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FIG 1. Coronal MR images of the retrobulbar space in a 3-year-old boy.
A, FSEIR image (2500/30/8/2) shows that nulling of fat from the inversion pulse effectively isolates the signal from the optic nerves. Structure is evident within the right optic nerve with these sequence settings.
B, 3PD water-plus-fat image (3000/85/8/1) shows both optic nerves as hypointense areas within a bright fat background. The internal structure is well depicted. Note the substantial signal from the sinuses, which is greatly nulled on the FSEIR image.
C, 3PD pure water image (3000/85/8/1) shows the optic nerves isolated from the surrounding fat. Substantial signal is present from water-containing tissue in the sinuses. Because of its relatively short T1, this signal is lost with the delay time in the FSEIR image.
D, 3PD pure fat image (3000/85/8/1) shows dramatic contrast and sharply defined margins between the water-containing structures (optic nerves and extraocular muscles) and retrobulbar fat.
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