Hitoshi Fujii

Non-contact, two-dimensional measurement of tissue circulation in choroid and optic nerve head using laser speckle phenomenon

A new apparatus has been developed using the laser speckle phenomenon for non-contact, two-dimensional analysis of tissue circulation in the choroid and optic nerve head (ONH). The fundus was illuminated by a diode laser spot and its image speckle was detected by an image sensor. The difference between the average of the speckle intensity (Imean) and the speckle intensity for successive scannings was calculated, and the ratio of Imean to this difference was defined as normalized blur (NB), which is a quantitative index of blood velocity. The results were displayed on color graphic monitors showing the two-dimensional variation of the NB level in the measurement field. In the rabbit, this apparatus was used to study the relationship between the results of NB measurement and the choroidal blood flow determined by the microsphere technique, the relationship between NB obtained from the ONH tissue free of visible surface vessels and the ocular perfusion pressure (OPP) after a lethal injection of pentobarital, and the effect of intraocular pressure (IOP) on the NB in the choroid or in the ONH. A stepwise reduction in the OPP was introduced by elevating the IOP manometrically. The relative decrease in the average NB over the field measured, NBav, in the choroid with the reduction in OPP showed a significant correlation with the relative change in the blood flow rate determined using the microsphere technique (r = 0.60, P < 0.001). NBav in the ONH had a good correlation with the OPP after a lethal injection of pentobarbital (r = 0.98, P < 0.001). NBav in the choroid decreased with reduction in the OPP. Although NBav in the ONH was little affected by OPP change when OPP was above 40 mmHg, at OPP levels below 40 mmHg, NBav in the ONH decreased along with a reduction in the OPP. These results suggest that by using the present apparatus, the blood velocity in the choroid or ONH under various conditions can be studied non-invasively in the living eye.

Real-Time Measurement of Human Optic Nerve Head and Choroid Circulation, Using the Laser Speckle Phenomenon

A modification of a previously described instrument that used the laser speckle phenomenon for noncontact two-dimensional analysis of the fundus tissue circulation was devised so that tissue circulation in the optic nerve head (ONH) or choroid of the human eye could be measured on a real-time basis. The fundus was illuminated by a diode laser spot and the image speckle was recognized by an area sensor. A quantitative index of blood velocity, normalized blur (NB), was calculated by a logistic board every 0.125 seconds for 7 seconds. Using this modified device, the average NB of the measurement field in the temporal ONH, free of visible surface vessels (NBONH), and that in the posterior choroid (NBch) of normal human eyes were measured. The coefficients of reproducibility of 1-minute interval measurements were 11.7% for the NBONH) and 8.7% for the NBch (each, an average of 5 pulses), and those of 24-hour interval measurements were 13.0% (NBONH) and 9.7% (NBch). The pulsatile component average of NBONH was 38.4% of mean NBONH; of NBch, 26.6% of the mean NBch.

Real-time visualization of retinal microcirculation by laser flowgraphy

A new real-time measuring system is developed to visualize the blood flow map of the human retina using dynamic laser speckle effects and a hardware logic circuit. The retina is illuminated with a diode laser spot through a retinal camera, and the speckle field at the image plane of the spot is scanned by an area sensor. The output signal is analog-to-digital (AID) converted and the blur rate of the intensity at each pixel point is evaluated through a hardware logic circuit specially devel- oped for this system. The results are displayed in 2-D color maps suc- cessively at a rate of 16 frames/s, which allows the real-time observation of retinal blood flow.

