Scintigraphic imaging procedures are now available that routinely permit visualization and quantitation of cardiac function. Image formation, while the most powerful form of data acquisition, carries with it a penalty of reduced detection sensitivity. As a consequence, there is a lower limit to the duration of physiologic phenomena that can be studied with present imaging methods. A number of medically interesting situations can be identified, however, in which the knowledge of regional function provided by imaging studies is not of primary importance. Instead, changes in global left ventricular function subsequent to various interventions might be of interest. In such cases, the temporal constraints of imaging procedures can, in large measure, be overcome by using non-imaging detectors or 'probes'. Probes can be constructed with detection efficiencies for left ventricular radioactivity that are at least in order of magnitude greater than for imaging devices. Such devices would be expected to yield measurements whose statistical precision was similar to that for imaging studies but requiring less than one-tenth the data acquisition time. To realize the advantages in practice requires the consideration of the entire acquisition-processing system as well as the detector design. The micro-processor based system described in this report was designed for maximum flexibility and utility. While the principle function of the system is to acquire, create, analyze and display (in real-time) left ventricular time activity (or volume) curves, provision is also made to acquire additional physiologic signals (e.g., ECG, flowmeter, etc.) and to calculate and display relationships between these various data. The system was designed for interactive use so that the system user can alter the course of a series of measurements based on previous results. These general capabilities are illustrated with several examples. In the first, LV function was measured continuously in a subject from (supine) rest through exercise and recovery. The second example illustrates the use of the system in acquiring (LV) pressure-volume loops. Several technical problems, such as correction for LV background radiation, appear at present to limit the probes applicability. Even now, however, probe systems are domonstrably useful in the study of global left ventricular function when this function is changing rapidly with time in response to various interventions.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging