PT  - JOURNAL ARTICLE
AU  - Jacob Y. Hesterman
AU  - Susan D. Kost
AU  - Robert W. Holt
AU  - Howard Dobson
AU  - Ajay Verma
AU  - P. David Mozley
TI  - Three-Dimensional Dosimetry for Radiation Safety Estimates from Intrathecal Administration
AID  - 10.2967/jnumed.117.190611
DP  - 2017 Oct 01
TA  - Journal of Nuclear Medicine
PG  - 1672--1678
VI  - 58
IP  - 10
4099  - http://jnm.snmjournals.org/content/58/10/1672.short
4100  - http://jnm.snmjournals.org/content/58/10/1672.full
SO  - J Nucl Med2017 Oct 01; 58
AB  - 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.