SU‐FF‐T‐362: Dosimetric Evaluation of the OneDose MOSFET for Measuring Kilovoltage Imaging Dose From Image‐Guided Radiotherapy

Abstract

Purpose: There is a growing interest to determine and to manage the additional image dose to radiotherapy patients. An easy‐to‐use in vivo dosimeter would be very useful for kilovoltage (kV) x‐rays used in IGRT. This study aims to provide the dosimetric characteristics of the commercially available OneDose™ for measuring dose from kV x‐rays with energy ranging from 60 to 125 kVp used in IGRT procedures with respect to reproducibility and energy correction factors. Method and Materials: The OneDoseTM system consists of a small MOSFET dosimeter with overall physical dimensions of 6 mm wide, 33 mm long, and < 1 mm thick and a portable handheld battery‐powered reader. The dosimeter is wireless with adhesive backing to stick to patient's skin. This single‐use dosimeter was pre‐calibrated by the manufacturer using Co‐60 beams. The energy response for kV x‐rays produced by a Varian OBI system was determined by using an ionization chamber in which the air‐kerma calibration factors were obtained from an Accredited Dosimetry Calibration Laboratory (ADCL). Results: The dosimeters have reproducible readings with a deviation of 1–4% for imaging dose of only a few cGy. The energy correction factors were found to be 0.27 – 0.32 for kV x‐rays from the OBI system ranging from 60 to 125 kVp including beams from cone‐beam CT. Conclusion: OneDose™ dosimeter has a similar reproducibility when used for measuring dose from kV photon beams as that when used for measuring dose from MV photon beams. A correction factor that is energy dependent must be applied because of the over‐responds to x‐rays in the diagnostic energy range. The ease‐to‐use allows the OneDose™ dosimeter to be suitable for in vivo dosimetry of measuring doses resulting from imaging guidance.Conflict of Interest: Research sponsored by Sicel Technologies, Inc. Morrisville NC.