Critical Organ Dose Estimation from Tc-99m-MIBI in Nuclear Medicine Cardiology Based on Distribution Data in Rats

Gholamreza  Fallah Mohammadi; Alireza  Khorrami Moghadam; Fariba  Abaszadeh; Mohammad  Mahdavi

doi:10.18502/fbt.v10i1.11518

Gholamreza Fallah Mohammadi Department of Radiology, Faculty of Allied Medicine, Mazandaran University of Medical Sciences, Sari, Iran
Alireza Khorrami Moghadam Department of Radiology, Faculty of Allied Medicine, Mazandaran University of Medical Sciences, Sari, Iran
Fariba Abaszadeh Department of Physics, University of Mazandaran, Babolsar, Iran
Mohammad Mahdavi Department of Radiology, Faculty of Allied Medicine, Mazandaran University of Medical Sciences, Sari, Iran

DOI: https://doi.org/10.18502/fbt.v10i1.11518

Keywords: Absorption Dose; Biodistribution; Internal Dosimetry; Nuclear Medicine; 99Tc-Methoxyisobutylisonitrile.

Abstract

Purpose: Calculating the organs' radiation dosage in cardiac nuclear medicine procedures is essential in order to identify critical organs, radiation risk assessment and optimization dose value in the injection of radiopharmaceutical drugs. In this study, the biological distribution of 99mTc-2-Methoxyisobutylisonitrile) 99mTc-MIBI as the most common radiopharmaceutical in a cardiac study in human organs based on animal samples was investigated.

Materials and Methods: After ^99mTc-MIBI preparation, radiopharmaceutical was injected into 15 rats. After sacrificing rats, the uptake of radiopharmaceuticals in critical organs at 15, 30, and 45 minutes was measured using an High Purity Germanium (HPGE) detector and the percentage of injected dose per gram of organs was calculated. The cumulative activity was calculated from the radiopharmaceutical transformation diagram with time. The absorption of a radioactive complex in human organs based on animal data was calculated by applying a correction factor. The organs dose was calculated using S factor and the effective dose was calculated using tissue weighting factors.

Results: The mean effective dose per unit of activity was 0.0062 mSv/MBq. The mean effective dose of 27.5 mCi radiopharmaceutical injection was 6.3 mSv. In this study, the absorbed dose in blood, heart, lung, thyroid, liver, spleen, stomach wall, muscle, and bone was calculated as 0.28, 2.92, 1.85, 24.82, 11.13, 7.03, 20.95, 1.11, 4.97, and 22.22 mGy, respectively.

Conclusion: The effective dose of human organs based on the animal model in the study of cardiac nuclear medicine was evaluated by injection of ^99mTc-MIBI radiopharmaceutical. The kidneys, salivary glands, thyroid, and spleen were the most critical organs that should be considered in dose optimization studies. The effective dose limit was 28% lower than the values reported in international references.