Assessment of Left Ventricular Ejection Fraction with multifocal collimators: Comparison between IQ-SPECT, Planar Equilibrium Radionuclide Angiography, and Cardiac Magnetic Resonance

Background: IQ-SPECT has been shown to significantly reduce acquisition time and administered dose while preserving image quality in myocardial perfusion imaging. The accuracy of gated blood-pool SPECT (GBPS) with IQ-SPECT to assess left ventricular ejection fractions (LVEF) and left ventricular end diastolic volumes (LVEDV) remains unknown. The purpose of this study is to compare LVEF and LVEDV obtained with IQ-SPECT to planar ventriculography and cardiac magnetic resonance imaging (cMRI).

Methods: Sixty consecutive patients who underwent IQ-SPECT GBPS and planar imaging were included. Among those patients, 11 also underwent cMRI within 30 days of their GBPS. IQ-SPECT LVEF and LVEDV were calculated automatically using 2 validated software: QBS and MHI (Harel et al, 2007, 2010). IQ-SPECT LVEF measurements were compared to planar LVEF and cMRI LVEF. IQ-SPECT LVEDV measurements were compared to cMRI LVEDV.

Results: Average ± SD planar LVEF was 48 ± 11 % (range 23 to 70 %) and average GBPS LVEDV was 177 ± 59mL (range 63 to 342 mL). Average ± SD GBPS LVEF were 40 ± 12 % and 44 ± 12 % with QBS and MHI respectively. Correlation coefficients between IQ-SPECT and planar LVEF were r=0.70 and r=0.83 for QBS and MHI respectively. Correlation coefficient between cMRI and planar LVEF was 0.69. Correlation coefficients between cMRI and GBPS LVEF were 0.52 and 0.65 using QBS and MHI respectively. Correlation coefficient between cMRI and GBPS LVEDV was 0.80 with both QBS and MHI. There was no significant correlation between the planar and GBPS LVEF difference versus LVEDV with QBS (r=0.03, p=0.81) and MHI (r=0.14, p=0.29).

Conclusions: : LVEF calculated with GBPS using IQ-SPECT correlates well with planar measurements for a broad range of LVEF and LVEDV. Correlation is best using the MHI method and variation is independent of LVEDV. Furthermore, there is very good correlation between LVEDV measured with GBPS using IQ-SPECT and cMRI. These results suggest that IQ-SPECT can be used for the assessment of LVEF and LVEDV with GBPS.

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