1
|
Vöröslakos M, Yaghmazadeh O, Alon L, Sodickson DK, Buzsáki G. Brain-implanted conductors amplify radiofrequency fields in rodents: Advantages and risks. Bioelectromagnetics 2024; 45:139-155. [PMID: 37876116 PMCID: PMC10947979 DOI: 10.1002/bem.22489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 07/26/2023] [Accepted: 09/30/2023] [Indexed: 10/26/2023]
Abstract
Over the past few decades, daily exposure to radiofrequency (RF) fields has been increasing due to the rapid development of wireless and medical imaging technologies. Under extreme circumstances, exposure to very strong RF energy can lead to heating of body tissue, even resulting in tissue injury. The presence of implanted devices, moreover, can amplify RF effects on surrounding tissue. Therefore, it is important to understand the interactions of RF fields with tissue in the presence of implants, in order to establish appropriate wireless safety protocols, and also to extend the benefits of medical imaging to increasing numbers of people with implanted medical devices. This study explored the neurological effects of RF exposure in rodents implanted with neuronal recording electrodes. We exposed freely moving and anesthetized rats and mice to 950 MHz RF energy while monitoring their brain activity, temperature, and behavior. We found that RF exposure could induce fast onset firing of single neurons without heat injury. In addition, brain implants enhanced the effect of RF stimulation resulting in reversible behavioral changes. Using an optical temperature measurement system, we found greater than tenfold increase in brain temperature in the vicinity of the implant. On the one hand, our results underline the importance of careful safety assessment for brain-implanted devices, but on the other hand, we also show that metal implants may be used for neurostimulation if brain temperature can be kept within safe limits.
Collapse
Affiliation(s)
- Mihály Vöröslakos
- Neuroscience Institute, Langone Medical Center, New York University, New York, NY 10016, USA
| | - Omid Yaghmazadeh
- Neuroscience Institute, Langone Medical Center, New York University, New York, NY 10016, USA
| | - Leeor Alon
- Department of Radiology, Grossman School of Medicine, New York University, New York, NY 10016, USA
| | - Daniel K. Sodickson
- Neuroscience Institute, Langone Medical Center, New York University, New York, NY 10016, USA; Department of Radiology, Grossman School of Medicine, New York University, New York, NY 10016, USA
| | - György Buzsáki
- Neuroscience Institute, Langone Medical Center, New York University, New York, NY 10016, USA; Department of Neurology, Grossman School of Medicine, New York University, New York, NY 10016, USA
| |
Collapse
|
2
|
Jacobs P, Fagan AJ. The effect of frequency (64-498 MHz) on specific absorption rate adjacent to metallic orthopedic screws in MRI: A numerical simulation study. Med Phys 2024; 51:1074-1082. [PMID: 38116822 PMCID: PMC10922637 DOI: 10.1002/mp.16902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 11/04/2023] [Accepted: 12/04/2023] [Indexed: 12/21/2023] Open
Abstract
BACKGROUND The imaging of patients with implanted electrically-conductive devices via magnetic resonance imaging at ultra-high fields is hampered by uncertainties relating to the potential for inducing tissue heating adjacent to the implant due to coupling of energy from the incident electromagnetic field into the implant. Existing data in the peer-reviewed literature of comparisons across field strengths of tissue heating and its surrogate, the specific absorption rate (SAR), is scarce and contradictory, leading to further doubts pertaining to the safety of imaging patients with such devices. PURPOSE The radiofrequency-induced SAR adjacent to orthopedic screws of varying length and at frequencies of 64 to 498 MHz was investigated via full-wave electromagnetic simulations, to provide an accurate comparison of SAR across MRI field strengths. METHODS Dipole antennas were used for RF transmission to achieve a uniform electric field tangential to the screws located 120 mm above the antenna midpoints, embedded in a bone-mimicking material. The input power to the antennas was constrained to achieve the following targets without the screw present: (i) E = 100 V/m, (ii) B1 + = 2 μT, and (iii) global-average-SAR = 3.2 W/kg. Simulations were performed with a spatial resolution of 0.2 mm in the volume surrounding the screws, resulting in 76-137 MCells, noting the maximum 1 g-averaged SAR value in each case. Simulations were repeated at 128 and 297 MHz for screws embedded in muscle tissue. RESULTS The peak SAR, occurring at the resonant screw length, substantially increased as the frequency decreased when the input power to the dipole antenna was constrained to achieve constant electric field in background tissue at the screws' locations. A similar pattern was observed when constraining input power to achieve constant B1 + and global-average-SAR. The dielectric properties of the tissue in which the screws were embedded dominated the SAR comparisons between 297 and 128 MHz. CONCLUSIONS The study design allowed for a direct comparison to be performed of SAR across frequencies and implant lengths without the confounding effect of variable incident electric field. Lower frequencies produced substantially larger SAR values for implants approaching the resonant length for the worst-case uniform incident electric field along the screws' length. The data may inform risk-benefit assessments for imaging patients with orthopedic implants at the new clinical field strength of 7 Tesla.
Collapse
Affiliation(s)
- Paul Jacobs
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Andrew J Fagan
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| |
Collapse
|
3
|
He Z, Dai J, Ho JDL, Tong HS, Wang X, Fang G, Liang L, Cheung CL, Guo Z, Chang HC, Iordachita I, Taylor RH, Poon WS, Chan DTM, Kwok KW. Interactive Multi-Stage Robotic Positioner for Intra-Operative MRI-Guided Stereotactic Neurosurgery. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2305495. [PMID: 38072667 PMCID: PMC10870025 DOI: 10.1002/advs.202305495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/30/2023] [Indexed: 02/17/2024]
Abstract
Magnetic resonance imaging (MRI) demonstrates clear advantages over other imaging modalities in neurosurgery with its ability to delineate critical neurovascular structures and cancerous tissue in high-resolution 3D anatomical roadmaps. However, its application has been limited to interventions performed based on static pre/post-operative imaging, where errors accrue from stereotactic frame setup, image registration, and brain shift. To leverage the powerful intra-operative functions of MRI, e.g., instrument tracking, monitoring of physiological changes and tissue temperature in MRI-guided bilateral stereotactic neurosurgery, a multi-stage robotic positioner is proposed. The system positions cannula/needle instruments using a lightweight (203 g) and compact (Ø97 × 81 mm) skull-mounted structure that fits within most standard imaging head coils. With optimized design in soft robotics, the system operates in two stages: i) manual coarse adjustment performed interactively by the surgeon (workspace of ±30°), ii) automatic fine adjustment with precise (<0.2° orientation error), responsive (1.4 Hz bandwidth), and high-resolution (0.058°) soft robotic positioning. Orientation locking provides sufficient transmission stiffness (4.07 N/mm) for instrument advancement. The system's clinical workflow and accuracy is validated with lab-based (<0.8 mm) and MRI-based testing on skull phantoms (<1.7 mm) and a cadaver subject (<2.2 mm). Custom-made wireless omni-directional tracking markers facilitated robot registration under MRI.
Collapse
Affiliation(s)
- Zhuoliang He
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Jing Dai
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Justin Di-Lang Ho
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Hon-Sing Tong
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Xiaomei Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
- Multi-Scale Medical Robotics Center, Hong Kong, 999077, China
| | - Ge Fang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Liyuan Liang
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong, 999077, China
- Multi-Scale Medical Robotics Center, Hong Kong, 999077, China
| | - Chim-Lee Cheung
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Ziyan Guo
- Department of Medical Physics and Biomedical Engineering, University College London, London, WC1E 6BT, UK
- Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, London, WC1E 6BT, UK
| | - Hing-Chiu Chang
- Department of Biomedical Engineering, The Chinese University of Hong Kong, Hong Kong, 999077, China
- Multi-Scale Medical Robotics Center, Hong Kong, 999077, China
| | - Iulian Iordachita
- Department of Mechanical Engineering and Laboratory for Computational Sensing and Robotics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Russell H Taylor
- Department of Computer Science and Laboratory for Computational Sensing and Robotics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Wai-Sang Poon
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, 999077, China
- Neuromedicine Center, Shenzhen Hospital, The University of Hong Kong, Shenzhen, 518053, China
| | - Danny Tat-Ming Chan
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, 999077, China
- Multi-Scale Medical Robotics Center, Hong Kong, 999077, China
| | - Ka-Wai Kwok
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, 999077, China
- Multi-Scale Medical Robotics Center, Hong Kong, 999077, China
| |
Collapse
|
4
|
Rogers T, Campbell-Washburn AE, Ramasawmy R, Yildirim DK, Bruce CG, Grant LP, Stine AM, Kolandaivelu A, Herzka DA, Ratnayaka K, Lederman RJ. Interventional cardiovascular magnetic resonance: state-of-the-art. J Cardiovasc Magn Reson 2023; 25:48. [PMID: 37574552 PMCID: PMC10424337 DOI: 10.1186/s12968-023-00956-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 07/25/2023] [Indexed: 08/15/2023] Open
Abstract
Transcatheter cardiovascular interventions increasingly rely on advanced imaging. X-ray fluoroscopy provides excellent visualization of catheters and devices, but poor visualization of anatomy. In contrast, magnetic resonance imaging (MRI) provides excellent visualization of anatomy and can generate real-time imaging with frame rates similar to X-ray fluoroscopy. Realization of MRI as a primary imaging modality for cardiovascular interventions has been slow, largely because existing guidewires, catheters and other devices create imaging artifacts and can heat dangerously. Nonetheless, numerous clinical centers have started interventional cardiovascular magnetic resonance (iCMR) programs for invasive hemodynamic studies or electrophysiology procedures to leverage the clear advantages of MRI tissue characterization, to quantify cardiac chamber function and flow, and to avoid ionizing radiation exposure. Clinical implementation of more complex cardiovascular interventions has been challenging because catheters and other tools require re-engineering for safety and conspicuity in the iCMR environment. However, recent innovations in scanner and interventional device technology, in particular availability of high performance low-field MRI scanners could be the inflection point, enabling a new generation of iCMR procedures. In this review we review these technical considerations, summarize contemporary clinical iCMR experience, and consider potential future applications.
Collapse
Affiliation(s)
- Toby Rogers
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA.
