MR imaging of olfactory bulbs and tracts.

Olfactory bulbs are easily detected on coronal T1-weighted MR images. They are situated almost symmetrically opposite either side of the lower end of the olfactory sulci, and, on sagittal images, they are observed as thin soft-tissue bands immediately beneath the frontal lobe base. On axial images they are shown as oval, paramedian structures of intermediate intensity. Visualization of the olfactory tract, however, is not always possible. Our study reveals that, on axial images, detection of the olfactory bulb depends on technical factors; we recommend a 256 x 256 matrix, a 3-mm-thick slice, and less than a 0.6-mm gap. Despite the lack of complete visualization of olfactory bulbs and tracts, MR may be effective in demonstrating diseases of these entities.