Room: ePoster Forums
Purpose: The purpose was to evaluate the dosimetric impact of using multiple channel cylinder applicators instead of single channel applicators in high dose rate (HDR) vaginal cuff brachytherapy (VCBT)
Methods: Sample plans of HDR VCBT in a list of multiple channel cylinders at 2.5, 3.0 and 3.5 cm in diameter were created and analyzed. The doses were prescribed either at the 0.5cm depth with 5.5 Gy for 4 fractions or at the cylinder surface with 8.8 Gy for 4 fracÂ¬tions, in various treatment lengths ranging from 3 to 8 cm. A 0.5 cm cylindrical shell volume called PTV_Eval was contoured for each plan and served as the target volume for dosimetric evaluation. The same treatment lengths, same prescription regimens, same target volume contouring and plan evaluation methods were repeated for the similar size single channel cylinders. The dose volume histograms, mean doses (D-mean) and the doses covering 90% (D90), 10% (D10), and 5% (D5) of PTV_Eval were calculated and compared.
Results: Both the multiple and single channel cylinders have the same treatment target volumes. The D-means of the both regimens in the multi-channel cases were between 6.3 and 7.1 Gy, in single channel were between 6.4 to 7.5 Gy and dependent on the cylinder size but independent of the treatment length. The ranges of average D90, D10 and D5 were from 3.654 to 5.04 Gy, 8.44 to 10.08 Gy and 8.84 to 10.86 Gy in multi-channel, 5.36 to 5.76 Gy, 7.40 to 9.97 Gy and 8.16 to 11.93 Gy in single channel, respectively.
Conclusion: The multiple-channel cylinder will deliver less than 10% of mean dose than a single channel cylinder for the same cylindrical target volume. A 0.5 cm variation of diameter will result in a 2% change of D-mean in multiple channel but just 4 % for single channel.