Determination of right ventricular ejection fraction from reprojected gated blood pool SPET: comparison with first-pass ventriculography

Gated blood pool (GBP) studies are widely available and relatively inexpens ive. We have previously published a simple and convenient method for measur ing left ventricle ejection fraction (EF) with increased accuracy from sing le-photon emission tomography (SPET) GBP scans. This paper describes an ext ension of this method by which right ventricular EF may also be measured. G ated SPET images of the blood pool are acquired and re-oriented in short-ax is slices. Counts from the left ventricle are excluded from the short-axis slices, which are then reprojected to give horizontal long-axis images. Tim e-activity curves are generated from each pixel around the right ventricle, and an image is created with non-ventricular pixels "greyed out". This ima ge is used as a guide in drawing regions of interest around the right ventr icle on the end-diastolic and end-systolic long-axis images. In 28 patients , first-pass ventriculography studies were acquired followed by SPET GBP sc ans. The first-pass images were analysed a total of four times by two obser vers and the SPET images were analysed three times each by two observers. T he agreement between the two techniques was good, with a correlation coeffi cient of 0.72 and a mean absolute difference between first-pass and reproje cted SPET EFs of 4.8 EF units. Only four of the 28 patients had a differenc e of greater than 8 EF units. Variability was also excellent for SPET right ventricular EF values. Intra-observer variability was significantly lower for SPET than for first-pass EFs: standard error of the estimate (SEE)=5.1 and 7.3 EF units, respectively (P<0.05). Inter-observer variability was com parable in the two techniques (SEE=5.2 and 6.9 EF units for SPET and first- pass ventriculography, respectively).