Variations in size specific effective dose with patient stature and beam width for kV cone beam CT imaging in radiotherapy

Colin John Martin, Abdullah Abuhaimed

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Facilities now available on linear accelerators for external beam radiotherapy enable radiation fields to be conformed to shapes of tumours with a high level of precision. However, in order for the treatment delivered to take advantage of this, the patient must be positioned on the couch with the same degree of accuracy. Kilovoltage cone beam computed tomography (CBCT) systems are now incorporated into radiotherapy linear accelerators to allow imaging to be performed at the time of treatment, and image guided radiation therapy (IGRT) is now standard in most radiotherapy departments throughout the world. However, because doses from imaging are much lower than therapy doses, less effort has been put into optimising radiological protection of imaging protocols. Standard imaging protocols supplied by the equipment vendor are often used with little adaptation to statures of individual patients, and exposure factors and field sizes are frequently larger than necessary. In this study, the impact of using standard protocols for imaging anatomical phantoms of varying size from a 193 adult phantom library has been evaluated. Monte Carlo simulations were used to calculate doses for organs and tissues for each phantom, and results combined in terms of size specific effective dose (SED). Values of SED from pelvic scans ranged from 11 mSv to 22 mSv for males and 8 mSv to 18 mSv for females, and for chest scans from 3.8 mSv to 7.6 mSv for males and 4.6 mSv to 9.5 mSv for females. Analysis of the results showed that if the same exposure parameters and field sizes are used, a person who is 5 cm shorter will receive a size specific effective dose that is 3% to 10% greater, while a person who is 10 kg lighter will receive a dose that is 10% to 14% greater as compared to the average size.
Original languageEnglish (US)
JournalJournal of Radiological Protection
StatePublished - Aug 2 2022
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: The authors would like to thank the National Cancer Institute of the National Institutes of Health (NIH) in the US for sharing the phantoms library used in this study, and the supercomputing lab at King Abdullah University of Science and Technology (KAUST) for their permission of performing all Monte Carlo simulations on the supercomputer (Shaheen). The authors also wish to thank the following participants in the ICRP Mentorship programme: Abdel-Hai Benali, Mario Djukelic, Sebastien Gros, María Cristina Plazas d’Leon, Yiannis Roussakis and Hossam Ragab Shaaban for their assistance in obtaining data on imaging practices in radiotherapy departments in their countries.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Waste Management and Disposal


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