Demonstration of the medullary lamellae of the human red nucleus with high-resolution gradient-echo MR imaging.

BACKGROUND AND PURPOSE The human red nucleus is not a uniform structure. It is composed of caudally located magnocellular and rostrally located parvicellular subnuclei. In fact, the latter forms the bulk of the human red nucleus and can be subdivided histologically by two medullary lamellae into three parts. Because iron is deposited in the human red nucleus and gradient-echo sequences are more sensitive than spin-echo sequences in the detection of iron, a high-resolution gradient-echo MR sequence was used in this study to determine whether the medullary lamellae of the normal human red nucleus could be detected in vivo. METHODS Ten healthy volunteers (seven men and three women, 27-48 years old) were examined with a high-resolution T2-weighted gradient-echo MR sequence using a 1.9-T MR imager. The scanning parameters were 60/40/15 (TR/TE/excitations) with a flip angle of 20 degrees , a pixel size of 1 x 1 mm, and a slice thickness of 5 mm. RESULTS The medullary lamellae were depicted in all subjects in three imaging planes: coronal, oblique axial, and oblique sagittal. The signal intensity of the lamellae was consistently higher than that of other parts of the red nucleus on all images. With the lamellae, the parvicellular subnucleus of the human red nucleus can be divided into its subdivisions. CONCLUSION High-resolution gradient-echo MR imaging is capable of depicting the medullary lamellae of the normal human red nucleus in vivo.