| Background and Objective: Optic nerve (ON) was an important part of optic pathway, optic canal (OC) was the narrowest part of ON to cranial cavity, so pathological changes in OC could affect directly ON. ON was one of the most common pathological changes positions, they often showed clinically vision decrease or blindness, which affecting the life and live quality of patients. For right treatment for ON pathological changes and improving efficiency, it was the key to find early and diagnose correctly. Some studier researched the normal MRI findings of ON and OC and diagnosis for ON pathological changes early, but their results and their methods were different, and they discussed little about imaging diagnostic value about the measurement of ON pathological changes. At present, when imaging technology high-speed developing, acknowledged and theories should be renewed and updated. We researched ON and OC dissection conformation and diameter measurement using multi-slice CT (MSCT) and MRI scanning method to set up standard for diameter measurement for every segment in normal adult ON and OC, and discuss imaging findings of dissection conformation and diameter changes for ON and disease related to ON on the basis of standard for diameter measurement, in order to improve CT examine and ON measurement application value in clinical diagnoses.Material and method: (1) Data: Choosing random 60 adult and healthy volunteers without eye and encephalic disease and without eyesight impediment, carrying out CT and MRI scanning, including 40 males and 20 female; 18 to 60 years old; mean age, 38.5 years. At the same time carrying out CT and MRI scanning for 50 patients with ophthalmic symptoms suspected ON disease; 18 to 69 years old; with 1 hour to 3 months course of diseases. 42 patients was treated for sight impediment for the first time, 8 patients were with other clinical symptoms at first, then emerged ophthalmic symptoms; 38 patients with different degree of eyesight decline, 12 patients losing light feeling, 6 patients with exophthalmos, 7 patients with headache and vomit.There were 21 patients with trauma, 5 patients with ON meningioma, 3 patients with glioma, 7 patients with intracranial hypertension, 5 patients with ON atrophy, 6 patients ON implicated by inner socket tumour, and 3 patients with optic neuritis in 50 patients. (2) Method: Using GE/ Light Speed PlusCT/4i multi-slice spiral CT device and German Siemens MRI device. The base line for CT and MRI cross section image built up on the basis of AB line; vertical line of AB line was taken as coronal scanning base line. OC scanning used HRCT cross section and coronal scanning, scanning parameters: 120KV, 240mA, 2.5mm, 3.75mm/s HS, matrix 512×512. ON was reconstruction using standard arithmetic, OC was reconstruction using bone arithmetic, then was transferred to AW4.0 workstation with a section thickness of 1.25mm, interval gap of 1.25mm, MRI used SE sequence, regular row cross section, coronal and sagittalis surface scanning with the parameters of a section thickness of 3mm, imaging limit of 230mm×230mm, matrix 256×256, T1WI: TR/TE=450/15ms, T2WI: TR/TE=6000/90ms, and average twice collection. Coronal surface scanning added Fs-TSE-T2 sequence in addition with the parameters of a section thickness 3mm, imaging limit 250×250mm, matrix 256×256, TR/TE=5000/119ms, and average twice collection. (3) Measured the length and thickness of all wall of OC with vernier caliper (exact to 0.02mm) on axes and coronal site and reconstruction sagittalis image attained from multi-slice spiral CT scanning, and calculated the area of ON socket ora, central section and skull ora (the calculation formula for ellipse area is S=πab a is 1/2 long dia, b is 1/2 short dia). Measured the cross dia and up and down dia on all stages of ON with vernier caliper on MRI cross section and sagittalis T1W1, measured point was 8 mm behind ball and canal inner stage and encephalic stage. Measured dia of inner socket ONF (optic nerve fiber) and ON on coronal position FS-TSE-T2, measured point was 4 mm and 8 mm behind ball and socket tip, and calculated the ratio of ONF/ON inner socket. (4) Carried out CT and MRI scanning for staring nerves and OC pathological changes using the same CT and MRI scanning sequence and scanning