Comprehensive Monte Carlo study of patient doses from cone-beam CT imaging in radiotherapy

Research output: Contribution to journalArticle


Accurate knowledge of ionizing radiation dose from cone-beam CT (CBCT)
imaging in radiotherapy is important to allow concomitant risks to be estimated
and for justification of imaging exposures. This study uses a Monte Carlo
CBCT model to calculate imaging dose for a wide range of imaging protocols
for male and female patients. The Elekta XVI CBCT system was modeled
using GATE and simulated doses were validated against measurements in a
water tank and thorax phantom. Imaging dose was simulated in the male and
female ICRP voxel phantoms for a variety of anatomical sites and imager
settings (different collimators, filters, full and partial rotation). The resulting
dose distributions were used to calculate effective doses for each scan protocol.
The Monte Carlo simulated doses agree with validation measurements within
5% and 10% for water tank and thorax phantom respectively. Effective dose
for head CBCT scans was generally lower for scans centred on the pituitary
than the larynx (0.03 mSv versus 0.06 mSv for male ICRP phantom). Pelvis
CBCT scan effective dose was higher for the female than male phantom
(5.11 mSv versus 2.80 mSv for M15 collimator scan), principally due to the
higher dose received by gonads for the female scan. Medium field of view
thorax scan effective doses ranged from 1.38 – 3.19 mSv depending on scan
length and phantom sex. Effective dose for half rotation thorax scans with
offset isocentre varied by almost a factor of three depending on laterality of
the isocentre, patient sex and imaged field length. The CBCT imaging doses
simulated here reveal large variations in dose depending on imaging isocentre

Bibliographical metadata

Original languageEnglish
Pages (from-to)13-30
Number of pages17
JournalJournal of Radiological Protection
Issue number1
Publication statusPublished - 6 Dec 2016