1
|
Li L, Law C, Marrett S, Chai Y, Huber L, Jezzard P, Bandettini P. Quantification of cerebral blood volume changes caused by visual stimulation at 3 T using DANTE-prepared dual-echo EPI. Magn Reson Med 2021; 87:1846-1862. [PMID: 34817081 DOI: 10.1002/mrm.29099] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 10/07/2021] [Accepted: 11/05/2021] [Indexed: 11/12/2022]
Abstract
PURPOSE We investigate the influence of moving blood-attenuation effects when using "delay alternating with nutation for tailored excitation" (DANTE) pulses in conjunction with blood oxygen level dependent (BOLD) of functional MRI (fMRI) at 3 T. Based on the effects of including DANTE pulses, we propose quantification of cerebral blood volume (CBV) changes following functional stimulation. METHODS Eighteen volunteers in total underwent fMRI scans at 3 T. Seven volunteers were scanned to investigate the effects of DANTE pulses on the fMRI signal. CBV changes in response to visual stimulation were quantified in 11 volunteers using a DANTE-prepared dual-echo EPI sequence. RESULTS The inflow effects from flowing blood in arteries and draining vein effects from flowing blood in large veins can be suppressed by use of a DANTE preparation module. Using DANTE-prepared dual-echo EPI, we quantitatively measured intravascular-weighted microvascular CBV changes of 25.4%, 29.8%, and 32.6% evoked by 1, 5, and 10 Hz visual stimulation, respectively. The extravascular fraction (∆S/S)extra at TE = 30 ms in total BOLD signal was determined to be 64.8 ± 3.4%, which is in line with previous extravascular component estimation at 3 T. Results show that the microvascular CBV changes are linearly dependent on total BOLD changes at TE = 30 ms with a slope of 0.113, and this relation is independent of stimulation frequency and subject. CONCLUSION The DANTE preparation pulses can be incorporated into a standard EPI fMRI sequence for the purpose of minimizing inflow effects and reducing draining veins effects in large vessels. Additionally, the DANTE-prepared dual-echo EPI sequence is a promising fast imaging tool for quantification of intravascular-weighted CBV change in the microvascular space at 3 T.
Collapse
Affiliation(s)
- Linqing Li
- National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA
| | - Christine Law
- Systems Neuroscience and Pain Lab, Stanford University, Stanford, California, USA
| | - Sean Marrett
- National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA
| | - Yuhui Chai
- National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA
| | - Laurentius Huber
- MR-Methods Group, MBIC, FPN, Maastricht University, Maastricht, Netherlands
| | - Peter Jezzard
- Wellcome Centre for Integrative Neuroimaging, FMRIB Division, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Peter Bandettini
- National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA
| |
Collapse
|
2
|
Reiter DA, Adelnia F, Cameron D, Spencer RG, Ferrucci L. Parsimonious modeling of skeletal muscle perfusion: Connecting the stretched exponential and fractional Fickian diffusion. Magn Reson Med 2021; 86:1045-1057. [PMID: 33724547 DOI: 10.1002/mrm.28766] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 02/12/2021] [Accepted: 02/14/2021] [Indexed: 12/30/2022]
Abstract
PURPOSE To develop an anomalous (non-Gaussian) diffusion model for characterizing skeletal muscle perfusion using multi-b-value DWI. THEORY AND METHODS Fick's first law was extended for describing tissue perfusion as anomalous superdiffusion, which is non-Gaussian diffusion exhibiting greater particle spread than that of the Gaussian case. This was accomplished using a space-fractional derivative that gives rise to a power-law relationship between mean squared displacement and time, and produces a stretched exponential signal decay as a function of b-value. Numerical simulations were used to estimate parameter errors under in vivo conditions, and examine the effect of limited SNR and residual fat signal. Stretched exponential DWI parameters, α and D , were measured in thigh muscles of 4 healthy volunteers at rest and following in-magnet exercise. These parameters were related to a stable distribution of jump-length probabilities and used to estimate microvascular volume fractions. RESULTS Numerical simulations showed low dispersion in parameter estimates within 1.5% and 1%, and bias errors within 3% and 10%, for α and D , respectively. Superdiffusion was observed in resting muscle, and to a greater degree following exercise. Resting microvascular volume fraction was between 0.0067 and 0.0139 and increased between 2.2-fold and 4.7-fold following exercise. CONCLUSIONS This model captures superdiffusive molecular motions consistent with perfusion, using a parsimonious representation of the DWI signal, providing approximations of microvascular volume fraction comparable with histological estimates. This signal model demonstrates low parameter-estimation errors, and therefore holds potential for a wide range of applications in skeletal muscle and elsewhere in the body.
Collapse
Affiliation(s)
- David A Reiter
- Department of Radiology & Imaging Sciences, Emory University, Atlanta, Georgia, USA.,Department of Orthopedics, Emory University, Atlanta, Georgia, USA
| | - Fatemeh Adelnia
- Vanderbilt University Institute of Imaging Sciences, Vanderbilt University, Medical center, Nashville, Tennessee, USA
| | - Donnie Cameron
- Norwich Medical School, University of East Anglia, Norwich, United Kingdom.,C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden Medical Center, Leiden, the Netherlands
| | - Richard G Spencer
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
| | - Luigi Ferrucci
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
| |
Collapse
|
3
|
Bladt P, van Osch MJP, Clement P, Achten E, Sijbers J, den Dekker AJ. Supporting measurements or more averages? How to quantify cerebral blood flow most reliably in 5 minutes by arterial spin labeling. Magn Reson Med 2020; 84:2523-2536. [PMID: 32424947 PMCID: PMC7402018 DOI: 10.1002/mrm.28314] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/19/2020] [Accepted: 04/17/2020] [Indexed: 11/29/2022]
Abstract
Purpose To determine whether sacrificing part of the scan time of pseudo‐continuous arterial spin labeling (PCASL) for measurement of the labeling efficiency and blood
T1 is beneficial in terms of CBF quantification reliability. Methods In a simulation framework, 5‐minute scan protocols with different scan time divisions between PCASL data acquisition and supporting measurements were evaluated in terms of CBF estimation variability across both noise and ground truth parameter realizations taken from the general population distribution. The entire simulation experiment was repeated for a single‐post‐labeling delay (PLD), multi‐PLD, and free‐lunch time‐encoded (te‐FL) PCASL acquisition strategy. Furthermore, a real data study was designed for preliminary validation. Results For the considered population statistics, measuring the labeling efficiency and the blood
T1 proved beneficial in terms of CBF estimation variability for any distribution of the 5‐minute scan time compared to only acquiring ASL data. Compared to single‐PLD PCASL without support measurements as recommended in the consensus statement, a 26%, 33%, and 42% reduction in relative CBF estimation variability was found for optimal combinations of supporting measurements with single‐PLD, free‐lunch, and multi‐PLD PCASL data acquisition, respectively. The benefit of taking the individual variation of blood
T1 into account was also demonstrated in the real data experiment. Conclusions Spending time to measure the labeling efficiency and the blood
T1 instead of acquiring more averages of the PCASL data proves to be advisable for robust CBF quantification in the general population.
Collapse
Affiliation(s)
- Piet Bladt
- imec - Vision Lab, Department of Physics, University of Antwerp, Antwerp, Belgium
| | - Matthias J P van Osch
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Institute of Brain and Cognition, Leiden University, Leiden, The Netherlands
| | - Patricia Clement
- Department of Radiology and Nuclear Medicine, Ghent University, Ghent, Belgium
| | - Eric Achten
- Department of Radiology and Nuclear Medicine, Ghent University, Ghent, Belgium
| | - Jan Sijbers
- imec - Vision Lab, Department of Physics, University of Antwerp, Antwerp, Belgium
| | - Arnold J den Dekker
- imec - Vision Lab, Department of Physics, University of Antwerp, Antwerp, Belgium
| |
Collapse
|
4
|
DeStefano JG, Jamieson JJ, Linville RM, Searson PC. Benchmarking in vitro tissue-engineered blood-brain barrier models. Fluids Barriers CNS 2018; 15:32. [PMID: 30514389 PMCID: PMC6280508 DOI: 10.1186/s12987-018-0117-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 11/11/2018] [Indexed: 12/13/2022] Open
Abstract
The blood–brain barrier (BBB) plays a key role in regulating transport into and out of the brain. With increasing interest in the role of the BBB in health and disease, there have been significant advances in the development of in vitro models. The value of these models to the research community is critically dependent on recapitulating characteristics of the BBB in humans or animal models. However, benchmarking in vitro models is surprisingly difficult since much of our knowledge of the structure and function of the BBB comes from in vitro studies. Here we describe a set of parameters that we consider a starting point for benchmarking and validation. These parameters are associated with structure (ultrastructure, wall shear stress, geometry), microenvironment (basement membrane and extracellular matrix), barrier function (transendothelial electrical resistance, permeability, efflux transport), cell function (expression of BBB markers, turnover), and co-culture with other cell types (astrocytes and pericytes). In suggesting benchmarks, we rely primarily on imaging or direct measurements in humans and animal models.
