Xiaodong Zhao1, Rui Zhang2. 1. Department of Physics and Astronomy, Louisiana State University, Baton Rouge, USA. 2. Department of Physics and Astronomy, Louisiana State University, Baton Rouge, USA; Department of Radiation Oncology, Mary Bird Perkins Cancer Center, Baton Rouge, USA. Electronic address: rzhang@lsu.edu.
Abstract
BACKGROUND: Local computed tomography (CT) reconstruction is achievable with portal images acquired during volumetric-modulated arc therapy (VMAT) delivery and was named as VMAT-CT. However, the application of VMAT-CT is limited because it has limited field of view and no density information. In addition, the new generation of multi-leaf collimator with faster speed and various collimator angles used in patients' plans could cause more artifacts in VMAT-CT. The goal of this study was to extend VMAT-CT concept, generate complete three-dimensional (3D) CT images, calculate new 3D dose, track and adapt VMAT plan based on updated images and dose. MATERIALS AND METHODS: VMAT-CT and planning CT of phantoms were fused by rigid or deformable registration to create VMAT-CT+ images. Trackings based on planning CT, VMAT-CT+, and cone beam CT (CBCT) were compared. When prescription dose was not met for planning target volume (PTV), re-planning was demonstrated on an in-house deformable phantom. Possible uncertainties were also evaluated. RESULTS: Tracking based on VMAT-CT+ was accurate and superior to those based on planning CT and CBCT since VMAT-CT+ can detect changes during treatment. PTV coverage in the deformable phantom decreased after deformations but went up and met the prescription goal after re-planning. The impact of uncertainties on dose was minimal. CONCLUSION: 3D tracking and adaptation of VMAT based on VMAT-CT are feasible. Our study has the potential to increase the confidence of beam delivery, catch and remedy errors during VMAT.
BACKGROUND: Local computed tomography (CT) reconstruction is achievable with portal images acquired during volumetric-modulated arc therapy (VMAT) delivery and was named as VMAT-CT. However, the application of VMAT-CT is limited because it has limited field of view and no density information. In addition, the new generation of multi-leaf collimator with faster speed and various collimator angles used in patients' plans could cause more artifacts in VMAT-CT. The goal of this study was to extend VMAT-CT concept, generate complete three-dimensional (3D) CT images, calculate new 3D dose, track and adapt VMAT plan based on updated images and dose. MATERIALS AND METHODS: VMAT-CT and planning CT of phantoms were fused by rigid or deformable registration to create VMAT-CT+ images. Trackings based on planning CT, VMAT-CT+, and cone beam CT (CBCT) were compared. When prescription dose was not met for planning target volume (PTV), re-planning was demonstrated on an in-house deformable phantom. Possible uncertainties were also evaluated. RESULTS: Tracking based on VMAT-CT+ was accurate and superior to those based on planning CT and CBCT since VMAT-CT+ can detect changes during treatment. PTV coverage in the deformable phantom decreased after deformations but went up and met the prescription goal after re-planning. The impact of uncertainties on dose was minimal. CONCLUSION: 3D tracking and adaptation of VMAT based on VMAT-CT are feasible. Our study has the potential to increase the confidence of beam delivery, catch and remedy errors during VMAT.
Authors: Dirk Verellen; Mark De Ridder; Nadine Linthout; Koen Tournel; Guy Soete; Guy Storme Journal: Nat Rev Cancer Date: 2007-12 Impact factor: 60.716
Authors: Fang-Fang Yin; Zhiheng Wang; Sua Yoo; Q Jackie Wu; John Kirkpatrick; Nicole Larrier; Jeffrey Meyer; Christopher G Willett; Lawrence B Marks Journal: Technol Cancer Res Treat Date: 2008-04