcome these limitations and dramatically broaden the applicability of CLS in basic research, the development of novel devices/therapies, and the assessment of their safety and efficacy. Various forms of functionalization are discussed in this paper: (i) shape parametrization (e.g., heartbeat, population variability), (ii) physical property distributions (e.g., image-based inhomogeneity), (iii) physiological dynamics (e.g., tissue and organ behavior), and (iv) integration of simulation/measurement data (e.g., exposure conditions, “validation evidence” supporting model tuning and validation). Although current model functionalization may only represent a small part of the physiology, it already facilitates the next level of realism by (i) driving consistency among anatomy and different functionalization layers and highlighting dependencies, (ii) enabling third-party use of validated functionalization layers as established simulation tools, and (iii) therefore facilitating their application as building blocks in network or multi-scale computational models. Integration in functionalized anatomical models thus leverages and potentiates the value of sub-models and simulation/measurement data toward ever-increasing simulation realism. In our o2S2PARC platform, we propose to expand the concept of functionalized anatomical models to establish an integration and sharing service for heterogeneous computational models, ranging from the molecular to the organ level. The objective of o2S2PARC is to integrate all models developed within the National Institutes of Health SPARC initiative in a unified anatomical and computational environment, to study the role of the peripheral nervous system in controlling organ physiology. The functionalization concept, as outlined for the o2S2PARC platform, could form the basis for many other application areas of CLS. The relationship to other ongoing initiatives, such as the Physiome Project, is also presented.
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Affiliation(s)
- Esra Neufeld
- IT'IS Foundation for Research on Information Technologies in Society, Zurich, Switzerland
| | - Bryn Lloyd
- IT'IS Foundation for Research on Information Technologies in Society, Zurich, Switzerland
| | | | - Wolfgang Kainz
- Division of Biomedical Physics, OSEL, CDRH, Food and Drug Administration, Silver Spring, MD, United States
| | - Niels Kuster
- IT'IS Foundation for Research on Information Technologies in Society, Zurich, Switzerland.,Swiss Federal Institute of Technology (ETHZ), Zurich, Switzerland
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141
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Liorni I, Neufeld E, Kühn S, Murbach M, Zastrow E, Kainz W, Kuster N. Novel mechanistic model and computational approximation for electromagnetic safety evaluations of electrically short implants. Phys Med Biol 2018; 63:225015. [PMID: 30418958 DOI: 10.1088/1361-6560/aae94c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper addresses unresolved issues related to the safety of persons with conductive medical implants exposed to electromagnetic (EM) fields. When exposed to EM fields compatible with the reference limits-in particular <100 MHz-implants may enhance local fields and energy absorption to values much higher than the basic restrictions that are considered safe. A mechanistic model based on transfer functions has been postulated for elongated active implants at magnetic resonance imaging (MRI) frequencies and used as a basis for standards dealing with MRI implant safety. However, this mechanistic model is inconsistent with the behavior observed for electrically short implants, such as abandoned leads in MRI or active implants under low-frequency exposure conditions (e.g. wireless power transfer). In this paper, a new mechanistic model for electrically short implants is proposed that allows implant safety assessment to be decomposed into separate steps. Per tip-shape, it requires only a single simulation or measurement of the implant exposed under (semi-)homogeneous conditions. To validate the approach, predictions of the mechanistic model were compared to results of numerical simulations for electric- and magnetic-field exposures. The impact of parameters such as tissue properties, length, tip shape, and insulation thickness on safety- and compliance-relevant quantities was studied. Validation involving an anatomically detailed computational human body model with a realistic implant at multiple locations under electric and magnetic exposures resulted in prediction agreement on the order of 7% (maximal deviation <15%). The approach was found to be applicable for electrical lengths up to 20% of the effective wavelength and can be used to derive suitable testing procedures as well as to develop safety guidelines and standards.
