ESTRO 36 _______________________________________________________________________________________________ female.Twenty-six patients (57.7%) underwent to SRT, nineteen (42.3%) to WBRT-SIB.The median number of brain metastases was 1 (range, 1-3).Acute toxicity (headache, hearing problems, nausea and vomiting), did not occur in treated patients.With a median follow-up of 20 months (range, 1.7 -56 months), the median LC was not reached.The 1 year LC was 77% in all patients.The median and 1 year OS was 16 months 71%, respectively.No significant impact of treatment option on clinical outcomes was observed.Local control and OS data for each group are reported in table 1. ConclusionOur study shows that SRT and WBRT-SIB offer a good LC and OS, without significant differences.Probably these data maybe due to the baseline patients selection and size simple therefore we are analyzing QoL and neurocognitive function of survivor patients to understand the global impact of these two modalities of treatments.

_____________________________________________________________________________________________________linked to a virtual RA plan into the Eclipse TPS.Two full arcs with photon beam energies of 6MV and 30°/330° complementary collimator angle were set.. Two evaluation groups, consisting of 5 new knowledge based plans (KBP) each, were used to validate LR and IR models.KBP were compared with clinical plans (CP) in term of PTVs homogeneity, using HI = 100X (D2% -D98%)/D50%, and DVH endpoints, as shown in table 1.

Background: The problems associated with the dosimetry of small fields used in stereotactic radiation therapy can be overcome using a careful choice of dosimeter in which the active dimensions of the detector are small compared to the size of the fields used. However, for routine verification of individual patient treatments it is often difficult to find sufficient machine time to obtain an adequate amount of data. Even where this is possible it can be problematic to perform measurements in places of high calculation uncertainty. This applies near heterogeneities within the patient and for extremely small fields, where the positional uncertainty is significant compared to the size of field measured or the detector construction makes a significant perturbation to the field. Methods: A method is described providing a computational system for the routine verification of stereotactic treatments using Monte Carlo techniques, simulating the transport of particles through the accelerator and patient geometry. Our stereotactic treatments are delivered using a BrainLAB M3 mu MLC for which an accurate model is required in order to simulate delivered doses to an acceptable uncertainty. A BEAMnrc Monte Carlo code module has been written which exactly models the M3 mu MLC, removing uncertainties associated with the approximation of the leaf geometry which may be particularly important for very small fields. This has been incorporated into a MATLAB-based tool box for dosimetric verification of stereotactic radiotherapy which is used to generate patient phantoms and input files for use within a distributed computing environment to improve calculation time. Results: Uncertainties of less than 3% can be achieved in typically 5 h of simulation time using approximately 30 PCs enabling the system to be used for routine verification of fractionated treatments. Investigations into the effects of increasing the calculation pool have shown that it may be possible to use this system for the pre-treatment verification of single fraction techniques. Conclusions: The investigation has shown that it is possible to implement a distributed computing-based solution to provide accurate verification of stereotactic radiotherapy and radiosurgery plans, using existing computing resources within a busy cancer centre. Copyright (C) 2010 S. Karger AG, Basel

This work investigated the accuracy of Monte Carlo (MC) simulations of amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) for the dosimetric verification of intensity-modulated radiotherapy (IMRT). In particular, the suitability of the method for verification of head and neck IMRT with extended field segments (≈20 cm superior–inferior), covering almost the entire detector area, was studied. A solution involving schematic modelling of backscatter materials has been established to account for non-uniform backscatter to the imager from supporting structures. 96% of points within the IMRT fields evaluated passed a 'gamma' evaluation criterion of 2%, 2 mm at isocentre at a dose rate of 100 MU min−1 with this solution included. Only 79% of points passed this gamma criterion without the correction for backscatter included. This work has also demonstrated the ability of the technique to detect systematic delivery errors in step and shoot IMRT. The technique identified a systematic overshoot on the first segment and an undershoot on the final segment. Results were verified by ion chamber measurements and agreed well with those reported in the literature, averaging approximately 0.1 and 0.3 MU for 100 and 300 MU min−1 deliveries, respectively. MC portal verification has the potential to become a key tool in the verification of IMRT and can also facilitate selection of optimal delivery parameters, thus improving treatment accuracy. This approach can be applied to the verification of other new treatment techniques and should also enable development of methodologies to detect and correct for delivery errors, both before and during treatment.

SHaRP - Simultaneous boosted, Hypofractionated pelvic Radiotherapy for Prostate cancer.

A method is presented to predict beam profiles and outputs for wedged asymmetric fields defined by independent collimator jaws allowing fast generation of beam profiles whilst requiring very little additional data to that already used by most treatment planning systems in generating symmetric field isodoses. Symmetric field data are modified by the use of wedged primary off-centre ratios (POCRs) which are obtained from in air measurements of the largest possible wedged field. Beam hardening occurring within the flattening filter and wedge is taken into account by the use of attenuation coefficients measured under each wedge and used to generate the wedged POCR at depth. A full investigation into the comparison between measured and calculated profiles was performed which demonstrates favourable agreement across the whole of the asymmetric field including the penumbra.