Collapse
Affiliation(s)
- Jackson G DeStefano
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD, USA.,Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - John J Jamieson
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD, USA.,Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Raleigh M Linville
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD, USA.,Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Peter C Searson
- Institute for Nanobiotechnology, Johns Hopkins University, Baltimore, MD, USA. .,Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, USA. .,120 Croft Hall, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA.
| |
Collapse
|
5
|
Fournet G, Li JR, Cerjanic AM, Sutton BP, Ciobanu L, Le Bihan D. A two-pool model to describe the IVIM cerebral perfusion. J Cereb Blood Flow Metab 2017; 37:2987-3000. [PMID: 27903921 PMCID: PMC5536805 DOI: 10.1177/0271678x16681310] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
IntraVoxel Incoherent Motion (IVIM) is a magnetic resonance imaging (MRI) technique capable of measuring perfusion-related parameters. In this manuscript, we show that the mono-exponential model commonly used to process IVIM data might be challenged, especially at short diffusion times. Eleven rat datasets were acquired at 7T using a diffusion-weighted pulsed gradient spin echo sequence with b-values ranging from 7 to 2500 s/mm2 at three diffusion times. The IVIM signals, obtained by removing the diffusion component from the raw MR signal, were fitted to the standard mono-exponential model, a bi-exponential model and the Kennan model. The Akaike information criterion used to find the best model to fit the data demonstrates that, at short diffusion times, the bi-exponential IVIM model is most appropriate. The results obtained by comparing the experimental data to a dictionary of numerical simulations of the IVIM signal in microvascular networks support the hypothesis that such a bi-exponential behavior can be explained by considering the contribution of two vascular pools: capillaries and somewhat larger vessels.
Collapse
Affiliation(s)
- Gabrielle Fournet
- 1 NeuroSpin, CEA Saclay-Center, Gif-sur-Yvette, France.,2 INRIA Saclay, Palaiseau, France
| | | | - Alex M Cerjanic
- 3 Bioengineering Department, Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Bradley P Sutton
- 3 Bioengineering Department, Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Luisa Ciobanu
- 1 NeuroSpin, CEA Saclay-Center, Gif-sur-Yvette, France
| | | |
Collapse
|
6
|
Schmid F, Tsai PS, Kleinfeld D, Jenny P, Weber B. Depth-dependent flow and pressure characteristics in cortical microvascular networks. PLoS Comput Biol 2017; 13:e1005392. [PMID: 28196095 PMCID: PMC5347440 DOI: 10.1371/journal.pcbi.1005392] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 03/01/2017] [Accepted: 01/31/2017] [Indexed: 01/21/2023] Open
Abstract
A better knowledge of the flow and pressure distribution in realistic microvascular networks is needed for improving our understanding of neurovascular coupling mechanisms and the related measurement techniques. Here, numerical simulations with discrete tracking of red blood cells (RBCs) are performed in three realistic microvascular networks from the mouse cerebral cortex. Our analysis is based on trajectories of individual RBCs and focuses on layer-specific flow phenomena until a cortical depth of 1 mm. The individual RBC trajectories reveal that in the capillary bed RBCs preferentially move in plane. Hence, the capillary flow field shows laminar patterns and a layer-specific analysis is valid. We demonstrate that for RBCs entering the capillary bed close to the cortical surface (< 400 μm) the largest pressure drop takes place in the capillaries (37%), while for deeper regions arterioles are responsible for 61% of the total pressure drop. Further flow characteristics, such as capillary transit time or RBC velocity, also vary significantly over cortical depth. Comparison of purely topological characteristics with flow-based ones shows that a combined interpretation of topology and flow is indispensable. Our results provide evidence that it is crucial to consider layer-specific differences for all investigations related to the flow and pressure distribution in the cortical vasculature. These findings support the hypothesis that for an efficient oxygen up-regulation at least two regulation mechanisms must be playing hand in hand, namely cerebral blood flow increase and microvascular flow homogenization. However, the contribution of both regulation mechanisms to oxygen up-regulation likely varies over depth. The brain consumes approximately 20% of the total oxygen used by the human body. An efficient and robust energy supply is essential for the brain’s functioning. The brain is able to up-regulate its oxygen supply in the proximity of neuronal activation. However, the details of the underlying vascular regulation mechanisms remain unknown. To improve the understanding of the blood flow patterns in the cortex we perform numerical simulations in realistic microvascular networks. In contrast to experimental measurements, numerical computations offer the advantage that the whole pressure and flow field is available for analysis. It is well established that the cerebral cortex is organized in laminar fashion and indeed our results reveal that the flow field in the capillary bed shows significant layer-specific differences. Those differences must be taken into account in future numerical and experimental works. Furthermore, it seems likely that multiple regulation mechanisms are playing hand in hand and that their impact differs over depth.
Collapse
Affiliation(s)
- Franca Schmid
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland
- * E-mail:
| | - Philbert S. Tsai
- Department of Physics, University of California at San Diego, La Jolla, California, United States of America
| | - David Kleinfeld
- Department of Physics, University of California at San Diego, La Jolla, California, United States of America
- Section of Neurobiology, University of California, La Jolla, California, United States of America
| | - Patrick Jenny
- Institute of Fluid Dynamics, ETH Zurich, Zurich, Switzerland
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| |
Collapse
|
7
|
Gould IG, Tsai P, Kleinfeld D, Linninger A. The capillary bed offers the largest hemodynamic resistance to the cortical blood supply. J Cereb Blood Flow Metab 2017; 37:52-68. [PMID: 27780904 PMCID: PMC5363755 DOI: 10.1177/0271678x16671146] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 06/15/2016] [Accepted: 07/30/2016] [Indexed: 01/09/2023]
Abstract
The cortical angioarchitecture is a key factor in controlling cerebral blood flow and oxygen metabolism. Difficulties in imaging the complex microanatomy of the cortex have so far restricted insight about blood flow distribution in the microcirculation. A new methodology combining advanced microscopy data with large scale hemodynamic simulations enabled us to quantify the effect of the angioarchitecture on the cerebral microcirculation. High-resolution images of the mouse primary somatosensory cortex were input into with a comprehensive computational model of cerebral perfusion and oxygen supply ranging from the pial vessels to individual brain cells. Simulations of blood flow, hematocrit and oxygen tension show that the wide variation of hemodynamic states in the tortuous, randomly organized capillary bed is responsible for relatively uniform cortical tissue perfusion and oxygenation. Computational analysis of microcirculatory blood flow and pressure drops further indicates that the capillary bed, including capillaries adjacent to feeding arterioles (d < 10 µm), are the largest contributors to hydraulic resistance.
Collapse
Affiliation(s)
- Ian Gopal Gould
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Philbert Tsai
- Department of Physics, University of California at San Diego, San Diego, CA, USA
| | - David Kleinfeld
- Department of Physics, University of California at San Diego, San Diego, CA, USA
| | - Andreas Linninger
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| |
Collapse
|
8
|
Jernigan SR, Osborne JA, Mirek CJ, Buckner G. Selective internal radiation therapy: quantifying distal penetration and distribution of resin and glass microspheres in a surrogate arterial model. J Vasc Interv Radiol 2015; 26:897-904.e2. [PMID: 25891507 DOI: 10.1016/j.jvir.2015.02.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 02/16/2015] [Accepted: 02/20/2015] [Indexed: 01/10/2023] Open
Abstract
PURPOSE To experimentally investigate the effects of microsphere density and diameter on distal penetration. MATERIALS AND METHODS A surrogate hepatic arterial system was developed to replicate the hemodynamics (pressures, flow rates, pulsatile flow characteristics) and anatomic geometry (vessel diameters) proximal and distal to the microsphere injection point. A planar tumor model, placed distal to the injection point, allowed visualization of deposited microspheres. Bland resin and glass microspheres, with physical characteristics approximating the characteristics of commercially available products, were injected into the surrogate system. Microsphere type, injection rate, systemic flow rate, and tumor model inclination were varied among tests (glass, n = 7; resin, n = 6) with replicates for 2 conditions. After injection, 254 micrographs were obtained at previously defined locations throughout the tumor model to document microsphere distributions. Average microsphere distributions and mass measurements of microspheres collected at the tumor outlet were analyzed to quantify distal penetration for each case. RESULTS Across all test conditions, average penetration depths of resin microspheres were higher compared with glass microspheres (45.1 cm ± 11.8 vs 22.3 cm ± 9.9). The analysis of variance indicated that the observed difference between microsphere type (glass vs resin) was significant (P = .005, df = 1,2). The observed distance means did not differ significantly across flow rate or inclination angle. CONCLUSIONS Penetration depths of resin microspheres were significantly higher than penetration depths of glass microspheres in the surrogate hepatic arterial system.
Collapse
Affiliation(s)
- Shaphan R Jernigan
- Departments of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh NC 27695
| | - Jason A Osborne
- Statistics, North Carolina State University, Campus Box 7910, Raleigh NC 27695
| | - Christopher J Mirek
- Biomedical Engineering, North Carolina State University, Campus Box 7910, Raleigh NC 27695
| | - Gregory Buckner
- Departments of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh NC 27695.; Biomedical Engineering, North Carolina State University, Campus Box 7910, Raleigh NC 27695..
| |
Collapse
|
9
|
Fontanella AN, Schroeder T, Hochman DW, Chen RE, Hanna G, Haglund MM, Rajaram N, Frees AE, Secomb TW, Palmer GM, Dewhirst MW. Quantitative mapping of hemodynamics in the lung, brain, and dorsal window chamber-grown tumors using a novel, automated algorithm. Microcirculation 2014; 20:724-35. [PMID: 23781901 DOI: 10.1111/micc.12072] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 06/14/2013] [Indexed: 12/01/2022]
Abstract
OBJECTIVE Hemodynamic properties of vascular beds are of great interest in a variety of clinical and laboratory settings. However, there presently exists no automated, accurate, technically simple method for generating blood velocity maps of complex microvessel networks. METHODS Here, we present a novel algorithm that addresses the problem of acquiring quantitative maps by applying pixel-by-pixel cross-correlation to video data. Temporal signals at every spatial coordinate are compared with signals at neighboring points, generating a series of correlation maps from which speed and direction are calculated. User-assisted definition of vessel geometries is not required, and sequential data are analyzed automatically, without user bias. RESULTS Velocity measurements were validated against the dual-slit method and against in vitro capillary flow with known velocities. The algorithm was tested in three different biological models in order to demonstrate its versatility. CONCLUSIONS The hemodynamic maps presented here demonstrate an accurate, quantitative method of analyzing dynamic vascular systems.