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Affiliation(s)
- Ilaria Liorni
- Foundation for Research on Information Technologies in Society (IT'IS), Zeughausstrasse 43, 8004 Zurich, Switzerland. Author to whom any correspondence
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142
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Fernández C, de Salles AA, Sears ME, Morris RD, Davis DL. Absorption of wireless radiation in the child versus adult brain and eye from cell phone conversation or virtual reality. ENVIRONMENTAL RESEARCH 2018; 167:694-699. [PMID: 29884550 DOI: 10.1016/j.envres.2018.05.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 05/08/2018] [Accepted: 05/11/2018] [Indexed: 06/08/2023]
Abstract
Children's brains are more susceptible to hazardous exposures, and are thought to absorb higher doses of radiation from cell phones in some regions of the brain. Globally the numbers and applications of wireless devices are increasing rapidly, but since 1997 safety testing has relied on a large, homogenous, adult male head phantom to simulate exposures; the "Standard Anthropomorphic Mannequin" (SAM) is used to estimate only whether tissue temperature will be increased by more than 1 Celsius degree in the periphery. The present work employs anatomically based modeling currently used to set standards for surgical and medical devices, that incorporates heterogeneous characteristics of age and anatomy. Modeling of a cell phone held to the ear, or of virtual reality devices in front of the eyes, reveals that young eyes and brains absorb substantially higher local radiation doses than adults'. Age-specific simulations indicate the need to apply refined methods for regulatory compliance testing; and for public education regarding manufacturers' advice to keep phones off the body, and prudent use to limit exposures, particularly to protect the young.
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Affiliation(s)
- C Fernández
- Federal Institute of Rio Grande do Sul, IFRS, Canoas 92412-240, Brazil.
| | - A A de Salles
- Federal University of Rio Grande do Sul, UFRGS, Porto Alegre 90050-190, Brazil
| | - M E Sears
- Prevent Cancer Now, Canada; Environmental Health Trust, USA
| | | | - D L Davis
- Environmental Health Trust, USA; The Hebrew University of Jerusalem, Israel
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143
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Morrison TM, Pathmanathan P, Adwan M, Margerrison E. Advancing Regulatory Science With Computational Modeling for Medical Devices at the FDA's Office of Science and Engineering Laboratories. Front Med (Lausanne) 2018; 5:241. [PMID: 30356350 PMCID: PMC6167449 DOI: 10.3389/fmed.2018.00241] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/08/2018] [Indexed: 12/29/2022] Open
Abstract
Protecting and promoting public health is the mission of the U.S. Food and Drug Administration (FDA). FDA's Center for Devices and Radiological Health (CDRH), which regulates medical devices marketed in the U.S., envisions itself as the world's leader in medical device innovation and regulatory science-the development of new methods, standards, and approaches to assess the safety, efficacy, quality, and performance of medical devices. Traditionally, bench testing, animal studies, and clinical trials have been the main sources of evidence for getting medical devices on the market in the U.S. In recent years, however, computational modeling has become an increasingly powerful tool for evaluating medical devices, complementing bench, animal and clinical methods. Moreover, computational modeling methods are increasingly being used within software platforms, serving as clinical decision support tools, and are being embedded in medical devices. Because of its reach and huge potential, computational modeling has been identified as a priority by CDRH, and indeed by FDA's leadership. Therefore, the Office of Science and Engineering Laboratories (OSEL)-the research arm of CDRH-has committed significant resources to transforming computational modeling from a valuable scientific tool to a valuable regulatory tool, and developing mechanisms to rely more on digital evidence in place of other evidence. This article introduces the role of computational modeling for medical devices, describes OSEL's ongoing research, and overviews how evidence from computational modeling (i.e., digital evidence) has been used in regulatory submissions by industry to CDRH in recent years. It concludes by discussing the potential future role for computational modeling and digital evidence in medical devices.
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Affiliation(s)
- Tina M. Morrison
- Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States
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144
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Kalloch B, Bode J, Kozlov M, Pampel A, Hlawitschka M, Sehm B, Villringer A, Möller HE, Bazin PL. Semi-automated generation of individual computational models of the human head and torso from MR images. Magn Reson Med 2018; 81:2090-2105. [PMID: 30230021 DOI: 10.1002/mrm.27508] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 07/05/2018] [Accepted: 08/04/2018] [Indexed: 11/08/2022]
Abstract
PURPOSE Simulating the interaction of the human body with electromagnetic fields is an active field of research. Individualized models are increasingly being used, as anatomical differences affect the simulation results. We introduce a processing pipeline for creating individual surface-based models of the human head and torso for application in simulation software based on unstructured grids. The pipeline is designed for easy applicability and is publicly released on figshare. METHODS The pipeline covers image acquisition, segmentation, generation of segmentation masks, and surface mesh generation of the single, external boundary of each structure of interest. Two gradient-echo sequences are used for image acquisition. Structures of the head and body are segmented using several atlas-based approaches. They consist of bone/skull, subarachnoid cerebrospinal fluid, gray matter, white matter, spinal cord, lungs, the sinuses of the skull, and a combined class of all other structures including skin. After minor manual preparation, segmentation images are processed to segmentation masks, which are binarized images per segmented structure free of misclassified voxels and without an internal boundary. The proposed workflow is applied to 2 healthy subjects. RESULTS Individual differences of the subjects are well represented. The models are proven to be suitable for simulation of the RF electromagnetic field distribution. CONCLUSION Image segmentation, creation of segmentation masks, and surface mesh generation are highly automated. Manual interventions remain for preparing the segmentation images prior to segmentation mask generation. The generated surfaces exhibit a single boundary per structure and are suitable inputs for simulation software.
