51
|
Simonis FFJ, Petersen ET, Lagendijk JJW, van den Berg CAT. Feasibility of measuring thermoregulation during RF heating of the human calf muscle using MR based methods. Magn Reson Med 2015; 75:1743-51. [PMID: 25977138 DOI: 10.1002/mrm.25710] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 02/04/2015] [Accepted: 03/09/2015] [Indexed: 11/06/2022]
Abstract
PURPOSE One of the main safety concerns in MR is heating of the subject due to radiofrequency (RF) exposure. Recently was shown that local peak temperatures can reach dangerous values and the most prominent parameter for accurate temperature estimations is thermoregulation. Therefore, the goal of this research is testing the feasibility of measuring thermoregulation in vivo using MR methods. THEORY AND METHODS The calves of 13 volunteers were scanned at 3 tesla. A Proton Resonance Frequency Shift method was used for temperature measurement. Arterial Spin Labeling and phase contrast scans were used for perfusion and flow measurements respectively. The calves were monitored during extreme RF exposure (20 W/kg, 16 min) and after physical exercise. RESULTS Temperature increases due to RF absorption (range of the 90th percentile of all volunteers: 1.1-2.5°C) matched with the reference skin temperature changes. Increases in perfusion and flow were defined on the whole leg and normalized to baseline. Perfusion showed a significant increase due to RF heating (ratio compared with baseline: 1.28 ± 0.37; P < 0.05), the influence of exercise was much greater, however (2.97 ± 2.45, P < 0.01). CONCLUSION This study represents a first exploration of measuring thermoregulation, which will become essential when new safety guidelines are based on thermal dose.
Collapse
Affiliation(s)
- Frank F J Simonis
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Esben T Petersen
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jan J W Lagendijk
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Cornelis A T van den Berg
- Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands
| |
Collapse
|
52
|
Tocchio S, Kline-Fath B, Kanal E, Schmithorst VJ, Panigrahy A. MRI evaluation and safety in the developing brain. Semin Perinatol 2015; 39:73-104. [PMID: 25743582 PMCID: PMC4380813 DOI: 10.1053/j.semperi.2015.01.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility-weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5-T and 3-T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges, and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, and sedation considerations, and a discussion of current technologies such as MRI conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners.
Collapse
Affiliation(s)
- Shannon Tocchio
- Pediatric Imaging Research Center, Department of Radiology Children’s Hospital of Pittsburgh of UPMC, Pittsburgh, PA University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Beth Kline-Fath
- Department of Radiology Cincinnati Children’s Hospital Medical Center, Cincinnati, OH
| | - Emanuel Kanal
- Director, Magnetic Resonance Services; Professor of Neuroradiology; Department of Radiology, University of Pittsburgh Medical Center (UPMC)
| | - Vincent J. Schmithorst
- Pediatric Imaging Research Center, Department of Radiology Children’s Hospital of Pittsburgh of UPMC, Pittsburgh, PA University of Pittsburgh Medical Center, Pittsburgh, PA
| | - Ashok Panigrahy
- Pediatric Imaging Research Center, Department of Radiology Children׳s Hospital of Pittsburgh of UPMC, University of Pittsburgh Medical Center, Pittsburgh, PA.
| |
Collapse
|
53
|
Malik SJ, Beqiri A, Price AN, Teixeira JN, Hand JW, Hajnal JV. Specific absorption rate in neonates undergoing magnetic resonance procedures at 1.5 T and 3 T. NMR IN BIOMEDICINE 2015; 28:344-52. [PMID: 25594939 PMCID: PMC5053241 DOI: 10.1002/nbm.3256] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 12/01/2014] [Accepted: 12/09/2014] [Indexed: 05/24/2023]
Abstract
MRI is finding increased clinical use in neonatal populations; the extent to which electromagnetic models used for quantification of specific absorption rate (SAR) by commercial MRI scanners accurately reflect this alternative scenario is unclear. This study investigates how SAR predictions relating to adults can be related to neonates under differing conditions when imaged using 1.5 T and 3 T MRI scanners. Electromagnetic simulations were produced in neonatal subjects of different sizes and positions within a generic MRI body transmit device operating at both 64 MHz and 128 MHz, corresponding to 1.5 T and 3 T MRI scanners, respectively. An adult model was also simulated, as was a spherical salt-water phantom, which was also used in a calorimetry experiment. The SAR in neonatal subjects was found to be less than that experienced in an adult in all scenarios; however, the overestimation factor was variable. For example a 3 T body scan resulting in local 10 g SAR of 10.1 W kg(-1) in an adult would deposit 2.6 W kg(-1) in a neonate: an approximately fourfold difference. The SAR experienced by neonatal subjects undergoing MRI is lower than that in adults in equivalent situations. If the safety of such procedures is assessed using adult-appropriate models then the result is a conservative estimate.
Collapse
Affiliation(s)
- Shaihan J Malik
- Centre for the Developing Brain and Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St Thomas' Hospital, London, UK
| | | | | | | | | | | |
Collapse
|
54
|
Abstract
Electroencephalography (EEG) has been used to study and characterize epilepsy for decades, but has a limited ability to localize epileptiform activity to a specific brain region. With recent technological advances, high-quality EEG can now be recorded during functional magnetic resonance imaging (fMRI), which characterizes brain activity through local changes in blood oxygenation. By combining these techniques, the specific timing of interictal events can be identified on the EEG at millisecond resolution and spatially localized with fMRI at millimeter resolution. As a result, simultaneous EEG-fMRI provides the opportunity to better investigate the spatiotemporal mechanisms of the generation of epileptiform activity in the brain. This article discusses the technical considerations and their solutions for recording simultaneous EEG-fMRI and the results of studies to date. It also addresses the application of EEG-fMRI to epilepsy in humans, including clinical applications and ongoing challenges.
Collapse
|
55
|
Seven-Tesla Magnetic Resonance Imaging of Atherosclerotic Plaque in the Significantly Stenosed Carotid Artery. Invest Radiol 2014; 49:749-57. [DOI: 10.1097/rli.0000000000000079] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
56
|
Shrivastava D, Utecht L, Tian J, Hughes J, Vaughan JT. In vivo radiofrequency heating in swine in a 3T (123.2-MHz) birdcage whole body coil. Magn Reson Med 2014; 72:1141-50. [PMID: 24259413 PMCID: PMC4041852 DOI: 10.1002/mrm.24999] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 09/05/2013] [Accepted: 09/23/2013] [Indexed: 02/01/2023]
Abstract
PURPOSE To study in vivo radiofrequency (RF) heating produced due to power deposition from a 3T (Larmour frequency = 123.2 MHz), birdcage, whole body coil. METHODS The RF heating was simulated in a digital swine by solving the mechanistic generic bioheat transfer model (GBHTM) and the conventional, empirical Pennes bioheat transfer equation for two cases: 1) when the swine head was in the isocenter and 2) when the swine trunk was in the isocenter. The simulation results were validated by making direct fluoroptic temperature measurements in the skin, brain, simulated hot regions, and rectum of 10 swine (case 1: n = 5, mean animal weight = 84.03 ± 6.85 kg, whole body average SAR = 2.65 ± 0.22 W/kg; case 2: n = 5, mean animal weight = 81.59 ± 6.23 kg, whole body average SAR = 2.77 ± 0.26 W/kg) during 1 h of exposure to a turbo spin echo sequence. RESULTS The GBHTM simulated the RF heating more accurately compared with the Pennes equation. In vivo temperatures exceeded safe temperature thresholds with allowable SAR exposures. Hot regions may be produced deep inside the body, away from the skin. CONCLUSION SAR exposures that produce safe temperature thresholds need reinvestigation.
