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^® 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^® 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 −0.4 ± 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 user-definable parameters.

中文翻译：

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磁共振引导的高强度聚焦超声（MRgHIFU）诱导的猪模型深层和浅层目标体内大体积热疗的特征

摘要

目的

为了表征在猪模型中体内深部和浅部靶标中由磁共振引导的高强度聚焦超声（MRgHIFU）诱导的大体积高温（HT）的温度场和组织损伤情况。

方法

十九HT会话进行体内与商业MRgHIFU系统（Sonalleve ^®在八个猪为58毫米的横截面直径的温度场后腿肌肉V2，深刻Medical公司，米西索加，ON，加拿大）。在目标感兴趣区域（tROI）中评估的温度统计信息包括准确性，时间变化和均匀性。研究了成像平面的数量和位置对基于反馈的温度控制的影响。温度场的特征在于时间范围（TIR，每个体素停留在40–45°C内的持续时间）图。组织损伤的特征在于对比增强的MRI，宏观和组织病理学分析。该Sonalleve的性能^® 该系统以商业模型为基准。

结果

在所有高温处理期间，平均温度（T _avg）与所需温度之间的平均差为-0.4±0.5°C；温度的标准偏差为1.2±0.2°C; 30分钟HT的T _avg的时间变化为0.6±0.2°C，温度均匀性为1.5±0.2°C。当在不同位置应用基于反馈的平面时，在TIR尺寸上观察到2.2厘米（猪）和1.5厘米（幻像）的差异。组织病理学检查显示，有62.5％的HT疗程在目标体积内出现肌纤维变性/坏死。

结论

大容量MRgHIFU介导的HT已成功实施，并在猪模型中在体内深层和浅层目标中进行了表征，并且热量分布可通过用户定义的参数进行修改。