Functional segmentation of the hippocampus in the healthy human brain and in Alzheimer's disease (vol 66, pg 28, 2013)

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Comparison of estimated human dose of 68Ga-MAA with 99mTc-MAA based on rat data

Objective: 99m Tc macroaggregated albumin (99m Tc- MAA) that had been used as a perfusion agent has been evaluated. In this study, we tried to estimate human absorbed dose of 68 Ga-MAA via commercially available kit from Pars-Isotopes, based on biodistribution data in wild-type rats, and compare our estimation with the available absorbed dose data from 99m Tc-MAA. Methods: For biodistribution of 68 Ga-MAA, three rats were sacrificed at each selected times after injection (15, 30, 45, 60, and 120 min) and the percentage of injected dose per gram of each organ was measured by direct counting from rats data from 11 harvested organs. The medical internal radiation dose formulation was applied to extrapolate from rats to human and to project the absorbed radiation dose for various organs in humans. Results: The biodistribution data for 68 Ga-MAA showed that the most of the activity was taken up by the lung (more than 97 %) in no time. Our dose prediction shows that a 185-MBq injection of 68 Ga-MAA into humans might result in an estimated absorbed dose of 4.31 mGy in the whole body. The highest absorbed doses are observed in the adrenals, spleen, pancreas, and red marrow with 0.36, 0.34, 0.26, and 0.19 mGy, respectively. Conclusion: Since the 99m Tc-MAA remains longer than 68 Ga-MAA in the lung and 68 Ga-MAA has good image qualities and results in lower amounts of dose delivery to the critical organs such as gonads, red marrow, and adrenals, the use of 68 Ga-MAA is recommended