Collapse
Affiliation(s)
- Devashish Shrivastava
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | | | | | | | | |
Collapse
|
57
|
Konkle JJ, Goodwill PW, Saritas EU, Zheng B, Lu K, Conolly SM. Twenty-fold acceleration of 3D projection reconstruction MPI. ACTA ACUST UNITED AC 2014; 58:565-76. [PMID: 23940058 DOI: 10.1515/bmt-2012-0062] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 07/08/2013] [Indexed: 01/27/2023]
Abstract
We experimentally demonstrate a 20-fold improvement in acquisition time in projection reconstruction (PR) magnetic particle imaging (MPI) relative to the state-of-the-art PR MPI imaging results. We achieve this acceleration in our imaging system by introducing an additional Helmholtz electromagnet pair, which creates a slow shift (focus) field. Because of magnetostimulation limits in humans, we show that scan time with three-dimensional (3D) PR MPI is theoretically within the same order of magnitude as 3D MPI with a field free point; however, PR MPI has an order of magnitude signal-to-noise ratio gain.
Collapse
|
58
|
Guidelines for limiting exposure to electric fields induced by movement of the human body in a static magnetic field and by time-varying magnetic fields below 1 Hz. HEALTH PHYSICS 2014; 106:418-425. [PMID: 25208018 DOI: 10.1097/hp.0b013e31829e5580] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
|
59
|
Koning W, de Rotte AA, Bluemink JJ, van der Velden TA, Luijten PR, Klomp DW, Zwanenburg JJ. MRI of the carotid artery at 7 Tesla: Quantitative comparison with 3 Tesla. J Magn Reson Imaging 2014; 41:773-80. [DOI: 10.1002/jmri.24601] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 01/25/2014] [Indexed: 11/11/2022] Open
Affiliation(s)
- Wouter Koning
- Department of Radiology; UMC Utrecht; The Netherlands
| | | | | | | | | | | | | |
Collapse
|
60
|
Shahin S, Mishra V, Singh SP, Chaturvedi CM. 2.45-GHz microwave irradiation adversely affects reproductive function in male mouse,Mus musculusby inducing oxidative and nitrosative stress. Free Radic Res 2014; 48:511-25. [DOI: 10.3109/10715762.2014.888717] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
61
|
White MJ, Thornton JS, Hawkes DJ, Hill DL, Kitchen N, Mancini L, McEvoy AW, Razavi R, Wilson S, Yousry T, Keevil SF. Design, Operation, and Safety of Single-Room Interventional MRI Suites: Practical Experience From Two Centers. J Magn Reson Imaging 2014; 41:34-43. [DOI: 10.1002/jmri.24577] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 01/10/2014] [Indexed: 11/06/2022] Open
Affiliation(s)
- Mark J. White
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
- UCL Institute of Neurology; Queen Square, London UK
| | - John S. Thornton
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
- UCL Institute of Neurology; Queen Square, London UK
| | | | | | - Neil Kitchen
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
- UCL Institute of Neurology; Queen Square, London UK
| | - Laura Mancini
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
- UCL Institute of Neurology; Queen Square, London UK
| | - Andrew W. McEvoy
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
- UCL Institute of Neurology; Queen Square, London UK
| | | | - Sally Wilson
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
| | - Tarek Yousry
- National Hospital for Neurology and Neurosurgery; Queen Square, London UK
- UCL Institute of Neurology; Queen Square, London UK
| | | |
Collapse
|
62
|
Carrio I, Ros P. Risks and Safety Aspects of MR-PET. PET/MRI 2014. [PMCID: PMC7122917 DOI: 10.1007/978-3-642-40692-8_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The introduction of MR-PET systems into medical practice not only may lead to a gain in clinical diagnosis as compared to PET-CT imaging due to the superior soft tissue contrast of the MR technology but can also substantially reduce exposure of patients to ionizing radiation. On the other hand, there are also risks and health effects associated with the use of diagnostic MR devices that have to be considered carefully. In this chapter, the biophysical and biological aspects relevant for the assessment of health effects related to the use of ionizing radiation in PET and (electro)magnetic fields in MR are summarized. On this basis, the current safety standards will be presented – which, however, do not address the possibility of synergistic effects of ionizing radiation and (electro)magnetic fields. In the light of the developing MR-PET technology, it is of utmost importance to investigate this aspect in more detail for exposure levels that will occur at MR-PET systems. Finally, some considerations concerning the justification and optimization of MR-PET examination will be made.
Collapse
Affiliation(s)
- Ignasi Carrio
- Depto. Medicina Nuclear, Autonomous University of Barcelona Hospital Sant Pau, Barcelona, Spain
| | - Pablo Ros
- Department of Radiology, University Hospitals Case Medical Center, Cleveland, Ohio USA
| |
Collapse
|
63
|
Acri G, Testagrossa B, Causa F, Tripepi MG, Vermiglio G, Novario R, Pozzi L, Quadrelli G. Evaluation of occupational exposure in magnetic resonance sites. Radiol Med 2013; 119:208-13. [PMID: 24337753 DOI: 10.1007/s11547-013-0324-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 10/22/2012] [Indexed: 11/30/2022]
Abstract
PURPOSE In an attempt to evaluate the exposure level of magnetic resonance imaging (MRI) workers to static magnetic fields, the isotropic magnetic flux density values were integrated over time to produce the cumulative exposure. To protect occupational staff a further precautionary step is proposed by introducing a weighting function incorporating the limits imposed by the Italian legislation. The results obtained should be reported, at the end of each working day, on a special dose card, in order to record each worker's exposure to the static magnetic field. Moreover, this dose card could be an important tool if long-term effects occur because it provides a complete history of the occupational exposure in an MRI site. MATERIALS AND METHODS To conduct measurements, three Hall-sensor probes were used. The consistency of experimental data, tools and methodologies used was evaluated by performing the Kruskal-Wallis test. Finally, the weighted magnitude of the magnetic flux density was integrated over time to obtain global exposure. RESULTS Measurements were performed on different MRI scanners ranging from 0.25 up to 3.0 T. The results obtained were compared with the 200 mT·h, which represents the upper limit of the Italian regulation. In no case was the 200 mT·h per day exposure exceeded: however, when the strength of the magnetic field was >200 mT the weighted function overestimated the exposure, so that it represents a highly precautionary measure taking into account possible acute and long-term effects. In addition, from the data recorded during patient positioning operations by MRI staff the dB/dt curve was obtained. CONCLUSIONS The areas obtained from the integral of the weighted static magnetic field strength over time can be indicative of the global exposure of the occupational staff. These values should be reported on a special dose card that could be considered as an important tool if long-term effects occur because it provides a complete history of the occupational exposure in an MRI site.
Collapse
Affiliation(s)
- Giuseppe Acri
- S.A.S.T.A.S Department-Section of Protezionistica A.S.S.I, University of Messina, Viale Gazzi-Policlinico Universitario, Torre Biologica, 98125, Messina, Italy,
| | | | | | | | | | | | | | | |
Collapse
|
64
|
Liu L, Trakic A, Sanchez-Lopez H, Liu F, Crozier S. An analysis of the gradient-induced electric fields and current densities in human models when situated in a hybrid MRI-LINAC system. Phys Med Biol 2013; 59:233-45. [DOI: 10.1088/0031-9155/59/1/233] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
65
|
Guibelalde del Castillo E. [Patient exposure to electromagnetic fields in magnetic resonance scanners: a review]. RADIOLOGIA 2013; 55 Suppl 2:2-8. [PMID: 24246885 DOI: 10.1016/j.rx.2013.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 09/11/2013] [Accepted: 09/21/2013] [Indexed: 11/16/2022]
Abstract
The use of non-ionizing electromagnetic fields in the low frequency end of the electromagnetic spectrum and static fields, radiofrequencies (RF), and microwaves is fundamental both in modern communication systems and in diagnostic medical imaging techniques like magnetic resonance imaging (MRI). The proliferation of these applications in recent decades has led to intense activity in developing regulations to guarantee their safety and to the establishment of guidelines and legal recommendations for the public, workers, and patients. In April 2012 it was foreseen that the European Parliament and Council would approve and publish a directive on the minimum health and safety requirements regarding the exposure of workers to the risks arising from electromagnetic fields, which would modify Directive 2004/40/EC. New studies related to the exposure to electromagnetic radiation and its impact on health published in recent years have led to a new postponement, and it is now foreseen that the directive will come into effect in October 2013. One of the most noteworthy aspects of the new version of the directive is the exclusion of the limits of occupational exposure to electromagnetic fields in the clinical use of MRI. In exchange for this exception, physicians and experts in protection against non-ionizing radiation are asked to make additional efforts to train workers exposed to non-ionizing radiation and to establish mechanisms to guarantee the correct application of non-ionizing electromagnetic fields in patients, along similar lines to the principles of justification and optimization established for ionizing radiation. On the basis of the most recently published studies, this article reviews some safety-related aspects to take into account when examining patients with MRI with high magnetic fields.
