| Objective:Using manganese-enhanced magnetic resonance imaging to observe the visual pathway of normal and optic nerve injury rats. Evaluate the value of manganese-enhanced magnetic resonance imaging. Normal visual pathway were visualized and the sites of the optic nerve injury were early detected. Find out a new image diagnosis of visual pathway.Methods:Healthy adult SD rats (N=16) were divided into 3 groups at random.1) Dose-response experiment (N=6):MRI was performed 24 hours after right eyes intravitreal MnCl2 injection. The dose were 10nmol,50nmol,200nmol,300nmol and 500nmol respectively. In order to study the optic nerve, the average signal intensity of the right and the left optic nerve in MRI images were measured under different doses. The contrast-to-noise ratio (CNR) of the optic nerve was calculated. Draw a dose-response curve of Mn2+ to analyze the correlation between different doses (Abscissa is the total amount of Mn2+, vertical axis is the CNR values).2) Experimental-control experiment (N=5):Right eye was the experimental group; left eye was the control group. MRI was performed 24 hours after right eyes intravitreal MnCl2 injection. The dose was 300nmol. The average signal intensity was measured (bilateral retina, optic nerve, optic chiasm, optic tract, lateral geniculate body and superior colliculus) and SNR was calculated. The enhancement in the visual pathway was compared. Paired t test was used for statistical analysis.3) Comparison of optic nerve injury and non-injury experiment (N=5):First, produced mechanical injury model on right optic nerve of adult SD rats. MRI was performed 24 hours after right eyes intravitreal MnCl2 injection. The doses were 300nmol. Recording MRI images of the visual pathway of optic nerve injury side and the other side. Compare with the data of control group and calculate SNR. The average signal intensity in MRI images of both visual pathways was measured. The changes of signal intensity in optic nerve injury rats were studied. Variance to analyze was used to analyze of the date.Results:1. The relationship between the dose and CNR in dose-response experimentThe relationship between the dose and CNR is curvilinear correlation (P=0.026, r=0.865). There are strong positive correlation between the dose and CNR. Showing that the higher dose of Mn2+, the higher degree of enhancement of MRI images.2. Comparison of the images in both sides of the visual path waysAfter right eye intravitreal Mn2+ injection, SNR of right visual patyway (include retina, optic nerve, optic chiasm, optic tract, lateral geniculate body, superior colliculus) are higher than the other side in MEMRI. After intravitreal 300 nmol Mn2+ injection the MRI images was significantly enhanced.3. Statistical analysis of the optic nerve injuryThe MRI images from the retina to the optic nerve injury site were significantly enhanced. The remote parts of the injured optic nerve were not enhanced.Conclusion:1. MEMRI can be clear, accurate display of the visual pathway in rats.2. The higher dose of Mn2+ injected into the vitreous, the higher degree of enhancement of MRI images.3. Mn2+ accumulated in the optic nerve injury site, because damage to the optic nerve axons. The high signal intensity was showed of the injured site in MEMRI images. It is more conducive to diagnosis of traumatic optic nerve injury. |
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