Effect of complex bolus-tissue load configurations on SAR distributions from dual concentric conductor applicators
Effect of complex bolus-tissue load configurations on SAR distributions from dual concentric conductor applicators
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DOI：
10.1109/10.797991
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发表时间：
1999-11-01
影响因子：
4.6
通讯作者：
Stauffer, PR
中科院分区：
文献类型：
--
作者：
Rossetto, F;Stauffer, PR
采用时域有限差分(FDTD)数值方法，对几种临床实际的复杂团注-组织负载模型下，4 cm-方形915-MHz双同心导体(DCC)微波天线阵列的功率沉积[比吸收率(SAR)]分布进行了理论分析。这项工作的目的是确定三种经常不可避免的团注-组织载荷的异质性对SAR的扰动效应。本工作研究的三种情况包括：骨(两根肋骨相距1 cm)嵌入肌肉或层状脂肪肌肉组织中5 mm或1 cm深，耦合团团与组织表面之间的小气泡，以及由于轮廓尖锐的解剖而变厚度的水团团层。FDTD模拟的结果表明，对于肋骨大小的骨骼，肌肉深度大于或等于5 mm，以及小于或等于1 mm厚的小气囊，对SBR分布的影响都相当小。直径为1 cm、深度为3 mm的较大气泡在气泡侧边附近有明显的SAR聚集，而当气泡位于DCC孔中心正下方、有较高的法向电场分量时，气泡下方有阻挡效应。在两个口径阵列下，从2.5毫米到7.5毫米的团状厚度变化只会对合成孔径雷达的均匀性和穿透性产生轻微的扰动，同时在较厚的团团下的合成孔径雷达略有减少，这应该通过改变施加到阵列单元的功率来充分适应。
Power deposition [specific absorption rate (SAR)] distributions from a two element array configuration of 4-cm-square 915-MHz dual concentric conductor (DCC) microwave antennas were characterized theoretically for several clinically realistic complex bolus-tissue load models using the finite difference time domain (FDTD) numerical method. The purpose of this effort was to determine the perturbing effects on SAR of three often unavoidable heterogeneities in the bolus-tissue load, The three cases studied in this work consist of bone (two ribs spaced 1 cm apart) embedded 5-mm or I-cm deep in muscle or layered fat-muscle tissue, small air bubbles trapped between the coupling bolus and tissue surface, and variable thickness water bolus layer due to sharply contoured anatomy. Results of the FDTD simulations demonstrate rather small effects on SBR distribution for both rib-sized bones greater than or equal to 5-mm deep in muscle and small air pockets less than or equal to 1-mm thick. Larger air bubbles >1-cm diameter by 3-mm depth showed a distinct concentration of SAR near the lateral sides of the air bubbles, and a blocking effect under the bubbles when located directly under the center of a DCC aperture where there is a higher normal E-field component. Variation from 2.5- to 7.5-mm bolus thickness under the two aperture array produced only minor perturbation of the uniformity and penetration of SAR, along with minor reduction in SAR under the thicker bolus which should be accommodated sufficiently by changes in applied power to the array elements.