- Section of Interventional Cardiology, MedStar Washington Hospital Center, 110 Irving St NW, Suite 4B01, Washington, DC, 20011, USA.
| | - Adrienne E Campbell-Washburn
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - Rajiv Ramasawmy
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - D Korel Yildirim
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - Christopher G Bruce
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - Laurie P Grant
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - Annette M Stine
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - Aravindan Kolandaivelu
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
- Johns Hopkins Hospital, Baltimore, MD, USA
| | - Daniel A Herzka
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
| | - Kanishka Ratnayaka
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA
- Rady Children's Hospital, San Diego, CA, USA
| | - Robert J Lederman
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Building 10/Room 2C713, 9000 Rockville Pike, Bethesda, MD, 20892-1538, USA.
| |
Collapse
|
5
|
Chen X, Zheng C, Golestanirad L. Application of Machine learning to predict RF heating of cardiac leads during magnetic resonance imaging at 1.5 T and 3 T: A simulation study. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 349:107384. [PMID: 36842429 DOI: 10.1016/j.jmr.2023.107384] [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: 05/27/2022] [Revised: 01/04/2023] [Accepted: 01/20/2023] [Indexed: 06/18/2023]
Abstract
Predicting magnetic resonance imaging (MRI)-induced heating of elongated conductive implants, such as leads in cardiovascular implantable electronic devices, is essential to assessing patient safety. Phantom experiments have traditionally been used to estimate radio-frequency (RF) heating of implants, but they are time-consuming. Recently, machine learning has shown promise for fast prediction of RF heating of orthopaedic implants when the implant position within the MRI RF coil was predetermined. We explored whether deep learning could be applied to predict RF heating of conductive leads with variable positions and orientations during MRI at 1.5 T and 3 T. Models of 600 cardiac leads with clinically relevant trajectories were generated, and electromagnetic simulations were performed to calculate the maximum of the 1 g-averaged specific absorption rate (SAR) of RF energy at the tips of lead models during MRI at 1.5 T and 3 T. Neural networks were trained to predict the maximum SAR at the lead tip from the knowledge of the coordinates of points along the lead trajectory. Despite the large range of SAR values (∼230 W/kg to ∼ 3200 W/kg and ∼ 10 W/kg to ∼ 3300 W/kg), the root- mean-square error of the predicted vs ground truth SAR remained at 223 W/kg and 206 W/kg, with the R2 scores of 0.89 and 0.85 on the testing set for 1.5 T and 3 T models, respectively. The results suggest that machine learning is a promising approach for fast assessment of RF heating of lead-like implants when only the knowledge of the lead geometry and MRI RF coil features are in hand.
Collapse
Affiliation(s)
- Xinlu Chen
- Department of Electrical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Can Zheng
- Department of Electrical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - L Golestanirad
- Department of Electrical Engineering, Northwestern University, Evanston, IL, 60208, USA; Departmeng of Radiology, Northwestern University Chicago, IL 60611, USA; Departmeng of Biomedical Engineering, Northwestern University, Evanston, IL 60608, USA.
| |
Collapse
|
6
|
Radiofrequency induced heating of biodegradable orthopaedic screw implants during magnetic resonance imaging. Bioact Mater 2023; 25:86-94. [PMID: 36733929 PMCID: PMC9883197 DOI: 10.1016/j.bioactmat.2023.01.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/19/2023] [Accepted: 01/21/2023] [Indexed: 01/24/2023] Open
Abstract
Magnesium (Mg)-based implants have re-emerged in orthopaedic surgery as an alternative to permanent implants. Literature reveals little information on how the degradation of biodegradable implants may introduce safety implications for patient follow-up using medical imaging. Magnetic resonance imaging (MRI) benefits post-surgery monitoring of bone healing and implantation sites. Previous studies demonstrated radiofrequency (RF) heating of permanent implants caused by electromagnetic fields used in MRI. Our investigation is the first to report the effect of the degradation layer on RF-induced heating of biodegradable orthopaedic implants. WE43 orthopaedic compression screws underwent in vitro degradation. Imaging techniques were applied to assess the corrosion process and the material composition of the degraded screws. Temperature measurements were performed to quantify implant heating with respect to the degradation layer. For comparison, a commercial titanium implant screw was used. Strongest RF induced heating was observed for non-degraded WE43 screw samples. Implant heating had shown to decrease with the formation of the degradation layer. No statistical differences were observed for heating of the non-degraded WE43 material and the titanium equivalent. The highest risk of implant RF heating is most pronounced for Mg-based screws prior to degradation. Amendment to industry standards for MRI safety assessment is warranted to include biodegradable materials.
Collapse
|
7
|
Zaman A, Zhao S, Kron J, Abbate A, Tomdio A, Hundley WG, Jordan JH. Role of Cardiac MRI Imaging of Focal and Diffuse Inflammation and Fibrosis in Cardiomyopathy Patients Who Have Pacemakers/ICD Devices. Curr Cardiol Rep 2022; 24:1529-1536. [PMID: 35984554 PMCID: PMC10123953 DOI: 10.1007/s11886-022-01770-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/08/2022] [Indexed: 01/11/2023]
Abstract
PURPOSE OF REVIEW This focused report aims to discuss and summarize the use of conventional and emerging methods using cardiovascular magnetic resonance (CMR) imaging in cardiomyopathy patients with implanted cardiac devices to identify diffuse and focal inflammation and fibrosis. RECENT FINDINGS Many cardiomyopathy patients with diffuse and focal myocardial fibrosis have a unique need for cardiac imaging that is complicated by cardiovascular implantable electronic devices (CIEDs). CMR imaging can accurately image myocardial fibrosis and inflammation using T1 mapping and late gadolinium enhancement (LGE) imaging. CMR imaging in CIED patients, however, has been limited due to severe imaging artifacts associated with the devices. The emergence of wideband imaging variants of LGE and T1 mapping techniques can successfully reduce or eliminate CIED artifacts for the evaluation of myocardial substrate in cardiomyopathy patients. Wideband imaging variants of LGE and T1 mapping techniques provide new tools for imaging focal and diffuse fibrosis and imaging in cardiomyopathy patients with implanted cardiac devices. These emerging techniques have the potential for great impact in clinical care of such patients as well as clinical research where imaging endpoints are desired.
Collapse
Affiliation(s)
- Ananna Zaman
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Samantha Zhao
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA
| | - Jordana Kron
- Department of Internal Medicine, Pauley Heart Center, Virginia Commonwealth University, West Hospital, 8th Floor, 1200 E. Broad Street, Richmond, VA, 23298, USA
| | - Antonio Abbate
- Department of Internal Medicine, Pauley Heart Center, Virginia Commonwealth University, West Hospital, 8th Floor, 1200 E. Broad Street, Richmond, VA, 23298, USA
| | - Anna Tomdio
- Department of Internal Medicine, Pauley Heart Center, Virginia Commonwealth University, West Hospital, 8th Floor, 1200 E. Broad Street, Richmond, VA, 23298, USA
| | - W Gregory Hundley
- Department of Internal Medicine, Pauley Heart Center, Virginia Commonwealth University, West Hospital, 8th Floor, 1200 E. Broad Street, Richmond, VA, 23298, USA
| | - Jennifer H Jordan
- Department of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA, USA. .,Department of Internal Medicine, Pauley Heart Center, Virginia Commonwealth University, West Hospital, 8th Floor, 1200 E. Broad Street, Richmond, VA, 23298, USA.
| |
Collapse
|
8
|
Kilbride BF, Narsinh KH, Jordan CD, Mueller K, Moore T, Martin AJ, Wilson MW, Hetts SW. MRI-guided endovascular intervention: current methods and future potential. Expert Rev Med Devices 2022; 19:763-778. [PMID: 36373162 PMCID: PMC9869980 DOI: 10.1080/17434440.2022.2141110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 10/25/2022] [Indexed: 11/16/2022]
Abstract
INTRODUCTION Image-guided endovascular interventions, performed using the insertion and navigation of catheters through the vasculature, have been increasing in number over the years, as minimally invasive procedures continue to replace invasive surgical procedures. Such endovascular interventions are almost exclusively performed under x-ray fluoroscopy, which has the best spatial and temporal resolution of all clinical imaging modalities. Magnetic resonance imaging (MRI) offers unique advantages and could be an attractive alternative to conventional x-ray guidance, but also brings with it distinctive challenges. AREAS COVERED In this review, the benefits and limitations of MRI-guided endovascular interventions are addressed, systems and devices for guiding such interventions are summarized, and clinical applications are discussed. EXPERT OPINION MRI-guided endovascular interventions are still relatively new to the interventional radiology field, since significant technical hurdles remain to justify significant costs and demonstrate safety, design, and robustness. Clinical applications of MRI-guided interventions are promising but their full potential may not be realized until proper tools designed to function in the MRI environment are available. Translational research and further preclinical studies are needed before MRI-guided interventions will be practical in a clinical interventional setting.
Collapse
Affiliation(s)
- Bridget F. Kilbride
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Kazim H. Narsinh
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | | | | | - Teri Moore
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Alastair J. Martin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Mark W. Wilson
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Steven W. Hetts
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| |
Collapse
|
9
|
Design and evaluation of an MRI-ready, self-propelled needle for prostate interventions. PLoS One 2022; 17:e0274063. [PMID: 36070302 PMCID: PMC9451087 DOI: 10.1371/journal.pone.0274063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 08/19/2022] [Indexed: 11/19/2022] Open
Abstract
Prostate cancer diagnosis and focal laser ablation treatment both require the insertion of a needle for biopsy and optical fibre positioning. Needle insertion in soft tissues may cause tissue motion and deformation, which can, in turn, result in tissue damage and needle positioning errors. In this study, we present a prototype system making use of a wasp-inspired (bioinspired) self-propelled needle, which is able to move forward with zero external push force, thereby avoiding large tissue motion and deformation. Additionally, the actuation system solely consists of 3D printed parts and is therefore safe to use inside a magnetic resonance imaging (MRI) system. The needle consists of six parallel 0.25-mm diameter Nitinol rods driven by the actuation system. In the prototype, the self-propelled motion is achieved by advancing one needle segment while retracting the others. The advancing needle segment has to overcome a cutting and friction force while the retracting needle segments experience a friction force in the opposite direction. The needle self-propels through the tissue when the friction force of the five retracting needle segments overcomes the sum of the friction and cutting forces of the advancing needle segment. We tested the performance of the prototype in ex vivo human prostate tissue inside a preclinical MRI system in terms of the slip ratio of the needle with respect to the prostate tissue. The results showed that the needle was visible in MR images and that the needle was able to self-propel through the tissue with a slip ratio in the range of 0.78–0.95. The prototype is a step toward self-propelled needles for MRI-guided transperineal laser ablation as a method to treat prostate cancer.
Collapse
|
10
|
Kreutz-Rodrigues L, Gibreel W, Carlsen BT, Frick MA, Mardini S, Bakri K. Clinical and Radiological Safety of Retained Implantable Doppler Devices Used for Free Flap Monitoring. Plast Surg (Oakv) 2022; 30:20-24. [PMID: 35096688 PMCID: PMC8793759 DOI: 10.1177/22925503211006537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
INTRODUCTION Implantable Doppler devices are reliable adjuncts used for free flap monitoring. Occasionally, the probe/wire is not removed and remains in the soft tissues. The clinical safety of the retained probes and safety and compatibility with magnetic resonance imaging (MRI) have not been studied. We present a series of retained implantable Doppler probes examining clinic outcomes, safety and compatibility with MRI, and effect on MRI image quality. METHODS A retrospective review was conducted of patients who had an implantable Doppler device for free flap monitoring between July 2007 and August 2018. Routine post-operative imaging was reviewed for all patients to identify incidental findings of a retained probe. A subset of patients with retained implantable Doppler probes who underwent MRI was identified. Magnetic resonance images were reviewed to detect any degradation of image quality. RESULTS A total of 323 patients who had an implantable Doppler device placed were reviewed 18 (5.6%) patients were identified with a retained probe and were included in this study. Mean age was 49 years with mean follow-up of 34.4 months. One potential device-related complication occurred in 1 (5.6%) patient. A total of 32 MRI scans were performed in 8 patients with retained devices, including 6 patients who underwent a total of 21 MRIs of the surgical site. There were no complications related to the MRI scans, and we found no significant degradation of image quality. CONCLUSION Retained implantable Doppler probes were not associated with substantial adverse clinical outcomes nor affected MRI image quality of the surgical site.
