Attenuation-corrected 99mTc-MIBI SPECT in overweight patients with chronic ischaemic dysfunction:: a comparison to NH3PET and implications for the diagnosis of myocardial viability

Objective We determined the value of attenuation correction (AC) of myocardial perfusion estimation with Tc-99m-MIBI SPECT in overweight patients by comparison of uncorrected (filtered back-projection (FBP) and corrected (an iterative algorithm with a measured attenuation coefficients map (FL-AC)) Tc-99m-MIBI relative uptake to perfusion data obtained in the same patients with NH3 PET. In addition, the impact of attenuation correction for the assessment of myocardial viability with Tc-99m-MIBI SPECT was determined using FDG PET as the reference method. Methods Thirty consecutive overweight patients (BMI = 28 +/- 4) with left ventricular dysfunction underwent a resting Tc-99m-MIBI SPECT and a PET study (NH3 and FDG). Tc-99m-MIBI SPECT scans were reconstructed without attenuation correction (FBP) and with attenuation correction (FL-AC). The left ventricle was divided into 16 segments, in which the relative uptake was quantified using circumferential profiles. A relative uptake >= 60% was considered consistent with viable myocardium for FDG and MIBI. Results The absolute difference between Tc-99m-MIBI SPECT and NH3 PET uptakes was less pronounced in the inferior (12 +/- 10% vs. 17 +/- 12%, P < 0.001), anteroseptal (12 +/- 11% vs. 16 +/- 12%, P = 0.009) and septal (15 +/- 12% vs. 18 +/- 14%, P = 0.003) regions (FL-AC vs. FBP, respectively). The sensitivity of MIBI for diagnosing myocardial viability increased from 83 to 100% (P = 0.034), without loss in specificity. Conclusion Attenuation correction improves myocardial perfusion estimation by Tc-99m-MIBI SPECT in the inferior, anteroseptal and septal regions and increases its sensitivity for the diagnosis of myocardial viability.