| Purpose: To Combine and compare the images of T2W-SPIR and STIR-FLAIR sequences for the orbit, to evaluate the diagnostic ability of STIR-FLAIR sequence for the orbital lesions, which suppresses signal from both fat and water.Materials and Methods: 51 patients (60 abnormal orbits) and 4 healthy volunteers were recruited for study. All the patients'clinical and MRI data was collected and co-related with the results of pathology and clinical manifestation for accurate diagnosis. Data was evaluated from the transverse images of the STIR-FLAIR and T2W-SPIR sequences though subjective and objective methods and from 6 aspects, such as the appearance of the normal orbit and the adjacent structures, 51 patients(60 abnormal orbits), choroidal lesions, extraocular muscle disease(Graves'disease),optic neuropathy and orbital vascular lesions.Results: 1. The normal orbital and adjacent structures have different appearance in the two sequences, STIR-FLAIR and T2W-SPIR.2. 51 patients(60 abnormal orbits): The interobserver reliability of the lesion scoring, including the quality of the images (artifacts), the lesion visibility and the relationship between lesion and surrounding structures, were assessed using a Kappa test. For the three aspects, STIR-FLAIR sequence's Kappa values were 0.827, 0.659, 0.645 respectively and for T2W-SPIR sequence they were 0.859, 0.803, 0.807. Compared to the images of T2W-SPIR sequence, STIR-FLAIR sequence's images had fewer artifacts(two-side P<0.05), higher lesion visibility(two-side P<0.05) and similar ability in assessing the relationship between lesion and surrounding structures(two-side P<0.05). In STIR-FLAIR sequence,the normalized signal intensity(Sn) of normal orbital structures such as orbital fat, orbital preseptal tissues, lacrimal gland and extraocular musles, were all slightly higher than they were in T2W-SPIR sequence(two-side P<0.05 for all of them), but the Sn vitreous body in T2W-SPIR sequence was apparently higher than STIR-FLAIR sequence(two-side P<0.05). In the STIR-FLAIR sequence, the Sn vitreous body was the lowest and the Sn extraocular muscles were the highest(two-side P<0.05 for all the comparisons) while comparing with other normal structures. By contrast, in the T2W-SPIR sequence the Sn vitreous body was the highest and the Sn extraocular muscles were similar to the Sn lacriaml gland with two-side P>0.05 while comparing with other normal structures. For the Sn lesions, they were higher than Sn extraocular muscles in STIR-FLAIR sequence while apparently lower than Sn vitreous body(two-side P<0.05 for all the comparisons). And, the STIR-FLAIR sequence had bigger signal intensity ratio(R)between the lesions and the vitreous body(two-side P<0.05), while the Rlesions/orbital fat was bigger in T2W-SPIR sequence with two-side P<0.05.3. Choroidal lesions: For this kind of disease, STIR-FLAIR sequence's images had lighter artifact, higher lesion visibility and higher ability in assessing the relationship between lesion and surrounding structures(two-side P<0.05 for all the three subjective assessments'comparisons). In STIR-FLAIR sequence, the Sn lesions were higher than both Sn orbital fat and Sn vitreous body with two-side P<0.05 for the both of them. In T2W-SPIR sequence, the Sn lesions and the Sn vitreous body were both higher than Sn orbital fat(two-side P<0.05 for both of them). Rlesions/ vitreous body in STIR-FLAIR sequence was bigger than in T2W-SPIR sequence(two-side P<0.05).4. Extraocular muscle disease(Graves'disease): All the 11 abnormal extraocular muscles were diagnosed by both of the two sequences. The outline of the 11 abnormal extraocular musles were displayed clearer in STIR-FLAIR sequence than T2W-SPIR sequence,while high signal around some abnormal extraocular muscles showed in T2W-SPIR sequence could not been seen in STIR-FLAIR sequence. In STIR-FLAIR sequence, the Sn abnormal extraocular muscles were higher than Sn normal extraocular muscles, Sn orbital fat and Sn vitreous body with two-side P<0.05 for all of them. In T2W-SPIR sequence, the Sn vitreous body were higher than Sn abnormal extraocular muscles, Sn normal extraocular muscles and Sn orbital fat(two-side P<0.05 for all of them). R abnormal extraocular muscles / vitreous body in STIR-FLAIR sequence was apparently bigger than in T2W-SPIR sequence(two-side P<0.05), and the R abnormal extraocular muscles / normal extraocular muscles in STIR-FLAIR sequence was slightly bigger than in T2W-SPIR sequence(two-side P<0.05) .While the R abnormal extraocular muscles /orbital fat between the two sequences were no significant different(two-side P>0.05).5. Optic neuropathy: The abnormal appearances of the 3 optic atrophy and 1 optic nerve violated by acute promyelocytic leukemia were displayed better in STIR-FLAIR sequence than in the T2W-SPIR sequence.6. Orbital vascular lesions: The two sequences had similar lesion visibility and the similar capability in assessing the relationship between the lesion and surrounding structures(two-side P>0.05 for both of them). In the STIR-FLAIR sequence, the Sn lesions were higher than Sn orbital preseptal tissues, Sn orbital fat and Sn vitreous body with two-side P<0.05 for all of them. In T2W-SPIR sequence, the Sn vitreous body were higher than Sn orbital preseptal tissues, Sn orbital fat and Sn lesions (two-side P<0.05 for all of them). Rlesions/ vitreous body in STIR-FLAIR sequence was bigger than in T2W-SPIR sequence(two-side P<0.05),while the Rlesions/orbital fat was bigger in T2W-SPIR sequence(two-side P<0.05).Conclusion: While imaging the orbit, compared with T2W-SPIR sequence, STIR-FLAIR sequence's images have fewer artifacts, higher tissue signal intensity contrast and higher lesion visibility. For the diseases which are related with choroid, STIR-FLAIR sequence is better than T2W-SPIR sequence not only in depicting but also in assessing the lesion range. For the optic neuropathy, the STIR-FLAIR sequence may be better too. For the extrocular abnormality of active Graves'disease, STIR-FLAIR sequence may be better than T2W-SPIR sequence owing to the better display for the outline of the abnormal extraocular, but for the inflammatory tissues'depiction, the T2W-SPIR sequence is better. For the orbital vascular lesions'diagnose, they have no different. To sum up, we recommend that STIR-FLAIR sequence has many benefits, especially when suspecting the lesions related with the eyeball(globe) and optic nerve, and when imaging these kinds of disease, STIR-FLAIR can take palce of T2W-SPIR sequence. |
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