Film based verification of calculation algorithms used for brachytherapy planning-getting ready for upcoming challenges of MBDCA

Abstract

PurposeWell-known defect of TG-43 based algorithms used in brachytherapy is a lack of information about interaction cross-sections, which are determined not only by electron density but also by atomic number. TG-186 recommendations with using of MBDCA (model-based dose calculation algorithm), accurate tissues segmentation, and the structure's elemental composition continue to create difficulties in brachytherapy dosimetry. For the clinical use of new algorithms, it is necessary to introduce reliable and repeatable methods of treatment planning systems (TPS) verification. The aim of this study is the verification of calculation algorithm used in TPS for shielded vaginal applicators as well as developing verification procedures for current and further use, based on the film dosimetry method.Material and methodsCalibration data was collected by separately irradiating 14 sheets of Gafchromic® EBT films with the doses from 0.25 Gy to 8.0 Gy using HDR 192Ir source. Standard vaginal cylinders of three diameters were used in the water phantom. Measurements were performed without any shields and with three shields combination. Gamma analyses were performed using the VeriSoft® package.ResultsCalibration curve was determined as third-degree polynomial type. For all used diameters of unshielded cylinder and for all shields combinations, Gamma analysis were performed and showed that over 90% of analyzed points meets Gamma criteria (3%, 3 mm).ConclusionsGamma analysis showed good agreement between dose distributions calculated using TPS and measured by Gafchromic films, thus showing the viability of using film dosimetry in brachytherapy.

Comprehensive methodology for commissioning modern 3D-image-based treatment planning systems for high dose rate gynaecological brachytherapy: A review

“…Table 1 highlights the need for developing a single comprehensive template to cover all the required items. Also, several studies argue for the importance of developing a comprehensive template for commissioning 3D-image-based TPSs in HDR GYN BT [4,26,[28][29][30]51,58]. In particular, this paper presents the first comprehensive template for verifying optimization routines and DVH-based parameters in BT TPSs.…”

“…Inhomogeneity modelling accuracy: Verifies that the TPS models the inhomogeneities in GYN cases and modifies the dose distributions according to the attenuation/scattering properties of these inhomogeneities (especially applicators and shields) [10,19,26,27,30,[53][54][55]. This test is particularly important for the applicators and shields in GYN cases.…”

“…It, however, does not include protocols for non-dosimetric aspects. Since then, a number of research groups have reported on the verification of the AAPM TG-43 parameters [20][21][22][23][24][25] and model-based TPSs [26][27][28][29][30], while focusing on the dose calculation aspect.…”

Quality assurance procedures based on dosimetric, gamma analysis as a fast reliable tool for commissioning brachytherapy treatment planning systems

“…Then the calibration curve was prepared and used recalculate the optical density (analog to digital conversion value; ADC) to the doses. 17 …”

Systematic Review of Intensity-Modulated Brachytherapy (IMBT): Static and Dynamic Techniques

“…"Static" IMBT approaches include those in which the shield does not move relative to the source or surrounding tissues during BT delivery, such as shielded applicators (eg, shielded cylinders, [3][4][5][6][7][8][9][10][11] shielded tandem and ovoids, [12][13][14][15][16][17][18][19][20] Strut-Adjusted Volume Implants [SAVI], 21 intracavitary mold applicators [ICMA], [22][23][24][25][26] direction-modulated brachytherapy [DirMBT], 21,25,[27][28][29][30][31][32][33][34] and cup or D-shaped applicators [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]…”