Dosimetric comparison of artificial walls of bladder and rectum with real walls in common prostate IMRT techniques: Patient and Monte Carlo study

Article type: Research Article

Authors: Gorji, Kourosh Ebrahimnejad^a | Sadat-Mirkazemi, Maryam^b | Banaei, Amin^{c; d; *} | Abedi-Firouzjah, Razzagh^a | Afkhami-Ardekani, Mahdieh^{e; *} | Ataei, Gholamreza^f

Affiliations: [a] Department of Medical Physics Radiobiology and Radiation Protection, School of Medicine, Babol University of Medical Sciences, Babol, Iran | [b] Student Research Committee, Babol University of Medical Sciences, Babol, Iran | [c] Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran | [d] Department of Radiology, Faculty of Paramedical Sciences, AJA University of Medical Sciences, Tehran, Iran | [e] Department of Radiology, Faculty of Paramedicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran | [f] Department of Radiology Technology, Faculty of Paramedical Sciences, Babol University of Medical Science, Babol, Iran

Correspondence: [*] Corresponding authors: Amin Banaei, Ph.D., Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Al-Ahmad and Chamran Cross, Tehran 1411713116, Iran. Tel.: +98 21 43822449; Fax: +98 2144338293; E-mail: [email protected] and Mahdieh Afkhami-Ardekani, M.Sc., Department of Radiology, Faculty of Paramedicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran. Tel.: +98 9126496216; Fax: +98 21 66466383; E-mail: [email protected].

Abstract: BACKGROUND:Rectum and bladder are hallow structures and considered as critical organs in prostate cancer intensity modulated radiotherapy (IMRT). Therefore, dose received by these organ walls must be considered for prediction of radiobiological effects. Contouring the real organ walls is quite difficult and time consuming in CT/MRI images, so the easy contouring artificial walls with uniform thickness could be appropriated alternatives. OBJECTIVE:To compare reconstructed artificial walls with real walls of bladder and rectum in common prostate IMRT techniques based on dose volume-histograms (DVHs) derived from artificial and real walls. METHODS:Artificial walls were reconstructed with 2–10 mm and 2–8 mm thicknesses for bladder and rectum, respectively. Four common IMRT techniques were applied to each patient. Spearman correlation was used to find the relation between the DVHs of true walls with artificial walls and whole organs. Monte Carlo (MC) simulations of the IMRT techniques and dosimetric comparison were also performed on a standard patient data. RESULTS:The 2 mm thickness artificial walls showed the minimum differences with the true bladder and rectum walls based on absolute evaluations (the maximum difference < 10cc and standard deviation < 15cc). However, relative evaluations showed that all the artificial walls had high correlations with real walls for selecting dose volume parameters. There was also good agreement between the treatment planning system and MC simulations results. CONCLUSION:The DVH of whole organs was not a good surrogate of the true wall. The 2 mm artificial walls can be regarded as good alternatives for both of rectum and bladder. However, in relative dose evaluations all studied artificial walls were appropriate.

Keywords: Prostate cancer, intensity modulated radiotherapy, bladder wall, rectum wall, Monte Carlo simulation

DOI: 10.3233/XST-190592

Journal: Journal of X-Ray Science and Technology, vol. 28, no. 1, pp. 59-70, 2020