Bucknor Matthew D, Rieke Viola, Do Loi, Majumdar Sharmila, Link Thomas M, Saeed Maythem
Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA.
J Magn Reson Imaging. 2014 Nov;40(5):1174-80. doi: 10.1002/jmri.24451. Epub 2013 Nov 7.
To evaluate hyperacute (<1 hour) changes on magnetic resonance (MR) and computed tomography (CT) imaging following MR-guided high-intensity focused ultrasound (MRgHIFU) in a swine bone model as a function of sonication number and energy.
Experimental procedures received approval from the local Institutional Animal Care and Use Committee. MRgHIFU was used to create distal and proximal ablations in the right femur of eight pigs. Each target was dosed with four or six sonications within similar volumes. The energy dosed to the distal target was higher (419 ± 19 J) than the proximal target (324 ± 17 J). The targeted femur and contralateral control were imaged before and after ablation using MR at 3T. Qualitative changes in signal on T1-weighted, T2-weighted, and T1-weighted postcontrast images were assessed. Ablation dimensions were calculated from postcontrast MRI. The 64-slice CT images were also obtained before and after ablation and qualitative changes were assessed.
MRgHIFU bone ablation size measured on average 8.5 × 21.1 × 16.2 mm (transverse × craniocaudal × anteroposterior). Interestingly, within similar prescribed volumes, increasing the number of sonications from 4 to 6 increased the depth of the intramedullary hypoenhanced zone from 2.9 mm to 6.5 mm (P < 0.001). There was no difference in the appearance of low versus high energy ablations. CT imaging did not show structural abnormalities.
The number of MRgHIFU focal sonications can be used to increase the depth of treatment within the targeted bone. Unlike CT, T2-weighted and contrast-enhanced MR demonstrated the hyperacute structural changes in the femur and surrounding soft tissue.
在猪骨模型中，评估磁共振引导下高强度聚焦超声（MRgHIFU）治疗后1小时内，磁共振成像（MR）和计算机断层扫描（CT）上的超急性变化，作为超声照射次数和能量的函数。
实验程序获得当地机构动物护理和使用委员会的批准。使用MRgHIFU在8头猪的右股骨中创建远端和近端消融灶。每个靶点在相似体积内接受4次或6次超声照射。给予远端靶点的能量（419±19焦耳）高于近端靶点（324±17焦耳）。在消融前后，使用3T磁共振对目标股骨和对侧对照进行成像。评估T1加权、T2加权和T1加权增强后图像上信号的定性变化。根据增强后MRI计算消融灶尺寸。在消融前后还获取了64层CT图像并评估定性变化。
MRgHIFU骨消融灶平均尺寸为8.5×21.1×16.2毫米（横向×头尾向×前后向）。有趣的是，在相似的规定体积内，超声照射次数从4次增加到6次，使髓内低增强区深度从2.9毫米增加到6.5毫米（P<0.001）。低能量与高能量消融灶的外观无差异。CT成像未显示结构异常。
MRgHIFU聚焦超声照射次数可用于增加目标骨内的治疗深度。与CT不同，T2加权和增强磁共振显示了股骨及周围软组织的超急性结构变化。
