MR Safety and the American College of Radiology White Paper.
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Magnetic Resonance Imaging↗
Biomedical subjects
Frank G Shellock
Publications and source records attributed to Frank G Shellock.
New metallic implant used for permanent contraception in women: evaluation of MR safety.
OBJECTIVE: This ex vivo investigation evaluated the safety of using MR imaging with a new metallic implant designed to provide permanent birth control. CONCLUSION: The findings indicated that it should be safe for patients with this metallic contraceptive implant to undergo MR imaging with systems using static magnetic fields of 1.5 T or less.
Contraceptive Devices, Female↗
Radiofrequency energy-induced heating of bovine articular cartilage: evaluation of a new temperature-controlled, bipolar radiofrequency system used at different settings.
This in vitro investigation determined temperature changes associated with radiofrequency energy-induced heating of bovine articular cartilage using a newly developed, temperature-controlled, bipolar radiofrequency system at different settings. Cartilage tissue samples were placed in a saline bath maintained at room temperature. Radiofrequency energy was applied using a temperature-controlled, bipolar radiofrequency system at four different settings. Fluoroptic thermometry recorded temperatures at the radiofrequency electrode-tissue interface at 1-second intervals before, during delivery (1-5 seconds), and after delivery (1-3 seconds) of radiofrequency energy. Ten data acquisitions were obtained at each equipment setting. There were statistically significant (P<.05) increases in cartilage tissue temperatures associated with the different temperature settings. The temperature at the radiofrequency electrode-tissue interface was relatively close to the equipment's set temperature. These data provide basic information for the temperature-controlled, bipolar radiofrequency system applied to articular cartilage and may be useful in guiding electrosurgical equipment for thermal-assisted chondroplasty.
Analysis of Variance↗
MR imaging-related heating of deep brain stimulation electrodes: in vitro study.
BACKGROUND AND PURPOSE: Recent work has shown a potential for excessive heating of deep brain stimulation electrodes during MR imaging. This in vitro study investigates the relationship between electrode heating and the specific absorption rate (SAR) of several MR images. METHODS: In vitro testing was performed by using a 1.5-T MR imaging system and a head transmit-receive coil, with bilateral deep brain stimulation systems positioned in a gel saline-filled phantom, and temperature monitoring with a fluoroptic thermometry system. Standardized fast spin-echo sequences were performed over a range of high, medium, and low SAR values. Several additional, clinically important MR imaging techniques, including 3D magnetization prepared rapid acquisition gradient-echo imaging, echo-planar imaging, quantitative magnetization transfer imaging, and magnetization transfer-suppressed MR angiography, were also tested by using typical parameters. RESULTS: A significant, highly linear relationship between SAR and electrode heating was found, with the temperature elevation being approximately 0.9 times the local SAR value. Minor temperature elevations, <1 degrees C, were found with the fast spin-echo, magnetization prepared rapid acquisition gradient-echo, and echo-planar clinical imaging sequences. The high dB/dt echo-planar imaging sequence had no significant heating independent of SAR considerations. Sequences with magnetization transfer pulses produced temperature elevations in the 1.0 to 2.0 degrees C range, which was less than theoretically predicted for the relatively high SAR values. CONCLUSION: A potential exists for excessive MR imaging-related heating in patients with deep brain stimulation electrodes; however, the temperature increases are linearly related to SAR values. Clinical imaging sequences that are associated with tolerable temperature elevations in the <or=2.0 degrees C range at the electrode tips can be performed safely within an SAR range <2.4 W/kg local (0.9 W/kg whole body averaged).
Body Temperature↗