Skin dose measurement and estimating the dosimetric effect of applicator misplacement in gynecological brachytherapy: A patient and phantom study

Article type: Research Article

Authors: Majdaeen, Mehrsa^a | Dorri-Giv, Masoumeh^b | Olfat, Shaghayegh^c | Ataei, Gholamreza^d | Abedi-Firouzjah, Razzagh^e | Banaei, Amin^{f; *} | Ranjbar, Sahar^{g; *}

Affiliations: [a] Department of Radiotherapy and Oncology, Razi Hospital, Guilan University of Medical Sciences, Rasht, Iran | [b] Nuclear Medicine Research Center, Department of Nuclear Medicine, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran | [c] Department of Medical Radiation, Engineering Faculty, Central Tehran Branch, Islamic Azad University, Tehran, Iran | [d] Department of Radiology Technology, Faculty of Paramedical Sciences, Babol University of Medical Science, Babol, Iran | [e] Cellular and Molecular Research Center, Yasuj University of Medical Sciences, Yasuj, Iran | [f] Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran | [g] Department of Medical Physics and Engineering, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

Correspondence: [*] Corresponding authors: Amin Banaei, Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. E-mail: [email protected]; Sahar Ranjbar, Department of Medical Physics and Engineering, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. E-mail: [email protected].

Abstract: OBJECTIVES:To evaluate skin dose differences between TPS (treatment planning system) calculations and TLD (thermo-luminescent dosimeters) measurements along with the dosimetric effect of applicator misplacement for patients diagnosed with gynecological (GYN) cancers undergoing brachytherapy. METHODS:The skin doses were measured using TLDs attached in different locations on patients’ skin in pelvic regions (anterior, left, and right) for 20 patients, as well as on a phantom. In addition, the applicator surface dose was calculated with TLDs attached to the applicator. The measured doses were compared with TPS calculations to find TPS accuracy. For the phantom, different applicator shifts were applied to find the effect of applicator misplacement on the surface dose. RESULTS:The mean absolute dose differences between the TPS and TLDs results for anterior, left, and right points were 3.14±1.03, 6.25±1.88, and 6.20±1.97 %, respectively. The mean difference on the applicator surface was obtained 1.92±0.46 %. Applicator misplacements of 0.5, 2, and 4 cm (average of three locations) resulted in 9, 36, and 61%, dose errors respectively. CONCLUSIONS:The surface/skin differences between the calculations and measurements are higher in the left and right regions, which relate to the higher uncertainty of TPS dose calculation in these regions. Furthermore, applicator misplacements can result in high skin dose variations, therefore it can be an appropriate quality assurance method for future research.

Keywords: Brachytherapy, gynecologic cancers, TLD dosimetry, TPS accuracy

DOI: 10.3233/XST-210911

Journal: Journal of X-Ray Science and Technology, vol. 29, no. 5, pp. 917-929, 2021