Collapse
Affiliation(s)
- Andrew N Fontanella
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Li H, Liu Q, Lu H, Li Y, Zhang HF, Tong S. Directly measuring absolute flow speed by frequency-domain laser speckle imaging. OPTICS EXPRESS 2014; 22:21079-21087. [PMID: 25321308 DOI: 10.1364/oe.22.021079] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Laser speckle contrast imaging (LSCI) is a simple yet powerful tool to image blood flow. However, traditional LSCI has limited quantitative analysis capabilities due to various factors affecting flow speed evaluation, including illumination intensity, scattering from static tissues, and mathematical complexity of blood flow estimation. Here, we present a frequency-domain laser speckle imaging (FDLSI) method that can directly measure absolute flow speed. In phantom experiments, the measured flow speed agreed well with the preset actual values (10% deviation). Furthermore, in vivo experiments demonstrated that FDLSI was minimally affected by illumination condition changes.
Collapse
|
11
|
Yin B, Kuranov RV, McElroy AB, Kazmi S, Dunn AK, Duong TQ, Milner TE. Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation. JOURNAL OF BIOMEDICAL OPTICS 2013; 18:56005. [PMID: 23640076 PMCID: PMC3642243 DOI: 10.1117/1.jbo.18.5.056005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A swept-source dual-wavelength photothermal (DWP) optical coherence tomography (OCT) system is demonstrated for quantitative imaging of microvasculature oxygen saturation. DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitation. A 1,064-nm OCT probe and 770-nm and 800-nm photothermal excitation beams are combined in a single-mode optical fiber to measure microvasculature hemoglobin oxygen saturation (SO(2)) levels in phantom blood vessels with a range of blood flow speeds (0 to 17 mm/s). A 50-μm-diameter blood vessel phantom is imaged, and SO(2) levels are measured using DWP-OCT and compared with values provided by a commercial oximeter at various blood oxygen concentrations. The influences of blood flow speed and mechanisms of SNR phase degradation on the accuracy of SO(2) measurement are identified and investigated.
Collapse
Affiliation(s)
- Biwei Yin
- University of Texas at Austin, Departments of Electrical and Computer Engineering, 1 University Station C0803, Austin, Texas 78712
| | - Roman V. Kuranov
- University of Texas Health Science Center at San Antonio, Department of Ophthalmology, 7703 Floyd Curl Drive, San Antonio, Texas 78229
- Address all correspondence to: Roman V. Kuranov, University of Texas Health Science Center at San Antonio, Department of Ophthalmology, 7703 Floyd Curl Drive, San Antonio, Texas 78229. Tel: 210-567-8402; Fax: 210-567-8413; E-mail:
| | - Austin B. McElroy
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| | - Shams Kazmi
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| | - Andrew K. Dunn
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| | - Timothy Q. Duong
- University of Texas Health Science Center at San Antonio, Department of Ophthalmology, 7703 Floyd Curl Drive, San Antonio, Texas 78229
| | - Thomas E. Milner
- University of Texas at Austin, Department of Biomedical Engineering, 1 University Station C0800, Austin, Texas 78712
| |
Collapse
|
12
|
Kuranov RV, Kazmi S, McElroy AB, Kiel JW, Dunn AK, Milner TE, Duong TQ. In vivo depth-resolved oxygen saturation by Dual-Wavelength Photothermal (DWP) OCT. OPTICS EXPRESS 2011; 19:23831-44. [PMID: 22109408 PMCID: PMC3482904 DOI: 10.1364/oe.19.023831] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Microvasculature hemoglobin oxygen saturation (SaO2) is important in the progression of various pathologies. Non-invasive depth-resolved measurement of SaO2 levels in tissue microvasculature has the potential to provide early biomarkers and a better understanding of the pathophysiological processes allowing improved diagnostics and prediction of disease progression. We report proof-of-concept in vivo depth-resolved measurement of SaO(2) levels in selected 30 µm diameter arterioles in the murine brain using Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) with 800 nm and 770 nm photothermal excitation wavelengths. Depth location of back-reflected light from a target arteriole was confirmed using Doppler and speckle contrast OCT images. SaO(2) measured in a murine arteriole with DWP-OCT is linearly correlated (R(2)=0.98) with systemic SaO(2) values recorded by a pulse-oximeter. DWP-OCT are steadily lower (10.1%) than systemic SaO(2) values except during pure oxygen breathing. DWP-OCT is insensitive to OCT intensity variations and is a candidate approach for in vivo depth-resolved quantitative imaging of microvascular SaO(2) levels.
Collapse
Affiliation(s)
- Roman V Kuranov
- Department of Ophthalmology, The University of Texas Health Science Center, San Antonio, Texas 78229, USA.
| | | | | | | | | | | | | |
Collapse
|
13
|
Autio J, Kawaguchi H, Saito S, Aoki I, Obata T, Masamoto K, Kanno I. Spatial frequency-based analysis of mean red blood cell speed in single microvessels: investigation of microvascular perfusion in rat cerebral cortex. PLoS One 2011; 6:e24056. [PMID: 21887370 PMCID: PMC3161111 DOI: 10.1371/journal.pone.0024056] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 08/03/2011] [Indexed: 02/04/2023] Open
Abstract
Background Our previous study has shown that prenatal exposure to X-ray irradiation causes cerebral hypo-perfusion during the postnatal development of central nervous system (CNS). However, the source of the hypo-perfusion and its impact on the CNS development remains unclear. The present study developed an automatic analysis method to determine the mean red blood cell (RBC) speed through single microvessels imaged with two-photon microscopy in the cerebral cortex of rats prenatally exposed to X-ray irradiation (1.5 Gy). Methodology/Principal Findings We obtained a mean RBC speed (0.9±0.6 mm/sec) that ranged from 0.2 to 4.4 mm/sec from 121 vessels in the radiation-exposed rats, which was about 40% lower than that of normal rats that were not exposed. These results were then compared with the conventional method for monitoring microvascular perfusion using the arteriovenous transit time (AVTT) determined by tracking fluorescent markers. A significant increase in the AVTT was observed in the exposed rats (1.9±0.6 sec) as compared to the age-matched non-exposed rats (1.2±0.3 sec). The results indicate that parenchyma capillary blood velocity in the exposed rats was approximately 37% lower than in non-exposed rats. Conclusions/Significance The algorithm presented is simple and robust relative to monitoring individual RBC speeds, which is superior in terms of noise tolerance and computation time. The demonstrative results show that the method developed in this study for determining the mean RBC speed in the spatial frequency domain was consistent with the conventional transit time method.
Collapse
Affiliation(s)
- Joonas Autio
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
| | - Hiroshi Kawaguchi
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
| | - Shigeyoshi Saito
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
| | - Ichio Aoki
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
| | - Takayuki Obata
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
| | - Kazuto Masamoto
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
- Center for Frontier Science and Engineering, University of Electro-Communications, Chofu, Tokyo, Japan
| | - Iwao Kanno
- Department of Biophysics, Molecular Imaging Center, National Institute of Radiological Sciences, Anagawa, Chiba, Japan
- * E-mail:
| |
Collapse
|
14
|
|
15
|
Schwarzmaier SM, Kim SW, Trabold R, Plesnila N. Temporal profile of thrombogenesis in the cerebral microcirculation after traumatic brain injury in mice. J Neurotrauma 2010; 27:121-30. [PMID: 19803784 DOI: 10.1089/neu.2009.1114] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Traumatic brain injury (TBI) is associated with an almost immediate reduction in cerebral blood flow (CBF). Because cerebral perfusion pressure is often normal under these circumstances it was hypothesized that the reduction of post-traumatic CBF has to occur at the level of the microcirculation. The aim of the current study was to investigate whether cerebral microvessels are involved in the development of blood flow disturbances following experimental TBI. C57/BL6 mice (n = 12) were intubated and ventilated under control of end-tidal Pco(2) ((ET)P(CO2)). After preparation of a cranial window and baseline recordings, the animals were subjected to experimental TBI by controlled cortical impact (CCI; 6 m/sec, 0.5 mm). Vessel lumina and intravascular cells were visualized by in vivo fluorescence microscopy (IVM) using the fluorescent dyes FITC-dextran and rhodamine 6G, respectively. Vessel diameter, cell-endothelial interactions, and thrombus formation were quantified within the traumatic penumbra by IVM up to 2 h after CCI. Arteriolar diameters increased after CCI by 26.2 +/- 2.5% (mean +/- SEM, p < 0.01 versus baseline), and remained at this level until the end of the observation period. Rolling of leukocytes on the cerebrovascular endothelium was observed both in arterioles and venules, while leukocyte-platelet aggregates were found only in venules. Microthrombi occluded up to 70% of venules and 33% of arterioles. The current data suggest that the immediate post-traumatic decrease in peri-contusional blood flow is not caused by arteriolar vasoconstriction, but by platelet activation and the subsequent formation of thrombi in the cerebral microcirculation.
