Cardiac Ejection Fraction and Volume Measurements Using Dynamic Cardiac Phantoms and Radionuclide Imaging

Dynamic cardiac phantoms and radionuclide imaging were used to obtain ejection fraction (EF) and left ventricular (LV) volume measurements. Tc-99m pertechnetate and water solutions were used to fill the ventricles, and 10 to 51 ml were added to the ventricular chambers so that 5 ejection fractions of 15% to 55% were produced. For planar and SPECT imaging a triple camera system with three different collimators, low energy high resolution (LEHR), ultra-high resolution (LEUR), and super high resolution (LESR) parallel beam collimators, were used. Three different collimators were chosen to evaluate the effects of different collimator resolutions on EF and LV volume measurements. The EF measurements from the planar images by three different collimators agree well with the actual EF within 10%. The volume estimations by pixel summing method produced the best estimations with a threshold of about 50% of the peak value within the ROI. In general, the lower the resolution of the collimator, the greater the deviation in the measured LV volume as the threshold level was changed, Overall, the count based method yielded the most reliable estimations in EF and volume measurements. The dynamic cardiac phantom is useful for evaluating methods for gated cardiac function measurements and studying collimator characteristics in cardiac imaging.