Myocardial perfusion imaging with first-pass computed tomographic imaging: Measurement of coronary flow reserve in an animal model of regional hyperemia

The accurate assessment of myocardial blood flow (MBF) is a potential adjunct to the anatomy of CT coronary angiography.

To compare semi-quantitative parameters from first-pass CT (FP CT) imaging with absolute measures of MBF in an animal model of altered MBF.

A pig model of intracoronary adenosine (n = 8) was used during FP CT. This produces a zone with hyperemic MBF and a control zone within a slice. A subset of these animals also underwent LAD occlusion with imaging. Fluorescent microspheres (Mcsp) were injected into the left atrium to determine absolute MBF concurrent with CT imaging. Pigs were placed in a 64-slice (Philips) CT with acquisition performed during IC adenosine and occlusion. A 40% dilution of Iopamidol 370 (1 mL/kg) was injected IV at 5 mL/second. CT acquisition was ECG gated over 40 cardiac phases with the following parameters: 180° axial mode (pitch = 0), field of view = 250 mmsq, 512 × 512 matrix, slice thickness = 2.5 mm × 10 slices, temporal resolution = 330 ms, 120 kV, 495 ma. Mcsp were injected immediately following CT imaging. The heart was sectioned into 2.5 mm slices to match the CT images and segmented. Time attenuation curves (TAC) were generated from CT in intervention and control zones based on Mcsp values. Mcsp coronary flow reserve (CFR) = hyperemic/control MBF, and CT CFR was derived from intervention/control area under curve from baseline corrected TIC.

MBF control = .65 ± .28, MBF adenosine = 2.6 ± .7 mL/min/g (P < .0001). CFR = 4.1 ± 1.1, CT CFR = 4.3 ± 1.4 (P = NS). There was a significant (r = .94, P < .0001) correlation between CFR and CT CFR.

CT first-pass myocardial perfusion imaging is feasible using a simple semi-quantitative analysis which provides reasonable estimates of MBF.