Imaging of choroidal hemodynamics in eyes with polypoidal choroidal vasculopathy using laser speckle phenomenon

PurposeTo compare the images of choroidal vasculature obtained by laser speckle flowgraphy (LSFG) and indocyanine green angiography (IA), and to evaluate the imaging of choroidal hemodynamics in eyes with polypoidal choroidal vasculopathy (PCV) using LSFG.MethodsWe performed IA and wide-field LSFG, which measures the index of blood velocity (mean square blur rate; MBR) in 25 eyes with PCV. We constructed an MBR map of the sequential MBR images (600 × 280 pixels) from four or five pulsations during measurement (4.5 s). A grayscale composite map of a still image was obtained by averaging the cumulative sum of the MBR map. We compared the angiographic images of the grayscale composite map to IA results and evaluated the choroidal hemodynamics of 25 eyes with PCV in the MBR map.ResultsThe choroidal vasculature on the grayscale map had a resolution similar to the IA results. The grayscale map detected branching network vessels in 20 (80%) of the 25 eyes and polypoidal lesions in 11 (44%) eyes. The MBR map showed that the pulsations of the branching network vessels and polypoidal lesions were synchronized with the cardiac rhythm. The fluctuation rates of the PCV lesions during one pulsation ranged from 8.3% to 26.7% (mean, 13.6%) and from 7.3% to 24.6% (mean, 15.9%) for the intact choroid. The MBR map showed the watershed zone and highest signal intensity in the macula.ConclusionsUsing an MBR map, wide-field LSFG revealed the pulsating choroidal hemodynamics of the posterior fundus. A grayscale composite map showed the fine choroidal vasculature whose resolution was comparable to that of IA. The branching network vessels of PCV showed that pulsation was synchronized with the choroidal vessels. Wide-field LSFG showed the highest choroidal blood flow in the macular area and the presence of a watershed zone.

Real-Time Blood Velocity Measurements in Human Retinal Vein Using the Laser Speckle Phenomenon

PURPOSE To measure the in vivo blood velocity in human retinal veins using a laser speckle system. METHODS The system consists of a fundus camera, a diode laser, an image sensor, and a personal computer system. The fundus area, including a target retinal vein, is illuminated with a diode laser through a fundus camera and the laser speckle pattern is imaged onto the area sensor. From the time change of the contrast of the speckle pattern, the normalized blur (NB) value, a quantitative index of blood velocity, was calculated using a logic board. RESULTS In an in vitro experiment, the NB obtained from blood flow in 50-300 microm internal diameter glass capillary tubes, used as an analogue of a retinal vein, correlated with the diameter of the tube, the actual blood flow rate, and the background NB value, which was used as an analogue of choroidal circulation. In the in vivo experiment, the blood velocity in human retinal veins of approximately 50 microm in diameter was estimated in 16 normal human eyes using nomograms based on the result of the in vitro experiment. Velocity averaged 11.1+/-0.6 mm/s (mean +/- SD, n = 16) in retinal veins 53+/-6 microm in diameter. The coefficient of reproducibility of 5-minute interval measurements was 2.5+/-0.9%, and it took 63+/-15 seconds for one measurement. CONCLUSIONS The present methodology is clinically valid for measuring blood velocity in retinal veins.

Effects of the brown seaweed Undaria pinnatifida on erythematous inflammation assessed using digital photo analysis

The brown seaweed Undaria pinnatifida (Harvey) Suringar produced potent inhibition of erythematous inflammation assessed using digital photo analysis. The analysis technique was validated by laser speckle flowgraphy and blood vessel contraction. The methanol extract suppressed erythema by 50% when applied within 1 h before or 15 min after application of phorbol myristate acetate. Erythema reduction to half‐maximal values took 12 h with the extract, compared with 25 h with the vehicle. The blade part of the thallus showed the highest activity, while the northern type of U. pinnatifida had slightly higher activity than the southern type. The active constituents were stearidonic acid and eicosapentaenoic acid. These findings reinforce the claims of the health care industry and indigenous medicine that U. pinnatifida can be used as a health food and remedy for inflammation‐related symptoms. Copyright

Measurements of blood flow velocity in human retinal veins using laser speckle flowgraphy system