Collapse
Affiliation(s)
| | - Waleed Gibreel
- Division of Plastic Surgery, Department of Surgery, Mayo Clinic, Rochester, MN, USA
| | - Brian T. Carlsen
- Division of Plastic Surgery, Department of Surgery, Mayo Clinic, Rochester, MN, USA
| | - Matthew A. Frick
- Division of Plastic Surgery, Department of Surgery, Mayo Clinic, Rochester, MN, USA
| | - Samir Mardini
- Division of Plastic Surgery, Department of Surgery, Mayo Clinic, Rochester, MN, USA
| | - Karim Bakri
- Division of Plastic Surgery, Department of Surgery, Mayo Clinic, Rochester, MN, USA,Karim Bakri, Division of Plastic and Reconstructive Surgery, Department of Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
| |
Collapse
|
11
|
Bhusal B, Bhattacharyya P, Baig T, Jones S, Martens M. Effect of inter-electrode RF coupling on heating patterns of wire-like conducting implants in MRI. Magn Reson Med 2022; 87:2933-2946. [PMID: 35092097 DOI: 10.1002/mrm.29177] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 12/16/2021] [Accepted: 01/09/2022] [Indexed: 11/05/2022]
Abstract
PURPOSE In this study, the effects of RF coupling on the magnitude and spatial patterns of RF-induced heating near multiple wire-like conducting implants (such as simultaneous electrical stimulation of stereoelectroencephalography electrodes) during MRI were assessed. METHODS Simulations and experimental measurements of RF-induced temperature increases near partially immersed wire-like conductors were performed using a phantom with a transmit/receive head coil on a 3T MRI system. The conductors consisted of either a pair of wires or a single simultaneous electrical stimulation of stereoelectroencephalography electrode with multiple contacts, and the locations and lengths of the conductors were varied to study the effect of electromagnetic coupling on RF-induced heating. RESULTS The temperature increase near a wire within the phantom was dependent not only on its own location and length, but also on the locations and lengths of the other partially immersed wires. In the configurations that were studied, the presence of a second implant could increase the heating near the tip of the conductor by as much as 95%. CONCLUSION The level of RF-induced heating during an MR scan is affected significantly by RF coupling when more than one wire-like implant is present. In some of the configurations studied, the heating was increased by the presence of a second conductor partially immersed in the phantom. Thus, RF coupling is an important factor to consider in the assessment of safety issues for MRI when multiple implants are present.
Collapse
Affiliation(s)
- Bhumi Bhusal
- Department of Radiology, Northwestern University, Chicago, Illinois, USA
| | | | - Tanvir Baig
- Department of Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Stephen Jones
- Imaging Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Michael Martens
- Department of Physics, Case Western Reserve University, Cleveland, Ohio, USA
| |
Collapse
|
12
|
Godinez F, Tomi-Tricot R, Delcey M, Williams SE, Mooiweer R, Quesson B, Razavi R, Hajnal JV, Malik SJ. Interventional cardiac MRI using an add-on parallel transmit MR system: In vivo experience in sheep. Magn Reson Med 2021; 86:3360-3372. [PMID: 34286866 DOI: 10.1002/mrm.28931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/15/2021] [Accepted: 06/28/2021] [Indexed: 12/19/2022]
Abstract
PURPOSE We present in vivo testing of a parallel transmit system intended for interventional MR-guided cardiac procedures. METHODS The parallel transmit system was connected in-line with a conventional 1.5 Tesla MRI system to transmit and receive on an 8-coil array. The system used a current sensor for real-time feedback to achieve real-time current control by determining coupling and null modes. Experiments were conducted on 4 Charmoise sheep weighing 33.9-45.0 kg with nitinol guidewires placed under X-ray fluoroscopy in the atrium or ventricle of the heart via the femoral vein. Heating tests were done in vivo and post-mortem with a high RF power imaging sequence using the coupling mode. Anatomical imaging was done using a combination of null modes optimized to produce a useable B1 field in the heart. RESULTS Anatomical imaging produced cine images of the heart comparable in quality to imaging with the quad mode (all channels with the same amplitude and phase). Maximum observed temperature increases occurred when insulation was stripped from the wire tip. These were 4.1℃ and 0.4℃ for the coupling mode and null modes, respectively for the in vivo case; increasing to 6.0℃ and 1.3℃, respectively for the ex vivo case, because cooling from blood flow is removed. Heating < 0.1℃ was observed when insulation was not stripped from guidewire tips. In all tests, the parallel transmit system managed to reduce the temperature at the guidewire tip. CONCLUSION We have demonstrated the first in vivo usage of an auxiliary parallel transmit system employing active feedback-based current control for interventional MRI with a conventional MRI scanner.
Collapse
Affiliation(s)
- Felipe Godinez
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.,Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Raphael Tomi-Tricot
- MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom
| | - Marylène Delcey
- Centre de Recherche Cardio, Thoracique de Bordeaux/IHU Liryc, INSERM U1045-University of Bordeaux, Pessac, France.,Siemens Healthcare, Saint-Denis, France
| | - Steven E Williams
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Ronald Mooiweer
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Bruno Quesson
- Centre de Recherche Cardio, Thoracique de Bordeaux/IHU Liryc, INSERM U1045-University of Bordeaux, Pessac, France
| | - Reza Razavi
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Joseph V Hajnal
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.,Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Shaihan J Malik
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.,Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| |
Collapse
|
13
|
Delcey M, Bour P, Ozenne V, Ben Hassen W, Quesson B. A fast MR-thermometry method for quantitative assessment of temperature increase near an implanted wire. PLoS One 2021; 16:e0250636. [PMID: 33983935 PMCID: PMC8118538 DOI: 10.1371/journal.pone.0250636] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 04/09/2021] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To propose a MR-thermometry method and associated data processing technique to predict the maximal RF-induced temperature increase near an implanted wire for any other MRI sequence. METHODS A dynamic single shot echo planar imaging sequence was implemented that interleaves acquisition of several slices every second and an energy deposition module with adjustable parameters. Temperature images were processed in real time and compared to invasive fiber-optic measurements to assess accuracy of the method. The standard deviation of temperature was measured in gel and in vivo in the human brain of a volunteer. Temperature increases were measured for different RF exposure levels in a phantom containing an inserted wire and then a MR-conditional pacemaker lead. These calibration data set were fitted to a semi-empirical model allowing estimation of temperature increase of other acquisition sequences. RESULTS The precision of the measurement obtained after filtering with a 1.6x1.6 mm2 in plane resolution was 0.2°C in gel, as well as in the human brain. A high correspondence was observed with invasive temperature measurements during RF-induced heating (0.5°C RMSE for a 11.5°C temperature increase). Temperature rises of 32.4°C and 6.5°C were reached at the tip of a wire and of a pacemaker lead, respectively. After successful fitting of temperature curves of the calibration data set, temperature rise predicted by the model was in good agreement (around 5% difference) with measured temperature by a fiber optic probe, for three other MRI sequences. CONCLUSION This method proposes a rapid and reliable quantification of the temperature rise near an implanted wire. Calibration data set and resulting fitting coefficients can be used to estimate temperature increase for any MRI sequence as function of its power and duration.
Collapse
Affiliation(s)
- Marylène Delcey
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac-Bordeaux, France
- Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Univ. Bordeaux, Bordeaux, France
- INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France
- Siemens Healthcare, Saint-Denis, France
- * E-mail:
| | - Pierre Bour
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac-Bordeaux, France
- Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Univ. Bordeaux, Bordeaux, France
- INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France
| | - Valéry Ozenne
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac-Bordeaux, France
- Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Univ. Bordeaux, Bordeaux, France
- INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France
| | | | - Bruno Quesson
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Pessac-Bordeaux, France
- Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Univ. Bordeaux, Bordeaux, France
- INSERM, Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France
| |
Collapse
|
14
|
Kolandaivelu A, Bruce CG, Ramasawmy R, Yildirim DK, O'Brien KJ, Schenke WH, Rogers T, Campbell-Washburn AE, Lederman RJ, Herzka DA. Native contrast visualization and tissue characterization of myocardial radiofrequency ablation and acetic acid chemoablation lesions at 0.55 T. J Cardiovasc Magn Reson 2021; 23:50. [PMID: 33952312 PMCID: PMC8101152 DOI: 10.1186/s12968-020-00693-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 12/09/2020] [Indexed: 01/18/2023] Open
Abstract
PURPOSE Low-field (0.55 T) high-performance cardiovascular magnetic resonance (CMR) is an attractive platform for CMR-guided intervention as device heating is reduced around 7.5-fold compared to 1.5 T. This work determines the feasibility of visualizing cardiac radiofrequency (RF) ablation lesions at low field CMR and explores a novel alternative method for targeted tissue destruction: acetic acid chemoablation. METHODS N = 10 swine underwent X-ray fluoroscopy-guided RF ablation (6-7 lesions) and acetic acid chemoablation (2-3 lesions) of the left ventricle. Animals were imaged at 0.55 T with native contrast 3D-navigator gated T1-weighted T1w) CMR for lesion visualization, gated single-shot imaging to determine potential for real-time visualization of lesion formation, and T1 mapping to measure change in T1 in response to ablation. Seven animals were euthanized on ablation day and hearts imaged ex vivo. The remaining animals were imaged again in vivo at 21 days post ablation to observe lesion evolution. RESULTS Chemoablation lesions could be visualized and displayed much higher contrast than necrotic RF ablation lesions with T1w imaging. On the day of ablation, in vivo myocardial T1 dropped by 19 ± 7% in RF ablation lesion cores, and by 40 ± 7% in chemoablation lesion cores (p < 4e-5). In high resolution ex vivo imaging, with reduced partial volume effects, lesion core T1 dropped by 18 ± 3% and 42 ± 6% for RF and chemoablation, respectively. Mean, median, and peak lesion signal-to-noise ratio (SNR) were all at least 75% higher with chemoablation. Lesion core to myocardium contrast-to-noise (CNR) was 3.8 × higher for chemoablation. Correlation between in vivo and ex vivo CMR and histology indicated that the periphery of RF ablation lesions do not exhibit changes in T1 while the entire extent of chemoablation exhibits T1 changes. Correlation of T1w enhancing lesion volumes indicated in vivo estimates of lesion volume are accurate for chemoablation but underestimate extent of necrosis for RF ablation. CONCLUSION The visualization of coagulation necrosis from cardiac ablation is feasible using low-field high-performance CMR. Chemoablation produced a more pronounced change in lesion T1 than RF ablation, increasing SNR and CNR and thereby making it easier to visualize in both 3D navigator-gated and real-time CMR and more suitable for low-field imaging.
