inviCRO, Boston, Massachusetts
Cleveland Clinic, Cleveland, Ohio.
J Nucl Med. 2017 Oct;58(10):1672-1678. doi: 10.2967/jnumed.117.190611. Epub 2017 Mar 23.
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. 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 ( = 3 each) of 185 MBq of Tc-diethylenetriaminepentaacetic acid. Absorbed dose was estimated for each subject using the intrathecal-specific dosimetry application. 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. 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.
鞘内给药在药物输送方面的应用越来越受到关注，其在影像学方面的应用也在不断得到研究。在这项工作中，三维基于体素的内部剂量测定应用程序 (VIDA) 和 4D 扩展心脏胸体模型 (XCAT) 得到扩展，以提供针对鞘内给药的特定辐射安全估计。使用带有额外编辑的脑脊液 (CSF) 区域的修改后的 XCAT 体模对三维 VIDA 剂量测定应用程序的蒙特卡罗模拟进行了运行，以生成 9 个选定源区域的每单位累积活度的体素水平吸收剂量图。进行了模拟验证，以比较现有剂量测定工具 (OLINDA/EXM) 中常见器官的吸收剂量估计值。使用 5 或 15 mL（= 3 个）体积的 185 MBq Tc-二乙三胺五乙酸，在 6 名健康受试者中采集了动态平面成像数据。使用鞘内特定剂量测定应用程序对每位受试者的吸收剂量进行了估计。模拟结果与 OLINDA 对常见器官的估计值相差在 6%以内。在腰椎 CSF 空间中的吸收剂量最高（0.3-0.8 mGy/MBq）。观察到全身有效剂量估计值为 0.003 mSv/MBq。观察到剂量体积依赖性，15 mL 体积导致几个鞘内和非鞘内区域的吸收剂量估计值较低。鞘内特异性 VIDA 实现使我们能够针对鞘内给药中最相关的区域进行定制剂量估计。吸收剂量高度局限于 CSF 和脊柱区域，在设计鞘内成像研究时应加以考虑。观察到吸收剂量与给药体积之间存在有趣的关系，值得进一步研究。
