Research Questions:

1. Is there a significant difference between the causal repeat rate of myocardial perfusion studies for Tc99m tetrofosmin and Tc99m sestamibi?
2. Is there a significant difference in the causal repeat rate of myocardial perfusion studies for Tc99m tetrofosmin and Tc99m sestamibi if an independent technologist reviewer blinded to the radiopharmaceutical makes the decision to repeat the study?
3. Is there a significant difference in the quantitative diagnostic measures reported between the original and the acceptable repeated studies?

There are two commonly used Tc-99m based radiopharmaceuticals useful in the diagnosis and localization of regions of reversible myocardial ischemia in the presence or absence of infarction under exercise and rest conditions. One is Tc-99m tetrofosmin (Tc-99m-1,2-bis[bis(2-ethoxyethyl) phosphino] ethane), the other is Tc-99m sestamibi (Tc-99m- methoxyisobutylisonitrile). When performing a myocardial perfusion SPECT (MPS) study, extracardiac subdiaphragmatic activity adjacent to the myocardium can cause artifacts in the inferior wall and can be detrimental to the accuracy of the study1,2. Following acquisition, MPS studies are routinely checked for potential imaging artifacts. When a separation between the extracardiac activity cannot clearly be distinguished from the myocardium, the study should be repeated. Repeating the SPECT study can affect the efficiency of a lab as well as having a negative influence on patient comfort and overall satisfaction. The goal of this study is to determine if there is a significant difference in the number of studies that should be repeated between the two commonly used radiopharmaceuticals.

Inclusion Criteria:

• Patients receiving sestamibi MPI study or tetrofosmin MPI study

Exclusion Criteria:

• Thallium or dual isotope MPI study

Patients referred for MPI