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Coverage‐based treatment planning to accommodate deformable organ variations in prostate cancer treatment
Author(s) -
Xu Huijun,
Vile Douglas J.,
Sharma Manju,
Gordon J. James,
Siebers Jeffrey V.
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4894701
Subject(s) - radiation treatment planning , medicine , prostate cancer , prostate , percentile , coverage probability , margin (machine learning) , nuclear medicine , dosimetry , radiation therapy , cancer , radiology , mathematics , computer science , statistics , confidence interval , machine learning
Purpose: To compare two coverage‐based planning (CP) techniques with standard fixed margin‐based planning (FM), considering the dosimetric impact of interfraction deformable organ motion exclusively for high‐risk prostate treatments.Methods: Nineteen prostate cancer patients with 8–13 prostate CT images of each patient were used to model patient‐specific interfraction deformable organ changes. The model was based on the principal component analysis (PCA) method and was used to predict the patient geometries for virtual treatment course simulation. For each patient, an IMRT plan using zero margin on target structures, prostate (CTV prostate ) and seminal vesicles (CTV SV ), were created, then evaluated by simulating 1000 30‐fraction virtual treatment courses. Each fraction was prostate centroid aligned. Patients whose D 98 failed to achieve 95% coverage probability objective D 98,95 ≥ 78 Gy (CTV prostate ) or D 98,95 ≥ 66 Gy (CTV SV ) were replanned using planning techniques: (1) FM (PTV prostate = CTV prostate + 5 mm, PTV SV = CTV SV + 8 mm), (2) CP OM which optimized uniform PTV margins for CTV prostate and CTV SV to meet the coverage probability objective, and (3) CP COP which directly optimized coverage probability objectives for all structures of interest. These plans were intercompared by computing probabilistic metrics, including 5% and 95% percentile DVHs (pDVH) and TCP/NTCP distributions.Results: All patients were replanned using FM and two CP techniques. The selected margins used in FM failed to ensure target coverage for 8/19 patients. Twelve CP OM plans and seven CP COP plans were favored over the other plans by achieving desirable D 98,95 while sparing more normal tissues.Conclusions: Coverage‐based treatment planning techniques can produce better plans than FM, while relative advantages of CP OM and CP COP are patient‐specific.