ESTRO 2025 - Abstract Book

S4094

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

treatment from the CT scan. This can affect the breathing threshold position, and the patient may be required to take a deeper or lesser breath-hold than what was originally planned. The aim of this study was to improve reproducibility and accuracy of the RB placement between CT and treatment by creating 3D printed wedges. As well as reducing material waste from the gauze. Material/Methods: A survey was distributed to assess radiographer experience of the gauze. It was found that 20% found it “very difficult” to place the gauze. 65% thought they could not accurately replicate the position of gauze inter fractionally. 70% reported they were required to re-position the gauze or block once the gating system was started. To overcome these uncertainties, four wedges were designed and 3D printed to replicate the angles achieved from the gauze (figure 1).

Each set of wedges included 5, 10, 15 and 20mm wedge, with the wedge depth embossed onto the surface (figure 2). Each wedge was printed using the departments Ultimaker S7 3D printer using PLA Tough filament.

Results: Radiographer feedback found that 87.5% reported that they found accurate positioning the wedge “Very Easy” or “Easy” under the RB. 100% thought they were able to accurately replicate the wedge position inter-fractionally. 81.25% did not have to re-setup the wedge after the gating system had started, the responders that answered “Yes” reported this was due to the RPM system being unable to detect the RB. No gauze has been used with any 4D or DIBH patients at CT or treatment since the introduction of the wedges. No wedges have broken or needed to be re-printed. Conclusion: The 3D printed wedges have improved reproducibility, accuracy and efficiency of the RB placement between CT and treatment. In addition, they have reduced material waste of the gauze.

Keywords: 3D printing, DIBH, gating

References: [1] Varian (2021) RPM Respiratory Gating System Instruction for Use. Published in Switzerland.