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Winter L, Periquito J, Kolbitsch C, Pellicer-Guridi R, Nunes RG, Häuer M, Broche L, O'Reilly T. Open-source magnetic resonance imaging: Improving access, science, and education through global collaboration. NMR IN BIOMEDICINE 2024; 37:e5052. [PMID: 37986655 DOI: 10.1002/nbm.5052] [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: 01/08/2023] [Revised: 08/01/2023] [Accepted: 09/09/2023] [Indexed: 11/22/2023]
Abstract
Open-source practices and resources in magnetic resonance imaging (MRI) have increased substantially in recent years. This trend started with software and data being published open-source and, more recently, open-source hardware designs have become increasingly available. These developments towards a culture of sharing and establishing nonexclusive global collaborations have already improved the reproducibility and reusability of code and designs, while providing a more inclusive approach, especially for low-income settings. Community-driven standardization and documentation efforts are further strengthening and expanding these milestones. The future of open-source MRI is bright and we have just started to discover its full collaborative potential. In this review we will give an overview of open-source software and open-source hardware projects in human MRI research.
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Affiliation(s)
- Lukas Winter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - João Periquito
- Department of Infection, Immunity & Cardiovascular Disease, The University of Sheffield, Sheffield, UK
| | - Christoph Kolbitsch
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | | | - Rita G Nunes
- Institute for Systems and Robotics and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Martin Häuer
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
- Open Source Ecology Germany e.V. (nonprofit), Berlin, Germany
| | - Lionel Broche
- Biomedical Physics, University of Aberdeen, Aberdeen, UK
| | - Tom O'Reilly
- Leiden University Medical Center (LUMC), Leiden, The Netherlands
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2
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Terekhov M, Elabyad IA, Lohr D, Reiter T, Kögler C, Lanz T, Schreiber LM. Complementary analysis of specific absorption rate safety for an 8Tx/16Rx array with central symmetry of elements for magnetic resonance imaging of the human heart and abdominopelvic organs at 7 T. NMR IN BIOMEDICINE 2023; 36:e5023. [PMID: 37620002 DOI: 10.1002/nbm.5023] [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: 10/04/2022] [Revised: 05/16/2023] [Accepted: 07/16/2023] [Indexed: 08/26/2023]
Abstract
A complementary safety assessment of the specific absorption rate (SAR) of the electromagnetic energy was performed in a prototype 8Tx/16Rx RF array for cardiac magnetic resonance imaging (MRI) at 7 T. The study aimed to address two critical aspects of 7-T SAR safety not always explicitly examined by coil vendors: (i) the influence of an RF-array position on a peak SAR value, and (ii) the risk of exceeding the permitted maximal SAR in the tissue surrounding conductive passive implants. The full-wave 3D electromagnetic simulations for the thorax with shifted array position and the whole-body volume in the presence of a dental retainer, an intrauterine contraceptive device (IUD), and a hip joint implant, were performed for two human voxel models. The effect of the array displacement on the SAR was simulated for seven array locations on the thorax shifted from the central position in different directions on 50 mm. The peak SAR values for both models were analyzed for the three phase-only transmit vectors optimized for B1 + homogeneity and transmit efficiency. Peak SAR values due to the shifts of the array position increase up to ≈50%. The worst-case peak SAR value for a dental retainer was found to be in the range of 10% of the maximal SAR in the tissue within the array's borders. For the IUD and artificial hip joint implants the effect was found to be negligible (peak SAR < 1% of the SAR within array borders). In addition to simulations for cardiac MRI, we performed a preliminary B1 + shimming and SAR-safety analysis for the same RF-array at various positions lower on the body trunk to assess a potential application in imaging abdominopelvic organs (prostate, kidney, and liver). The most promising target for an ad hoc alternative application of the array was found to be the prostate.
