NONINVASIVE MEASUREMENT OF LEFT-VENTRICULAR VOLUMES AND FUNCTION BY GATED POSITRON EMISSION TOMOGRAPHY

To date cardiac positron emission tomography (PET) studies have focuss ed on the measurement of myocardial blood flow, metabolism and recepto rs while left ventricular (LV) function and dimensions have been deriv ed from other modalities. The main drawback of this approach is the di fficulty of data co-registration, which limits clinical interpretation . The aim of this study was to evaluate whether it is possible to meas ure absolute cardiac volumes, and consequently LV function parameters such as ejection fraction, and wall motion with gated PET. Nineteen pa tients underwent a PET scan and planar radionuclide ventriculography ( MUGA) within 9+/-9 days. A 9-min scan (16 gates/cardiac cycle) was acq uired after inhalation of 3 MBq/ml of oxygen-15 labelled carbon monoxi de at the rate of 500 ml/min over 4 min using a multislice PET camera. Noise reduction was performed on the gated image to enhance the defin ition of the ventricles before reslicing to the short-axis view. A thr eshold value was used to detect the edge of the LV at each gate. LV vo lumes at each gate were estimated by summing the volume of voxels with in the LV boundary. PET measurements of LV volumes were as follows: LV end-diastolic volume ranged from 72 to 233 ml and LV end-systolic vol ume ranged from 24 to 203 ml. Phantom experiments supported the validi ty of this approach for estimating volumes, LV ejection fraction measu red with MUGA was 38.4%+/-16.3% (range 15%-71%) and that measured with PET was 39.6%+/-17.7% (range 9%-72%) (P=NS), The LV ejection fraction measurements were highly correlated (r(2)=0.824). These results indic ate that: (1) absolute end-diastolic and end-systolic volumes can be q uantified using gated PET and (2) LV ejection fraction can be accurate ly measured by gated PET simultaneously with the other physiological P ET parameters.