Correlation of ultrasound phase with physical skull properties
Correlation of ultrasound phase with physical skull properties
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DOI：
10.1016/s0301-5629(02)00503-3
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发表时间：
2002-05-01
影响因子：
2.9
通讯作者：
Hynynen, K
中科院分区：
文献类型：
--
作者：
Clement, GT;Hynynen, K
使用聚焦超声（US）的脑部疾病的非侵入性治疗需要一个可靠的模型，用于预测由于使用在体内获得的物理参数的颅骨的场的失真。先前的研究表明，单独控制US相位足以使用相控US阵列通过颅骨产生焦点。本研究集中在识别方法来估计相位失真。这将是至关重要的未来临床使用的非侵入性脑治疗。检查了10个离体人颅骨。使用计算机断层扫描（CT）在水中对每个样品进行成像。这些信息被用来确定颅骨的内外表面，厚度作为位置的函数，以及内部结构。通过将颅骨碎片放置在换能器和接收器之间，使颅骨垂直于换能器，获得一系列点上的相位测量。颅骨厚度与超声相移之间存在相关性。数据的线性拟合遵循当使用平均声速2650 m/s时由均匀头骨预测的数据。大的方差（SD = 60度，平均值= 50度）表明内部骨速度和密度波动的额外作用。为了减少差异，头骨首先被研究为三层结构。其次，将密度相关的骨速度波动引入单层和三层模型。已确定，使用密度调整平均传播速度改进了总体相位预测。结果表明，它是可能的使用厚度和密度信息从CT图像预测的US相位失真引起的颅骨足够准确的治疗像差校正。此外，测量提供了可用于临床治疗的颅骨厚度和密度的相位依赖系数。(C)2002年世界医学超声生物学联合会。
Noninvasive treatment of brain disorders using focused ultrasound (US) requires a reliable model for predicting the distortion of the field due to the skull using physical parameters obtained in vivo. Previous studies indicate that control of US phase alone is sufficient for producing a focus through the skull using a phased US array. The present study concentrates on identifying methods to estimate phase distortion. This will be critical for the future clinical use of noninvasive brain therapy. Ten ex vivo human calvaria were examined. Each sample was imaged in water using computerized tomography (CT). The information was used to determine the inner and outer skull surfaces, thickness as a function of position, and internal structure. Phase measurement over a series of points was obtained by placing a skull fragment between a transducer and a receiver with the skull normal to the transducer. Correlation was found between the skull thickness and the US phase shift. A linear fit of the data follows that predicted by a homogeneous skull when average speed of sound 2650 m/s was used. Large variance (SD = 60degrees, mean = 50degrees) indicates the additional role of internal bone speed and density fluctuations. In an attempt to reduce the variance, the skull was first studied as a three-layer structure. Next, density-dependent bone speed fluctuation was introduced to both the single-layer and three-layer models. It was determined that adjustment of the mean propagation speeds using density improves the overall phase prediction. Results demonstrate that it is possible to use thickness and density information from CT images to predict the US phase distortion induced by the skull accurately enough for therapeutic aberration correction. In addition, the measurements provide coefficients for phase dependence on skull thickness and density that can be used in clinical treatments. (C) 2002 World Federation for Ultrasound in Medicine Biology.