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Evaluation of optic nerve head blood flow in response to increase of intraocular pressure
摘要： The time course of the changes in the optic nerve head (ONH) blood flow in response to changes in the ocular perfusion pressure (OPP) induced by an artificial elevation of the intraocular pressure (IOP) has not been determined. We measured the blood flow, represented by the mean blur rate (MBR), on the ONH determined by laser speckle flowgraphy. The MBR was determined before, during, and after the IOP was elevated by 20 or 30 mmHg by pressure applied on the eye by an ophthalmodynamometer in a total of 27 healthy eyes. For an IOP elevation of 20 mmHg, the percentage reduction in the MBR-vessel was ?24.7%, and in the MBR-tissue was ?16.0% (P < 0.001). For an IOP elevation of 30 mmHg, the percentage reduction of the MBR-vessel was ?35.3% and the MBR-tissue was ?24.7% (P < 0.001). During the 30 mmHg IOP elevation for 10 minutes, both the MBR-vessel and MBR-tissue began returning to the baseline level from 1 minute after the beginning of the IOP elevation (P < 0.01, P < 0.05, respectively) and continued returning during the 10 minutes IOP elevation (P < 0.001, P < 0.01, respectively). We conclude that the ONH can autoregulate its blood flow in response to experimental changes in OPP induced by IOP elevations.
关键词： optic nerve head,autoregulation,laser speckle flowgraphy,blood flow,intraocular pressure
更新于2025-09-10 09:29:36
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Non-neuronal evoked and spontaneous hemodynamic changes in the anterior temporal region of the human head may lead to misinterpretations of functional near-infrared spectroscopy signals
摘要： Several functional near-infrared spectroscopy (fNIRS) studies report their findings based on changes of a single chromophore, usually concentration changes of oxygenated hemoglobin ([O2Hb]) or deoxygenated hemoglobin (HHb). However, influence of physiological actions may differ depending on which element is considered and the assumption that the chosen measure correlates with the neural response of interest might not hold. By assessing the correlation between [O2Hb] and [HHb] in task-evoked activity as well as resting-state data, we identified a spatial dependency of non-neuronal hemodynamic changes in the anterior temporal region of the human head. Our findings support the importance of reporting and discussing fNIRS outcomes obtained with both chromophores ([O2Hb] and [HHb]), in particular, for studies concerning the anterior temporal region of the human head. This practice should help to achieve a physiologically correct interpretation of the results when no measurements with short-distance channels are available while employing continuous-wave fNIRS systems.
关键词： superficial temporal vessels,temporal lobe,optical neuroimaging,temporalis muscle,scalp blood flow,extracerebral signal contamination,functional near-infrared spectroscopy
更新于2025-09-10 09:29:36
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Hemodynamic and neuronal responses to cocaine differ in awake versus anesthetized animals: Optical brain imaging study
摘要： Cocaine is a highly addictive drug with complex pharmacological effects. Most preclinical imaging studies investigating the effects of cocaine in the brain have been performed under anesthesia, which confounds findings. To tackle this problem, we used optical imaging to compare the effects of cocaine in the awake versus the anesthetized state. For this purpose, we customized an air floating mobile cage to fit the multi-wavelength spectral and laser speckle optical imaging system and implanted a multi-layer cranial window over the mouse somatosensory cortex. Results showed significant differences in neuronal activity and hemodynamics at baseline and in response to cocaine between the awake and the anesthetized state (isoflurane anesthesia). Specifically, 1) at baseline isoflurane dilated cerebral vessels, increased cerebral blood flow and depressed neuronal Ca2+ activity compared to the awake state; 2) acute cocaine (1 mg/kg iv) vasoconstricted blood vessels (arteries and veins) and decreased cerebral blood flow and oxygenated hemoglobin in the anesthetized state but not in the awake condition; 3) cocaine increased the accumulation of mean intracellular Ca2+ in neurons in the anesthetized state but not in the awake condition; and 4) in the awake state acute cocaine increased neuronal activities (increased the frequency of Ca2+ transients) and increased neuronal synchronization. We also corroborated that in the wake state cocaine also disrupted neurovascular coupling. These findings indicate that both vascular and neuronal responses to cocaine are influenced by isoflurane anesthesia, which highlights the importance of imaging awake animals when studying the effects of cocaine or other drugs in the brain.