Collapse
Affiliation(s)
- E Guibelalde del Castillo
- Departamento de Radiología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, España.
| |
Collapse
|
66
|
Wolska-Krawczyk M, Rube MA, Immel E, Melzer A, Buecker A. Heating and safety of a new MR-compatible guidewire prototype versus a standard nitinol guidewire. Radiol Phys Technol 2013; 7:95-101. [PMID: 24203851 DOI: 10.1007/s12194-013-0236-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 10/02/2013] [Accepted: 10/03/2013] [Indexed: 11/27/2022]
Abstract
Our purpose in this study was to examine heating of nitinol and polyetheretherketone (PEEK) guidewires during near-real-time MR imaging in an artificial vascular model an "aorta phantom". The first 100 cm of the nitinol- and PEEK-based guidewires both 145 × 0.08 cm were immersed in a saline-filled aorta phantom. The probes of a fiber-optic thermometer were positioned at the tips of both wires. Balanced steady-state free precession (bSSFP) [TE 1.6 ms; TR 3.5 ms; flip angle (FA) 60°; field of view (FOV) 40 cm; matrix 256 × 256; specific absorption rate (SAR); 1.15 Watt (W)/kg] and spoiled gradient-echo (SPGR) (TE 1.8 ms; TR 60 ms; FA 60°; FOV 40 cm; matrix 256 × 256; SAR 1.15 W/kg) pulse sequences were acquired in a 1.5-T MR scanner with use of an 8-channel array coil. Temperatures were recorded while the phantom was placed centrally in the bore of a MR scanner and in an off-center position (x = 24 cm, y = -5 cm, z = -10/10 cm). The temperature of the nitinol guidewire increased by 0.3 °C (center) and 1.1 °C (off-center position) with use of the bSSFP and by 9.6 and 13 °C (off-center position) with use of the SPGR sequence. Only minor temperature changes up to a maximum of 0.4 °C were observed with the MR-compatible PEEK guidewire when any position or sequence was applied. The PEEK guidewire showed substantially lower heating as compared to the nitinol guidewire in near-real-time imaging sequences in a phantom.
Collapse
|
67
|
Sienkiewicz Z. International Workshop on Non-Ionizing Radiation Protection in Medicine. Med Phys 2013; 40:117001. [DOI: 10.1118/1.4824921] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
68
|
Abstract
Ultrasound remains the modality of choice in imaging the fetus due to its availability, safety, and low cost. With advances in technology, however, magnetic resonance imaging (MRI) has become an important adjuvant in the evaluation of the fetus. MRI is not limited by fetal lie, oligohydramnios, overlying bone, or obesity. MRI can image the fetus in any plane, providing a large field of view of the fetus and placenta with excellent soft tissue resolution of the brain, airway, lungs, and abdomen. Advanced techniques are being developed that provide volumetric data, spectroscopy, and functional images. MRI has its own set of challenges with a lack of consensus regarding its utility and safety. Artifact from the moving fetus and breathing mother limits the sequences available. While there is currently no evidence that fetal MRI produces harmful effects, long-term safety regarding radiofrequency fields and the loud acoustic environment continues to be studied. In this review, the benefits and potential risks of fetal MRI will be discussed.
Collapse
Affiliation(s)
- Dorothy Bulas
- Department of Diagnostic Imaging and Radiology, Children's National Medical Center, 111 Michigan Ave NW, Washington, DC 20010.
| | | |
Collapse
|
69
|
Arteaga de Castro CS, Boer VO, Andreychenko A, Wijnen JP, van der Heide UA, Luijten PR, Klomp DWJ. Improved efficiency on editing MRS of lactate and γ-aminobutyric acid by inclusion of frequency offset corrected inversion pulses at high fields. NMR IN BIOMEDICINE 2013; 26:1213-1219. [PMID: 23508792 DOI: 10.1002/nbm.2937] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 02/06/2013] [Accepted: 02/07/2013] [Indexed: 06/01/2023]
Abstract
γ-Aminobutyric acid (GABA) and lactate are metabolites which are present in the brain. These metabolites can be indicators of psychiatric disorders or tumor hypoxia, respectively. The measurement of these weakly coupled spin systems can be performed using MRS editing techniques; however, at high field strength, this can be challenging. This is due to the low available B1 (+) field at high fields, which results in narrow-bandwidth refocusing pulses and, consequently, in large chemical shift displacement artifacts. In addition, as a result of the increased chemical shift displacement artifacts and chemical shift dispersion, the efficiency of the MRS method is reduced, even when using adiabatic refocusing pulses. To overcome this limitation, frequency offset corrected inversion (FOCI) pulses have been suggested as a mean to substantially increase the bandwidth of adiabatic pulses. In this study, a Mescher-Garwood semi-localization by adiabatic selection and refocusing (MEGA-sLASER) editing sequence with refocusing FOCI pulses is presented for the measurement of GABA and lactate in the human brain. Metabolite detection efficiencies were improved by 20% and 75% for GABA and lactate, respectively, when compared with editing techniques that employ adiabatic radiofrequency refocusing pulses. The highly efficient MEGA-sLASER sequence with refocusing FOCI pulses is an ideal and robust MRS editing technique for the measurement of weakly coupled metabolites at high field strengths.
Collapse
|
70
|
Abstract
Magnetic resonance imaging (MRI) has been used to image the in utero fetus for the past 3 decades. Although not as commonplace as other patient-oriented MRI, it is a growing field and demonstrating a role in the clinical care of the fetus. Indeed, the body of literature involving fetal MRI exceeds 3000 published articles. Indeed, there is interest in accessing even the healthy fetus with MRI to further understand the development of humans during the fetal stage. On the horizon is fetal imaging using 3.0-T clinical systems. Although a clear path is not necessarily determined, experiments, theoretical calculations, advances in pulse sequence design, new hardware, and experience from imaging at 1.5 T help define the path.
Collapse
Affiliation(s)
- Robert C Welsh
- Department of Radiology, University of Michigan, Ann Arbor, MI 48109-5667, USA.
| | | | | |
Collapse
|
71
|
Saritas EU, Goodwill PW, Zhang GZ, Conolly SM. Magnetostimulation limits in magnetic particle imaging. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:1600-1610. [PMID: 23649181 DOI: 10.1109/tmi.2013.2260764] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
For magnetic particle imaging (MPI), specific absorption rate (SAR) and more critically magnetostimulation (i.e., dB/dt) safety limits will determine the optimal scan parameters, such as the drive field strength and frequency. These parameters will impact the scanning speed, field-of-view (FOV) and signal-to-noise ratio in MPI. Understanding the potential safety hazards of the drive field is critical for scaling MPI for human use. In this work, we demonstrate that magnetostimulation is the primary magnetic safety consideration in MPI, and we describe the first human-subject magnetostimulation threshold experiments for MPI using homogeneous coils. Our experiments, performed on the arm and leg, indicate that magnetostimulation thresholds monotonically decrease with increasing frequency. Additionally, we show for the first time that a strong inverse correlation exists between the threshold and the body part size. The chronaxie time, on the other hand, did not vary with body part size. We conclude with an estimation of the magnetostimulation thresholds for a full-body MPI scanner: a mean asymptotic threshold of 14.3 mT-pp (peak-to-peak) with a mean chronaxie time of 289 μs, which correspond to a magnetostimulation threshold of about 15 mT-pp for frequencies between 25 and 50 kHz. These findings will have a great impact on the optimization of MPI parameters, especially in determining the number of partial FOVs required to cover a region of interest.
