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A. S. Davis, D. Holck, K. Brown, D. Duffy, J. De la Torre; Uptake of Radioactive Iodine Into Orbital Tissue of Patients at 4 and 24 Hours After Undergoing Radioactive Iodine Uptake and Scan for Thyroid Abnormalities. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5251.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the uptake of radioactive iodine into orbital tissues utilizing single photon emission tomography (SPECT) scanning at 4 hours versus 24 hours of patients undergoing radioactive iodine uptake and scan for thyroid abnormalities.
5 patients being imaged for radioiodine (123-Iodine) uptake of the thyroid also underwent imaging of their orbital tissues utilizing single photon emission tomography (SPECT) scanning at 4 hours and 24 hours after the intake of radioiodine. The SPECT images taken at 4 hours were compared to the images taken at 24 hours using standard region of interest (ROI) analysis in the area of orbital tissue. Patients were also assessed for age, thyroid stimulating hormone blood levels, and presence or absence of thyroid related orbitopathy.
Of the 5 patients, 4 were female (80%) and 1 was male (20%). Ages ranged from 25-37 (mean 31.4). 1/5 patients (20%) had TSH levels significantly above the normal range (0.3-4.5 uIU/mL). 3/5 (60%) had TSH levels below the normal range, and 1/5 (20%) had TSH levels within the normal range. 1/5 patients (20%) had clinically diagnosed thyroid related orbitopathy and 4/5 (80%) had no signs of clinical eye disease. All 5 patients received a maximum dose of 300 micro curies of the 123-Iodine. 5/5 patients (100%) completed SPECT imaging of orbital tissues at 4 hours and 3/5 (60%) completed successful imaging of orbital tissues at 24 hours. Emitted gamma pulse counts in the area of orbital tissue at 4 hours ranged from 318-2469 (mean 1202.2). At 24 hours, emitted gamma pulse counts in the same area ranged from 87-229 (mean 137). The percent of detectable emitted gamma pulse counts between the 4 and 24 hour images ranged from 8.45-30.2 (mean 17.9%).
Single photon emission tomography scanning of orbital tissues in patients undergoing radioactive iodine uptake analysis for thyroid abnormalities appears to provide a greater emitted gamma count from orbital tissues at 4 hours compared to 24 hours after radioiodine intake.
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