| objective1. Using MRI to quantitatively measure the normal values of exophthalmoses, shortand long diameters of extraocular muscles, the thickness of fatty tissue at the inner side of eye ball and the T2 values of extraocular muscles and fat in order to establish the referent values of normal orbital structures for further study of Graves ophthalmopathy (GO).2. Using MRI to quantitatively measure the values of exophthalmos, short and long diameters of extraocular muscles, the thickness of fatty tissue at the inner side of eye ball in GO patients and comparing with that of normal values in order to analyze the histological basis of GO and to evaluate the MRI value in the diagnosis of GO.3. Using MRI to quantitatively measure the T2 values of extraocular muscles and fat and comparing with that of normal values in order to analyze the histopathological basis of GO and to evaluate the MRI value in the choice of therapeutic methods of GO.materials and methods1. Patients' data: 25 normal cases and 30 GO cases were included in the study. Among 25 normal cases were 9 males and 16 females aging from 19 to 65, averaging 40.13 years old. Among 30 GO cases were 12 males and 18 females aging from 18 to 65, averaging 40.03 years old.2. Examination method: All the cases were undergone MRI scan with spin echosequence, STIR (Short TI Inversion recovery) sequence. 20 of 25 normal cases and 21 of 30 GO cases were scanned with SE dual-echo sequence and SE dual-echo sequence with fat repression .3. Data analysis: All the images of GO group and control group were transferred and managed in the silicon-o2 post-disposing work station and PACS system in Nanfang hospital. The short and long diameters of extraocular muscles were measured on T1WI axial or coronal images, such as RLR (right lateral rectus), RMR (right medial rectus), RIR (right inferior rectus), RSO (right superior oblique), RSR(right superior rectus), LLR (left lateral rectus), LMR (left medial rectus ), LIR (left inferior rectus), LSO (left superior oblique ) and LSR ( left superior rectus). The ratios of short diameter to long diameter (R values) of extraocular muscles were calculated. The thickness of fatty tissue at the inner side of two eye balls and the values of exophthalmos were also measured. At the same time, the T2 values of RMR, RSR, RIR, LMR, LSR, LIR and the orbital fatty tissue were measured in the SE dual echo images.4. Statistical analysis: SPSS 10.0 was performed and all datum used x±s, independent t test, one-way-ANOVA and LSD. P<0.05 was regarded as statistical difference and P<0.0\ was regarded as significant difference.[result]—. The means (x±s) of exophthalmos, short diameters, long diameters and R values in all extrocular muscles, the thickness of fatty tissue at the inner side of eye ball and the T2 values of extraocular muscles and fat in 25 normal cases with MRL1. Exophthalmos values: R= 18.39±1.41mm, L = 18.39±1.41mm. Normal exophthalmos value was less than 20mm, with 18.39mm as average value.2. Short diameters of extrocular muscles: RLR =3.58±0.95mm, RMR = 3.25±O.68mm, RSR =3.63±0.72mm, RIR =3.85±1.07mm, RSO=3.32±0.71mm, LLR= 3.41±0.73mm, LMR= 3.38±0.79mm, LSR = 3.65±0.64mm, LIR = 3.97±0.99mm, LSO=3.37±0.64mm. Among all the extraocular muscles, the short diameter of inferior rectus was largest, following by superior rectus, lateral rectus and medial rectus. Superior oblique was the shortest.3. Long diameters of all extrocular muscles: RLR = 10.35±1.37mm, RMR = 9.02±1.49mm , RSR = 10.08±1.21mm , RIR = 8.23±1.34mm , RSO =5.75±1.01mm, LLR=10.88±1.88mm, LMR=9.31±1.52mm, LSR=9.83±1.22mm, LIR=8.15± 1.28mm, LSO=5.83±1.05mm. Among all the extraocular muscles, the long diameter of lateral rectus was largest, following by superior rectus, and medial rectus, inferior rectus. Superior oblique was the shortest.4. Rvalues of extrocular muscles: RLR =0.36±0.13, RMR =0.38±0.13, RSR = 0.36±0.07, RIR =0.48±0.16, RSO = 0.58±0.11, LLR = 0.34±0.08, LMR= O.38±O.ll, LSR=O.35±O.O8, LIR=0.49±0.13, LSO = 0.59±0.12. Among all the extraocular muscles, the R values of superior oblique was the largest, which meaned that its oval shape was more likely to be a circle. The R values of lateral rectus was the smallest, and its oval shape was more flat.5. Thickness of fatty tissue at the inner side of eye balls: R=:5.05±0.89mm,L = 4.60±5.40mm.6. The T2 of extraocular muscles and the fatty tissue: RMR=79.09± 10.85, RSR=80.90±8.91,RIR=85.05±6.89, LMR=82.73±9.69, LSR=82.59±8.59, LIR = 83.77±7.85, fatty tissue: R=97.27±4.21, L=98.23±3.67.