Abstract:
The development of PET/CT scan has received great attention in the medical diagnostic study.However, whole-body PET/CT examinations increase patient exposure compared to an individual CT or PET examination. The purpose of this study is to investigate the patient doses and factors affecting from the administration of fluorine-18-fluorodeoxyglucose ([superscript 18]F-FDG) and the CT scan. Thirty-five patients with aged ranged from 28 years to 60 years (mean ± SD, 44±10), underwent whole-body PET/CT examinations at King Chulalongkorn Memorial Hospital, with suspected of cancer spreading to other organs. Internal dose at the target organs included liver, kidneys, stomach, urinary bladder, colon, thyroid gland, gonads, lungs, skin, bone marrow, bone surface, breast and spleen, were calculated using the MIRD (Medical Internal Radiation Dosimetry) method. The effective dose from CT scan was calculated using Monte Carlo simulation, WinDose program version 2.1a. The results show the organ receiving the highest absorbed doses was the urinary bladder of 63.72±9.41 muGy/MBq (95 % CI: 60.49-66.95). The critical organ such as gonads received average absorbed dose of 11.46±3.78 muGy/MBq. Average dose coefficient from administration of [superscript18]F-FDG of 15.56±1.52 muSv/MBq. Average [superscript18]F-FDG activities of 312 MBq was administered, resulted the average whole-body effective doses from PET scan of 4.82±0.5 mSv, ranged from 3.81 and 5.81 mSv. The average whole-body effective dose from the CT scan was 14.45±2.82 mSv, ranged from 10.04 and 21.98 mSv. The average effective dose for patients undergoing whole-body [superscript18]F-FDG PET/CT examinations was 19.27±2.92 mSv, ranged from 14.27 and 26.95 mSv. Factors influenced the patient dose in this study were the activity of [superscript18]F-FDG, the mass of organs, patient BMI, mAs and scan length. The patient dose is mostly dependent on the activity of [superscript18]F-FDG with the correlation, r = 0.720 (p-value < 0.01) from PET scan, and dependent on mAs and patient BMI with the correlation 0.980 and 0.866 (p-value < 0.01), respectively, for CT scan. The benefits of this study are the records of patient dose and related information for [superscript18]F-FDG PET/CT in Thai patient in the future.
