1
|
Shellock FG, Rosen MS, Webb A, Kimberly WT, Rajan S, Nacev AN, Crues JV. Managing Patients With Unlabeled Passive Implants on MR Systems Operating Below 1.5 T. J Magn Reson Imaging 2024; 59:1514-1522. [PMID: 37767980 DOI: 10.1002/jmri.29002] [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: 07/31/2023] [Revised: 08/29/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
The standard of care for managing a patient with an implant is to identify the item and to assess the relative safety of scanning the patient. Because the 1.5 T MR system is the most prevalent scanner in the world and 3 T is the highest field strength in widespread use, implants typically have "MR Conditional" (i.e., an item with demonstrated safety in the MR environment within defined conditions) labeling at 1.5 and/or 3 T only. This presents challenges for a facility that has a scanner operating at a field strength below 1.5 T when encountering a patient with an implant, because scanning the patient is considered "off-label." In this case, the supervising physician is responsible for deciding whether to scan the patient based on the risks associated with the implant and the benefit of magnetic resonance imaging (MRI). For a passive implant, the MRI safety-related concerns are static magnetic field interactions (i.e., force and torque) and radiofrequency (RF) field-induced heating. The worldwide utilization of scanners operating below 1.5 T combined with the increasing incidence of patients with implants that need MRI creates circumstances that include patients potentially being subjected to unsafe imaging conditions or being denied access to MRI because physicians often lack the knowledge to perform an assessment of risk vs. benefit. Thus, physicians must have a complete understanding of the MRI-related safety issues that impact passive implants when managing patients with these products on scanners operating below 1.5 T. This monograph provides an overview of the various clinical MR systems operating below 1.5 T and discusses the MRI-related factors that influence safety for passive implants. Suggestions are provided for the management of patients with passive implants labeled MR Conditional at 1.5 and/or 3 T, referred to scanners operating below 1.5 T. The purpose of this information is to empower supervising physicians with the essential knowledge to perform MRI exams confidently and safely in patients with passive implants. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.
Collapse
Affiliation(s)
- Frank G Shellock
- Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Matthew S Rosen
- Department of Radiology, A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Andrew Webb
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - W Taylor Kimberly
- Division of Neurocritical Care, Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | | | | | - John V Crues
- ProNet Imaging Medical Group and RadNet Management, Los Angeles, California, USA
| |
Collapse
|
2
|
Duan S, Wu X, Shi J, Li W, Dong Q, Xin SX. Study of the radiofrequency-induced heating inside the human head with dental implants at 7 T. Bioelectromagnetics 2024; 45:82-93. [PMID: 37860924 DOI: 10.1002/bem.22490] [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: 02/26/2023] [Revised: 08/28/2023] [Accepted: 10/09/2023] [Indexed: 10/21/2023]
Abstract
Conductive dental implants are commonly used in restorative therapy to replace missing teeth in patients. Ensuring the radiofrequency (RF) safety of these patients is crucial when performing 7 T magnetic resonance scans of their heads. This study aimed to investigate RF-induced heating inside the human head with dental implants at 7 T. Dental implants and their attachments were fabricated and integrated into an anatomical head model, creating different measurement configurations (MCs). Numerical simulations were conducted using a 7 T transmit coil loaded with the anatomical head model, both with and without dental implants. The maximum temperatures inside the head for various MCs were computed using the maximum permissible input powers (MPIPs) obtained without dental implants and compared with published limits. Additionally, the MPIPs with dental implants were calculated for scenarios where the temperature limits were exceeded. The maximum temperatures observed inside the head ranged from 38.4°C to 39.6°C. The MPIPs in the presence of dental implants were 81.9%-97.3% of the MPIPs in the absence of dental implants for scenarios that exceeded the regulatory limit. RF-induced heating effect of the dental implants was not significant. The safe scanning condition in terms of RF exposure was achievable for patients with dental implants. For patients with conductive dental implants of unknown configuration, it is recommended to reduce the input power by 18.1% of MPIP without dental implants to ensure RF safety.
