Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.
J Nucl Med. 2010 Mar;51(3):471-6. doi: 10.2967/jnumed.109.070532.
Rodent species are widely used in the testing and approval of new radiopharmaceuticals, necessitating murine phantom models. As more therapy applications are being tested in animal models, calculating accurate dose estimates for the animals themselves becomes important to explain and control potential radiation toxicity or treatment efficacy. Historically, stylized and mathematically based models have been used for establishing doses to small animals. Recently, a series of anatomically realistic human phantoms was developed using body models based on nonuniform rational B-spline. Realistic digital mouse whole-body (MOBY) and rat whole-body (ROBY) phantoms were developed on the basis of the same NURBS technology and were used in this study to facilitate dose calculations in various species of rodents.
Voxel-based versions of scaled MOBY and ROBY models were used with the Vanderbilt multinode computing network (Advanced Computing Center for Research and Education), using geometry and tracking radiation transport codes to calculate specific absorbed fractions (SAFs) with internal photon and electron sources. Photon and electron SAFs were then calculated for relevant organs in all models.
The SAF results were compared with values from similar studies found in reference literature. Also, the SAFs were used with standardized decay data to develop dose factors to be used in radiation dose calculations. Representative plots were made of photon electron SAFs, evaluating the traditional assumption that all electron energy is absorbed in the source organs.
The organ masses in the MOBY and ROBY models are in reasonable agreement with models presented by other investigators noting that considerable variation can occur between reported masses. Results consistent with those found by other investigators show that absorbed fractions for electrons for organ self-irradiation were significantly less than 1.0 at energies above 0.5 MeV, as expected for many of these small-sized organs, and measurable cross-irradiation was observed for many organ pairs for high-energy electrons (as would be emitted by nuclides such as (32)P, (90)Y, or (188)Re).
啮齿动物种类广泛用于新放射性药物的测试和批准，因此需要建立鼠类模型。随着更多的治疗应用在动物模型中进行测试，准确计算动物自身的剂量估计变得非常重要，以便解释和控制潜在的辐射毒性或治疗效果。历史上，为小动物建立剂量使用了简化和基于数学的模型。最近，开发了一系列基于非均匀有理 B 样条的体模型的解剖学逼真的人体模型。在此基础上，使用相同的 NURBS 技术开发了逼真的数字鼠整体（MOBY）和鼠整体（ROBY）模型，并在本研究中用于促进各种啮齿动物的剂量计算。
使用比例缩放的 MOBY 和 ROBY 模型的体素版本，结合范德比尔特多节点计算网络（高级计算研究与教育中心），使用几何和跟踪辐射传输代码，计算内部光子和电子源的特定吸收分数（SAF）。然后，为所有模型中的相关器官计算光子和电子 SAF。
将 SAF 结果与参考文献中类似研究的结果进行比较。此外，还使用标准化的衰变数据计算剂量因子，用于辐射剂量计算。制作了光子电子 SAF 的代表性图，评估了所有电子能量都在源器官中吸收的传统假设。
MOBY 和 ROBY 模型中的器官质量与其他研究人员提出的模型基本一致，注意到报告的质量之间可能存在相当大的差异。与其他研究人员发现的结果一致，结果表明，对于许多这些小尺寸的器官，高于 0.5 MeV 的电子自照射的吸收分数明显小于 1.0，对于许多器官对高能电子的交叉照射也可以观察到（如（32）P、（90）Y 或（188）Re 等核素发射的电子）。
