Dose-volume and radiobiological dependence on the calculation grid size in prostate VMAT planning

Journal Article · Sat Dec 15 04:00:00 EST 2018 · Medical Dosimetry

DOI:https://doi.org/10.1016/J.MEDDOS.2017.12.002· OSTI ID:22824216

Jiang, Runqing ^[1]

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1. Medical Physics Department, Grand River Regional Cancer Centre, Kitchener, ON N2G 1G3 (Canada)

This study evaluated the effects of dose-volume and radiobiological dependence on the calculation grid size in prostate volumetric-modulated arc therapy (VMAT) planning. Ten patients with prostate cancer were selected for this retrospective treatment planning study. Prostate VMAT plans were created for the patients using the 6 MV photon beam produced by a Varian TrueBEAM linac with the calculation grid size equal to 1, 2, 2.5, 3, 4, and 5 mm. Dose-volume histograms (DVHs) of targets and organs at risk were generated for different grid sizes. We calculated the radiobiological parameters of the tumor control probability (TCP) of clinical target volume (CTV) and planning target volume (PTV), and the normal tissue complication probability (NTCP) of organs at risk (rectal wall, rectum, bladder wall, bladder, left femur, and right femur). The homogeneity, conformity, and gradient indexes of CTV and PTV were calculated for different grid sizes. The TCP of PTV was found decreasing with a rate of 0.06%/mm when the calculation grid size increased from 1 to 5 mm. On the other hand, both NTCPs of rectal wall and rectum were found decreasing with rates of 0.03%/mm and 0.05%/mm, respectively, with an increase of grid size. The homogeneity index of PTV increased with a rate of 0.57/mm of the calculation grid size, whereas the conformity index of PTV decreased with a rate of 0.0075/mm. The gradient index of PTV was found increasing with a rate equal to 0.05/mm. In prostate VMAT planning, variations of dose-volume and radiobiological parameters with calculation grid size on PTV, rectal wall, and rectum were more significant than those of CTV and other organs at risk such as bladder wall, bladder, and femurs. Results in this study are important in the treatment planning quality assurance when the calculation grid size is varied to compromise a shorter dose computing time.

• OSTI ID: 22824216
• Journal Information: Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 4 Vol. 43; ISSN 0958-3947
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BLADDER
FEMUR
LINEAR ACCELERATORS
NEOPLASMS
PATIENTS
PHOTON BEAMS
PLANNING
PROSTATE
QUALITY ASSURANCE
RADIATION DOSES
RADIOTHERAPY
RECTUM