Retinal functional imager (RFI): Non-invasive functional imaging of the retina

Retinal functional imager (RFI) is a unique non-invasive functional imaging system with novel capabilities for visualizing the retina. The objective of this review was to show the utility of non-invasive functional imaging in various disorders. Electronic literature search was carried out using the websites www.pubmed.gov and www.google.com. The search words were retinal functional imager and non-invasive retinal imaging used in combination. The articles published or translated into English were studied. The RFI directly measures hemodynamic parameters such as retinal blood-flow velocity, oximetric state, metabolic responses to photic activation and generates capillary perfusion maps (CPM) that provides retinal vasculature detail similar to flourescein angiography. All of these parameters stand in a direct relationship to the function and therefore the health of the retina, and are known to be degraded in the course of retinal diseases. Detecting changes in retinal function aid early diagnosis and treatment as functional changes often precede structural changes in many retinal disorders. Nepal J Ophthalmol 2013; 5(10): 250-257 DOI: http://dx.doi.org/10.3126/nepjoph.v5i2.8738

Download Full-text

Automated segmentation and fractal analysis of high-resolution non-invasive capillary perfusion maps of the human retina

Microvascular Research ◽

10.1016/j.mvr.2013.06.008 ◽

2013 ◽

Vol 89 ◽

pp. 172-175 ◽

Cited By ~ 23

Author(s):

Hong Jiang ◽

Delia Cabrera DeBuc ◽

Tatjana Rundek ◽

Byron L. Lam ◽

Clinton B. Wright ◽

...

Keyword(s):

High Resolution ◽

Fractal Analysis ◽

Automated Segmentation ◽

Human Retina ◽

Capillary Perfusion ◽

Non Invasive ◽

Perfusion Maps

Download Full-text

Exploratory study of non-invasive, high-resolution functional macular imaging in subjects with diabetic retinopathy

International Journal of Ophthalmology ◽

10.18240/ijo.2021.01.08 ◽

2021 ◽

Vol 14 (1) ◽

pp. 57-63

Author(s):

Thalmon R Campagnoli ◽

◽

Jing Tian ◽

Delia Cabrera DeBuc ◽

William E. Smiddy ◽

...

Keyword(s):

Blood Flow ◽

Diabetic Retinopathy ◽

High Resolution ◽

Functional Imaging ◽

Case Series ◽

Diabetic Patients ◽

Capillary Perfusion ◽

Imaging Device ◽

Non Invasive ◽

Retinal Microvasculature

AIM: To evaluate a high-resolution functional imaging device that yields quantitative data regarding macular blood flow and capillary network features in eyes with diabetic retinopathy (DR). METHODS: Prospective, cross-sectional comparative case-series in which blood flow velocities (BFVs) and non-invasive capillary perfusion maps (nCPMs) in macular vessels were measured in patients with DR and in healthy controls using the Retinal Functional Imager (RFI) device. RESULTS: A total of 27 eyes of 21 subjects were studied [9 eyes nonproliferative diabetic retinopathy (NPDR), 9 eyes proliferative diabetic retinopathy (PDR) and 9 controls]. All diabetic patients were type 2. All patients with NPDR and 5 eyes with PDR also had diabetic macular edema (DME). The NPDR group included eyes with severe (n=3) and moderate NPDR (n=6), and were symptomatic. A significant decrease in venular BFVs was observed in the macular region of PDR eyes when compared to controls (2.61±0.6 mm/s and 2.92±0.72 mm/s in PDR and controls, respectively, P=0.019) as well as PDR eyes with DME compared to NPDR eyes (2.36±0.51 mm/s and 2.94±1.09 mm/s in PDR with DME and NPDR, respectively, P=0.01). CONCLUSION: The RFI, a non-invasive imaging tool, provides high-resolution functional imaging of the retinal microvasculature and quantitative measurement of BFVs in visually impaired DR patients. The isolated diminish venular BFVs in PDR eyes compared to healthy eyes and PDR eyes with DME in comparison to NPDR eyes may indicate the possibility of more retinal vein compromise than suspected in advanced DR.

