Fast Three-Point Dixon MR Imaging of the Retrobulbar Space with Low-Resolution Images for Phase Correction: Comparison with Fast Spin-Echo Inversion Recovery Imaging
Frank J. Rybickia,
Robert V. Mulkerna,
Richard L. Robertsona,
Caroline D. Robsona,
Taylor Chunga and
Jingfei Maa
a From the Department of Radiology (F.J.R.), Brigham and Women's Hospital and Harvard Medical School, Boston, Mass; Department of Radiology (F.J.R., R.V.M., R.L.R., C.D.R.), Children's Hospital and Harvard Medical School, Boston, Mass; Department of Diagnostic Imaging (T.C.), Texas Children's Hospital, Houston; and Department of Diagnostic Radiology (J.M.), Anderson Cancer Center, Houston, TX.
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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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FIG 2. Coronal MR images of the retrobulbar space in a 12-year-old girl with dental braces.
A, FSEIR image shows that the evaluation of orbits is limited by artifact from the dental braces. Note the improved contrast between gray and white matter because of the additional T1 weighting caused by the inversion pulse.
B, 3PD water-plus-fat image (3000/85/8/1) offers dramatically improved signal; the artifact from the dental braces has a sharper margin.
C, 3PD pure water image (3000/85/8/1) shows superior anatomic detail compared with FSEIR.
D, 3PD pure fat image (3000/85/8/1) shows substantial signal from fat-containing structures outside the retrobulbar space.
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