Laboratoire d'Imagerie Moleculaire et Fonctionnelle, UMR 5231 CNRS/Université Victor Segalen Bordeaux 2, Bordeaux, France.
NMR Biomed. 2011 Feb;24(2):145-53. doi: 10.1002/nbm.1563. Epub 2010 Dec 3.
MR thermometry offers the possibility to precisely guide high-intensity focused ultrasound (HIFU) for the noninvasive treatment of kidney and liver tumours. The objectives of this study were to demonstrate therapy guidance by motion-compensated, rapid and volumetric MR temperature monitoring and to evaluate the feasibility of MR-guided HIFU ablation in these organs. Fourteen HIFU sonications were performed in the kidney and liver of five pigs under general anaesthesia using an MR-compatible Philips HIFU platform prototype. HIFU sonication power and duration were varied. Volumetric MR thermometry was performed continuously at 1.5 T using the proton resonance frequency shift method employing a multi-slice, single-shot, echo-planar imaging sequence with an update frequency of 2.5 Hz. Motion-related suceptibility artefacts were compensated for using multi-baseline reference images acquired prior to sonication. At the end of the experiment, the animals were sacrificed for macroscopic and microscopic examinations of the kidney, liver and skin. The standard deviation of the temperature measured prior to heating in the sonicated area was approximately 1 °C in kidney and liver, and 2.5 °C near the skin. The maximum temperature rise was 30 °C for a sonication of 1.2 MHz in the liver over 15 s at 300 W. The thermal dose reached the lethal threshold (240 CEM(43) ) in two of six cases in the kidney and four of eight cases in the liver, but remained below this value in skin regions in the beam path. These findings were in agreement with histological analysis. Volumetric thermometry allows real-time monitoring of the temperature at the target location in liver and kidney, as well as in surrounding tissues. Thermal ablation was more difficult to achieve in renal than in hepatic tissue even using higher acoustic energy, probably because of a more efficient heat evacuation in the kidney by perfusion.
磁共振测温可实现高强度聚焦超声（HIFU）的精确引导，用于非侵入性治疗肾脏和肝脏肿瘤。本研究旨在通过运动补偿的快速容积式磁共振测温来演示治疗引导，并评估该器官中磁共振引导 HIFU 消融的可行性。在全身麻醉下，使用与磁共振兼容的 Philips HIFU 平台原型，在五头猪的肾脏和肝脏中进行了 14 次 HIFU 超声治疗。调整了 HIFU 超声的功率和持续时间。在 1.5 T 下使用质子共振频率偏移法连续进行容积式磁共振测温，采用多切片、单次激发、回波平面成像序列，更新频率为 2.5 Hz。通过在超声治疗前采集的多基线参考图像来补偿与运动相关的敏感性伪影。实验结束时，处死动物以对肾脏、肝脏和皮肤进行宏观和微观检查。在超声治疗区域加热前测量的温度的标准偏差在肾脏和肝脏中约为 1°C，在靠近皮肤处约为 2.5°C。在肝脏中，以 1.2 MHz 的频率进行 15 秒、300 W 的超声治疗，最大温升为 30°C。在肾脏中，有两例达到了 6 例中的致死阈值（240 CEM(43) ），在肝脏中有四例达到了 8 例中的致死阈值，但在光束路径中的皮肤区域仍低于该值。这些发现与组织学分析一致。容积式测温允许实时监测肝脏和肾脏以及周围组织中目标位置的温度。即使使用更高的声能，在肾脏中实现热消融也比在肝脏中更困难，这可能是由于肾脏中的灌注更有效地排出了热量。
