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Zilberti L, Arduino A, Torchio R, Zanovello U, Baruffaldi F, Sanchez-Lopez H, Bettini P, Alotto P, Chiampi M, Bottauscio O. Orthopedic implants affect the electric field induced by switching gradients in MRI. Magn Reson Med 2024; 91:398-412. [PMID: 37772634 DOI: 10.1002/mrm.29861] [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: 04/28/2023] [Revised: 08/18/2023] [Accepted: 08/20/2023] [Indexed: 09/30/2023]
Abstract
PURPOSE To investigate whether the risk of peripheral nerve stimulation increases in the presence of bulky metallic prostheses implanted in a patient's body. METHODS A computational tool was used to calculate the electric field (E-field) induced in a realistic human model due to the action of gradient fields. The calculations were performed both on the original version of the anatomical model and on a version modified through "virtual surgery" to incorporate knee, hip, and shoulder prostheses. Five exam positions within a body gradient coil and one position using a head gradient coil were simulated, subjecting the human model to the readout gradient from an EPI sequence. The induced E-field in models with and without prostheses was compared, focusing on the nerves and all other tissues (both including and excluding the bones from the analysis). RESULTS In the nerves, the most pronounced increase in the E-field (+24%) was observed around the knee implant during an abdominal MRI (Y axis readout). When extending the analysis to encompass all tissues (excluding bones), the greatest amplification (+360%) occurred around the knee implant during pelvic MRI (Z axis readout). Notable increases in E-field peaks were also identified around the shoulder and hip implants in multiple scenarios. CONCLUSION Based on the presented results, further investigations aimed at quantifying the threshold of nerve stimulation in the presence of bulky implants are desirable.
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Affiliation(s)
- Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
| | | | - Riccardo Torchio
- Department of Industrial Engineering, Università degli Studi di Padova, Padova, Italy
| | | | | | - Hector Sanchez-Lopez
- Research Center for Medical Artificial Intelligence, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Paolo Bettini
- Department of Industrial Engineering, Università degli Studi di Padova, Padova, Italy
| | - Piergiorgio Alotto
- Department of Industrial Engineering, Università degli Studi di Padova, Padova, Italy
| | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
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2
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Noetscher GM, Serano PJ, Horner M, Prokop A, Hanson J, Fujimoto K, Brown J, Nazarian A, Ackerman J, Makaroff SN. An in silico testbed for fast and accurate MR labeling of orthopedic implants. eLife 2023; 12:RP90440. [PMID: 38096104 PMCID: PMC10721214 DOI: 10.7554/elife.90440] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2023] Open
Abstract
One limitation on the ability to monitor health in older adults using magnetic resonance (MR) imaging is the presence of implants, where the prevalence of implantable devices (orthopedic, cardiac, neuromodulation) increases in the population, as does the pervasiveness of conditions requiring MRI studies for diagnosis (musculoskeletal diseases, infections, or cancer). The present study describes a novel multiphysics implant modeling testbed using the following approaches with two examples: (1) an in silico human model based on the widely available Visible Human Project (VHP) cryo-section dataset; (2) a finite element method (FEM) modeling software workbench from Ansys (Electronics Desktop/Mechanical) to model MR radio frequency (RF) coils and the temperature rise modeling in heterogeneous media. The in silico VHP-Female model (250 parts with an additional 40 components specifically characterizing embedded implants and resultant surrounding tissues) corresponds to a 60-year-old female with a body mass index of 36. The testbed includes the FEM-compatible in silico human model, an implant embedding procedure, a generic parameterizable MRI RF birdcage two-port coil model, a workflow for computing heat sources on the implant surface and in adjacent tissues, and a thermal FEM solver directly linked to the MR coil simulator to determine implant heating based on an MR imaging study protocol. The primary target is MR labeling of large orthopedic implants. The testbed has very recently been approved by the US Food and Drug Administration (FDA) as a medical device development tool for 1.5 T orthopedic implant examinations.
