SU‐E‐J‐119: Head‐And‐Neck Digital Phantoms for Geometric and Dosimetric Uncertainty Evaluation of CT‐CBCT Deformable Image Registration

TL;DRAbstract

Purpose: To evaluate geometric and dosimetric uncertainties of CT‐CBCT deformable image registration (DIR) algorithms using digital phantoms generated from real patients. Methods: We selected ten H&N cancer patients with adaptive IMRT. For each patient, a planning CT (CT1), a replanning CT (CT2), and a pretreatment CBCT (CBCT1) were used as the basis for digital phantom creation. Manually adjusted meshes were created for selected ROIs (e.g. PTVs, brainstem, spinal cord, mandible, and parotids) on CT1 and CT2. The mesh vertices were input into a thin‐plate spline algorithm to generate a reference displacement vector field (DVF). The reference DVF was applied to CBCT1 to create a simulated mid‐treatment CBCT (CBCT2). The CT‐CBCT digital phantom consisted of CT1 and CBCT2, which were linked by the reference DVF. Three DIR algorithms (Demons, B‐Spline, and intensity‐based) were applied to these ten digital phantoms. The images, ROIs, and volumetric doses were mapped from CT1 to CBCT2 u

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