MDCT of the myocardium: a new contribution to ischemic heart disease

Myocardial delayed-enhancement CT: initial experience in children and young adults

BACKGROUND

Clinical utility of myocardial delayed enhancement CT has not been reported in children and young adults.

OBJECTIVE

To describe initial experience of myocardial delayed enhancement CT regarding image quality, radiation dose and identification of myocardial lesions in children and young adults.

MATERIALS AND METHODS

Between August 2013 and November 2016, 29 consecutive children and young adults (median age 16 months) with suspected coronary artery or myocardial abnormality underwent arterial- and delayed-phase cardiac CT at our institution. We measured CT densities in normal myocardium, left ventricular cavity, and arterial and delayed hypo-enhancing and delayed hyperenhancing myocardial lesions. We then compared the extent of delayed hyperenhancing lesions with delayed-enhancement MRI or thallium single-photon emission CT.

RESULTS

Normal myocardium and left ventricular cavity showed significantly higher CT numbers on arterial-phase CT than on delayed-phase CT (t-test, P<0.0001). Contrast-to-noise ratios of the arterial and delayed hypo-enhancing and delayed hyperenhancing lesions on CT were 26.7, 17.6 and 18.7, respectively. Delayed-phase CT findings were equivalent to those of delayed-enhancement MRI in all cases (7/7) and to those of thallium single-photon emission CT in 70% (7/10).

CONCLUSION

Myocardial delayed-enhancement CT can be added to evaluate myocardial lesions in select children and young adults with suspected coronary artery or myocardial abnormality.

Left ventricular myocardium segmentation on delayed phase of multi-detector row computed tomography

RATIONALE AND OBJECTIVES

Advanced ischemic heart disease is usually accompanied by left ventricular (LV) myocardial volume loss and an abnormal enhancing pattern on delayed phase of multi-detector row computed tomography (MDCT). To assist radiologists and physicians in estimating the LV myocardial volume on delayed phase, this paper proposes an adaptive segmentation method for contouring the myocardial region in the delayed-phase MDCT and for computing the volume.

MATERIALS AND METHODS

The proposed method uses an anisotropic diffusion filter as a preprocessing procedure to enhance contrast and reduce specks in MDCT imaging. This work picks the middle of mid-ventricular level image slices as the lead slice. The proposed method develops two contouring modes to sketch the myocardium contour on the lead slice. By establishing the obtained contours as the initial contours, the region-growing method is employed to identify the contour of the myocardial region for each slice. The convex-hull finding algorithm is then used to refine the extracted contour. Finally, the width properties of the myocardial region and the morphological operators are used to obtain the entire LV myocardial volume.

RESULTS

Twenty-seven healthy patients who had no symptoms of ischemic heart disease are examined to evaluate the performance of the proposed method. Compared with manual contours delineated by two experienced experts, the contouring results using computer simulation reveal that the proposed method reliably identifies contours similar to those obtained using manual sketching.

CONCLUSION

The proposed method provides robust contouring for the LV myocardium on delayed-phase MDCT. The potential role of this technique may substantially reduce the time required to sketch manually a precise contour with high stability.

Quantitative and qualitative characterization of the acute changes in myocardial structure and function after distal coronary microembolization using MDCT

RATIONALE AND OBJECTIVES

To determine the potential of multidetector computed tomography (MDCT) in assessing, at 72 hours, the effects of distal coronary microembolization on myocardial structure and function.

MATERIALS AND METHODS

Microembolic material (total volume=16 mm(3) of 40-120 μm diameter) was selectively delivered in the left anterior descending coronary artery under x-ray fluoroscopy (n = 6 pigs). After 72 hours, 64-slice MDCT was used to assess LV function, perfusion, and viability. For comparison between the measurements at 80 kV, 120 kV, and postmortem we used Bland-Altman and Pearson correlation. Histochemical and histopathological staining was used for quantitative and qualitative characterization of microinfarct.

RESULTS

Cine MDCT showed the deleterious effects of microembolization on systolic wall thickening, LV volumes, and ejection fraction. Perfusion parameters, such as max upslope, peak attenuation, and time to peak, differed between microinfarct territory and remote myocardium. Inconsistency in visualizing microinfarct was observed using tube voltages of 80 kV and 120 kV. The extent of heterogeneous microinfarct was 4.5 ± 1.0 % of LV mass at 80 kV, 6.1 ± 0.9% LV at 120 kV, and 5.9 ± 1.1% LV on postmortem. There was significant difference in the extent of microinfarct measured on 80 kV MDCT compared with 120 kV and postmortem. Microscopic examination revealed the random distribution of obstructed microvessels surrounded by myocardial necrosis and inflammatory cells in all animals.

