Integrated ultrasound and magnetic resonance imaging for simultaneous temperature and cavitation monitoring during focused ultrasound therapies
Integrated ultrasound and magnetic resonance imaging for simultaneous temperature and cavitation monitoring during focused ultrasound therapies
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DOI：
10.1118/1.4823793
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发表时间：
2013-11-01
期刊：
影响因子：
3.8
通讯作者：
McDannold, Nathan
中科院分区：
文献类型：
--
作者：
Arvanitis, Costas D.;McDannold, Nathan
目的：超声可以通过粘滞加热、声空化或两者的结合，无创地产生不同的生物效应，这些效应可以用于开发癌症和其他疾病的广泛治疗方法。为了精确定位和控制这些不同的影响，需要能够同时绘制温度变化和空化活动的成像方法。为了满足这些需求，作者将超声成像阵列集成到mri引导聚焦超声（MRgFUS）系统中，分别通过被动声学测绘（PAM）和磁共振温度成像（MRTI）同时可视化热效应和机械效应。方法：采用经颅超声治疗脑肿瘤消融术的MRgFUS系统对该系统进行了实验，实验对象为模拟幻像组织和充满幻像的离体猕猴颅骨。在空化强化加热实验中，在不断增加的功率水平（30-110 W）下应用10 s连续波超声，直到宽带声发射（惯性空化的特征）明显。PAM中信号的存在或缺乏，以及其大小和位置，与MRTI中的焦点加热进行了比较。另外的实验将PAM与标准b超成像进行了比较，并测试了该系统在充满微泡超声造影剂的通道中绘制低功率（5w）爆发超声产生的空化活动的可行性。结果：当惯性空化明显时，PAM出现局部活性，MRTI发热明显增加。两种成像方式注册后，空化活动和加热的平均位置一致；在超声阵列轴向和横向方向上，最大空化活度与焦点加热的距离分别为-3.4 +/- 2.1 mm和-0.1 +/- 3.3 mm。扭曲和其他MRI问题在PAM/MRTI配准中引入了小的不确定性。虽然存在较大的变化，但空化图的平均强度（在超声过程中相对恒定）与峰值温升之间存在明显的非线性关系。数据与指数的拟合相关系数（R-2）为0.62。研究人员还发现，该系统能够通过b模式成像可视化空化活动，并在空化增强加热和超声造影剂低功率超声期间被动绘制经颅空化活动。结论：作者已经证明了将超声成像阵列集成到MRgFUS系统中以同时绘制局部空化活动和温度的可行性。作者预计，这种集成的方法可以用来开发空化增强消融的控制器，并促进这种和其他超声治疗的优化和发展。该综合系统也为研究声空化的生物效应提供了一个有用的工具。(C) 2013作者。
Purpose: Ultrasound can be used to noninvasively produce different bioeffects via viscous heating, acoustic cavitation, or their combination, and these effects can be exploited to develop a wide range of therapies for cancer and other disorders. In order to accurately localize and control these different effects, imaging methods are desired that can map both temperature changes and cavitation activity. To address these needs, the authors integrated an ultrasound imaging array into an MRI-guided focused ultrasound (MRgFUS) system to simultaneously visualize thermal and mechanical effects via passive acoustic mapping (PAM) and MR temperature imaging (MRTI), respectively.Methods: The system was tested with an MRgFUS system developed for transcranial sonication for brain tumor ablation in experiments with a tissue mimicking phantom and a phantom-filled ex vivo macaque skull. In experiments on cavitation-enhanced heating, 10 s continuous wave sonications were applied at increasing power levels (30-110 W) until broadband acoustic emissions (a signature for inertial cavitation) were evident. The presence or lack of signal in the PAM, as well as its magnitude and location, were compared to the focal heating in the MRTI. Additional experiments compared PAM with standard B-mode ultrasound imaging and tested the feasibility of the system to map cavitation activity produced during low-power (5 W) burst sonications in a channel filled with a microbubble ultrasound contrast agent.Results: When inertial cavitation was evident, localized activity was present in PAM and a marked increase in heating was observed in MRTI. The location of the cavitation activity and heating agreed on average after registration of the two imaging modalities; the distance between the maximum cavitation activity and focal heating was -3.4 +/- 2.1 mm and -0.1 +/- 3.3 mm in the axial and transverse ultrasound array directions, respectively. Distortions and other MRI issues introduced small uncertainties in the PAM/MRTI registration. Although there was substantial variation, a nonlinear relationship between the average intensity of the cavitation maps, which was relatively constant during sonication, and the peak temperature rise was evident. A fit to the data to an exponential had a correlation coefficient (R-2) of 0.62. The system was also found to be capable of visualizing cavitation activity with B-mode imaging and of passively mapping cavitation activity transcranially during cavitation-enhanced heating and during low-power sonication with an ultrasound contrast agent.Conclusions: The authors have demonstrated the feasibility of integrating an ultrasound imaging array into an MRgFUS system to simultaneously map localized cavitation activity and temperature. The authors anticipate that this integrated approach can be utilized to develop controllers for cavitation-enhanced ablation and facilitate the optimization and development of this and other ultrasound therapies. The integrated system may also provide a useful tool to study the bioeffects of acoustic cavitation. (C) 2013 Author(s).