Consecutive short-axis slices of myocardial perfusion SPECT. With low (25 MBq) and high (200 MBq) injection doses in the rats with myocardial infarction. Each rat was imaged twice; one with the standard (STD) pinhole collimator (upper two panels) and the other with the high-sensitivity (HS) pinhole collimator (lower panels) with or without post-reconstruction filtering. The number in parentheses is the defect sizes, expressed as percentage of the left ventricular myocardium (%LV), measured on polar maps. G1.5 mm indicates Gaussian filter of 1.5-mm kernel size; G2.5 mm, Gaussian filter of 2.5-mm kernel size.