Abstract

Purpose

Magnetic resonance guided focused ultrasound (MRgFUS) treatment of tumors uses inter-sonication delays to allow heat to dissipate from the skin and other near-field tissues. Despite inter-sonication delays, treatment of tumors close to the skin risks skin burns. This work has designed and evaluated an open-source, conformable, skin-cooling system for body MRgFUS treatments to reduce skin burns and enable ablation closer to the skin.

Methods

A MR-compatible skin cooling system is described that features a conformable skin-cooling pad assembly with feedback control allowing continuous flow and pressure maintenance during the procedure. System performance was evaluated with hydrophone, phantom and in vivo porcine studies. Sonications were performed 10 and 5 mm from the skin surface under both control and forced convective skin-cooling conditions. 3D MR temperature imaging was acquired in real time and the accumulated thermal dose volume was measured. Gross analysis of the skin post-sonication was further performed. Device conformability was demonstrated at several body locations.

Results

Hydrophone studies demonstrated no beam aberration, but a 5–12% reduction of the peak pressure due to the presence of the skin-cooling pad assembly in the acoustic near field. Phantom evaluation demonstrated there is no MR temperature imaging precision reduction or any other artifacts present due to the coolant flow during MRgFUS sonication. The porcine studies demonstrated skin burns were reduced in size or eliminated when compared to the control condition.

Conclusion

An open-source design of an MRgFUS active skin cooling system demonstrates device conformability with a reduction of skin burns while ablating superficial tissues.

中文翻译：

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用于身体磁共振引导聚焦超声治疗的开源、舒适的皮肤冷却系统的设计和评估

 抽象的

 目的

磁共振引导聚焦超声 (MRgFUS) 肿瘤治疗利用超声间延迟来让热量从皮肤和其他近场组织消散。尽管超声间处理存在延迟，但治疗靠近皮肤的肿瘤仍存在皮肤烧伤的风险。这项工作设计并评估了一种开源、舒适的皮肤冷却系统，用于身体 MRgFUS 治疗，以减少皮肤烧伤并使消融更接近皮肤。

 方法

描述了一种与 MR 兼容的皮肤冷却系统，其特征在于具有反馈控制的舒适皮肤冷却垫组件，允许在手术过程中保持连续的流量和压力。通过水听器、体模和猪体内研究评估系统性能。在控制和强制对流皮肤冷却条件下，在距皮肤表面 10 毫米和 5 毫米处进行超声处理。实时采集 3D MR 温度成像并测量累积热剂量体积。进一步对超声处理后的皮肤进行总体分析。设备的顺应性在多个身体部位得到了证明。

 结果

水听器研究表明，没有光束畸变，但由于声学近场中存在皮肤冷却垫组件，峰值压力降低了 5-12%。模型评估表明，在 MRgFUS 超声处理过程中，冷却剂流动不会导致 MR 温度成像精度降低或出现任何其他伪影。对猪的研究表明，与对照条件相比，皮肤烧伤的面积减少或消除。

 结论

MRgFUS 主动皮肤冷却系统的开源设计展示了设备的顺应性，可在消融浅表组织的同时减少皮肤烧伤。