Volumetric (3D) bladder dose parameters are more reproducible than point (2D) dose parameters in vaginal vault high-dose-rate brachytherapy

Lucas Gomes Sapienza, Adriana Flosi, Antonio Aiza, Antonio Cassio de Assis Pellizzon, Rubens Chojniak, Glauco Baiocchi, Lucas Gomes Sapienza, Adriana Flosi, Antonio Aiza, Antonio Cassio de Assis Pellizzon, Rubens Chojniak, Glauco Baiocchi

Abstract

There is no consensus on the use of computed tomography in vaginal cuff brachytherapy (VCB) planning. The purpose of this study was to prospectively determine the reproducibility of point bladder dose parameters (DICRU and maximum dose), compared with volumetric-based parameters. Twenty-two patients who were treated with high-dose-rate (HDR) VCB underwent simulation by computed tomography (CT-scan) with a Foley catheter at standard tension (position A) and extra tension (position B). CT-scan determined the bladder ICRU dose point in both positions and compared the displacement and recorded dose. Volumetric parameters (D0.1cc, D1.0cc, D2.0cc, D4.0cc and D50%) and point dose parameters were compared. The average spatial shift in ICRU dose point in the vertical, longitudinal and lateral directions was 2.91 mm (range: 0.10-9.00), 12.04 mm (range: 4.50-24.50) and 2.65 mm (range: 0.60-8.80), respectively. The DICRU ratio for positions A and B was 1.64 (p < 0.001). Moreover, a decrease in Dmax was observed (p = 0.016). Tension level of the urinary catheter did not affect the volumetric parameters. Our data suggest that point parameters (DICRU and Dmax) are not reproducible and are not the ideal choice for dose reporting.

Figures

Figure 1. 3D scatterplot of catheter spatial…
Figure 1. 3D scatterplot of catheter spatial displacement between positions A and B.
Figure 2
Figure 2
(a) Sagittal view of the fused planning CT scan at both tension levels: standard (position A, green arrow) and extra tension (position B, red arrow). (b) Bladder reference point identified at the center of the balloon on a coronal plane (blue arrow). (c) Digitally reconstructed radiograph (DRR) from the CT scan in position A.

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Source: PubMed

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