Three-dimensional radiobiologic dosimetry: Application of radiobiologic modeling to patient-specific 3-dimensional imaging-based internal dosimetry
Three-dimensional radiobiologic dosimetry: Application of radiobiologic modeling to patient-specific 3-dimensional imaging-based internal dosimetry
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DOI：
10.2967/jnumed.106.038000
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发表时间：
2007-06-01
影响因子：
9.3
通讯作者：
Sgouros, George
中科院分区：
文献类型：
--
作者：
Prideaux, Andrew R.;Song, Hong;Sgouros, George
传统上，基于肿瘤和基于患者特异性成像的剂量测定方法产生了肿瘤和正常器官的平均器官吸收剂量或空间剂量分布。在这项工作中，放射生物学建模被引入到生物学有效剂量和等效均匀剂量参数转换的吸收剂量的空间分布。该方法说明使用的数据从甲状腺癌患者治疗放射性碘。方法：使用三次配准SPECT/CT扫描生成放射性核素动力学（清除率）和累积活性的三维图像。提供累积的活性图像和相应的CT扫描作为基于EGSnrc的Monte Carlo计算的输入：累积的活性图像用于定义衰减的分布，并且从CT导出的衰减图像用于定义相应的空间组织密度和组成分布。率图像用于将空间吸收剂量分布转换为生物有效剂量分布，然后用于估计分割的感兴趣体积的单个等效均匀剂量。等效均匀剂量也直接由吸收剂量分布计算。结果如下：我们使用简单的模型验证的方法，比较剂量体积直方图与以前分析的临床病例，并给出平均吸收剂量，平均生物有效剂量，等效均匀剂量的一个说明性的情况下，一个弥漫性肺转移的儿童甲状腺癌患者。肿瘤的平均吸收剂量、平均生物有效剂量和等效均匀剂量分别为57.7、58.5和25.0戈伊。正常肺组织的相应值分别为9.5、9.8和8.3戈伊。结论：分析表明放射生物学建模对缓解预测的影响。肿瘤的等效剂量值降低57%反映了肿瘤中的高水平剂量不均匀性以及实现肿瘤缓解的相应可能性降低。这种分析预计将是有用的放射性核素治疗的治疗计划。
Phantom-based and patient-specific imaging-based dosimetry methodologies have traditionally yielded mean organ-absorbed doses or spatial dose distributions over tumors and normal organs. In this work, radiobiologic modeling is introduced to convert the spatial distribution of absorbed dose into biologically effective dose and equivalent uniform dose parameters. The methodology is illustrated using data from a thyroid cancer patient treated with radioiodine. Methods: Three registered SPECT/CT scans were used to generate 3-dimensional images of radionuclide kinetics (clearance rate) and cumulated activity. The cumulated activity image and corresponding CT scan were provided as input into an EGSnrc-based Monte Carlo calculation: The cumulated activity image was used to define the distribution of decays, and an attenuation image derived from CT was used to define the corresponding spatial tissue density and composition distribution. The rate images were used to convert the spatial absorbed dose distribution to a biologically effective dose distribution, which was then used to estimate a single equivalent uniform dose for segmented volumes of interest. Equivalent uniform dose was also calculated from the absorbed dose distribution directly. Results: We validate the method using simple models; compare the dose-volume histogram with a previously analyzed clinical case; and give the mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for an illustrative case of a pediatric thyroid cancer patient with diffuse lung metastases. The mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for the tumor were 57.7, 58.5, and 25.0 Gy, respectively. Corresponding values for normal lung tissue were 9.5, 9.8, and 8.3 Gy, respectively. Conclusion: The analysis demonstrates the impact of radiobiologic modeling on response prediction. The 57% reduction in the equivalent dose value for the tumor reflects a high level of dose nonuniformity in the tumor and a corresponding reduced likelihood of achieving a tumor response. Such analyses are expected to be useful in treatment planning for radionuclide therapy.