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

Abstract

Purpose: To characterize temperature fields and tissue damage profiles of large-volume hyperthermia (HT) induced by magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) in deep and superficial targets in vivo in a porcine model. Methods: Nineteen HT sessions were performed in vivo with a commercial MRgHIFU system (Sonalleve V R V2, Profound Medical Inc., Mississauga, ON, Canada) in hind leg muscles of eight pigs with temperature fields of cross-sectional diameter of 58-mm. Temperature statistics evaluated in the target region-of-interest (tROI) included accuracy, temporal variation, and uniformity. The impact of the number and location of imaging planes for feedback-based temperature control were investigated. Temperature fields were characterized by time-in-range (TIR, the duration each voxel stays within 40-45 C) maps. Tissue damage was characterized by contrast-enhanced MRI, and macroscopic and histopathological analysis. The performance of the Sonalleve V R system was benchmarked against a commercial phantom. Results: Across all HT sessions, the mean difference between the average temperature (T avg) and the desired temperature was À0.4 ± 0.5 C; the standard deviation of temperature 1.2 ± 0.2 C; the temporal variation of T avg for 30-min HT was 0.6 ± 0.2 C, and the temperature uniformity was 1.5 ± 0.2 C. A difference of 2.2-cm (in pig) and 1.5-cm (in phantom) in TIR dimensions was observed when applying feedback-based plane(s) at different locations. Histopathology showed 62.5% of examined HT sessions presenting myofiber degeneration/necrosis within the target volume. Conclusion: Large-volume MRgHIFU-mediated HT was successfully implemented and characterized in a porcine model in deep and superficial targets in vivo with heating distributions modifiable by userdefinable parameters.

Targetability of cervical cancer by magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU)-mediated hyperthermia (HT) for patients receiving radiation therapy

“…Despite these limitations, the results of this study provide important evidence that most late-stage cervical cancer primaries are targetable by MRgHIFU HT, which supports the progression into a clinical trial. We have evaluated the feasibility and safety of applying MRgHIFU induced HT for a variety of clinically mimicking pelvic geometries in a porcine model [40], and also characterized the heating volume of the MRgHIFU-induced HT [86]. Furthermore, the feasibility of using MRgHIFU for treating rectal cancer patients was also evaluated by Chu et al [43].…”

Technical note: Low‐cost MR‐compatible pneumatic respiratory organ motion simulator for the development of MR‐guided thermal therapy

“…3,4 Recent innovations are expanding the use of these MRgFUS systems for the delivery of longduration hyperthermia over larger and deep volumes. 5,6 MR thermometry allows for real-time temperature measurement over treatment volumes to ensure patient safety and precise heat deposition during the ablation procedure.…”

“…Clinical MRgFUS systems are currently used for the ablation of deep soft tissue tumors in sites such as the brain, uterine fibroids, prostate, pancreas, and bone metastases 3,4 . Recent innovations are expanding the use of these MRgFUS systems for the delivery of long‐duration hyperthermia over larger and deep volumes 5,6 …”