Instrumentation for Radionuclide Cardiology

Radioactive tracers have been employed for the evaluation of cardiac structure and function for over 50 years. The discipline had its genesis in 1927 with the innovative experiments of Blumgart and Weiss [1]. These investigators, utilizing the principles of the radioactive tracer method devised by Hevesy [2], measured circulation in man by injecting a dose of radium C-salt (radon) into an antecubital vein detecting its arrival in the contralateral brachial artery with a Wilson cloud chamber. This technique was revived by Prinzmetal and associates [3] in 1948 with the advent of atomic age technology. Using a Geiger-Muller counter and the artifical radionuclide 24Na, these investigators repeated the Blumgart and Weiss determination of circulation time also recording temporal changes in the radioactivity over the heart and lungs. The radionuclide angiocardiogram was thus discovered. Many improvements in instrumentation and radiopharmaceuticals have since been introduced to facilitate evaluation of the central circulation. Cardiovascular nuclear medicine procedures today encompass a myriad of qualitative and quantitative techniques including: (1) detection and quantitation of intracardiac shunts, (2) measurements of regional myocardial blood flow, (3) visualization of anatomic relationships of major cardiovascular structures — such as chamber dilatation, ventricular or septal hypertrophy, pericardial effusion, or ventricular aneu-rysm, (4) identification of intracardiac clot or mass, (5) evaluation of heart mechanical function, (6) identification, anatomic localization, and sizing of acute myocardial infarcts, (7) noninvasive assessment of myocardial perfusion at rest and during exercise or pharmacologic stress, (8) assessment of severity of valvular regurgitation, and (9) evaluation of regional myocardial metabolism.