Quantitative assessment of Cerenkov luminescence imaging for in vivo measuring radioiodide uptake of thyroid gland in mouse

Objectives Cenenkov radiation can be observed from a range of positron-, β- and α-emitting radionuclides using optical imaging devices, and was found to correlate linearly with the measured radiation signal. This study aims to measure the radioiodide uptake of normal thyroid gland of mouse by Cerenkov luminescence imaging (CLI) and compared with gamma imaging method.

Methods To correlate the radioactivity with the photon flux measured from the thyroid gland, a serial doses of I-131 from 0.5 mCi to 2.0 mCi were intraperitoneally (i.p.) injected into BALB/c mice. The measurement was carried out at 24 hr later. To correlate the 24-hr thyroid uptake measured by gamma imaging with the uptake measured by CLI, 0.5 mCi of I-131 was i.p. administered into 12 mice. The % uptake was calculated as: (Thyroid CNT - Background CNT)/CNT of injected dose; CNT = counts/sec for gamma imaging or photons/sec for CLI.

Results The thyroid counts are well correlated with the thyroid photon flux by linear regression analysis. (y=6535+2x+23342, R²=0.9927) The % I-131 uptake of thyroid is 1.21±0.45 (mean±SD) (range: 0.5-2.2) measured by CLI and 29.78±7.78 (range:16.0-43.1) by gamma imaging. The linear regression of uptake measured by both methods is y=15.053x+11.608, R²=0.7723.

Conclusions CLI and gamma imaging exhibit correlations in measurement of I-131 uptake of thyroid gland of mouse. The findings warrant further exploration and optimization of CLI as an alternative to gamma imaging in measuring the thyroid uptake function in small animals.