Collapse
Affiliation(s)
- Susanne M Schwarzmaier
- Institute for Surgical Research in the Walter Brendel Center for Experimental Medicine, Department of Neurosurgery, University of Munich Medical Center-Grosshadern, Ludwig-Maximilians University, Munich, Germany
| | | | | | | |
Collapse
|
16
|
Unekawa M, Tomita M, Tomita Y, Toriumi H, Miyaki K, Suzuki N. RBC velocities in single capillaries of mouse and rat brains are the same, despite 10-fold difference in body size. Brain Res 2010; 1320:69-73. [PMID: 20085754 DOI: 10.1016/j.brainres.2010.01.032] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 12/24/2009] [Accepted: 01/12/2010] [Indexed: 11/15/2022]
Abstract
Employing high-speed camera laser-scanning confocal microscopy with RBC-tracking software, we previously showed that RBC velocities in intraparenchymal capillaries of rat cerebral cortex are distributed over a wide range. In the present work, we measured RBC velocities in mice, whose body weights are less than one-tenth of that of rats. In an isoflurane-anesthetized mouse, a cranial window was opened in the left temporo-parietal region. Intravenously administered FITC-labeled RBCs were automatically recognized and tracked frame-by-frame at 500fps, and the velocities of all RBCs recognized were calculated with our Matlab-domain software, KEIO-IS2. Among 15241 RBCs detected in the ROI in 21 mice, 1655 were identified as flowing in capillaries. The velocities of these RBCs ranged from 0.15 to 8.6mm/s, with a mean of 2.03+/-1.42mm/s. A frequency distribution plot showed that RBC velocities were clustered at around 1.0mm/s, tailing up to 8.6mm/s, and 59% of the RBCs in capillaries showed velocities within the range of 0.5 to 2.0mm/s. Unexpectedly, these characteristics of RBC velocities in mice were very similar to those of rats, despite differences in RBC diameter (6.0 vs. 6.5microm), body size (25 vs. 327g), heart rate (461 vs. 319bpm) and arterial blood pressure (86 vs. 84mmHg). We speculate that physical factors relating to oxygen exchange may constrain general RBC velocity in capillaries to a certain range for optimum oxygen exchange, regardless of species.
Collapse
Affiliation(s)
- Miyuki Unekawa
- Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
| | | | | | | | | | | |
Collapse
|
17
|
Demchenko IT, Luchakov YI, Moskvin AN, Gutsaeva DR, Allen BW, Thalmann ED, Piantadosi CA. Cerebral blood flow and brain oxygenation in rats breathing oxygen under pressure. J Cereb Blood Flow Metab 2005; 25:1288-300. [PMID: 15789033 DOI: 10.1038/sj.jcbfm.9600110] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hyperbaric oxygen (HBO(2)) increases oxygen tension (PO(2)) in blood but reduces blood flow by means of O(2)-induced vasoconstriction. Here we report the first quantitative evaluation of these opposing effects on tissue PO(2) in brain, using anesthetized rats exposed to HBO(2) at 2 to 6 atmospheres absolute (ATA). We assessed the contribution of regional cerebral blood flow (rCBF) to brain PO(2) as inspired PO(2) (PiO(2)) exceeds 1 ATA. We measured rCBF and local PO(2) simultaneously in striatum using collocated platinum electrodes. Cerebral blood flow was computed from H(2) clearance curves in vivo and PO(2) from electrodes calibrated in vitro, before and after insertion. Arterial PCO(2) was controlled, and body temperature, blood pressure, and EEG were monitored. Scatter plots of rCBF versus PO(2) were nonlinear (R(2)=0.75) for rats breathing room air but nearly linear (R(2)=0.88-0.91) for O(2) at 2 to 6 ATA. The contribution of rCBF to brain PO(2) was estimated at constant inspired PO(2), by increasing rCBF with acetazolamide (AZA) or decreasing it with N-nitro-L-arginine methyl ester (L-NAME). At basal rCBF (78 mL/100 g min), local PO(2) increased 7- to 33-fold at 2 to 6 ATA, compared with room air. A doubling of rCBF increased striatal PO(2) not quite two-fold in rats breathing room air but 13- to 64-fold in those breathing HBO(2) at 2 to 6 ATA. These findings support our hypothesis that HBO(2) increases PO(2) in brain in direct proportion to rCBF.
Collapse
Affiliation(s)
- Ivan T Demchenko
- Center for Hyperbaric Medicine and Environmental Physiology, Duke University, Durham, North Carolina 27710, USA
| | | | | | | | | | | | | |
Collapse
|
18
|
NAKANO A, SUGII Y, MINAMIYAMA M, SEKI J, NIIMI H. Velocity Profiles of Pulsatile Blood Flow in Arterioles with Bifurcation and Confluence in Rat Mesnetery Measured by Particle Image Velocimetry. ACTA ACUST UNITED AC 2005. [DOI: 10.1299/jsmec.48.444] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Yasuhiko SUGII
- Department of Quantum Engineering and Systems Science, The University of Tokyo
| | - Motomu MINAMIYAMA
- Department of Clinical Engineering, Hiroshima International University
| | - Junji SEKI
- National Cardiovascular Center Research Institute
| | - Hideyuki NIIMI
- National Cardiovascular Center Research Institute
- Tasly Microcirculation Research Center, Peking University Health Science Center
| |
Collapse
|
19
|
Grinberg OY, Hou H, Roche MA, Merlis J, Grinberg SA, Khan N, Swartz HM, Dunn JF. Modeling of the response of ptO2 in rat brain to changes in physiological parameters. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2005; 566:111-8. [PMID: 16594142 DOI: 10.1007/0-387-26206-7_16] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
It is known that oxygen tension in tissue (ptO2) will change in response to an alteration of physiological parameters including: pCO2 in arterial blood, blood flow, capillary density, oxygen carrying capacity, and p50 of hemoglobin. We have used modeling to compute the change of PtO2 in response to changes of each physiological parameter and related these changes to experimental data. The oxygen distribution in a Krogh cylinder was computed assuming a linear decrease of hemoglobin saturation from the arterial to the venous end of the capillary. Parameters of the model were used to compute the baseline cerebral PtO2 expressed as the mean value of the PtO2 over the whole cylinder. These parameters were adjusted to derive PtO2 values close to those measured at the relevant experimental conditions. Then each desired parameter was varied to calculate the change in PtO2 related to this parameter. Effects of different factors on cerebral PtO2 were modeled and compared with experimental values obtained with various experimental interventions including: changing CBF, modifying p50 with the allosteric modifier RSR13, modification of capillary density, and hemoglobin content. An acceptable agreement of the computed and the experimental changes of the cerebral PtO2 was obtained for these experimental conditions.
Collapse
|
20
|
de Zwart JA, Silva AC, van Gelderen P, Kellman P, Fukunaga M, Chu R, Koretsky AP, Frank JA, Duyn JH. Temporal dynamics of the BOLD fMRI impulse response. Neuroimage 2004; 24:667-77. [PMID: 15652302 DOI: 10.1016/j.neuroimage.2004.09.013] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Revised: 09/07/2004] [Accepted: 09/08/2004] [Indexed: 11/16/2022] Open
Abstract
Using computer simulations and high-resolution fMRI experiments in humans (n=6) and rats (n=8), we investigated to what extent BOLD fMRI temporal resolution is limited by dispersion in the venous vasculature. For this purpose, time-to-peak (TTP) and full-width at half-maximum (FWHM) of the BOLD impulse response (IR) function were determined. In fMRI experiments, a binary m-sequence probe method was used to obtain high-sensitivity model-free single-pixel estimates of IR. Simulations of postcapillary flow suggested that flow-related dispersion leads to a TTP and FWHM increase, which can amount to several seconds in larger pial veins. fMRI experiments showed substantial spatial variation in IR timing within human visual cortex, together with a correlation between TTP and FWHM. Averaged across the activated regions and across subjects, TTP and FWHM were 4.51+/-0.52 and 4.04+/-0.42 s, respectively. In regions of interest (ROI) weighted toward the larger venous structures, TTP and FWHM increased to 5.07+/-0.64 and 4.32+/-0.48 s, respectively. In rat somatosensory cortex, TTP and FWHM were substantially shorter than in humans (2.73+/-0.60 and 2.28+/-0.63 s, respectively). These results are consistent with a substantial macrovascular dispersive contribution to BOLD IR in humans, and furthermore suggest that neurovascular coupling is a relatively rapid process, with a resolution below 2.3 s FWHM.
Collapse
Affiliation(s)
- Jacco A de Zwart
- Laboratory of Functional and Molecular Imaging, NINDS, National Institutes of Health, Bethesda, MD 20892-1065, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Jung JC, Mehta AD, Aksay E, Stepnoski R, Schnitzer MJ. In vivo mammalian brain imaging using one- and two-photon fluorescence microendoscopy. J Neurophysiol 2004; 92:3121-33. [PMID: 15128753 PMCID: PMC2826362 DOI: 10.1152/jn.00234.2004] [Citation(s) in RCA: 224] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
One of the major limitations in the current set of techniques available to neuroscientists is a dearth of methods for imaging individual cells deep within the brains of live animals. To overcome this limitation, we developed two forms of minimally invasive fluorescence microendoscopy and tested their abilities to image cells in vivo. Both one- and two-photon fluorescence microendoscopy are based on compound gradient refractive index (GRIN) lenses that are 350-1,000 microm in diameter and provide micron-scale resolution. One-photon microendoscopy allows full-frame images to be viewed by eye or with a camera, and is well suited to fast frame-rate imaging. Two-photon microendoscopy is a laser-scanning modality that provides optical sectioning deep within tissue. Using in vivo microendoscopy we acquired video-rate movies of thalamic and CA1 hippocampal red blood cell dynamics and still-frame images of CA1 neurons and dendrites in anesthetized rats and mice. Microendoscopy will help meet the growing demand for in vivo cellular imaging created by the rapid emergence of new synthetic and genetically encoded fluorophores that can be used to label specific brain areas or cell classes.
