Department of Radiology, UT Southwestern Medical Center, Dallas, Texas, USA.
Clinical Sites Research Program, Philips Research North America, Cambridge, Massachusetts, USA.
J Magn Reson Imaging. 2017 Aug;46(2):354-364. doi: 10.1002/jmri.25605. Epub 2017 Jan 9.
To evaluate magnetization-prepared 3D T -weighted magnetic resonance imaging (MRI) measurements of acute tissue changes produced during ablative MR high-intensity focused ultrasound (MR-HIFU) exposures.
A clinical MR-HIFU system (3T) was used to generate thermal lesions (n = 24) in the skeletal muscles of three pigs. T -weighted, 2D T -weighted, and magnetization-prepared 3D T -weighted sequences were acquired before and after therapy to evaluate tissue changes following ablation. Tissues were harvested shortly after imaging, fixed in formalin, and gross-sectioned. Select lesions were processed into whole-mount sections. Lesion dimensions for each imaging sequence (length, width) and for gross sections (diameter of lesion core and rim) were assessed by three physicists. Contrast-to-background ratio between lesions and surrounding muscle was compared.
Lesion dimensions on T and 2D T -weighted imaging sequences were well correlated (R ∼0.7). The contrast-to-background ratio between lesion and surrounding muscle was 7.4 ± 2.4 for the magnetization-prepared sequence versus 1.7 ± 0.5 for a conventional 2D T -weighted acquisition, and 7.0 ± 2.9 for a contrast-enhanced T -weighted sequence. Compared with diameter measured on gross pathology, all imaging sequences overestimated the lesion core by 22-33%, and underestimated the lesion rim by 6-13%.
After MR-HIFU exposures, measurements of the acute thermal damage patterns in muscle using a magnetization-prepared 3D T -weighted imaging sequence correlate with 2D T -weighted and contrast-enhanced T -weighted imaging, and all agree well with histology. The magnetization-prepared sequence offers positive tissue contrast and does not require IV contrast agents, and may provide a noninvasive imaging evaluation of the region of acute thermal injury at multiple times during HIFU procedures.
1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:354-364.
评估在消融性磁共振高强度聚焦超声（MR-HIFU）治疗过程中产生的急性组织变化的磁化准备 3D T1 加权磁共振成像（MRI）测量。
使用临床 MR-HIFU 系统（3T）在三头猪的骨骼肌中产生热损伤（n=24）。在治疗前后采集 T1 加权、2D T1 加权和磁化准备 3D T1 加权序列，以评估消融后组织变化。成像后立即采集组织，用福尔马林固定，大体切片。选择部分病变进行全层切片。由三位物理学家评估每个成像序列（长度、宽度）和大体切片（病变核心和边缘的直径）的病变尺寸。比较病变与周围肌肉之间的对比背景比。
T1 和 2D T1 加权成像序列上的病变尺寸相关性良好（R ∼0.7）。病变与周围肌肉之间的对比背景比磁化准备序列为 7.4±2.4，常规 2D T1 加权采集为 1.7±0.5，增强 T1 加权序列为 7.0±2.9。与大体病理测量的直径相比，所有成像序列均高估了病变核心 22-33%，低估了病变边缘 6-13%。
在 MR-HIFU 暴露后，使用磁化准备 3D T1 加权成像序列测量肌肉中的急性热损伤模式与 2D T1 加权和增强 T1 加权成像相关，且均与组织学结果吻合良好。磁化准备序列提供了阳性组织对比，且无需静脉内造影剂，可在 HIFU 治疗过程中的多个时间点提供对急性热损伤区域的无创性成像评估。
1 技术功效：第 2 阶段 J. MAGN. RESON. IMAGING 2017;46:354-364.