Collapse
Affiliation(s)
- Song Duan
- Department of Radiation Oncology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Xiuxiu Wu
- Department of Radiation Oncology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Juntian Shi
- Department of Radiation Oncology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, China
| | - Wenhui Li
- Department of Dentistry, Air Force Hospital of Southern Theater Command of PLA, Guangzhou, Guangdong, China
| | - Qingshan Dong
- Department of Stomatology, General Hospital of Central Theater Command of PLA, WuHan, China
| | - Sherman Xuegang Xin
- Biophysics and Medical Imaging Lab, School of Medicine, South China University of Technology, Guangzhou, Guangdong, China
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Park BS, Guag JW, Jeong H, Rajan SS, McCright B. A new method to improve RF safety of implantable medical devices using inductive coupling at 3.0 T MRI. MAGMA (NEW YORK, N.Y.) 2023; 36:933-943. [PMID: 37566311 PMCID: PMC10667457 DOI: 10.1007/s10334-023-01109-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 06/21/2023] [Accepted: 07/03/2023] [Indexed: 08/12/2023]
Abstract
OBJECTIVE To enhance RF safety when implantable medical devices are located within the body coil but outside the imaging region by using a secondary resonator (SR) to reduce electric fields, the corresponding specific absorption rate (SAR), and temperature change during MRI. MATERIALS AND METHODS This study was conducted using numerical simulations with an American Society for Testing and Materials (ASTM) phantom and adult human models of Ella and Duke from Virtual Family Models, along with corresponding experimental results of temperature change obtained using the ASTM phantom. The circular SR was designed with an inner diameter of 150 mm and a width of 6 mm. Experimental measurements were carried out using a 3 T Medical Implant Test System (MITS) body coil, electromagnetic (EM) field mapping probes, and an ASTM phantom. RESULTS The magnitudes of B1+ (|B1+|) and SAR1g were reduced by 15.2% and 5.85% within the volume of interest (VoI) of an ASTM phantom, when a SR that generates opposing electromagnetic fields was utilized. Likewise, the Δ|B1+| and ΔSAR1g were reduced by up to 56.7% and 57.5% within the VoI of an Ella model containing a copper rod when an opposing SR was used. CONCLUSION A novel method employing the designed SR, which generates opposing magnetic fields to partially shield a sample, has been proposed to mitigate the risk of induced-RF heating at the VoI through numerical simulations and corresponding experiments under various conditions at 3.0 T.
Collapse
Affiliation(s)
- Bu S Park
- Division of Cellular and Gene Therapies (DCGT), OTAT, CBER, Food and Drug Administration (FDA), Silver Spring, MD, USA.
| | - Joshua W Guag
- Division of Biomedical Physics (DBP), OSEL, CDRH, FDA, Silver Spring, MD, USA
| | - Hongbae Jeong
- Division of Biomedical Physics (DBP), OSEL, CDRH, FDA, Silver Spring, MD, USA
| | - Sunder S Rajan
- Division of Biomedical Physics (DBP), OSEL, CDRH, FDA, Silver Spring, MD, USA
| | - Brent McCright
- Division of Cellular and Gene Therapies (DCGT), OTAT, CBER, Food and Drug Administration (FDA), Silver Spring, MD, USA
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
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.
Collapse
|
7
|
Shaffer A, Nigh N, Weisbaum D, Anderson A, Wszalek T, Sutton BP, Webb A, Damon B, Moussa I, Arnold PM. Cardiothoracic and Vascular Surgery Implant Compatibility With Ultrahigh Field Magnetic Resonance Imaging (4.7 Tesla and 7 Tesla). Am J Cardiol 2023; 201:239-246. [PMID: 37392607 DOI: 10.1016/j.amjcard.2023.05.062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 05/23/2023] [Accepted: 05/31/2023] [Indexed: 07/03/2023]
Abstract
The use of 7 Tesla (T) magnetic resonance imaging (MRI) is expanding across medical specialties, particularly, clinical neurosciences and orthopedics. Investigational 7 T MRI has also been performed in cardiology. A limiting factor for expansion of the role of 7 T, irrespective of the body part being imaged, is the sparse testing of biomedical implant compatibility at field strengths >3 T. Implant compatibility can be tested following the American Society for Testing and Materials International guidelines. To assess the current state of cardiovascular implant safety at field strengths >3 T, a systematic search was performed using PubMed, Web of Science, and citation matching. Studies written in English that included at least 1 cardiovascular-related implant and at least 1 safety outcome (deflection angle, torque, or temperature change) were included. Data were extracted for the implant studied, implant composition, deflection angle, torque, and temperature change, and the American Society for Testing and Materials International standards were followed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines for scoping reviews were followed. A total of 9 studies were included. A total of 34 cardiovascular-related implants tested ex vivo at 7 T and 91 implants tested ex vivo at 4.7 T were included. The implants included vascular grafts and conduits, vascular access ports, peripheral and coronary stents, caval filters, and artificial valves. A total of 2 grafts, 1 vascular access port, 2 vena cava filters, and 5 stents were identified as incompatible with the 7 T MRI. All incompatible stents were 40 mm in length. Based on the safety outcomes reported, we identify several implants that may be compatible with >3 T MRI. This scoping review seeks to concisely summarize all the cardiovascular-related implants tested for ultrahigh field MRI compatibility to date.
