ECG GATED RADIONUCLIDE PLETHYSMOGRAPHY - A METHOD FOR THE ASSESSMENT OF PULMONARY SYSTOLIC BLOOD-VOLUME INCREASE

During cardiac systole the stroke volume of blood which is ejected fro m the right ventricle increases the pulmonary blood volume. This systo lic pulmonary blood volume increase is measured by using ECG gated che st scintigrams obtained with Tc-99(m)-labelled red blood cells. The to tal radiation counts in a region of interest that includes either the right or the left lung increases during systole. On the average, the i ncrease of the total pulmonary systolic radiation was found to be 62% of the systolic radiation decrease in the left ventricle region of int erest. The discrepancy between the value of the systolic pulmonary blo od volume increase and that of stroke volume is attributed to blood fl ow from the lungs into the left atrium during the cardiac systole peri od.