Background: With radiotherapy having entered the era of image guidance, or image-guided radiation therapy (IGRT), imaging procedures are routinely performed for patient positioning and target localization. The imaging dose delivered may result in excessive dose to sensitive organs and potentially increase the chance of secondary cancers and, therefore, needs to be managed. Aims: This task group was charged with: a) providing an overview on imaging dose, including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV-CT, megavoltage cone-beam CT (MV-CBCT) and kilovoltage cone-beam CT (kV-CBCT), and b) providing general guidelines for commissioning dose calculation methods and managing imaging dose to patients. Materials & Methods: We briefly review the dose to radiotherapy (RT) patients resulting from different image guidance procedures and list typical organ doses resulting from MV and kV image acquisition procedures. Results: We provide recommendations for managing the imaging dose, including different methods for its calculation, and techniques for reducing it. The recommended threshold beyond which imaging dose should be considered in the treatment planning process is 5% of the therapeutic target dose. Discussion: Although the imaging dose resulting from current kV acquisition procedures is generally below this threshold, the ALARA principle should always be applied in practice. Medical physicists should make radiation oncologists aware of the imaging doses delivered to patients under their care. Conclusion: Balancing ALARA with the requirement for effective target localization requires that imaging dose be managed based on the consideration of weighing risks and benefits to the patient.
Bibliographical noteFunding Information:
The members of this task group thank Greg Sharp (TISC Lead Reviewer), Ping Xia (TPC Lead Reviewer), Jeffrey Siebers (External Lead Reviewer), Jeff Colvin, and Sonja Dieterich for their very helpful comments and suggestions. We thank Gig Mageras and Debra Brinkmann for their helpful guidance over the years in which this report was developed. We also thank the referees for their very helpful and constructive comments. We wish to acknowledge the support from AAPM TPC leadership and extend our thanks to the science editor for the professional proof reading of this report. Finally, we want to thank our consultants: Walter Bosch, Jun Deng, Choonsik Lee, Peter Munro and Ying Xiao for their invaluable contributions to this report.
© 2018 American Association of Physicists in Medicine
- image dose management
- image dose reduction techniques
- image guidance doses
- recommended dose threshold