A 3-dimensional absorbed dose calculation method based on quantitative SPECT for radionuclide therapy: evaluation for (131)I using monte carlo simulation.
A 3-dimensional absorbed dose calculation method based on quantitative SPECT for radionuclide therapy: evaluation for (131)I using monte carlo simulation.
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发表时间：
2002-08
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通讯作者：
M. Ljungberg;K. Sjögreen;Xiaowei Liu;E. Frey;Y. Dewaraja;S. Strand
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作者：
M. Ljungberg;K. Sjögreen;Xiaowei Liu;E. Frey;Y. Dewaraja;S. Strand
未标记的一种通用方法是基于定量SPECT活性测量的患者特异性三维吸收剂量计算。方法计算方案包括一种将CT图像配准到SPECT图像的方法，以及作为迭代重建方法一部分执行的衰减、散射和准直器探测器响应的位置相关补偿。还包括一种基于EGS 4（电子-伽马簇射，第4版）蒙特卡罗代码将测得的放射性分布转换为三维吸收剂量分布的方法。活性定量和吸收剂量计算的准确性进行评估的基础上，现实的Monte Carlo模拟SPECT数据，使用SIMIND（模拟成像核探测器）程序和基于体素的计算机体模。从计算机体模获得CT图像，并且相对于SPECT图像添加真实的患者运动。基于SPECT的放射性浓度和吸收剂量分布与真实的。结果在准直器中可以对目标散射、光子衰减和散射穿透进行校正。然而，SPECT系统有限的空间分辨率造成了不准确性，准直器响应校正不能完全补偿。结论所提出的方法包括补偿大部分降低定量图像信息的参数。补偿方法基于物理模型，因此一般适用于其他放射性核素。拟议的评价方法可作为今后对不同方法进行相互比较的基础。
UNLABELLED A general method is presented for patient-specific 3-dimensional absorbed dose calculations based on quantitative SPECT activity measurements. METHODS The computational scheme includes a method for registration of the CT image to the SPECT image and position-dependent compensation for attenuation, scatter, and collimator detector response performed as part of an iterative reconstruction method. A method for conversion of the measured activity distribution to a 3-dimensional absorbed dose distribution, based on the EGS4 (electron-gamma shower, version 4) Monte Carlo code, is also included. The accuracy of the activity quantification and the absorbed dose calculation is evaluated on the basis of realistic Monte Carlo-simulated SPECT data, using the SIMIND (simulation of imaging nuclear detectors) program and a voxel-based computer phantom. CT images are obtained from the computer phantom, and realistic patient movements are added relative to the SPECT image. The SPECT-based activity concentration and absorbed dose distributions are compared with the true ones. RESULTS Correction could be made for object scatter, photon attenuation, and scatter penetration in the collimator. However, inaccuracies were imposed by the limited spatial resolution of the SPECT system, for which the collimator response correction did not fully compensate. CONCLUSION The presented method includes compensation for most parameters degrading the quantitative image information. The compensation methods are based on physical models and therefore are generally applicable to other radionuclides. The proposed evaluation methodology may be used as a basis for future intercomparison of different methods.