We measured the blood flow velocity in human retinal veins using a laser speckle flowgraphy system. This system consists of a fundus camera, a diode laser, an image sensor and a personal computer system. The fundus is illuminated with a diode laser through a fundus camera and the laser speckle pattern is imaged onto the area sensor. From the time change of contrast of speckle pattern, normalized blur (NB) value, a quantitative index of tissue blood velocity, was calculated by means of a logistic board, and two-dimensional distribution of NB in the measurement field was displayed in a color display. In the in vitro experiment, the NB obtained from the blood flow in a glass capillary tube was correlated with the diameter of the tube, background NB value and the blood flow rate actually measured. In the in vivo experiment, the blood velocity in human retinal veins of approximately 50 microns in diameter was estimated in 16 normal eyes using nomograms based on the results of the in vitro experiment. Velocity averaged 11.1 +/- 0.6 mm/ sec (mean +/- standard deviation, n = 16) in retinal veins of 53 +/- 6 microns in diameter and the reproducibility index of the in vivo measurements was 2.5 +/- 0.9%.

LSFG Findings of Proliferative Diabetic Retinopathy After Intravitreal Injection of Bevacizumab

The authors investigate the changes of chorioretinal blood flow using laser speckle flowgraphy (LSFG) in efficacy of treatment. Intravitreal bevacizumab was injected in a patient with proliferative diabetic retinopathy. LSFG measures the relative velocity index of erythrocytes (mean blur rate) in a previously confirmed area, with neovascularization elsewhere (NVE), neovascularization of the disc (NVD), and without neovascularization. The authors compared mean blur rate before and after bevacizumab injection in each area. In LSFG images, regression of blood flow was observed at the area of neovascularization sequentially as the change of color pattern. Finally, decrease of the mean blur rate of an average 32.7% was observed in the NVE area. Similarly, a reduction of 31.9% of mean blur rate was observed in the NVD area. However, in the area of without neovascularization, reduction of mean blur rate was not observed. This suggested the useful possibility of measuring chorioretinal blood flow changes by drug intervention using LSFG analysis.The authors investigate the changes of chorioretinal blood flow using laser speckle flowgraphy (LSFG) in efficacy of treatment. Intravitreal bevacizumab was injected in a patient with proliferative diabetic retinopathy. LSFG measures the relative velocity index of erythrocytes (mean blur rate) in a previously confirmed area, with neovascularization elsewhere (NVE), neovascularization of the disc (NVD), and without neovascularization. The authors compared mean blur rate before and after bevacizumab injection in each area. In LSFG images, regression of blood flow was observed at the area of neovascularization sequentially as the change of color pattern. Finally, decrease of the mean blur rate of an average 32.7% was observed in the NVE area. Similarly, a reduction of 31.9% of mean blur rate was observed in the NVD area. However, in the area of without neovascularization, reduction of mean blur rate was not observed. This suggested the useful possibility of measuring chorioretinal blood flow changes by drug intervention using LSFG analysis.

Functional imaging system for simultaneous measurement of blood volume and flow

Optical imaging derived from intrinsic signals such as blood volume and flow has enabled us to characterize the area of brain activation. Multi-spectral imaging of the change in cortical reflectance allows the determination of the change in the oxy-hemoglobin concentration independent of the deoxy-haemoglobin concentration. The changes in blood volume and oxygenation are closely related to the cerebral blood flow, and hence the simultaneous measurement of blood volume and flow in the cortical tissue must be beneficial for investigation of functional brain activation. Laser speckle flowgraphy has also been developed to visualize the blood flow in tissue and has been applied to measure the blood flow in tissue. In this study, a functional imaging system has been designed and assembled for the simultaneous measurement of the change in blood volume and flow in tissue. The optical systems of multi-spectral imaging and laser speckle flowgraphy are attached to the photo ports of the beam-splitter attachment of a stereo-microscope. The data of the multi-spectral image and speckle pattern of phantoms and finger are obtained for the initial experiments with the proposed system.

Optical imaging system for measurement of blood volume and flow in exposed brain cortex

The change in blood volume and flow in the cortical tissue of guinea pigs caused by brain activation during auditory stimulation is measured with a multispectral imaging system and a laser speckle flowgraphy system.