Numerical study of SAR for multi-component orthopaedic hip replacement system during MRI
Numerical study of SAR for multi-component orthopaedic hip replacement system during MRI
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多部件骨科髋关节置换系统MRI期间SAR数值研究
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
W. Kainz
中科院分区：
文献类型：
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作者：
Jianfeng Zheng;Dawei Li;Ji Chen;W. Kainz
在这项研究中，我们提出了多组件骨科髋关节置换系统的比吸收率（SAR）的数值模拟。SAR用于评价磁共振成像（MRI）期间器械的射频（RF）致热。由于多组件骨科髋关节置换系统具有多种设计和尺寸的组件组合，因此计算量很大，几乎不可能评价每种可能组合和配置的SAR和相应温升。在这项研究中，开发了一种有效的搜索策略和计算模拟模型，以评估与骨科髋关节置换系统附近组织中诱导SAR相关的因素，并找到所有可能组合的“最差情况”峰值SAR。时域有限差分（FDTD）用于计算1.5 T和3 T MRI系统的美国材料与试验协会（ASTM）体模内典型髋关节置换系统的峰值SAR。结果表明，股骨柄和螺钉长度是影响两种场强（分别为1.5T/64 MHz和3 T/128 MHz）下峰值SAR的最重要因素。在64 MHz和128 MHz下，峰值1克平均SAR分别达到216 W/kg和103 W/kg。我们还发现，最短的股骨柄和最长的螺钉通常会引起更高的峰值SAR。
In this study we present numerical simulations of the Specific Absorption Rate (SAR) for multi-component orthopaedic hip replacement systems. The SAR is used to evaluate the radio frequency (RF)-induced heating of the devices during magnetic resonance imaging (MRI). Because multi-component orthopaedic hip replacement systems have many combinations of components with various designs and sizes, it is computationally intensive, and almost impossible, to evaluate the SAR and the corresponding temperature rise for each possible combination and configuration. In this study, an effective searching strategy and a computational simulation model are developed to evaluate the factors associated with induced SAR in the tissue near an orthopaedic hip replacement system, and to find the “worst case” peak SAR for all possible combinations. The finite-difference time-domain (FDTD) was used to calculate the peak SAR for a typical hip replacement system inside the American Society for Testing and Materials (ASTM) phantom for both 1.5 Tesla (T) and 3T MRI systems. The results indicate that the stem and screw lengths are the most important factors influencing the peak SAR for both field strengths, 1.5T/64 MHz and 3T/128 MHz, respectively. The peak 1 gram averaged SAR reaches 216 W/kg and 103 W/kg for 64 MHz and 128 MHz, respectively. We also found that shortest stems, and the longest screws, typically induce higher peak SAR.