Collapse
Affiliation(s)
- Emine U Saritas
- Department of Bioengineering, University of California, Berkeley, CA 94720, USA.
| | | | | | | |
Collapse
|
72
|
Fiechter M, Stehli J, Fuchs TA, Dougoud S, Gaemperli O, Kaufmann PA. Impact of cardiac magnetic resonance imaging on human lymphocyte DNA integrity. Eur Heart J 2013; 34:2340-5. [PMID: 23793096 PMCID: PMC3736059 DOI: 10.1093/eurheartj/eht184] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/23/2013] [Accepted: 05/08/2013] [Indexed: 11/14/2022] Open
Abstract
AIMS Magnetic resonance (MR) imaging is widely used for diagnostic imaging in medicine as it is considered a safe alternative to ionizing radiation-based techniques. Recent reports on potential genotoxic effects of strong and fast switching electromagnetic gradients such as used in cardiac MR (CMR) have raised safety concerns. The aim of this study was to analyse DNA double-strand breaks (DSBs) in human blood lymphocytes before and after CMR examination. METHODS AND RESULTS In 20 prospectively enrolled patients, peripheral venous blood was drawn before and after 1.5 T CMR scanning. After density gradient cell separation of blood samples, DNA DSBs in lymphocytes were quantified using immunofluorescence microscopy and flow cytometric analysis. Wilcoxon signed-rank testing was used for statistical analysis. Immunofluorescence microscopic and flow cytometric analysis revealed a significant increase in median numbers of DNA DSBs in lymphocytes induced by routine 1.5 T CMR examination. CONCLUSION The present findings indicate that CMR should be used with caution and that similar restrictions may apply as for X-ray-based and nuclear imaging techniques in order to avoid unnecessary damage of DNA integrity with potential carcinogenic effect.
Collapse
Affiliation(s)
- Michael Fiechter
- Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, Zurich CH-8091, Switzerland
- Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Julia Stehli
- Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, Zurich CH-8091, Switzerland
| | - Tobias A. Fuchs
- Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, Zurich CH-8091, Switzerland
| | - Svetlana Dougoud
- Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, Zurich CH-8091, Switzerland
| | - Oliver Gaemperli
- Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, Zurich CH-8091, Switzerland
| | - Philipp A. Kaufmann
- Department of Radiology, Cardiac Imaging, University Hospital Zurich, Ramistrasse 100, NUK C 42, Zurich CH-8091, Switzerland
- Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| |
Collapse
|
73
|
Zhadobov M, Ferrand G, Luong M, Soubere Y, Le Quément C, Carton PH, Piret Y, Sauleau R, Le Dréan Y. Exposure system and dosimetry for in vitro studies of biocompatibility of pulse-modulated RF signals of ultrahigh field MRI. IEEE Trans Biomed Eng 2013; 60:3167-75. [PMID: 23799680 DOI: 10.1109/tbme.2013.2270371] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A new setup for exposure of human cells in vitro at 37 °C to pulse-modulated 300 and 500 MHz signals of future magnetic resonance imaging (MRI) systems is designed, built up, and characterized. Two dipole antennas, specifically designed for ultrahigh field MRI, are used as radiating structures. The electromagnetic (EM) field distribution inside the incubator containing the cells is computed, and it is shown to be in a good agreement with measurements. The electric field at the cell level is quantified numerically. Local, 1-g average, and averaged over the culture medium volume SAR are provided along with the standard deviation values for each well. Temperature increments are measured inside the culture medium during the exposure using an optical fiber thermometer. Then, we identify the pulse parameters corresponding to the thermal threshold of 1 °C, usually considered as a threshold for thermally induced biological effects. For these parameters, the induction of heat shock proteins is assessed to biologically verify a potential thermal response of cells. The data demonstrate that, under the considered experimental conditions, exposure to pulse-modulated radiations emulating typical ultrahigh field MRI signals, corresponding to temperature increments below 1 °C, does not trigger any heat shock response in human brain cells.
Collapse
|
74
|
Yahya A, De Zanche N, Allen PS. A dual-tuned transceive resonator for (13) C{(1) H} MRS: two open coils in one. NMR IN BIOMEDICINE 2013; 26:533-541. [PMID: 23401299 DOI: 10.1002/nbm.2890] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 10/01/2012] [Accepted: 10/18/2012] [Indexed: 06/01/2023]
Abstract
Proton-decoupled, (13) C nuclear MRS experiments require a RF coil that operates at the Larmor frequencies of both (13) C and (1) H. In this work, we designed, built and tested a single-unit, dual-tuned coil based on a half-birdcage open coil design. It was constructed as a low-pass network with a resonant trap in series with each leg. Traps are tuned in alternate legs such that the two resonant modes arise from currents on alternate legs. The coil performance was compared with that of a dual-tuned coil consisting of two proton surface coils operating in quadrature and a single surface coil for (13) C transmission and reception. The half-birdcage coil was shown to produce a more homogeneous RF field at each frequency and was more sensitive to a (13) C signal arising from regions further from the coil surface. The applicability of the coil in vivo was demonstrated by acquiring a proton decoupled, natural abundance (13) C glycogen signal from the calf of a normal volunteer.
Collapse
Affiliation(s)
- Atiyah Yahya
- Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
| | | | | |
Collapse
|
75
|
Saritas EU, Goodwill PW, Croft LR, Konkle JJ, Lu K, Zheng B, Conolly SM. Magnetic particle imaging (MPI) for NMR and MRI researchers. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 229:116-26. [PMID: 23305842 PMCID: PMC3602323 DOI: 10.1016/j.jmr.2012.11.029] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 11/21/2012] [Accepted: 11/30/2012] [Indexed: 05/04/2023]
Abstract
Magnetic Particle Imaging (MPI) is a new tracer imaging modality that is gaining significant interest from NMR and MRI researchers. While the physics of MPI differ substantially from MRI, it employs hardware and imaging concepts that are familiar to MRI researchers, such as magnetic excitation and detection, pulse sequences, and relaxation effects. Furthermore, MPI employs the same superparamagnetic iron oxide (SPIO) contrast agents that are sometimes used for MR angiography and are often used for MRI cell tracking studies. These SPIOs are much safer for humans than iodine or gadolinium, especially for Chronic Kidney Disease (CKD) patients. The weak kidneys of CKD patients cannot safely excrete iodine or gadolinium, leading to increased morbidity and mortality after iodinated X-ray or CT angiograms, or after gadolinium-MRA studies. Iron oxides, on the other hand, are processed in the liver, and have been shown to be safe even for CKD patients. Unlike the "black blood" contrast generated by SPIOs in MRI due to increased T2* dephasing, SPIOs in MPI generate positive, "bright blood" contrast. With this ideal contrast, even prototype MPI scanners can already achieve fast, high-sensitivity, and high-contrast angiograms with millimeter-scale resolutions in phantoms and in animals. Moreover, MPI shows great potential for an exciting array of applications, including stem cell tracking in vivo, first-pass contrast studies to diagnose or stage cancer, and inflammation imaging in vivo. So far, only a handful of prototype small-animal MPI scanners have been constructed worldwide. Hence, MPI is open to great advances, especially in hardware, pulse sequence, and nanoparticle improvements, with the potential to revolutionize the biomedical imaging field.
