Low‐Intensity Focused Ultrasound Pulsation Device Used During Magnetic Resonance Imaging: Evaluation of Magnetic Resonance Imaging‐Related Heating at 3 Tesla/128 MHz

Objective The objective of this study was to determine magnetic resonance imaging ( MRI )‐related heating for a low‐intensity focused ultrasound pulsation ( LIFUP ) device used during MRI performed at 3  T /128  MHz . Materials and Methods A special phantom was constructed to mimic the thermal properties of the human brain, and a piece of human temporal bone (skull) was embedded on top. Four fluoroptic thermometry probes, placed above and below the skull, were used to measure temperature changes during MRI (3  T /128  MHz ; scanner‐reported head average specific absorption rate 1.1–2 W/kg) with and without concurrent LIFUP sonication. LIFUP sonication was applied using a focused ultrasound device ( BXP ulsar 1001, B rainsonix, I nc., L os A ngeles, CA , USA ) at a derated spatial‐peak temporal‐average intensity of 3870 mW/cm 2 . Results MRI performed at relatively high specific absorption rate ( SAR ) caused a slight elevation in temperature (≤0.6° C ). Concurrent use of MRI at a medium‐strength SAR and LIFUP sonication resulted in maximum temperature rise of 3.1° C after 8 min of continuous use. Conclusions Under the specific conditions utilized for this investigation, LIFUP sonication does not appear to present significant heating risks when used concurrently with MRI . This information has important implications for the use of the LIFUP sonication in human subjects undergoing MRI at 3  T /128  MHz .