A mathematical model to predict the different isodose volumes using TRAK value in HDR intracavitary brachytherapy for...

To find out the simple relationship between Total Reference Air Kerma (TRAK) and various isodose volumes. Calculated isodose volumes were compared with experimental data for revised Manchester and International Commission on Radiation Units and measurements (ICRU)-89 Point A-based treatment plans. The accuracy of the formula was compared with the results of other relationships available in the literature.

Dosimetric data from 62 intracavitary brachytherapy (ICBT) treatment plans of 31 patients with cervical cancer were studied. Each patient had treatment plans normalized to revised Manchester and ICRU-89 Points A (A_flange and A_icru89). For each treatment plan, TRAK values, V_350, V₇₀₀, V₁₀₅₀, and V₁₄₀₀ were obtained. The modeling curve was plotted between Isodose volume (V_d) and the ratio of d/TRAK obtained from A_flange plans to get a mathematical relation. The results of this formula were compared with the experimental data and outcomes of other formulas available in the literature. A paired-sample t-test was performed to assess the statistical significance.

In the case of revised Manchester-based A_flange normalization plans, the mean isodose volume of V₃₅₀, V₇₀₀, V_1050, and V₁₄₀₀ were 285.98 ± 32.3 cm³, 101.96 ± 10.63 cm³, 52.71 ± 4.72 cm³, and 31.44 ± 2.33 cm³ respectively. Likewise, for ICRU-89 based A_icru89 normalization plans, the mean isodose volumes of V₃₅₀, V₇₀₀, V_1050, and V₁₄₀₀ were 304.11 ± 26.17 cm³, 108.88 ± 8.29 cm³, 56.62 ± 3.69 cm³ and 34 ± 2.23 cm³ respectively. The mean difference was significant. The Mathematical relationship developed was [INLINE:1]. No correlation was found between TRAK and D_0.1cm³,D_2cm³ for organs at risk.

The developed formula calculated isodose volumes within the accuracy of ± 3% in ICBT plans.