Dosimetric verifi cation of the dose optimisation model used in endovascular brachytherapy, evaluation of the optimised dose distributions using elaborated indices.
BACKGROUND:
The equipment used for standard radiotherapy is used in vascular brachytherapy for prevention of restenosis after angioplasty.
MATERIAL AND METHOD: A paraffi n-wax phantom, thermoluminescent detectors and MD-55 Gafchromic ยฎ fi lms were used for dose measurements. The edge dose index (EDI), central dose index (CDI) and treatment length index (TLI) were introduced to compare dose distributions calculated and measured.
RESULTS: Obtained values (p>0.05) show no statistically signifi cant differences between calculated doses and measured doses. EDI values showed improvement in dose homogeneity on the edges of the application after optimisation. After optimisation CDI values from 0.9% to 1.6% for calculated and from -1.8% to 3.1% for measured showed improvement in dose homogeneity in the central part of the application. Observed values of TLI from 3% to 21% for calculated doses and from 7% to 24% for doses measured by Gafchromic ยฎ fi lms showed increase of RIL for optimised treatment plans.
CONCLUSIONS: 1/ The designed phantom allowed repeatable dosimetric verifi cation of dose distributions in endovascular brachytherapy. 2/ Measurements with thermoluminescent detectors and Gafchromic fi lms proved the accuracy of the calculation algorithm in endovascular brachytherapy conditions. 3/ Elaborated indices were found to be a useful tool in describing dose homogeneity. They allowed the process of optimisation to be controlled and thus an increase in dose homogeneity by 30% at the edges and by 7% in the middle of the treated volume to be achieved.