Right anterior oblique first-pass radionuclide ejection fractions: effects of temporal smoothing and various...

Thirty-seven patients undergoing contrast left ventriculography were studied by first-pass radionuclide angiography (FPRA) in the right anterior oblique view. Ejection fraction (LVEF) was calculated from FPRA using (a) a spatially and temporally varying background correction (BGC) based on a matrix of activity in lung and left atrium and (b) BGC with temporal fluctuation but with no allowance for spatial variations. The two methods were performed on both raw and temporally smoothed data. All four LVEFs correlated well with contrast LVEF (r = 0.90 - 0.94). Absolute values differed significantly from contrast values except for the method using the spatially and temporally varying BGC on smoothed data, which provided the closest overall agreement at all levels of LVEFs, despite occasional large individual variations. The same method on raw data overestimated low LVEFs and the method applying only temporal fluctuation in background underestimated high LVWFs. Allowance for spatial and temporal variations in background is therefore important when first-pass radionuclide angiography is performed in the RAO view.