Abstract Book

S12

ESTRO 37

acquired in-room at the treatment position. While some proton therapy centres have opted for in-room CT-on- rails imaging, which provide dose-calculation-quality images without correction, several have preferred to employ at-isocenter gantry-, nozzle-, C-arm- or couch- mounted cone beam CT (CBCT) imaging solutions (see Figure 1).

The natural extension of CBCT intensity correction is to enable dose calculation on 4DCBCT images for monitoring of the treatment of moving tumours. However in such applications the lower amount of projections per reconstructed phase entails that iterative reconstruction techniques may be necessary to obtain an image capable of accurately driving deformable image registration.

CBCT images suffer from severe artefacts, partly caused by a high scatter-to-primary ratio due to the flat panel imaging geometry which captures a significant proportion of scattered photons. It is generally acknowledged that the image quality of CBCT is not sufficient to allow the conversion to stopping power required for performing accurate proton therapy dose calculations, and that correction techniques must be employed to achieve this objective. Correction strategies are generally based on deformable image registration (DIR) of the planning CT data (Figure 2A) to the anatomy observed in the CBCT images (Figure 2B), essentially combining the image quality of conventional CT scanning with the ability of CBCT to image the anatomy in the treatment position to create a virtual CT image (Figure 2C). The technique has been shown to work well for head and neck cases where 3D images are considered when compared to a control or re- planning CT (Figure 2E). A variant of such correction methods employs the virtual CT to generate an estimate of the scatter distribution reaching the flat panel imager and correct the CBCT projections before image reconstruction (Figure 2D), which has been shown to perform well for sites such as the pelvis where less predictable motion than for head and neck cases can be expected. The latter approach has been compared to Monte Carlo simulations of scatter and found equivalent.

Symposium: Patient centered care and monitoring side effects: Review clinics and follow up

SP-0033 The role of a specialised nurse in cancer care during radiotherapy L. Van den Berghe 1 1 University Hospital Ghent, Radiotherapie, Gent, Belgium Abstract text Every training for radiotherapy nurse, radiographer or radiation therapist has the common goal of treating, counseling and caring for the patient during his or her treatment. The job is overshadowed by the mainly technical fact. Similarly, care for the patient and his environment is equally important and continuously present. Various curricula worldwide describe in specific details the content of the job. Nevertheless, researchers have, since the 40s of the previous age, been thinking about the specific role of the radiation oncology nurse. They described the importance of preparing patients before treatment, reassuring them regarding safety and their progress during treatment, comforting patients and addressing their symptoms. In America they described from 1980 on specific roles: patient care, education of patients and families, administrative responsibilities, research, consultation. During the 90s they described four levels of nursing care. Clinic care, patient teaching, counseling and the advanced practice role. The last role is evenso a role that the ESTRO RTT Committee introduced in the RTT Education Qualification Framework for level 7 and 8. So we become a "specialist" in radiation oncology. A possible strategy to work out this specialistic view is to