Quantitative analysis of transmural gradients in myocardial perfusion magnetic resonance images

Abstract

Conventional quantitative assessments of myocardial perfusion analyze the temporal relation between the arterial input function and the myocardial signal intensity curves, thereby neglecting the important spatial relation between the myocardial signal intensity curves. The new method presented in this article enables characterization of sub-endocardial to sub-epicardial gradients in myocardial perfusion based on a two dimensional, "gradientogram" representation, which displays the evolution of the transmural gradient in myocardial contrast uptake over time in all circumferential positions of the acquired images. Moreover, based on segmentation in these gradientograms, several new measurements that characterize transmural myocardial perfusion distribution over time are defined. In application to clinical image data, the new two-dimensional representations, as well as the newly defined measurements revealed a clear distinction between normal perfusion and inducible ischaemia. Thus, the new measurements may serve as diagnostic markers for the detection and characterization of epicardial coronary and microvascular disease.

Fig. 1. Examples of the sampling grid used to extract SI curves from apical (a), mid (b), and basal (c) slice of a SA perfusion CMR series.

Fig. 2. Examples of perfusograms for an endocardial layer (a), mid-myocardial layer (b), and an epicardial layer (c). Note the endocardial perfusion defect indicated by the arrow.

Fig. 3. A chart representing an endocardial SI curve, an epicardial SI curve, a gradient curve, and an arterial input curve.

Fig. 4. The newly defined quantitative measures for assessing the severity of perfusion deficits based on the segmented gradientogram and gradient curves.

Fig. 5. Examples of sub-epicardial perfusograms before registration and filtering (a), after registration but before filtering (b), and after registration and filtering (c).

Fig. 6

Results for a patient with normal perfusion, including the original high resolution CMR perfusion images at apical (a), mid (b), and basal (c) position; the red arrow indicates the start and direction of the gradientogram (top-bottom), gradientograms for the apical (d), mid (e), and basal (f) position, and bull’s eye plots displaying for all slices the mean gradient (g), peak gradient (h), and cumulative gradient (i); bright (yellow) is worse.

Fig. 7

Results for a patient with abnormal perfusion, including the original high resolution CMR perfusion images at apical (a), mid (b), and basal (c) position; the red arrow indicates the start and direction of the gradientogram (top-bottom), gradientograms for the apical (d), mid (e), and basal (f) position, and bull’s eye plots displaying for all slices the mean gradient (g), peak gradient (h), and cumulative gradient (i); bright (yellow) is worse.

Fig. 8. Segmented perfusion deficit in the gradientograms of the apical (a), mid (b), and basal (c) slices of the positive case.