A Monte Carlo Study On Fetal Dose From Craniospinal Irradiation with Proton Pencil Beam Scanning Treatment
Y Yeom1*, K Griffin2, M Mille3, C Lee4, S O'Reilly5, L Dong6, J Jung7, C Lee8, (1) National Cancer Institute, Rockville, MD, (2) National Cancer Institute, Rockville, MD, (3) National Cancer Institute, Bethesda, MD, (4) University of Michigan, Ann Arbor, MI, (5) University of Pennsylvania, Philadelphia, PA, (6) University of Pennsylvania, Philadelphia, PA, (7) East Carolina Univ, Greenville, NC, (8) National Cancer Institute, Rockville, MD
Presentations
TU-IePD-TRACK 5-3 (Tuesday, 7/27/2021) 12:30 PM - 1:00 PM [Eastern Time (GMT-4)]
Purpose: To evaluate fetal dose from proton pencil beam scanning (PBS) craniospinal irradiation (CSI) during pregnancy by conducting Monte Carlo (MC) dose calculations coupled with eight gestational-age dependent pregnant female phantoms (8, 10, 15, 20, 25, 30, 35, and 38 weeks).
Methods: The pregnant phantoms were converted into DICOM-RT data (CT images and structures) and imported into a treatment planning system (TPS) (Eclipse v15.6) commissioned for an IBA PBS nozzle. From the TPS, a proton PBS CSI plan (prescribed dose: 36 Gy) was created on the phantoms. MC simulation of the proton PBS CSI to estimate fetal dose was conducted using the TOPAS MC code, for which MC beam properties at the nozzle exit (spot size, spot divergence, mean energy, and energy spread) as a function of the nominal energy were matched to the IBA PBS nozzle beam measurement data. We calculated organ/tissue-averaged absorbed doses for 28 fetal organs and tissues. For contextual purposes, the fetal organ/tissue doses from the treatment planning CT scan of the mother’s head and abdomen were also estimated by using the National Cancer Institute dosimetry system for CT (NCICT, Version 3) considering a low-dose CT protocol (CTDIvol: 8.97 mGy).
Results: The majority of the fetal organ/tissue doses from the proton PBS CSI onto the eight pregnant phantoms fell within a range from 3 to 6 mGy. The fetal doses from the proton PBS CSI were generally lower than those from the planning CT scan, which fell within a range from 7 to 13 mGy.
Conclusion: The organ/tissue doses produced from this comprehensive MC study provide one of the first clinically informative predictions on the magnitude of fetal dose during proton PBS CSI during pregnancy because most proton TPSs cannot estimate out-of-field fetal dose.
ePosters
Keywords
Not Applicable / None Entered.
Taxonomy
Not Applicable / None Entered.
Contact Email