⁹⁹Tc^m-SESTAMIBI for planar myocardial perfusion imaging; not as ideal as the physical properties

⁹⁹Tc^m-methoxyisobutyl isonitrile (Tc-SESTAMIBI) has recently been introduced as a new myocardial perfusion agent which exhibits ideal physical properties for imaging with the gamma camera. To assess the diagnostic accuracy of planar Tc-SESTAMIBI, myocardial perfusion imaging was performed in 60 consecutive patients at rest and during exercise. The results were compared with coronary angiographic findings, obtained within 3 months of the exercise test. Planar²⁰¹T1 images were also performed on the same day and to the same level of stress as the Tc-SESTAMIBI exercise. Exact segmental agreement between Tc-SESTAMIBI and²⁰¹T1 was 77%. Nineteen per cent of all 900 segments demonstrated ischaemia with Tc- SESTAMIBI and 20% with²⁰¹T1. The overall sensitivity for detecting haemodynamically significant coronary artery disease with Tc-SESTAMIBI was 86% and specificity was 78%; with²⁰¹T1 the values were 89 and 78%, respectively (differences not significant). Vessel-specific comparative detection rates revealed no statistical significant differences between both radiopharmaceuticals. Intra-observer variability for Tc-SESTAMIBI images was 12% and for²⁰¹T1 it was 14%. Inter-observer variability for Tc-SESTAMIBI was 14% and for²⁰¹T117%. Although the physical characteristics of Tc-SESTAMIBI allow crisp and clear high-count density imaging, no significant differences are found when planar images are compared with²⁰¹T1 and are well within observer variabilities.