High-Resolution 3D MR Microangiography of the Rat Ocular Circulation

Shih, Yen‐Yu Ian; Muir, Eric R.; Li, Guang; Garza, Bryan H. De La; Duong, Timothy Q.

doi:10.1148/radiol.12112033

Cited by 20 publications

(18 citation statements)

References 18 publications

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“…In addition to BF MRI, anatomical MRI has also been applied to study the retina using a variety of contrasts, such as T1 [45,46], T2 [45-47], balanced steady state free precession [48], diffusion [45,47], and manganese-enhanced [49-51], chromium-enhanced [52], microangiographic [53] MRI. Functional MRI based on BOLD [54,55,46], blood-volume [56,57], manganese-enhanced [58,50], balanced steady-state free precession [48], and diffusion [59] contrasts have also been demonstrated.…”

Section: Discussionmentioning

confidence: 99%

Decreased retinal–choroidal blood flow in retinitis pigmentosa as measured by MRI

et al. 2013

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Purpose To evaluate retinal and choroidal blood flow (BF) using high-resolution magnetic resonance imaging (MRI) as well as visual function measured by the electroretinogram (ERG) in patients with retinitis pigmentosa (RP). Methods MRI studies were performed in 6 RP patients (29-67 years) and 5 healthy volunteers (29-64 years) on a 3-Tesla scanner with a custom-made surface coil. Quantitative BF was measured using the pseudo-continuous arterial-spin-labeling technique at 0.5x0.8x6.0mm. Full-field ERGs of all patients were recorded. Amplitudes and implicit times of standard ERGs were analyzed. Results Basal BF in the posterior retinal-choroid was 142±16 ml/100ml/min (or 1.14±0.13 μl/mm2/min) in the control group and was 70±19 ml/100ml/min (or 0.56±0.15 μl/mm2/min) in the RP group. Retinal-choroidal BF was significantly reduced by 52±8% in RP patients compared to controls (P<0.05). ERG a- and b-wave amplitudes of RP patients were reduced and b-wave implicit times were delayed. There were statistically significant correlations between a-wave amplitude and BF value (r=0.9, P<0.05) but not between b-wave amplitude and BF value (r =0.7, P=0.2). Conclusions This study demonstrates a novel non-invasive MRI approach to measure quantitative retinal and choroidal BF in RP patients. We found that retinal-choroidal BF was markedly reduced and significantly correlated with reduced amplitudes of the a-wave of the standard combined ERG.

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Section: Discussionmentioning

confidence: 99%

Decreased retinal–choroidal blood flow in retinitis pigmentosa as measured by MRI

et al. 2013

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“…The animal preparation was similar to that reported previously. 14,15 Adult male Sprague–Dawley rats ( n = 26, 250–300g) were anesthetized with 2% isoflurane, intubated and ventilated (Harvard apparatus, Model 683, South Natick, MA). The respiratory rate of the ventilator was set between 57 and 60 stroke/min.…”

Section: Methodsmentioning

confidence: 99%

Quantitative Retinal and Choroidal Blood Flow During Light, Dark Adaptation and Flicker Light Stimulation in Rats Using Fluorescent Microspheres

Shih

Wang

Garza

et al. 2013

Current Eye Research

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Purpose The present study aimed to quantify retinal and choroidal blood flow (BF) during light, dark adaptation and flicker light stimulation using the microsphere technique. Materials and Methods Adult male Sprague–Dawley rats were anesthetized with isoflurane. Eyes were dark (Group I, n = 8), light (Group II, n = 8) adapted or stimulated with 10Hz flicker light (Group III, n = 10). Retinal and choroidal BF were measured by a previously established method, using a mixture of 8 μm yellow-green and 10 μm red fluorescent microspheres. The microspheres were counted ex vivo in the dissected retina and choroid and in the reference arterial blood under a fluorescent microscope. Results The choroidal BF was 64.8 ± 29 μl/min (mean ± SD) during dark adaptation, not significantly different from that during light adaptation (66.0 ± 17.8 μl/min). The retinal BF was 13.5 ± 3.2 μl/min during 10 Hz flickering light stimulation, significantly higher than that during dark adaptation in the control fellow eyes (9.9 ± 2.9 μl/min). The choroidal BF values were not statistically different between flicker stimulation and dark adaptation. Retinal BF was 11.6 ± 2.9 μl/min during light adaptation. Dark adaptation did not increase retinal BF (Group I, 8.2 ± 2.4 μl/min; Group II, 9.9 ± 2.9 μl/min). Conclusions These findings argue against a dark-induced or flicker-induced functional hyperemia in the choroid as a result of the demands of the outer retina. Retinal BF was not higher during dark adaptation. Our data support the conclusion that the inner retina has a higher energy demand in flicker conditions relative to dark.

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“…Heart rate and blood oxygen saturation level were continuously monitored by a MouseOx system (STARR Life Science Corp., Oakmont, PA) and maintained within normal ranges. An established CBV fMRI technique was employed (Mandeville et al, 1998) by using 30 mg/kg monocrystalline iron oxide nanoparticles (MION) at 11.7 T to minimize the BOLD contribution (Shih et al, 2011, 2012c). …”

Section: Methodsmentioning

confidence: 99%

Ultra high-resolution fMRI and electrophysiology of the rat primary somatosensory cortex

et al. 2013

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High-resolution functional-magnetic-resonance-imaging (fMRI) has been used to study brain functions at increasingly finer scale, but whether fMRI can accurately reflect layer-specific neuronal activities is less well understood. The present study investigated layer-specific cerebral-blood-volume (CBV) fMRI and electrophysiological responses in the rat cortex. CBV fMRI at 40×40 µm in-plane resolution was performed on an 11.7-T scanner. Electrophysiology used a 32-channel electrode array that spanned the entire cortical depth. Graded electrical stimulation was used to study activations in different cortical layers, exploiting the notion that most of the sensory-specific neurons are in layers II–V and most of the nociceptive-specific neurons are in layers V–VI. CBV response was strongest in layer IV of all stimulus amplitudes. Current source density analysis showed strong sink currents at cortical layers IV and VI. Multi-unit activities mainly appeared at layers IV–VI and peaked at layer V. Although our measures showed scaled activation profiles during modulation of stimulus amplitude and failed to detect specific recruitment at layers V and VI during noxious electrical stimuli, there appears to be discordance between CBV fMRI and electrophysiological peak responses, suggesting neurovascular uncoupling at laminar resolution. The technique implemented in the present study offers a means to investigate intracortical neurovascular function in the normal and diseased animal models at laminar resolution.

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High-Resolution 3D MR Microangiography of the Rat Ocular Circulation

Cited by 20 publications

References 18 publications

Decreased retinal–choroidal blood flow in retinitis pigmentosa as measured by MRI

Decreased retinal–choroidal blood flow in retinitis pigmentosa as measured by MRI

Quantitative Retinal and Choroidal Blood Flow During Light, Dark Adaptation and Flicker Light Stimulation in Rats Using Fluorescent Microspheres

Ultra high-resolution fMRI and electrophysiology of the rat primary somatosensory cortex

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