IEEE Trans Med Imaging. 2014 Jun;33(6):1324-37. doi: 10.1109/TMI.2014.2310704.
Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is a noninvasive method for thermal ablation, which exploits the capabilities of magnetic resonance imaging (MRI) for excellent visualization of the target and for near real-time thermometry. Oncological quality of ablation may be obtained by volumetric sonication under automatic feedback control of the temperature. For this purpose, a new nonparametric (i.e., model independent) temperature controller, using nonlinear negative reaction, was designed and evaluated for the iterated sonication of a prescribed pattern of foci. The main objective was to achieve the same thermal history at each sonication point during volumetric MRgHIFU. Differently sized linear and circular trajectories were investigated ex vivo and in vivo using a phased-array HIFU transducer. A clinical 3T MRI scanner was used and the temperature elevation was measured in five slices simultaneously with a voxel size of 1 ×1 ×5 mm(3) and temporal resolution of 4 s. In vivo results indicated a similar thermal history of each sonicated focus along the prescribed pattern, that was 17.3 ± 0.5 °C as compared to 16 °C prescribed temperature elevation. The spatio-temporal control of the temperature also enabled meaningful comparison of various sonication patterns in terms of dosimetry and near-field safety. The thermal build-up tended to drift downwards in the HIFU transducer with a circular scan.
磁共振引导高强度聚焦超声（MRgHIFU）是一种非侵入性的热消融方法，利用磁共振成像（MRI）的出色可视化能力和近实时测温能力。通过自动反馈控制温度的容积式超声，可以获得肿瘤消融的质量。为此，设计并评估了一种新的非参数（即无模型）温度控制器，采用非线性负反应，用于预定焦点模式的迭代超声。主要目标是在容积性 MRgHIFU 中的每个超声点获得相同的热历史。使用相控阵 HIFU 换能器在离体和体内研究了不同尺寸的线性和圆形轨迹。使用临床 3T MRI 扫描仪，同时使用体素大小为 1×1×5mm3 和时间分辨率为 4s 的 5 个切片测量温度升高。体内结果表明，沿着预定模式的每个超声焦点的热历史相似，为 17.3±0.5°C，而规定的温度升高为 16°C。温度的时空控制还使得能够根据剂量学和近场安全性对各种超声模式进行有意义的比较。随着圆形扫描，HIFU 换能器中的热积累有向下漂移的趋势。
