Evaluation of effective dose for a patient under Ga-67 nuclear examination using TLD, water phantom and a simplified model.
This study evaluated the effective dose of Ga-67 for a patient undergoing Ga-67 citrate nuclear examination by applying thermoluminescent dosimeter (TLD) technique and an indigenous water phantom. The Ga-67 radionuclide remaining in the body inevitably generated a measurable internal dose even though gamma camera scanning took only minutes to complete the clinical examination. For effective simulation of the cumulated effective dose for a patient undergoing examination, 150 TLDs were placed inside the water phantom for 6 days to monitor the gamma ray dose from the distributed Ga-67 citrate solution. The inserted TLDs represented internal organs, and the effective dose was calculated according to data in the ICRP-60 report. The water phantom was designed to model the body of a healthy human weighing 70 kg, and the water that was mixed with Ga-67 citrate solution was slowly replaced with fresh feed water to yield the required biological half life of the phantom. After continuously feeding in fresh water throughout the 6 days of TLD exposure, the TLDs were analyzed to determine the effective doses from the various biological half lives of the phantom. The derived effective dose of 185 MBq Ga-67 citrate solution for male/female (M/F) was 10.7/12.2, 10.7/12.0, 8.7/9.9 and 6.0/6.8 mSv, of biological half lives of 6.0, 4.5, 3.0 and 1.5 days, respectively. Although these experimental results correlated well with earlier empirical studies, they were lower than most calculated values. The cumulated uncertainty in the effective dose was 12.5-19.4%, which was acceptable in terms of both TLD counting statistic and reproducibility.
Graduate Institute of Radiological Science, Central Taiwan University of Science and Technology, Takun, Taichung 40609, Taiwan.
Kuang Hua
KH
Chu
Yu Ting
YT
Lin
Chia Chun
CC
Hsu
Chien Yi
CY
Chen
Lung Kwang
LK
Pan
D001822:Body Burden; D002951:Citrates / Q000032:analysis* / Q000493:pharmacokinetics*; D003198:Computer Simulation; D005708:Gallium / Q000032:analysis* / Q000493:pharmacokinetics*; D006801:Humans; D008954:Models, Biological; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011877:Radionuclide Imaging / Q000295:instrumentation / Q000379:methods*; D019275:Radiopharmaceuticals / Q000032:analysis / Q000493:pharmacokinetics; D012062:Relative Biological Effectiveness; D013819:Thermoluminescent Dosimetry / Q000379:methods*; D014018:Tissue Distribution; D014867:Water; D014915:Whole-Body Counting / Q000379:methods*
D002951:Citrates; D019275:Radiopharmaceuticals; D014867:Water; D005708:Gallium; C103850:gallium citrate