CONCLUSION

Both visible and nonvisible microinfarct cause perfusion deficit and LV dysfunction. MDCT is sensitive for quantifying early functional changes in LV caused by microembolization. Further improvement in spatial resolution of this technology is needed to improve visualization of microinfarct.

Reperfusion injury components and manifestations determined by cardiovascular MR and MDCT imaging

Advances in magnetic resonance (MR) and computed tomography (CT) imaging have improved visualization of acute and scar infarct. Over the past decade, there have been and continues to be many significant technical advancements in cardiac MR and multi-detector computed tomography (MDCT) technologies. The strength of MR imaging relies on a variety of pulse sequences and the ability to noninvasively provide information on myocardial structure, function and perfusion in a single imaging session. The recent technical developments may also allow CT technologies to rise to the forefront for evaluating clinical ischemic heart disease. Components of reperfusion injury including myocardial edema, hemorrhage, calcium deposition and microvascular obstruction (MO) have been demonstrated using MR and CT technologies. MR imaging can be used serially and noninvasively in assessing acute and chronic consequences of reperfusion injury because there is no radiation exposure or administration of radioactive materials. MDCT is better suited for assessing coronary artery stenosis and as an alternative technique for assessing viability in patients where MR imaging is contraindicated. Changes in left ventricular (LV) volumes and function measured on cine MR are directly related to infarct size measured on delayed contrast enhanced images. Recent MR studies found that transmural infarct, MO and peri-infarct zone are excellent predictors of poor post-infarct recovery and mortality. Recent MR studies provided ample evidence that growth factor genes and stem cells delivered locally have beneficial effects on myocardial viability, perfusion and function. The significance of deposited calcium in acute infarct detected on MDCT requires further studies. Cardiac MR and MDCT imaging have the potential for assessing reperfusion injury components and manifestations.

Multidetector computed tomography in reperfused acute myocardial infarction. Assessment of infarct size and no-reflow in comparison with cardiac magnetic resonance imaging

OBJECTIVES

(1) To determine the accuracy of delayed enhancement multidetector computed tomography (MDCT) in measuring the extent of acute myocardial infarct and no-reflow areas using cardiac magnetic resonance imaging (MRI) as standard of reference and (2) to define the optimum timing between injection and MDCT image acquisition to characterize infarcted myocardium and no-reflow areas after reperfusion therapy.

MATERIALS AND METHODS

Nineteen patients were prospectively included after acute myocardial infarction and revascularization. Each patient had an MDCT acquisition before and 5 and 10 minutes after injection of 1.5 mL/kg iodinated contrast medium, and a contrast-enhanced MRI at 5 and 10 minutes after injection of 0.2 mmol/kg gadolinium chelate. We assessed image quality and infarct extent using MDCT and MRI, and we measured parameters related to iodinated contrast media kinetics (DeltaHU and DeltaHU ratio).

RESULTS

The areas of hyperenhanced myocardium located on the MDCT corresponded to the occluded vessel located on the coronary angiogram (kappa = 0.9). There were strong correlations between the extent of hyperenhanced infarcted myocardium on MDCT and MRI at 5 minutes (20.4% +/- 2.7% of left ventricle (LV) and 20.9% +/- 2.4%, respectively, R = 0.85; P < 0.0001) and 10 minutes after injection (21.0% +/- 2.9% of LV and 19.4% +/- 2.5%, respectively, R = 0.80; P < 0.0001). However, the correlation between the area of hypoenhanced myocardium measured using MDCT and CMR 5 minutes after injection (R = 0.86; P < 0.0001) was better than the measurement obtained 10 minutes after injection (R = 0.64; P = 0.002). On contrast-enhanced MDCT, 5 minutes after injection, the signal-to-noise ratio was significantly higher than at 10 minutes after injection in LV blood (28 +/- 1 to 21 +/- 1, respectively; P = 0.0007), normal myocardium (18 +/- 1 to 15 +/- 1; P = 0.0009), and hyperenhanced infarcted myocardium (24 +/- 1 to 20 +/- 1; P = 0.004). MDCT image quality was significantly better at 5 minutes (3.2 +/- 0.1) than at 10 minutes (2.8 +/- 0.2, P = 0.01, kappa = 0.4). The DeltaHU ratio increased slightly but significantly between 5 minutes (0.83 +/- 0.01) and 10 minutes (0.93 +/- 0.01; P = 0.01), suggesting a slow wash-in and wash-out of contrast medium in infarcted myocardium.

CONCLUSION

In ST segment elevation myocardial infarction patients contrast-enhanced MDCT is an accurate method for characterizing and sizing myocardial infarct and no-reflow. Contrast-enhanced MDCT performed 5 minutes after injection yields a higher signal-to-noise ratio and image quality than the 10 minutes time point with no difference in the extent of infarct measurement.