Feasibility and safety assessment of magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU)-mediated mild hyperthermia in pelvic targets evaluated using an in vivo porcine model

Abstract

2019) Feasibility and safety assessment of magnetic resonance-guided highintensity focused ultrasound (MRgHIFU)-mediated mild hyperthermia in pelvic targets evaluated using an in vivo porcine modelABSTRACT Purpose: To evaluate the feasibility and assess safety parameters of magnetic resonance-guided highintensity focused ultrasound (MRgHIFU)-mediated hyperthermia (HT; heating to 40-45 C) in various pelvic targets in a porcine model in vivo. Methods: Thirteen HT treatments were performed in six pigs with a commercial MRgHIFU system (Sonalleve V2, Profound Medical Inc., Mississauga, Canada) to muscle adjacent to the ventral/dorsal bladder wall and uterus to administer 42 C (±1 ) for 30 min (±5%) using an 18-mm target diameter and 100 W power. Feasibility was assessed using accuracy, uniformity, and MR-thermometry performance-based metrics. Safety parameters were assessed for tissues in the targets and beam-path by contrast-enhanced MRI, gross-pathology and histopathology. Results: Across all HT sessions, the mean difference between average temperature (T avg ) and the target temperature within the target region-of-interest (tROI, the cross-section of the heated volume at focal depth) was 0.51 ± 0.33 C. Within the tROI, the temperature standard deviation averaged 1.55 ± 0.31 C, the average 30-min T avg variation was 0.80 ± 0.17 C, and the maximum difference between T avg and the 10th-or 90th-percentile temperature averaged 2.01 ± 0.44 C. The average time to reach !41 C and cool to 40 C within the tROI at the beginning and end of treatment was 47.25 ± 27.47 s and 66.37 ± 62.68 s, respectively. Compared to unheated controls, no abnormally-perfused tissue or permanent damage was evident in the MR images, gross pathology or histological analysis. Conclusions: MRgHIFU-mediated HT is feasible and safety assessment is satisfactory for treating an array of clinically-mimicking pelvic geometries in a porcine model in vivo, implying the technique may have utility in treating pelvic targets in human patients. ARTICLE HISTORY

Sonogenetics for noninvasive and cellular-level neuromodulation in rodent brain

“…We have established the MR thermometry technique for monitoring heating by FUS in our previous studies 24,25 . MR thermometry shows localized heating at the FUS spatially targeted brain location.…”

Characterization of magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU)-induced large-volume hyperthermia in deep and superficial targets in a porcine model

“…The Sonalleve V R V2 system [41][42][43] comprises of a patient tabletop that can be locked into an MRI scanner bore (Ingenia 1.5 T, Philips, Best, the Netherlands). The tabletop accommodates a 2-channel RF receive coil and a 256-channel phased-array HIFU transducer.…”

“…In short, HT was primarily regulated by the tROI temperature in the target plane. The aim is to raise the temperature to a pre-defined target temperature and to homogenously maintain the temperature in each voxel within the tROI [43]. The 58-mm diameter circular tROI is divided into seven 'subcells' (each with Ø ¼ 16-mm) arranged on a hexagonal grid [40].…”

“…Sandbags were used to further stabilize and support the animal on the HIFU table (Figure 1(A)). [40,42,43] was acquired to image hind leg muscle for treatment planning: echo time ¼130 ms, repetition time ¼1300 ms, flip angle ¼90 , number of signal averages ¼1, field-of-view ¼250 Â 259-mm 2 , acquisition matrix ¼250 Â 217, spatial resolution (voxel size) ¼1.12 Â 1.19 Â 2.5-mm 3 , scan time ¼190-s. We maintained a safety margin of !10-mm [45][46][47] between the HIFU beampath and any bone. 4.…”

“…4. Temperature monitoring: The proton resonance frequency shift (PRFS) method was used for temperature mapping [39,40,42,43] using field of view ¼400 Â 400mm 2 , voxel size ¼2.5 Â 2.5 Â 7mm 3 , temporal resolution ¼3.7s. Briefly, a dynamic, RF-spoiled, fast-fieldecho echo-planar imaging (FFE-EPI) sequence was utilized to obtain magnitude and phase images.…”