Download Full-text

K+ Channels of Müller Glial Cells in Retinal Disorders

CNS & Neurological Disorders - Drug Targets ◽

10.2174/1871527317666180202114233 ◽

2018 ◽

Vol 17 (4) ◽

pp. 255-260 ◽

Cited By ~ 2

Author(s):

Feng Gao ◽

Lin-Jie Xu ◽

Yuan Zhao ◽

Xing-Huai Sun ◽

Zhongfeng Wang

Keyword(s):

Müller Cells ◽

Major Type ◽

Delayed Rectifier ◽

Muller Cells ◽

Bkca Channels ◽

K Channels ◽

Functional Changes ◽

Physiological Properties ◽

Retinal Disorders ◽

Inwardly Rectifying

Background & Objective: Müller cell is the major type of glial cell in the vertebrate retina. Müller cells express various types of K+ channels, such as inwardly rectifying K+ (Kir) channels, big conductance Ca2+-activated K+ (BKCa) channels, delayed rectifier K+ channels (KDR), and transient A-type K+ channels. These K+ channels play important roles in maintaining physiological functions of Müller cells. Under some retinal pathological conditions, the changed expression and functions of K+ channels may contribute to retinal pathogenesis. Conclusion: In this article, we reviewed the physiological properties of K+ channels in retinal Müller cells and the functional changes of these channels in retinal disorders.

Download Full-text

Partial aperture imaging system based on sparse point spread holograms and nonlinear cross-correlations

Scientific Reports ◽

10.1038/s41598-020-77912-3 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Angika Bulbul ◽

Joseph Rosen

Keyword(s):

Structural Changes ◽

Imaging System ◽

Current System ◽

Three Dimensional ◽

Phase Mask ◽

Coded Aperture ◽

Space Telescopes ◽

Reconstruction Process ◽

Cross Correlations ◽

Equivalent Systems

AbstractPartial aperture imaging system (PAIS) is a recently developed concept in which the traditional disc-shaped aperture is replaced by an aperture with a much smaller area and yet its imaging capabilities are comparable to the full aperture systems. Recently PAIS was demonstrated as an indirect incoherent digital three-dimensional imaging technique. Later it was successfully implemented in the study of the synthetic marginal aperture with revolving telescopes (SMART) to provide superresolution with subaperture area that was less than one percent of the area of the full synthetic disc-shaped aperture. In the study of SMART, the concept of PAIS was tested by placing eight coded phase reflectors along the boundary of the full synthetic aperture. In the current study, various improvements of PAIS are tested and its performance is compared with the other equivalent systems. Among the structural changes, we test ring-shaped eight coded phase subapertures with the same area as of the previous circular subapertures, distributed along the boundary of the full disc-shaped aperture. Another change in the current system is the use of coded phase mask with a point response of a sparse dot pattern. The third change is in the reconstruction process in which a nonlinear correlation with optimal parameters is implemented. With the improved image quality, the modified-PAIS can save weight and cost of imaging devices in general and of space telescopes in particular. Experimental results with reflective objects show that the concept of coded aperture extends the limits of classical imaging.

Download Full-text

Functional Imaging of Rel Expression in Inflammatory Processes Using Bioluminescence Imaging System in Transgenic Mice

PLoS ONE ◽

10.1371/journal.pone.0057632 ◽

2013 ◽

Vol 8 (2) ◽

pp. e57632 ◽

Cited By ~ 7

Author(s):

Xingyu Yang ◽

Hua Jing ◽

Kai Zhao ◽

Ruilin Sun ◽

Zhenze Liu ◽

...

Keyword(s):

Transgenic Mice ◽

Functional Imaging ◽

Bioluminescence Imaging ◽

Imaging System ◽

Inflammatory Processes

Download Full-text

Abstract P604: Astrocyte-dependent Regulation of Vascular Tone: Role in Hypertension

Hypertension ◽

10.1161/hyp.68.suppl_1.p604 ◽

2016 ◽

Vol 68 (suppl_1) ◽

Author(s):

Juan Manuel Ramiro-Diaz ◽

Ki Jung Kim ◽

Jessica A Filosa

Keyword(s):

