RESUMEN
BACKGROUND AND PURPOSE: In adaptive radiotherapy, deformable image registration (DIR) is used to propagate delineations of tumors and organs into a new therapy plan and to calculate the accumulated total dose. Many DIR accuracy metrics have been proposed. An alternative proposed here could be a local uncertainty (LU) metric for DIR results. MATERIALS AND METHODS: The LU represented the uncertainty of each DIR position and was focused on deformation evaluation in uniformly-dense regions. Four cases demonstrated LU calculations: two head and neck cancer cases, a lung cancer case, and a prostate cancer case. Each underwent two CT examinations for radiotherapy planning. RESULTS: LU maps were calculated from each DIR of the clinical cases. Reduced fat regions had LUs of 4.6⯱â¯0.9â¯mm, 4.8⯱â¯1.0â¯mm, and 4.5⯱â¯0.7â¯mm, while the shrunken left parotid gland had a LU of 4.1⯱â¯0.8â¯mm and the shrunken lung tumor had a LU of 3.7⯱â¯0.7â¯mm. The bowels in the pelvic region had a LU of 10.2⯱â¯3.7â¯mm. LU histograms for the cases were similar and 99% of the voxels had a LUâ¯<â¯3â¯mm. CONCLUSIONS: LU is a new uncertainty metric for DIR that was demonstrated for clinical cases. It had a tolerance of <3â¯mm.