Related Experiment Videos
STIR MR imaging of the orbit
S W Atlas1, R I Grossman, D B Hackney
1Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia 19104.
Abstract:
Fifteen patients with CT-documented orbital lesions were evaluated with MR imaging at 1.5 T with both conventional spin-echo (SE) and short inversion time inversion recovery (STIR) sequences. Fat signal was reliably nulled at inversion times of approximately 120-200 msec in all cases, thereby allowing clear detection of all retrobulbar lesions and normal structures on STIR images as markedly hyperintense relative to fat. All lesions were also clearly depicted on SE images; in fact, short repetition time/short echo time SE sequences were at least as useful as STIR images for illustrating anatomic structures and mass lesions, and in a much shorter scanning time. Separation of optic nerve from perioptic subarachnoid space was clear on SE images, but often difficult or impossible on STIR images owing to the relatively high intensity of normal optic nerves on STIR images. The synergism of relaxation prolongation with STIR actually resulted in loss of information, as any ability to separate the effects of T1 from T2 on signal intensity was impossible when STIR was the sole pulse sequence. We believe that more information is obtained with standard SE sequences than with STIR sequences, and therefore SE remains the method of choice for orbital MR imaging.
Insights
Conventional spin-echo (SE) MRI sequences are superior to short inversion time inversion recovery (STIR) for evaluating orbital lesions. SE sequences provide clearer visualization of orbital anatomy and lesions, especially the optic nerve, compared to STIR.
Area of Science:
- Radiology
- Medical Imaging
- Ophthalmology
Background:
- Orbital lesions require accurate imaging for diagnosis and management.
- Magnetic Resonance Imaging (MRI) is a key modality for evaluating orbital pathology.
- Comparing different MRI sequences is crucial for optimizing diagnostic yield.
Purpose of the Study:
- To compare the efficacy of conventional spin-echo (SE) and short inversion time inversion recovery (STIR) MRI sequences in evaluating orbital lesions.
- To determine the optimal MRI technique for visualizing orbital anatomy and pathology.
Main Methods:
- Retrospective evaluation of 15 patients with CT-documented orbital lesions.
- MRI at 1.5 T using both conventional SE and STIR sequences.
- Analysis of lesion conspicuity, anatomic detail, and fat suppression effectiveness.
Main Results:
- STIR sequences effectively nulled fat signal, enhancing retrobulbar lesion detection.
- SE sequences, particularly short repetition time/short echo time, were equally effective in depicting lesions and anatomy.
- SE sequences provided superior separation of the optic nerve from the perioptic subarachnoid space compared to STIR.
- STIR sequences sometimes obscured details due to high signal intensity of normal optic nerves.
Conclusions:
- Conventional SE sequences offer more comprehensive information for orbital MRI than STIR sequences.
- SE sequences are considered the preferred method for orbital MRI due to better visualization of critical structures.
- The combination of SE and STIR may not always be synergistic, with SE alone often providing sufficient diagnostic detail.