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FIG 2. Axial MR images through the upper midbrain.
A, Axial T2-weighted image in a healthy control subject, a 55-year-old woman. A hypointense area, believed to be SNr, is located in the anteromedial part of the crus cerebri (arrow). No hyperintense gray matter area, representing the SN, is visible.
B, Proton density-weighted image in the same section as in A. The SN (n) is clearly identified as an area of hyperintense gray matter surrounded by the hypointense red nucleus (r) and the crural fibers (c).
C, T1-weighted image in the same section as in A. The SN is not evident.
D, Fast STIR image in the same section as in A. The SN (n) is readily identified as a structure with gray matter signal intensity. The red nucleus (r) with surrounding white matter and the crural fibers (c) are identified as areas with relatively low signal intensity.
E, Video-reversed fast STIR image onto which the hypointense areas on a T2-weighted image are superimposed (shaded areas). The hypointense area on the T2-weighted image includes the crural fibers and the anterior part of the SN.
F, Corresponding axial-section specimen obtained from a human cadaver.
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