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Affiliation(s)
- Maxim Terekhov
- Department of Cardiovascular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg (UKW), Würzburg, Germany
| | - Ibrahim A Elabyad
- Department of Cardiovascular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg (UKW), Würzburg, Germany
| | - David Lohr
- Department of Cardiovascular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg (UKW), Würzburg, Germany
| | - Theresa Reiter
- Department of Internal Medicine I/Cardiology, University Hospital Würzburg (UKW), Würzburg, Germany
| | | | | | - Laura M Schreiber
- Department of Cardiovascular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg (UKW), Würzburg, Germany
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Silemek B, Seifert F, Petzold J, Brühl R, Ittermann B, Winter L. Wirelessly interfacing sensor-equipped implants and MR scanners for improved safety and imaging. Magn Reson Med 2023; 90:2608-2626. [PMID: 37533167 DOI: 10.1002/mrm.29818] [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: 02/07/2023] [Revised: 07/12/2023] [Accepted: 07/13/2023] [Indexed: 08/04/2023]
Abstract
PURPOSE To investigate a novel reduced RF heating method for imaging in the presence of active implanted medical devices (AIMDs) which employs a sensor-equipped implant that provides wireless feedback. METHODS The implant, consisting of a generator case and a lead, measures RF-inducedE $$ E $$ -fields at the implant tip using a simple sensor in the generator case and transmits these values wirelessly to the MR scanner. Based on the sensor signal alone, parallel transmission (pTx) excitation vectors were calculated to suppress tip heating and maintain image quality. A sensor-based imaging metric was introduced to assess the image quality. The methodology was studied at 7T in testbed experiments, and at a 3T scanner in an ASTM phantom containing AIMDs instrumented with six realistic deep brain stimulation (DBS) lead configurations adapted from patients. RESULTS The implant successfully measured RF-inducedE $$ E $$ -fields (Pearson correlation coefficient squared [R2 ] = 0.93) and temperature rises (R2 = 0.95) at the implant tip. The implant acquired the relevant data needed to calculate the pTx excitation vectors and transmitted them wirelessly to the MR scanner within a single shot RF sequence (<60 ms). Temperature rises for six realistic DBS lead configurations were reduced to 0.03-0.14 K for heating suppression modes compared to 0.52-3.33 K for the worst-case heating, while imaging quality remained comparable (five of six lead imaging scores were ≥0.80/1.00) to conventional circular polarization (CP) images. CONCLUSION Implants with sensors that can communicate with an MR scanner can substantially improve safety for patients in a fast and automated manner, easing the current burden for MR personnel.
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Affiliation(s)
- Berk Silemek
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Frank Seifert
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Johannes Petzold
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Rüdiger Brühl
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Bernd Ittermann
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Lukas Winter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
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4
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Sadeghi-Tarakameh A, DelaBarre L, Zulkarnain NIH, Harel N, Eryaman Y. Implant-friendly MRI of deep brain stimulation electrodes at 7 T. Magn Reson Med 2023; 90:2627-2642. [PMID: 37533196 PMCID: PMC10543551 DOI: 10.1002/mrm.29825] [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: 03/03/2023] [Revised: 07/18/2023] [Accepted: 07/19/2023] [Indexed: 08/04/2023]
Abstract
PURPOSE The purpose of this study is to present a strategy to calculate the implant-friendly (IF) excitation modes-which mitigate the RF heating at the contacts of deep brain stimulation (DBS) electrodes-of multichannel RF coils at 7 T. METHODS An induced RF current on an implantable electrode generates a scattered magnetic field whose left-handed circularly polarizing component (B 1 + $$ B{1}^{+} $$ ) is approximated using aB 1 + $$ B{1}^{+} $$ -mapping technique and subsequently used as a gauge for the electrode's induced current. Using this approach, the relative induced currents resulting from each channel of a multichannel RF coil on the DBS electrode were calculated. The IF modes of the corresponding multichannel coil were determined by calculating the null space of the relative induced currents. The proposed strategy was tested and validated for unilateral and bilateral commercial DBS electrodes (directional lead; Infinity DBS system, Abbott Laboratories) placed inside a uniform phantom by performing heating and imaging studies on a 7T MRI scanner using a 16-channel transceive RF coil. RESULTS Neither individual IF modes nor shim solutions obtained from IF modes induced significant temperature increase when used for a high-power turbo spin-echo sequence. In contrast, shimming with the scanner's toolbox (i.e., based on per-channelB 1 + $$ B{1}^{+} $$ fields) resulted in a more than 2°C temperature increase for the same amount of input power. CONCLUSION A strategy for calculating the IF modes of a multichannel RF coil is presented. This strategy was validated using a 16-channel RF coil at 7 T for unilateral and bilateral commercial DBS electrodes inside a uniform phantom.
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Affiliation(s)
| | - Lance DelaBarre
- Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Noam Harel
- Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota, USA
| | - Yigitcan Eryaman
- Center for Magnetic Resonance Research (CMRR), University of Minnesota, Minneapolis, Minnesota, USA
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Espiritu J, Berangi M, Cwieka H, Iskhakova K, Kuehne A, Florian Wieland D, Zeller-Plumhoff B, Niendorf T, Willumeit-Römer R, Seitz JM. 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.
