In vivo dosimetry of 3D gynecological brachytherapy using the glass dosimeter: a phantom study

Abstract

Brachytherapy can deliver high doses to the target while sparing healthy tissues due to its steep dose gradient property. However, treatment was only performed according to the dose calculated by a treatment planning system without verification of the dose due to the characteristics. Therefore, the aim of this study was to design the in-house phantom to evaluate the dosimetric differences of gynecological brachytherapy under clinical conditions between calculation by the treatment planning system and measurement by the RPLGDs. An in-house phantom consisting of the glass dosimeter holder and the holder of the applicator was created. This holder was designed to move the axis of the holder to apply the rectum point that differs according to the patient's anatomy. In addition, the holder of the applicator was designed for application in various types of applicators in intracavitary brachytherapy. The clinical study was used to quantify variations between the calculated and measured dose for 6 cases at various points in the phantom, which included point A, point B, bladder point, and rectum points. The mean dose difference between the calculated and measured dose at point A was 1.99%, the bladder point was 4.42%, and the rectum point was 3.53%. All values were within 5% of the acceptable reference value agreement. For the low dose at point B, the measured dose differs from the calculated dose of about 0.1 Gy. We consider that in-vivo dosimetry in the in-house phantom using the RPLGD for brachytherapy can minimize overdoses and, estimate the real delivered dose for the patient’s record using an accessory for the applicator in clinical practice.