The Art of 7T Imaging (Slideshow)

System-level brain study at a nearly microscopic scale. That’s what neuroscience researchers have been relishing since the installation of Cleveland Clinic’s 7-tesla (7T) MRI scanner in 2013. Here are a few glimpses of what it makes possible.

<p>A two-dimensional, T2*-weighted gradient echo image obtained with 7T MRI (0.25 × 0.25 mm² in-plane resolution; 1.5 mm slice thickness; 9 min 54 sec scan time). With more than double the field strength of 3T MRI, 7T scanning produces in vivo images at spatial resolutions up to five times those possible at clinical field strengths. By marrying the spatial resolution of CT with the superior soft-tissue contrast of MRI, 7T yields dramatic gains in signal and contrast that may enable more accurate diagnosis and advance neuroscience research.</p>

<p>Fiber tractography images of the corpus callosum overlaid on the T1-weighted anatomic image. Using 7T MRI, we can visualize the submillimeter-size fiber tracts. Tractography results are color-coded according to the direction of the fiber. (1.0 mm³ isotropic resolution, 12 min scan time)</p>

<p>Axial (left) and sagittal (right) views of functional MRI results at 7T using a flashing checkerboard visual stimulus. These results show activation in the visual cortex and the lateral geniculate nucleus. (1.25 mm³ isotropic resolution)</p>

<p>Susceptibility-weighted imaging (SWI) in a healthy volunteer. SWI shows susceptibility differences between tissues and is sensitive to venous blood and iron. In general, higher-field-strength systems such as 7T MRI produce better contrast with SWI. (0.43 × 0.43 × 0.8 mm³ resolution, 7 min scan time)</p>

<p>Magnetic resonance angiography (MRA) image without contrast in a healthy volunteer. At 7T, there is a higher contrast between blood vessels and tissue than at lower field strengths, making direct imaging of small vessels possible. 7T imaging promises to play an important role in the study of small-vessel abnormalities. (0.3 × 0.3 mm² in-plane resolution; 19 mm slab thickness; 5 min 16 sec scan time)</p>

<p>MRIs of white matter in a patient with advanced MS taken at 7T (left) and 1.5T (right). While 1.5T shows a uniform field of signal hyperintensity (brightness), 7T allows disease details to be appreciated with greater resolution. Note the myriad rounded lesions that appear superimposed at 7T but appear coalesced at 1.5T. The 7T image also reveals a black dot at the center of most lesions (arrow), which represents the effects of blood flow in a central vein. This association, well established from microscopic pathology, can now be demonstrated on MRI with the advent of 7T, which may help distinguish MS from numerous look-alikes at lower magnetic field.</p>

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Images were provided by Mark Lowe, PhD, Cleveland Clinic’s Director of High-Field MRI; Sehong Oh, PhD, project staff scientist in Cleveland Clinic’s Imaging Institute; and Stephen E. Jones, MD, PhD, Vice Chair for Research and Academic Affairs in the Imaging Institute.

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