Collapse
Affiliation(s)
- Annabelle Shaffer
- Carle Illinois College of Medicine, University of Illinois Urbana Champaign, Urbana, Illinois
| | - Noah Nigh
- Carle Illinois College of Medicine, University of Illinois Urbana Champaign, Urbana, Illinois
| | - David Weisbaum
- Department of Neurosurgery, Carle Foundation Hospital, Urbana, Illinois
| | - Aaron Anderson
- Carle Illinois Advanced Imaging Center, Carle Foundation Hospital, Urbana, Illinois; Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Tracey Wszalek
- Carle Illinois Advanced Imaging Center, Carle Foundation Hospital, Urbana, Illinois; Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Bradley P Sutton
- Carle Illinois College of Medicine, University of Illinois Urbana Champaign, Urbana, Illinois; Carle Illinois Advanced Imaging Center, Carle Foundation Hospital, Urbana, Illinois; Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Andrew Webb
- Carle Illinois Advanced Imaging Center, Carle Foundation Hospital, Urbana, Illinois; Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands; Leiden University Medical Center, Leiden, The Netherlands
| | - Bruce Damon
- Carle Illinois Advanced Imaging Center, Carle Foundation Hospital, Urbana, Illinois; Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Issam Moussa
- Carle Illinois College of Medicine, University of Illinois Urbana Champaign, Urbana, Illinois; Heart and Vascular Institute, Carle Foundation Hospital, Urbana, Illinois
| | - Paul M Arnold
- Carle Illinois College of Medicine, University of Illinois Urbana Champaign, Urbana, Illinois; Department of Neurosurgery, Carle Foundation Hospital, Urbana, Illinois.
| |
Collapse
|
8
|
Bottauscio O, Arduino A, Chiampi M, Zilberti L. Simplified modeling of implanted medical devices with metallic filamentary closed loops exposed to low or medium frequency magnetic fields. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2023; 229:107316. [PMID: 36566651 DOI: 10.1016/j.cmpb.2022.107316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 12/12/2022] [Accepted: 12/16/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND AND OBJECTIVES Electric currents are induced in implanted medical devices with metallic filamentary closed loops (e.g., fixation grids, stents) when exposed to time varying magnetic fields, as those generated during certain diagnostic and therapeutic biomedical treatments. A simplified methodology to efficiently compute these currents, to estimate the altered electromagnetic field distribution in the biological tissues and to assess the consequent biological effects is proposed for low or medium frequency fields. METHODS The proposed methodology is based on decoupling the handling of the filamentary wire and the anatomical body. To do this, a circuital solution is adopted to study the metallic filamentary implant and this solution is inserted in the electromagnetic field solution involving the biological tissues. The Joule losses computed in the implant are then used as a forcing term for the thermal problem defined by the bioheat Pennes' equation. The methodology is validated against a model problem, where a reference solution is available. RESULTS The proposed simplified methodology is proved to be in good agreement with solutions provided by alternative approaches. In particular, errors in the amplitude of the currents induced in the wires result to be always lower than 3%. After the validation, the methodology is applied to check the interactions between the magnetic field generated by different biomedical devices and a skull grid, which represents a complex filamentary wire implant. CONCLUSIONS The proposed simplified methodology, suitable to be applied to closed loop wires in the low to intermediate frequency range, is found to be sufficiently accurate and easy to apply in realistic exposure scenarios. This modeling tool allows analyzing different types of small implants, from coronary and biliary duct stents to orthopedic grids, under a variety of exposure scenarios.
Collapse
Affiliation(s)
- Oriano Bottauscio
- Istituto Nazionale di Ricerca Metrologica (INRiM), Strada Delle Cacce 91, 10135 Torino, Italy.
| | - Alessandro Arduino
- Istituto Nazionale di Ricerca Metrologica (INRiM), Strada Delle Cacce 91, 10135 Torino, Italy
| | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRiM), Strada Delle Cacce 91, 10135 Torino, Italy
| | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRiM), Strada Delle Cacce 91, 10135 Torino, Italy
| |
Collapse
|
9
|
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.
Collapse
Affiliation(s)
| | | | | | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
| | | | | | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, Italy
| |
Collapse
|
10
|
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] [MESH Headings] [Grants] [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.