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Affiliation(s)
- Gregory M Noetscher
- Electrical & Computer Eng. Dept, Worcester Polytechnic InstituteWorcesterUnited States
| | | | | | | | | | | | - James Brown
- Micro Systems Enigineering, Inc, an affiliate of BiotronikLake OswegoUnited States
| | - Ara Nazarian
- Musculoskeletal Translational Innovation Initiative, Department of Orthopedic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical SchoolBostonUnited States
| | - Jerome Ackerman
- Harvard Medical SchoolBostonUnited States
- Athinoula A Martinos Center for Biomed. Imaging, Massachusetts General HospitalCharlestownUnited States
| | - Sergey N Makaroff
- Electrical & Computer Eng. Dept, Worcester Polytechnic InstituteWorcesterUnited States
- Athinoula A Martinos Center for Biomed. Imaging, Massachusetts General HospitalCharlestownUnited States
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3
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Zanovello U, Fuss C, Arduino A, Bottauscio O. Efficient prediction of MRI gradient-induced heating for guiding safety testing of conductive implants. Magn Reson Med 2023; 90:2011-2018. [PMID: 37382200 DOI: 10.1002/mrm.29787] [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: 04/19/2023] [Revised: 05/29/2023] [Accepted: 06/15/2023] [Indexed: 06/30/2023]
Abstract
PURPOSE To propose an efficient numerical method to predict the temperature increase of an implantable medical device induced by any linearly polarized homogeneous magnetic field, according to the ISO 10974 methodology for testing of gradient-induced device heating. THEORY AND METHODS The concepts of device-specific power and temperature tensors are introduced to mathematically describe the electromagnetic and thermal anisotropic behavior of the device, from which the device heating for an arbitrary exposure direction can be predicted. The proposed method is compared to a brute-force approach based on simulations, and validated by applying it to four reference orthopedic implants with a commercial simulation software. RESULTS The proposed method requires about 5% $$ \% $$ of the time required by the brute-force approach, and 30% $$ \% $$ of the memory occupancy. The temperature increase predicted by the proposed method over a range of incident magnetic field exposures deviated from brute-force direct simulations by less than± $$ \pm $$ 0.3% $$ \% $$ . CONCLUSION The proposed method allows efficient prediction of the heating of an implantable medical device induced by any linearly polarized homogeneous magnetic field using a small fraction of the simulations required by the brute-force approach. The results can be used to predict the worst-case orientation of the gradient field, for subsequent experimental characterization according to the ISO 10974 standard.
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Affiliation(s)
- Umberto Zanovello
- Metrologia dei materiali innovativi e scienze della vita, Istituto Nazionale di Ricerca Metrologica, Torino, Italy
| | | | - Alessandro Arduino
- Metrologia dei materiali innovativi e scienze della vita, Istituto Nazionale di Ricerca Metrologica, Torino, Italy
| | - Oriano Bottauscio
- Metrologia dei materiali innovativi e scienze della vita, Istituto Nazionale di Ricerca Metrologica, Torino, Italy
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4
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Noetscher GM, Serano PJ, Horner M, Prokop A, Hanson J, Fujimoto K, Brown JE, Nazarian A, Ackerman J, Makaroff SN. An In-Silico Testbed for Fast and Accurate MR Labeling of Orthopaedic Implants. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.16.549234. [PMID: 37649909 PMCID: PMC10465017 DOI: 10.1101/2023.07.16.549234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
One limitation on the ability to monitor health in older adults using Magnetic Resonance (MR) imaging is the presence of implants, where the prevalence of implantable devices (orthopedic, cardiac, neuromodulation) increases in the population, as does the pervasiveness of conditions requiring MRI studies for diagnosis (musculoskeletal diseases, infections, or cancer). The present study describes a novel multiphysics implant modeling testbed using the following approaches with two examples: - an in-silico human model based on the widely available Visible Human Project (VHP) cryo-section dataset; - a finite element method (FEM) modeling software workbench from Ansys (Electronics Desktop/Mechanical) to model MR radio frequency (RF) coils and the temperature rise modeling in heterogeneous media. The in-silico VHP Female model (250 parts with an additional 40 components specifically characterizing embedded implants and resultant surrounding tissues) corresponds to a 60-year-old female with a body mass index (BMI) of 36. The testbed includes the FEM-compatible in-silico human model, an implant embedding procedure, a generic parameterizable MRI RF birdcage two-port coil model, a workflow for computing heat sources on the implant surface and in adjacent tissues, and a thermal FEM solver directly linked to the MR coil simulator to determine implant heating based on an MR imaging study protocol. The primary target is MR labeling of large orthopaedic implants. The testbed has very recently been approved by the US Food and Drug Administration (FDA) as a medical device development tool (MDDT) for 1.5 T orthopaedic implant examinations.
