Evaluation of the VeriDose in vivo dosimetry system

Recently, a new design of an in vivo diode dosimetry system, VeriDose diodes, has been introduced by Nuclear Associates to verify the radiation dose delivery to patients treated with either photon or electron beams. The goal of this study is to evaluate the linearity, accuracy, reproducibility, energy dependence, and orientation dependence of this system. These investigations were performed in Solid Water phantom material for both photon and electron beams. The results of the diode dosimetry were compared with the data measured simultaneously using a calibrated ion chamber. Also, for verification of the reproducibility of the results, the investigations were repeated on different days. The results indicated less than a 4% deviation between the diode and ion chamber measured dose for both photon and electron beams. Also, the responses of the photon and electron diodes were linear for doses greater than 2 cGy and 10 cGy, respectively. The response of the photon diode is insensitive (less than 5%) except when the beam is tangent to the skin or beam entering from the tail (wire) end of the diode. However, the electron diode is angular independent between 20° and 90° relative to the patient's skin.