A Dual Collimator Design for Beat-to-Beat Measurement of Cardiac Performance with an Anger Camera

A dual collimator was designed for an Anger camera to permit measurement of cardiac performance on a beat-to-beat basis. Special all-purpose (SAP) and special high-sensitivity (SHS) collimator sections can be interchanged without movement of the patient. Thus, left-ventricular regions of interest delineated on SAP multigated images can be transferred to SHS dynamic images to generate beat-to-beat volume curves. Preliminary balloon studies demonstrated an excellent correlation between ejection fractions calculated with the two collimators: r greater than 0.99, n = 17, p less than 0.001. Varying the volume of an adjacent "right ventricle" balloon failed to alter significantly the count rate from the "left ventricle" balloon's region of interest. Preliminary results on 12 patients, comparing standard-camera ejection fractions with average beat-to-beat ejection fractions, showed that is is possible to measure cardiac function on a beat-to-beat basis with a single-crystal gamma camera. There was minimal difference between the ejection fractions calculated by the dual-collimator method and a standard gated technique (r = 0.98, n = 12, p less than 0.001).