Collapse
Affiliation(s)
- Aravindan Kolandaivelu
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Chris G Bruce
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Rajiv Ramasawmy
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- Biophysics and Biochemistry Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Dursun Korel Yildirim
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey
| | - Kendall J O'Brien
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - William H Schenke
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Toby Rogers
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- Medstar Washington Hospital Center, Washington, DC, USA
| | - Adrienne E Campbell-Washburn
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- Biophysics and Biochemistry Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Robert J Lederman
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Daniel A Herzka
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
| |
Collapse
|
15
|
Reiss S, Lottner T, Ozen AC, Polei S, Bitzer A, Bock M. Analysis of the RF Excitation of Endovascular Stents in Small Gap and Overlap Scenarios Using an Electro-Optical E-field Sensor. IEEE Trans Biomed Eng 2021; 68:783-792. [DOI: 10.1109/tbme.2020.3009869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
16
|
Silicon Carbide and MRI: Towards Developing a MRI Safe Neural Interface. MICROMACHINES 2021; 12:mi12020126. [PMID: 33530350 PMCID: PMC7911642 DOI: 10.3390/mi12020126] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 12/11/2022]
Abstract
An essential method to investigate neuromodulation effects of an invasive neural interface (INI) is magnetic resonance imaging (MRI). Presently, MRI imaging of patients with neural implants is highly restricted in high field MRI (e.g., 3 T and higher) due to patient safety concerns. This results in lower resolution MRI images and, consequently, degrades the efficacy of MRI imaging for diagnostic purposes in these patients. Cubic silicon carbide (3C-SiC) is a biocompatible wide-band-gap semiconductor with a high thermal conductivity and magnetic susceptibility compatible with brain tissue. It also has modifiable electrical conductivity through doping level control. These properties can improve the MRI compliance of 3C-SiC INIs, specifically in high field MRI scanning. In this work, the MRI compliance of epitaxial SiC films grown on various Si wafers, used to implement a monolithic neural implant (all-SiC), was studied. Via finite element method (FEM) and Fourier-based simulations, the specific absorption rate (SAR), induced heating, and image artifacts caused by the portion of the implant within a brain tissue phantom located in a 7 T small animal MRI machine were estimated and measured. The specific goal was to compare implant materials; thus, the effect of leads outside the tissue was not considered. The results of the simulations were validated via phantom experiments in the same 7 T MRI system. The simulation and experimental results revealed that free-standing 3C-SiC films had little to no image artifacts compared to silicon and platinum reference materials inside the MRI at 7 T. In addition, FEM simulations predicted an ~30% SAR reduction for 3C-SiC compared to Pt. These initial simulations and experiments indicate an all-SiC INI may effectively reduce MRI induced heating and image artifacts in high field MRI. In order to evaluate the MRI safety of a closed-loop, fully functional all-SiC INI as per ISO/TS 10974:2018 standard, additional research and development is being conducted and will be reported at a later date.
Collapse
|
17
|
Yaras YS, Yildirim DK, Herzka DA, Rogers T, Campbell-Washburn AE, Lederman RJ, Degertekin FL, Kocaturk O. Real-time device tracking under MRI using an acousto-optic active marker. Magn Reson Med 2020; 85:2904-2914. [PMID: 33347642 DOI: 10.1002/mrm.28625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 09/30/2020] [Accepted: 11/09/2020] [Indexed: 12/31/2022]
Abstract
PURPOSE This work aims to demonstrate the use of an "active" acousto-optic marker with enhanced visibility and reduced radiofrequency (RF) -induced heating for interventional MRI. METHODS The acousto-optic marker was fabricated using bulk piezoelectric crystal and π-phase shifted fiber Bragg grating (FBGs) and coupled to a distal receiver coil on an 8F catheter. The received MR signal is transmitted over an optical fiber to mitigate RF-induced heating. A photodetector converts the optical signal into electrical signal, which is used as the input signal to the MRI receiver plug. Acousto-optic markers were characterized in phantom studies. RF-induced heating risk was evaluated according to ASTM 2182 standard. In vivo real-time tracking capability was tested in an animal model under a 0.55T scanner. RESULTS Signal-to-noise ratio (SNR) levels suitable for real-time tracking were obtained by using high sensitivity FBG and piezoelectric transducer with resonance matched to Larmor frequency. Single and multiple marker coils integrated to 8F catheters were readout for position and orientation tracking by a single acousto-optic sensor. RF-induced heating was significantly reduced compared to a coax cable connected reference marker. Real-time distal tip tracking of an active device was demonstrated in an animal model with a standard real-time cardiac MR sequence. CONCLUSION Acousto-optic markers provide sufficient SNR with a simple structure for real-time device tracking. RF-induced heating is significantly reduced compared to conventional active markers. Also, multiple RF receiver coils connected on an acousto-optic modulator can be used on a single catheter for determining catheter orientation and shape.
Collapse
Affiliation(s)
- Yusuf S Yaras
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Micromachined Sensors and Transducers Group, Atlanta, Georgia, USA
| | - Dursun Korel Yildirim
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | - Daniel A Herzka
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | - Toby Rogers
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | | | - Robert J Lederman
- National Institutes of Health, National Heart Lung and Blood Institute, Bethesda, Maryland, USA
| | - F Levent Degertekin
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Micromachined Sensors and Transducers Group, Atlanta, Georgia, USA
| | - Ozgur Kocaturk
- Institute of Biomedical Engineering, Bogazici University, Kandilli Kampus, Istanbul, Turkey
| |
Collapse
|
18
|
MR Imaging Safety in the Interventional Environment. Magn Reson Imaging Clin N Am 2020; 28:583-591. [PMID: 33040998 DOI: 10.1016/j.mric.2020.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Interventional MR imaging procedures are rapidly growing in number owing to the excellent soft tissue resolution of MR imaging, lack of ionizing radiation, hardware and software advancements, and technical developments in MR imaging-compatible robots, lasers, and ultrasound equipment. The safe operation of an interventional MR imaging system is a complex undertaking, which is only possible with multidisciplinary planning, training, operations and oversight. Safety for both patients and operators is essential for successful operations. Herein, we review the safety concerns, solutions and challenges associated with the operation of a modern interventional MR imaging system.
Collapse
|
19
|
Bhusal B, Nguyen BT, Sanpitak PP, Vu J, Elahi B, Rosenow J, Nolt MJ, Lopez‐Rosado R, Pilitsis J, DiMarzio M, Golestanirad L. Effect of Device Configuration and Patient's Body Composition on the
RF
Heating and Nonsusceptibility Artifact of Deep Brain Stimulation Implants During
MRI
at 1.5T and 3T. J Magn Reson Imaging 2020; 53:599-610. [DOI: 10.1002/jmri.27346] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 08/12/2020] [Accepted: 08/13/2020] [Indexed: 12/13/2022] Open
Affiliation(s)
- Bhumi Bhusal
- Department of Radiology Northwestern University Chicago Illinois USA
| | - Bach T. Nguyen
- Department of Radiology Northwestern University Chicago Illinois USA
| | - Pia P. Sanpitak
- Department of Biomedical Engineering Northwestern University Chicago Illinois USA
| | - Jasmine Vu
- Department of Radiology Northwestern University Chicago Illinois USA
- Department of Biomedical Engineering Northwestern University Chicago Illinois USA
| | - Behzad Elahi
- Department of Physical Therapy and Human Movement Sciences Northwestern University Chicago Illinois USA
| | - Joshua Rosenow
- Department of Neurosurgery Northwestern University Chicago Illinois USA
| | - Mark J. Nolt
- Department of Neurosurgery Northwestern University Chicago Illinois USA
| | - Roberto Lopez‐Rosado
- Department of Physical Therapy and Human Movement Sciences Northwestern University Chicago Illinois USA
| | - Julie Pilitsis
- Department of Neurosciences and Experimental Therapeutics Albany Medical College Albany New York USA
| | - Marisa DiMarzio
- Department of Neurosciences and Experimental Therapeutics Albany Medical College Albany New York USA
| | - Laleh Golestanirad
- Department of Radiology Northwestern University Chicago Illinois USA
- Department of Biomedical Engineering Northwestern University Chicago Illinois USA
| |
Collapse
|
20
|
Reichert A, Reiss S, Krafft AJ, Bock M. Passive needle guide tracking with radial acquisition and phase-only cross-correlation. Magn Reson Med 2020; 85:1039-1046. [PMID: 32767451 DOI: 10.1002/mrm.28448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 07/07/2020] [Accepted: 07/07/2020] [Indexed: 12/24/2022]
Abstract
PURPOSE Acceleration of a passive tracking sequence based on phase-only cross-correlation (POCC) using radial undersampling. METHODS The phase-only cross-correlation (POCC) algorithm allows passive tracking of interventional instruments in real-time. In a POCC sequence, two cross-sectional images of a needle guide with a positive MR contrast are continuously acquired from which the instrument trajectory is calculated. Conventional Cartesian imaging for tracking is very time consuming; here, a higher temporal resolution is achieved using a highly undersampled radial acquisition together with a modified POCC algorithm that incorporates the point-spread-function. Targeting and needle insertion is performed in two phantom experiments with 16 fiducial targets, each using 4 and 16 radial projections for passive tracking. Additionally, targeting of eight deep lying basivertebral veins in the lumbar spines is performed for in vivo proof-of-application with four radial projections for needle guide tracking. RESULTS The radially undersampled POCC sequence yielded in the phantom experiments a lateral targeting accuracy of 1.1 ± 0.4 mm and 1.0 ± 0.5 mm for 16 and 4 radial projections, respectively, without any statistically significant difference. In the in vivo application, a mean targeting duration of 62 ± 13 s was measured. CONCLUSION Radial undersampling can drastically reduce the acquisition time for passive tracking in a POCC sequences for MR-guided needle interventions without compromising the targeting accuracy.
Collapse
Affiliation(s)
- Andreas Reichert
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Simon Reiss
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Axel Joachim Krafft
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| |
Collapse
|
21
|
Needle Heating During Interventional Magnetic Resonance Imaging at 1.5- and 3.0-T Field Strengths. Invest Radiol 2020; 55:396-404. [DOI: 10.1097/rli.0000000000000649] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
22
|
Özen AC, Silemek B, Lottner T, Atalar E, Bock M. MR safety watchdog for active catheters: Wireless impedance control with real-time feedback. Magn Reson Med 2020; 84:1048-1060. [PMID: 31961965 DOI: 10.1002/mrm.28153] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/29/2019] [Accepted: 12/09/2019] [Indexed: 12/13/2022]
Abstract
PURPOSE To dynamically minimize radiofrequency (RF)-induced heating of an active catheter through an automatic change of the termination impedance. METHODS A prototype wireless module was designed that modifies the input impedance of an active catheter to keep the temperature rise during MRI below a threshold, ΔTmax . The wireless module (MR safety watchdog; MRsWD) measures the local temperature at the catheter tip using either a built-in thermistor or external data from a fiber-optical thermometer. It automatically changes the catheter input impedance until the temperature rise during MRI is minimized. If ΔTmax is exceeded, RF transmission is blocked by a feedback system. RESULTS The thermistor and fiber-optical thermometer provided consistent temperature data in a phantom experiment. During MRI, the MRsWD was able to reduce the maximum temperature rise by 25% when operated in real-time feedback mode. CONCLUSION This study demonstrates the technical feasibility of an MRsWD as an alternative or complementary approach to reduce RF-induced heating of active interventional devices. The automatic MRsWD can reduce heating using direct temperature measurements at the tip of the catheter. Given that temperature measurements are intrinsically slow, for a clinical implementation, a faster feedback parameter would be required such as the RF currents along the catheter or scattered electric fields at the tip.
