Nuclear stress tests are similar to the treadmill test but also provide images of the heart taken under a special camera. This test uses an IV injection of a radioactive isotope, using a similar amount of radiation as an x-ray. This allows images to be taken of the heart both before and after exercise. If the patient is unable to walk on the treadmill to stress the heart, there are alternative medications that can be given to the patient to stress the heart in place of the treadmill.