Are you J Stacy Allen?

Claim your profile

Publications (3)11.71 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: While the current gold standard for coronary imaging is X-ray angiography, evidence is accumulating that it may not be the most sensitive technique for detecting unstable plaque. Other imaging modalities, such as cardiovascular magnetic resonance (CMR), can be used for plaque characterization, but suffer from long scan and reconstruction times for determining regions of stenosis. We have developed an intravascular fluorinated contrast agent that can be used for angiography with cardiovascular magnetic resosnace at clinical field strengths (1.5 T). This liquid perfluorocarbon nanoparticle contains a high concentration of fluorine atoms that can be used to generate contrast on 19F MR images without any competing background signal from surrounding tissues. By using a perfluorocarbon with 20 equivalent fluorine molecules, custom-built RF coils, a modified clinical scanner, and an efficient steady-state free procession sequence, we demonstrate the use of this agent for angiography of small vessels in vitro, ex vivo, and in vivo. The surprisingly high signal generated with very short scan times and low doses of perfluorocarbon indicates that this technique may be useful in clinical settings when coupled with advanced imaging strategies.
    Journal of Cardiovascular Magnetic Resonance 02/2007; 9(3):565-73. · 4.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The utility of harmonic phase (HARP) analysis was recently demonstrated in humans and large animals as a technique for rapid and automatic analysis of tagged magnetic resonance images. In the current study, the applicability and accuracy of HARP analysis for automatic strain quantification in small animals were investigated. A validation study was performed on seven postinfarct rats and seven age-matched controls. A method for direct computation of 2D Lagrangian strain fields from spatial derivatives of HARP images was also developed in this paper. The results of HARP analysis were evaluated by comparison with those of homogeneous strain analysis employing finite element method and manual tag tracking. Both methods were validated with simulated digital images. Compared to conventional homogeneous strain analysis, HARP analysis yielded similar results in the assessment of regional strain patterns in both control and infarct rats. Both methods detected a reduction in maximal stretch and shortening in infarct rats. Our results suggest that HARP analysis can also be applied to quantify alterations in regional myocardial wall motion in small animals.
    Magnetic Resonance in Medicine 01/2005; 52(6):1282-90. · 3.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Structural remodeling of myocardium after infarction plays a critical role in functional adaptation. Diffusion tensor magnetic resonance imaging (DTMRI) provides a means for rapid and nondestructive characterization of the three-dimensional fiber architecture of cardiac tissues. In this study, microscopic structural changes caused by MI were evaluated in Fischer 344 rats 4 wk after infarct surgery. DTMRI studies were performed on 15 excised, formalin-fixed rat hearts of both infarct (left anterior descending coronary artery occlusion, n = 8) and control (sham, n = 7) rats. Infarct myocardium exhibited increased water diffusivity (41% increase in trace values) and decreased diffusion anisotropy (37% decrease in relative anisotropy index). The reduced diffusion anisotropy correlated negatively with microscopic fiber disarray determined by histological analysis (R = 0.81). Transmural courses of fiber orientation angles in infarct zones were similar to those of normal myocardium. However, regional angular deviation of the diffusion tensor increased significantly in the infarct myocardium and correlated strongly with microscopic fiber disarray (R = 0.86). These results suggest that DTMRI may provide a valuable tool for defining structural remodeling in diseased myocardium at the cellular and tissue level.
    AJP Heart and Circulatory Physiology 10/2003; 285(3):H946-54. · 4.01 Impact Factor