Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA.
J Magn Reson Imaging. 2017 Nov;46(5):1418-1422. doi: 10.1002/jmri.25676. Epub 2017 Feb 22.
To evaluate the effect of differences in sonication duration and power on the size of postcontrast ablation zone following magnetic resonance-guided focused ultrasound (MRgFUS) of bone in a swine femoral bone model.
Experimental procedures received approval from the Institutional Committee on Animal Research. MRgFUS was used to create two thermal lesions in the left femur of six pigs. Each target was subjected to six sonications. 400J of energy was used for each sonication. However, the distal target received the standard sonication duration of 20 seconds (20W), while the proximal target received a longer sonication duration of 40 seconds (10W). MRgFUS lesions were imaged with fat-saturated spoiled gradient echo sequence at 3.0T MRI 10 minutes following the administration of contrast. Maximum three-plane dimensions of the hypoenhanced ablation area were measured.
Postcontrast MR images demonstrated ovoid regions of hypoenhancement at each target. The average depth of ablation was significantly greater for the shorter high-power sonications (7.3 mm), compared to the longer lower-power sonications (4.5 mm), P = 0.026. The craniocaudal dimension was also greater for the shorter ablations 26.7 mm compared to the longer sonications 21.0 mm, P = 0.006.
Contrary to anecdotal clinical experience, this preclinical model suggests that during MRgFUS of bone, standard duration, higher-power sonications resulted in deeper ablation volumes compared to long duration, lower-power sonications. These results suggest that to achieve deeper ablations, if longer sonications are used, then the power should be relatively maintained, for a net energy increase.
1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:1418-1422.
在猪股骨模型中，评估超声持续时间和功率的差异对磁共振引导聚焦超声（MRgFUS）骨后对比消融区大小的影响。
实验程序获得机构动物研究委员会的批准。MRgFUS 用于在 6 头猪的左股骨中创建两个热损伤。每个靶标接受 6 次超声处理。每次超声处理使用 400J 的能量，但远侧靶标接受标准的 20 秒超声处理（20W），而近侧靶标接受 40 秒的较长超声处理（10W）。MRgFUS 损伤在造影后 10 分钟使用 3.0T MRI 上的脂肪饱和扰相梯度回波序列进行成像。测量低增强消融区的最大三平面尺寸。
对比后 MR 图像显示每个靶标均呈现出椭圆形低增强区域。与较长的低功率超声处理相比，较短的高功率超声处理的消融深度明显更大（7.3mm），P=0.026。较短的消融（26.7mm）的前后向尺寸也大于较长的超声处理（21.0mm），P=0.006。
与轶事临床经验相反，该临床前模型表明，在骨的 MRgFUS 中，标准持续时间、高功率超声处理导致的消融体积比长持续时间、低功率超声处理更深。这些结果表明，如果使用较长的超声处理来实现更深的消融，则应相对保持功率，以增加净能量。
1 技术功效：第 5 阶段 J. Magn. Reson. Imaging 2017;46:1418-1422.
