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Qian E, Poojar P, Fung M, Jin Z, Vaughan JT, Shrivastava D, Gultekin D, Fernandes T, Geethanath S. Magnetic resonance fingerprinting based thermometry (MRFT): application to ex vivoimaging near DBS leads. Phys Med Biol 2023; 68:17NT01. [PMID: 37489867 DOI: 10.1088/1361-6560/acea54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 07/25/2023] [Indexed: 07/26/2023]
Abstract
The purpose of this study is to demonstrate the first work ofT1-based magnetic resonance thermometry using magnetic resonance fingerprinting (dubbed MRFT). We compared temperature estimation of MRFT with proton resonance frequency shift (PRFS) thermometry onex vivobovine muscle. We demonstrated MRFT's feasibility in predicting temperature onex vivobovine muscles with deep brain stimulation (DBS) lead.B0maps generated from MRFT were compared with gold standardB0maps near the DBS lead. MRFT and PRFS estimated temperatures were compared in the presence of motion. All experiments were performed on a 3 Tesla whole-body GE Premier system with a 21-channel receive head coil (GE Healthcare, Milwaukee, WI). Four fluoroptic probes were used to measure the temperature at the center of a cold muscle (probe 1), the room temperature water bottle (probe 2), and the center and periphery of the heated muscle (probes 3 and 4). We selected regions of interest (ROIs) around the location of the probes and used simple linear regression to generate the temperature sensitivity calibration equations that convertT1maps and Δsmaps to temperature maps. We then repeated the same setup and compared MRFT and PRFS thermometry temperature estimation with gold standard probe measurements. For the MRFT experiment on DBS lead, we taped the probe to the tip of the DBS lead and used a turbo spin echo sequence to induce heating near the lead. We selected ROIs around the tip of the lead to compare MRFT temperature estimation with probe measurements and compared with PRFS temperature estimation. Vendor-suppliedB0mapping sequence was acquired to compare with MRFT-generatedB0maps. We found strong linear relationships (R2> 0.958) betweenT1and temperature and Δsand temperatures in our temperature sensitivity calibration experiment. MRFT and PRFS thermometry both accurately predict temperature (RMSE < 1.55 °C) compared to probe measurements. MRFT estimated temperature near DBS lead has a similar trend as the probe temperature. BothB0maps show inhomogeneities around the lead. MRFT estimated temperature is less sensitive to motion.
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Affiliation(s)
- Enlin Qian
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
- Department of Biomedical Engineering, Columbia University, New York, NY, United States of America
| | - Pavan Poojar
- Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mt. Sinai, New York, NY, United States of America
| | - Maggie Fung
- GE Healthcare, New York, NY, United States of America
| | - Zhezhen Jin
- Department of Biostatistics, Columbia University, New York, NY, United States of America
| | - John Thomas Vaughan
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
- Department of Biomedical Engineering, Columbia University, New York, NY, United States of America
| | - Devashish Shrivastava
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
| | - David Gultekin
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
| | - Tiago Fernandes
- Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mt. Sinai, New York, NY, United States of America
- ISR - Lisboa/LARSyS and Department of Bioengineering, Instituto Superior Técnico-Universidade de Lisboa, Lisbon, Portugal
| | - Sairam Geethanath
- Columbia Magnetic Resonance Research Center, Columbia University, New York, NY, United States of America
- Accessible MR Laboratory, Biomedical Engineering and Imaging Institute, Dept. of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mt. Sinai, New York, NY, United States of America
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Scotti AM, Damen F, Gao J, Li W, Liew CW, Cai Z, Zhang Z, Cai K. Phase-independent thermometry by Z-spectrum MR imaging. Magn Reson Med 2022; 87:1731-1741. [PMID: 34752646 PMCID: PMC10029969 DOI: 10.1002/mrm.29072] [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: 05/24/2021] [Revised: 09/30/2021] [Accepted: 10/17/2021] [Indexed: 01/05/2023]
Abstract
PURPOSE Z-spectrum imaging, defined as the consecutive collection of images after saturating over a range of frequency offsets, has been recently proposed as a method to measure the fat-water fraction by the simultaneous detection of fat and water resonances. By incorporating a binomial pulse irradiated at each offset before the readout, the spectral selectivity of the sequence can be further amplified, making it possible to monitor the subtle proton resonance frequency shift that follows a change in temperature. METHODS We tested the hypothesis in aqueous and cream phantoms and in healthy mice, all under thermal challenge. The binomial module consisted of 2 sinc-shaped pulses of opposite phase separated by a delay. Such a delay served to spread out off-resonance spins, with the resulting excitation profile being a periodic function of the delay and the chemical shift. RESULTS During heating experiments, the water resonance shifted downfield, and by fitting the curve to a sine function it was possible to quantify the change in temperature. Results from Z-spectrum imaging correlated linearly with data from conventional MRI techniques like T1 mapping and phase differences from spoiled GRE. CONCLUSION Because the measurement is performed solely on magnitude images, the technique is independent of phase artifacts and is therefore applicable in mixed tissues (e.g., fat). We showed that Z-spectrum imaging can deliver reliable temperature change measurement in both muscular and fatty tissues.
