Relaxation time constants and apparent diffusion coefficients of rat retina at 7 Tesla

Abstract

MRI has recently been applied to study the retina in vivo. Measurements of relaxation time constants (T 1 , T 2 , and T 2 *) and the apparent diffusion coefficient (ADC) of the retina would be useful to systemically optimize structural, physiological, and functional MRI contrasts. MRI studies were performed on 12 anesthetized and paralyzed rats. High-resolution T 1 , T 2 , T 2 * and ADC of the rat eyes were measured at 50 3 50 3 800 lm at 7 Tesla. Profiles of T 1 , T 2 , T 2 * and ADC across the retinal thickness were analyzed. Region of interests of three layers across the retinal thickness were tabulated. This study demonstrated that high resolution T 1 , T 2 , T 2 * and ADC of the rat retina could be imaged. Profile analysis of T 1 , T 2 , T 2 * and ADC across the retinal thickness were helpful to minimize partial volume effects. T 1 , T 2 , T 2 * and ADC of the rat retina were overall similar to those of the brain. Quantitative T 1 , T 2 , T 2 * and ADC may change in retinal diseases and their measurements could help to stage retinal disease progression and monitor therapeutic intervention.

MRI of rod cell compartment-specific function in disease and treatment in vivo

“…ADC can be thought of as a barrier index: the more barriers water hits as it diffuses, the lower the water mobility, and thus the lower the ADC measured. In the retina, advantage is taken of this property and the fact that the subretinal space (SRS) expands several fold in light compared to that in dark (Adijanto et al, 2009;Chen et al, 2008Chen et al, , 2011Li et al, 1994a;Nair et al, 2010). In-line with this physiology, ADC MRI measures a greater axial ADC in the SRS in the light than in dark (Bissig and Berkowitz, 2012); the same extent of lightstimulated SRS expansion is measured independently of the presence of manganese (Fig.…”

Lamina-Specific Anatomic Magnetic Resonance Imaging of the Human Retina

“…In animal models, layer-specific anatomic, 10,14 relaxation time, 15,16 manganese-enhanced, [17][18][19] blood flow, 20 -22 blood volume 23,24 MRIs and multimodal functional MRI (fMRI) of physiologic 20,21,24,25 and visual 23,26,27 stimulation of the retina have been reported. Many of these studies showed lamina-specific retinal resolution.…”

Layer-Specific Manganese-Enhanced MRI of the Retina in Light and Dark Adaptation

“…MRI, by contrast, offers depth-resolved information with large field of view. MRI has recently been applied to image anatomical layers, [4][5][6] relaxation time and diffusion constants, [6][7][8] blood-oxygenation level dependent (BOLD) responses to physiological 5 and visual [9][10][11] stimulations, and quantitative blood flow 12,13 of the retinas in animal models. These approaches have been applied to study retinal degeneration, 5,12 diabetic retinopathy, 14 and glaucoma 15 in animal models.…”