ESTRO 2023 - Abstract Book

S2093

Digital Posters

ESTRO 2023

Results The results of the test phase show that the DSC score was 7% higher on an average in the atlas that contained 30 CT-scans compared to the atlas containing 5 CT-scans. The mean DSC found in the internal cohort was 0,742 and in the external cohort 0,696. The visual check showed that 27% of the slices were perfectly generated, 58% of the slices needed some adjustments and 15% of the slices were incorrectly generated. The OAR’s that gave the highest DSC scores were the mandible and the oral cavity, the lowest was measured on the submandibular glands. Figure 1 shows the results on one patient of the generated structures by ABS and the manually drawn structures. The results of the test phase, the internal and external cohort and the visual checks are graphically drawn in figure 2. Manually contouring nine OAR’s per patient took 35 minutes on average. When using the ABS it took 20 minutes to generate and adapt the structures.

Figure 1 comparison manually drawn (red) and generated by atlas (yellow)

Figure 2 comparison between test phase, internal cohort, external cohort (DSC) and visual check (percentage perfect generated slices) Conclusion The structures generated by ABS bring a good starting point that only needs adjustments to us clinically. When using ABS it can save 15 minutes in the delineation process.

PO-2325 The relationship between contour agreement and dosimetric impacts in CBCT for prostate radiotherapy

H. Pang 1

1 Pamela Youde Nethersole Eastern Hospital, Clinical Oncology, Hong Kong, Hong Kong (SAR) China

Purpose or Objective Most of the treatment machine in use is incapable to visualize the instant dose distribution during online cone beam computed tomography (CBCT) review. The level of contour alignment is taken as a reference for the manual registration.