Collapse
Affiliation(s)
- Ali Caglar Özen
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany.,German Consortium for Translational Cancer Research Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Berk Silemek
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey.,Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Thomas Lottner
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Freiburg, Germany
| | - Ergin Atalar
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey.,Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Freiburg, Germany
| |
Collapse
|
23
|
Dixit N, Pauly JM, Scott GC. Thermo‐acoustic ultrasound for noninvasive temperature monitoring at lead tips during MRI. Magn Reson Med 2019; 84:1035-1047. [DOI: 10.1002/mrm.28152] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 11/14/2019] [Accepted: 12/09/2019] [Indexed: 12/29/2022]
Affiliation(s)
- Neerav Dixit
- Department of Electrical Engineering Stanford University Stanford CAUSA
| | - John M. Pauly
- Department of Electrical Engineering Stanford University Stanford CAUSA
| | - Greig C. Scott
- Department of Electrical Engineering Stanford University Stanford CAUSA
| |
Collapse
|
24
|
Godinez F, Scott G, Padormo F, Hajnal JV, Malik SJ. Safe guidewire visualization using the modes of a PTx transmit array MR system. Magn Reson Med 2019; 83:2343-2355. [PMID: 31722119 PMCID: PMC7048617 DOI: 10.1002/mrm.28069] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 10/16/2019] [Accepted: 10/16/2019] [Indexed: 02/06/2023]
Abstract
Purpose MRI‐guided cardiovascular intervention using standard metal guidewires can produce focal tissue heating caused by induced radiofrequency guidewire currents. It has been shown that safe operation is made possible by using parallel transmit radiofrequency coils driven in the null current mode, which does not induce radiofrequency currents and hence allows safe tissue visualization. We propose that the maximum current modes, usually considered unsafe, be used at very low power levels to visualize conductive wires, and we investigate pulse sequences best suited for this application. Methods Spoiled gradient echo, balanced steady‐state free precession, and turbo spin echo sequences were evaluated for their ability to visualize a conductive guidewire embedded in a gel phantom when run in maximum current modes at very low power level. Temperature at the guidewire tip was monitored for safety assessment. Results Excellent guidewire visualization could be achieved using maximum current modes excitation, with the turbo spin echo sequence giving the best image quality. Although turbo spin echo is usually considered to be a high‐power sequence, our method reduced all pulses to 1% amplitude (0.01% power), and heating was not detected. In addition, visualization of background tissue can be achieved using null current mode, also with no recorded heating at the guidewire tip even when running at 100% (reported) specific absorption rate. Conclusion Parallel transmit is a promising approach for both guidewire and tissue visualization using maximum and null current modes, respectively, for interventional cardiac MRI. Such systems can switch excitation mode instantaneously, allowing for flexible integration into interactive sequences.
Collapse
Affiliation(s)
- Felipe Godinez
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Greig Scott
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | | | - Joseph V Hajnal
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Shaihan J Malik
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| |
Collapse
|
25
|
Golestanirad L, Kazemivalipour E, Lampman D, Habara H, Atalar E, Rosenow J, Pilitsis J, Kirsch J. RF heating of deep brain stimulation implants in open-bore vertical MRI systems: A simulation study with realistic device configurations. Magn Reson Med 2019; 83:2284-2292. [PMID: 31677308 DOI: 10.1002/mrm.28049] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 10/02/2019] [Accepted: 10/03/2019] [Indexed: 12/18/2022]
Abstract
PURPOSE Patients with deep brain stimulation (DBS) implants benefit highly from MRI, however, access to MRI is restricted for these patients because of safety hazards associated with RF heating of the implant. To date, all MRI studies on RF heating of medical implants have been performed in horizontal closed-bore systems. Vertical MRI scanners have a fundamentally different distribution of electric and magnetic fields and are now available at 1.2T, capable of high-resolution structural and functional MRI. This work presents the first simulation study of RF heating of DBS implants in high-field vertical scanners. METHODS We performed finite element electromagnetic simulations to calculate specific absorption rate (SAR) at tips of DBS leads during MRI in a commercially available 1.2T vertical coil compared to a 1.5T horizontal scanner. Both isolated leads and fully implanted systems were included. RESULTS We found 10- to 30-fold reduction in SAR implication at tips of isolated DBS leads, and up to 19-fold SAR reduction at tips of leads in fully implanted systems in vertical coils compared to horizontal birdcage coils. CONCLUSIONS If confirmed in larger patient cohorts and verified experimentally, this result can open the door to plethora of structural and functional MRI applications to guide, interpret, and advance DBS therapy.
Collapse
Affiliation(s)
- Laleh Golestanirad
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, Illinois
| | - Ehsan Kazemivalipour
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.,National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | | | - Hideta Habara
- Hitachi, Ltd. Healthcare Business Unit, Tokyo, Japan
| | - Ergin Atalar
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey.,National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Joshua Rosenow
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Julie Pilitsis
- Department of Neurosurgery, Albany Medical Center, Albany, New York
| | - John Kirsch
- A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, Massachusetts
| |
Collapse
|
26
|
Alipour A, Meyer ES, Dumoulin CL, Watkins RD, Elahi H, Loew W, Schweitzer J, Olson G, Chen Y, Tao S, Guttman M, Kolandaivelu A, Halperin HR, Schmidt EJ. MRI Conditional Actively Tracked Metallic Electrophysiology Catheters and Guidewires With Miniature Tethered Radio-Frequency Traps: Theory, Design, and Validation. IEEE Trans Biomed Eng 2019; 67:1616-1627. [PMID: 31535979 DOI: 10.1109/tbme.2019.2941460] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Cardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns). METHOD MBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine. RESULTS Electromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ∼17 dB/MBalun surface-current attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility. CONCLUSION MBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI. SIGNIFICANCE MBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.
Collapse
|
27
|
Golestanirad L, Kazemivalipour E, Keil B, Downs S, Kirsch J, Elahi B, Pilitsis J, Wald LL. Reconfigurable MRI coil technology can substantially reduce RF heating of deep brain stimulation implants: First in-vitro study of RF heating reduction in bilateral DBS leads at 1.5 T. PLoS One 2019; 14:e0220043. [PMID: 31390346 PMCID: PMC6685612 DOI: 10.1371/journal.pone.0220043] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 07/08/2019] [Indexed: 12/12/2022] Open
Abstract
Patients with deep brain stimulation (DBS) implants can significantly benefit from magnetic resonance imaging (MRI), however access to MRI is restricted in these patients because of safety concerns due to RF heating of the leads. Recently we introduced a patient-adjustable reconfigurable transmit coil for low-SAR imaging of DBS at 1.5T. A previous simulation study demonstrated a substantial reduction in the local SAR around single DBS leads in 9 unilateral lead models. This work reports the first experimental results of temperature measurement at the tips of bilateral DBS leads with realistic trajectories extracted from postoperative CT images of 10 patients (20 leads in total). A total of 200 measurements were performed to record temperature rise at the tips of the leads during 2 minutes of scanning with the coil rotated to cover all accessible rotation angles. In all patients, we were able to find an optimum coil rotation angle and reduced the heating of both left and right leads to a level below the heating produced by the body coil. An average heat reduction of 65% was achieved for bilateral leads. When considering each lead alone, an average heat reduction of 80% was achieved. Our results suggest that reconfigurable coil technology introduces a promising approach for imaging of patients with DBS implants.
Collapse
Affiliation(s)
- Laleh Golestanirad
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States of America
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Ehsan Kazemivalipour
- Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
| | - Boris Keil
- Department of Life Science Engineering, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Sean Downs
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - John Kirsch
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| | - Behzad Elahi
- Department of Neurology, Bryan Health, Lincoln, NE, United States of America
| | - Julie Pilitsis
- Department of Neurosurgery, Albany Medical Center, Albany, NY, United States of America
| | - Lawrence L. Wald
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States of America
| |
Collapse
|
28
|
Erhardt JB, Lottner T, Martinez J, Özen AC, Schuettler M, Stieglitz T, Ennis DB, Bock M. It's the little things: On the complexity of planar electrode heating in MRI. Neuroimage 2019; 195:272-284. [PMID: 30935911 DOI: 10.1016/j.neuroimage.2019.03.061] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 03/07/2019] [Accepted: 03/26/2019] [Indexed: 10/27/2022] Open
Abstract
Neurological disorders are increasingly analysed and treated with implantable electrodes, and patients with such electrodes are studied with MRI despite the risk of radio-frequency (RF) induced heating during the MRI exam. Recent clinical research suggests that electrodes with smaller diameters of the electrical interface between implant and tissue are beneficial; however, the influence of this electrode contact diameter on RF-induced heating has not been investigated. In this work, electrode contact diameters between 0.3 and 4 mm of implantable electrodes appropriate for stimulation and electrocorticography were evaluated in a 1.5 T MRI system. In situ temperature measurements adapted from the ASTM standard test method were performed and complemented by simulations of the specific absorption rate (SAR) to assess local SAR values, temperature increase and the distribution of dissipated power. Measurements showed temperature changes between 0.8 K and 53 K for different electrode contact diameters, which is well above the legal limit of 1 K. Systematic errors in the temperature measurements are to be expected, as the temperature sensors may disturb the heating pattern near small electrodes. Compared to large electrodes, simulations suggest that small electrodes are subject to less dissipated power, but more localized power density. Thus, smaller electrodes might be classified as safe in current certification procedures but may be more likely to burn adjacent tissue. To assess these local heating phenomena, smaller temperature sensors or new non-invasive temperature sensing methods are needed.
Collapse
Affiliation(s)
- Johannes B Erhardt
- Department of Microsystems Engineering-IMTEK, University of Freiburg, Freiburg, Germany; Department of Radiology, University of California, Los Angeles, CA, USA; BrainLinks-BrainTools, Freiburg, Germany
| | - Thomas Lottner
- Department of Radiology - Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jessica Martinez
- Department of Radiology, University of California, Los Angeles, CA, USA; Department of Bioengineering, University of California, Los Angeles, CA, USA
| | - Ali C Özen
- Department of Radiology - Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany; German Cancer Consortium Partner Site Freiburg, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | | | - Thomas Stieglitz
- Department of Microsystems Engineering-IMTEK, University of Freiburg, Freiburg, Germany; Bernstein Center Freiburg, Freiburg, Germany; BrainLinks-BrainTools, Freiburg, Germany
| | - Daniel B Ennis
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Michael Bock
- Department of Radiology - Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
| |
Collapse
|
29
|
Reconfigurable MRI technology for low-SAR imaging of deep brain stimulation at 3T: Application in bilateral leads, fully-implanted systems, and surgically modified lead trajectories. Neuroimage 2019; 199:18-29. [PMID: 31096058 DOI: 10.1016/j.neuroimage.2019.05.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 04/24/2019] [Accepted: 05/06/2019] [Indexed: 11/22/2022] Open
Abstract
Patients with deep brain stimulation devices highly benefit from postoperative MRI exams, however MRI is not readily accessible to these patients due to safety risks associated with RF heating of the implants. Recently we introduced a patient-adjustable reconfigurable coil technology that substantially reduced local SAR at tips of single isolated DBS leads during MRI at 1.5 T in 9 realistic patient models. This contribution extends our work to higher fields by demonstrating the feasibility of scaling the technology to 3T and assessing its performance in patients with bilateral leads as well as fully implanted systems. We developed patient-derived models of bilateral DBS leads and fully implanted DBS systems from postoperative CT images of 13 patients and performed finite element simulations to calculate SAR amplification at electrode contacts during MRI with a reconfigurable rotating coil at 3T. Compared to a conventional quadrature body coil, the reconfigurable coil system reduced the SAR on average by 83% for unilateral leads and by 59% for bilateral leads. A simple surgical modification in trajectory of implanted leads was demonstrated to increase the SAR reduction efficiency of the rotating coil to >90% in a patient with a fully implanted bilateral DBS system. Thermal analysis of temperature-rise around electrode contacts during typical brain exams showed a 15-fold heating reduction using the rotating coil, generating <1°C temperature rise during ∼4-min imaging with high-SAR sequences where a conventional CP coil generated >10°C temperature rise in the tissue for the same flip angle.
