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J. Chen, Q. Wang, H. Zhang, S. Chen, S. A. Wickline, S.-K. Song; Diffusion Tensor MRI Detects Photoreceptor Degeneration in Mouse. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3002.
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Retinitis pigmentosa is a family of neurodegenerative retinaldiseases. However, limited methods are available to detect degeneratingphotoreceptors (PR) during disease progression. This study aimedto develop non-invasive MRI technique for detecting PR degenerationin a mouse model of retinitis pigmentosa.
In vivo diffusion tensor MRI (DTI) were performed on 2-4 monthsold rd1 (n = 6) and C57/BL6 mice (n = 6) at 11.74T. MR imageswere acquired with 0.4 mm thickness and 23 x 23 µm2 resolutionafter 2X interpolation. MRI determined cell orientation, axial(DA) and radial diffusivity (DR), and fractional anisotropy(FA) were quantified. A p < 0.05 was accepted as statisticalsignificance for data comparison using Student t-test.
Three layers in the control retina and a single layer in therd1 retina were detected by MRI (Figs 1A & B). DTI measuredcell orientation was radial in the outer retina layer of control,but was circumferential in the rd1 retina and the inner retinalayer of control (Figs 1C & D). Degeneration of radiallyaligned PR in the rd1 retina was confirmed by histology (Figs1E & F). Quantitative analysis showed that FA of the rd1retina was comparable to FA in the inner and middle layers ofcontrol but was lower than FA in the outer layer (Fig. 2A).However, the rd1 retina exhibited higher DA and DR than allretina layers of control (Figs. 2C & D).
We reported the first in vivo DTI study of the retina. The MRI-detectedcell structure and FA in the rd1 retina delineates the degenerationof PR. The elevated DA and DR in the rd1 retina might reflectthe injury of remaining neuron cells. Thus, DTI may allow specificdetection of the PR injury in vivo.
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