An overview of electromagnetic safety considerations associated with magnetic resonance imaging.
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Electrocardiography↗
Biomedical subjects
E Kanal
Publications and source records attributed to E Kanal.
Patient monitoring during clinical MR imaging.
The impressive growth in the number of patients imaged with magnetic resonance (MR) technology has been accompanied by technical advances that have permitted more acutely ill patients to be studied with this diagnostic tool. Such patients, however, might require monitoring of vital functions during the examination. Unfortunately, the present construction of most MR imaging systems makes direct visualization of the patient difficult, if not impossible. Furthermore, the static and time-varying magnetic (and electric) fields associated with MR imaging systems may be incompatible with most physiologic monitoring devices, either because of safety or function. The authors review herein the data regarding presently available monitoring devices for various physiologic parameters and provide recommendations regarding what--and whom--to monitor during clinical MR examinations.
Humans↗
A comparison between magnetic resonance imaging and computed tomography for stereotactic coordinate determination.
The spatial accuracy of magnetic resonance imaging (MRI) has not been established for stereotactic surgery. Magnetic susceptibility artifacts may lead to anatomical distortion and inaccurate stereotactic MRI coordinates, especially when targets are in regions of the brain out of the center of the magnetic field. MRI-guided stereotactic localization, however, provides better multiplanar target resolution than is available with computed tomographic (CT) scanning. Therefore, we compared the accuracy of stereotactic coordinates determined by MRI and CT studies in 41 patients (53 targets). Coordinates were measured in each plane and as vector distances between the target and the center of the stereotactic frame on axial or coronal MRI studies. Absolute axial plane MRI and CT distances varied an average of 2.13 +/- 1.59 mm. The mean difference in measurements in the X (left-right) dimension was 1.19 mm and 1.55 mm in the Y (anterior-posterior) dimension. Central targets (located less than 2 cm from the frame center) had a mean MRI-CT difference of 2.09 +/- 1.79 mm; peripheral targets (greater than 2 cm from the frame center) differed by 2.17 +/- 1.3 mm. The voxel volumes were calculated for all compared images. Although differences between the physical properties of data acquisition with each imaging modality could explain the observed CT-MRI discrepancies, a 1-pixel difference in target selection could account totally for all the variance observed. MRI field strength (0.5 vs. 1.5 T) did not correlate with coordinate determination accuracy. We conclude that MRI-guided stereotactic localization can be used with confidence for most diagnostic, functional, and therapeutic stereotactic procedures.
Artifacts↗
Sonography vs MR imaging in children who are candidates for liver transplantation.
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Child↗
Burns associated with clinical MR examinations.
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Burns↗
Safety considerations in MR imaging.
The authors identify eight areas of potential safety concern during clinical magnetic resonance (MR) imaging. These include (a) biologic effects of the static magnetic field; (b) ferromagnetic attractive "projectile" effects of the static magnetic field; (c) potential effects of the relatively slowly time-varying magnetic field gradients; (d) effects of the rapidly varying radio-frequency (RF) magnetic fields, including RF power deposition concerns; (e) auditory considerations from noise caused by the rapidly pulsed magnetic field gradients; (f) safety considerations concerning superconductive systems, including quenches, use of cryogens, and cryogen storage and handling; (g) psychological effects, such as claustrophobia and anxiety induced because of the examination; and (h) possible effects of the intravenous use of the MR contrast agent gadopentetate dimeglumine. The concerns in each of these categories are elaborated upon, and the available data are presented to clarify their status.
Accident Prevention↗
Ferrioxamine as a magnetic resonance contrast agent. Preclinical studies and phase I and II human clinical trials.
The preclinical and clinical trial experience with ferrioxamine (S-FDF; Salutar, Inc.) as a contrast agent for magnetic resonance imaging (MRI) is summarized. The results in 44 patients or subjects show that the drug is safe and well tolerated when given intravenously. In certain conditions, early results show that the use of this contrast agent provides more information than can be obtained with MRI alone.
Adult↗
High resolution MR imaging of the knee.
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Humans↗
Policies, guidelines, and recommendations for MR imaging safety and patient management. SMRI Safety Committee.
The following are policies, guidelines, and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) concerning various issues related to magnetic resonance (MR) imaging safety and patient management. These policies, guidelines, and recommendations were developed to provide standardized and consistent information for use by health practitioners involved in clinical MR imaging.
Humans↗
Policies, guidelines, and recommendations for MR imaging safety and patient management. SMRI Safety Committee.
