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Updated: May 2, 2026
Author Spotlight: Improving Radiation Therapy Access with Radiation Planning Assistant
Published on: October 6, 2023
Combined online and offline adaptive radiation therapy: a dosimetric feasibility study
Chengliang Yang1, Feng Liu2, Ergun Ahunbay2
1Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin; Henan Cancer Hospital, Zhengzhou University, Zhengzhou, China.
Purpose:
The purpose of this work is to explore a new adaptive radiation therapy (ART) strategy, combined "online and offline" ART, that can fully account for interfraction variations similar to the existing online ART but with substantially reduced online effort.
Methods And Materials:
The concept for the combined ART is to perform online ART only for the fractions with obvious interfraction variations and to deliver the ART plan for that online fraction as well as the subsequent fractions until the next online fraction needs to be adapted. To demonstrate the idea, the daily computed tomographic (CT) data acquired during image guided radiation therapy (IGRT) with an in-room CT (CTVision, Siemens Healthcare, Amarillo, TX) for 6 representative patients (including 2 prostate, 1 head-and-neck, and 1 pancreatic cancer, 1 adrenal carcinoma, and 1 craniopharyngioma patients) were analyzed. Three types of plans were generated based on the following selected daily CTs: (1) IGRT repositioning plan, generated by applying the repositioning shifts to the original plan (representing the current IGRT practice); (2) Re-Opt plan, generated with full-scope optimization; and (3) ART plan, either online ART plan generated with an online ART tool (RealArt, Prowess Inc, Concord, CA) or offline ART plan generated with shifts from the online ART plan. Various dose-volume parameters were compared with measure dosimetric benefits of the ART plans based on daily dose distributions and the cumulative dose maps obtained with deformable image registration.
Results:
In general, for all the cases studied, the ART (with 3-5 online ART) and Re-Opt plans provide comparable plan quality and offer significantly better target coverage and normal tissue sparing when compared with the repositioning plans. This improvement is statistically significant.
Conclusions:
The combined online and offline ART is dosimetrically equivalent to the online ART but with substantially reduced online effort, and enables immediate delivery of the adaptive plan when an obvious anatomic change is observed.
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