关键词： oxygenated hemoglobin,Neuronal [Ca2+]i activity,Addiction,neurovascular coupling,GCaMP6f,cerebral blood flow,Neuronal synchronization,Vasoconstriction,Isoflurane
更新于2025-09-10 09:29:36
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Patient motion correction for dynamic cardiac PET: Current status and challenges
摘要： For dynamic cardiac PET of quantifying myocardial blood flow (MBF), patient motion is a major factor that affects the ROI definition and absolute quantification accuracy. In a recent study, an 82rubidium (82Rb)-dynamic-tailored motion-correction framework has been proposed to address the voluntary body motion for all the dynamic frames, including both early and late phases. This approach brings us one step closer to the practical and full motion correction for dynamic cardiac PET studies. In this editorial, we discussed the current status and limitations of motion-correction methods for dynamic cardiac PET, including the recent publication at JNC, and also pointed out the remaining challenges for future developments.
关键词： 82rubidium,dynamic cardiac PET,myocardial blood flow,motion-correction framework,patient motion correction
更新于2025-09-09 09:28:46
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Blood Flow in Monocular Retinoblastoma Assessed by Color Doppler and Correlations With High-Risk Pathologic Features
摘要： PURPOSE. To use color Doppler to analyze blood ?ow in the retrobulbar central retinal artery (CRA) and central retinal vein (CRV) in monocular retinoblastoma. METHODS. This prospective study included patients with group D and E retinoblastomas managed with only enucleation. Peak blood velocities were assessed in the CRA and CRV of tumor-containing eyes (CRAv and CRVv, respectively). The resistivity index in the CRA (RIa) and pulse index in the CRV (PIv) were calculated and related to optic nerve invasion (ONi), choroid invasion (mCHi), and tumor volume. RIa and PIv were also calculated for healthy eyes. RESULTS. In total, 25 patients with a mean age of 30.8-months old were included. The means (SD) for CRAv, CRVv, RIa, and PIv were 26.94 (12.32) cm/s, 16.2 (9.56) cm/s, 0.88 (0.12) and 0.79 (0.29), respectively. Tumor volume was signi?cantly correlated with CRAv (P ? 0.025) and RIa (P ? 0.032). ONi was present in 19 eyes and correlated with a smaller PIv (P < 0.001). A PIv less than 0.935 had a sensitivity of 89.5% and speci?city of 83.3% for predicting ONi. mCHi was not correlated with ?ow values. Healthy eyes had a signi?cantly lower RIa (P < 0.001) and lower PIv than eyes with (P ? 0.009) and without (P < 0.001) ONi. tumor volume was directly CONCLUSIONS. correlated with CRAv and RIa, and lower PIv was correlated with optic nerve invasion when a predictive cut-off value of less than 0.935 was applied. Comparisons with healthy eyes showed that tumor-containing eyes were associated with higher RIa and PIv values.
关键词： histopathology,eye enucleation,blood flow velocity,retinoblastoma,color doppler ultrasonography
更新于2025-09-09 09:28:46
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[ACM Press the 3rd International Conference - Seoul, Republic of Korea (2018.08.22-2018.08.24)] Proceedings of the 3rd International Conference on Biomedical Signal and Image Processing - ICBIP '18 - Correction of Aliasing in Color Doppler Echocardiography Based on Image Processing Technique in Echodynamography
摘要： A study about the program of color Doppler to improve blood velocity estimation has been developed. Color Doppler echocardiographic images were acquired using Philips IE33 have a crucial issue the ambiguity of the offset beams when the correct velocity of the blood flow exceeds the velocity of the Nyquist limit. Therefore, velocity dealiasing is needed in quality control of color Doppler echocardiographic data to correct velocities using EDG (echodynamography) based on observer and machine interaction. The program is applied to echocardiography images of aortic stenosis subject as a technique to assess cardiovascular function. One challenging with color Doppler is correcting velocity aliasing. The observer determines the ambiguity area based on his or her knowledge. These results confirm the dealiasing and noise removing are vital elements in improving blood velocity estimation in cardiovascular diagnostic. Therefore, this study could use clinical tools based on color Doppler imaging.