—. Comparison and analysis between the GO group and control group in the means ( x±s ) of exophthalmos, short diameters, long diameters and R values in extrocular muscles, the thickness of fatty tissue at the inner side of eye ball and the T2 values of extraocular muscles and fat with MRI..1. Exophthalmos values: The Exophthalmos value of GO group was larger than that of normal group. There was significant difference between these two groups in exophthalmos value, with P <0.01.2. Short diameters of extrocular muscles: The short diameter of extraocular muscles in GO group was longer than that in control group except for LSO. There was significant difference between these two groups in the short diameter of extrocular muscles, with P <0.05.3. Long diameters of extrocular muscles: There were no significant difference between the GO group and control group in the long diameter of extrocular muscles .4. R values of extrocular muscles: Except for LSR, The R value of extraocular muscles in GO group was larger than that in control group. There was statistical difference between the GO group and control group in the R values of extracular muscles5. Thickness of fatty tissue at the inner side of eye balls: The thickness of fatty tissue at the inner side of eye balls in GO group was larger than that in control group. There was significant difference between these two groups in the thickness of fatty tissue at the inner side of eye balls, with P <0.05.6. Using the maximum short diameter of extraocular muscles of the confidence interval limit in normal group as criterions, all the extraocular muscles in GO group were observed again by a radiologist to determine whether or not the extraocular muscles were enlarged. The results showed that the short diameter of at least one muscle was increased in 26 (87%). The RIRs were increased in 19 (63 % ) , the LIRs were increased in 17(57%), the RMRs were increased in 16(53%) ,the LMRs were increased in 18 (60% ) , the RSRs were increased in 14 (47% ) , the LSRs were increased in 12 (40% ) , the RLRs were increased in 9 (30% ) and the LLR were increased in 11 (37%) of the GO group.7. The T2 of extraocular muscles and the fatty tissue: There were statistically differences between GO group and control group in the T2 values of RMR, RSR, RIR, LMR, LSR, LIR .But there was not statistically different in fat tissue between there two groups .[conclusion]1. The enlargement of extraocular muscles was one of the reasons leading to exophthalmos, especially in inferior rectus and medial rectus, following by superior rectus and lateral rectus. The short diameter played an important role in the thickness of the extraocular muscles and was one of the main reasons of exophthalmos, but the long diameter did not. Thus, if the extraocular muscles were not shown obvious thickness, the R values was helpful in the diagnosis of GO.2. The increment of fat was one of the main factors leading to exophthalmos, too. Through measuring the thickness of the fatty tissue at the inner side of eye ball, we can judge the increment of the fat tissue in ocular cavity effectively and simply.3. By the comparison of the T2 values of the extraocular muscles and the fatty tissue between GO group and the control group, there was statistical difference in T2 values of extraocular muscles between GO group and the control group but no statistical difference in fatty tissues. We proposed that the enlargement of extraocular muscles was related to edema, however, the enlargement of fatty tissues was onlyhyperplasia. This proposal is helpful in the therapy of GO patients.
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