Velocity Perfusion Research Articles

Quantitative transport mapping of multi-delay arterial spin labeling MRI detects early blood perfusion alterations in Alzheimer’s disease

BackgroundQuantitative transport mapping (QTM) of blood velocity, based on the transport equation has been demonstrated higher accuracy and sensitivity of perfusion quantification than the traditional Kety’s method-based cerebral blood flow (CBF). This study aimed to investigate the associations between QTM velocity and cognitive function in Alzheimer’s disease (AD) using multiple post-labeling delay arterial spin labeling (ASL) MRI.MethodsA total of 128 subjects (21 normal controls (NC), 80 patients with mild cognitive impairment (MCI), and 27 AD) were recruited prospectively. All participants underwent MRI examination and neuropsychological evaluation. QTM velocity and traditional CBF maps were computed from multiple delay ASL. Regional quantitative perfusion measurements were performed and compared to study group differences. We tested the hypothesis that cognition declines with reduced cerebral blood perfusion with consideration of age and gender effects.ResultsIn cortical gray matter (GM) and the hippocampus, QTM velocity and CBF showed decreased values in the AD group compared to NC and MCI groups; QTM velocity, but not CBF, showed a significant difference between MCI and NC groups. QTM velocity and CBF showed values decreasing with age; QTM velocity, but not CBF, showed a significant gender difference between male and female. QTM velocity and CBF in the hippocampus were positively correlated with cognition, including global cognition, memory, executive function, and language function.ConclusionThis study demonstrated an increased sensitivity of QTM velocity as compared with the traditional Kety’s method-based CBF. Specifically, we observed only in QTM velocity, reduced perfusion velocity in GM and the hippocampus in MCI compared with NC. Both QTM velocity and CBF demonstrated a reduction in AD vs. controls. Decreased QTM velocity and CBF in the hippocampus were correlated with poor cognitive measures. These findings suggest QTM velocity as potential biomarker for early AD blood perfusion alterations and it could provide an avenue for early intervention of AD.

Method for measuring blood flow and depth of blood vessel based on laser speckle contrast imaging using 3D convolutional neural network: A preliminary study

Laser speckle contrast imaging (LSCI) is a technology that can acquire real-time two-dimensional perfusion images non-invasively. However, measuring perfusion velocity under a tissue is difficult due to its optical properties. Dynamic scattered light occurs by perfusion is diffused by the surrounding tissue and it depends on the depth of tissue. We aimed to develop a three-dimensional convolutional neural network (3D-CNN) model based on laser speckle contrast images to measure the flow velocity and the depth of tissue using a flow phantom. The training data was selected as a region containing both static speckles and dynamic speckles, and the model was trained on the laser speckle contrast image data. The trained model showed a measurement accuracy of more than 90 % for velocity and 99 % for depth measurement. This study has the potential of a deep-learning model based on LSCI to analyze the blood flow and depth of blood vessels in bio-applications.

Strain- and sex-specific differences in intestinal microhemodynamics and gut microbiota composition.

Intestinal microcirculation is a critical interface for nutrient exchange and energy transfer, and is essential for maintaining physiological integrity. Our study aimed to elucidate the relationships among intestinal microhemodynamics, genetic background, sex, and microbial composition. To dissect the microhemodynamic landscape of the BALB/c, C57BL/6J, and KM mouse strains, laser Doppler flowmetry paired with wavelet transform analysis was utilized to determine the amplitude of characteristic oscillatory patterns. Microbial consortia were profiled using 16S rRNA gene sequencing. To augment our investigation, a broad-spectrum antibiotic regimen was administered to these strains to evaluate the impact of gut microbiota depletion on intestinal microhemodynamics. Immunohistochemical analyses were used to quantify platelet endothelial cell adhesion molecule-1 (PECAM-1), estrogen receptor α (ESR1), and estrogen receptor β (ESR2) expression. Our findings revealed strain-dependent and sex-related disparities in microhemodynamic profiles and characteristic oscillatory behaviors. Significant differences in the gut microbiota contingent upon sex and genetic lineage were observed, with correlational analyses indicating an influence of the microbiota on microhemodynamic parameters. Following antibiotic treatment, distinct changes in blood perfusion levels and velocities were observed, including a reduction in female C57BL/6J mice and a general decrease in perfusion velocity. Enhanced erythrocyte aggregation and modulated endothelial function post-antibiotic treatment indicated that a systemic response to microbiota depletion impacted cardiac amplitude. Immunohistochemical data revealed strain-specific and sex-specific PECAM-1 and ESR1 expression patterns that aligned with observed intestinal microhemodynamic changes. This study highlights the influence of both genetic and sex-specific factors on intestinal microhemodynamics and the gut microbiota in mice. These findings also emphasize a substantial correlation between intestinal microhemodynamics and the compositional dynamics of the gut bacterial community.