Collapse
|
30
|
Golestanirad L, Angelone LM, Kirsch J, Downs S, Keil B, Bonmassar G, Wald LL. Reducing RF-induced Heating near Implanted Leads through High-Dielectric Capacitive Bleeding of Current (CBLOC). IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2019; 67:1265-1273. [PMID: 31607756 PMCID: PMC6788634 DOI: 10.1109/tmtt.2018.2885517] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Patients with implanted medical devices such as deep brain stimulation or spinal cord stimulation are often unable to receive magnetic resonance imaging (MRI). This is because once the device is within the radiofrequency (RF) field of the MRI scanner, electrically conductive leads act as antenna, amplifying the RF energy deposition in the tissue and causing possible excessive tissue heating. Here we propose a novel concept in lead design in which 40cm lead wires are coated with a ~1.2mm layer of high dielectric constant material (155 < ε r < 250) embedded in a weakly conductive insulation (σ = 20S/m). The technique called High-Dielectric Capacitive Bleeding of Current, or CBLOC, works by forming a distributed capacitance along the lengths of the lead, efficiently dissipating RF energy before it reaches the exposed tip. Measurements during RF exposure at 64 MHz and 123 MHz demonstrated that CBLOC leads generated 20-fold less heating at 1.5 T, and 40-fold less heating at 3 T compared to control leads. Numerical simulations of RF exposure at 297 MHz (7T) predicted a 15-fold reduction in specific absorption rate (SAR) of RF energy around the tip of CBLOC leads compared to control leads.
Collapse
Affiliation(s)
- Laleh Golestanirad
- A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Department of Radiology, Harvard Medical School, Charlestown, MA 02129 USA, and the Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago IL 60611 USA
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Device and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD
| | - John Kirsch
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| | - Sean Downs
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| | - Boris Keil
- Department of Life Science Engineering, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Giorgio Bonmassar
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| | - Lawrence L Wald
- A. A. Martinos Center for Biomedical Imaging, Charlestown MA 02129 USA (, , , )
| |
Collapse
|
31
|
Özen AC, Lottner T, Bock M. Safety of active catheters in MRI: Termination impedance versus RF‐induced heating. Magn Reson Med 2018; 81:1412-1423. [DOI: 10.1002/mrm.27481] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 06/08/2018] [Accepted: 07/15/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Ali Caglar Özen
- Department of Radiology, Medical Physics, Medical Center ‐ University of Freiburg, Faculty of Medicine University of Freiburg Freiburg Germany
- German Cancer Consortium Partner Site Freiburg, German Cancer Research Center (DKFZ) Heidelberg Germany
| | - Thomas Lottner
- Department of Radiology, Medical Physics, Medical Center ‐ University of Freiburg, Faculty of Medicine University of Freiburg Freiburg Germany
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center ‐ University of Freiburg, Faculty of Medicine University of Freiburg Freiburg Germany
| |
Collapse
|
32
|
Abstract
Diagnostic and interventional cardiac catheterization is routinely used in the diagnosis and treatment of congenital heart disease. There are well-established concerns regarding the risk of radiation exposure to patients and staff, particularly in children given the cumulative effects of repeat exposure. Magnetic resonance imaging (MRI) offers the advantage of being able to provide better soft tissue visualization, tissue characterization, and quantification of ventricular volumes and vascular flow. Initial work using MRI catheterization employed fusion of x-ray and MRI techniques, with x-ray fluoroscopy to guide catheter placement and subsequent MRI assessment for anatomical and hemodynamic assessment. Image overlay of 3D previously acquired MRI datasets with live fluoroscopic imaging has also been used to guide catheter procedures.Hybrid x-ray and MRI-guided catheterization paved the way for clinical application and validation of this technique in the assessment of pulmonary vascular resistance and pharmacological stress studies. Purely MRI-guided catheterization also proved possible with passive catheter tracking. First-in-man MRI-guided cardiac catheter interventions were possible due to the development of MRI-compatible guidewires, but halted due to guidewire limitations.More recent developments in passive and active catheter tracking have led to improved visualization of catheters for MRI-guided catheterization. Improvements in hardware and software have also increased image quality and scanning times with better interactive tools for the operator in the MRI catheter suite to navigate through the anatomy as required in real time. This has expanded to MRI-guided electrophysiology studies and radiofrequency ablation in humans. Animal studies show promise for the utility of MRI-guided interventional catheterization. Ongoing investment and development of MRI-compatible guidewires will pave the way for MRI-guided diagnostic and interventional catheterization coming into the mainstream.
Collapse
|
33
|
Simultaneous slice excitation for accelerated passive marker tracking via phase-only cross correlation (POCC) in MR-guided needle interventions. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2018; 31:781-788. [DOI: 10.1007/s10334-018-0701-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 08/09/2018] [Accepted: 08/15/2018] [Indexed: 12/24/2022]
|
34
|
Yaras YS, Satir S, Ozsoy C, Ramasawmy R, Campbell-Washburn AE, Lederman RJ, Kocaturk O, Degertekin FL. Acousto-Optic Catheter Tracking Sensor for Interventional MRI Procedures. IEEE Trans Biomed Eng 2018; 66:1148-1154. [PMID: 30188810 DOI: 10.1109/tbme.2018.2868830] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE The objective of this paper is to introduce an acousto-optic optical fiber sensor for tracking catheter position during interventional magnetic resonance imaging (MRI) to overcome RF induced heating of active markers. METHODS The sensor uses a miniature coil coupled to a piezoelectric transducer, which is in turn mechanically connected to an optical fiber. The piezoelectric transducer converts the RF signal to acoustic waves in the optical fiber over a region including a fiber Bragg grating (FBG). The elastic waves in the fiber modulates the FBG geometry and hence the reflected light in the optical fiber. Since the coil is much smaller than the RF wavelength and the signal is transmitted on the dielectric optical fiber, the sensor effectively reduces RF induced heating risk. Proof of concept prototypes of the sensor are implemented using commercially available piezoelectric transducers and optical fibers with FBGs. The prototypes are characterized in a 1.5 T MRI system in comparison with an active tracking marker. RESULTS Acousto-optical sensor shows linear response with flip angle and it can be used to detect signals from multiple coils for potential orientation detection. It has been successfully used to detect the position of a tacking coil in phantom in an imaging experiment. CONCLUSION Acousto-optical sensing is demonstrated for tracking catheters during interventional MRI. Real-time operation of the sensor requires sensitivity improvements like using a narrow band FBG. SIGNIFICANCE Acousto-optics provides a compact solution to sense RF signals in MRI with dielectric transmission lines.
Collapse
|
35
|
Golestanirad L, Rahsepar AA, Kirsch JE, Suwa K, Collins JC, Angelone LM, Keil B, Passman RS, Bonmassar G, Serano P, Krenz P, DeLap J, Carr JC, Wald LL. Changes in the specific absorption rate (SAR) of radiofrequency energy in patients with retained cardiac leads during MRI at 1.5T and 3T. Magn Reson Med 2018; 81:653-669. [PMID: 29893997 PMCID: PMC6258273 DOI: 10.1002/mrm.27350] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 04/08/2018] [Accepted: 04/16/2018] [Indexed: 12/20/2022]
Abstract
PURPOSE To evaluate the local specific absorption rate (SAR) and heating around retained cardiac leads during MRI at 64 MHz (1.5T) and 127 MHz (3T) as a function of RF coil type and imaging landmark. METHODS Numerical models of retained cardiac leads were built from CT and X-ray images of 6 patients with retained cardiac leads. Electromagnetic simulations and bio-heat modeling were performed with MRI RF body and head coils tuned to 64 MHz and 127 MHz and positioned at 9 different imaging landmarks covering an area from the head to the lower limbs. RESULTS For all patients and at both 1.5T and 3T, local transmit head coils produced negligible temperature rise ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>Δ</mml:mo> <mml:mi>T</mml:mi> <mml:mo><</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>°</mml:mo> <mml:mi>C</mml:mi></mml:mrow> </mml:math> ) for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>3</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> . For body imaging with quadrature-driven coils at 1.5T, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>Δ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> during a 10-min scan remained < 3°C at all imaging landmarks for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>3</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> and <6°C for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>4</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> . For body imaging at 3T, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>Δ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> during a 10-min scan remained < 6°C at all imaging landmarks for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>2</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> . For shorter pulse sequences up to 2 min, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>Δ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> remained < 6°C for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>3</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> . CONCLUSION For the models based on 6 patients studied, simulations suggest that MRI could be performed safely using a local head coil at both 1.5T and 3T, and with a body coil at 1.5T with pulses that produced <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>4</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> . MRI at 3T could be performed safely in these patients using pulses with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>2</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> .
Collapse
Affiliation(s)
- Laleh Golestanirad
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts.,Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois
| | - Amir Ali Rahsepar
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois
| | - John E Kirsch
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
| | - Kenichiro Suwa
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois
| | - Jeremy C Collins
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland
| | - Boris Keil
- Department of Life Science Engineering, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Rod S Passman
- Division of Cardiology, Department of Medicine, Northwestern University, Feinberg School of Medicine, Chicago, Illinois
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
| | - Peter Serano
- Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, Maryland
| | | | - Jim DeLap
- ANSYS Inc., Canonsburg, Pennsylvania
| | - James C Carr
- Department of Radiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois
| | - Lawrence L Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
| |
Collapse
|
36
|
Wu KJ, Gregory TS, Boland BL, Zhao W, Cheng R, Mao L, Tse ZTH. Magnetic resonance conditional paramagnetic choke for suppression of imaging artifacts during magnetic resonance imaging. Proc Inst Mech Eng H 2018; 232:597-604. [PMID: 29687748 DOI: 10.1177/0954411918771098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Higher risk patient populations require continuous physiological monitoring and, in some cases, connected life-support systems, during magnetic resonance imaging examinations. While recently there has been a shift toward wireless technology, some of the magnetic resonance imaging devices are still connected to the outside using cabling that could interfere with the magnetic resonance imaging's radio frequency during scanning, resulting in excessive heating. We developed a passive method for radio frequency suppression on cabling that may assist in making some of these devices magnetic resonance imaging compatible. A barrel-shaped strongly paramagnetic choke was developed to suppress induced radio frequency signals which are overlaid onto physiological monitoring leads during magnetic resonance imaging. It utilized a choke placed along the signal lines, with a gadolinium solution core. The choke's magnetic susceptibility was modeled, for a given geometric design, at increasing chelate concentration levels, and measured using a vibrating sample magnetometer. Radio frequency noise suppression versus frequency was quantified with network-analyzer measurements and tested using cabling placed in the magnetic resonance imaging scanner. Temperature-elevation and image-quality reduction due to the device were measured using American Society for Testing and Materials phantoms. Prototype chokes with gadolinium solution cores exhibited increasing magnetic susceptibility, and insertion loss (S21) also showed higher attenuation as gadolinium concentration increased. Image artifacts extending <4 mm from the choke were observed during magnetic resonance imaging, which agreed well with the predicted ∼3 mm artifact from the electrochemical machining simulation. An accompanying temperature increase of <1 °C was observed in the magnetic resonance imaging phantom trial. An effective paramagnetic choke for radio frequency suppression during magnetic resonance imaging was developed and its performance demonstrated.
