Thanks for writing your query to healthcaremagic. A myocardial perfusion SPECT (Single Photon Emission Computed Tomography) study, also called a cardiac stress-rest test, is used to evaluate the heart s blood supply. Two sets of images showing blood flow are obtained: the first following a period of rest, and the second following a period of stress, which involves exercise on a treadmill. If you are unable to do walk than medicines can be injected to induce the same effect as done by exercise.Myocardial perfusion SPECT is used to evaluate damage that might have been caused by a myocardial infarction (heart attack) and to assess the presence and extent of myocardial ischemia (reduced blood flow due to obstruction in the vessels). Since you are already have risk factor for having heart problem like diabetes, unstable angina 15 years back,so it is preferable that you get this test done. It will help to find out what is the status of the blood supply to your heart. There are no major risk involved in doing this test as the test is done under supervision of experienced cardiologists & medical staff who will be constantly monitoring your heart response to the test. During the test you may feel tired, have shortness of breath or have sweating. You can always inform your doctor any time during the test & the test can be stopped any time in between. Make sure you get the test done in good clinical stepup. I hope i have answered your query. In case of any further doubts, I will be happy to help you.