Collapse
Affiliation(s)
- Juergen C Jung
- Department of Biological Sciences, Stanford University, Stanford, CA 94305-5435, USA
| | | | | | | | | |
Collapse
|
22
|
Schulte ML, Wood JD, Hudetz AG. Cortical electrical stimulation alters erythrocyte perfusion pattern in the cerebral capillary network of the rat. Brain Res 2003; 963:81-92. [PMID: 12560113 DOI: 10.1016/s0006-8993(02)03848-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The effect of direct cortical electrical stimulation on the pattern of erythrocyte perfusion in the capillary network of the rat cerebral cortex was studied by fluorescence intravital video-microscopy. The movement of fluorescently labeled red blood cells (FRBCs) in individual capillaries 50-70 microm subsurface in the dorsal somatosensory cortex was visualized using a closed cranial window. Cortical stimulation electrodes were placed on opposite sides of the window. FRBC velocity (mm/s) and supply rate (cells/s) were measured in 51 capillaries from six rats before and during electrical stimulation of increasing intensities (15-s trains of 3-Hz, 3-ms, 0.5-5.0-mA, square pulses). FRBC velocity, supply rate, and the instantaneous capillary erythrocyte content (lineal cell density, LCD, cells/mm) increased with the stimulation current and reached maxima of 110, 160 and 33% above control, respectively. Capillaries with low resting velocity showed a greater response than those with high resting velocity. The fraction of capillaries in which FRBC velocity increased was not constant, but increased with the stimulation current, as did the magnitude of the velocity change in these capillaries. A few capillaries showed a negative FRBC velocity response at stimulations <4 mA. These results suggest that a robust rise in the fraction of responding (engaged) capillaries and a smaller rise in the capillary LCD contribute to neuronal activation-induced cortical hyperemia. Thus, capillary engagement and erythrocyte recruitment appear to represent important components of the cortical functional hyperemic response. These results provide insight into some of the specific hemodynamic changes associated with functional hyperemia occurring at the capillary level.
Collapse
Affiliation(s)
- M L Schulte
- Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | | | | |
Collapse
|
23
|
Thomale UW, Schaser KD, Unterberg AW, Stover JF. Visualization of rat pial microcirculation using the novel orthogonal polarized spectral (OPS) imaging after brain injury. J Neurosci Methods 2001; 108:85-90. [PMID: 11459621 DOI: 10.1016/s0165-0270(01)00375-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Recently, the novel optical system, orthogonal polarized spectral (OPS) imaging was developed to visualize microcirculation. Investigation of changes in microcirculation is essential for physiological, pathophysiological, and pharmacological studies. In the present study applicability of OPS imaging was assessed to study pial microcirculation in normal and traumatized rat brain. High quality images of rat pial microcirculation in normal and traumatized rats were generated with the OPS imaging, allowing to easily differentiate arterioles and venules with the dura remaining intact. In non-traumatized rats, mean vessel diameter of arterioles and venules of five different cortical regions was 19.1+/-2.7 and 22.2+/-1.4 microm, respectively. In the early phase following focal cortical contusion vessel diameter was significantly decreased in arterioles by 28% while diameter in venules was significantly increased by 27%. For technical reasons velocity in arterioles was not measurable. In venules, mean flow velocity of 0.68+/-0.08 mm/s was significantly decreased by 50% at 30 min after trauma. OPS imaging is an easy to use optical system allowing to generate high quality images and to reliably investigate pial microcirculation without having to remove the dura. This technique opens the possibility to perform longitudinal studies investigating changes in pial microcirculation.
Collapse
Affiliation(s)
- U W Thomale
- Department of Neurosurgery, Charité, Virchow Medical Center, Humboldt-University of Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | | | | | | |
Collapse
|
24
|
St Lawrence KS, Frank JA, McLaughlin AC. Effect of restricted water exchange on cerebral blood flow values calculated with arterial spin tagging: a theoretical investigation. Magn Reson Med 2000; 44:440-9. [PMID: 10975897 DOI: 10.1002/1522-2594(200009)44:3<440::aid-mrm15>3.0.co;2-6] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Arterial spin tagging techniques originally used the one-compartment Kety model to describe the dynamics of tagged water in the brain. The work presented here develops a more realistic model that includes the contribution of tagged water in the capillary bed and accounts for the finite time required for water to diffuse across the blood-brain barrier. The new model was used to evaluate potential errors in cerebral blood flow values calculated using the one-compartment Kety model. The results predict that if the one-compartment Kety model is used to analyze arterial spin tagging data the observed grey matter cerebral blood flow values should be relatively insensitive to restricted diffusion of water across the capillary bed. For instance, the observed grey matter cerebral blood flow should closely approximate the true cerebral blood flow and not the product of the extraction fraction and the cerebral blood flow. This prediction is in agreement with recent experimental arterial spin tagging results.
Collapse
Affiliation(s)
- K S St Lawrence
- Laboratory of Diagnostic Radiology Research, CC, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | | | |
Collapse
|
25
|
Ritter LS, Orozco JA, Coull BM, McDonagh PF, Rosenblum WI. Leukocyte accumulation and hemodynamic changes in the cerebral microcirculation during early reperfusion after stroke. Stroke 2000; 31:1153-61. [PMID: 10797180 DOI: 10.1161/01.str.31.5.1153] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Leukocytes contribute to cerebral ischemia-reperfusion injury. However, few experimental models examine both in vivo behavior of leukocytes and microvascular rheology after stroke. The purpose of the present study was to characterize patterns of leukocyte accumulation in the cerebral microcirculation and to examine the relationship between leukocyte accumulation and microcirculatory hemodynamics after middle cerebral artery occlusion and reperfusion (MCAO-R). METHODS Male rats (250 to 350 g) were anesthetized and ventilated. Tail catheters were inserted for measurement of arterial blood gases and administration of drugs. Body temperature was maintained at 37 degrees C. Animals were subjected to 2 hours of MCAO by the filament method. A cranial-window preparation was performed, and the brain was superfused with warm, aerated artificial cerebrospinal fluid. Reperfusion was initiated by withdrawing the filament, and the pial microcirculation was observed by use of intravital fluorescence microscopy. Leukocyte accumulation in venules, arterioles, and capillaries; leukocyte rolling in venules; and leukocyte venular shear rate were assessed during 1 hour of reperfusion. RESULTS We found significant leukocyte adhesion in cerebral venules during 1 hour of reperfusion after 2 hours of MCAO. Leukocyte trapping in capillaries and adhesion to arterioles after MCAO-R tended to increase compared with controls, but the increase was not significant. We also found that shear rate was significantly reduced in venules during early reperfusion after MCAO. CONCLUSIONS A model using the filament method of stroke and fluorescence microscopy was used to examine white-cell behavior and hemodynamics in the cerebral microcirculation after MCAO-R. We observed a significant increase in leukocyte rolling and adhesion in venules and a significant decrease in blood shear rate in the microcirculation of the brain during early reperfusion. Leukocytes may activate and damage the blood vessels and surrounding brain cells, which contributes to an exaggerated inflammatory component to reperfusion. The model described can be used to examine precisely blood cell-endothelium interactions and hemodynamic changes in the microcirculation during postischemic reperfusion. Information from these and similar experiments may contribute to our understanding of the early inflammatory response in the brain during reperfusion after stroke.
Collapse
Affiliation(s)
- L S Ritter
- University of Arizona College of Nursing, Tucson, AZ, USA.
| | | | | | | | | |
Collapse
|
26
|
Seylaz J, Charbonné R, Nanri K, Von Euw D, Borredon J, Kacem K, Méric P, Pinard E. Dynamic in vivo measurement of erythrocyte velocity and flow in capillaries and of microvessel diameter in the rat brain by confocal laser microscopy. J Cereb Blood Flow Metab 1999; 19:863-70. [PMID: 10458593 DOI: 10.1097/00004647-199908000-00005] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A new method for studying brain microcirculation is described. Both fluorescently labeled erythrocytes and plasma were visualized on-line through a closed cranial window in anesthetized rats, using laser-scanning two-dimension confocal microscopy. Video images of capillaries, arterioles, and venules were digitized off-line to measure microvessel diameter and labeled erythrocyte flow and velocity in parenchymal capillaries up to 200 microm beneath the brain surface. The method was used to analyze the rapid adaptation of microcirculation to a brief decrease in perfusion pressure. Twenty-second periods of forebrain ischemia were induced using the tour-vessel occlusion model in eight rats. EEG, arterial blood pressure, and body temperature were continuously controlled. In all conditions, labeled erythrocyte flow and velocity were both very heterogeneous in capillaries. During ischemia, capillary perfusion was close to 0, but a low blood flow persisted in arterioles and venules, while EEG was flattening. The arteriole and venule diameter did not significantly change. At the unclamping of carotid arteries, there was an instantaneous increase (by about 150%) of arteriole diameter. Capillary erythrocyte flow and velocity increased within 5 seconds, up to, respectively, 346 +/- 229% and 233 +/- 156% of their basal value. No capillary recruitment of erythrocytes was detected. All variables returned to their basal levels within less than 100 seconds after declamping. The data are discussed in terms of a possible involvement of shear stress in the reperfusion period.
Collapse
Affiliation(s)
- J Seylaz
- Laboratoire de Recherches Cérébrovasculaires, CNRS UPR 646, Université Paris 7, France
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Kleinfeld D, Mitra PP, Helmchen F, Denk W. Fluctuations and stimulus-induced changes in blood flow observed in individual capillaries in layers 2 through 4 of rat neocortex. Proc Natl Acad Sci U S A 1998; 95:15741-6. [PMID: 9861040 PMCID: PMC28114 DOI: 10.1073/pnas.95.26.15741] [Citation(s) in RCA: 574] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cortical blood flow at the level of individual capillaries and the coupling of neuronal activity to flow in capillaries are fundamental aspects of homeostasis in the normal and the diseased brain. To probe the dynamics of blood flow at this level, we used two-photon laser scanning microscopy to image the motion of red blood cells (RBCs) in individual capillaries that lie as far as 600 micrometers below the pia mater of primary somatosensory cortex in rat; this depth encompassed the cortical layers with the highest density of neurons and capillaries. We observed that the flow was quite variable and exhibited temporal fluctuations around 0.1 Hz, as well as prolonged stalls and occasional reversals of direction. On average, the speed and flux (cells per unit time) of RBCs covaried linearly at low values of flux, with a linear density of approximately 70 cells per mm, followed by a tendency for the speed to plateau at high values of flux. Thus, both the average velocity and density of RBCs are greater at high values of flux than at low values. Time-locked changes in flow, localized to the appropriate anatomical region of somatosensory cortex, were observed in response to stimulation of either multiple vibrissae or the hindlimb. Although we were able to detect stimulus-induced changes in the flux and speed of RBCs in some single trials, the amplitude of the stimulus-evoked changes in flow were largely masked by basal fluctuations. On average, the flux and the speed of RBCs increased transiently on stimulation, although the linear density of RBCs decreased slightly. These findings are consistent with a stimulus-induced decrease in capillary resistance to flow.
