Fat-suppression MR imaging of the orbit.

The effect of fat suppression on orbital MR imaging was tested by using a derivative of the Dixon method called chopper fat suppression in eight normal volunteers and eight patients with normal conventional orbital MR studies. Chopper fat suppression requires no postacquisition image processing or increased scan time and can be applied through a wide range of T1 to T2 weighting. In normal orbits, fat suppression was found to be advantageous for imaging the lacrimal gland and the optic nerve. Using fat-suppressed T1- or intermediate-weighted sequences, 2000/30 (TR/TE), the optic nerve was recognized by its high signal intensity relative to adjacent CSF, dural sheath, and surrounding fat. The technique minimized loss of anatomic detail by reducing chemical shift misregistration artifact. Disadvantages included an overall lower orbital signal/noise ratio. When used in conjunction with a TR/TE combination carefully selected for both anatomic region of interest and suspected pathology, the fat-suppression technique has the potential for improving the visualization of orbital lesions.