Collapse
Affiliation(s)
| | | | - Mario Chiampi
- Istituto Nazionale di Ricerca Metrologica (INRIM)TorinoItaly
| | | | - Luca Zilberti
- Istituto Nazionale di Ricerca Metrologica (INRIM)TorinoItaly
| |
Collapse
|
11
|
Mittendorff L, Young A, Sim J. A narrative review of current and emerging MRI safety issues: What every MRI technologist (radiographer) needs to know. J Med Radiat Sci 2022; 69:250-260. [PMID: 34498813 PMCID: PMC9163467 DOI: 10.1002/jmrs.546] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 08/19/2021] [Accepted: 08/31/2021] [Indexed: 12/13/2022] Open
Abstract
Magnetic resonance imaging (MRI) has been traditionally regarded as a safe imaging modality due to the absence of ionising radiation. However, MRI is a source of potential hazards with a variety of risks including, but not limited to, those associated with the various electromagnetic fields used for imaging. All MRI technologists (radiographers) require sound knowledge of the physical principles of the MRI scanner and must understand the associated safety risks and how to avoid adverse events from occurring. MRI technologists now assume more responsibility in clinical decision-making, and their knowledge base has consequently had to expand significantly. In addition, rapid advancements in MRI technology and other correlated areas such as medical implant technology, and the associated increase in MRI safety issues, place increasing demands on the MRI technologist to constantly keep abreast of current and future developments. This article reviews current and emerging MRI safety issues relevant to the three MRI electromagnetic fields and highlights the key information that all MRI technologists should be fully cognisant of to ensure competent and safe practice within the MRI environment.
Collapse
Affiliation(s)
- Lisa Mittendorff
- Department of Anatomy and Medical Imaging, School of Medical SciencesThe University of AucklandAucklandNew Zealand
- Mercy Radiology, SilverdaleAucklandNew Zealand
| | - Adrienne Young
- Department of Anatomy and Medical Imaging, School of Medical SciencesThe University of AucklandAucklandNew Zealand
| | - Jenny Sim
- Department of Anatomy and Medical Imaging, School of Medical SciencesThe University of AucklandAucklandNew Zealand
- Department of Medical Imaging and Radiation Sciences, School of Primary and Allied Health CareMonash UniversityClaytonVICAustralia
| |
Collapse
|
12
|
Spronk T, Kraff O, Kreutner J, Schaefers G, Quick HH. Development and evaluation of a numerical simulation approach to predict metal artifacts from passive implants in MRI. MAGMA (NEW YORK, N.Y.) 2022; 35:485-497. [PMID: 34655346 PMCID: PMC9188622 DOI: 10.1007/s10334-021-00966-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 09/27/2021] [Accepted: 10/01/2021] [Indexed: 11/08/2022]
Abstract
OBJECTIVE This study presents the development and evaluation of a numerical approach to simulate artifacts of metallic implants in an MR environment that can be applied to improve the testing procedure for MR image artifacts in medical implants according to ASTM F2119. METHODS The numerical approach is validated by comparing simulations and measurements of two metallic test objects made of titanium and stainless steel at three different field strengths (1.5T, 3T and 7T). The difference in artifact size and shape between the simulated and measured artifacts were evaluated. A trend analysis of the artifact sizes in relation to the field strength was performed. RESULTS The numerical simulation approach shows high similarity (between 75% and 84%) of simulated and measured artifact sizes of metallic implants. Simulated and measured artifact sizes in relation to the field strength resulted in a calculation guideline to determine and predict the artifact size at one field strength (e.g., 3T or 7T) based on a measurement that was obtained at another field strength only (e.g. 1.5T). CONCLUSION This work presents a novel tool to improve the MR image artifact testing procedure of passive medical implants. With the help of this tool detailed artifact investigations can be performed, which would otherwise only be possible with substantial measurement effort on different MRI systems and field strengths.
Collapse
Affiliation(s)
- Tobias Spronk
- Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Kokereiallee 7, Building C84, 45141, Essen, Germany.
- High-Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
- MRI-STaR Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany.
