Dosimetric evaluation study of IMRT and VMAT techniques for prostate cancer based on different multileaf collimator designs

Mohamed M Fathy; Belal Z Hassan; Reem H El-Gebaly; Maha H Mokhtar

doi:10.1007/s00411-022-01011-2

Dosimetric evaluation study of IMRT and VMAT techniques for prostate cancer based on different multileaf collimator designs

Radiat Environ Biophys. 2023 Mar;62(1):97-106. doi: 10.1007/s00411-022-01011-2. Epub 2022 Dec 28.

Authors

Mohamed M Fathy¹, Belal Z Hassan^{2

3}, Reem H El-Gebaly², Maha H Mokhtar⁴

Affiliations

¹ Department of Biophysics, Faculty of Science, Cairo University, Giza, Egypt. mfathy@sci.cu.edu.eg.
² Department of Biophysics, Faculty of Science, Cairo University, Giza, Egypt.
³ Department of Radiotherapy, Al-Ziraeyeen Hospital, Cairo University, Giza, Egypt.
⁴ Department of Radiotherapy and Nuclear Medicine, Medical Physics Unit, National Cancer Institute, Cairo University, Giza, Egypt.

Abstract

The hypofractionated radiotherapy modality was established to reduce treatment durations and enhance therapeutic efficiency, as compared to conventional fractionation treatment. However, this modality is challenging because of rigid dosimetric constraints. This study aimed to assess the impact of multi-leaf collimator (MLC) widths (10 mm and 5 mm) on plan quality during the treatment of prostate cancer. Additionally, this study aimed to investigate the impact of the MLC mode of energy on the Agility flattening filter (FF), MLC Agility-free flattening filter (FFF), and MLCi2 for patients receiving hypofractionated radiotherapy. Two radiotherapy techniques; Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Radiotherapy (VMAT), were used in this research. In the present study, computed tomography simulations of ten patients (six plans per patient) with localized prostate adenocarcinoma were analyzed. Various dosimetric parameters were assessed, including monitor units, treatment delivery times, conformity, and homogeneity indices. To evaluate the plan quality, dose-volume histograms (DVHs) were estimated for each technique. The results demonstrated that the determined dosimetric parameters of planning target volume (PTV)p (such as D mean, conformity, and homogeneity index) showed greater improvement with MLC Agility FF and MLC Agility FFF than with MLCi2. Additionally, the treatment delivery time was reduced in the MLC Agility FF (by 31%) and MLC Agility FFF (by 10.8%) groups compared to the MLCi2 group. It is concluded that for both the VMAT and IMRT techniques, the smaller width (5 mm) MLCs revealed better planning target volume coverage, improved the dosimetric parameters for PTV, reduced the treatment time, and met the constraints for OARs. It is therefore recommended to use 5 mm MLCs for hypofractionated prostate cancer treatment due to better target coverage and better protection of OARs.

Keywords: Flattening filter (FF); Free flattening filter (FFF); Intensity-modulated radiotherapy (IMRT); Multileaf collimator; Volumetric modulated arc therapy (VMAT).

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Humans
Male
Prostatic Neoplasms* / radiotherapy
Radiometry / methods
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Intensity-Modulated*