SPECT myocardial blood flow quantitation toward clinical use: a comparative study with super(13)N-Ammonia PET myocardial blood flow quantitation

The aim of this study was to evaluate the accuracy of myocardial blood flow (MBF) quantitation of super(99m)Tc-Sestamibi (MIBI) single photon emission computed tomography (SPECT) compared with super(13)N-Ammonia (NH3) position emission tomography (PET) on the same cohorts. Recent advances of SPECT technologies have been applied to develop MBF quantitation as a promising tool to diagnose coronary artery disease (CAD) for areas where PET MBF quantitation is not available. However, whether the SPECT approach can achieve the same level of accuracy as the PET approach for clinical use still needs further investigations. Twelve healthy volunteers (HVT) and 16 clinical patients with CAD received both MIBI SPECT and NH3 PET flow scans. Dynamic SPECT images acquired with high temporary resolution were fully corrected for physical factors and processed to quantify K1 using the standard compartmental modeling. Human MIBI tracer extraction fraction (EF) was determined by comparing MIBI K1 and NH3 flow on the HVT group and then used to convert flow values from K1 for all subjects. MIBI and NH3 flow values were systematically compared to validate the SPECT approach. The human MIBI EF was determined as [1.0-0.816*exp(-0.267/MBF)]. Global and regional MBF and myocardial flow reserve (MFR) of MIBI SPECT and NH3 PET were highly correlated for all subjects (global R super(2): MBF=0.92, MFR=0.78; regional R super(2): MBF greater than or equal to 0.88, MFR greater than or equal to 0.71). No significant differences for rest flow, stress flow, and MFR between these two approaches were observed (All p greater than or equal to 0.088). Bland-Altman plots overall revealed small bias between MIBI SPECT and NH3 PET (global: Delta MBF=-0.03Lml/min/g, Delta MFR=0.07; regional: Delta MBF=-0.07-0.06 , Delta MFR= -0.02 -0.22). Quantitation with SPECT technologies can be accurate to measure myocardial blood flow as PET quantitation while comprehensive imaging factors of SPECT to derive the variability between these two approaches were fully addressed and corrected.