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AJNR - American Journal of Neuroradiology

Published ahead of print on April 3, 2008
doi: 10.3174/ajnr.A1002

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Signal Intensity of the Motor Cortex on Phase-Weighted Imaging at 3T

S. Kakeda^a, Y. Korogi^a, K. Kamada^a, N. Ohnari^a, J. Moriya^a, T. Sato^a, M. Kitajima^b, H. Hasnine^c and N. Hirata^c

^a Department of Radiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu, Japan
^b Department of Radiology, Kumamoto University School of Medicine, Tokyo, Japan
^c GE Yokogawa Medical Systems Ltd, Tokyo, Japan

View larger version (82K): [in this window] [in a new window]   Fig 1. Comparison of various TEs in the 3 different techniques (magnitude, phase, and phase-weighted imaging) performed in a healthy volunteer (a 37-year-old man): magnitude images with TEs of 12 (A), 28 (B), 40 (C), and 80 ms (D); phase images with TEs of 12 (E), 28 (F), 40 (G), and 80 ms (H); and phase-weighted images with TEs of 12 (I), 28 (J), 40 (K), and 80 ms (L). The gray-to-white-matter contrast on magnitude images (A–D) is poor in all TEs. The gray-to-white-matter contrast on the phase (E–H) and phase-weighted images (I–L) increases by increasing the TE (asterisk versus arrowhead). The heightened contrast between motor (large arrow) and other cortices (small arrow) is most apparent on the phase-weighted image with a TE of 40 ms (K). The definition between motor (large arrow) and other cortices (small arrow) is poor on the phase-weighted image with a TE of 80 ms (L), due to the decrease in signal intensity of the other cortices.

View larger version (18K): [in this window] [in a new window]   Fig 2. Distribution of signal intensity in the motor cortex according to the patient's age on phase-weighted (A), phase (B), and magnitude images (C). In all subjects older than 20 years, the motor cortex on phase-weighted images was classified as grade II or III. The frequency of grade III on a phase-weighted image was higher than that on the phase and the magnitude images.

View larger version (37K): [in this window] [in a new window]   Fig 3. Magnitude (A), phase (B), and phase-weighted images (C) obtained in a 14-year-old girl. The signal intensity of the bilateral motor cortices (arrows) on the phase-weighted image (C) is definitely hypointense (grade III) in comparison with that in other cortices.