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Affiliation(s)
- Benjamin Kalloch
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Leipzig University of Applied Sciences, Leipzig, Germany
| | - Jens Bode
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Department of Engineering Physics, University of Applied Sciences Münster, Münster, Germany
| | - Mikhail Kozlov
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - André Pampel
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | | | - Bernhard Sehm
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Arno Villringer
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Harald E Möller
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Pierre-Louis Bazin
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Netherlands Institute for Neuroscience, Amsterdam, Netherlands.,Spinoza Centre for Neuroimaging, Amsterdam, Netherlands
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145
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Clément JD, Gruetter R, Ipek Ö. A human cerebral and cerebellar 8‐channel transceive RF dipole coil array at 7T. Magn Reson Med 2018; 81:1447-1458. [PMID: 30226637 DOI: 10.1002/mrm.27476] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 06/25/2017] [Accepted: 07/10/2018] [Indexed: 02/01/2023]
Abstract
PURPOSE Dipole antennas that provide high transmit field penetration with large coverage, and their use in a parallel transmit setup, may be advantageous in minimizing B 1 + -field inhomogeneities at ultra-high field, i.e 7T. We have developed and evaluated an 8-channel RF dipole coil array for imaging the entire cerebral and cerebellar regions in man. METHODS A coil array was modeled with seven dipoles: six placed covering the occipital and temporal lobes; one covering the parietal lobe; and two loops covering the frontal lobe. Center-shortened and fractionated dipoles were simulated for the array configuration and assessed with respect to B 1 + -field at maximum specific absorption rate averaged over 10 g tissue regions in human brain. The whole-brain center-shortened dipoles with frontal loops coil array was constructed and its transmit properties were assessed with respect to MR images, B 1 + -field, and homogeneity. RESULTS In simulations, the dipole arrays showed comparable performances to cover the whole-brain. However, for ease of construction, the center-shortened dipole was favored. High spatial resolution anatomical images of the human brain with the coil array demonstrated a full coverage of the cerebral cortex and cerebellum. CONCLUSIONS The 8-channel center-shortened dipoles and frontal loops coil array promises remarkable efficiency in highly challenging regions as the cerebellum, and phase-only RF shimming of whole-brain could greatly benefit ultra-high field magnetic resonance imaging of the human brain at 7T.
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Affiliation(s)
- Jérémie D. Clément
- LIFMET Ecole Polytechnique Fédérale de Lausanne (EPFL) Geneva Switzerland
| | - Rolf Gruetter
- LIFMET Ecole Polytechnique Fédérale de Lausanne (EPFL) Geneva Switzerland
- Department of Radiology University of Geneva Geneva Switzerland
- Department of Radiology University of Lausanne Lausanne Switzerland
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146
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Destruel A, O'Brien K, Jin J, Liu F, Barth M, Crozier S. Adaptive SAR mass-averaging framework to improve predictions of local RF heating near a hip implant for parallel transmit at 7 T. Magn Reson Med 2018; 81:615-627. [PMID: 30058186 DOI: 10.1002/mrm.27379] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 04/26/2018] [Accepted: 05/07/2018] [Indexed: 12/26/2022]
Abstract
PURPOSE Magnetic resonance imaging is used increasingly to scan patients with hip prostheses. We evaluated the reliability of 10 g-averaged specific absorption rate (SAR10g ) to predict radiofrequency (RF) heating in tissues surrounding a hip implant at 7 T in an 8-channel pTx hip coil. A new adaptive SAR mass-averaging method is proposed to improve the correlation between the distribution of mass-averaged SAR and that of tissue temperature. METHODS Currently, RF safety standards for implants are based on temperature instead of SAR, as SAR has not been introduced with regard to exposure scenarios with implants. In this manuscript, however, adaptive SAR is proposed for fast and reliable exposure evaluation with implants, after its correlation with tissue temperature is verified. A framework to calculate adaptive SAR mass-averaging was introduced, which uses a different averaging mass in tissues surrounding the implants and was designed to prevent the temperature from exceeding 39ºC. Predictions from SAR10g and adaptive SAR were compared with thermal simulations. RESULTS The SAR10g method failed to predict both the location and amplitude of heating in tissue near the metal implants. In some cases, the temperature far exceeded 39ºC even when SAR10g was only 70% of the maximum allowed 10 W/kg. The distributions of adaptive SAR and temperature matched in most of the configurations, and the temperature remained below 39ºC when adaptive SAR was constrained. CONCLUSION Adaptive SAR can accurately monitor RF heating and could be used for parallel transmit at 7 T to supplement current standards.
