Romanian Reports in Physics, Vol. 64, No. 3, P. 728–736, 2012 MEDICAL PHYSICS IN VIVO DOSIMETRY MEASUREMENTS FOR BREAST RADIATION TREATMENTS G. VASILE 1,3 , MADALINA VASILE 2,3 , O.G. DULIU 3 1 Center of Radiotherapy, 1 st rue de l’Octroi, Blois, 41000, France, E-mail: gmvasile@yahoo.com 2 Hospital Center of Niort, 40 th avenue Charles de Gaulle, Niort, 79021, France, E-mail: madapop@yahoo.com 3 University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125 Magurele (Ilfov), Romania, E-mail: duliu@b.astral.ro Received September 12, 2011 Abstract. In vivo dosimetry is a vital tool in quality assurance program. It is very important to check the dose delivered for each patient undergoing radiation treatment in order to avoid over or under dosing. The aim of this paper is to present a study for quality control protocol using in vivo dosimetry for breast cancer radiation treatment. We report one year estimation of the radiation treatments accuracy, expressed as a comparison between delivered and prescribed doses. Dose delivered were measured by in vivo dosimetry in order to detect any systematic errors that may have escaped the different check performed in treatment plan preparation, data transfer or patient set-up. The diodes detectors used in this study were tested, calibrated and corrected in order to be accepted for treatment measurements. For each radiation field used in treatment a comparative study between calculated and expected dose on the patient’ skin were performed. Depending of the observed discrepancies, the corrective actions and the decision levels were set up. During this study we investigated 634 radiation photon fields, in 1968 measurements, 66 potential errors being detected. Dosimetry checks show that only 3 of them could have induced a variation, over 5% in the dose delivered. Key words: radiotherapy, quality control, in vivo dosimetry, diodes. 1. INTRODUCTION In vivo dosimetry (IVD) represents a direct measurement of the dose delivered to the target volume in the radiotherapy. In order to limit the errors during the radiation treatment, some international and national organizations such as European Society for Therapeutic Radiology and Oncology (ESTRO) [1], American Association of Physicists in Medicine (AAPM) [2], French National Institute of Cancer (INCA) [3] and Romanian National Commission for Nuclear Activity Control (CNCAN) [4] have recommended the implementation of quality control (QC) program to achieve the accuracy and precision of treatments in radiotherapy.