使用梯度回波磁共振成像监测微泡介导的聚焦超声暴露中的声学空化。

Monitoring of acoustic cavitation in microbubble-presented focused ultrasound exposure using gradient-echo MRI.

作者信息

Wu Chen-Hua, Liu Hao-Li, Ho Cheng-Tao, Hsu Po-Hung, Fan Ching-Hsiang, Yeh Chih-Kuang, Kang Shih-Tsung, Chen Wen-Shiang, Wang Fu-Nien, Peng Hsu-Hsia

机构信息

Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan.

Department of Electrical Engineering, Chang-gung University, Taoyuan, Taiwan.

出版信息

J Magn Reson Imaging. 2020 Jan;51(1):311-318. doi: 10.1002/jmri.26801. Epub 2019 May 24.

DOI:10.1002/jmri.26801

PMID:31125166

Abstract

BACKGROUND

Gadolinium-based contrast agents can be used to identify the blood-brain barrier (BBB) opening after inducing a focused ultrasound (FUS) cavitation effect in the presence of microbubbles. However, the use of gadolinium may be limited for frequent routine monitoring of the BBB opening in clinical applications.

PURPOSE

To use a gradient-echo sequence without contrast agent administration for monitoring of acoustic cavitation.

STUDY TYPE

Animal and phantom prospective.

PHANTOM/ANIMAL MODEL: Static and flowing gel phantoms; six normal adult male Sprague-Dawley rats.

FIELD STRENGTH/SEQUENCE: 3T, 7T; fast low-angle shot sequence.

ASSESSMENT

Burst FUS with acoustic pressures = 1.5, 2.2, 2.8 MPa; pulse repetition frequencies = 1, 10,100 Hz; and duty cycles = 2%, 5%, 10% were transmitted to the chamber of a static phantom with microbubble concentrations = 10%, 1%, 0.1%. MR slice thicknesses = 3, 6, 8 mm were acquired. In flowing phantom experiments, 0.1%, 0.25%, 0.5%, 0.75%, and 1% microbubbles were infused and transmitted by burst FUS with an acoustic pressure = 0.4 and 1 MPa. In in vivo experiments, 0.25% microbubbles was infused and 0.8 MPa burst FUS was transmitted to targeted brain tissue beneath the superior sagittal sinus. The mean signal intensity (SI) was normalized using the mean SI from pre-FUS.

STATISTICAL TESTS

Two-tailed Student's t-test. P < 0.05 was considered statistically significant.

RESULTS

In the static phantom, the time courses of normalized SI decreases to minimum SI levels of 70-80%. In the flowing phantom, substantial normalized SI of 160-230% was present with variant acoustic pressures and microbubble concentrations. Compared with in vivo control rats, the brain tissue of experimental rats with transmission of FUS pulses exhibited considerable decreases of normalized SI (P < 0.001) because of the cavitation-induced perturbation of flow.

DATA CONCLUSION

Observing gradient-echo SI changes can help monitor the targeted location of microbubble-enhanced FUS, which in turn assists the monitoring of the BBB opening.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:311-318.

摘要

背景

基于钆的造影剂可用于在微泡存在下诱导聚焦超声（FUS）空化效应后识别血脑屏障（BBB）的开放。然而，在临床应用中，钆的使用可能因频繁常规监测BBB开放而受到限制。

目的

使用不注射造影剂的梯度回波序列监测声学空化。

研究类型

动物和模型前瞻性研究。

模型/动物模型：静态和流动凝胶模型；六只正常成年雄性Sprague-Dawley大鼠。

场强/序列：3T、7T；快速低角度激发序列。

评估

将声压分别为1.5、2.2、2.8MPa；脉冲重复频率分别为1、10、100Hz；占空比分别为2%、5%、10%的突发FUS传输至微泡浓度分别为10%、1%、0.1%的静态模型腔室。采集MR切片厚度为3、6、8mm的数据。在流动模型实验中，注入0.1%、0.25%、0.5%、0.75%和1%的微泡，并通过声压为0.4和1MPa的突发FUS进行传输。在体内实验中，注入0.25%的微泡，并将0.8MPa的突发FUS传输至上矢状窦下方的目标脑组织。使用FUS前的平均信号强度（SI）对平均SI进行归一化。