A comparison of SWI HP-filtered-phase images (B and D) with Duvernoy’s india ink–stained results (A and C).16 Anterior (A and B) and posterior (C and D) mesencephalic structures are indicated. Arrow 1 indicates the crus cerebri; 2a, substantia nigra, pars reticulata; 2b, substantia nigra, pars compacta; 3, capsule of the red nucleus; 4a, red nucleus (vascularized region); 4b, red nucleus (nonvascularized region); 5, fascicula nigrale; 6, medial geniculate body; 7, superior colliculus; 8, intermediate area. Images A and C reprinted with permission from Duvernoy HM. Human Brain Stem Vessels. 2nd ed. Berlin, Germany: Springer-Verlag; 1999;206 –13.