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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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Arduino A, Baruffaldi F, Bottauscio O, Chiampi M, Martinez JA, Zanovello U, Zilberti L. Computational dosimetry in MRI in presence of hip, knee or shoulder implants: do we need accurate surgery models? Phys Med Biol 2022; 67. [PMID: 36541561 DOI: 10.1088/1361-6560/aca5e6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 11/24/2022] [Indexed: 11/27/2022]
Abstract
Objective.To quantify the effects of different levels of realism in the description of the anatomy around hip, knee or shoulder implants when simulating, numerically, radiofrequency and gradient-induced heating in magnetic resonance imaging. This quantification is needed to define how precise the digital human model modified with the implant should be to get realistic dosimetric assessments.Approach. The analysis is based on a large number of numerical simulations where four 'levels of realism' have been adopted in modelling human bodies carrying orthopaedic implants.Main results. Results show that the quantification of the heating due to switched gradient fields does not strictly require a detailed local anatomical description when preparing the digital human model carrying an implant. In this case, a simple overlapping of the implant CAD with the body anatomy is sufficient to provide a quite good and conservative estimation of the heating. On the contrary, the evaluation of the electromagnetic field distribution and heating caused by the radiofrequency field requires an accurate description of the tissues around the prosthesis.Significance. The results of this paper provide hints for selecting the 'level of realism' in the definition of the anatomical models with embedded passive implants when performing simulations that should reproduce, as closely as possible, thein vivoscenarios of patients carrying orthopaedic implants.
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Affiliation(s)
| | | | | | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
| | | | | | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
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7
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Classification Scheme of Heating Risk during MRI Scans on Patients with Orthopaedic Prostheses. Diagnostics (Basel) 2022; 12:diagnostics12081873. [PMID: 36010224 PMCID: PMC9406867 DOI: 10.3390/diagnostics12081873] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 07/25/2022] [Accepted: 07/28/2022] [Indexed: 12/02/2022] Open
Abstract
Due to the large variety of possible clinical scenarios, a reliable heating-risk assessment is not straightforward when patients with arthroplasty undergo MRI scans. This paper proposes a simple procedure to estimate the thermal effects induced in patients with hip, knee, or shoulder arthroplasty during MRI exams. The most representative clinical scenarios were identified by a preliminary frequency analysis, based on clinical service databases, collecting MRI exams of 11,658 implant carrier patients. The thermal effects produced by radiofrequency and switching gradient fields were investigated through 588 numerical simulations performed on an ASTM-like phantom, considering four prostheses, two static field values, seven MR sequences, and seven regions of imaging. The risk assessment was inspired by standards for radiofrequency fields and by scientific studies for gradient fields. Three risk tiers were defined for the radiofrequency, in terms of whole-body and local SAR averages, and for GC fields, in terms of temperature elevation. Only 50 out of 588 scenarios require some caution to be managed. Results showed that the whole-body SAR is not a self-reliant safety parameter for patients with metallic implants. The proposed numerical procedure can be easily extended to any other scenario, including the use of detailed anatomical models.