Collapse
Affiliation(s)
- Emine U Saritas
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720-1762, USA.
| | | | | | | | | | | | | |
Collapse
|
76
|
Niendorf T, Graessl A, Thalhammer C, Dieringer MA, Kraus O, Santoro D, Fuchs K, Hezel F, Waiczies S, Ittermann B, Winter L. Progress and promises of human cardiac magnetic resonance at ultrahigh fields: a physics perspective. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 229:208-22. [PMID: 23290625 DOI: 10.1016/j.jmr.2012.11.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Revised: 11/16/2012] [Accepted: 11/16/2012] [Indexed: 05/12/2023]
Abstract
A growing number of reports eloquently speak about explorations into cardiac magnetic resonance (CMR) at ultrahigh magnetic fields (B0≥7.0 T). Realizing the progress, promises and challenges of ultrahigh field (UHF) CMR this perspective outlines current trends in enabling MR technology tailored for cardiac MR in the short wavelength regime. For this purpose many channel radiofrequency (RF) technology concepts are outlined. Basic principles of mapping and shimming of transmission fields including RF power deposition considerations are presented. Explorations motivated by the safe operation of UHF-CMR even in the presence of conductive implants are described together with the physics, numerical simulations and experiments, all of which detailing antenna effects and RF heating induced by intracoronary stents at 7.0 T. Early applications of CMR at 7.0 T and their clinical implications for explorations into cardiovascular diseases are explored including assessment of cardiac function, myocardial tissue characterization, MR angiography of large and small vessels as well as heteronuclear MR of the heart and the skin. A concluding section ventures a glance beyond the horizon and explores future directions. The goal here is not to be comprehensive but to inspire the biomedical and diagnostic imaging communities to throw further weight behind the solution of the many remaining unsolved problems and technical obstacles of UHF-CMR with the goal to transfer MR physics driven methodological advancements into extra clinical value.
Collapse
Affiliation(s)
- Thoralf Niendorf
- Berlin Ultrahigh Field Facility, Max-Delbrueck Center for Molecular Medicine, Berlin, Germany.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
77
|
Hand J, Bosmans H, Caruana C, Keevil S, Norris D, Padovani R, Speck O. The European Federation of Organisations for Medical Physics Policy Statement No 14: The role of the Medical Physicist in the management of safety within the magnetic resonance imaging environment: EFOMP recommendations. Phys Med 2013; 29:122-5. [DOI: 10.1016/j.ejmp.2012.12.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
|
78
|
Abstract
More than a decade ago, multimodality imaging was introduced into clinical routine with the development of the positron emission tomography (PET)/computed tomography (CT) technique. Since then, PET/CT has been widely accepted in clinical imaging and has emerged as one of the main cancer imaging modalities. With the recent development of combined PET/magnetic resonance (MR) systems for clinical use, a promising new hybrid imaging modality is now becoming increasingly available. The combination of functional information delivered by PET with the morphologic and functional imaging of MR imaging (e.g., diffusion-weighted imaging, dynamic contrast-enhanced MR imaging and MR spectroscopy) offers exciting possibilities for clinical applications as well as basic research. However, the differences between CT and MR imaging are fundamental. This also leads to distinct differences between PET/CT and PET/MR not only regarding image interpretation but also concerning data acquisition, data processing and image reconstruction. This article provides an overview of the principal differences between PET/CT and PET/MR in terms of scanner design and technology, attenuation correction, speed, acquisition protocols, radiation exposure and safety aspects. PET/MR is expected to show advantages over PET/CT in clinical applications in which MR is known to be superior to CT due to its high intrinsic soft tissue contrast. However, as of now, only assumptions can be made about the future clinical role of PET/MR, as data about the performance of PET/MR in the clinical setting are still limited. The possible future clinical use of PET/MR in oncology, neurology and neurooncology, cardiology and imaging of inflammation is discussed.
Collapse
Affiliation(s)
- Florian C Gaertner
- Technische Universität München, Klinikum rechts der Isar, Department of Nuclear Medicine, Ismaninger Str. 22, 81675 München, Germany.
| | | | | |
Collapse
|
79
|
Measurements of RF heating during 3.0-T MRI of a pig implanted with deep brain stimulator. Magn Reson Imaging 2012; 31:783-8. [PMID: 23228310 DOI: 10.1016/j.mri.2012.11.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 11/07/2012] [Accepted: 11/08/2012] [Indexed: 11/22/2022]
Abstract
PURPOSE To present preliminary, in vivo temperature measurements during MRI of a pig implanted with a deep brain stimulation (DBS) system. MATERIALS AND METHODS DBS system (Medtronic Inc., Minneapolis, MN) was implanted in the brain of an anesthetized pig. 3.0-T MRI was performed with a T/R head coil using the low-SAR GRE EPI and IR-prepped GRE sequences (SAR: 0.42 and 0.39 W/kg, respectively), and the high-SAR 4-echo RF spin echo (SAR: 2.9 W/kg). Fluoroptic thermometry was used to directly measure RF-related heating at the DBS electrodes, and at the implantable pulse generator (IPG). For reference the measurements were repeated in the same pig at 1.5 T and, at both field strengths, in a phantom. RESULTS At 3.0T, the maximal temperature elevations at DBS electrodes were 0.46 °C and 2.3 °C, for the low- and high-SAR sequences, respectively. No heating was observed on the implanted IPG during any of the measurements. Measurements of in vivo heating differed from those obtained in the phantom. CONCLUSION The 3.0-T MRI using GRE EPI and IR-prepped GRE sequences resulted in local temperature elevations at DBS electrodes of no more than 0.46 °C. Although no extrapolation should be made to human exams and much further study will be needed, these preliminary data are encouraging for the future use 3.0-T MRI in patients with DBS.
Collapse
|
80
|
Shrivastava D, Abosch A, Hughes J, Goerke U, DelaBarre L, Visaria R, Harel N, Vaughan JT. Heating induced near deep brain stimulation lead electrodes during magnetic resonance imaging with a 3 T transceive volume head coil. Phys Med Biol 2012; 57:5651-65. [PMID: 22892760 DOI: 10.1088/0031-9155/57/17/5651] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Heating induced near deep brain stimulation (DBS) lead electrodes during magnetic resonance imaging with a 3 T transceive head coil was measured, modeled, and imaged in three cadaveric porcine heads (mean body weight = 85.47 ± 3.19 kg, mean head weight = 5.78 ± 0.32 kg). The effect of the placement of the extra-cranial portion of the DBS lead on the heating was investigated by looping the extra-cranial lead on the top, side, and back of the head, and placing it parallel to the coil's longitudinal axial direction. The heating was induced using a 641 s long turbo spin echo sequence with the mean whole head average specific absorption rate of 3.16 W kg(-1). Temperatures were measured using fluoroptic probes at the scalp, first and second electrodes from the distal lead tip, and 6 mm distal from electrode 1 (T(6 mm)). The heating was modeled using the maximum T(6 mm) and imaged using a proton resonance frequency shift-based MR thermometry method. Results showed that the heating was significantly reduced when the extra-cranial lead was placed in the longitudinal direction compared to the other placements (peak temperature change = 1.5-3.2 °C versus 5.1-24.7 °C). Thermal modeling and MR thermometry may be used together to determine the heating and improve patient safety online.
Collapse
Affiliation(s)
- Devashish Shrivastava
- Center for Magnetic Resonance Research, University of Minnesota, 2021, 6th St SE, Minneapolis, MN 55455, USA.