Vascular Tone ◽

Structural Changes ◽

Neurovascular Unit ◽

Brain Slices ◽

Vascular Cognitive Impairment ◽

Vascular Density ◽

Aqp4 Expression ◽

Functional Changes ◽

Functional Studies ◽

Underlying Mechanisms

Clinical studies support that untreated hypertension (HT) accelerates the development of vascular cognitive impairment (VCI). Yet, the underlying mechanisms for VCI are not known. In a recent study we demonstrated the role of astrocytes in the regulation of parenchymal arteriole (PA) steady-state vascular tone. Here we hypothesized hypertension results in structural and functional changes to the neurovascular unit resulting in enhanced astrocytic TRPV4 channel-dependent Ca 2+ increases contributing to augmented pressure-induced PA constriction . Functional studies were conducted in brain slices from angiotensin II (AngII) treated mice (600 ng/Kg/min, 28 days). PA arterioles within brain slices were perfused and pressurized and myogenic-evoked diameter changes measured using video microscopy. In addition, using the GLAST-CreERT2 ; R26-lsl-GCaMP3 mice we measure myogenic-evoked Ca 2+ changes in perivascular astrocytes. We demonstrate that HT increases pressure-induced PA tone by 11.14% at 30 mmHg and 12.97% at 60 mmHg (10.88 to 22.02 and 15.46 to 28.43% of tone, P<0.05 and P<0.01, respectively). In ANG II-treated mice, PA myogenic-evoked responses significantly increased astrocytic Ca 2+ oscillations frequency (119.4%, 0.0366 to 0.0803 Hz, P<0.0001). A significant increase in astrocytic Ca 2+ oscillation frequency was also observed after 2 min of AngII (500 nM) bath application (44.8%, 0.0366 to 0.053 Hz, P<0.01) in brain slices from AngII treated mice. Furthermore, using the model of spontaneous hypertensive rat (SHR) we observed that HT differentially increases vascular density and the number of vascular pericytes in cortical layers with highest neuronal densities (L III-V). Finally, while aquaporin 4 (AQP4) expression pattern was not different in the gray matter of SHR compared with WKY rats, a significant increase in unpolarized AQP4 expression was observed in the white matter of SHR. Taken together, this evidence indicates that HT induces functional and structural changes to the neurovascular unit favoring the development of regional brain hypoperfusion likely contributing to the development of VCI.

Download Full-text

Hyperpolarized 129Xe Magnetic Resonance Spectroscopy in a Rat Model of Bronchopulmonary Dysplasia

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00612.2020 ◽

2021 ◽

Author(s):

Jordan David Fliss ◽

Brandon Zanette ◽

Yonni Friedlander ◽

Siddharth Sadanand ◽

Andras A Lindenmaier ◽

...

Keyword(s):

Magnetic Resonance ◽

Gas Exchange ◽

Magnetic Resonance Spectroscopy ◽

Bronchopulmonary Dysplasia ◽

Rat Model ◽

Resonance Spectroscopy ◽

Gas Exchange Parameters ◽

Functional Changes ◽

Non Invasive

Premature infants often require mechanical ventilation and oxygen therapy which can result in bronchopulmonary dysplasia (BPD), characterized by developmental arrest and impaired lung function. Conventional clinical methods for assessing the prenatal lung are not adequate for the detection and assessment of long-term health risks in infants with BPD, highlighting the need for a non-invasive tool for the characterization of lung microstructure and function. Theoretical diffusion models, like the Model of Xenon Exchange (MOXE), interrogate alveolar gas exchange by predicting the uptake of inert Hyperpolarized (HP) 129Xe gas measured with HP 129Xe magnetic resonance spectroscopy (MRS). To investigate HP 129Xe MRS as a tool for non-invasive characterization of pulmonary microstructural and functional changes in vivo, HP 129Xe gas exchange data were acquired in an oxygen exposure rat model of BPD that recapitulates the fewer and larger distal airways and pulmonary vascular stunting characteristics of BPD. Gas exchange parameters from MOXE, including airspace mean chord length (Lm), apparent hematocrit in the pulmonary capillaries (HCT), and pulmonary capillary transit time (tx), were compared with airspace mean axis length and area density (MAL and ρA) and percentage area of tissue and air (PTA and PAA) from histology. Lm was significantly larger in the exposed rats (p=0.003) and correlated with MAL, ρA, PTA, and PAA (0.59<|ρ|<0.66 and p<0.05). Observed increase in HCT (p=0.012) and changes in tx are also discussed. These findings support the use of HP 129Xe MRS for detecting fewer, enlarged distal airways in this rat model of BPD, and potentially in humans.