Collapse
Affiliation(s)
- D Kleinfeld
- Department of Physics, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0319, USA
| | | | | | | |
Collapse
|
28
|
Ishikawa M, Sekizuka E, Shimizu K, Yamaguchi N, Kawase T. Measurement of RBC velocities in the rat pial arteries with an image-intensified high-speed video camera system. Microvasc Res 1998; 56:166-72. [PMID: 9828154 DOI: 10.1006/mvre.1998.2100] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mean centerline red blood cell (RBC) velocity of the rat pial artery was measured using an image-intensified high-speed (1000 frames/s) video camera system and RBCs labeled with fluorescein isothiocyanate (FITC). Some investigations measuring RBC velocity have been made in most organs, but the RBC velocity of the pial artery has not yet been measured with this system using FITC labeled RBC. After recording the emission of the FITC labeled RBC through a closed cranial window using this system, the authors analyzed the videotape. The movement of each individual RBC for several milliseconds over a distance of 50 microm could be pursued. The mean centerline RBC velocity in normal rats varied between 1.0 and 9.0 mm/s (most of the measurements we taken in vessels ranging between 20 and 80 microm in diameter). As the diameter of the pial artery becomes smaller, the blood flow rate (pi x (diameter/2)2 x (mean centerline velocity/1.6)) tends to become smaller. During CO2 inhalation, the pial artery diameter, mean centerline RBC velocity, and blood flow rate increased with statistical significance. Mean centerline RBC velocities in the cerebral microcirculation could not be measured directly with accuracy using the older methods (30 frames/s). However, this method is useful for investigation of the cerebral microcirculation and is considered to be applicable for studying the behavior of leukocytes or platelets, which will be examined in a subsequent study.
Collapse
Affiliation(s)
- M Ishikawa
- Department of Neurosurgery, Saitama National Hospital, Saitama, Japan
| | | | | | | | | |
Collapse
|
29
|
Fehér G, Schulte ML, Weigle CG, Kampine JP, Hudetz AG. Postnatal remodeling of the leptomeningeal vascular network as assessed by intravital fluorescence video-microscopy in the rat. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1996; 91:209-17. [PMID: 8852371 DOI: 10.1016/0165-3806(95)00178-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An intriguing characteristic of the ontogenic development of the cerebral vasculature is the rapid differentiation of the neonatal leptomeningeal vascular plexus into the mature, adult network form. The physiological and cellular mechanisms of this cerebrovascular remodeling process are unclear. The objective of this work was to determine and correlate changes in vascular density, network pattern and flow velocity in leptomeningeal microvessels of the rat during postnatal development in vivo. To this end, microvascular diameter, segment length, and vascular density of reconstructed leptomeningeal networks were measured from video-recordings of the microcirculation visualized through a cranial window in 0-15-day-old Sprague-Dawley rats. The velocity of erythrocytes in the microvessels was measured by frame to frame tracking of fluorescently labeled red blood cells. We found that surface vascular density (total vessel length per area), node density and segment density (object per area) decreased significantly by the second week after birth. Anastomosing vascular polygons, characteristic to newborn networks, became less numerous and larger in diameter during the postnatal 2-week period, indicating progressive rarefaction of the networks. Vessel diameter and red cell velocity showed transient increases at 1.5 weeks. The velocity/diameter ratio (V/D), an index of wall shear rate, increased by the age of 1.5 weeks and remained unchanged afterwards. There was a negative correlation between V/D and diameter at 1 week; this relationship was reversed to a positive correlation at 2 weeks. We conclude that postnatal remodeling of the leptomeningeal vascular network is associated with rarefaction and an adaptation of vessel caliber to wall shear rate. These changes may contribute to arterio-venous differentiation and redistribution of blood flow from the superficial to the intracortical vasculature in the developing brain.
Collapse
Affiliation(s)
- G Fehér
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226, USA
| | | | | | | | | |
Collapse
|
30
|
Abstract
We determined whether cerebral arterioles in vitro adjust their diameters in response to changes in intraluminal flow rate and pressure. Intracerebral arterioles (38- to 55-microns diameter) were isolated from Sprague-Dawley rats and cannulated with a perfusion system that permitted separate control of intraluminal pressure and flow rates. Increasing pressure at 0 flow, in 20 mm Hg steps from 20 to 100 mm Hg, resulted in myogenic constriction, which was greatest at 60 mm Hg (approximately 20%). Increasing flow rate at a constant pressure of 60 mm Hg elicited a biphasic response. At flow rates of up to 10 microL/min, the arterioles dilated by up to 14.5 +/- 2.2% of their control diameter. At higher (> 10 microL/min) flow rates, however, a progressive restoration of resting diameter was observed. Application of the nitric oxide synthase inhibitor NG-mono-methyl-L-arginine (L-NMMA, 0.1 mmol/L) caused a 15.4 +/- 1.7% decrease in control diameter (at 60 mm Hg, zero flow). Although L-NMMA did not affect the responses to increases in pressure or to vasodilators (adenosine and pH 6.8 buffer), it abolished the dilator responses to flow rate increases and to acetylcholine. In contrast, inhibition of prostaglandin synthesis by indomethacin (10 mumol/L) had no effect on flow-induced dilation. These results show that changes in intraluminal flow rates and pressure can independently influence cerebral arteriolar tone and suggest that the flow-induced dilator responses of cerebral arterioles are mediated by an arginine metabolite, such as nitric oxide.
Collapse
Affiliation(s)
- A C Ngai
- Department of Neurological Surgery, University of Washington School of Medicine, Seattle, USA
| | | |
Collapse
|
31
|
Ye GF, Moore TW, Buerk DG, Jaron D. A compartmental model for oxygen-carbon dioxide coupled transport in the microcirculation. Ann Biomed Eng 1994; 22:464-79. [PMID: 7825749 DOI: 10.1007/bf02367083] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We present a multicompartmental model for an oxygen-carbon dioxide transport system. The compartmental equations and their lumped parameters are derived through space averaging of the corresponding distributed model. The model can predict compartmental distributions of oxygen and carbon dioxide partial pressures, oxygen-hemoglobin saturation, and pH. Other unique features include the effects of the radial distribution of partial pressures and the difference in metabolic rates between vessel wall and tissue. A model for the cat brain, based on this formulation, is compared with results of experiments and with two types of earlier models: one without space averaging and one without carbon dioxide transport. The results suggest that space averaging the convective terms significantly affects the behavior of the model. This is consistent with conclusions from our earlier oxygen-only model. Our observations also demonstrate, however, significant differences between the results from the oxygen-carbon dioxide model and the oxygen-only model. For instance, at low blood flow rates or at low level of oxygen input, predicted oxygen partial pressures can differ by as much as 30% between the two models. Results obtained from the present model are supported by available experimental findings.
Collapse
Affiliation(s)
- G F Ye
- Biomedical Engineering and Science Institute, Drexel University, Philadelphia, PA 19104
| | | | | | | |
Collapse
|
32
|
Villringer A, Them A, Lindauer U, Einhäupl K, Dirnagl U. Capillary perfusion of the rat brain cortex. An in vivo confocal microscopy study. Circ Res 1994; 75:55-62. [PMID: 8013082 DOI: 10.1161/01.res.75.1.55] [Citation(s) in RCA: 214] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Confocal laser-scanning microscopy was used to visualize subsurface cerebral microvessels labeled with intravascular fluorescein in a closed cranial window model of the anesthetized rat. In noninvasive optical sections up to 250 microns beneath the brain surface, plasma perfusion and blood cell perfusion of individual capillaries were studied. Under resting conditions, in all cerebral capillaries the presence of plasma flow as demonstrated by the appearance of an intravenously injected fluorescent tracer within 20 seconds after injection. Plasma flow was verified even in capillaries that contained stationary erythrocytes or leukocytes; 91.1% of the capillaries contained flowing blood cells, 5.2% contained stationary blood cells, and no blood cells were seen in 3.6%. Mean blood cell velocity was 498.3 +/- 443.9 microns/s, and the mean blood cell supply rate was 35.75 +/- 28.01 cells per second. When capillaries were continuously observed for 1 minute, "on" and "off" periods of blood cell flow were noted. During hypercapnia (increase of PCO2 from 33.25 to 50.26 mm Hg), mean blood cell flux increased from 38.6 +/- 17.2 to 55.5 +/- 12.2 per second (P < .005, paired t test of mean values in six animals), and blood cell velocity increased from 519.5 +/- 254.8 to 828.5 +/- 460.8 microns/s (P = .074, paired t test of mean values in six animals). Homogeneity of blood cell flux increased as indicated by the coefficient of variation decreasing from 44.6% to 22.0%, and the portion of poorly perfused capillaries (blood cell flux, < 40 per second) decreased from 59.2% to 22.4%.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- A Villringer
- Department of Neurology, Charité Hospital, Humboldt University, Berlin, Germany
| | | | | | | | | |
Collapse
|
33
|
Schacterle RS, Ribando RJ, Adams JM. A model of brain arteriolar oxygen and carbon dioxide transport during anemia. J Cereb Blood Flow Metab 1993; 13:872-80. [PMID: 8360293 DOI: 10.1038/jcbfm.1993.109] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Existing experimental and theoretical evidence suggests that precapillary diffusion of O2 and CO2 occurs between arterioles and tissue under normal physiologic conditions. However, limited information is available on arteriolar gas transport during anemia. With use of a mathematical model of an arteriolar network in brain tissue, anemic hematocrits of 35, 25, and 15% were modeled to determine the effect of anemia on the exchange, the change in the equilibrium tissue O2 and CO2 tensions, and the increase in blood flow needed to restore tissue oxygenation. We found that the blood PO2 exiting the network fell from 66 mm Hg normally to 48 mm Hg during the severest anemia. Concurrently, the equilibrium tissue O2 tensions dropped from 44 to 23 mm Hg. For CO2 the exit blood PCO2 was 58 mm Hg for a 15% hematocrit, an increase of 4 mm Hg from the normal value, and equilibrium tissue PCO2 increased from 56 to 61 mm Hg. Blood flow increases from normal values necessary to offset the effects of the decreased O2 delivery to the tissue were 26, 86, and 222%, respectively, for hematocrits of 35, 25, and 15%. We compared our model results with recent experimental studies that have suggested that the amount of O2 diffusion is much higher than predicted values. We found that these experimental O2 gradients are three to four times larger than theoretical.
