As an aid in differentiating pericardial effusion L from cardiac dilatation or hypertrophy, or both, mapping the distribution of radioactive tracers in the cardiovascular blood pool by scanning has been used increasingly since the method was introduced by Rejali, MacIntyre, and Friedell.1 One way of improving the resolution of the cardiac scan is to use radiopharmaceuticals that provide greater numbers of photons available to the scanning detector. A variety of agents have been used in the past. Wagner, McAfee, and Mozley2 used sodium iodide I 131 bound to human albumin; MacIntyre et al3 and others4 introduced the use of sodium iodipamide I 131 (Radio-Cholografin).
Technetium 99m, obtainable as a radioactive decay product of molybdenum 99 offers many advantages as a nuclide for scanning.5 The absence of beta radiation with99mTc and its six-hour physical half-life, make it suitable for use in millicurie dosage. When