Carcinoma of the uterine cervix: a 3D – CT analysis of dose to the internal, external and common iliac nodes in tandem and ovoid applications

Purpose: To describe external, internal and common iliac dose rates estimated with 3D-computed tomography (CT) based dose calculations in tandem and ovoid brachytherapy. Materials and methods: Thirty patients with carcinoma of the uterine cervix received low dose rate brachytherapy with a CT-compatible Fletcher–Suit–Deldos device. A total of 36 implants were performed with axial CT images used to identify internal iliac, external iliac, and common iliac vessels. Dose rates on the surfaces of these vessels were calculated for the purpose of estimating the dose to their associated lymph nodes. Results: In 22 out of 72 comparisons, point B overestimated the maximum dose with the external iliac nodes. In 21 out of 72 comparisons, point B overestimated the maximum dose with the internal iliac nodes. In all cases, Point B overestimated the minimum dose to the internal and external iliac nodal chains. Conclusion: It was found that Point B dose is similar to the maximum common iliac nodal dose. Patient to patient variability, of Point B dose, warrants further study of dose distributions to the nodal chains. The minimum dose to the external iliac nodal chain at the bifurcation of the nodal chains may provide a useful measure of 'pelvic side wall dose' and deserves further study to see if it can be correlated with pelvic side wall control and complications.