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Affiliation(s)
| | - Mostafa Berangi
- MRI.TOOLS GmbH, Berlin, Germany
- Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Hanna Cwieka
- Institute of Metallic Biomaterials, Helmholtz Zentrum Hereon, Geesthacht, Germany
| | - Kamila Iskhakova
- Institute of Metallic Biomaterials, Helmholtz Zentrum Hereon, Geesthacht, Germany
| | | | - D.C. Florian Wieland
- Institute of Metallic Biomaterials, Helmholtz Zentrum Hereon, Geesthacht, Germany
| | | | - Thoralf Niendorf
- MRI.TOOLS GmbH, Berlin, Germany
- Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Berlin, Germany
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
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Petzold J, Schmitter S, Silemek B, Winter L, Speck O, Ittermann B, Seifert F. Towards an integrated radiofrequency safety concept for implant carriers in MRI based on sensor-equipped implants and parallel transmission. NMR IN BIOMEDICINE 2023; 36:e4900. [PMID: 36624556 DOI: 10.1002/nbm.4900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 10/11/2022] [Accepted: 01/04/2023] [Indexed: 06/15/2023]
Abstract
To protect implant carriers in MRI from excessive radiofrequency (RF) heating it has previously been suggested to assess that hazard via sensors on the implant. Other work recommended parallel transmission (pTx) to actively mitigate implant-related heating. Here, both ideas are integrated into one comprehensive safety concept where native pTx safety (without implant) is ensured by state-of-the-art field simulations and the implant-specific hazard is quantified in situ using physical sensors. The concept is demonstrated by electromagnetic simulations performed on a human voxel model with a simplified spinal-cord implant in an eight-channel pTx body coil at 3 T . To integrate implant and native safety, the sensor signal must be calibrated in terms of an established safety metric (e.g., specific absorption rate [SAR]). Virtual experiments show that E -field and implant-current sensors are well suited for this purpose, while temperature sensors require some caution, and B 1 probes are inadequate. Based on an implant sensor matrix Q s , constructed in situ from sensor readings, and precomputed native SAR limits, a vector space of safe RF excitations is determined where both global (native) and local (implant-related) safety requirements are satisfied. Within this safe-excitation subspace, the solution with the best image quality in terms of B 1 + magnitude and homogeneity is then found by a straightforward optimization algorithm. In the investigated example, the optimized pTx shim provides a 3-fold higher mean B 1 + magnitude compared with circularly polarized excitation for a maximum implant-related temperature increase ∆ T imp ≤ 1 K . To date, sensor-equipped implants interfaced to a pTx scanner exist as demonstrator items in research labs, but commercial devices are not yet within sight. This paper aims to demonstrate the significant benefits of such an approach and how this could impact implant-related RF safety in MRI. Today, the responsibility for safe implant scanning lies with the implant manufacturer and the MRI operator; within the sensor concept, the MRI manufacturer would assume much of the operator's current responsibility.
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Affiliation(s)
- Johannes Petzold
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
- Biomedical Magnetic Resonance, Otto von Guericke University Magdeburg, Magdeburg, Germany
| | - Sebastian Schmitter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Berk Silemek
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Lukas Winter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Oliver Speck
- Biomedical Magnetic Resonance, Otto von Guericke University Magdeburg, Magdeburg, Germany
| | - Bernd Ittermann
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Frank Seifert
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
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Berangi M, Kuehne A, Waiczies H, Niendorf T. MRI of Implantation Sites Using Parallel Transmission of an Optimized Radiofrequency Excitation Vector. Tomography 2023; 9:603-620. [PMID: 36961008 PMCID: PMC10037644 DOI: 10.3390/tomography9020049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/03/2023] [Accepted: 03/05/2023] [Indexed: 03/25/2023] Open
Abstract
Postoperative care of orthopedic implants is aided by imaging to assess the healing process and the implant status. MRI of implantation sites might be compromised by radiofrequency (RF) heating and RF transmission field (B1+) inhomogeneities induced by electrically conducting implants. This study examines the applicability of safe and B1+-distortion-free MRI of implantation sites using optimized parallel RF field transmission (pTx) based on a multi-objective genetic algorithm (GA). Electromagnetic field simulations were performed for eight eight-channel RF array configurations (f = 297.2 MHz), and the most efficient array was manufactured for phantom experiments at 7.0 T. Circular polarization (CP) and orthogonal projection (OP) algorithms were applied for benchmarking the GA-based shimming. B1+ mapping and MR thermometry and imaging were performed using phantoms mimicking muscle containing conductive implants. The local SAR10g of the entire phantom in GA was 12% and 43.8% less than the CP and OP, respectively. Experimental temperature mapping using the CP yielded ΔT = 2.5-3.0 K, whereas the GA induced no extra heating. GA-based shimming eliminated B1+ artefacts at implantation sites and enabled uniform gradient-echo MRI. To conclude, parallel RF transmission with GA-based excitation vectors provides a technical foundation en route to safe and B1+-distortion-free MRI of implantation sites.