关键词： Color Doppler,Blood flow velocity,Aliasing,Dealiasing,Smoothing
更新于2025-09-09 09:28:46
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Retrobulbar blood flow changes in eyes with diabetic retinopathy a 10 year follow up study
摘要： Purpose: We sought to assess long-term changes in the flow parameters of retrobulbar vessels in diabetic patients. Methods: The retrobulbar circulation of 138 eyes was evaluated between 1994 and 1995 and 36 eyes were reevaluated between 2004 and 2008 (study group). They were divided into four groups: eyes of diabetic patients without diabetic retinopathy (DR), eyes with nonproliferative DR, eyes with proliferative DR, and eyes of nondiabetic patients (controls). Color Doppler imaging was used to assess the flow velocities in the major retrobulbar vessels. The resistive index (RI) was calculated and compared among the groups and between the two time periods. Results: RI values of the central retinal artery and posterior ciliary artery had increased in the two non-DR groups and in the nonproliferative DR group, with a surprising decrease measured in eyes with proliferative DR (P= nonsignificant [NS]). Combining the nonproliferative DR and proliferative DR groups resulted in a milder increase of the RI of the posterior ciliary artery (P= NS) and the central retinal artery (P=0.02) in the DR group compared to the other groups. Conclusion: Our results demonstrate that an increase of the resistance in the retrobulbar vessels, as a part of DR, can lessen over time and may even be reversed.
关键词： color Doppler imaging,retrobulbar blood flow,diabetic retinopathy
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Nara, Japan (2018.10.9-2018.10.12)] 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Blood Circulation Based on PPG Signals for Thermal Comfort Evaluation
摘要： This paper presents a new index for monitoring transition of blood circulation from Photoplethysmogram (PPG) signals for thermal comfort evaluation of users. Heat dissipation reaction through the dilation of blood vessels is person's intrinsic ability to control the thermal comfort. When body temperature is higher than normal temperature, blood circulation changes according to the dilation of blood vessels in distal end of the extremities. Blood circulation is often evaluated by an index of peripheral resistance corresponding to changes in blood flow velocity such as systolic/diastolic ratio (S/D) of flow velocities, resistance index and the pulsatility index. Unfortunately, such an index cannot be utilized in daily life for healthcare with using fitness trackers since the blood flow velocity is measured by either an ultrasonic Doppler blood flowmeter (UDF) or a Laser-Doppler flowmeter. Therefore, we propose a new index which is easily acquirable from PPG signals. First, a couple of variables correlating to the blood flow velocity is calculated from a rate of volumetric strain of Photoplethysmogram signals. Then the new index can be obtained as difference of these variables. Experimental results show the effectiveness of this index by confirming high correlation with S/D of UDF.
关键词： Peripheral blood circulation,volumetric strain,blood flow velocity,Photoplethysmogram signals
更新于2025-09-04 15:30:14
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Optoacoustic microscopy at multiple discrete frequencies
摘要： Optoacoustic (photoacoustic) sensing employs illumination of transient energy and is typically implemented in the time domain using nanosecond photon pulses. However, the generation of high-energy short photon pulses requires complex laser technology that imposes a low pulse repetition frequency (PRF) and limits the number of wavelengths that are concurrently available for spectral imaging. To avoid the limitations of working in the time domain, we have developed frequency-domain optoacoustic microscopy (FDOM), in which light intensity is modulated at multiple discrete frequencies. We integrated FDOM into a hybrid system with multiphoton microscopy, and we examine the relationship between image formation and modulation frequency, showcase high-fidelity images with increasing numbers of modulation frequencies from phantoms and in vivo, and identify a redundancy in optoacoustic measurements performed at multiple frequencies. We demonstrate that due to high repetition rates, FDOM achieves signal-to-noise ratios similar to those obtained by time-domain methods, using commonly available laser diodes. Moreover, we experimentally confirm various advantages of the frequency-domain implementation at discrete modulation frequencies, including concurrent illumination at two wavelengths that are carried out at different modulation frequencies as well as flow measurements in microfluidic chips and in vivo based on the optoacoustic Doppler effect. Furthermore, we discuss how FDOM redefines possibilities for optoacoustic imaging by capitalizing on the advantages of working in the frequency domain.
关键词： Doppler effect,Frequency-domain,Multiphoton microscopy,Optoacoustic microscopy,Microcirculatory blood flow
更新于2025-09-04 15:30:14
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Quantitative Analysis of Fundus-Image Sequences Reveals Phase of Spontaneous Venous Pulsations
摘要： Spontaneous venous pulsation correlates negatively with elevated intracranial pressure and papilledema, and it relates to glaucoma. Yet, its etiology remains unclear. A key element to elucidate its underlying mechanism is the time at which collapse occurs with respect to the heart cycle, but previous reports are contradictory. We assessed this question in healthy subjects using quantitative measurements of both vein diameters and artery lateral displacements; the latter being used as the marker of the ocular systole time.
关键词： retina,pulsation,intraocular pressure,blood flow,intracranial pressure,spontaneous venous pulsation
更新于2025-09-04 15:30:14