| | | | | | | | | | | | | | | |
Collapse
|
81
|
Koning W, Bluemink JJ, Langenhuizen EAJ, Raaijmakers AJ, Andreychenko A, van den Berg CAT, Luijten PR, Zwanenburg JJM, Klomp DWJ. High-resolution MRI of the carotid arteries using a leaky waveguide transmitter and a high-density receive array at 7 T. Magn Reson Med 2012; 69:1186-93. [PMID: 22760686 DOI: 10.1002/mrm.24345] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/12/2012] [Accepted: 05/01/2012] [Indexed: 11/09/2022]
Affiliation(s)
- W. Koning
- Department of Radiology; UMC; Utrecht The Netherlands
| | - J. J. Bluemink
- Department of Radiotherapy; UMC; Utrecht The Netherlands
| | | | | | | | | | - P. R. Luijten
- Department of Radiology; UMC; Utrecht The Netherlands
| | | | | |
Collapse
|
82
|
McRobbie DW. Occupational exposure in MRI. Br J Radiol 2012; 85:293-312. [PMID: 22457400 PMCID: PMC3486652 DOI: 10.1259/bjr/30146162] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 04/13/2011] [Accepted: 05/04/2011] [Indexed: 11/05/2022] Open
Abstract
This article reviews occupational exposure in clinical MRI; it specifically considers units of exposure, basic physical interactions, health effects, guideline limits, dosimetry, results of exposure surveys, calculation of induced fields and the status of the European Physical Agents Directive. Electromagnetic field exposure in MRI from the static field B(0), imaging gradients and radiofrequency transmission fields induces electric fields and currents in tissue, which are responsible for various acute sensory effects. The underlying theory and its application to the formulation of incident and induced field limits are presented. The recent International Commission on Non-Ionizing Radiation Protection (ICNIRP) Bundesministerium für Arbeit und Soziales and Institute of Electrical and Electronics Engineers limits for incident field exposure are interpreted in a manner applicable to MRI. Field measurements show that exposure from movement within the B(0) fringe field can exceed ICNIRP reference levels within 0.5 m of the bore entrance. Rate of change of field dB/dt from the imaging gradients is unlikely to exceed the new limits, although incident field limits can be exceeded for radiofrequency (RF) exposure within 0.2-0.5 m of the bore entrance. Dosimetric surveys of routine clinical practice show that staff are exposed to peak values of 42 ± 24% of B(0), with time-averaged exposures of 5.2 ± 2.8 mT for magnets in the range 0.6-4 T. Exposure to time-varying fields arising from movement within the B(0) fringe resulted in peak dB/dt of approximately 2 T s(-1). Modelling of induced electric fields from the imaging gradients shows that ICNIRP-induced field limits are unlikely to be exceeded in most situations; however, movement through the static field may still present a problem. The likely application of the limits is discussed with respect to the reformulation of the European Union (EU) directive and its possible implications for MRI.
Collapse
Affiliation(s)
- D W McRobbie
- Radiological Sciences Unit, Imperial College Healthcare NHS Trust, Charing Cross Hospital, London, UK.
| |
Collapse
|
83
|
Massire A, Cloos MA, Luong M, Amadon A, Vignaud A, Wiggins CJ, Boulant N. Thermal simulations in the human head for high field MRI using parallel transmission. J Magn Reson Imaging 2012; 35:1312-21. [PMID: 22241685 DOI: 10.1002/jmri.23542] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 11/28/2011] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To investigate, via numerical simulations, the compliance of the specific absorption rate (SAR) versus temperature guidelines for the human head in magnetic resonance imaging procedures utilizing parallel transmission at high field. MATERIALS AND METHODS A combination of finite element and finite-difference time-domain methods was used to calculate the evolution of the temperature distribution in the human head for a large number of parallel transmission scenarios. The computations were performed on a new model containing 20 anatomical structures. RESULTS Among all the radiofrequency field exposure schemes simulated, the recommended 39°C maximum local temperature was never exceeded when the local 10-g average SAR threshold was reached. On the other hand, the maximum temperature barely complied with its guideline when the global SAR reached 3.2 W/kg. The maximal temperature in the eye could very well rise by more than 1°C in both cases. CONCLUSION Considering parallel transmission, the recommended values of local 10-g SAR may remain a relevant metric to ensure that the local temperature inside the human head never exceeds 39°C, although it can lead to rises larger than 1°C in the eye. Monitoring temperature instead of SAR can provide increased flexibility in pulse design for parallel transmission.
Collapse
|
84
|
Powell J, Papadaki A, Hand J, Hart A, McRobbie D. Numerical simulation of SAR induced around Co-Cr-Mo hip prostheses in situ exposed to RF fields associated with 1.5 and 3 T MRI body coils. Magn Reson Med 2011; 68:960-8. [DOI: 10.1002/mrm.23304] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 11/01/2011] [Indexed: 11/07/2022]
|
85
|
Arteaga de Castro CS, van den Bergen B, Luijten PR, van der Heide UA, van Vulpen M, Klomp DWJ. Improving SNR and B1 transmit field for an endorectal coil in 7 T MRI and MRS of prostate cancer. Magn Reson Med 2011; 68:311-8. [PMID: 22127763 DOI: 10.1002/mrm.23200] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 07/19/2011] [Accepted: 08/06/2011] [Indexed: 11/07/2022]
Abstract
Higher magnetic field strengths like 7 T and above are desirable for MR spectroscopy given the increased spectral resolution and signal to noise ratio. At these field strengths, substantial nonuniformities in B(1)(+/-) and radiofrequency power deposition become apparent. In this investigation, we propose an improvement on a conventionally used endorectal coil, through the addition of a second element (stripline). Both elements are used as transceivers. In the center of the prostate, approximately 40% signal to noise ratio increase is achieved. In fact, the signal to noise ratio gain obtained with the quadrature configuration locally can be even greater than 40% when compared to the single loop configuration. This is due to the natural asymmetry of the B(1)(+/-) fields at high frequencies, which causes destructive and constructive interference patterns. Global specific absorption rate is reduced by almost a factor of 2 as expected. Furthermore, approximately a 4-fold decrease in local specific absorption rate is observed when normalized to the B(1) values in the center of the prostate. Because of the 4-fold local specific absorption rate decrease obtained with the dual channel setup for the same reference B(1) value (20 μT at 3.5 cm depth into the prostate) as compared to the single loop, the transmission power B(1) duty cycle can be increased by a factor 4. Consequently, when using the two-element endorectal coil, the radiofrequency power deposition is significantly reduced and radiofrequency intense sequences with adiabatic pulses can be safely applied at 7 T for (1)H magnetic resonance spectroscopy and MRI in the prostate. Altogether, in vivo (1)H magnetic resonance spectroscopic imaging of prostate cancer with a fully adiabatic sequence operated at a minimum B(1)(+) of 20 μT shows insensitivity to the nonuniform transmit field, while remaining within local specific absorption rate guidelines of 10 W/kg.
Collapse
Affiliation(s)
- C S Arteaga de Castro
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
| | | | | | | | | | | |
Collapse
|
86
|
Foster KR, Morrissey JJ. Thermal aspects of exposure to radiofrequency energy: report of a workshop. Int J Hyperthermia 2011; 27:307-19. [PMID: 21591896 DOI: 10.3109/02656736.2010.545965] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This special issue contains papers presented at an international workshop entitled 'Thermal Aspects of Radio Frequency Exposure' convened in Gaithersburg, Maryland, USA on 11-12 January 2010, and co-sponsored by the Mobile Manufacturers Forum, the GSM Association, and the US Food and Drug Administration. The goals of the workshop were to (1) identify appropriate health endpoints associated with thermal hazards and their time-dependence thresholds, and (2) outline future directions for research that might lead to an improved understanding of health and safety implications of human exposure to radiofrequency energy and design of improved exposure limits for this energy. This present contribution summarises some of the major conclusions of the speakers, and offers comments by one of the present authors on proposed research priorities and the implications of the material presented at the workshop for setting improved thermally based limits for human exposure to RF energy.
Collapse
Affiliation(s)
- Kenneth R Foster
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | | |
Collapse
|
87
|
Shrivastava D, Hanson T, Kulesa J, Tian J, Adriany G, Vaughan JT. Radiofrequency heating in porcine models with a "large" 32 cm internal diameter, 7 T (296 MHz) head coil. Magn Reson Med 2011; 66:255-63. [PMID: 21337423 PMCID: PMC3339408 DOI: 10.1002/mrm.22790] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Revised: 11/30/2010] [Accepted: 12/02/2010] [Indexed: 01/22/2023]
Abstract
Temperatures were measured in vivo in four pigs (mean animal weight = 110.75 kg and standard deviation = 6.13 kg) due to a continuous wave radiofrequency (RF) power irradiation with a 31.75 cm internal diameter and a 15.24 cm long, 7 T (296 MHz), eight channel, transverse electromagnetic head coil. The temperatures were measured in the subcutaneous layer of the scalp, 5, 10, 15, and 20 mm deep in the brain, and rectum using fluoroptic temperature probes. The RF power was delivered to the pig's head for ∼3 h (mean deposition time = 3.14 h and standard deviation = 0.06 h) at the whole head average specific absorption rate of ∼3 W kg(-1) (mean average specific absorption rate = 3.08 W kg(-1) and standard deviation = 0.09 W kg(-1)). Next, simple bioheat transfer models were used to simulate the RF power induced temperature changes. Results show that the RF power produced uniform temperature changes in the pigs' heads (mean temperature change = 1.68°C and standard deviation = 0.13°C) with no plateau achieved during the heating. No thermoregulatory alterations were detected due to the heating because the temperature responses of the pre-RF and post-RF epochs were not statistically significantly different. Simple, validated bioheat models may provide accurate temperature changes.
