E. Nasr

Rôle de la radiothérapie dans l’ossification hétérotopique

PURPOSE To evaluate the use of radiation therapy for the prevention of heterotopic ossification. PATIENTS AND METHODS Twenty-two patients, 20 to 76 years old were irradiated for the prevention of heterotopic ossification. All patients received a postoperative irradiation consisting of 700 cGy delivered by 18 MV photons using a linear accelerator. The delay between surgery and irradiation was 24 hours for 20 patients, 48 hours for three patients, 72 hours for two patients and 96 hours for one patient. The follow-up of all patients was based on radiologic findings (Brooker score) as well as the clinical status of the articulation before and after surgery. Of the 14 cases for which follow-up data was available, seven received primary prophylaxis and seven received secondary prophylaxis. RESULTS Heterotopic ossification prophylaxis using radiation therapy was radiologically successful in 71.5% of patients: 85.7% success for patients receiving primary prophylaxis and 57.1% success for patients receiving secondary prophylaxis. No functional failure was reported. No patient developed radiation related side effects. CONCLUSION Radiation therapy is proven to be effective in preventing heterotopic ossification. A larger study group is needed in order to compare our results with those seen in the literature.

EP-1663: A tool for collision prediction in linac-based intracranial radiosurgery planning

Purpose or Objective: The use of volumetric modulated arc (VMAT) is well established for many clinical sites. However, brain tumours are often treated using a 3D cranial radiotherapy (3DCRT) technique with one or two phases. The use of VMAT for cranial radiotherapy is a positive alternative that has been explored by many centres, particularly for brain metastases. Although VMAT provides a more conformal dose across the target volume than conventional planning techniques the main disadvantage is the low dose bath to normal tissue. The potential for additional neurotoxicity must be considered when deciding the best method of treatment. A planning study was conducted to investigate the difference between 3DCRT, co-planar partial arc VMAT and co-planar full arc VMAT.

EP-1629: A novel method for electron beam geometry optimisation

Purpose or Objective: Labour-intensive procedures, such as adaptive radiotherapy and the upcoming new modalities protons and MR linac, result in an increased workload in the treatment planning department. We therefore started the FAST-planning project, a Framework for Automatic Segmentation and Treatment planning. The purpose of this project is to produce single-click automated treatment planning for the majority of tumour sites.

PO-0820: Volumetric quality assurance of RapidArc plans for multiple intracranial targets using gel dosimetry

Purpose or Objective: Brain Arteriovenous mal-formation (AVM), in some cases, is treated with Onyx34 liquid embolic system (LES) containing tantalum. Moreover, stereotactic radiosurgery (SRS) may be required when total obliteration is not achieved after embolization. Presence of tantalum in radiation field not only generates artefacts in computed tomography (CT) images but also it could arise dose distribution perturbations. Goal in this study was to analyze the perturbation effect of Onyx34 in flattening filter free (FFF) photon beams using GAMOS Monte Carlo (MC). Artefact cause analysis was also included in the study.