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8
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Bassen H, Zaidi T. Parameters Affecting Worst-Case Gradient-Field Heating of Passive Conductive Implants. J Magn Reson Imaging 2022; 56:1197-1204. [PMID: 35778374 DOI: 10.1002/jmri.28321] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 06/11/2022] [Accepted: 06/13/2022] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND Testing MRI gradient-induced heating of implanted medical devices is required by regulatory organizations and others. A gradient heating test of the ISO 10974 Technical Specification (TS) for active implants was adopted for this study of passive hip implants. All but one previous study of hip implants used nonuniform gradient exposure fields in clinical scanners and reported heating of less than 5 °C. This present study adapted methods of the TS, addressing the unmet need for identifying worst-case heating via exposures to uniform gradient fields. PURPOSE To identify gradient-field parameters affecting maximum heating in vitro for a hip implant and a cylindrical titanium disk. STUDY TYPE Computational simulations and experimental validation of induced heating. PHANTOM Tissue-simulating gel. FIELD STRENGTH 42 T/s RMS, sinusoidal, continuous B fields with high spatial uniformity ASSESSMENT: Hip implant heating at 1-10 kHz, via computational modeling, validated by limited point measurements. Experimental measurements of exposures of an implant at 42 T/s for 4, 6, and 9 kHz, analyzed at 50, 100, and 150 seconds. STATISTICAL TESTS One sample student's t-test to assess difference between computational and experimental results. Experimental vs. computational results were not significantly different (p < 0.05). RESULTS Maximum simulated temperature rise (10-minute exposure) was 10 °C at 1 kHz and 0.66 °C at 10 kHz. The ratio of the rise for 21 T/s vs. 42 T/s RMS was 4, after stabilizing at 50 seconds (dB/dt ratio squared). DATA CONCLUSIONS Heating of an implant is proportional to the frequency of the B field and the implant's cross-sectional area and is greater for a thickness on the order of its skin depth. Testing with lower values of dB/dt RMS with lower cost amplifiers enables prediction of heating at higher values for dB/dt squared (per ISO TS) with identical frequency components and waveforms, once thermal equilibrium occurs. EVIDENCE LEVEL 1 TECHNICAL EFFICACY: Stage 1.
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Affiliation(s)
- Howard Bassen
- Division of Biomedical Physics, Center for Devices and Radiological Health, US Food and Drug Administration, Maryland, USA
| | - Tayeb Zaidi
- Division of Biomedical Physics, Center for Devices and Radiological Health, US Food and Drug Administration, Maryland, USA
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9
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Arduino A, Bottauscio O, Chiampi M, Zanovello U, Zilberti L. A contribution to MRI safety testing related to gradient-induced heating of medical devices. Magn Reson Med 2022; 88:930-944. [PMID: 35344605 PMCID: PMC9314691 DOI: 10.1002/mrm.29235] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 01/22/2022] [Accepted: 02/24/2022] [Indexed: 12/26/2022]
Abstract
PURPOSE To theoretically investigate the feasibility of a novel procedure for testing the MRI gradient-induced heating of medical devices and translating the results into clinical practice. METHODS The concept of index of stress is introduced by decoupling the time waveform characteristics of the gradient field signals from the field spatial distribution within an MRI scanner. This index is also extended to consider the anisotropy of complex bulky metallic implants. Merits and drawbacks of the proposed index of stress are investigated through virtual experiments. In particular, the values of the index of stress evaluated for realistic orthopedic implants placed within an ASTM phantom are compared with accurate heating simulations performed with 2 anatomic body models (a man and a woman) implanted through a virtual surgery procedure. RESULTS The manipulation of the proposed index of stress allows to identify regions within the MRI bore where the implant could affect the safety of the examinations. Furthermore, the conducted analysis shows that the power dissipated into the implant by the induced eddy currents is a dosimetric quantity that estimates well the maximum temperature increase in the tissues surrounding the implant. CONCLUSION The results support the adoption of an anisotropic index of stress to regulate the gradient-induced heating of geometrically complex implants. They also pave the way for a laboratory characterization of the implants based on electrical measurements, rather than on thermal measurements. The next step will be to set up a standardized experimental procedure to evaluate the index of stress associated with an implant.
