Radiation Dose Assessment In Torso Phantom From Spect-CT Imaging
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Date
2016-01
Authors
Abdul Rahman, Siti Fairus
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Single Photon Emission Computed Tomography-Computed Tomography (SPECT-CT) systems are one of the latest technologies that have been used regularly in nuclear medicine imaging because of their ability to provide precise localisation of the anatomical images and physiological data from nuclear medicine studies. However, the exposure to radiation especially x-rays pose risk of inducing cancer in patients. Therefore, quantifying the radiation dose from SPECT-CT imaging was the main aim of this study in order to ensure that patients are exposed to minimal amount radiation. Torso phantom was used as a model to measure the radiation dose. 99mTechnetium was used as the tracer for SPECT where 2 mCi of 99mTechnetium was injected into the liver region of the torso phantom and low dose CT protocol was used for CT imaging. The measurement of radiation dose was repeated for three times using Thermoluminescence Dosimeters (TLDs) as the detector. The TLD readings were measured and converted to dose value. Prior to the usage, the TLDs were subjected to annealing, calibration and also sensitivity testing in order to select the most suitable TLDs for radiation measurement. The results showed that the sensitivity factors of all the chosen TLDs were from 0.800 to 1.250 which falls within the standard acceptable limit. Furthermore, the temperature, relative humidity and also background radiation that were monitored pre and post imaging falls within the acceptable range specified by International Atomic Energy Agency (IAEA). The mean effective dose obtained for CT imaging was 0.025 mSv, the dose from SPECT was 3.6×10-4 mSv and dose from the hybrid system SPECT/CT was 0.028 mSv. Thus, the radiation dose for SPECT-CT imaging was higher compared to the doses measured from individual SPECT and CT imaging. This because the dose from SPECT-CT imaging is the summation doses from gamma rays emitted by 99mTechnetium injected into the phantom and also x-ray from CT machine.
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Keywords
Radiation dose assessment in torso phantom , from spect-CT imaging