Contents lists available at ScienceDirect Physica Medica journal homepage: www.elsevier.com/locate/ejmp Original paper An innovative gynecological HDR brachytherapy applicator system for treatment delivery and real-time verification Anna Romanyukha a , Mauro Carrara b, ⁎ , Davide Mazzeo c , Chiara Tenconi d , Tebarak Al-Salmani a , Joel Poder e , Dean Cutajar a , Iolanda Fuduli a , Marco Petasecca a , Joseph Bucci e , Annamaria Cerrotta f , Brigida Pappalardi f , Federica Piccolo f , Emanuele Pignoli b , Anatoly Rosenfeld a a Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia b Medical Physics Unit, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy c Department of Physics, Università degli Studi di Milano, Milan, Italy d Department of Oncology and Hemato-Oncology, Università degli Studi di Milano, Milan, Italy e St George Cancer Care Center, Kogarah, NSW, Australia f Radiation Oncology 2 Unit, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy ARTICLE INFO Keywords: HDR brachytherapy Multichannel vaginal applicator Source tracking Diodes In vivo treatment QA ABSTRACT The multichannel vaginal cylinder (MVC) applicator employed for gynecological high dose rate (HDR) bra- chytherapy increases dose delivery complexity, and thus makes the treatment more prone to errors. A quality assurance (QA) procedure tracking the source throughout dose delivery can detect dwell position and time errors in the multiple channels of the applicator. A new MVC system with integrated real time in vivo treatment delivery QA has been developed based on diodes embedded on the outer surface of the MVC. It has been pre-calibrated and verified using a non-clinical treatment plan with consecutive test positions and dwell times within each catheter, followed by the delivery of ten clinical plans of adjuvant vaginal cuff brachytherapy following hysterectomy for endometrial cancer. The non-clinical verification showed overall mean dwell position and time discrepancies between the nominal and measured treatment of -0.2 ± 0.5 mm and -0.1 ± 0.1 s (k = 1), respectively. The clinical plans showed mean positional discrepancies of 0.2 ± 0.4 and 0.0 ± 0.8 mm, for the central and peripheral catheters, re- spectively, and mean dwell time discrepancies of -0.1 ± 0.2 and -0.0 ± 0.1 s for central and peripheral catheters, respectively. The innovative prototype of the MVC system has shown the ability to track the source with sub-mm and sub- second accuracy, and demonstrated potential for its incorporation into the clinical routine. 1. Introduction The multichannel vaginal cylinder (MVC) applicator has been widely adopted in gynecological high dose rate (HDR) brachytherapy (BT) treatments. It has shown reductions in doses received by organs-at- risk, as compared to the single channel vaginal cylinder (SVC) appli- cator, without compromising the dose to the target. In fact, as com- pared to SVC the MVC geometry provides more degrees of freedom (i.e., the source is also dwelling in peripheral channels) to optimize the dose distribution for each patient [1–5]. The presence of multiple channels increases treatment complexity, and thus makes HDR treatments more prone to error. Errors can arise as a result of transfer tube misconnections, afterloader malfunction, and mistakes in afterloader calibration, among others, and thus affect source stepping distances, dwell times, and dwell positions within the applicator. Moreover, treatment errors often remain unknown due to a lack of real-time or post-treatment dose delivery verification in the current treatment flow [6,7]. Treatment verification is recommended in order to ensure optimal outcomes for the patient, and can be done by measuring or visualizing the HDR source during dose delivery either as a quality assurance (QA) procedure performed prior to treatment delivery, or for in vivo https://doi.org/10.1016/j.ejmp.2019.03.001 Received 3 December 2018; Received in revised form 27 February 2019; Accepted 1 March 2019 ⁎ Corresponding author at: Medical Physics Unit, Dept. of Diagnostic Imaging and Radiotherapy, Fondazione IRCCS Istituto Nazionale dei Tumori, Via Venezian, 1, 20133 Milano, Italy. E-mail address: mauro.carrara@istitutotumori.mi.it (M. Carrara). Physica Medica 59 (2019) 151–157 Available online 07 March 2019 1120-1797/ © 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved. T