Abstract
Purpose: To evaluate the feasibility and assess safety parameters of magnetic resonance-guided high-intensity 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 (Tavg) 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 Tavg variation was 0.80 ± 0.17 °C, and the maximum difference between Tavg 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.
Highlights
Mild hyperthermia (HT), which refers to increasing the temperature to 40–45°C for an extended period of time up to 1.5 hours, has been reported to be one of the most effective sensitizers for radiation therapy (RT) and/or chemotherapy[1]
Abnormally-perfused tissue or permanent damage was evident in the MR images, gross pathology, or histological analysis
magnetic resonance-guided high-intensity focused ultrasound (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
Summary
Mild hyperthermia (HT), which refers to increasing the temperature to 40–45°C for an extended period of time up to 1.5 hours, has been reported to be one of the most effective sensitizers for radiation therapy (RT) and/or chemotherapy[1]. The addition of HT to RT can increase complete response rates (CRRs), partial response rates (PRRs), and improve overall survival[3,14,15]. A prospective, randomized, multicenter trial reported increased CRRs of 26% (p=0.003), 22% (p=0.01), and 6% (p>0.05) in the treatment of cervical cancer (n=114), bladder cancer (n=101), and rectal cancer (n=143)[16], respectively. Such results showed the addition of HT to RT resulted in a significant enhancement of treatment efficacy. Other studies showing pelvic cancer treatment sites that could benefit from adding HT to an RT treatment regimen include bladder cancer[16–18], rectal and colon cancer[15,19], uterine cancers (including both uterine cervix and uterine corpus)[20–23] and prostate cancer[24]
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