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BackgroundDiffusion Tensor Imaging (DTI) quantifies the amount ofanisotropic diffusion exhibited by biological tissues. Pro-cessing DTI images allow a 3D visualization of the fiberarchitecture by tracking the fiber trajectories within thetissue. Experimental evidence has shown that the myocar-dium undergoes remodeling as myocardial infarction pro-gresses over time[1]. The aim of this study is to investigateand compare the fiber architecture in an infarcted porcineheart using DTI at 1.5T and 3T, to analyze the effect ofhigh field magnets in imaging.MethodsEx-vivo DTI was performed on an infracted pig heart on1.5T (Avanto, Siemens Hea lthcare, Germany) and 3T(Tim Trio, Siemens Healthcare, Germany) MRI scan-ners. Infarcts were created in the apex region (Fig 1) byoccluding the left ante rior descending coronary artery.After 22 days, the hearts were dissected and formalinfixed for 6 months. A diffusion-weighted echo planarimaging sequence was used to acquire multi-slice shortaxis views covering the ventric les in the excised heart.Imaging parameters included: diffusion encoding direc-tions=256; TE=90ms; TR=7000(1.5T), 6600(3T) ms; slicethickness=2mm; matrix=128x128; FOV=256x256mm2;b-values=0,1000s/mm2; slices=37(1 .5T), 42(3T); isotro-pic resolution of 2x2x2mm. The images were masked tosegment the left ventricular myocardium (LVM).Explore DTI [2], was used to obtain a tensor map andtrack the fibers using a deterministic algorithm. For thisanalysis, fractional ani sotropy (FA) and the anglebetween the longest eigenvectors (V1) of the twosuccessive voxels were set to 0.2 and 45 degrees respec-tively. The lower limit of the length of the fibers wasvaried from 2mm to 30mm to see the correspondingchange in fiber tracts near the infracted region of theLVM obtained from both 1.5T and 3T scanners.ResultsFig 1 shows the magnitude image displaying the infarctwith thin myocardial wall. Fig 2 displays 3D visualizationof the fiber tracts in the LVM. In Fig 2 the upper rowand the lower row displays data from 3T and 1.5T scan-ners respectively. From left to right the lower limit of thefiber length was varied in the analysis to track the short

Diffusion tensor imaging of formalin fixed infarcted porcine hearts: a comparison between 3T and 1.5T