ESTRO 2021 Abstract Book

S370

ESTRO 2021

Conclusion The agreement between measured and simulated RP fields suggests the suitability of sCTs for proton dose calculations. This outcome brings sCTs generated by DCNNs closer towards clinical implementation within adaptive proton therapy treatment workflows. The proposed RP quality control tool allows for CT number accuracy assessment in sCTs.

Symposium: Innovations in radiotherapy practice

SP-0481 SBRT in cardiac diseases: The evolving role of the RTT K. Pilling 1 1 Newcastle Upon Tyne Hospitals NHS Foundation Trust, Northern Centre for Cancer Care, Newcastle upon Tyne, United Kingdom Abstract Text Recent evidence suggests that SABR may have an emerging role in the treatment of patients with abnormal heart rhythms, Ventricular Tachycardia (VT), a non-malignant condition with high mortality. Using SABR to treat VT represents a novel treatment alternative for cardiac patients too sick for invasive treatments or in whom conventional therapies, including invasive cardiac catheter ablation, have failed. This is the first completely non-invasive therapy for cardiac arrhythmias and could reduce procedure times for patients from up to 8 hours down to around 45 minutes, without risk of general anaesthesia or invasive ablation procedures. Key clinical staff attended the 1st SNORAD meeting (Symposium for non-invasive radioablation) held in St Louis 2017. In addition to bringing back a better understanding of the process they made an arrangement whereby the St Louis team would provide peer review for patient selection and treatment planning. Pivotal to the introduction of cardiac SABR was the establishment of a MDT group. This consisted of physicists, oncologists, cardiologists, dosimetrists, radiographers and radiologists able to consider all aspects of setting up the service. This involved a steep learning curve for all professionals having to step into another highly complex discipline outside of their own area of expertise. As a consequence of the MDT approach, Radiographers played a key role in in the discussions within the MDT, looking at patient positioning/immobilisation, pre- treatment and treatment imaging and patient information. These patients have been through some unpleasant treatments and radiotherapy is a new and unknown concept, therefore radiographer presence at patient consent was considered essential. Whilst the Oncologist goes through the formal consent process discussing risks etc with the patient the radiographer role was to explain the practicalities of treatment. For patients without an oncology background the non-invasive nature of radiotherapy required explanation and prompted many questions. Rather than the typical radiotherapy outpatient presentation these are acutely ill patients who have exhausted all other treatment options and will require active monitoring throughout the whole process. As such they engender unfamiliar emotive issues around mortality which are not familiar in the radiotherapy setting At the inception of this technique we felt that as radiographers, our knowledge of cardiac anatomy and physiology was lacking. What was traditionally an avoidance structure is now the target and we needed to better understand cardiac structures to facilitate the IGRT image matching process and subsequent treatment delivery. A dedicated radiologist provided training to a core group of radiographers who could cascade this training as appropriate. Once we knew what we were looking at from an anatomical point of view, we decided to look at previous CBCT images for thorax patients with Implanted Cardiac Devices (ICD) to evaluate different matching strategies. We soon realised that image quality would be a major issue, mainly due to the artefacts from the pacing wires. Inspection of these thorax images identified further issues that we also needed to address in order for us to match safely and accurately. This led to us working closely with the imaging medical physics experts looking at how to optimise image quality whilst preserving a realistic treatment delivery timeframe. This included looking at motion management strategies, varying the gantry speed and the mAs and also looking at 4DCBCT all utilising an anatomical thorax phantom and a 4D Quasar phantom. The results of this development process led us to what we believed would be the optimal imaging parameters to enable us to treat our first patient successfully. Pre-treatment CT imaging protocols were also