| | - Oliver Kraff
- Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Kokereiallee 7, Building C84, 45141, Essen, Germany
| | - Jakob Kreutner
- MRI-STaR Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany
- MR:Comp GmbH, Testing Services for MR Safety and Compatibility, Gelsenkirchen, Germany
| | - Gregor Schaefers
- MRI-STaR Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany
- MR:Comp GmbH, Testing Services for MR Safety and Compatibility, Gelsenkirchen, Germany
| | - Harald H Quick
- Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Kokereiallee 7, Building C84, 45141, Essen, Germany
- High-Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| |
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
Germann C, Nanz D, Sutter R. Magnetic Resonance Imaging Around Metal at 1.5 Tesla: Techniques From Basic to Advanced and Clinical Impact. Invest Radiol 2021; 56:734-748. [PMID: 34074944 DOI: 10.1097/rli.0000000000000798] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
ABSTRACT During the last decade, metal artifact reduction in magnetic resonance imaging (MRI) has been an area of intensive research and substantial improvement. The demand for an excellent diagnostic MRI scan quality of tissues around metal implants is closely linked to the steadily increasing number of joint arthroplasty (especially knee and hip arthroplasties) and spinal stabilization procedures. Its unmatched soft tissue contrast and cross-sectional nature make MRI a valuable tool in early detection of frequently encountered postoperative complications, such as periprosthetic infection, material wear-induced synovitis, osteolysis, or damage of the soft tissues. However, metal-induced artifacts remain a constant challenge. Successful artifact reduction plays an important role in the diagnostic workup of patients with painful/dysfunctional arthroplasties and helps to improve patient outcome. The artifact severity depends both on the implant and the acquisition technique. The implant's material, in particular its magnetic susceptibility and electrical conductivity, its size, geometry, and orientation in the MRI magnet are critical. On the acquisition side, the magnetic field strength, the employed imaging pulse sequence, and several acquisition parameters can be optimized. As a rule of thumb, the choice of a 1.5-T over a 3.0-T magnet, a fast spin-echo sequence over a spin-echo or gradient-echo sequence, a high receive bandwidth, a small voxel size, and short tau inversion recovery-based fat suppression can mitigate the impact of metal artifacts on diagnostic image quality. However, successful imaging of large orthopedic implants (eg, arthroplasties) often requires further optimized artifact reduction methods, such as slice encoding for metal artifact correction or multiacquisition variable-resonance image combination. With these tools, MRI at 1.5 T is now widely considered the modality of choice for the clinical evaluation of patients with metal implants.
Collapse
|
15
|
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.
Collapse
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
| | | |
Collapse
|
16
|
Khodarahmi I, Rajan S, Sterling R, Koch K, Kirsch J, Fritz J. Heating of Hip Arthroplasty Implants During Metal Artifact Reduction MRI at 1.5- and 3.0-T Field Strengths. Invest Radiol 2021; 56:232-243. [PMID: 33074932 DOI: 10.1097/rli.0000000000000732] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The aim of this study was to quantify the spatial temperature rises that occur during 1.5- and 3.0-T magnetic resonance imaging (MRI) of different types of hip arthroplasty implants using different metal artifact reduction techniques. MATERIALS AND METHODS Using a prospective in vitro study design, we evaluated the spatial temperature rises of 4 different total hip arthroplasty constructs using clinical metal artifact reduction techniques including high-bandwidth turbo spin echo (HBW-TSE), slice encoding for metal artifact correction (SEMAC), and compressed sensing SEMAC at 1.5 and 3.0 T. Each MRI protocol included 6 pulse sequences, with imaging planes, parameters, and coverage identical to those in patients. Implants were immersed in standard American Society for Testing and Materials phantoms, and fiber optic sensors were used for temperature measurement. Effects of field strength, radiofrequency pulse polarization at 3.0 T, pulse protocol, and gradient coil switching on heating were assessed using nonparametric Friedman and Wilcoxon signed-rank tests. RESULTS Across all implant constructs and MRI protocols, the maximum heating at any single point reached 13.1°C at 1.5 T and 1.9°C at 3.0 T. The temperature rises at 3.0 T were similar to that of background in the absence of implants (P = 1). Higher temperature rises occurred at 1.5 T compared with 3.0 T (P < 0.0001), and circular compared with elliptical radiofrequency pulse polarization (P < 0.0001). Compressed sensing SEMAC generated equal or lower degrees of heating compared with HBW-TSE at both field strengths (P < 0.0001). CONCLUSIONS Magnetic resonance imaging of commonly used total hip arthroplasty implants is associated with variable degrees of periprosthetic tissue heating. In the absence of any perfusion effects, the maximum temperature rises fall within the physiological range at 3.0 T and within the supraphysiologic range at 1.5 T. However, with the simulation of tissue perfusion effects, the heating at 1.5 T also reduces to the upper physiologic range. Compressed sensing SEMAC metal artifact reduction MRI is not associated with higher degrees of heating than the HBW-TSE technique.
