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TH-EF-BRD-04: A Fast 4D IMRT/VMAT Planning Method Based On Segment Aperture Morphing. Med Phys 2015 Jun;42(6):3740



Pubmed ID



PURPOSE: To investigate dosimetric advantages of a 4D IMRT/VMAT planning method employing a segment aperture morphing (SAM) algorithm accounting for respiration-induced target motion and deformation. The minimal required number of calculated SAM phases was tested to minimize plan creation time.

METHODS: The new technique involves generating 4D step-and-shoot IMRT or VMAT plans based on 10-phase 4DCT in the following steps: (1) optimizing a flattening-filter-free IMRT/VMAT plan based on the 50% phase CT dataset (2) warping contours from the 50%-phase CT to the remaining phases via deformable image registration (DIR) and manual editing (3) morphing segment apertures of the 50%-phase plan to each phase CT using SAM that adjusts each aperture shape based on the change of the beam's-eye-view of the target contour between the two phases (4) calculating the dose distribution for each phase with the morphed apertures and same MUs as in the 50%-phase plan, and (5) generating the 4D plan by accumulating the dose from all nine SAM-corrected phases and the original 50% optimized phase using DIR. 4D plans based on 10, 7, 5 and 3 SAM-corrected phases were generated for representative lung and pancreatic cancer cases, and were compared using DVH analysis against the gold-standard 4D plan where all 10 phases are individually planned and optimized. A SAM-corrected 4D plan was also compared to a simpler phase-by-phase isocenter-shifted plan to assess accounting for tumor deformation and translation opposed to only tumor translation.

RESULTS: Plan DVH quality for the 10-phase and 7-phase 4D SAM plans were comparable with the fully-optimized 4D plans (PTV-D95's within 3% of fully-optimized plans). SAM based algorithms out-performed simpler isocenter-shifted-only approaches (∼1.5% PTV-D95 improvement). SAM-based 4D planning greatly reduces planning time verses individually optimized phase planning techniques.

CONCLUSION: SAM with DIR provides a fast and accurate way to create 4D IMRT/VMAT plans.

Author List

Klawikowski S, Tai A, Ates O, Ahunbay E, Li X


Ergun Ahunbay PhD Associate Professor in the Radiation Oncology department at Medical College of Wisconsin
An Tai PhD Associate Professor in the Radiation Oncology department at Medical College of Wisconsin

jenkins-FCD Prod-480 9a4deaf152b0b06dd18151814fff2e18f6c05280