S2862
RTT - RTT education, training, and advanced practice
ESTRO 2026
was identified as the most common factor for re- imaging. Despite routine instructions for patients to empty their rectum before treatment, precise control of rectal volume remains unachievable due to inherent physiological limitations. Based on the results, an improved CBCT assessment protocol has been developed, accepting gas-distended rectum if it remains within the original rectum contour. The updated protocol is designed to decrease the frequency of re-imaging during CBCT evaluation. The clinical efficacy of this protocol will undergo evaluation in the immediate future. Overall, systematic auditing of re-imaging will provide an effective method for evaluating protocol performance and overall operational effectiveness. Keywords: Quality improvement, Gynecology, Image- guided References: 1) Chee D, Buckley L. Application of repeat image analysis to radiation therapy imaging modalities as a quality improvement tool for image guided radiotherapy. J Appl Clin Med Phys. 2023 Sep;24(9):e14019. doi:10.1002/acm2.14019. Epub 2023 May 4. PMID: 37143316; PMCID: PMC10476973.2) Jadon R, et al. A systematic review of dose-volume predictors and constraints for late bowel toxicity following pelvic radiotherapy. Radiat Oncol.2019 Apr 3;14(1):57.doi:10.1186/s13014-01912628. PMID: 30943992; PMCID: PMC6448293.3) Webster A, et al. Image-Guided Radiotherapy for Pelvic Cancers: A Review of Current Evidence and Clinical Utilisation. Clin Oncol (R Coll Radiol).2020Dec;32(12):805816.doi:10.1016/j.clon.2020 .09.010. Epub2020Oct16. PMID: 33071029. Semi-automated quantitative workflow for offline plan adaptation in head and neck radiotherapy C.C.H. Warmerdam, K.F. Crama, R. de Jong, M.A. de Jong, E.A. Onderwater, E. Astreinidou Radiotherapy, LUMC, Leiden, Netherlands Purpose/Objective: To evaluate the feasibility of a semi-automatic dosimetric workflow based on corrected CBCT (cCBCT) to support offline plan adaptation decision-making in head and neck cancer patients (HN), and to compare its performance with the standard qualitative contour- based clinical workflow. Material/Methods: Fifteen HN patients treated with VMAT and online CBCT between October 2021 and April 2025, who underwent offline plan adaptation during their 25–35 fraction treatment course, were analyzed. For each patient, the planning CT (pCT), repeat CT (rCT), and the Digital Poster 2171
Re-imaging factors were classified as setup error, incorrect bladder/rectal filling, internal anatomical changes, machine error, and others.Secondary analysis examining the dosimetric impact of rectal filling variation (original versus gas-distended rectums) was also conducted on 10 patients. To simulate a gas- distended rectum in the treatment plan, the original rectum was assigned to air density and recalculated. Two-tailed paired t-test (p<0.05) was used for statistical analysis. Results:
57% of the patient cohort required repeated CBCT during their treatment. The occurrence of re-imaging was 56% in the weekly CBCT group and 59% in the daily CBCT group, demonstrating that re-imaging is a significant clinical problem. Incorrect rectal filling contributed to the highest incidence of repeat CBCT (n=332, 54%) (Figure 1). Statistical analysis revealed significant differences in rectal dose parameters with air correction. Rectum Dmax increased from 50.95±3.20 Gy to 51.70±3.55 Gy (p= 0.018), and Dmean increased from 37.40±6.43 Gy to 37.92±6.40 Gy (p< 0.01) (Table 1). Despite statistical significance, the small incremental magnitude suggests they are clinically insignificant. Conclusion: Assessing re-imaging rates and their causes, help to identify improvements to reduce patient doses and enhance workflow efficiency. Incorrect rectal filling
Made with FlippingBook - Share PDF online