Tracking tumor boundary using point correspondence for adaptive radio therapy

•This study addresses the problem of delineating mobile lung tumor regions for radiation therapy.•We propose two registration approaches to track the tumor regions: 1) First frame approach; and 2) Best frame approach.•We evaluated the proposed approaches over a sequence of 600 images acquired from 6 patients.•The best frame approach yielded an average Dice score of 0.89 ± 0.04 and Hausdorff distance of 3.38 ± 0.10 mm.•This study demonstrates a promising boundary tracking tool for delineating the tumor region for adaptive radiation therapy.