Collapse
Affiliation(s)
- Devashish Shrivastava
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | | | | | | | | | | |
Collapse
|
88
|
Abstract
The safe operation of both clinical and pre-clinical MR systems is critical. There are a wide range of potential MR hazards. This chapter covers both the theoretical background to issues of MR safety and the guidance on more practical issues. The main sources of information on national and international MR safety guidance and advice are discussed, as well as local safety policies which are required for all MR installations. The projectile effect and other MR safety issues due to static and time-varying magnetic fields are considered, such as peripheral nerve stimulation, tissue heating and RF burns. Finally, contrast agents, auditory effects and medical implants and devices are discussed, as well as the less thought about issue of biological safety of clinical and pre-clinical MR systems.
Collapse
Affiliation(s)
- Andrew Simmons
- King's College London, Institute of Psychiatry, Centre for Neuroimaging Sciences, London, UK.
| | | |
Collapse
|
89
|
van den Bergen B, Klomp DWJ, Raaijmakers AJE, de Castro CA, Boer VO, Kroeze H, Luijten PR, Lagendijk JJW, van den Berg CAT. Uniform prostate imaging and spectroscopy at 7 T: comparison between a microstrip array and an endorectal coil. NMR IN BIOMEDICINE 2011; 24:358-365. [PMID: 20960577 DOI: 10.1002/nbm.1599] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 06/21/2010] [Accepted: 07/09/2010] [Indexed: 05/30/2023]
Abstract
An endorectal coil and an eight-element microstrip array were compared for prostate imaging at 7 T. An extensive radiofrequency safety assessment was performed with the use of finite difference time domain simulations to determine safe scan parameters. These simulations showed that the endorectal coil can deliver substantially more B(1)(+) to the prostate than can the microstrip array within the specific absorption rate safety guidelines. However, the B(1)(+) field of the endorectal coil is very inhomogeneous, which makes the use of adiabatic pulses compulsory for T(1) - or T(2) -weighted imaging. As a consequence, a full prostate examination is only possible in a feasible amount of time when the microstrip array is used for T(1) - and T(2) -weighted imaging, whereas the endorectal coil is required for spectroscopic imaging. The pulse parameters were optimised within the specific absorption rate guidelines and thereafter used to provide a good illustration of the possibilities of prostate imaging at 7 T.
Collapse
Affiliation(s)
- Bob van den Bergen
- University Medical Centre Utrecht, Department of Radiotherapy, the Netherlands.
| | | | | | | | | | | | | | | | | |
Collapse
|
90
|
Shrivastava D, Abosch A, Hanson T, Tian J, Gupte A, Iaizzo PA, Vaughan JT. Effect of the extracranial deep brain stimulation lead on radiofrequency heating at 9.4 Tesla (400.2 MHz). J Magn Reson Imaging 2011; 32:600-7. [PMID: 20815057 DOI: 10.1002/jmri.22292] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
PURPOSE To study the effect of the extracranial portion of a deep brain stimulation (DBS) lead on radiofrequency (RF) heating with a transmit and receive 9.4 Tesla head coil. MATERIALS AND METHODS The RF heating was studied in four excised porcine heads (mean animal head weight = 5.46 +/- 0.14 kg) for each of the following two extracranial DBS lead orientations: one, parallel to the coil axial direction; two, perpendicular to the coil axial direction (i.e., azimuthal). Temperatures were measured using fluoroptic probes at four locations: one, scalp; two, near the second DBS lead electrode-brain contact; three, near the distal tip of the DBS lead; and four, air surrounding the head. A continuous wave RF power was delivered to each head for 15 min using the coil. Net, delivered RF power was measured at the coil (mean whole head average specific absorption rate = 2.94 +/- 0.08 W/kg). RESULTS RF heating was significantly reduced when the extracranial DBS lead was placed in the axial direction (temperature change = 0-5 degrees C) compared with the azimuthal direction (temperature change = 1-27 degrees C). CONCLUSION Development of protocols seems feasible to keep RF heating near DBS electrodes clinically safe during ultra-high field head imaging.
Collapse
Affiliation(s)
- Devashish Shrivastava
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | | | | | | | | | | | | |
Collapse
|
91
|
Abstract
The combination of electroencephalography (EEG) with functional magnetic resonance imaging (fMRI) forms a powerful tool for the investigation of brain function, but concurrent implementation of EEG and fMRI poses many technical challenges. Here, the motivation for combining EEG and fMRI is explored and methods underlying the combination are described. After a brief introduction to the two different techniques, the advantages and disadvantages of different methods of data recording are detailed, followed by a description of the artefacts encountered when performing EEG and fMRI measurements simultaneously, and the methods which have been developed to eliminate these artefacts. Important safety considerations and potential pitfalls associated with simultaneous recording are also described. The ways in which EEG and fMRI data analysis can be integrated are then described along with examples of key work which illustrate the power of combined EEG/fMRI measurements. The chapter concludes with a brief discussion of future directions for combined EEG/fMRI research.
Collapse
Affiliation(s)
- Karen Mullinger
- School of Physics and Astronomy, Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, UK.
| | | |
Collapse
|
92
|
YAMAGUCHI-SEKINO S, SEKINO M, UENO S. Biological Effects of Electromagnetic Fields and Recently Updated Safety Guidelines for Strong Static Magnetic Fields. Magn Reson Med Sci 2011; 10:1-10. [DOI: 10.2463/mrms.10.1] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
|
93
|
Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz). HEALTH PHYSICS 2010; 99:818-36. [PMID: 21068601 DOI: 10.1097/hp.0b013e3181f06c86] [Citation(s) in RCA: 584] [Impact Index Per Article: 41.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
|
94
|
Reeves MJ, Brandreth M, Whitby EH, Hart AR, Paley MNJ, Griffiths PD, Stevens JC. Neonatal cochlear function: measurement after exposure to acoustic noise during in utero MR imaging. Radiology 2010; 257:802-9. [PMID: 20876389 DOI: 10.1148/radiol.10092366] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To establish whether fetal exposure to the operating noise of 1.5-T magnetic resonance (MR) imaging is associated with cochlear injury and subsequent hearing loss in neonates. MATERIALS AND METHODS The study was performed with local research ethics committee approval and written informed parental consent. Neonatal hearing test results, including otoacoustic emission (OAE) data, were sought for all neonates delivered in Sheffield who had previously undergone in utero MR imaging between August 1999 and September 2007. The prevalence of hearing impairment in these neonates was determined, with corresponding 95% confidence intervals calculated by using the binomial exact method, and mean OAE measurements were compared with anonymized local audiometric reference data by using the t test. RESULTS One hundred three neonates who had undergone in utero MR imaging were identified; 96 of them had completed hearing screening assessment. Thirty-four of these babies were admitted to the neonatal intensive care unit (NICU), and one of them had bilateral hearing impairment. The prevalence of hearing impairment was 1% (one of 96; 95% confidence interval: 0.03%, 5.67%), which is in accordance with the prevalence expected, given the high proportion of babies in this study who had been in the NICU (ie, NICU graduates). In addition, for the well babies, there was no significant difference in mean OAE cochlear response compared with that for a reference data set of more than 16,000 OAE results. When NICU graduates were included in the comparison, a significant difference (P = .002) was found in one of four frequency bands used to analyze the cochlear response; however, this difference was small compared with the normal variation in OAE measurements. CONCLUSION The findings in this study provide some evidence that exposure of the fetus to 1.5-T MR imaging during the second and third trimesters of pregnancy is not associated with an increased risk of substantial neonatal hearing impairment.