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Affiliation(s)
- Mostafa Berangi
- Berlin Ultrahigh Field Facility, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
- Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
- MRI.TOOLS GmbH, 13125 Berlin, Germany
| | | | | | - Thoralf Niendorf
- Berlin Ultrahigh Field Facility, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany
- Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
- MRI.TOOLS GmbH, 13125 Berlin, Germany
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Wooldridge J, Arduino A, Zilberti L, Zanovello U, Chiampi M, Clementi V, Bottauscio O. Gradient coil and radiofrequency induced heating of orthopaedic implants in MRI: influencing factors. Phys Med Biol 2021; 66. [PMID: 34847533 DOI: 10.1088/1361-6560/ac3eab] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 11/30/2021] [Indexed: 11/12/2022]
Abstract
Patients with implanted orthopaedic devices represent a growing number of subjects undergoing magnetic resonance imaging (MRI) scans each year. MRI safety labelling is required for all implants under the EU Medical Device Regulations to ensure regulatory compliance, with each device assessed through standardised testing procedures. In this paper, we employ parametric studies to assess a range of clinically relevant factors that cause tissue heating, performing simulations with both radiofrequency (RF) and gradient coil (GC) switching fields, the latter of which is often overlooked in the literature. A series of 'worst-case' scenarios for both types of excitation field is discussed. In the case of GC fields, large volume implants and large plate areas with the field orientated perpendicular to the plane cause the highest heating levels, along with sequences with high rates of field switching. Implant heating from RF fields is driven primarily from the 'antenna effect', with thin, linear implants of resonant length resulting in the highest temperature rises. In this work, we show that simplifications may be made to the field sequence and in some cases the device geometry without significantly compromising the accuracy of the simulation results, enabling the possibility for generic estimates of the implant heating for orthopaedic device manufacturers and opportunities to simplify the safety compliance process.
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Affiliation(s)
- J Wooldridge
- National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, United Kingdom
| | - A Arduino
- Istituto Nazionale di Ricerca Metrologica, Str. delle Cacce, 91, I-10135 Torino TO, Italy
| | - L Zilberti
- Istituto Nazionale di Ricerca Metrologica, Str. delle Cacce, 91, I-10135 Torino TO, Italy
| | - U Zanovello
- Istituto Nazionale di Ricerca Metrologica, Str. delle Cacce, 91, I-10135 Torino TO, Italy
| | - M Chiampi
- Istituto Nazionale di Ricerca Metrologica, Str. delle Cacce, 91, I-10135 Torino TO, Italy
| | - V Clementi
- IRCCS Istituto Ortopedico Rizzoli, Laboratorio di Tecnologia Medica, Via di Barbiano 1/10, I-40136 Bologna, Italy
| | - O Bottauscio
- Istituto Nazionale di Ricerca Metrologica, Str. delle Cacce, 91, I-10135 Torino TO, Italy
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Godinez F, Tomi-Tricot R, Quesson B, Barthel M, Lykowsky G, Scott G, Razavi R, Hajnal J, Malik S. An 8 channel parallel transmit system with current sensor feedback for MRI-guided interventional applications. Phys Med Biol 2021; 66. [PMID: 34649230 DOI: 10.1088/1361-6560/ac2fbe] [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: 03/06/2021] [Accepted: 10/14/2021] [Indexed: 11/12/2022]
Abstract
Background.Parallel transmit (pTx) has introduced many benefits to magnetic resonance imaging (MRI) with regard to decreased specific absorption rates and improved transmit field homogeneity, of particular importance in applications at higher magnetic field strengths. PTx has also been proposed as a solution to mitigating dangerous RF induced heating of elongated conductive devices such as those used in cardiac interventions. In this work we present a system that can augment a conventional scanner with pTx, in particular for use in interventional MRI for guidewire safety, by adjusting the amplitude and phase of each channel right before the start of the imaging pulses.Methods.The pTx system was designed to work in-line with a 1.5 T MRI while the RF synthesis and imaging control was maintained on the host MR scanner. The add-on pTx system relies on the RF transmit signal, unblanking pulse, and a protocol driven trigger from the scanner. The RF transmit was split into multiple fully modulated transmit signals to drive an array of custom transceiver coils. The performance of the 8-channel implementation was tested with regards to active and real-time control of RF induced currents on a standard guidewire, heating mitigation tests, and anatomical imaging in sheep.Results. The pTx system was intended to update RF shims in real-time and it was demonstrated that the safe RF shim could be determined while the guidewire is moved. The anatomical imaging demonstrated that cardiac anatomy and neighbouring superficial structures could be fully characterized with the pTx system inline.Conclusion.We have presented the design and performance of a real-time feedback control pTx system capable of adding such capabilities to a conventional MRI with the focus of guidewire imaging in cardiac interventional MRI applications.
