Intrathecal administration is of growing interest for drug delivery, and its utility is being increasingly investigated through imaging. In this work, the 3-dimensional Voxel-Based Internal Dosimetry Application (VIDA) and 4D Extended Cardiac Torso Phantom (XCAT) were extended to provide radiation safety estimates specific to intrathecal administration. Methods: The 3-dimensional VIDA dosimetry application Monte Carlo simulation was run using a modified XCAT phantom with additional and edited cerebrospinal fluid (CSF) regions to produce voxel-level absorbed dose per unit cumulated activity maps for 9 selected source regions. Simulation validation was performed to compare absorbed dose estimates for common organs in a preexisting dosimetry tool (OLINDA/EXM). Dynamic planar imaging data were acquired in 6 healthy subjects using administered volumes of 5 or 15 mL (n = 3 each) of 185 MBq of ^99mTc-diethylenetriaminepentaacetic acid. Absorbed dose was estimated for each subject using the intrathecal-specific dosimetry application. Results: Simulation results were within 6% of OLINDA estimates for common organs. Absorbed dose estimates were highest (0.3–0.8 mGy/MBq) in the lumbar CSF space. A whole-body effective dose estimate of 0.003 mSv/MBq was observed. An administered volume dependency was observed with a 15-mL volume, resulting in lower absorbed dose estimates for several intrathecal and nonintrathecal regions. Conclusion: The intrathecal-specific VIDA implementation enables tailored dosimetry estimation for regions most relevant in intrathecal administration. Absorbed doses are highly localized to CSF and spinal regions and should be taken into consideration when designing intrathecal imaging studies. A potentially interesting relationship was observed between absorbed dose and administered volume, which merits further investigation.

鞘内给药对于药物递送越来越引起人们的兴趣，并且其用途正在通过成像越来越多地进行研究。在这项工作中，扩展了3维基于体素的内部剂量测定应用程序（VIDA）和4D扩展心脏躯干体模（XCAT），以提供鞘内给药特有的辐射安全性评估。方法：3维VIDA剂量学应用程序Monte Carlo模拟是使用经过修改的XCAT体模进行的，该体模具有附加的和编辑的脑脊液（CSF）区域，以生成针对9个选定源区域的单位累积累积活动图的体素水平吸收剂量。进行了模拟验证，以比较预先存在的剂量测定工具（OLINDA / EXM）中常见器官的吸收剂量估算值。动态平面成像数据使用5或15毫升（施用体积在6名健康受试者获得的Ñ的185个活度= 3各自）^99米锝二亚乙基三酸。使用鞘内特异性剂量测定法估算每个受试者的吸收剂量。结果：模拟结果在普通器官的OLINDA估计值的6％以内。腰椎脑脊液空间的吸收剂量估计最高（0.3-0.8 mGy / MBq）。观察到全身有效剂量估计为0.003 mSv / MBq。观察到15 mL体积的给药体积依赖性，导致几个鞘内和非鞘内区域的吸收剂量估计较低。结论：鞘内特异性VIDA的实现使得鞘内给药最相关区域的定制剂量学估计成为可能。吸收剂量高度局限在CSF和脊柱区域，在设计鞘内成像研究时应予以考虑。在吸收剂量和给药量之间观察到潜在的有趣关系，值得进一步研究。