Purpose: To prospectively determine whether the absolute tissue sodium concentration (TSC) increases in myocardial infarctions (MIs) in humans and whether TSC is related to infarct size, infarct age, ventricular dysfunction, and/or electrophysiologic inducibility of ventricular arrhythmias.Materials and Methods: Delayed contrast material-enhanced 1.5-T hydrogen 1 (H-1) magnetic resonance (MR) imaging was used to measure the size and location of nonacute MIs in 20 patients (18 men, two women; mean age, 63 years +/- 9 [standard deviation]; age range, 48-82 years) examined at least 90 days after MI. End-systolic and end-diastolic volumes, ejection fraction, and left ventricle (LV) mass were measured with cine MR imaging. The TSC in normal, infarcted, and adjacent myocardial tissue was measured on sodium 23 (Na-23) MR images coregistered with delayed contrast-enhanced 1H MR images. Programmed electric stimulation to induce monomorphic ventricular tachycardia (MVT) was used to assess arrhythmic potential, and myocardial TSC was compared between the inducible MVT and noninducible MVT patient groups.Results: The mean TSC for MIs (59 mu mol/g wet weight +/- 10) was 30% higher than that for noninfarcted ( remote) LV regions (45 mu mol/g wet weight +/- 5, P <.001) and that for healthy control subjects, and TSC did not correlate with infarct age or functional and morphologic indices. The mean TSC for tissue adjacent to the MI (50 mu mol/g wet weight +/- 6) was intermediate between that for the MI and that for remote regions. The elevated TSC measured in the MI at 23Na MR imaging lacked sufficient contrast and spatial resolution for routine visualization of MI. Cardiac TSC did not enable differentiation between patients in whom MVT was inducible and those in whom it was not.Conclusion: Absolute TSC is measurable with 23Na MR imaging and is significantly elevated in human MI; however, TSC increase is not related to infarct age, infarct size, or global ventricular function. In regions adjacent to the MI, TSC is slightly increased but not to levels in the MI. (c) RSNA, 2008.

Purpose: To objectively characterize different heart tissues from functional and viability images provided by composite-strain-encoding (C-SENC) MRI.Materials and Methods: C-SENC is a new MRI technique for simultaneously acquiring cardiac functional and viability images. In this work, an unsupervised multi-stage fuzzy clustering method is proposed to identify different heart tissues in the C-SENC images. The method is based on sequential application of the fuzzy c-means (FCM) and iterative self-organizing data (ISODATA) clustering algorithms. The proposed method is tested on simulated heart images and on images from nine patients with and without myocardial infarction (MI). The resulting clustered images are compared with MRI delayed-enhancement (DE) viability images for determining MI. Also, Bland-Altman analysis is conducted between the two methods.Results: Normal myocardium, infarcted myocardium, and blood are correctly identified using the proposed method. The clustered images correctly identified 90 +/- 4% of the pixels defined as infarct in the DE images. In addition, 89 5% of the pixels defined as infarct in the clustered images were also defined as infarct in DE images. The Bland-Altman results show no bias between the two methods in identifying MI.Conclusion: The proposed technique allows for objectively identifying divergent heart tissues, which would be potentially important for clinical decision-making in patients with MI.

Purpose: To develop a breathhold method for black-blood viability imaging of the heart that may facilitate identifying the endocardial border.Materials and Methods: Three stimulated-echo acquisition mode (STEAM) images were obtained almost simultaneously during the same acquisition using three different demodulation values. Two of the three images were used to construct a black-blood image of the heart The third image was a T-1-weighted viability image that enabled detection of hyperintense infarcted myocardium after contrast agent administration. The three STEAM images were combined into one composite black-blood viability image of the heart. The composite STEAM images were compared to conventional inversion-recovery (IR) delayed hyperenhanced (DHE) images in nine human subjects studied on a 3T MRI scanner.Results: STEAM images showed black-blood characteristics and a significant improvement in the blood-infarct signal-difference to noise ratio (SDNR) when compared to the IR-DHE images (34 +/- 4.1 vs. 10 +/- 2.9, mean +/- standard deviation (SD), P < 0.002). There was sufficient myocardiurn-infarct SDNR in the STEAM images to accurately delineate infarcted regions. The extracted infarcts demonstrated good agreement with the IR-DHE images.Conclusion: The STEAM black-blood property allows for better delineation of the blood-infarct border, which would enhance the fast and accurate measurement of infarct size.

Background: Large, buoyant high density lipoprotein, also known as HDL subclass 2 (HDL2),and small, dense HDL, also known as HDL subclass 3 (HDL3) are thought to exert variable protective effects a...

Assessment of myocardial viability in patients with Myocardial Infarction (MI) is important for therapeutic decision making. Magnetic resonance imaging (MRI) delayed-enhancement (DE) images provide accurate myocardial viability images. In addition, functional MRI provides important complementary information about the heart muscle status. From the combined viability and functional images, different tissue types of the heart could be identified using clustering techniques. However, seldom are these MRI images acquired at the same point in time to allow for automatic clustering. Composite Strain-Encoding (C-SENC) MRI is a modification of the standard SENC MRI, which enables acquiring both viability and functional images in the same cardiac phase. A multi-stage clustering technique was applied to the resulting C-SENC images of canine models with MI as well as to human volunteers and patients with MI. The results showed the applicability of the proposed technique for identifying different heart tissues: normal myocardium, infarction, and blood.