Collapse
Affiliation(s)
- Kevin J Wu
- 1 School of Electrical and Computer Engineering, College of Engineering, University of Georgia, Athens, GA, USA
| | - T Stan Gregory
- 1 School of Electrical and Computer Engineering, College of Engineering, University of Georgia, Athens, GA, USA
| | - Brian L Boland
- 1 School of Electrical and Computer Engineering, College of Engineering, University of Georgia, Athens, GA, USA
| | - Wujun Zhao
- 2 Department of Chemistry, University of Georgia, Athens, GA, USA
| | - Rui Cheng
- 1 School of Electrical and Computer Engineering, College of Engineering, University of Georgia, Athens, GA, USA
| | - Leidong Mao
- 1 School of Electrical and Computer Engineering, College of Engineering, University of Georgia, Athens, GA, USA
| | - Zion Tsz Ho Tse
- 1 School of Electrical and Computer Engineering, College of Engineering, University of Georgia, Athens, GA, USA
| |
Collapse
|
37
|
Bhusal B, Bhattacharyya P, Baig T, Jones S, Martens M. Measurements and simulation of RF heating of implanted stereo-electroencephalography electrodes during MR scans. Magn Reson Med 2018; 80:1676-1685. [DOI: 10.1002/mrm.27144] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 01/26/2018] [Accepted: 01/31/2018] [Indexed: 12/18/2022]
Affiliation(s)
- Bhumi Bhusal
- Department of Physics; Case Western Reserve University; Cleveland Ohio USA
| | - Pallab Bhattacharyya
- Imaging Institute, Cleveland Clinic; Cleveland Ohio USA
- Radiology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University; Cleveland Ohio USA
| | - Tanvir Baig
- Department of Physics; Case Western Reserve University; Cleveland Ohio USA
| | - Stephen Jones
- Imaging Institute, Cleveland Clinic; Cleveland Ohio USA
- Epilepsy Center, Cleveland Clinic; Cleveland Ohio USA
| | - Michael Martens
- Department of Physics; Case Western Reserve University; Cleveland Ohio USA
| |
Collapse
|
38
|
Lucano E, Liberti M, Lloyd T, Apollonio F, Wedan S, Kainz W, Angelone LM. A numerical investigation on the effect of RF coil feed variability on global and local electromagnetic field exposure in human body models at 64 MHz. Magn Reson Med 2018; 79:1135-1144. [PMID: 28421683 PMCID: PMC5810925 DOI: 10.1002/mrm.26703] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 03/15/2017] [Accepted: 03/15/2017] [Indexed: 01/04/2023]
Abstract
PURPOSE This study aims to investigate how the positions of the feeding sources of the transmit radiofrequency (RF) coil, field orientation direction with respect to the patient, and patient dimensions affect the global and local electromagnetic exposure in human body models. METHODS Three RF coil models were implemented, namely a specific two-source (S2) feed and two multisource feed configurations: generic 32-source (G32) and hybrid 16-source (H16). Thirty-two feeding conditions were studied for the S2, whereas two were studied for the G32 and H16. The study was performed using five human body models. Additionally, for two of the body models, the case of a partially implanted lead was evaluated. RESULTS The results showed an overall variation due to coil feeding conditions of the whole-body specific absorption rate (SAR) of less than 20%, but deviations up to 98% of the magnitude of the electric field tangential to a possible lead path. For the analysis with the partially implanted lead, a variation of local SAR at the tip of the lead of up to 60% was observed with respect to feed position and field orientation direction. CONCLUSION The results of this study suggest that specific information about feed position and field orientation direction must be considered for an accurate evaluation of patient exposure. Magn Reson Med 79:1135-1144, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Elena Lucano
- US Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, Maryland, USA
- Universita degli Studi di Roma La Sapienza, Department of Information Engineering, Electronics, Telecommunications, Roma, Italy
| | - Micaela Liberti
- Universita degli Studi di Roma La Sapienza, Department of Information Engineering, Electronics, Telecommunications, Roma, Italy
| | - Tom Lloyd
- Imricor Medical Systems, Burnsville, Minnesota, USA
| | - Francesca Apollonio
- Universita degli Studi di Roma La Sapienza, Department of Information Engineering, Electronics, Telecommunications, Roma, Italy
| | - Steve Wedan
- Imricor Medical Systems, Burnsville, Minnesota, USA
| | - Wolfgang Kainz
- US Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, Maryland, USA
| | - Leonardo M. Angelone
- US Food and Drug Administration, Center for Devices and Radiological Health, Silver Spring, Maryland, USA
| |
Collapse
|
39
|
Dixit N, Stang PP, Pauly JM, Scott GC. Thermo-Acoustic Ultrasound for Detection of RF-Induced Device Lead Heating in MRI. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:536-546. [PMID: 29053449 PMCID: PMC5942199 DOI: 10.1109/tmi.2017.2764425] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Patients who have implanted medical devices with long conductive leads are often restricted from receiving MRI scans due to the danger of RF-induced heating near the lead tips. Phantom studies have shown that this heating varies significantly on a case-by-case basis, indicating that many patients with implanted devices can receive clinically useful MRI scans without harm. However, the difficulty of predicting RF-induced lead tip heating prior to scanning prevents numerous implant recipients from being scanned. Here, we demonstrate that thermo-acoustic ultrasound (TAUS) has the potential to be utilized for a pre-scan procedure assessing the risk of RF-induced lead tip heating in MRI. A system was developed to detect TAUS signals by four different TAUS acquisition methods. We then integrated this system with an MRI scanner and detected a peak in RF power absorption near the tip of a model lead when transmitting from the scanner's body coil. We also developed and experimentally validated simulations to characterize the thermo-acoustic signal generated near lead tips. These results indicate that TAUS is a promising method for assessing RF implant safety, and with further development, a TAUS pre-scan could allow many more patients to have access to MRI scans of significant clinical value.
Collapse
|
40
|
Alipour A, Gokyar S, Algin O, Atalar E, Demir HV. An inductively coupled ultra-thin, flexible, and passive RF resonator for MRI marking and guiding purposes: Clinical feasibility. Magn Reson Med 2017; 80:361-370. [PMID: 29148092 DOI: 10.1002/mrm.26996] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 09/17/2017] [Accepted: 10/15/2017] [Indexed: 12/20/2022]
Abstract
PURPOSE The purpose of this study is to develop a wireless, flexible, ultra-thin, and passive radiofrequency-based MRI resonant fiducial marker, and to validate its feasibility in a phantom model and several body regions. METHODS Standard microfabrication processing was used to fabricate the resonant marker. The proposed marker consists of two metal traces in the shape of a square with an edge length of 8 mm, with upper and lower traces connected to each other by a metalized via. A 3T MRI fiducial marking procedure was tested in phantom and ex vivo, and then the marker's performance was evaluated in an MRI experiment using humans. The radiofrequency safety was also tested using temperature sensors in the proximity of the resonator. RESULTS A flexible resonator with a thickness of 115 μm and a dimension of 8 × 8 mm was obtained. The experimental results in the phantom show that at low background flip angles (6-18°), the resonant marker enables precise and rapid visibility, with high marker-to-background contrast and signal-to-noise ratio improvement of greater than 10 in the vicinity of the marker. Temperature analysis showed a specific absorption ratio gain of 1.3. Clinical studies further showed a successful biopsy procedure using the fiducial marking functionality of our device. CONCLUSIONS The ultra-thin and flexible structure of this wireless flexible radiofrequency resonant marker offers effective and safe MR visualization with high feasibility for anatomic marking and guiding at various regions of the body. Magn Reson Med 80:361-370, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Akbar Alipour
- Department of Electrical and Electronics Engineering, National Magnetic Resonance Research Center (UMRAM) National Nanotechnology Research Center and Institute of Material Science and Nanotechnology (UNAM) Department of Physics, Bilkent University, Bilkent, Ankara, Turkey
| | - Sayim Gokyar
- Department of Electrical and Electronics Engineering, National Magnetic Resonance Research Center (UMRAM) National Nanotechnology Research Center and Institute of Material Science and Nanotechnology (UNAM) Department of Physics, Bilkent University, Bilkent, Ankara, Turkey
| | - Oktay Algin
- Department of Electrical and Electronics Engineering, National Magnetic Resonance Research Center (UMRAM) National Nanotechnology Research Center and Institute of Material Science and Nanotechnology (UNAM) Department of Physics, Bilkent University, Bilkent, Ankara, Turkey.,Department of Radiology, Ankara Ataturk Training and Research Hospital, Ankara, Turkey
| | - Ergin Atalar
- Department of Electrical and Electronics Engineering, National Magnetic Resonance Research Center (UMRAM) National Nanotechnology Research Center and Institute of Material Science and Nanotechnology (UNAM) Department of Physics, Bilkent University, Bilkent, Ankara, Turkey
| | - Hilmi Volkan Demir
- Department of Electrical and Electronics Engineering, National Magnetic Resonance Research Center (UMRAM) National Nanotechnology Research Center and Institute of Material Science and Nanotechnology (UNAM) Department of Physics, Bilkent University, Bilkent, Ankara, Turkey.,LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Mathematical and Physical Sciences, Nanyang Technological University, Singapore
| |
Collapse
|
41
|
Griffin GH, Anderson KJT, Wright GA. Miniaturizing Floating Traps to Increase RF Safety of Magnetic-Resonance-Guided Percutaneous Procedures. IEEE Trans Biomed Eng 2017; 64:329-340. [PMID: 28113187 DOI: 10.1109/tbme.2016.2553680] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE MRI in the area of cardiovascular catheter-based interventional procedures is an active field. A common intervention-revascularization of chronic total occlusions, requires a conductive guidewire for revascularization. The mechanical properties of guidewires are paramount to the successful execution of such procedures. Furthermore to benefit from MRI techniques, additional conductors are required to transmit signal from the tip of a catheter. Long thin conductors in MRI systems pose a safety risk in the form of RF heating due to induced RF currents on the conductors. Unfortunately many existing techniques to mitigate this risk require physical modification of the conductors, inevitably resulting in detrimental mechanical tradeoffs in the guidewire. This manuscript proposes a novel application and miniaturization of an existing device, the floating RF trap. The RF trap couples strongly to any thin conductor passing through the trap lumen inducing significant series impedance. This results in reduction of induced RF currents, and thus, heating. METHODS AND RESULTS This study shows theoretical and experimental analysis of induced impedance as well as theoretical reduction in heating due to various distributions of traps along the length of a catheter. Results of measuring induced current and heating in phantom experiments are also presented. Through comparison with commercial simulation packages and results of phantom experiments, it is shown that miniaturized RF traps can be modeled accurately, including their induced series impedance and effect on induced RF current. CONCLUSION AND SIGNIFICANCE It was demonstrated that floating RF traps present a feasible method to mitigate RF heating while maintaining important mechanical properties of guidewires.
