How Do Videodensitometric Ejection Fractions From Intravenous Digital Subtraction Ventriculograms Compare With First Pass Radionuclide Ejection Fractions? (Technical Aspects)

Three major errors implicit in the determination of ejection fractions from videodensi-tometric analysis of intravenous digital subtraction ventriculograms are errors due to: (1) nonlinear transfer of densitometric information about relative volumes, (2) inadequate background subtraction and (3) overlapping atrial contrast. Nonlinear errors associated with our imaging system were estimated using balloon phantoms in a water bath. These were small for a tube voltage of 90 kV and an iodine concentration of approximately 37 mg/cc commonly used in clinical studies. Background subtraction errors are approached by using phase matched second order mask images temporally close to the contrast images. Atrial overlap errors remain a significant problem. However, videodensitometric ejection frac-tions from intravenous digital studies correlated well with first pass right ventriculo-grams (r = 0.84) and left ventriculograms (r = 0.85).