The purpose of this study is to evaluate the quality and prognostic ability of low dose 99mTc-tetrofosmin Myocardial Perfusion SPECT Imaging.

The objective of this study is to determine if myocardial perfusion imaging (MPI) using a new SPECT reconstruction software and a low dose (LD) of 99mTC-tetrofosmin will provide equal quality and prognostic value as a full dose (FD) of 99mTc-tetrofosmin myocardial perfusion SPECT imaging methodology.

The images of clinical patients from the Diagnostic Imaging Department will be assessed and compared for image quality and myocardial perfusion. The outcomes of participants that have had FD studies will be compared to those who have had LD studies. Consented participants will be contacted and will be asked to provide information on their cardiovascular health since the date of their LD or FD scan, such as non fatal myocardial infarction, death, congestive heart failure, admission to hospital with chest pain, further cardiac diagnostic testing, including angiography and early and late revascularization. The event information will be tabulated at 6, 12, 18, and 24 months for the LD and FD studies.

The study hypothesizes that there will be no difference in the quality and prognostic value between the LD and FD 99mTc-tetrofosmin SPECT MPI imaging protocols. The study hypothesizes that there will be no increase in repeat diagnostic testing and angiography with using the LD imaging protocol.

Inclusion Criteria:

• Participants who have completed the FD and LD MPI studies on the GE Infinia Haweye or GE NM 530 (CZT crystal) cameras
• Retrospective participants must consent to the study interview(s) for data collection
• Prospective participants must consent to follow up for data collection

Exclusion Criteria:

• Unwilling to consent to data collection either retrospectively or in follow up prospectively

Clinical patients who have undergone myocardial perfusion imaging.