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Affiliation(s)
| | | | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
| | | | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
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10
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Fujimoto K, Zaidi TA, Lampman D, Guag JW, Etheridge S, Habara H, Rajan SS. Comparison of SAR distribution of hip and knee implantable devices in 1.5T conventional cylindrical-bore and 1.2T open-bore vertical MRI systems. Magn Reson Med 2021; 87:1515-1528. [PMID: 34775615 DOI: 10.1002/mrm.29007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 08/15/2021] [Accepted: 08/24/2021] [Indexed: 11/11/2022]
Abstract
PURPOSE There is increasing use of open-bore vertical MR systems that consist of two planar RF coils. A recent study showed that the RF-induced heating of a neuromodulation device was much lower in the open-bore system at the brain and the chest imaging landmarks. This study focused on the hip and knee implants and compared the specific absorption rate (SAR) distribution in human models in a 1.2T open-bore coil with that of a 1.5T conventional birdcage coil. METHODS Computational modeling results were compared against the measurement values using a saline phantom. The differences in RF exposure were examined between a 1.2T open-bore coil and a 1.5T conventional birdcage coil using SAR in an anatomical human model. RESULTS Modeling setups were validated. The body placed closed to the coil elements led to high SAR values in the birdcage system compared with the open-bore system. CONCLUSION Our computational modeling showed that the 1.2T planar system demonstrated a lower intensity of SAR distribution adjacent to hip and knee implants compared with the 1.5T conventional birdcage system.
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Affiliation(s)
- Kyoko Fujimoto
- U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Tayeb A Zaidi
- U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | | | - Joshua W Guag
- U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | | | - Hideta Habara
- Healthcare Business Unit, Hitachi, Taito, Tokyo, Japan
| | - Sunder S Rajan
- U.S. Food and Drug Administration, Silver Spring, Maryland, USA
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Hartwig V, Virgili G, Mattei FE, Biagini C, Romeo S, Zeni O, Scarfì MR, Massa R, Campanella F, Landini L, Gobba F, Modenese A, Giovannetti G. Occupational exposure to electromagnetic fields in magnetic resonance environment: an update on regulation, exposure assessment techniques, health risk evaluation, and surveillance. Med Biol Eng Comput 2021; 60:297-320. [PMID: 34586563 DOI: 10.1007/s11517-021-02435-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 08/27/2021] [Indexed: 12/15/2022]
Abstract
Magnetic resonance imaging (MRI) is one of the most-used diagnostic imaging methods worldwide. There are ∼50,000 MRI scanners worldwide each of which involves a minimum of five workers from different disciplines who spend their working days around MRI scanners. This review analyzes the state of the art of literature about the several aspects of the occupational exposure to electromagnetic fields (EMF) in MRI: regulations, literature studies on biological effects, and health surveillance are addressed here in detail, along with a summary of the main approaches for exposure assessment. The original research papers published from 2013 to 2021 in international peer-reviewed journals, in the English language, are analyzed, together with documents published by legislative bodies. The key points for each topic are identified and described together with useful tips for precise safeguarding of MRI operators, in terms of exposure assessment, studies on biological effects, and health surveillance.
