Quantitative evaluation of the effect of anatomical changes on the results of in vivo dosimetry during radiation therapy in the thoracic region

EPID-based IVD detected reduced GPR values in replanning cases, identifying the 3%/3 mm criterion as optimal. A per-fraction GPR of < 97% under this criterion may indicate notable anatomical changes. Continuing treatment without replanning tended to increase doses delivered to the target and normal tissues. These findings support the clinical utility of IVD and provide quantitative criteria for replanning decisions beyond CT or contour-based assessments.