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Affiliation(s)
- Aurelien Destruel
- School of Information Technology and Electrical Engineering, University of Queensland, Australia.,Centre for Advanced Imaging, University of Queensland, Australia
| | - Kieran O'Brien
- Centre for Advanced Imaging, University of Queensland, Australia.,Siemens Healthcare Pty Ltd, Brisbane, Australia
| | - Jin Jin
- School of Information Technology and Electrical Engineering, University of Queensland, Australia.,Siemens Medical Solutions USA, Malvern, Pennsylvania.,Institute for Neuroimaging and Informatics, University of Southern California, Los Angeles, California
| | - Feng Liu
- School of Information Technology and Electrical Engineering, University of Queensland, Australia
| | - Markus Barth
- Centre for Advanced Imaging, University of Queensland, Australia
| | - Stuart Crozier
- School of Information Technology and Electrical Engineering, University of Queensland, Australia
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147
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Foerster M, Thielens A, Joseph W, Eeftens M, Röösli M. A Prospective Cohort Study of Adolescents' Memory Performance and Individual Brain Dose of Microwave Radiation from Wireless Communication. ENVIRONMENTAL HEALTH PERSPECTIVES 2018; 126:077007. [PMID: 30044230 PMCID: PMC6108834 DOI: 10.1289/ehp2427] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 05/16/2018] [Accepted: 05/23/2018] [Indexed: 05/04/2023]
Abstract
BACKGROUND The potential impact of microwave radiofrequency electromagnetic fields (RF-EMF) emitted by wireless communication devices on neurocognitive functions of adolescents is controversial. In a previous analysis, we found changes in figural memory scores associated with a higher cumulative RF-EMF brain dose in adolescents. OBJECTIVE We aimed to follow-up our previous results using a new study population, dose estimation, and approach to controlling for confounding from media usage itself. METHODS RF-EMF brain dose for each participant was modeled. Multivariable linear regression models were fitted on verbal and figural memory score changes over 1 y and on estimated cumulative brain dose and RF-EMF related and unrelated media usage (n=669-676). Because of the hemispheric lateralization of memory, we conducted a laterality analysis for phone call ear preference. To control for the confounding of media use behaviors, a stratified analysis for different media usage groups was also conducted. RESULTS We found decreased figural memory scores in association with an interquartile range (IQR) increase in estimated cumulative RF-EMF brain dose scores: -0.22 (95% CI: -0.47, 0.03; IQR: 953 mJ/kg per day) in the whole sample, -0.39 (95% CI: -0.67, -0.10; IQR: 953 mJ/kg per day) in right-side users (n=532), and -0.26 (95% CI: -0.42, -0.10; IQR: 341 mJ/kg per day) when recorded network operator data were used for RF-EMF dose estimation (n=274). Media usage unrelated to RF-EMF did not show significant associations or consistent patterns, with the exception of consistent (nonsignificant) positive associations between data traffic duration and verbal memory. CONCLUSIONS Our findings for a cohort of Swiss adolescents require confirmation in other populations but suggest a potential adverse effect of RF-EMF brain dose on cognitive functions that involve brain regions mostly exposed during mobile phone use. https://doi.org/10.1289/EHP2427.
