Analysis of Online and Offline Head and Neck Image-guided Radiation Therapy

The introduction of a daily image-guided radiation therapy (IGRT) program is an important step. It has implications for the radiation therapy team in terms of accuracy, workflow, and decision making. This study assesses how successful a radiation therapy department has been in using this technology and the accuracy of individual decision making when comparing online and offline image match data.

Twenty intensity-modulated radiation therapy head and neck patients had their IGRT data assessed retrospectively. Online analysis was completed based on a 0-mm action threshold. Offline analysis was then conducted on the same data. Any discrepancies in decision making were then assessed.

Results indicated that the treating radiation therapy team was able to image match consistently when benchmarked against their colleagues in the offline environment. Analysis of online versus offline corrections in each of the three orthogonal directions showed strong agreement. Further analysis revealed no statistically significant differences for systematic errors, whereas a statistically significant but small difference was present for random error.

In this age of sophisticated equipment, daily IGRT is a valuable modality. However, the introduction of daily online IGRT inclusive of a 0-mm action threshold for head and neck IGRT requires careful consideration and evidence that such accuracy can be achieved. Ultimately, it is still the radiation therapist who must make the decision, which places great importance on the competency of the treating radiation therapy team.