Research Highlights - Bilateral Hip Imaging at 7T

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Bilateral Hip MRI at 7 Tesla - Clinical Role for High Spatial Resolution Imaging

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A 16 channel stripline transceiver RF coil was used, together with a B1 shimming algorithm aiming at maximizing B1+ in six regions of interest over the hips which were identified on axial scout images. Our successful results demonstrate that this approach effectively reduces inhomogeneities observed before B1 shimming and provides high joint tissue contrast in both hips, while reducing the required RF power. Critical to this success was a fast, small flip angle B1+ calibration scan that permitted the computation of subject specific B1 shimming solutions, a necessary step to account for large spatial variations in B1+ phase observed in different subjects.

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Multi slice coronal fat suppressed PD-TSE images (0.5/0.5/1.5 mm3) after B1 shim,  10 min acquisition)

 

Summary of the B1 Shim procedure. A. Left: Coronal scout image used for positioning three axial slices (yellow lines) through hip heads used for B1 shim. Right RIOs drrawn over the three axial slices enclosing both hip heads. Smaller inner disks were exclided because of a low SNR in entral bone tissue. B: the three axial views before B1 shim. Note some dark areas crossing the hip heads (arrows) C: same slices after B1 shim. Note the signal gain in previously dark areas. D: RF efficiency (ranging between 0 and 1) within the ROIs shown in A before B1 shim. Note the consistency between the location of RF efficiency trough and of dark signal (arrows). E: RF efficiency within the ROIs after B1 shim. Note the overall dramatic gain in RF efficiency. (corresponding improvement in anatomical coronal TSE hip images are show in Fig 3). F. Estimated transmit B1 maps (arbitrary units) for the 16 channel show for one of the axial slices. Left: magnitude (B1+) maps. Right B1+ phase maps relative to the first channel(set to uniformly zero degrees). The enire clibration was obtained in a 1min 44sec acquisition.

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Pre versus post shimming.

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3D Medic Post

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PD-TSE IMAGE AFTER B1-SHIMMING Resolution 0.5 x 0.5 x 1.5mm No gap

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High Resolution Bilateral Hip Joint Imaging at 7 Tesla - hip delamination.

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