Ultrasound assessment is useful for evaluating balloon volume of resuscitative endovascular balloon occlusion of the aorta.

Endovascular balloon occlusion of the aorta (EBOA) increases proximal arterial pressure but may also induce life-threatening ischemic complications. Although partial REBOA (P-REBOA) mitigates distal ischemia, it requires invasive monitoring of femoral artery pressure for titration. In this study, we aimed to titrate P-REBOA to prevent high-degree P-REBOA using ultrasound assessment of femoral arterial flow. Proximal (carotid) and distal (femoral) arterial pressures were recorded, and perfusion velocity of distal arterial pressures was measured by pulse wave Doppler. Systolic and diastolic peak velocities were measured among all ten pigs. Total REBOA was defined as a cessation of distal pulse pressure, and maximum balloon volume was documented. The balloon volume (BV) was titrated at 20% increments of maximum capacity to adjust the degree of P-REBOA. The distal/proximal arterial pressure gradient and the perfusion velocity of distal arterial pressures were recorded. Proximal blood pressure increased with increasing BV. Distal pressure decreased with increasing BV, and distal pressure sharply decreased by > 80% of BV. Both systolic and diastolic velocities of the distal arterial pressure decreased with increasing BV. Diastolic velocity could not be recorded when the BV of REBOA was > 80%. The diastolic peak velocity in the femoral artery disappeared when %BV was > 80%. Evaluation of the femoral artery pressure by pulse wave Doppler may predict the degree of P-REBOA without invasive arterial monitoring.

Super-Resolution Ultrasound Localization Microscopy Using High-Frequency Ultrasound to Measure Ocular Perfusion Velocity in the Rat Eye.

Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify the perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.

Phenotyping the sheep tail - Presentation of characterization methods in the context of breeding for short-tailedness

In order to establish targeted breeding for short-tailedness, a suitable method must initially be found that allows phenotyping of the sheep tail beyond tail length. In this study, in addition to assessing body measurements, more advanced studies such as ultrasonography and radiology were performed on the caudal spine of sheep for the first time. The objective of this work was to analyze the physiological variation of tail lengths and vertebrae within a merino sheep population. It also aimed to validate the use of sonographic gray scale analysis and perfusion measurement on the sheep tail. Tail length and circumference in centimeters were measured in 256 Merino lambs on the first or second day of life. At 14 weeks of age the caudal spine of these animals was examined radiographically. Sonographic gray scale analysis and measurement of the perfusion velocity of the caudal artery mediana were also performed in a portion of the animals. The tested method of measurement showed a standard error of 0,08 cm and a coefficient of variation of 0,23% for tail length and 0,78% for tail circumference. The animals had a mean tail length of 22,5±2,32 cm and a mean tail circumference of 6,53±0,49 cm. The mean caudal vertebrae count for this population was 20,4±1,6. The use of a mobile radiographic unit is well suited for imaging the caudal spine in sheep. It was demonstrated that the caudal median artery could be imaged for measurement of perfusion velocity (cm/s), and sonographic gray-scale analysis also showed good feasibility. The mean gray scale value is 19,74±4,5 and the modal value for the most commonly found gray scale pixels is 191,53±120,2. The mean perfusion velocity for the caudal artery mediana is 5,83±3,04 cm/s. The results show that the methods presented are well suited for further characterization of the ovine tail. For the first time, gray values for the tail tissue and the perfusion velocity of the caudal artery mediana were determined.

Lower Limb Dynamic Activity Significantly Reduces Foot Skin Perfusion: Exploring Data with Different Optical Sensors in Age-Grouped Healthy Adults