Collapse
|
42
|
Schleicher KE, Bock M, Düring K, Kroboth S, Krafft AJ. Radial MRI with variable echo times: reducing the orientation dependency of susceptibility artifacts of an MR-safe guidewire. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2017; 31:235-242. [PMID: 28770356 DOI: 10.1007/s10334-017-0645-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Guidewires are indispensable tools for intravascular MR-guided interventions. Recently, an MR-safe guidewire made from a glass-fiber/epoxy compound material with embedded iron particles was developed. The size of the induced susceptibility artifact, and thus the guidewire's visibility, depends on its orientation against B 0. We present a radial acquisition scheme with variable echo times that aims to reduce the artifact's orientation dependency. MATERIALS AND METHODS The radial acquisition scheme uses sine-squared modulated echo times depending on the physical direction of the spoke to balance the susceptibility artifact of the guidewire. The acquisition scheme was studied in simulations based on dipole fields and in phantom experiments for different orientations of the guidewire against B 0. The simulated and measured artifact widths were quantitatively compared. RESULTS Compared to acquisitions with non-variable echo times, the proposed acquisition scheme shows a reduced angular variability. For the two main orientations (i.e., parallel and perpendicular to B 0), the ratio of the artifact widths was reduced from about 2.2 (perpendicular vs. parallel) to about 1.2 with the variable echo time approach. CONCLUSION The reduction of the orientation dependency of the guidewire's artifact via sine-squared varying echo times could be verified in simulations and measurements. The more balanced artifact allows for a better overall visibility of the guidewire.
Collapse
Affiliation(s)
- Katharina E Schleicher
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany.
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| | | | - Stefan Kroboth
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| |
Collapse
|
43
|
Korutz AW, Obajuluwa A, Lester MS, McComb EN, Hijaz TA, Collins JD, Dandamudi S, Knight BP, Nemeth AJ. Pacemakers in MRI for the Neuroradiologist. AJNR Am J Neuroradiol 2017; 38:2222-2230. [PMID: 28705821 DOI: 10.3174/ajnr.a5314] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cardiac implantable electronic devices are frequently encountered in clinical practice in patients being screened for MR imaging examinations. Traditionally, the presence of these devices has been considered a contraindication to undergoing MR imaging. Growing evidence suggests that most of these patients can safely undergo an MR imaging examination if certain conditions are met. This document will review the relevant cardiac implantable electronic devices encountered in practice today, the background physics/technical factors related to scanning these devices, the multidisciplinary screening protocol used at our institution for scanning patients with implantable cardiac devices, and our experience in safely performing these examinations since 2010.
Collapse
Affiliation(s)
- A W Korutz
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.)
| | - A Obajuluwa
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.)
| | - M S Lester
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.)
| | - E N McComb
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.)
| | - T A Hijaz
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.)
| | - J D Collins
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.)
| | - S Dandamudi
- Medicine, Division of Cardiology (S.D., B.P.K.)
| | - B P Knight
- Medicine, Division of Cardiology (S.D., B.P.K.)
| | - A J Nemeth
- From the Departments of Radiology (A.W.K., A.O., M.S.L., E.N.M., T.A.H., J.D.C., A.J.N.).,Neurology (A.J.N.), Northwestern University Feinberg School of Medicine, Chicago, Illinois
| |
Collapse
|
44
|
|
45
|
Panych LP, Madore B. The physics of MRI safety. J Magn Reson Imaging 2017; 47:28-43. [DOI: 10.1002/jmri.25761] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 04/24/2017] [Indexed: 01/25/2023] Open
Affiliation(s)
- Lawrence P. Panych
- Department of Radiology; Brigham and Women's Hospital; Boston Massachusetts USA
- Harvard Medical School; Boston Massachusetts USA
| | - Bruno Madore
- Department of Radiology; Brigham and Women's Hospital; Boston Massachusetts USA
- Harvard Medical School; Boston Massachusetts USA
| |
Collapse
|
46
|
McElcheran CE, Yang B, Anderson KJ, Golestanirad L, Graham SJ. Parallel radiofrequency transmission at 3 tesla to improve safety in bilateral implanted wires in a heterogeneous model. Magn Reson Med 2017; 78:2406-2415. [DOI: 10.1002/mrm.26622] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Revised: 01/05/2017] [Accepted: 01/06/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Clare E. McElcheran
- Physical Sciences Platform, Sunnybrook Health Sciences Institute; Toronto Canada
- Department of Medical Biophysics; University of Toronto; Toronto Canada
| | - Benson Yang
- Physical Sciences Platform, Sunnybrook Health Sciences Institute; Toronto Canada
| | - Kevan J.T. Anderson
- Physical Sciences Platform, Sunnybrook Health Sciences Institute; Toronto Canada
| | - Laleh Golestanirad
- Massachusetts General Hospital, Harvard Medical School; Charlestown Massachusetts USA
| | - Simon J. Graham
- Physical Sciences Platform, Sunnybrook Health Sciences Institute; Toronto Canada
- Department of Medical Biophysics; University of Toronto; Toronto Canada
| |
Collapse
|
47
|
Nazarian S. Cardiac Electrophysiology Procedures, Known Unknowns, and Unknown Unknowns. JACC Clin Electrophysiol 2017; 3:104-106. [DOI: 10.1016/j.jacep.2016.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 09/15/2016] [Indexed: 11/28/2022]
|
48
|
Nagy Z, Oliver-Taylor A, Kuehne A, Goluch S, Weiskopf N. Tx/Rx Head Coil Induces Less RF Transmit-Related Heating than Body Coil in Conductive Metallic Objects Outside the Active Area of the Head Coil. Front Neurosci 2017; 11:15. [PMID: 28184184 PMCID: PMC5266708 DOI: 10.3389/fnins.2017.00015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 01/09/2017] [Indexed: 11/25/2022] Open
Abstract
The transmit-receive (Tx/Rx) birdcage head coil is often used for excitation instead of the body coil because of the presumably lower risk of heating in and around conductive implants. However, this common practice has not been systematically tested. To investigate whether the Tx/Rx birdcage head coil produces less heating than the body coil when scanning individuals with implants, we used a 3T clinical scanner and made temperature measurements around a straight 15 cm conductor using either the Tx/Rx body or the head coil for excitation. Additionally, the transmitted fields of a Tx/Rx head coil were measured both in air and in gel using a resonant and a non-resonant B field probes as well as a non-resonant E field probe. Simulations using a finite-difference time domain solver were compared with the experimental findings. When the body coil was used for excitation, we observed heating around the 15 cm wire at various anatomical locations (both within and outside of the active volume of the head coil). Outside its active area, no such heating was observed while using the Tx/Rx head coil for excitation. The E and B fields of the Tx/Rx birdcage head coil extended well-beyond the physical dimensions of the coil. In air, the fields were monotonically decreasing, while in gel they were more complex with local maxima at the end of the ASTM phantom. These experimental findings were line with the simulations. While caution must always be exercised when scanning individuals with metallic implants, these findings support the use of the Tx/Rx birdcage head coil in place of the body coil at 3T in order to reduce the risk of heating in and around conductive implants that are remote from the head coil.
Collapse
Affiliation(s)
- Zoltan Nagy
- Laboratory for Social and Neural Systems Research, University of ZürichZürich, Switzerland
- Wellcome Trust Centre for Neuroimaging, University College LondonLondon, UK
| | - Aaron Oliver-Taylor
- Department of Neonatology, Institute for Women's Health, University College LondonLondon, UK
| | - Andre Kuehne
- Center for Medical Physics and Biomedical Engineering, Medical University of ViennaVienna, Austria
- MR Center of Excellence, Medical University of ViennaVienna, Austria
| | - Sigrun Goluch
- Center for Medical Physics and Biomedical Engineering, Medical University of ViennaVienna, Austria
- MR Center of Excellence, Medical University of ViennaVienna, Austria
| | - Nikolaus Weiskopf
- Wellcome Trust Centre for Neuroimaging, University College LondonLondon, UK
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain SciencesLeipzig, Germany
| |
Collapse
|
49
|
Balasubramanian M, Wells WM, Ives JR, Britz P, Mulkern RV, Orbach DB. RF Heating of Gold Cup and Conductive Plastic Electrodes during Simultaneous EEG and MRI. Neurodiagn J 2017; 57:69-83. [PMID: 28436813 PMCID: PMC5444667 DOI: 10.1080/21646821.2017.1256722] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
PURPOSE To investigate the heating of EEG electrodes during magnetic resonance imaging (MRI) scans and to better understand the underlying physical mechanisms with a focus on the antenna effect. MATERIALS AND METHODS Gold cup and conductive plastic electrodes were placed on small watermelons with fiberoptic probes used to measure electrode temperature changes during a variety of 1.5T and 3T MRI scans. A subset of these experiments was repeated on a healthy human volunteer. RESULTS The differences between gold and plastic electrodes did not appear to be practically significant. For both electrode types, we observed heating below 4°C for straight wires whose lengths were multiples of ½ the radiofrequency (RF) wavelength and stronger heating (over 15°C) for wire lengths that were odd multiples of ¼ RF wavelength, consistent with the antenna effect. CONCLUSIONS The antenna effect, which has received little attention so far in the context of EEG-MRI safety, can play as significant a role as the loop effect (from electromagnetic induction) in the heating of EEG electrodes, and therefore wire lengths that are odd multiples of ¼ RF wavelength should be avoided. These results have important implications for the design of EEG electrodes and MRI studies as they help to minimize the risk to patients undergoing MRI with EEG electrodes in place.
Collapse
Affiliation(s)
- Mukund Balasubramanian
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A
| | - William M Wells
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A
| | - John R Ives
- Department of Neuroscience, University of Western Ontario, London, Ontario, Canada
- Ives EEG Solutions, Inc., Newburyport, Massachusetts, U.S.A
| | | | - Robert V Mulkern
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A
| | - Darren B Orbach
- Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A
| |
Collapse
|
50
|
Golestanirad L, Iacono MI, Keil B, Angelone LM, Bonmassar G, Fox MD, Herrington T, Adalsteinsson E, LaPierre C, Mareyam A, Wald LL. Construction and modeling of a reconfigurable MRI coil for lowering SAR in patients with deep brain stimulation implants. Neuroimage 2016; 147:577-588. [PMID: 28011252 DOI: 10.1016/j.neuroimage.2016.12.056] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 11/13/2016] [Accepted: 12/19/2016] [Indexed: 10/20/2022] Open
Abstract
Post-operative MRI of patients with deep brain simulation (DBS) implants is useful to assess complications and diagnose comorbidities, however more than one third of medical centers do not perform MRIs on this patient population due to stringent safety restrictions and liability risks. A new system of reconfigurable magnetic resonance imaging head coil composed of a rotatable linearly-polarized birdcage transmitter and a close-fitting 32-channel receive array is presented for low-SAR imaging of patients with DBS implants. The novel system works by generating a region with low electric field magnitude and steering it to coincide with the DBS lead trajectory. We demonstrate that the new coil system substantially reduces the SAR amplification around DBS electrodes compared to commercially available circularly polarized coils in a cohort of 9 patient-derived realistic DBS lead trajectories. We also show that the optimal coil configuration can be reliably identified from the image artifact on B1+ field maps. Our preliminary results suggest that such a system may provide a viable solution for high-resolution imaging of DBS patients in the future. More data is needed to quantify safety limits and recommend imaging protocols before the novel coil system can be used on patients with DBS implants.
Collapse
Affiliation(s)
- Laleh Golestanirad
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
| | - 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, USA
| | - Boris Keil
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Institute of Medical Physics and Radiation Protection, THM, Life Science Engineering, Giessen, Germany
| | - 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, USA
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Michael D Fox
- Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Todd Herrington
- Partners Neurology, Massachusetts General Hospital, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Elfar Adalsteinsson
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA
| | - Cristen LaPierre
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Azma Mareyam
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Lawrence L Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA
| |
Collapse
|