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Affiliation(s)
- Alessandro M. Scotti
- Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Frederick Damen
- Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Jin Gao
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, USA
- Research Resources Center, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Weiguo Li
- Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA
- Research Resources Center, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Chong Wee Liew
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Zimeng Cai
- School of Medical Engineering, Southern Medical University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Image Processing, Southern Medical University, Guangzhou, China
| | - Zhuoli Zhang
- Department of Radiology, Northwestern University, Evanston, Illinois, USA
| | - Kejia Cai
- Department of Radiology, University of Illinois at Chicago, Chicago, Illinois, USA
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, USA
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Kuroda K, Yatsushiro S. New Insights into MR Safety for Implantable Medical Devices. Magn Reson Med Sci 2022; 21:110-131. [PMID: 35228487 PMCID: PMC9199981 DOI: 10.2463/mrms.rev.2021-0160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 01/08/2022] [Indexed: 12/24/2022] Open
Abstract
Over the last two decades, the status of MR safety has dramatically changed. In particular, ever since the MR-conditional cardiac device was approved by the Food and Drug Administration (FDA) in 2008 and by the Pharmaceuticals and Medical Devices Agency (PMDA) in 2012, the safety of patients with an implantable medical device (IMD) has been one of the most important issues in terms of MR use. In conjunction with the regulatory approvals for various IMDs, standards, technical specifications, and guidelines have also been rapidly created and developed. Many invaluable papers investigating and reviewing the history and status of MR use in the presence of IMDs already exist. As such, this review paper seeks to bridge the gap between clinical practice and the information that is obtained by standard-based tests and provided by an IMD's package insert or instructions for use. Interpretation of the gradient of the magnetic flux density intensity of the static magnetic field with respect to the magnetic displacement force is discussed, along with the physical background of RF field. The relationship between specific absorption rate (SAR) and B1+RMS, and their effects on image quality are described. In addition, insofar as providing new directions for future research and practice, the feasibility of safety test methods for RF-induced heating of IMDs using MR thermometry, evaluation of tissue heat damage, and challenges in cardiac IMDs will be discussed.
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Affiliation(s)
- Kagayaki Kuroda
- Department of Human and Information Sciences, School of Information Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan
| | - Satoshi Yatsushiro
- Department of Human and Information Sciences, School of Information Science and Technology, Tokai University, Hiratsuka, Kanagawa, Japan
- Biosim Laboratory, Bioview, Inc., Tokyo, Japan
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Sengupta S, Yan X, Hoyt TL, Drake G, Gunderman A, Chen Y. Minimal artifact actively shimmed metallic needles in MRI. Magn Reson Med 2021; 87:541-550. [PMID: 34411348 DOI: 10.1002/mrm.28977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 07/02/2021] [Accepted: 07/29/2021] [Indexed: 11/12/2022]
Abstract
PURPOSE Signal voids caused by metallic needles pose visualization and monitoring challenges in many MRI applications. In this work, we explore a solution to this problem in the form of an active shim insert that fits inside a needle and corrects the field disturbance (ΔB0 ) caused by the needle outside of it. METHODS The ΔB0 induced by a 4 mm outside-diameter titanium needle at 3T is modeled and a two-coil orthogonal shim set is designed and fabricated to shim the ΔB0 . Signal recovery around the needle is assessed in multiple orientations in a water phantom with four different pulse sequences. Phase stability around the needle is assessed in an ex-vivo porcine tissue dynamic gradient echo experiment with and without shimming. Additionally, heating of the shim insert is assessed under 8 min of continuous operation with 1A current and concurrent imaging. RESULTS An average recovery of ~63% of lost signal around the needle across orientations is shown with active shimming with a maximum current of 1.172 A. Signal recovery and correction of the underlying ΔB0 is shown to be independent of imaging sequence. Needle-induced phase gradients outside the perceptible signal void are also minimized with active shimming. Temperature rise of up to 0.9° Celsius is noted over 8 min of continuous 1A active shimming operation. CONCLUSION A sequence independent method for minimization of metallic needle induced signal loss using an active shim insert is presented. The method has potential benefits in a range of qualitative and quantitative interventional MRI applications.