Collapse
Affiliation(s)
- Iman Khodarahmi
- From the Department of Radiology, NYU Grossman School of Medicine, New York, NY
| | - Sunder Rajan
- Division of Biomedical Physics, Office of Science and Engineering Laboratory, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring
| | - Robert Sterling
- Department of Orthopedic Surgery, John Hopkins University School of Medicine, Baltimore, MD
| | - Kevin Koch
- Department of Radiology, Medical College of Wisconsin, Milwaukee, WI
| | - John Kirsch
- Department of Radiology, Massachusetts General Hospital, Boston, MA
| | - Jan Fritz
- From the Department of Radiology, NYU Grossman School of Medicine, New York, NY
| |
Collapse
|
17
|
Reiss S, Lottner T, Ozen AC, Polei S, Bitzer A, Bock M. Analysis of the RF Excitation of Endovascular Stents in Small Gap and Overlap Scenarios Using an Electro-Optical E-field Sensor. IEEE Trans Biomed Eng 2021; 68:783-792. [DOI: 10.1109/tbme.2020.3009869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
18
|
Seo Y, Wang ZJ. Measurement and evaluation of specific absorption rate and temperature elevation caused by an artificial hip joint during MRI scanning. Sci Rep 2021; 11:1134. [PMID: 33441883 PMCID: PMC7807097 DOI: 10.1038/s41598-020-80828-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 12/21/2020] [Indexed: 11/25/2022] Open
Abstract
A primary safety concern in a magnetic resonance imaging environment is heating of metallic implants by absorbing radiofrequency (RF) energy during MRI scanning. Experimental measurement in conjunction with computational modeling was used to evaluate the risk of biological tissue injury from the RF heating of artificial hip joints by obtaining both specific absorption rate (SAR) and temperature elevation at 1.5 T and 3 T MRI systems. Simulation result showed that high SAR and high temperature appeared near both head and tail sections of the artificial hip joints. For five different 1.5 T and 3 T MRI systems, measured temperature location showed that high temperature rises occurred near both head and tail regions of the metallic hip joints. Measured SAR value of 24.6 W/kg and the high temperature rise (= 4.22 °C) occurred in the tail region of the hip joint at 1.5 T, which was higher than the limits for temperature required by the international electrotechnical commission 60601-2-33. We have demonstrated the feasibility of evaluating RF heating of metallic hip joints during MRI scans.
Collapse
Affiliation(s)
- Youngseob Seo
- Division of Chemical and Biological Metrology, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Doryong-dong, Yuseong-gu, Daejeon, 34113, Republic of Korea.
| | - Zhiyue J Wang
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Radiology, Children's Health, Dallas, TX, USA
| |
Collapse
|
19
|
Abstract
Magnetic resonance (MR) imaging relies on a strong static magnetic field in conjunction with careful orchestration of pulsed linear gradient magnetic fields and radiofrequency magnetic fields in order to generate images. The interaction of these fields with patients as well as materials with magnetic or conducting properties can be a source of risk in the MR environment. This article provides a basic review of the physical underpinnings of the primary risks in MR imaging to foster development of intuition with respect to both patient and risk management in the MR environment.
Collapse
Affiliation(s)
- Roger Jason Stafford
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Unit 1472, Houston, TX 77030, USA.
| |
Collapse
|
20
|
Xia M, Zheng J, Yang R, Song S, Xu J, Liu Q, Kainz W, Long SA, Chen J. Effects of patient orientations, landmark positions, and device positions on the MRI RF-induced heating for modular external fixation devices. Magn Reson Med 2020; 85:1669-1680. [PMID: 32970911 DOI: 10.1002/mrm.28514] [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: 04/03/2020] [Revised: 08/13/2020] [Accepted: 08/18/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE This paper studies the RF-induced heating for modular external fixation devices applied on the leg regions of the human bodies. Through numerical investigations of RF-induced heating related to different patient orientations, landmark positions, and device positions under 1.5T and 3T MRI systems, simple and practical methods to reduce RF-induced heating are recommended. METHODS Numerical simulations using a full-wave electromagnetic solver based on the finite-difference time-domain method were performed to characterize the effects of patient orientations (head-first/feet-first), landmark positions (the scanning area of the patient), and device positions (device on left or right leg) on the RF-induced heating of the external fixation devices. The G32 coil design and three anatomical human models (Duke model, Ella model, and Fats model) were adopted to model the MRI RF coil and the patients. RESULTS The relative positions of the patient, device, and coil can significantly affect the RF-induced heating. With other conditions remaining the same, changing the device position or patient orientation can lead to a peak 1-g averaged spatial absorption ratio variation of a factor around four. By changing the landmark position and the patient orientation, the RF-induced heating can be reduced from 1323.6 W/kg to 217.5 W/kg for the specific scanning situations studied. CONCLUSION Patient orientations, landmark positions, and device positions influence the RF-induced heating of modular external fixation devices at 1.5 T and 3 T. These features can be used to reduce the RF-induced heating during MRI simply and practically.
