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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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American Journal of Neuroradiology 29:1171-1175, June-July 2008
© 2008 American Society of Neuroradiology

BRAIN

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

Please address correspondence to Shingo Kakeda, MD, Department of Radiology, University of Occupational and Environmental Health School of Medicine, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan; e-mail: kakeda{at}med.uoeh-u.ac.jp

BACKGROUND AND PURPOSE: It is known that the motor cortex shows hypointensity on T2-weighted images in older patients. The goal of this study was to assess the signal intensity of the motor cortices on the phase-weighted imaging performed with a Windows-based software program that we developed ourselves.

MATERIALS AND METHODS: All studies were performed at 3T MR imaging. First, the TE for the phase-weighted image was optimized; the best contrast between the motor and other cortices was obtained with a TE of 40 ms. The study population consisted of 45 healthy subjects (23 females, 22 males; mean age, 32.1 years). The signal intensity of the motor cortices was divided into 3 grades by 2 neuroradiologists in comparison with that of the superior frontal cortex (SFC): In grade I, the motor cortex was isointense to the SFC; in grade II, the motor cortex was slightly hypointense to the SFC; and in grade III, the motor cortex was markedly hypointense to the SFC.

RESULTS: The motor cortex was classified as either grade II or III in all subjects older than 20 years of age on the phase-weighted images. Even at 10–19 years of age, the grade II or III appearance was found in 14 (88%) of 16 motor cortices (8 subjects) on the phase-weighted images.

CONCLUSION: In adolescents, the motor cortex is hypointense to other cerebral cortices on phase-weighted MR imaging, which probably reflects differences in the concentration of nonheme iron and/or in the tissue architecture.