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Affiliation(s)
- Saikat Sengupta
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Xinqiang Yan
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Tamarya L Hoyt
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Gary Drake
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Anthony Gunderman
- Department of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas, USA
| | - Yue Chen
- Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
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Zhang F, Jiang C, Li Y, Niu X, Long T, He C, Ding J, Li L, Li L. Investigation of Artifacts and Optimization in Proton Resonance Frequency Thermometry Towards Heating Risk Monitoring of Implantable Medical Devices in Magnetic Resonance Imaging. IEEE Trans Biomed Eng 2021; 68:3638-3646. [PMID: 34003743 DOI: 10.1109/tbme.2021.3081599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Artifacts limit the application of proton resonance frequency (PRF) thermometry for on-site, individualized heating evaluations of implantable medical devices such as deep brain stimulation (DBS) for use in magnetic resonance imaging (MRI). Its properties are unclear and the research on how to choose an unaffected measurement region is insufficient. METHODS The properties of PRF signals around the metallic DBS electrode were investigated through simulations and phantom experiments considering electromagnetic interferences from material susceptibility and the radio frequency (RF) interactions. A threshold method on phase difference Δϕ was used to define a measurement area to estimate heating at the electrode surface. Its performance was compared to that of the Bayesian magnitude method and probe measurements. RESULTS The B0 magnetic field inhomogeneity due to the electrode susceptibility was the main influencing factor on PRF compared to the RF artifact. Δϕ around the electrode followed normal distribution but was distorted. Underestimation occurred at places with high temperature rises. The noise was increased and could be well estimated from magnitude images using a modified NEMA method. The Δϕ-threshold method based on this knowledge outperformed the Bayesian magnitude method by more than 42% in estimation error of the electrode heating. CONCLUSION The findings favor the use of PRF with the proposed approach as a reliable method for electrode heating estimation. SIGNIFICANCE This study clarified the influence of device artifacts and could improve the performance of PRF thermometry for individualized heating assessments of patients with implants under MRI.
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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] [Track Full Text] [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.
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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
| | - 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
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Lutz NW, Bernard M. Contactless Thermometry by MRI and MRS: Advanced Methods for Thermotherapy and Biomaterials. iScience 2020; 23:101561. [PMID: 32954229 PMCID: PMC7489251 DOI: 10.1016/j.isci.2020.101561] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Control of temperature variation is of primordial importance in particular areas of biomedicine. In this context, medical treatments such as hyperthermia and cryotherapy, and also the development and use of hydrogel-based biomaterials, are of particular concern. To enable accurate temperature measurement without perturbing or even destroying the biological tissue or material to be monitored, contactless thermometry methods are preferred. Among these, the most suitable are based on magnetic resonance imaging and spectroscopy (MRI, MRS). Here, we address the latest developments in this field as well as their current and anticipated practical applications. We highlight recent progress aimed at rendering MR thermometry faster and more reproducible, versatile, and sophisticated and provide our perspective on how these new techniques broaden the range of applications in medical treatments and biomaterial development by enabling insight into finer details of thermal behavior. Thus, these methods facilitate optimization of clinical and industrial heating and cooling protocols.
