A microcomputerized system of nuclear probe for left ventricular function evaluation

In this work, it is presented the development of a system, consisting in a nuclear probe and a 16 bits microcomputer, for left ventricular function (LVF) monitoring and analysis. Previously used in renal and thyroid studies, the nuclear probe, 2''x2''NaI(Tl) crystal, was adapted for its new application. The alterations include the design and construction of appropriate colimators and unterfacing to a strip-chart register and a magnetic tape recorder. After a single injection of Tc-99m labelling red blood cells, the probe is placed over the patient's chest on a convenient left anterior oblique position and a left ventricle time activity curve is obtained. This curve and the patient's eletrocardiogram (ECG) are recorded for posterior processing. The software, in PASCAL language, transfers the data from the magnetic tape to the microcomputer and provides the LVF and ECG curves to be displayed on beat-to-beat mode or as mean curves. From these curves one can extract ventricular parameter such as: ejection fraction, ejection rate, systolic and diastolic intervals and heart rate, by manually positioning three cursors on the points of interest. A critical evaluation of this method is performed and its advantages as well as its limitations are discussed. This approach provides an easy to operate and a low cost device that can be useful in many clinical situations, for example, the continuous monitoring in ICUs, the screening in out-patient departments. The assessment of drugs effects on left ventricular function is also possible. (author)