Motion-weighted target volume and dose-volume histogram: A practical approximation of four-dimensional planning and evaluation |
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Authors: | Geoffrey ZhangVladimir Feygelman Tzung-Chi HuangCraig Stevens Weiqi LiThomas Dilling |
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Affiliation: | a Division of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA b Department of Medical Radiological Technology, China Medical University, Taiwan |
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Abstract: | Background and purposeIn ITV-based 3D-planning, the information of volume occupancy versus respiratory phase is not utilized. We propose a motion-weighted CTV (mwCTV) delineation method, which carries some 4D-information into planning. This method allows plan optimization based on occupancy-weighting and generation of motion-weighted DVH (mwDVH) that approximate the DVHs of full 4D-dose accumulation.Material and methodsOccupancy information from contours in 4D-CT is incorporated in the mwCTV generation. Higher-occupancy volumes receive higher dosimetric priority in planning. The temporally-weighted mwCTV is converted to a spatially-weighted mwCTV incorporating the temporal-weighting in mwDVH generation using the 3D-dose distribution. The mwDVHs were compared with DVHs of deformable-image-registration (DIR)-based 4D-dose accumulation and 3D-method for 10 cases.ResultsFor all the cases, the mwDVH curves are closer to the 4D-calculated DVH than the 3D-DVHs are, indicating a better approximation of the 4D-DVH. The 70 Gy-covered percentage-CTV volume differed by −2.8% ± 0.8% between 3D and 4D, and 0.3% ± 0.7% between mwDVH and 4D-methods. The mean RMS values of the percentage-volume differences for the 4D-3D is 1.7 ± 1.1, while for the 4D-mwDVH is 0.4 ± 0.3.ConclusionThe mwCTV and mwDVH method, which is simple in implementation and does not require DIR, is a practical approximation of DIR-based 4D-planning and evaluation. |
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Keywords: | 4D-treatment planning Dose-volume histogram Tumor motion Deformable image registration |
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