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Affiliation(s)
- Norbert W. Lutz
- Aix-Marseille University, CNRS, CRMBM, 27 Bd Jean Moulin, 13005 Marseille, France
| | - Monique Bernard
- Aix-Marseille University, CNRS, CRMBM, 27 Bd Jean Moulin, 13005 Marseille, France
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Bruschewski M, Schmidt S, John K, Grundmann S, Schmitter S. An unbiased method for PRF-shift temperature measurements in convective heat transfer systems with functional parts made of metal. Magn Reson Imaging 2020; 75:124-133. [PMID: 33075452 DOI: 10.1016/j.mri.2020.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/22/2020] [Accepted: 10/14/2020] [Indexed: 10/23/2022]
Abstract
The purpose of this study is to provide a PRF-shift method for fluid temperature measurements in convective heat transfer systems, which contain functional parts made of metal. Such measurements are extremely useful to examine and design convective cooling systems for industrial devices. Metals like copper seem inevitable for such applications because no commonly available non-metallic material reaches the same level of thermal conductivity as for example copper. In MRI, electrically conductive parts embedded in the measured sample are known to produce various kinds of errors including errors in the image phase caused by eddy currents. Two methods are compared that can be used to remove the eddy currents induced phase: via the phase difference of two readouts at different echo times and via the sum of the phase of two acquisitions with reverse gradient polarity and same echo time. The latter method, termed Rot-Echo, provides a better measurement efficiency because of higher temperature sensitivity. Also, this technique is able to directly measure the eddy currents induced phase map. After verification in a stationary water experiment, the Rot-Echo method was applied to time-averaged temperature measurements in a Pin Fin heat exchanger, comprised of water flow that is heated by an array of copper pins. The temperature fields acquired in the Pin Fin heat exchanger under stable thermal-hydraulic conditions agreed well with data from temperature sensors. No eddy currents effects were visible in any of the data sets in the vicinity of the copper rods. In conclusion, this study shows that unbiased PRF-shift temperature measurements are feasible in complex flow systems even if metallic material is used for the functional parts.
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Affiliation(s)
| | - Simon Schmidt
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Kristine John
- Institute of Fluid Mechanics, University of Rostock, Rostock, Germany
| | - Sven Grundmann
- Institute of Fluid Mechanics, University of Rostock, Rostock, Germany
| | - Sebastian Schmitter
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany; Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany
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9
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Winter L, Seifert F, Zilberti L, Murbach M, Ittermann B. MRI‐Related Heating of Implants and Devices: A Review. J Magn Reson Imaging 2020; 53:1646-1665. [DOI: 10.1002/jmri.27194] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Lukas Winter
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Frank Seifert
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica Torino Italy
| | - Manuel Murbach
- ZMT Zurich MedTech AG Zurich Switzerland
- Institute for Molecular Instrumentation and Imaging (i3M) Universidad Politécnica de Valencia (UPV) Valencia Spain
| | - Bernd Ittermann
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
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10
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Destruel A, Fuentes M, Weber E, O'Brien K, Jin J, Liu F, Barth M, Crozier S. A numerical and experimental study of RF shimming in the presence of hip prostheses using adaptive SAR at 3 T. Magn Reson Med 2019; 81:3826-3839. [PMID: 30803001 DOI: 10.1002/mrm.27688] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 01/17/2019] [Accepted: 01/20/2019] [Indexed: 12/25/2022]
Abstract
PURPOSE Parallel transmission techniques in MRI have the potential to improve the image quality near metal implants at 3 T. However, current testing of implants only evaluates the risk of radiofrequency (RF) heating in phantoms in circularly polarized mode. We investigate the influence of changing the transmission settings in a 2-channel body coil on the peak temperature near 2 CoCrMo hip prostheses, using adaptive specific absorption rate (SAR) as an estimate of RF heating. METHODS Adaptive SAR is a SAR averaging method that is optimized to correlate with thermal simulations and limit the temperature to 39°C near hip implants. The simulated peak temperature was compared when using whole-body SAR, SAR10g , and adaptive SAR as a constraint for the maximum allowed input power. Adaptive SAR was used as a fast estimate of temperature to evaluate the trade-off between good image quality and low heating near the hip implants. Electromagnetic simulations were validated by simulating and measuring B1 maps and electric fields in a phantom at 3 T. RESULTS Simulations and measurements showed excellent agreement. Limiting whole-body SAR to 2 W/kg and SAR10g to 10 W/kg resulted in temperatures up to 49.3°C and 40.7°C near the hip implants after 30 minutes of RF exposure, respectively. Predictions based on adaptive SAR limited the temperature to 39°C, and allowed to improve the B1 field distribution while preventing peak temperatures near the hip implants. CONCLUSION Significant RF heating can occur at 3 T near hip implants when parallel transmission is used. Adaptive SAR can be integrated in RF shimming algorithms to improve the uniformity and reduce heating.