Collapse
Affiliation(s)
- R S Schacterle
- Department of Biomedical Engineering, University of Virginia, Charlottesville
| | | | | |
Collapse
|
34
|
Rovainen CM, Woolsey TA, Blocher NC, Wang DB, Robinson OF. Blood flow in single surface arterioles and venules on the mouse somatosensory cortex measured with videomicroscopy, fluorescent dextrans, nonoccluding fluorescent beads, and computer-assisted image analysis. J Cereb Blood Flow Metab 1993; 13:359-71. [PMID: 7683023 DOI: 10.1038/jcbfm.1993.49] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cortical surface vessels were monitored through closed cranial windows with an epifluorescence microscope and SIT or ICCD cameras. Fluorescent dextrans or 1.3 microns latex beads were injected into the contralateral jugular vein for plasma labeling and for vascular transits. For close arterial transits, these tracers or physiological saline were injected into the ipsilateral external carotid artery. AVTTs were calculated from intensity differences of tracers between a branch of the MCA and a vein draining the same cortical region over time. AVTTs for saline dilutions of RBCs were significantly shorter (0.73 times) than for dextrans. Both dextrans and beads distributed with plasma. With FITC-dextran, inner diameters of arterioles and venules averaged 6 microns larger than hemoglobin under green light. This difference was likely due to the segregation of red blood cells and plasma during flow. Velocities of individual fluorescent beads were measured in pial vessels by strobe epi-illumination. Plots of bead velocities against radial position in arterioles were blunted parabolas. Peak shear rates in the marginal layer next to the vessel walls were determined directly from bead tracks in arterioles (D = 21-71 microns) and were 1.32 times the Poiseuille estimate. The calculated peak wall shear stress was 39 +/- 14 dyn/cm2 (mean +/- SD) for these arterioles but was probably severalfold greater in the smallest terminal pial arterioles. Vmax near the axes of arterioles increased with D+0.5. The calculated peak wall shear rate was highest in small arterioles and decreased with D-0.5. The calculated flow Q increased with D+2.5. These methods permit direct, simultaneous, dynamic measurements on multiple identified cerebral microvessels.
Collapse
Affiliation(s)
- C M Rovainen
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110
| | | | | | | | | |
Collapse
|
35
|
Hudetz AG, Weigle CG, Fenoy FJ, Roman RJ. Use of fluorescently labeled erythrocytes and digital cross-correlation for the measurement of flow velocity in the cerebral microcirculation. Microvasc Res 1992; 43:334-41. [PMID: 1635476 DOI: 10.1016/0026-2862(92)90029-o] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- A G Hudetz
- Department of Physiology, Medical College of Wisconsin, Milwaukee 53226
| | | | | | | |
Collapse
|
36
|
Rovainen CM, Wang DB, Woolsey TA. Strobe epi-illumination of fluorescent beads indicates similar velocities and wall shear rates in brain arterioles of newborn and adult mice. Microvasc Res 1992; 43:235-9. [PMID: 1584065 DOI: 10.1016/0026-2862(92)90020-p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- C M Rovainen
- Department of Cell Biology, Washington University School of Medicine, St. Louis, Missouri 63110
| | | | | |
Collapse
|
37
|
Dirnagl U, Villringer A, Einhäupl KM. In-vivo confocal scanning laser microscopy of the cerebral microcirculation. J Microsc 1992; 165:147-57. [PMID: 1552568 DOI: 10.1111/j.1365-2818.1992.tb04312.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Confocal scanning laser microscopy (CSLM) was used to study the microcirculation of the brain neocortex in anaesthetized rats. After removal of the dura mater, implantation of a closed cranial window, and intravenous injection of fluorescein, three-dimensional reconstructions of cortical capillaries were performed down to a depth of 250 microns below the pial surface. Using a one-dimensional approach (single line scanning), erythrocyte (negative contrast in fluorescently labelled plasma) and leucocyte (labelled with rhodamine 6 G) velocity and supply rate in cortical capillaries were measured. The effect of CO2-inhalation on capillary blood flow dynamics was studied. Capillaries were imaged continuously for up to 1 h without changes in flow or fluorescence pattern. However, by increasing the laser power 10-100-fold, aggregate formation was induced and capillaries were occluded, possibly due to damage to vascular endothelium. We conclude that CSLM can be used to study morphological and dynamic aspects of fluorescently labelled subsurface structures in organs of experimental animals.
Collapse
Affiliation(s)
- U Dirnagl
- Department of Neurology, University of Munich, Germany
| | | | | |
Collapse
|
38
|
Dirnagl U, Villringer A, Gebhardt R, Haberl RL, Schmiedek P, Einhäupl KM. Three-dimensional reconstruction of the rat brain cortical microcirculation in vivo. J Cereb Blood Flow Metab 1991; 11:353-60. [PMID: 2016343 DOI: 10.1038/jcbfm.1991.74] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We used confocal laser scanning microscopy (CLSM) to investigate the morphology and three-dimensional relationships of the microcirculation of the superficial layers of the rat brain cortex in vivo. In anesthetized rats equipped with a closed cranial window (dura mater removed), after i.v. injection of 3 mg/100 g of body weight of fluorescein in 0.5 ml of saline, serial optical sections of the brain cortex intraparenchymal microcirculation were taken. Excitation was at a wavelength of 488 nm (argon laser), and emission was collected above 515 nm. CLSM provided images of brain vessels with sufficient signal-to-noise ratio for three-dimensional reconstructions down to a depth of 250 microns beneath the surface of the brain. Compared to conventional fluorescence microscopy, CLSM has a much higher axial resolution and higher depth of penetration. Laser light-induced intravascular aggregates, irregularities of erythrocyte flow, or microvascular occlusions ("light and dye injury") were not apparent in the current experimental paradigm. CLSM is a promising new tool for in vivo visualization of the cerebral microcirculation. Future studies have to characterize the potential damage to the tissue dye mechanisms.
Collapse
Affiliation(s)
- U Dirnagl
- Department of Neurology, University of Munich, Germany
| | | | | | | | | | | |
Collapse
|
39
|
Sharan M, Jones MD, Koehler RC, Traystman RJ, Popel AS. A compartmental model for oxygen transport in brain microcirculation. Ann Biomed Eng 1989; 17:13-38. [PMID: 2919811 DOI: 10.1007/bf02364271] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A compartmental model is formulated for oxygen transport in the cerebrovascular bed of the brain. The model considers the arteriolar, capillary and venular vessels. The vascular bed is represented as a series of compartments on the basis of blood vessel diameter. The formulation takes into account such parameters as hematocrit, vascular diameter, blood viscosity, blood flow, metabolic rate, the nonlinear oxygen dissociation curve, arterial PO2, P50 (oxygen tension at 50% hemoglobin saturation with O2) and carbon monoxide concentration. The countercurrent diffusional exchange between paired arterioles and venules is incorporated into the model. The model predicts significant longitudinal PO2 gradients in the precapillary vessels. However, gradients of hemoglobin saturation with oxygen remain fairly small. The longitudinal PO2 gradients in the postcapillary vessels are found to be very small. The effect of the following variables on tissue PO2 is studied: blood flow, PO2 in the arterial blood, hematocrit, P50, concentration of carbon monoxide, metabolic rate, arterial diameter, and the number of perfused capillaries. The qualitative features of PO2 distribution in the vascular network are not altered with moderate variation of these parameters. Finally, the various types of hypoxia, namely hypoxic, anemic and carbon monoxide hypoxia, are discussed in light of the above sensitivity analysis.
Collapse
Affiliation(s)
- M Sharan
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | | | | | | | | |
Collapse
|
40
|
Hudetz AG, Conger KA, Pal M, Horton CR. Mathematical analysis of network topology in the cerebrocortical microvasculature. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 222:87-94. [PMID: 3364304 DOI: 10.1007/978-1-4615-9510-6_10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The three-dimensional branching pattern of deep cerebrocortical capillary networks was reconstructed from histological sections. The distribution of blood flow in a mathematical model of the reconstructed network was calculated. The transit of red blood cells through the network was simulated by computer, and the total path length traveled by the cells was estimated. The results support both anatomical and hemodynamic heterogeneity of the cerebrocortical microvascular system.
Collapse
Affiliation(s)
- A G Hudetz
- Center for Rehabilitation Science and Biomedical Engineering, Louisiana Tech University, Ruston
| | | | | | | |
Collapse
|
41
|
Morii S, Ngai AC, Winn HR. Reactivity of rat pial arterioles and venules to adenosine and carbon dioxide: with detailed description of the closed cranial window technique in rats. J Cereb Blood Flow Metab 1986; 6:34-41. [PMID: 3080442 DOI: 10.1038/jcbfm.1986.5] [Citation(s) in RCA: 165] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This study describes a closed cranial window technique that allows the observation and measurement of rat pial arterioles and venules in situ. The resolving power of this system is 1-2 microns. Using this sensitive technique, we characterized the responses to 7% carbon dioxide inhalation and adenosine in arterioles (10-70 microns) and venules (15-100 microns). During carbon dioxide inhalation, larger arterioles (greater than 40 microns) dilated more than smaller arterioles (less than 20 microns). There was limited vasoreactivity of pial venules during CO2 inhalation. Dilation of arterioles was initially observed with an adenosine concentration of 10(-8) M. Almost a twofold increase in diameter was noted at 10(-3) M. In contrast to the effect of CO2 inhalation, the degree of dilation with topical application of adenosine was not size dependent. Pial venules did not respond to adenosine. The technique for observation of pial vessels using the closed cranial window and for measurement of vessel diameter by video camera system microscopy is a powerful tool for studying in vivo the cerebral circulation in the rat.
