ESTRO 2025 - Abstract Book

S4038

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

ESTRO 2025

Results: Three liver SABR patients have been scanned using this protocol with varying image quality. Despite the same protocol used for all patients, IVC enhancement has been inconsistent. Patients included had a wide range of BMI. This may have contributed to the differences in scan quality as contrast volumes are not adjusted by patient weight in this centre. One of the main challenges in this process is performing the portal venous phase within the required time. The patient must be coached into EEBH prior to the portal venous scan being acquired. This is highly dependent on patient compliance and the radiation therapists ability to work at a quick pace while ensuring patient safety. The accuracy of the EEBH is paramount for reproducibility of treatment. Conclusion: Although there have been challenges due to the complexity of this technique, over-all it has been successful. All patients completed liver SABR treatment with no repeat CT-simulations required. The introduction of bolus tracking technology to individualise IV contrast delays is being considered. In addition to this, adjustment of IVC volume based on patient weight may improve scan quality 3 . References: 1.Beddar AS, Briere TM, Balter P, Pan T, et al. 4D-CT imaging with synchronized intravenous contrast injection to improve delineation of liver tumors for treatment planning. Radiotherapy and Oncology.2008 Jun;87(3):445– 8.doi:10.1016/j.radonc.2007.12.009 2. Murphy A. Four-Phase liver protocol (CT).Radiopaedia.org. 2021 Nov 13; doi:10.53347/rid-94731 involves a non contrast,phase and delayed phase acquisition. 3. Jensen C,Blair K, Wagner-Bartak, et al. Comparison of abdominal computed tomographic enhancement and organ lesion depiction between weight-based scanner software contrast dosing and a fixed-dose protocol in a tertiary care oncologic center. Journal of Computer Assisted Tomography.2019 Jan;43(1):155– 62.doi:10.1097/rct.0000000000000789 Digital Poster Prostate cancer radiotherapy with electromagnetic tracking: the first experience of application Darya Mychko, Halina Kastsiakhina, Maria Laptseva, Anna Pumpur, Stanislau Siamkouski, Mikita Shautsou Radiotherapy Department, Minsk City Clinical Oncology Center, Minsk, Belarus Purpose/Objective: The study aims to assess treatment tolerance in the low and intermediate risk prostate cancer (PCa) patients, underwent stereotactic beam radiotherapy (SBRT) using electromagnetic transmitter-based positioning system (ETBPS). Material/Methods: The prospective study enrolled the first 17 PCa patients completed SBRT in the Minsk City Clinical Oncology Center. Indications of SBRT were histologically confirmed low and intermediate risk PCa with a prostate volume of less than 80 ml, bladder volume at least 100 ml, Karnofsky performance status at least 70%. In cases of urethral stricture, sings of urinary retention, a history of transurethral prostate resection and pelvic RT, severe urinary disorders, nonspecific inflammatory bowel diseases SBRT was rejected. 5 daily SBRT fractions with single dose of 7–7.25 Gy were used. Patients’ positioning accuracy was controlled with cone beam CT (CBCT) performed before each RT procedure and target displacement was tracked during the RT session in a real time with ETBPS. Keywords: SGRT, breath hold, motion management 146