ESTRO 36 Abstract Book

S109 ESTRO 36 _______________________________________________________________________________________________

medical physicists built a document management system that follows the patient process from university clinics to the Skandion Clinic. It contains all guiding and supporting documents, procedures and instructions. An essential experience acquired was that it is very important to write the required documents on so many procedures, guidelines and instructions as much as possible before the first patient treatment. Thus it was found that once the clinic was up and running with patient treatments, it was much easier to revise an existing procedure that to get time to write entirely new ones. Acceptance and measurement, education and training. It was decided early on that the RTT/nurses would work in team with the medical physicists on measurement and acceptance of IBA's equipment so there was at least one RTT/nurse during the daytime. Then we continued during the first half of the year with a medical physicist and a RTT/nurse to work together on the morning checks. The clinical training included the IBA Web training from UPenn in Philadelphia as well as study visits for two weeks in the proton clinic in Philadelphia. To this the IBA on site clinical training at the Skandion Clinic was added. We were given training on all new systems including trolley transport, CT scanning, journal system, fire and safety, CPR, etc. Another valuable experience was gathered from end-to- end testing, when a mock patient went through all phases of the process from each university clinic to the Skandion Clinic and back. An empty House to a functioning clinic. RTT/nurses had responsibility for equipping the premises with all that may be needed in order to start up a functioning clinic. This included practically everything from staff clothing to consumables and medicines, the toys for the children and even the special requirements of the anesthesia personnel. In summary, it has been hard work, frustrating at times, but extremely educational and stimulating most of the time, and above all a fun time to start up a clinic. SP-0217 Workflow in a proton therapy department – real difference from photon therapy? F. Fellin 1 1 Ospedale Santa Chiara di Trento, U.O. Protonterapia, Trento, Italy In Europe, there was a significantly increase in proton therapy (PT) facilities in the last few years. In PT, Radiation Therapy Technologists (RTTs) have a key role throughout the patient’s therapeutic course, such as in photon therapy. The physical characteristics of protons are an advantage for saving the organs at risk (OARs) and/or for increasing the dose to the target, but they imply some important criticalities during the patient workflow. Pencil Beam Scanning (PBS) is the most advanced technique for PT but this is the proton technique with more criticality. RTTs, should know these critical issues and be aware of the impact that they have in the patient workflow and in their working activities. RTTs are involved in several steps of the patient workflow in PT; in general, they are the same as in photon therapy: simulation CT, diagnostic imaging, treatment planning, delivery of therapy. However, in each single step, there are important differences compared to photon therapy. Starting from the simulation, the main differences relate to the choice of the immobilization devices, both for their purchase that for each specific patient, and the definition with tatoo of the treatment isocenter that, especially with PBS, it can be defined directly during the acquisition of simulation CT. In addition, since the dose delivery is very accurate, the definition of target volumes and OARs must be very strict. For this reason, the PT facilities are usually equipped with MR and PET-CT systems; RTTs must be able to use this equipment and to acquire the necessary images. In the treatment planning step, the Medical Dosimetrists

(MDs) work with the Medical Physicists in the plans optimization; they will use all the experience to get the best plan for each patient. In addition to all the attention that MDs must have during treatment planning, which are common in photon therapy, in PT there are other situations in which they must be careful. For example, it is very important to set the correct direction of the fields based on the tissues that the beams must pass through before reaching the target and it is recommended to avoid that all fields have the distal fall-off in the same area (in particular near OARs); it is important to limit the use of the range shifter and to select the most appropriate irradiation technique based on the specific case (SFO, MFO); MDs must know and evaluate all possible uncertainties (range, RBE, …); they must adopt robust optimization techniques and field specific PTV. Even for the delivery of therapy sessions, there are some important differences between photon and proton therapy. First, the equipment is quite different: RTTs must know in detail the PT equipment operation. Proton therapy equipment is much larger and more complex compared to photon therapy system. In PT, the patient setup is checked every day; generally, RTTs use flat panels with x-ray tubes system (for 2D images) or CBCT (for 3D images). In some facilities, a CT on-rails is installed in the treatment room and RTTs use this one for monitoring the patient position before the therapy. The advantage of CT on-rails is that, in principle, you can use the daily images for checking the dose distribution every day. In PT, tattoos performed during the simulation CT are important especially in the first treatment session. They are used to align the patient and move manually the treatment couch on the isocenter, for defined the setup position. Afterwards, RTTs capture the couch coordinate for setup position and, during subsequent sessions, the table will be aligned automatically. In all sessions except the first one, tattoos are important only in treatments with immobilization devices that are not perfectly indexed on the couch, e.g. in the case of treatments in pelvic area. RTTs must be very careful during the proton dose delivery with PBS. There isn’t a proper ratio between dose and monitor units delivered; the number of monitor units depend on the field size: the greater the size of the target, the greater the number of MU and the beam-on time. Given the precision of proton dose delivery, small anatomical changes can lead to important variations of dose distribution in the patient. For this reason, RTTs must observe and communicate any anatomical variations that they see during the patient setup. In this way, it is possible to perform any dosimetrical checks in the course of therapy. In these cases, it is very useful to have a CT on- rails. In PT, RTTs will have to acquire a weekly control CT for treatments of areas prone to anatomical changes. It will be used by Physicists or MDs to perform dose assessments during the treatment and, if necessary, they will organize a replanning. These are some of the most significant differences observed in proton therapy compared to photon therapy; they change the work of RTTs in patient workflow. PT is an advanced, complex and precise radiation therapy technique and it requires very high skills for RTTs.

Symposium with Proffered Papers: Combining tumour and normal tissue models

SP-0218 Novel approaches in the study of bladder cancer A. Kiltie 1 1 Oxford, United Kingdom, Patients with muscle-invasive bladder cancer can be treated by removal of their bladder (cystectomy) or by bladder preserving strategies, which include the use of