First-pass (FP) MR myocardial perfusion (perf) imaging can quantify absolute myocardial blood flow (MBF) but images are of low signal at conventional field strength. Purpose: To determine the accuracy of absolute FP MBF measures at 3 Tesla and compare these measures with FP 1.5T using MBF by microspheres (mcsp) as the gold-standard.
Methods: A pig model was used to alter MBF in a coronary artery during FP MRI (intracoronary adenosine followed by ischemia). This produces an active zone with a range of MBF and a control zone. Mcsp were injected into the left atrium with concurrent reference sampling. FP MR perf imaging was performed at 1.5T (n=8) or 3.0T (n=7) using a saturation-recovery gradient echo sequence in short-axis slices (SAX) during a bolus injection of 0.025mmol/kg gadolinium-DTPA. Fermi function deconvolution was performed on active and control ROI from SAX slices with an arterial input function from the LV cavity. These MR values of MBF were matched to mcsp values obtained from SAX slices at pathology.
Results: Occlusion MBF was 0.22±.26 ml/min/g, adenosine MBF was 2.11±1.13 ml/min/g and control zone MBF was 0.70±0.22ml/min/g. The correlation of MR FP MRI with mcsp is shown in Figure 1
: 3T) r=0.95, p<0.0001, 1.5T, r=0.94, P<0.0001. The 95% confidence limits were slightly narrower at 3T (3T=0.41ml/min/g, 1.5T=0.55ml/min/g, p=NS. FP MRI characteristics were better at 3T (noise, SNR, contrast enhancement all superior at 3T). In zones where MBF<0.50ml/min/g, the correlation with mcsp was closer at 3T (r=0.55 at 1.5T, r=0.85 at 3T).
Conclusion: Absolute MBF by FP perfusion imaging is accurate at both 1.5 and 3T. Signal quality is better at 3T which may confer a benefit in low MBF zones.
Dipyridamole infusion protocols for absolute myocardial blood flow quantitation by PET