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Affiliation(s)
- Aurelien Destruel
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia.,Centre for Advanced Imaging, University of Queensland, St. Lucia, Australia
| | - Miguel Fuentes
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia.,Population Health Research on Electromagnetic Energy, School of Public Health and Preventive Medicine, Monash University, Clayton, Australia
| | - Ewald Weber
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia
| | - Kieran O'Brien
- Centre for Advanced Imaging, University of Queensland, St. Lucia, Australia.,Siemens Healthcare, Brisbane, Australia
| | - Jin Jin
- Siemens Healthineers USA, Los Angeles, California
| | - Feng Liu
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia
| | - Markus Barth
- Centre for Advanced Imaging, University of Queensland, St. Lucia, Australia
| | - Stuart Crozier
- School of Information Technology and Electrical Engineering, University of Queensland, St. Lucia, Australia
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11
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Weber H, Hargreaves BA, Daniel BL. Artifact-reduced imaging of biopsy needles with 2D multispectral imaging. Magn Reson Med 2017; 80:655-661. [PMID: 29285787 DOI: 10.1002/mrm.27056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 11/30/2017] [Accepted: 12/01/2017] [Indexed: 12/28/2022]
Abstract
PURPOSE Magnetic resonance (MR) guidance for biopsy procedures requires high intrinsic soft-tissue contrast. However, artifacts induced by the metallic needle can reduce its localization and require low-susceptibility needle materials with poorer cutting performance. In a proof of concept, we demonstrate the feasibility of 2D multispectral imaging (2DMSI) for both needle tracking and for needle artifact reduction for more precise needle localization and to enable the usage of needle materials with higher susceptibility. METHOD We applied 2DMSI for imaging of MR-compatible biopsy needles, conventional stainless-steel needles, and mixed-material needles and compared it to conventional techniques. In addition, we exploited intrinsic off-resonance information for passive needle tracking. RESULTS 2DMSI achieved a stronger reduction of the needle artifact compared to conventional techniques. For the mixed-material needles, the artifact was reduced to a level below that for MR-compatible needles with conventional imaging. The passive tracking also improved the ability to pinpoint the needle. CONCLUSION 2DMSI is promising for both needle tracking and artifact-reduced imaging of biopsy needles for a more precise needle localization. 2DMSI may be particularly promising for needles inducing large distortions or for targeting of small lesions. In addition, it may enable the use of needle materials with higher susceptibility and potentially better sampling performance. Magn Reson Med 80:655-661, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Hans Weber
- Department of Radiology, Stanford University, Palo Alto, California, USA
| | - Brian A Hargreaves
- Department of Radiology, Stanford University, Palo Alto, California, USA
| | - Bruce L Daniel
- Department of Radiology, Stanford University, Palo Alto, California, USA
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12
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Weber H, Ghanouni P, Pascal-Tenorio A, Pauly KB, Hargreaves BA. MRI monitoring of focused ultrasound sonications near metallic hardware. Magn Reson Med 2017; 80:259-271. [PMID: 29215150 DOI: 10.1002/mrm.27034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 11/13/2017] [Accepted: 11/14/2017] [Indexed: 01/06/2023]
Abstract
PURPOSE To explore the temperature-induced signal change in two-dimensional multi-spectral imaging (2DMSI) for fast thermometry near metallic hardware to enable MR-guided focused ultrasound surgery (MRgFUS) in patients with implanted metallic hardware. METHOD 2DMSI was optimized for temperature sensitivity and applied to monitor focus ultrasound surgery (FUS) sonications near metallic hardware in phantoms and ex vivo porcine muscle tissue. Further, we evaluated its temperature sensitivity for in vivo muscle in patients without metallic hardware. In addition, we performed a comparison of temperature sensitivity between 2DMSI and conventional proton-resonance-frequency-shift (PRFS) thermometry at different distances from metal devices and different signal-to-noise ratios (SNR). RESULTS 2DMSI thermometry enabled visualization of short ultrasound sonications near metallic hardware. Calibration using in vivo muscle yielded a constant temperature sensitivity for temperatures below 43 °C. For an off-resonance coverage of ± 6 kHz, we achieved a temperature sensitivity of 1.45%/K, resulting in a minimum detectable temperature change of ∼2.5 K for an SNR of 100 with a temporal resolution of 6 s per frame. CONCLUSION The proposed 2DMSI thermometry has the potential to allow MR-guided FUS treatments of patients with metallic hardware and therefore expand its reach to a larger patient population. Magn Reson Med 80:259-271, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Hans Weber
