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Inverse optimization of low‐cost kilovoltage x‐ray arc therapy plans
Author(s) -
Breitkreutz Dylan Y.,
Renaud MarcAndré,
Seuntjens Jan,
Weil Michael D.,
Zavgorodni Sergei,
BazalovaCarter Magdalena
Publication year - 2018
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 - 10.1002/mp.13153
Subject(s) - nuclear medicine , medicine , radiation treatment planning , prostate , dosimetry , radiation therapy , prostate cancer , medical physics , radiology , cancer
Purpose The objective of this work was to investigate the benefits of using inverse optimization treatment planning for kilovoltage arc therapy ( KVAT ) and to assess the dosimetric limitations of KVAT . Methods Monte Carlo ( MC ) calculated, inversely optimized KVAT plans of spherical, idealized breast, lung, and prostate lesions were calculated using the EGS nrc/ BEAM nrc and DOSXYZ nrc MC codes. The dose delivered with the KVAT system, which generates 200–225 kV photon beamlets, was calculated and inversely optimized using an optimization framework developed at McGill University. KVAT dose distributions were compared with inversely optimized and MC generated megavoltage ( MV ) volumetric modulated arc therapy ( VMAT ) plans as a reference. Prescription doses delivered to 95% of the planning target volume ( PTV ) were 38.5 (10 fractions), 60 (30 fractions) and 73.8 (41 fractions) Gy for the breast, lung and prostate patients, respectively. Dose distributions, dose volume histograms, and PTV homogeneity indices were used to evaluate KVAT and VMAT plans based on RTOG protocols. Results All organ‐at‐risk ( OAR ) doses were within prescribed dose limits for KVAT and VMAT plans. Generally, KVAT plans delivered higher doses to OAR s. For example, due to the lower energy of KVAT , 50% of the rib volume received 12.9 Gy from KVAT while only receiving 2.5 Gy from VMAT . OAR doses were especially high for the KVAT prostate plan due to the presence of large volumes of bony anatomy, which illustrates a limitation of the KVAT system. The KVAT treatment times per fraction for the breast, lung and prostate patients were 2.8, 2.6 and 5.5 min, respectively. Conclusions The inversely optimized KVAT plans presented in this work have demonstrated the ability of our novel low‐cost, kilovoltage x‐ray therapy system to safely treat deep‐seated spherical lesions in breast and lung patients while meeting RTOG dose constraints on OAR s.