S2916
RTT- RTT operational practice and workflow innovations
ESTRO 2026
workflows for pelvic sites. This study aimed to evaluate different options to introduce AI-enhanced IRIS reconstruction (Elekta) to improve CBCT image quality for online adaptive workflows [1]. Subsequently, the image quality of CBCT scans with and without IRIS reconstruction was retrospectively evaluated. Material/Methods: Two analyses were performed. Firstly, CBCT acquisition parameters were assessed to define the optimal parameters. Four presets were tested, of which the parameters are shown in figure 1. The AI- enhanced IRIS reconstruction algorithm (Elekta) was applied to all presets. The different presets were tested in four patients with a tumor in the pelvis. Image quality was assessed visually by a multidisciplinary team consisting of two medical physicists, one medical physics engineer, and two RTTs with specific training in image-guided radiotherapy (IGRT). Secondly, the added value of IRIS reconstruction was assessed for contour adaptation in an online adaptive workflow. In this assessment, CBCTs from patients with prostate (n=1), anus (n=1), rectum (n=3), and bladder (n=2) were reconstructed with and without IRIS and blindly presented to a group of three RTTs who delineate contours during an online adaptive workflow, and was shown to one physician. The image quality of both reconstructions were assessed using a 5-point scale [2]. Additionally, participants identified their preferred reconstruction for delineation within an adaptive workflow and commented on the appearance of artifacts in the reconstructions. Results: The multidisciplinary team found that medium- and high-dose CBCTs provided the best image quality in the central pelvis, despite increased rind artifacts at the body contour from the higher dose per frame. These presets are applied based on pelvic body size. The lower-speed preset caused more artifacts in moving air regions. Based on the observations, medium and high-dose images with IRIS reconstruction were selected for further evaluation in the online adaptive workflow. Results are presented in Figure 2. Artifact assessment showed that IRIS reconstructions contained the same artifacts as without IRIS, appearing more pronounced in 48% of cases.
marked sector-based inequities in RT capacity and access.
Conclusion: These findings will support the development of a strategic framework to strengthen RT capacity and reduce sector-based disparities. Ultimately, this evidence can guide policy and resource planning toward more equitable cancer care delivery in the country. References: Ramashia et al. Improving Access to Radiotherapy: Exploring Structural Quality Indicators for Radiotherapy in Gauteng Province, South Africa. Int J Environ Res Public Health. 2025 Apr 8;22(4):585. doi: 10.3390/ijerph22040585. Keywords: Radiotherapy access, quality indicators Digital Poster 2072 Assessment of IRIS reconstruction image quality in pelvic CBCT for online adaptive contouring Annelies J Zoetelief, Michael J Rijssel, Kim Verhoef, Gonda G Sikkes, Claudia M.C.W. Galama-Meester, Margriet Vriens, Martijn P.W. Intven, Gert J Meijer Radiotherapy, UMC Utrecht, Utrecht, Netherlands Purpose/Objective: Cone-beam CT (CBCT) image quality remains a limiting factor for accurate adaptation in online adaptive
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