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Affiliation(s)
- Felipe Godinez
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United kingdom.,Centre for the Developing Brain, King's College London, London, United kingdom.,Department of Radiology, University of California Davis, Sacramento, California, United States of America
| | - Raphael Tomi-Tricot
- MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom
| | - Bruno Quesson
- Centre de recherche Cardio-Thoracique de Bordeaux/IHU Liryc, INSERM U1045-University of Bordeaux, Pessac, France
| | | | | | - Greig Scott
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, United States of America
| | - Reza Razavi
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United kingdom.,Department of Congenital Cardiology, Evelina London Children's Healthcare, Guys and St Thomas' NHS Foundation Trust, London, United Kingdom
| | - Joseph Hajnal
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United kingdom.,Centre for the Developing Brain, King's College London, London, United kingdom
| | - Shaihan Malik
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United kingdom.,Centre for the Developing Brain, King's College London, London, United kingdom
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10
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Silemek B, Seifert F, Petzold J, Hoffmann W, Pfeiffer H, Speck O, Rose G, Ittermann B, Winter L. Rapid safety assessment and mitigation of radiofrequency induced implant heating using small root mean square sensors and the sensor matrix Q s. Magn Reson Med 2021; 87:509-527. [PMID: 34397114 DOI: 10.1002/mrm.28968] [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: 05/06/2021] [Revised: 07/20/2021] [Accepted: 07/26/2021] [Indexed: 11/07/2022]
Abstract
PURPOSE Rapid detection and mitigation of radiofrequency (RF)-induced implant heating during MRI based on small and low-cost embedded sensors. THEORY AND METHODS A diode and a thermistor are embedded at the tip of an elongated mock implant. RF-induced voltages or temperature change measured by these root mean square (RMS) sensors are used to construct the sensor Q-Matrix (QS ). Hazard prediction, monitoring and parallel transmit (pTx)-based mitigation using these sensors is demonstrated in benchtop measurements at 300 MHz and within a 3T MRI. RESULTS QS acquisition and mitigation can be performed in <20 ms demonstrating real-time capability. The acquisitions can be performed using safe low powers (<3 W) due to the high reading precision of the diode (126 µV) and thermistor (26 µK). The orthogonal projection method used for pTx mitigation was able to reduce the induced signals and temperatures in all 155 investigated locations. Using the QS approach in a pTx capable 3T MRI with either a two-channel body coil or an eight-channel head coil, RF-induced heating was successfully assessed, monitored and mitigated while the image quality outside the implant region was preserved. CONCLUSION Small (<1.5 mm3 ) and low-cost (<1 €) RMS sensors embedded in an implant can provide all relevant information to predict, monitor and mitigate RF-induced heating in implants, while preserving image quality. The proposed pTx-based QS approach is independent of simulations or in vitro testing and therefore complements these existing safety assessments.
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Affiliation(s)
- Berk Silemek
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Frank Seifert
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Johannes Petzold
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Werner Hoffmann
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Harald Pfeiffer
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Oliver Speck
- Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany.,German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany.,Leibniz Institute for Neurobiology (LIN), Magdeburg, Germany.,Center for Behavioral Brain Sciences (CBBS), Magdeburg, Germany
| | - Georg Rose
- Center for Behavioral Brain Sciences (CBBS), Magdeburg, Germany.,Institute for Medical Engineering and Research Campus STIMULATE, University of Magdeburg, Magdeburg, Germany
| | - Bernd Ittermann
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Lukas Winter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
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11
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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.
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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
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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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