Development of a Radiation Sensor System for Measuring Medical Radiation Exposure (e.g. CT scans on patients)

Abstract

By Matthew Oh, Neurobiology

Advisor: Matthew Mille

Abstract: This research revolves around dosimetry, the study of measuring radiation dosage using dosimeters (radiation sensors). An OSLD (optically stimulated luminescence dosimeter) system is used in clinical practice to measure the radiation dose delivered to CT subjects to identify potential associated health risks such as secondary cancers. An OSLD program requires a calibrated reader and dosimeter reusability. The objectives of this study were: (1) To calibrate OSLD reader (2) To use OSLDs inside a physical phantom to measure organ dose received in typical brain CT scans (3) To create a box to clear OSLDs for use in future experiments. (1) Background readings of 300+ dosimeters were recorded at NCI. Dosimeters were irradiated at NIST and calibration factors were calculated. (2) Dosimeters were inserted into a pediatric phantom to measure dose to organs. (3) A box was created for LED light dosimeter illumination (GE Indoor Floodlight, 75 W, 850 lumens) for signal clearance. Preliminary testing was performed using irradiated dosimeters (200 or 300 mGy) using NIST M100 X-ray Beam. Fraction of remaining signal recorded as function of illumination time (12s ~ 8 hrs). Through this research, (1) calibration of OSL reader established. (2) The radiation dose to brain for brain CT was 23.8 mGy. (3) box created for 99.8% of original signal clearance within 20 minutes. In future research, the NCI OSL dosimetry system will be utilized to measure radiation dose in epidemiological studies to investigate medical radiation exposure caused health risks (i.e. cancer).