ESTRO 2024 - Abstract Book

S5906

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

Table 1: Planning goals for UHF treatment.

Results:

Data from 25 out of the 32 patients were available for dose calculation based on CBCT. In general, the delivered dose closely matched the planned dose for the bladder and rectum. In seven patients, rectal filling during treatment exceeded the pre-planned rectal filling. This increased rectal filling led to five cases exceeding one planning goal. This goal defined a maximum dose of 35 Gy to 2 cm 3 of the rectum volume. Figure 1 shows the dose deviation for these patients. However, for all other rectal constraints, rectal filling did not result in violation of planning goals. There was considerable variation in bladder filling among the patients, but the delivered dose did not exceed planning goals in any case. The use of CBCT for delineating the bladder and rectum is acknowledged as a limitation of the study. In some cases, the image quality was too poor to unambiguously distinguish the interface between the rectal wall and the prostate.