Stereotactic Radiosurgery (SRS) is a procedure that uses ionizing radiation in a single fraction or few fractions to treat intracranial lesions. Usually, for these treatments, small photon fields, formed by circular collimators or micro multileaf collimators are used. The objective of the present work is to compare the measurements of the dose in depth (PDD), the off-axis ratio (OAR), and the output factor (OF) using Edge diode and radiochromic films and analyzing the agreement between the two detectors during these measures. In the gamma index analysis of the profiles, the minimum percentage reached was 98.3% of the points in the criterion 1% and 0.5 mm. The maximum percentage difference in the output factor was 2.79% for a cone 4 mm and 10FFF. In the gamma index analysis of the PDDs, the minimum percentage reached was 97% of the points in the criterion 1% and 1mm. The results show a good agreement between the edge detector and the film in small field measurements for radiosurgery.

The stereotactic radiosurgery (SRS) is a technique that uses multiple beams extremely collimated of ionizingradiation to treat intracranial lesions and functional abnormalities, with high geometric precision and dosimetricaccuracy. The use of small fields is already a reality in modern radiotherapy techniques. However, the accuracyin small-field dosimetry is challenging because of several process physics and aspects related to the detector. Theaim of this paper is to evaluate the response of a dosimetric system developed by Nuclear Energy Department ofFederal University of Pernambuco (DEN/UFPE) for small field dosimetry. Measurements of, output factor (OF),off-axis ratio (OAR) and percentage depth dose (PDP) were performed with this dosimetric system andcompared with the results obtained with a commercial diode and treatment planning system data. The resultsshowed that the Diode-DEN presents a reliable and economical alternative for small fields dosimetry used intreatments of SRS. This detector can be used for validation of dates obtained in commissioning of linearaccelerator and inserted in Treatment Planning Systems (TPS).