Balidemaj E, de Boer P, van Lier A L H M W, Remis R F, Stalpers L J A, Westerveld G H, Nederveen A J, van den Berg C A T, Crezee J
Radiotherapy, Academic Medical Center, Amsterdam, The Netherlands.
Phys Med Biol. 2016 Feb 21;61(4):1596-607. doi: 10.1088/0031-9155/61/4/1596. Epub 2016 Feb 2.
The in vivo electric conductivity (σ) values of tissue are essential for accurate electromagnetic simulations and specific absorption rate (SAR) assessment for applications such as thermal dose computations in hyperthermia. Currently used σ-values are mostly based on ex vivo measurements. In this study the conductivity of human muscle, bladder content and cervical tumors is acquired non-invasively in vivo using MRI. The conductivity of 20 cervical cancer patients was measured with the MR-based electric properties tomography method on a standard 3T MRI system. The average in vivo σ-value of muscle is 14% higher than currently used in human simulation models. The σ-value of bladder content is an order of magnitude higher than the value for bladder wall tissue that is used for the complete bladder in many models. Our findings are confirmed by various in vivo animal studies from the literature. In cervical tumors, the observed average conductivity was 13% higher than the literature value reported for cervical tissue. Considerable deviations were found for the electrical conductivity observed in this study and the commonly used values for SAR assessment, emphasizing the importance of acquiring in vivo conductivity for more accurate SAR assessment in various applications.
组织的体内电导率（σ）值对于诸如热疗中热剂量计算等应用的精确电磁模拟和比吸收率（SAR）评估至关重要。目前使用的σ值大多基于离体测量。在本研究中，利用磁共振成像（MRI）在体内非侵入性获取人体肌肉、膀胱内容物和宫颈肿瘤的电导率。在标准3T MRI系统上，采用基于磁共振的电特性断层扫描方法测量了20例宫颈癌患者的电导率。肌肉的体内平均σ值比目前人体模拟模型中使用的值高14%。膀胱内容物的σ值比许多模型中用于完整膀胱的膀胱壁组织的值高一个数量级。我们的发现得到了文献中各种体内动物研究的证实。在宫颈肿瘤中，观察到的平均电导率比文献报道的宫颈组织值高13%。本研究中观察到的电导率与SAR评估常用值之间存在相当大的偏差，这强调了获取体内电导率对于各种应用中更准确的SAR评估的重要性。
