ESTRO 2022 - Abstract Book

S838

Abstract book

ESTRO 2022

Results On the level of PGI spot clusters, there is a significant correlation (r Pearson =0.3, p<0.01) between IDD and PGI range shifts over all 22 monitored fields (Fig.2B). The only moderate correlation is mainly due to statistical uncertainty of the clusters, represented by the mean absolute error between IDD and PGI range shifts of 3.4mm. The correlation might also be affected by difficult range shift determination due to spots traversing highly heterogeneous tissue. Despite the moderate correlation on cluster level, a field-wise classification, the main endpoint in our study, is possible with high detection sensitivity. Resulting from the training, a field was classified as relevantly changed if >12% of PGI clusters are relevant . The final model achieved a sensitivity of 80% (4/5) and a specificity of 67% (4/6) on the test cohort (Fig.2C).

Conclusion A first systematic investigation on the sensitivity of a PGI system to field-wise detect anatomical changes in clinical HNC PT treatments was performed using quantitative dose-based ground truth information from up-to-date control CTs. The capability of PGI to detect relevant anatomical changes with high sensitivity was demonstrated, which is essential for its clinical application, e.g. as treatment intervention system for online-adaptive PT. The now available evaluation workflow as well as the permanently growing PGI dataset from the ongoing clinical PGI study are a unique basis for follow-up studies.