A comparison of the clinical relevance of thallium-201 and technetium-99m-methoxyisobutyl-isonitrile for the evaluation of myocardial blood flow.

Thallium-201 is at present the radiotracer of choice for the clinical evaluation of myocardial blood flow. Although different technetium-99m-isonitrile agents have been synthesised recently, only 99m Tc-melhoxyisobutyl-isonitrile ( 99m Tc_MIBI) has proved to hold promise for clinical implementation. The myocardial distribution of 201 TI and 99m Tc_MIBI was compared in a group of 20 patients, who underwent both 201 TI single photon emission computed tomography and 99m Tc_MIBI study as well as coronary angiography. The sensitivity for predicting a lesion ranged from 25% to 88% in different areas of the heart and was comparable for the two radiophannaceuticals. The specificity was > 80% tor all regions except the inferior region where a specificily ot 58% obtained by 99m Tc-MIBI was better than the low specificity of 17% obtained with 201 TI (P< 0,008).