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Affiliation(s)
- Milena Foerster
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Arno Thielens
- Department of Electrical Engineering and Computer Sciences, Berkeley Wireless Research Center, University of California Berkeley, Berkeley, California, USA
- Interuniversity Microelectronics Centre (IMEC), Leuven, Belgium
| | - Wout Joseph
- Interuniversity Microelectronics Centre (IMEC), Leuven, Belgium
- Department of Information Technology, Waves research group, Ghent University
| | - Marloes Eeftens
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Martin Röösli
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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148
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Wang H, Sun X, Wu T, Li C, Chen Z, Liao M, Li M, Yan W, Huang H, Yang J, Tan Z, Hui L, Liu Y, Pan H, Qu Y, Chen Z, Tan L, Yu L, Shi H, Huo L, Zhang Y, Tang X, Zhang S, Liu C. Deformable torso phantoms of Chinese adults for personalized anatomy modelling. J Anat 2018; 233:121-134. [PMID: 29663370 PMCID: PMC5987821 DOI: 10.1111/joa.12815] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2018] [Indexed: 11/26/2022] Open
Abstract
In recent years, there has been increasing demand for personalized anatomy modelling for medical and industrial applications, such as ergonomics device development, clinical radiological exposure simulation, biomechanics analysis, and 3D animation character design. In this study, we constructed deformable torso phantoms that can be deformed to match the personal anatomy of Chinese male and female adults. The phantoms were created based on a training set of 79 trunk computed tomography (CT) images (41 males and 38 females) from normal Chinese subjects. Major torso organs were segmented from the CT images, and the statistical shape model (SSM) approach was used to learn the inter-subject anatomical variations. To match the personal anatomy, the phantoms were registered to individual body surface scans or medical images using the active shape model method. The constructed SSM demonstrated anatomical variations in body height, fat quantity, respiratory status, organ geometry, male muscle size, and female breast size. The masses of the deformed phantom organs were consistent with Chinese population organ mass ranges. To validate the performance of personal anatomy modelling, the phantoms were registered to the body surface scan and CT images. The registration accuracy measured from 22 test CT images showed a median Dice coefficient over 0.85, a median volume recovery coefficient (RCvlm ) between 0.85 and 1.1, and a median averaged surface distance (ASD) < 1.5 mm. We hope these phantoms can serve as computational tools for personalized anatomy modelling for the research community.
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Affiliation(s)
- Hongkai Wang
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Xiaobang Sun
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
- Department of Information TechnologyUniversity of JyväskyläJyväskyläFinland
| | - Tongning Wu
- China Academy of Industry and Communications TechnologyBeijingChina
| | - Congsheng Li
- China Academy of Industry and Communications TechnologyBeijingChina
| | - Zhonghua Chen
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Meiying Liao
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Mengci Li
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Wen Yan
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Hui Huang
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Jia Yang
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Ziyu Tan
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Libo Hui
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Yue Liu
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Hang Pan
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Yue Qu
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Zhaofeng Chen
- Department of Biomedical EngineeringFaculty of Electronic Information and Electrical EngineeringDalian University of TechnologyDalianLiaoningChina
| | - Liwen Tan
- Institute of Digital MedicineThird Military Medical UniversityChongqingChina
| | - Lijuan Yu
- The Affiliated Cancer Hospital of Hainan Medical CollegeHaikouHainanChina
| | - Hongcheng Shi
- Department of Nuclear MedicineZhongshan HospitalFudan UniversityShanghaiChina
| | - Li Huo
- Department of Nuclear MedicinePeking Union Medical College HospitalBeijingChina
| | - Yanjun Zhang
- Department of Nuclear Medicinethe First Affiliated Hospital of Dalian Medical UniversityDalianLiaoningChina
| | - Xin Tang
- Trauma Department of Orthopaedicsthe First Affiliated Hospital of Dalian Medical UniversityDalianLiaoningChina
| | - Shaoxiang Zhang
- Institute of Digital MedicineThird Military Medical UniversityChongqingChina
| | - Changjian Liu
- Trauma Department of Orthopaedicsthe First Affiliated Hospital of Dalian Medical UniversityDalianLiaoningChina
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149
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Liney GP, Dong B, Weber E, Rai R, Destruel A, Garcia-Alvarez R, Manton DJ, Jelen U, Zhang K, Barton M, Keall P, Crozier S. Imaging performance of a dedicated radiation transparent RF coil on a 1.0 Tesla inline MRI-linac. ACTA ACUST UNITED AC 2018; 63:135005. [DOI: 10.1088/1361-6560/aac813] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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150
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Chiaramello E, Parazzini M, Fiocchi S, Ravazzani P, Wiart J. Stochastic Dosimetry Based on Low Rank Tensor Approximations for the Assessment of Children Exposure to WLAN Source. ACTA ACUST UNITED AC 2018. [DOI: 10.1109/jerm.2018.2825018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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