Person: Reese, Timothy
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Reese
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Timothy
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Reese, Timothy
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Publication In vivo fiber tractography of the right and left ventricles using diffusion tensor MRI of the entire human heart(BioMed Central, 2014) Mekkaoui, Choukri; Reese, Timothy; Jackowski, Marcel P; Bhat, Himanshu; Kostis, William J; Sosnovik, DavidPublication Correlation of DTI tractography with electroanatomic mapping in normal and infarcted myocardium(BioMed Central, 2014) Mekkaoui, Choukri; Jackowski, Marcel P; Thiagalingam, Aravinda; Kostis, William J; Nielles-Vallespin, Sonia; Firmin, David; Bhat, Himanshu; Ruskin, Jeremy; Reese, Timothy; Sosnovik, DavidPublication Diffusion Tensor Imaging in Patients with Glioblastoma Multiforme Using the Supertoroidal Model(Public Library of Science, 2016) Mekkaoui, Choukri; Metellus, Philippe; Kostis, William J.; Martuzzi, Roberto; Pereira, Fabricio R.; Beregi, Jean-Paul; Reese, Timothy; Constable, Todd R.; Jackowski, Marcel P.Purpose Diffusion Tensor Imaging (DTI) is a powerful imaging technique that has led to improvements in the diagnosis and prognosis of cerebral lesions and neurosurgical guidance for tumor resection. Traditional tensor modeling, however, has difficulties in differentiating tumor-infiltrated regions and peritumoral edema. Here, we describe the supertoroidal model, which incorporates an increase in surface genus and a continuum of toroidal shapes to improve upon the characterization of Glioblastoma multiforme (GBM). Materials and Methods DTI brain datasets of 18 individuals with GBM and 18 normal subjects were acquired using a 3T scanner. A supertoroidal model of the diffusion tensor and two new diffusion tensor invariants, one to evaluate diffusivity, the toroidal volume (TV), and one to evaluate anisotropy, the toroidal curvature (TC), were applied and evaluated in the characterization of GBM brain tumors. TV and TC were compared with the mean diffusivity (MD) and fractional anisotropy (FA) indices inside the tumor, surrounding edema, as well as contralateral to the lesions, in the white matter (WM) and gray matter (GM). Results: The supertoroidal model enhanced the borders between tumors and surrounding structures, refined the boundaries between WM and GM, and revealed the heterogeneity inherent to tumor-infiltrated tissue. Both MD and TV demonstrated high intensities in the tumor, with lower values in the surrounding edema, which in turn were higher than those of unaffected brain parenchyma. Both TC and FA were effective in revealing the structural degradation of WM tracts. Conclusions: Our findings indicate that the supertoroidal model enables effective tensor visualization as well as quantitative scalar maps that improve the understanding of the underlying tissue structure properties. Hence, this approach has the potential to enhance diagnosis, preoperative planning, and intraoperative image guidance during surgical management of brain lesions.Publication Diffusion MRI in the heart(John Wiley and Sons Inc., 2015) Mekkaoui, Choukri; Reese, Timothy; Jackowski, Marcel P.; Bhat, Himanshu; Sosnovik, DavidDiffusion MRI provides unique information on the structure, organization, and integrity of the myocardium without the need for exogenous contrast agents. Diffusion MRI in the heart, however, has proven technically challenging because of the intrinsic non‐rigid deformation during the cardiac cycle, displacement of the myocardium due to respiratory motion, signal inhomogeneity within the thorax, and short transverse relaxation times. Recently developed accelerated diffusion‐weighted MR acquisition sequences combined with advanced post‐processing techniques have improved the accuracy and efficiency of diffusion MRI in the myocardium. In this review, we describe the solutions and approaches that have been developed to enable diffusion MRI of the heart in vivo, including a dual‐gated stimulated echo approach, a velocity‐ (M 1) or an acceleration‐ (M 2) compensated pulsed gradient spin echo approach, and the use of principal component analysis filtering. The structure of the myocardium and the application of these techniques in ischemic heart disease are also briefly reviewed. The advent of clinical MR systems with stronger gradients will likely facilitate the translation of cardiac diffusion MRI into clinical use. The addition of diffusion MRI to the well‐established set of cardiovascular imaging techniques should lead to new and complementary approaches for the diagnosis and evaluation of patients with heart disease. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.Publication Accelerated free-breathing diffusion tensor MRI of the entire human heart using spatiotemporal registration and retrospective image selection(BioMed Central, 2016) Mekkaoui, Choukri; Reese, Timothy; Jackowski, Marcel P; Bhat, Himanshu; Sosnovik, DavidPublication Characterization of the myocardium in the 4-chamber view using accelerated free-breathing diffusion tensor MRI(BioMed Central, 2016) Mekkaoui, Choukri; Reese, Timothy; Bhat, Himanshu; Jackowski, Marcel P; Sosnovik, DavidPublication Fiber Architecture in Remodeled Myocardium Revealed with a Quantitative Diffusion CMR Tractography Framework and Histological Validation(BioMed Central, 2012) Huang, Shuning; Thiagalingam, Aravinda; Jackowski, Marcel P; Mekkaoui, Choukri; Chen, Howard; Dai, Guangping; Reese, Timothy; Kostis, William J; Maurovich-Horvat, Pal; Ruskin, Jeremy; Hoffman, Udo; Sosnovik, DavidBackground: The study of myofiber reorganization in the remote zone after myocardial infarction has been performed in 2D. Microstructural reorganization in remodeled hearts, however, can only be fully appreciated by considering myofibers as continuous 3D entities. The aim of this study was therefore to develop a technique for quantitative 3D diffusion CMR tractography of the heart, and to apply this method to quantify fiber architecture in the remote zone of remodeled hearts. Methods: Diffusion Tensor CMR of normal human, sheep, and rat hearts, as well as infarcted sheep hearts was performed ex vivo. Fiber tracts were generated with a fourth-order Runge-Kutta integration technique and classified statistically by the median, mean, maximum, or minimum helix angle (HA) along the tract. An index of tract coherence was derived from the relationship between these HA statistics. Histological validation was performed using phase-contrast microscopy. Results: In normal hearts, the subendocardial and subepicardial myofibers had a positive and negative HA, respectively, forming a symmetric distribution around the midmyocardium. However, in the remote zone of the infarcted hearts, a significant positive shift in HA was observed. The ratio between negative and positive HA variance was reduced from 0.96 ± 0.16 in normal hearts to 0.22 ± 0.08 in the remote zone of the remodeled hearts (p<0.05). This was confirmed histologically by the reduction of HA in the subepicardium from −52.03° ± 2.94° in normal hearts to −37.48° ± 4.05° in the remote zone of the remodeled hearts (p < 0.05). Conclusions: A significant reorganization of the 3D fiber continuum is observed in the remote zone of remodeled hearts. The positive (rightward) shift in HA in the remote zone is greatest in the subepicardium, but involves all layers of the myocardium. Tractography-based quantification, performed here for the first time in remodeled hearts, may provide a framework for assessing regional changes in the left ventricle following infarction.Publication Left Ventricular Remodeling Following Myocardial Infarction Revealed with a Quantitative Diffusion MRI Tractography Framework(BioMed Central, 2012) Mekkaoui, Choukri; Huang, Shuning; Dai, Guangping; Reese, Timothy; Thiagalingam, Aravinda; Maurovich-Horvat, Pal; Ruskin, Jeremy; Hoffmann, Udo; Jackowski, Marcel P; Sosnovik, DavidA cardiac-tailored framework for 3D Diffusion Tensor MRI tractography is developed and used to characterize myofiber architecture in normal and remodeled myocardium. We show that myofibers in the subepicardium of the remote infarct zone become less oblique (more circumferential) as the heart dilates and remodels. This fiber realignment may play an important role in the loss of contractile function in the remote zone over time.Publication Myocardial infarct delineation in vivo using diffusion tensor MRI and the tractographic propagation angle(BioMed Central, 2013) Mekkaoui, Choukri; Huang, Shuning; Dai, Guangping; Reese, Timothy; Ruskin, Jeremy; Hoffmann, Udo; Jackowski, Marcel P; Sosnovik, DavidPublication Diffusion MR Tractography of the Heart(BioMed Central, 2009) Sosnovik, David; Wang, Ruopeng; Dai, Guangping; Reese, Timothy; Wedeen, VanHistological studies have shown that the myocardium consists of an array of crossing helical fiber tracts. Changes in myocardial fiber architecture occur in ischemic heart disease and heart failure, and can be imaged non-destructively with diffusion-encoded MR. Several diffusion-encoding schemes have been developed, ranging from scalar measurements of mean diffusivity to a 6-dimensional imaging technique known as diffusion spectrum imaging or DSI. The properties of DSI make it particularly suited to the generation of 3-dimensional tractograms of myofiber architecture. In this article we review the physical basis of diffusion-tractography in the myocardium and the attributes of the available techniques, placing particular emphasis on DSI. The application of DSI in ischemic heart disease is reviewed, and the requisites for widespread clinical translation of diffusion MR tractography in the heart are discussed.