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AJNR - American Journal of Neuroradiology

Published ahead of print on October 10, 2007
doi: 10.3174/ajnr.A0772

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3D Time-Resolved Contrast-Enhanced Cerebrovascular MR Angiography with Subsecond Frame Update Times Using Radial k-Space Trajectories and Highly Constrained Projection Reconstruction

Y. Wu^b, N. Kim^a, F.R. Korosec^a,b, A. Turk^a, H.A. Rowley^a, O. Wieben^b, C.A. Mistretta^a,b and P.A. Turski^a

^a Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wis
^b Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wis

View larger version (68K): [in this window] [in a new window]   Fig 1. Schematic diagram of the HYPR reconstruction algorithm. Data were acquired by using undersampled radial trajectories. Images in the top row were reconstructed by using filtered backprojection. Images in the bottom row were reconstructed by using the HYPR method. All processing was performed on the source images, and the resulting maximum-intensity-projection images are shown. The low attenuation of vessels (high sparsity) in the source images makes them amenable to HYPR processing. For the HYPR processing, note that the sagittal sinus that appears in the composite image is suppressed following multiplication by the weighting image for frame 1.

View larger version (126K): [in this window] [in a new window]   Fig 2. Comparison of in-plane resolution and artifacts for Cartesian TRICKS (0.94 x 1.5 mm) (A, B) and HYPR TRICKS (0.47 x 0.47 mm) (C, D). Arrows in the Cartesian TRICKS images show the ghosting and black band artifacts resulting from fluctuations in signal intensity occurring during acquisition of data for a single frame, caused by changes in the concentration of contrast material. More rapid and larger fluctuations lead to more severe artifacts.

View larger version (115K): [in this window] [in a new window]   Fig 3. Comparison of Cartesian TRICKS timeframes (the 3 images with the black frames) and HYPR TRICKS timeframes from a patient with AVM. The frame update times are 0.4 seconds for HYPR TRICKS and 2.4 seconds for Cartesian TRICKS.