Count-based left ventricular volume determination utilizing a left posterior oblique view for attenuation correction.

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Abstract
The inherent error of the left ventricular volume measurement from the gated equilibrium blood pool scintigram utilizing the count-based technique was determined. The study population consisted of 26 patients who had undergone biplane contrast ventriculography [for the study of various heart diseases]. The patients were imaged with a parallel-hole collimator in the left anterior oblique position showing the septum to best advantage. A reference blood sample was counted and radionuclide volumes calculated without correction for attenuation. Attenuation corrected volumes were derived with the factor 1/e-.mu.d, where d = distance from skin marker to center of the left ventricle in the orthogonal left posterior oblique view and .mu. = linear attenuation coefficient. A series of .mu. values from 0.08-0.15 cm-1 was evaluated. There was a trend toward improvement in the r value and lowering of the SEE [standard error of the estimate] with attenuation correction. The tightest 95% confidence limits achieved for an end-diastolic 150-ml ventricle were .+-. 44 ml and for an end-systolic 75-ml ventricle .+-. 32 ml. In view of the magnitude of inherent error, the count-based volume measurement may be more suitable for group analyses and in cases in which in individual patient serves as his own control.