Collapse
Affiliation(s)
- Meiqi Xia
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Jianfeng Zheng
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Rui Yang
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Shuo Song
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Jian Xu
- UIH America Inc, Houston, Texas, USA
| | - Qi Liu
- UIH America Inc, Houston, Texas, USA
| | - Wolfgang Kainz
- Center for Devices and Radiological Health (CDRH), US Food and Drug Administration (FDA), Silver Spring, Maryland, USA
| | - Stuart A Long
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Ji Chen
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| |
Collapse
|
21
|
Hu Q, Yu VY, Yang Y, Hu P, Sheng K, Lee PP, Kishan AU, Raldow AC, O'Connell DP, Woods KE, Cao M. Practical Safety Considerations for Integration of Magnetic Resonance Imaging in Radiation Therapy. Pract Radiat Oncol 2020; 10:443-453. [PMID: 32781246 DOI: 10.1016/j.prro.2020.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/16/2020] [Accepted: 07/28/2020] [Indexed: 12/29/2022]
Abstract
Interest in integrating magnetic resonance imaging (MRI) in radiation therapy (RT) practice has increased dramatically in recent years owing to its unique advantages such as excellent soft tissue contrast and capability of measuring biological properties. Continuous real-time imaging for intrafractional motion tracking without ionizing radiation serves as a particularly attractive feature for applications in RT. Despite its many advantages, the integration of MRI in RT workflows is not straightforward, with many unmet needs. MR safety remains one of the key challenges and concerns in the clinical implementation of MR simulators and MR-guided radiation therapy systems in radiation oncology. Most RT staff are not accustomed to working in an environment with a strong magnetic field. There are specific requirements in RT that are different from diagnostic applications. A large variety of implants and devices used in routine RT practice do not have clear MR safety labels. RT-specific imaging pulse sequences focusing on fast acquisition, high spatial integrity, and continuous, real-time acquisition require additional MR safety testing and evaluation. This article provides an overview of MR safety tailored toward RT staff, followed by discussions on specific requirements and challenges associated with MR safety in the RT environment. Strategies and techniques for developing an MR safety program specific to RT are presented and discussed.
Collapse
Affiliation(s)
- Qiongge Hu
- Department of Radiation Oncology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Victoria Y Yu
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York
| | - Yingli Yang
- Department of Radiation Oncology, University of California, Los Angeles, California
| | - Peng Hu
- Department of Radiology, University of California, Los Angeles, California
| | - Ke Sheng
- Department of Radiation Oncology, University of California, Los Angeles, California
| | - Percy P Lee
- Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Amar U Kishan
- Department of Radiation Oncology, University of California, Los Angeles, California
| | - Ann C Raldow
- Department of Radiation Oncology, University of California, Los Angeles, California
| | - Dylan P O'Connell
- Department of Radiation Oncology, University of California, Los Angeles, California
| | - Kaley E Woods
- Department of Radiation Oncology, University of California, Los Angeles, California
| | - Minsong Cao
- Department of Radiation Oncology, University of California, Los Angeles, California.
| |
Collapse
|
22
|
|
23
|
Zheng J, Lan Q, Kainz W, Long SA, Chen J. Genetic algorithm search for the worst-case MRI RF exposure for a multiconfiguration implantable fixation system modeled using artificial neural networks. Magn Reson Med 2020; 84:2754-2764. [PMID: 32459032 DOI: 10.1002/mrm.28319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 03/20/2020] [Accepted: 04/21/2020] [Indexed: 11/09/2022]
Abstract
PURPOSE This paper presents a method to search for the worst-case configuration leading to the highest RF exposure for a multiconfiguration implantable fixation system under MRI. METHODS A two-step method combining an artificial neural network and a genetic algorithm is developed to achieve this purpose. In the first step, the level of RF exposure in terms of peak 1-g and/or 10-g averaged specific absorption rate (SAR1g/10g ), related to the multiconfiguration system, is predicted using an artificial neural network. A genetic algorithm is then used to search for the worst-case configuration of this multidimensional nonlinear problem within both the enumerated discrete sample space and generalized continuous sample space. As an example, a generic plate system with a total of 576 configurations is used for both 1.5T and 3T MRI systems. RESULTS The presented method can effectively identify the worst-case configuration and accurately predict the SAR1g/10g with no more than 20% of the samples in the studied discrete sample space, and can even predict the worst case in the generalized continuous sample space. The worst-case prediction error in the generalized continuous sample space is less than 1.6% for SAR1g and less than 1.3% for SAR10g compared with the simulation results. CONCLUSION The combination of an artificial neural network with genetic algorithm is a robust technique to determine the worst-case RF exposure level for a multiconfiguration system, and only needs a small amount of training data from the entire system.