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Affiliation(s)
- Valentina Hartwig
- Institute of Clinical Physiology (IFC), Italian National Research Council (CNR), Via G. Moruzzi 1, 56124, Pisa, San Cataldo, Italy.
| | - Giorgio Virgili
- Virgili Giorgio, Via G. Pastore 2, 26040, Crespina-Lorenzana, Italy
| | - F Ederica Mattei
- West Systems S.R.L, Via Don Mazzolari 25, 56025, Pontedera, PI, Italy
| | - Cristiano Biagini
- Associazione Italiana Tecnici Dell'Imaging in Risonanza Magnetica, AITIRM, Via XX Settembre 76, 50129, Florence, Italy
| | - Stefania Romeo
- Institute for Electromagnetic Sensing of the Environment (IREA) , Italian National Research Council (CNR), Via Diocleziano 328, 80124, Naples, Italy
| | - Olga Zeni
- Institute for Electromagnetic Sensing of the Environment (IREA) , Italian National Research Council (CNR), Via Diocleziano 328, 80124, Naples, Italy
| | - Maria Rosaria Scarfì
- Institute for Electromagnetic Sensing of the Environment (IREA) , Italian National Research Council (CNR), Via Diocleziano 328, 80124, Naples, Italy
| | - Rita Massa
- Institute for Electromagnetic Sensing of the Environment (IREA) , Italian National Research Council (CNR), Via Diocleziano 328, 80124, Naples, Italy.,Department of Physics, University Federico II, Via Cinthia 21, 80126, Naples, Italy
| | - Francesco Campanella
- Dipartimento di medicina, epidemiologia, Igiene del Lavoro E Ambientale, Inail, Via Fontana Candida 1, 00078 Monte Porzio Catone, Rome, Italy
| | - Luigi Landini
- Fondazione Toscana "G. Monasterio", Via G. Moruzzi 1, 56124, Pisa, San Cataldo, Italy
| | - Fabriziomaria Gobba
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125, Modena, Italy
| | - Alberto Modenese
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125, Modena, Italy
| | - Giulio Giovannetti
- Institute of Clinical Physiology (IFC), Italian National Research Council (CNR), Via G. Moruzzi 1, 56124, Pisa, San Cataldo, Italy
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Arduino A, Zanovello U, Hand J, Zilberti L, Brühl R, Chiampi M, Bottauscio O. Heating of hip joint implants in MRI: The combined effect of RF and switched-gradient fields. Magn Reson Med 2021; 85:3447-3462. [PMID: 33483979 PMCID: PMC7986841 DOI: 10.1002/mrm.28666] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 12/09/2020] [Accepted: 12/09/2020] [Indexed: 12/20/2022]
Abstract
PURPOSE To investigate how the simultaneous exposure to gradient and RF fields affects the temperature rise in patients with a metallic hip prosthesis during an MRI session. METHODS In silico analysis was performed with an anatomically realistic human model with CoCrMo hip implant in 12 imaging positions. The analysis was performed at 1.5 T and 3 T, considering four clinical sequences: turbo spin-echo, EPI, gradient-echo, and true fast imaging sequence with steady precession. The exposure to gradient and RF fields was evaluated separately and superposed, by adopting an ad hoc computational algorithm. Temperature increase within the body, rather than specific absorption rate, was used as a safety metric. RESULTS With the exception of gradient-echo, all investigated sequences produced temperature increases higher than 1 K after 360 seconds, at least for one body position. In general, RF-induced heating dominates the turbo spin-echo sequence, whereas gradient-induced heating prevails with EPI; the situation with fast imaging sequence with steady precession is more diversified. The RF effects are enhanced when the implant is within the RF coil, whereas the effects of gradient fields are maximized if the prosthesis is outside the imaging region. Cases for which temperature-increase thresholds were exceeded were identified, together with the corresponding amount of tissue mass involved and the exposure time needed to reach these limits. CONCLUSION The analysis confirms that risky situations may occur when a patient carrying a hip implant undergoes an MRI exam and that, in some cases, the gradient field heating may be significant. In general, exclusion criteria only based on whole-body specific absorption rate may not be sufficient to ensure patients' safety.
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Affiliation(s)
| | | | - Jeff Hand
- School of Biomedical Engineering and Imaging SciencesKing’s College LondonLondonUnited Kingdom
| | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRIM)TorinoItaly
| | - Rüdiger Brühl
- Physikalisch‐Technische BundesanstaltBraunschweig and BerlinGermany
| | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRIM)TorinoItaly
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