parameters, and analyzed images. Carried out image measurement and imagine analysis with double blind method.Result (1) OC central section was narrowest for OC, its cross dia was 4.57+0.44 mm, cross section area was 18.05±3.74mm2. Inner wall of OC central section was thinnest, its thickness was 0.58±0.37mm. Inner side wall of OC was longest, its long dia was 11.76±2.54mm. (2) The dia of every section of ON was different, it was 5.21±0.27 mm behind 4 mm of ball, it was 4.43±0.23 mm behind 8 mm of ball, it was 3.47±0.28 mm on socket tip, intracanalicular optic nerve was 3.46±0.36 mm, intracraial optic nerve was 3.92±0.41 mm. (3) MRI coronal Fs-TSE-T2 sequence measured the ida of inner socket ONF and ON, it was found that suburalhoid became thinner from front to back, it was narrowest on socket tip. The ratio of ONF/ON dia was become bigger from front to back, it was 0.57±0.03 behind 4 mm of ball and 0.58±0.04 behind 8 mm of ball, and 0.62±0.05 at socket tip. There was no significant difference between sex and age group (P>0.05). (4) Among 13 patients with OC fracture, 5 patients' fracture slice went in OC resulting canal dia and area becoming small and ON appearing break or extrusion symptom, and the other OC fracture without change of canal dia and area, which was incorporated into ON contusion. 8 patients with simply inner socket ON contusion, CT and MRI findings appeared ON becoming thicker, more than 5.5 mm, 3 patients with suburalhoid becoming bigger and the ratio of ONF/ON decreasing to 0.52, 5 patients with ONF swelling resulting in suburalhoid becoming thinner and the ratio of ONF/ON increasing to 0.63. 5 patients with ON meningioma all appeared ON becoming thicker, but its ONF configuration and dia line not changed, suburalhoid configuration and width abnormity, ONF/ON minishing, 1 patients' ratio less than 0.47. For 3 patients with ON glioma, their ON became thicker on the shape of shuttle or bar; MRI showed that ONF configuration abnormity on pathological changes sites, suburalhoid of pathological changes sites became narrower in abnormality resulting in the ratio of ONF/ON increased distinctly. 7 patients with intracranial hypertension all showed ON becoming thicker, MRI showed double side suburalhoid both enlarged, due to ON becoming thicker apparently, ONF wasn't found changes, the ratio of ONF/ON less than 0.55. Among 5 patients with optic nerve atrophy, 2 patients' ON didn't change on dia, 3 patients' atrophy thinner, but due to ONF becoming thin, the value of suburalhoid increase relatively, and ONF/ON becoming small. All optic nerves become thick in 3 cases of optic neuritis, MRI findings are ONF became thicker with asymmetry, suburalhoid became thinner, and ONF/ON increased. Transfer lump, haemangioma, inner socket haematoma and inflammative fake lump affect ON in 6 cases of inner socket pathological changes, it will appear that ON become thin under pressure, that suburalhoid under pressure in MRI findings and that ONF/ON increase.Conclusion:1. The middle part of optic canal of normal adult was narrowest, and its inner side wall was thinnest, so it was easy to arouse optic canal fracture and affect canal dia and area, that resulted in inside canal optic nerves damage.2. The stage of 4 mm behind ball of orbital optic nerve was thickest, it tapered off behind that.3. MRI coronal section Fs-TSE-T2 sequence could distinguish optic nerve figure, optic nerve fiber and suburalhoid. The ratio of ONF/ON became large gradually from front to bake in orbital optic nerve.4. It could be found that the ratio of ONF/ON became large in optic nerve contusion, meningioma of optic nerve, optic nerve glioma, intracranial hypertension, optic nerve atrophy, optic neuritis and etc. Considering the other MRI findings, it should help to diagnose.Innovation:1. TO set up the ratio of optic nerve fiber and optic nerve inside orbit of normal adult on the basis of the MRI coronal section Fs-TSE-T2 sequence, to perfect optic nerve pathway measurement method.2. TO discuss diagnostic value on change of ratio of optic nerve fiber and optic nerve in pathological changes, such as optic nerve contusion, meningioma of optic nerve, glioma, intracranial hypertension, optic nerve atrophy, optic neuritis and etc.
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