Collapse
Affiliation(s)
- Michael J Reeves
- Academic Unit of Radiology, University of Sheffield, Royal Hallamshire Hospital, Glossop Rd, C Floor, Sheffield S10 2JF, England.
| | | | | | | | | | | | | |
Collapse
|
95
|
Kikuchi S, Saito K, Takahashi M, Ito K. Temperature elevation in the fetus from electromagnetic exposure during magnetic resonance imaging. Phys Med Biol 2010; 55:2411-26. [PMID: 20360633 DOI: 10.1088/0031-9155/55/8/018] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study computationally assessed the temperature elevations due to electromagnetic wave energy deposition during magnetic resonance imaging in non-pregnant and pregnant woman models. We used a thermal model with thermoregulatory response of the human body for our calculations. We also considered the effect of blood temperature variation on body core temperature. In a thermal equilibrium state, the temperature elevations in the intrinsic tissues of the woman and fetal tissues were 0.85 and 0.61 degrees C, respectively, at a whole-body averaged specific absorption rate of 2.0 W kg(-1), which is the restriction value of the International Electrotechnical Commission for the normal operating mode. As predicted, these values are below the temperature elevation of 1.5 degrees C that is expected to be teratogenic. However, these values exceeded the recommended temperature elevation limit of 0.5 degrees C by the International Commission on Non-Ionizing Radiation Protection. We also assessed the irradiation time required for a temperature elevation of 0.5 degrees C at the aforementioned specific absorption rate. As a result, the calculated irradiation time was 40 min.
Collapse
Affiliation(s)
- Satoru Kikuchi
- Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
| | | | | | | |
Collapse
|
96
|
Hand JW, Li Y, Hajnal JV. Numerical study of RF exposure and the resulting temperature rise in the foetus during a magnetic resonance procedure. Phys Med Biol 2010; 55:913-30. [PMID: 20090188 DOI: 10.1088/0031-9155/55/4/001] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Numerical simulations of specific absorption rate (SAR) and temperature changes in a 26-week pregnant woman model within typical birdcage body coils as used in 1.5 T and 3 T MRI scanners are described. Spatial distributions of SAR and the resulting spatial and temporal changes in temperature are determined using a finite difference time domain method and a finite difference bio-heat transfer solver that accounts for discrete vessels. Heat transfer from foetus to placenta via the umbilical vein and arteries as well as that across the foetal skin/amniotic fluid/uterine wall boundaries is modelled. Results suggest that for procedures compliant with IEC normal mode conditions (maternal whole-body averaged SAR(MWB) < or = 2 W kg(-1) (continuous or time-averaged over 6 min)), whole foetal SAR, local foetal SAR(10 g) and average foetal temperature are within international safety limits. For continuous RF exposure at SAR(MWB) = 2 W kg(-1) over periods of 7.5 min or longer, a maximum local foetal temperature >38 degrees C may occur. However, assessment of the risk posed by such maximum temperatures predicted in a static model is difficult because of frequent foetal movement. Results also confirm that when SAR(MWB) = 2 W kg(-1), some local SAR(10g) values in the mother's trunk and extremities exceed recommended limits.
Collapse
Affiliation(s)
- J W Hand
- Imaging Sciences Department, Imperial College London, London W12 0NN, UK.
| | | | | |
Collapse
|
97
|
Carmichael DW, Thornton JS, Rodionov R, Thornton R, McEvoy AW, Ordidge RJ, Allen PJ, Lemieux L. Feasibility of simultaneous intracranial EEG-fMRI in humans: A safety study. Neuroimage 2010; 49:379-90. [DOI: 10.1016/j.neuroimage.2009.07.062] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 06/22/2009] [Accepted: 07/24/2009] [Indexed: 10/20/2022] Open
|
98
|
Amendment to the ICNIRP "Statement on medical magnetic resonance (MR) procedures: protection of patients". HEALTH PHYSICS 2009; 97:259-261. [PMID: 19667810 DOI: 10.1097/hp.0b013e3181aff9eb] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
|
99
|
Salerno S, La Mendola C, Lo Casto A, Mamone G, Caccamo N, Cardinale AE, Salerno A. Reversible effect of MR and ELF magnetic fields (0.5 T and 0.5 mT) on human lymphocyte activation patterns. Int J Radiat Biol 2009; 82:77-85. [PMID: 16546906 DOI: 10.1080/09553000600589131] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE The aim of this study was to investigate the effects of magnetic fields (MF) of different intensity generated by a magnetic resonance (MR) unit (0.5 Tesla) and a double cylindrical coil (0.5 m Tesla) on human CD4(+) T cell lines. MATERIALS AND METHODS CD4(+) T cells were exposed for two hours under isothermal conditions (37 +/- 0.5 degrees C) to the above mentioned MF; a control group was provided for each exposed sample. After exposure, the samples were analysed in the laboratory for the following endpoints: release of cytokines, expression of surface markers, cell proliferation and levels of cytosolic free-calcium. RESULTS Exposure to MF for 2 h and subsequent in vitro stimulation in the presence of the appropriate mitogen, caused a decrease of interferon-gamma production, a decrease of cell proliferation, a decrease of expression of CD25 and a decrease of cytosolic free calcium concentration in exposed CD4(+) T cell lines. Data obtained, were statistically significant when evaluated after 24 h of in vitro culture, but were not significant, for both types of MF, when the experimental groups were analysed after prolonged in vitro culture. CONCLUSION These results indicate that static magnetic fields (SMF) can give rise to transient biological effects on T lymphocytes and the present system is a sensitive model for understanding the effects of MF on the immune system.
Collapse
Affiliation(s)
- Sergio Salerno
- Dipartimento Biotecnologie Mediche e Medicina Legale -- Sez. Radiologia, Università degli Studi di Palermo, Sicily, Italy
| | | | | | | | | | | | | |
Collapse
|
100
|
Hartwig V, Giovannetti G, Vanello N, Lombardi M, Landini L, Simi S. Biological effects and safety in magnetic resonance imaging: a review. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2009; 6:1778-98. [PMID: 19578460 PMCID: PMC2705217 DOI: 10.3390/ijerph6061778] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 06/05/2009] [Indexed: 11/16/2022]
Abstract
Since the introduction of Magnetic Resonance Imaging (MRI) as a diagnostic technique, the number of people exposed to electromagnetic fields (EMF) has increased dramatically. In this review, based on the results of a pioneer study showing in vitro and in vivo genotoxic effects of MRI scans, we report an updated survey about the effects of non-ionizing EMF employed in MRI, relevant for patients' and workers' safety. While the whole data does not confirm a risk hypothesis, it suggests a need for further studies and prudent use in order to avoid unnecessary examinations, according to the precautionary principle.
Collapse
Affiliation(s)
- Valentina Hartwig
- ITENI Laboratory, CNR Institute of Clinical Physiology, Pisa, Italy; E-Mails:
(V.H.);
(G.G.)
| | - Giulio Giovannetti
- ITENI Laboratory, CNR Institute of Clinical Physiology, Pisa, Italy; E-Mails:
(V.H.);
(G.G.)
| | - Nicola Vanello
- Department of Information Engineering, University of Pisa, Italy; E-Mail:
| | - Massimo Lombardi
- MRI Laboratory, G. Monasterio Foundation and CNR Institute of Clinical Physiology, Pisa, Italy; E-Mail:
| | - Luigi Landini
- Department of Information Engineering, University of Pisa, Italy; E-Mail:
| | - Silvana Simi
- Cell Biology and Cytogenetics Unit, CNR Institute of Clinical Physiology, Pisa, Italy
| |
Collapse
|