Download Full-text

Study of Osteocyte Behavior by High-Resolution Intravital Imaging Following Photo-Induced Ischemia

Molecules ◽

10.3390/molecules23112874 ◽

2018 ◽

Vol 23 (11) ◽

pp. 2874

Author(s):

Hengfeng Yuan ◽

Wen Jiang ◽

Yuanxin Chen ◽

Betty Kim

Keyword(s):

Imaging Techniques ◽

Avascular Osteonecrosis ◽

Functional Changes ◽

Cellular Processes ◽

Non Invasive ◽

Behavioral Dynamics ◽

Bony Anatomy ◽

Magnetic Resonance Imaging Mri

Ischemic injuries and local hypoxia can result in osteocytes dysfunction and play a key role in the pathogenesis of avascular osteonecrosis. Conventional imaging techniques including magnetic resonance imaging (MRI) and computed tomography (CT) can reveal structural and functional changes within bony anatomy; however, characterization of osteocyte behavioral dynamics in the setting of osteonecrosis at the single cell resolution is limited. Here, we demonstrate an optical approach to study real-time osteocyte functions in vivo. Using nicotinamide adenine dinucleotide (NADH) as a biomarker for metabolic dynamics in osteocytes, we showed that NADH level within osteocytes transiently increase significantly after local ischemia through non-invasive photo-induced thrombosis of afferent arterioles followed by a steady decline. Our study presents a non-invasive optical approach to study osteocyte behavior through the modulation of local environmental conditions. Thus it provides a powerful toolkit to study cellular processes involved in bone pathologies in vivo.

Download Full-text

Airway smooth muscle tone modulates mechanically induced cytoskeletal stiffening and remodeling

Journal of Applied Physiology ◽

10.1152/japplphysiol.00025.2005 ◽

2005 ◽

Vol 99 (2) ◽

pp. 634-641 ◽

Cited By ~ 32

Author(s):

Linhong Deng ◽

Nigel J. Fairbank ◽

Darren J. Cole ◽

Jeffrey J. Fredberg ◽

Geoffrey N. Maksym

Keyword(s):

Smooth Muscle ◽

Mechanical Stress ◽

Applied Stress ◽

Airway Smooth Muscle ◽

Cell Activation ◽

Structural Changes ◽

Muscle Tone ◽

Residual Effects ◽

Cell Stiffness ◽

Functional Changes

The application of mechanical stresses to the airway smooth muscle (ASM) cell causes time-dependent cytoskeletal stiffening and remodeling (Deng L, Fairbank NJ, Fabry B, Smith PG, and Maksym GN. Am J Physiol Cell Physiol 287: C440–C448, 2004). We investigated here the extent to which these behaviors are modulated by the state of cell activation (tone). Localized mechanical stress was applied to the ASM cell in culture via oscillating beads (4.5 μm) that were tightly bound to the actin cytoskeleton (CSK). Tone was reduced from baseline level using a panel of relaxant agonists (10−3 M dibutyryl cAMP, 10−4 M forskolin, or 10−6 M formoterol). To assess functional changes, we measured cell stiffness (G′) using optical magnetic twisting cytometry, and to assess structural changes of the CSK we measured actin accumulation in the neighborhood of the bead. Applied mechanical stress caused a twofold increase in G′ at 120 min. After cessation of applied stress, G′ diminished only 24 ± 6% (mean ± SE) at 1 h, leaving substantial residual effects that were largely irreversible. However, applied stress-induced stiffening could be prevented by ablation of tone. Ablation of tone also inhibited the amount of actin accumulation induced by applied mechanical stress ( P < 0.05). Thus the greater the contractile tone, the greater was applied stress-induced CSK stiffening and remodeling. As regards pathobiology of asthma, this suggests a maladaptive positive feedback in which tone potentiates ASM remodeling and stiffening that further increases stress and possibly leads to worsening airway function.

Download Full-text