- Department of Radiology, Stanford University, Palo Alto, California, USA
| | - Pejman Ghanouni
- Department of Radiology, Stanford University, Palo Alto, California, USA
| | | | - Kim Butts Pauly
- Department of Radiology, Stanford University, Palo Alto, California, USA
| | - Brian A Hargreaves
- Department of Radiology, Stanford University, Palo Alto, California, USA
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Zhang Y, Poorman ME, Grissom WA. Dual-echo Z-shimmed proton resonance frequency-shift magnetic resonance thermometry near metallic ablation probes: Technique and temperature precision. Magn Reson Med 2017; 78:2299-2306. [PMID: 28185304 DOI: 10.1002/mrm.26634] [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: 08/05/2016] [Revised: 01/11/2017] [Accepted: 01/11/2017] [Indexed: 11/09/2022]
Abstract
PURPOSE To improve the precision of proton resonance frequency-shift magnetic resonance thermometry near ablation probes by recovering near-probe image signals that are typically lost due to magnetic susceptibility-induced field distortions. METHODS A dual-echo gradient-recalled echo sequence was implemented, in which the first echo was under- or over-refocused in the slice dimension to recover image signal and temperature precision near a probe, and the second echo was fully refocused to obtain image signal everywhere else in the slice. A penalized maximum likelihood algorithm was implemented to estimate a single temperature map from both echoes. Agar phantom and ex vivo experiments with and without microwave heating at 3 T evaluated how much temperature precision was improved near a microwave ablator compared to a conventional single-echo scan as a function of slice and needle orientation in the magnet. RESULTS The number of near-probe voxels with temperature standard deviation σ>1°C was decreased by 51% in the phantom experiment, averaged across orientations, and by 31% in the pork. Temperature maps near the probe were more smoother and more complete in all orientations. CONCLUSION Dual-echo z-shimmed temperature imaging can recover image signal for more precise temperature mapping near metallic ablation probes. Magn Reson Med 78:2299-2306, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Yuxin Zhang
- Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Megan E Poorman
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - William A Grissom
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
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Ferromagnetic particles as magnetic resonance imaging temperature sensors. Nat Commun 2016; 7:12415. [PMID: 27503610 PMCID: PMC4980494 DOI: 10.1038/ncomms12415] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 06/30/2016] [Indexed: 02/01/2023] Open
Abstract
Magnetic resonance imaging is an important technique for identifying different types of tissues in a body or spatial information about composite materials. Because temperature is a fundamental parameter reflecting the biological status of the body and individual tissues, it would be helpful to have temperature maps superimposed on spatial maps. Here we show that small ferromagnetic particles with a strong temperature-dependent magnetization, can be used to produce temperature-dependent images in magnetic resonance imaging with an accuracy of about 1 °C. This technique, when further developed, could be used to identify inflammation or tumours, or to obtain spatial maps of temperature in various medical interventional procedures such as hyperthermia and thermal ablation. This method could also be used to determine temperature profiles inside nonmetallic composite materials. Magnetic resonance imaging can distinguish between different tissue types by measuring the proton distribution in a living sample. Here, the authors demonstrate how this technique can be extended to provide temperature information by using ferromagnetic particles with temperature-dependent magnetization.
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