Collapse
|
42
|
Ivanov KP, Kalinina MK. Microcirculation velocity changes under hypoxia in brain, muscles, liver, and their physiological significance. Microvasc Res 1985; 30:10-8. [PMID: 4021833 DOI: 10.1016/0026-2862(85)90033-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Linear blood flow velocity in brain, muscle capillaries and hepatic sinusoids was measured by means of microfilming in normal and hypoxemic rats (breathing with 7% O2 in N2). The mean flow velocity was found to increase by 66% in brain capillaries and by 12% in hepatic sinusoids. In skeletal muscle the blood flow ceased in about 40% of the capillaries under investigation and in the others the flow velocity slowed down twofold. Different response to hypoxemia was explained by the physiological function peculiarities of the organs in question as well as the type of the energetic exchange and that of the microvascular net structure.
Collapse
|
43
|
Kobari M, Gotoh F, Fukuuchi Y, Tanaka K, Suzuki N, Uematsu D. Blood flow velocity in the pial arteries of cats, with particular reference to the vessel diameter. J Cereb Blood Flow Metab 1984; 4:110-4. [PMID: 6693510 DOI: 10.1038/jcbfm.1984.15] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The blood flow velocity and diameter of feline pial arteries, ranging in diameter from 20 to 200 microns, were measured simultaneously using a newly developed video camera method under steady-state conditions for all other parameters. There was a linear relationship between blood flow velocity and pial artery diameter (y = 0.340x + 0.309), the correlation coefficient being 0.785 (p less than 0.001). The average values for blood flow velocity in pial arteries less than 50 microns, greater than or equal to 50 but less than 100 microns, greater than or equal to 100 but less than 150 microns, and greater than or equal to 150 microns in diameter were 12.9 +/- 1.3, 24.6 +/- 3.4, 42.1 +/- 4.7, and 59.9 +/- 5.3 mm/s, respectively. Blood flow rate was calculated as a product of the cross-sectional area and the flow velocity. The blood flow rate increased exponentially as the pial artery diameter increased (y = 2.71 X 10(-4) x2.98). The average values for blood flow rate in pial arteries less than 50 microns, greater than or equal to 50 but less than 100 microns, greater than or equal to 100 but less than 150 microns and greater than or equal to 150 microns in diameter were 12.8 +/- 1.5, 122.1 +/- 24.8, 510.2 +/- 74.8, and 1524.2 +/- 174.4 10(-3) mm3/s, respectively. Hemorheological parameters such as the wall shear rate and Reynolds' number were also calculated. The data obtained provide a useful basis for further investigations in the field of cerebral circulation.
Collapse
|
44
|
Ma YP, Leung TM, Lau SH, Kwan HC. Pseudo-on-line fast response microvessel dimensions video graphic recorder with electrical signal output. Microvasc Res 1983; 25:133-44. [PMID: 6843368 DOI: 10.1016/0026-2862(83)90010-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The present article describes a new method of microvessel dimensions measurement in which a writing oscilloscope is used to continuously and graphically record the microvessel video signal from television microscopy at a fast rate of 50 records per second. Dimensions of interest, such as the microvessel red blood cell flux diameter, are then easily marked out manually from the graphic records and a dynamic electrical signal proportional to the dimensions is generated. The signal is then recorded on one channel of a multichannel voltage recorder and is synchronised with other experimental signals which have previously been recorded on-line during the experiment. The result is that the dimension signal appears to have been recorded on-line during the experiment as well. This is desirable for electronic signal correlation and processing. This method is useful when poor experimental conditions, commonly encountered, make automatic recording of microvessel dimension unsatisfactory and manual inspection and processing become necessary.
Collapse
|
45
|
Harper SL, Bohlen HG. In vitro and in vivo measurement of red cell velocity with epi- and transillumination. Microvasc Res 1983; 25:186-93. [PMID: 6843372 DOI: 10.1016/0026-2862(83)90014-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Measurement of red cell velocity with the dual-slit cross-correlation method in glass capillary tubes during transillumination indicates that the measured velocity must be divided by a correction factor of approximately 1.6 to equal the average velocity calculated from a known flow and inner diameter. Whether the same correction factor exists when red cell velocity is measured during epiillumination is questionable. Red cell velocity was measured with the dual-slit correlation method nearly simultaneously using epi- (EL) and transillumination (TL) while glass tubes (40-100 microns, i.d.) were pump perfused with whole human blood (hematocrit 39-42%). With TL, the measured velocity is 1.58 +/- 0.07 (SEM) times the calculated average velocity, whereas a factor of 2.04 +/- 0.04 (SEM) was obtained with epiillumination. When intestinal arterioles with approximately the same inner diameters and flow velocities as the glass tubes were used, the ratio of velocities measured with TL to EL was 1.21 +/- 0.02 (SEM) as compared to 1.31 +/- 0.09 (SEM) for glass tubes using TL and EL of the tube at the same pump flow. This similarity of TL to EL velocity ratios for glass tubes and microvessels may be fortuitous or indicate that comparable flow properties and measurement conditions exist for in vitro and in vivo situations. The major finding of the study is, however, that different velocity correction factors exist for EL and TL measurements when the dual-slit correlation method is used to estimate red cell velocities in tubes of an internal diameter of 40-100 microns at normal hematocrits.
Collapse
|
46
|
Gotoh F, Muramatsu F, Fukuuchi Y, Okayasu H, Tanaka K, Suzuki N, Kobari M. Video camera method for simultaneous measurement of blood flow velocity and pial vessel diameter. J Cereb Blood Flow Metab 1982; 2:421-8. [PMID: 7142306 DOI: 10.1038/jcbfm.1982.48] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
A new method for the simultaneous measurement of blood flow velocity and pial vessel diameter is described. The system consists basically of a high-sensitivity vidicon camera, camera control, width analyzer, video densitometer, TV monitor, desktop computer, and multi-pen recorder. The pial vessels are visualized through a cranial window at 25-200x magnification on the TV monitor. The diameter of three target vessels can be recorded simultaneously on the recorder by adjustment of controllable video signal gates using the width analyzer. At the same time, the optical densities of two targets at points upstream and downstream of the pial vessel are measured continuously with video densitometers, and their outputs are recorded on the polygraph and analyzed by the computer. The time difference in the two peaks of time--concentration curves, produced very 2-3 s at the highest frequency by the injection of a small amount of saline through the lingual artery, is measured on-line using the computer. The flow velocity in the vessel is calculated from the time difference and the distance between the two targets. The system was shown to be stable, reliable, and rapid in response. This method may provide a useful tool for research in the field of blood circulation in the brain or any other organ.
Collapse
|
47
|
Rosenblum WI, El-Sabban F. Measurement of red cell velocity with a two-slit technique and cross-correlation: use of reflected light, and either regulated dc or unregulated ac power supplies. Microvasc Res 1981; 22:225-7. [PMID: 7321905 DOI: 10.1016/0026-2862(81)90092-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
48
|
Ivanov KP, Kalinina MK. Blood flow velocity in capillaries of brain and muscles and its physiological significance. Microvasc Res 1981; 22:143-55. [PMID: 7321902 DOI: 10.1016/0026-2862(81)90084-4] [Citation(s) in RCA: 125] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
49
|
Pawlik G, Rackl A, Bing RJ. Quantitative capillary topography and blood flow in the cerebral cortex of cats: an in vivo microscopic study. Brain Res 1981; 208:35-58. [PMID: 7470927 DOI: 10.1016/0006-8993(81)90619-3] [Citation(s) in RCA: 276] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In 50 anesthetized cats the microcirculation in intermediate and deeper layers of the cerebral cortex was visualized in vivo by microtransillumination, and documented by high-speed microcinephotography. The viability of the preparation was verified in a series of experiments demonstrating spontaneous vasomotion and responsiveness to chemical stimulation of pial arterioles and small arteries. Stereological methods for quantitative analysis of projected images of capillaries in a comparatively large tissue volume were employed to determine morphometric and topographical parameters of the asymmetric, highly tortuous intracortical capillary network. Capillary diameters (5.1 +/- 0.84 micrometer), radii of curvature (median 57 micrometer), total capillary lengths per tissue volume 939 +/- 338.2 mm/cu.mm), capillary volume fractions (2.1 +/- 0.51%), total capillary surface areas per tissue volume (15.3 +/- 4.85 sq.mm/cu.mm), and intercapillary distances (median 24.2 micrometer) showed significant interregional differences. The frequency distribution of the lengths of capillary segments (median 108 micrometer) was best described by a Weibull distribution. On the average 90% of all capillaries were continuously perfused. Capillary red cell flow (median velocity 1500 micrometer/sec) was predominantly unidirectional and conspicuously irregular. The variance of capillary red cell velocities (CRCVs) was significantly correlated (tau = 0.48) with capillary tortuosity. An extreme value distribution best described the observed frequency distribution of CRCVs. Flow irregularities represented both white noise and a significant stochastic periodicity at frequencies between 40 and 90 Hz.
Collapse
|
50
|
Gussis GL, Jamison RL, Robertson CR. Determination of erythrocyte velocities in the mammalian inner renal medulla by a video velocity-tracking system. Microvasc Res 1979; 18:370-83. [PMID: 537513 DOI: 10.1016/0026-2862(79)90044-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|