Collapse
Affiliation(s)
- Jianfeng Zheng
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Qianlong Lan
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Wolfgang Kainz
- Center for Devices and Radiological Health, Food and Drug Administration, Rockville, Maryland, USA
| | - Stuart A Long
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| | - Ji Chen
- Department of Electrical and Computer Engineering, University of Houston, Houston, Texas, USA
| |
Collapse
|
24
|
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
| |
Collapse
|
25
|
Arduino A, Bottauscio O, Brühl R, Chiampi M, Zilberti L. In silico evaluation of the thermal stress induced by MRI switched gradient fields in patients with metallic hip implant. ACTA ACUST UNITED AC 2019; 64:245006. [DOI: 10.1088/1361-6560/ab5428] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
26
|
Noureddine Y, Kraff O, Ladd ME, Wrede K, Chen B, Quick HH, Schaefers G, Bitz AK. Radiofrequency induced heating around aneurysm clips using a generic birdcage head coil at 7 Tesla under consideration of the minimum distance to decouple multiple aneurysm clips. Magn Reson Med 2019; 82:1859-1875. [DOI: 10.1002/mrm.27835] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 05/08/2019] [Accepted: 05/10/2019] [Indexed: 12/13/2022]
Affiliation(s)
- Yacine Noureddine
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg‐Essen Essen Germany
- MR:comp GmbH, MR Safety Testing Laboratory Gelsenkirchen Germany
| | - Oliver Kraff
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg‐Essen Essen Germany
| | - Mark E. Ladd
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg‐Essen Essen Germany
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ) Heidelberg Germany
- Faculty of Physics and Astronomy and Faculty of Medicine University of Heidelberg Heidelberg Germany
| | - Karsten Wrede
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg‐Essen Essen Germany
- Department of Neurosurgery University Hospital Essen Essen Germany
| | - Bixia Chen
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg‐Essen Essen Germany
- Department of Neurosurgery University Hospital Essen Essen Germany
| | - Harald H. Quick
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg‐Essen Essen Germany
- High Field and Hybrid MR, University Hospital Essen Essen Germany
| | - Gregor Schaefers
- MR:comp GmbH, MR Safety Testing Laboratory Gelsenkirchen Germany
- MRI‐STaR – Magnetic Resonance Institute for Safety, Technology and Research GmbH Gelsenkirchen Germany
| | - Andreas K. Bitz
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ) Heidelberg Germany
- Faculty of Electrical Engineering and Information Technology FH Aachen University of Applied Sciences Aachen NRW Germany
| |
Collapse
|
27
|
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.
Collapse
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
| |
Collapse
|
28
|
Fujimoto K, Angelone LM, Lucano E, Rajan SS, Iacono MI. Radio-Frequency Safety Assessment of Stents in Blood Vessels During Magnetic Resonance Imaging. Front Physiol 2018; 9:1439. [PMID: 30459628 PMCID: PMC6232906 DOI: 10.3389/fphys.2018.01439] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 09/21/2018] [Indexed: 01/03/2023] Open
Abstract
Purpose: The purpose of this study was to investigate the need for high-resolution detailed anatomical modeling to correctly estimate radio-frequency (RF) safety during magnetic resonance imaging (MRI). RF-induced heating near metallic implanted devices depends on the electric field tangential to the device (Etan). Etan and specific absorption rate (SAR) were analyzed in blood vessels of an anatomical model to understand if a standard gel phantom accurately represents the potential heating in tissues due to passive vascular implants such as stents. Methods: A numerical model of an RF birdcage body coil and an anatomically realistic virtual patient with a native spatial resolution of 1 mm3 were used to simulate the in vivo electric field at 64 MHz (1.5 T MRI system). Maximum values of SAR inside the blood vessels were calculated and compared with peaks in a numerical model of the ASTM gel phantom to see if the results from the simplified and homogeneous gel phantom were comparable to the results from the anatomical model. Etan values were also calculated in selected stent trajectories inside blood vessels and compared with the ASTM result. Results: Peak SAR values in blood vessels were up to ten times higher than those found in the ASTM standard gel phantom. Peaks were found in clinically significant anatomical locations, where stents are implanted as per intended use. Furthermore, Etan results showed that volume-averaged SAR values might not be sufficient to assess RF safety. Conclusion: Computational modeling with a high-resolution anatomical model indicated higher values of the incident electric field compared to the standard testing approach. Further investigation will help develop a robust safety testing method which reflects clinically realistic conditions.
Collapse
Affiliation(s)
- Kyoko Fujimoto
- Division of Biomedical Physics, Office of Science and Engineering Laboratory, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Leonardo M Angelone
- Division of Biomedical Physics, Office of Science and Engineering Laboratory, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Elena Lucano
- Division of Biomedical Physics, Office of Science and Engineering Laboratory, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Sunder S Rajan
- Division of Biomedical Physics, Office of Science and Engineering Laboratory, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States
| | - Maria Ida Iacono
- Division of Biomedical Physics, Office of Science and Engineering Laboratory, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States
| |
Collapse
|