The following are policies, guidelines, and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) concerning various issues related to magnetic resonance (MR) imaging safety and patient management. These policies, guidelines, and recommendations were developed to provide standardized and consistent information for use by health practitioners involved in clinical MR imaging.
Humans↗
Magnetic ports in tissue expanders--a caution for MRI.
Although a great deal is known about the potential hazards of ferromagnetic materials relative to MRI, little has been written about the safety of tissue panders. Recently a new modification of the existing ports has been made available by incorporating a magnet for ease of identification of the injection site. Despite its low mass, the intrinsic magnetic field presents a contra-indicating factor due to the potential for torque and movement in the presence of the strong magnetic field found in the clinical MR imagers. With any evidence of tissue expander prosthesis obtained in the history, a careful questioning about the possibility of a magnetic port should be carried out.
Equipment Safety↗
Computer-based tutorial in MR imaging.
PURPOSE: To test the effectiveness of customized software as a teaching tool to help the novice understand basic physics concepts underlying the creation of MR images via various pulse sequences. METHODS: The authors have developed animating graphic and highly interactive electronic MR audiovisual software for the Macintosh computer in the C programming language, and have integrated it into the classroom setting for teaching MR imaging physics concepts such as T1, T2, T2*, proton density, RF excitation, TR, TE, TI, flip angle, static magnetic field strength, gradient magnetic fields, section thickness, number of phase-encoding gradients, number of excitations, field of view, intersection gap, receiver bandwidth, contrast agent(s), etc. The program interactively demonstrates the effects of these variables upon such imaging objectives as voxel dimensions, section quantity, total scanned volume, signal-to-noise ratio, contrast, contrast-to-noise ratios, resolving power, and scan acquisition time. Partial saturation, gradient echo, inversion recovery, and fat-saturation imaging techniques are included. Written posttests on the syllabus covered in our basic MR course were administered to three groups: 43 student professionals (technologist/physicist/radiologist) (control professional group) before, 149 student professionals (exposed professional group) after the addition of the tutorial software into the MR course as an integral part of the teaching process, and a group of 200 pharmaceutical sales staff with little to no prior MR or scientific background (exposed pharmaceutical group). The scores were then evaluated and compared among the groups. One hundred ten students exposed to this software also anonymously rated the software on a 1 to 5 scale (harmful to very helpful, respectively) as to their feeling regarding its role in their MR educational experience and the ease with which they were able to understand the material covered in the basic MR course curriculum. RESULTS: Mean test scores were statistically significantly lower in the Control Professional Group (60%, +/- 2.59 standard error of the mean (SEM)) than in either the Exposed Pharmaceutical (73% +/- 0.75 SEM) or Exposed Professional Groups (77% +/- 0.99 SEM). The mean subjective assessment score regarding the software was 4.8 (scale 1 to 5). CONCLUSION: This custom-developed interactive MR tutorial software is demonstrated to be effective in assisting even those new to MR imaging in understanding the concepts underlying MR imaging physics in a manner that is felt to be significantly more palatable than lectures, articles, and/or textbooks alone.
Computer-Assisted Instruction↗
Chronic acquired hepatic failure: MR imaging of the brain at 1.5 T.
The results of MR imaging of the brain at 1.5 T in 42 adults with non-Wilsonian chronic hepatic failure are reported. T1-weighted images demonstrated increased signal in the globus pallidus in 30 patients and in the putamen in 21, while T2-weighted images demonstrated no corresponding alteration in signal intensity. Symmetric low intensity in the central portion of the globus pallidus on spin-density and T2-weighted images in two patients correlated with regions of calcification on CT scans. Increased intensity on T1-weighted images also occurred in the mesencephalon surrounding the red nucleus (17/42) and in the quadrigeminal plate (4/42). Three patients demonstrated increased intensity in the pons on T2-weighted images unassociated with clinical brainstem dysfunction. Increased intensity on T1-weighted images was seen in the anterior pituitary in 28 of 35 patients. Alterations in signal intensity were not demonstrated in the cerebral cortex or cerebellum. MR findings did not correlate with laboratory indices of hepatic or thyroid function, with histologic liver diagnosis, or with neurologic status at the time of MR evaluation. Increased signal intensity in the basal ganglia, pituitary gland, and mesencephalon surrounding the red nuclei is characteristic of chronic hepatocellular dysfunction. Deposition of an as yet unidentified paramagnetic substance or altered intracellular water relaxation associated with the proliferation of astrocyte cytoplasmic organelles is postulated as the likely mechanism for this previously undescribed MR manifestation of chronic acquired hepatic failure.
Brain↗