Introduction: The human lower limb is widely used as a model to study in vivo microcirculatory physiology and pathophysiology. It is a preferential target for critical comorbidities (overweight, diabetes, and peripheral vascular disease). Movement and activity are consistently regarded as beneficial, but the related adaptive physiology is still poorly understood. Our goal was to better identify the foot microcirculatory changes after a regular walking gait activity in healthy subjects of different ages. Methods: Twelve healthy participants of both sexes, with normal BMI and Ankle-Brachial Index, were selected and grouped according to age – group I (21.0 ± 1 y.o.) and group II (55.8 ± 3 y.o.). The protocol involved 2 phases of 5-min duration each – phase 1, a static standing position, and phase 2, 5-min walking with a comfortable pace on a pre-established circuit. Perfusion changes were assessed in the dorsal region of both feet before (baseline, phase 1) and after (phase 2) the gait period by noninvasive optical technologies – laser Doppler flowmetry (LDF), photoplethysmography, and polarized spectroscopy (PSp). Comparative statistics were performed with a 95% confidence level. Results: All instruments detected an asymmetric nonsignificant perfusion between right and left feet during rest in all participants with values in females consistently lower than men. Older participants exhibited lower baseline values than the younger group. Gait evoked a perfusion reduction in all participants relative to phase 1 detected with all technologies, with statistically significant changes recorded with LDF (group I, p = 0.033, and group II, p = 0.028) and PSp (group II, p = 0.041). Furthermore, LDF revealed that gait significantly reduced perfusion velocity in the older group (p = 0.003). Corresponding changes in the younger group were present but discrete. Recovery to baseline levels was also slower in the older group. Discussion/Conclusions: Our results confirm that perfusion is age dependent and demonstrate the clinical relevance of simple dynamic activities such as gait. This reduction of the dorsal foot perfusion occurs in depth, being more pronounced with the movement intensity, suggesting a wide application potential in early diagnostics as for rehabilitation.

The restorative effect of apocynin and catalase in l-arginine induced hypotension on normotensive subjects - the role of oxidative stress.

L-arginine is a substrate for nitric oxide synthase (NOS) responsible for the production of NO. This investigation studied the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on L-arginine induced oxidative stress and hypotension. Forty Wistar-Kyoto rats were treated for 14 days with vehicle, L-arginine (12.5mg/ml p.o.), L-arginine+apocynin (2.5mmol/L p.o.), L-arginine+catalase (10000U/kg/day i.p.) and L-arginine plus apocynin+catalase respectively. Weekly renal functional and hemodynamic parameters were measured and kidneys harvested at the end of the study for histopathological and renal NADPH oxidase 4 (Nox4) assessments. L-arginine administration in normotensive rats decreased systolic blood pressure (120±2 vs 91±2mmHg) and heart rate (298±21 vs 254±15b/min), enhanced urinary output (21.5±4.2 vs 32±1.9ml/24h , increased creatinine clearance (1.72±0.56 vs 2.62±0.40ml/min/kg), and fractional sodium excretion (0.88±0.16 vs 1.18±0.16 %), caused proteinuria (28.10±1.93 vs 35.26±1.69mg/kg/day) and a significant decrease in renal cortical blood perfusion (292±3 vs 258±5bpu) and pulse wave velocity (3.72±0.20 vs 2.84±0.13m/s) (all P<0.05). L-arginine increased plasma malondialdehyde (by ~206 % P<0.05) and NO (by~51 %, P<0.05) but decreased superoxide dismutase (by~31 %, P<0.05) and total antioxidant capacity (by~35 %, P<0.05) compared to control. Renal Nox4 mRNA activity was approximately 2.1 fold higher (P<0.05) in the L-arginine treated rats but was normalized by apocynin and apocynin plus catalase treatment. Administration of apocynin and catalase, but not catalase alone to rats fed L-arginine, restored the deranged renal function and structure, prevented hypotension and enhanced the antioxidant capacity and suppressed Nox4 expression. These findings suggest that apocynin and catalase might be used prophylactically in states of oxidative stress.

Modeling the impact of fluid flow on resveratrol release from electrospun fibers

Using electrospun fibers to deliver therapeutic agents has gained significant attention in various applications including cancer treatment and tissue regeneration. However, the effect of fluid flow and uptake by cells on the concentration profile is not well understood. In this study, we evaluated the release of lipophilic resveratrol from poly(ε-caprolactone) (PCL)-gelatin (GT) electrospun fibers experimentally and by using computational fluid dynamics (CFD). Resveratrol containing PCL-GT electrospun fibers were formed and used in a custom-built tubular bioreactor, to assess flow effect on concentration profile over 5 days. CFD model was developed to simulate release in both static cultures and under fluid flow conditions. Resveratrol stability in the culture medium and uptake by human umbilical vein endothelial cells and K562 cells over 3 days were used in the model. The concentration profile as a function of time was simulated and validated by experiments. The effects of inlet velocity, cellular uptake rate, bioreactor's length, and surrounding tissue porosity were assessed. The release profile was mainly affected by cellular uptake and the presence of porous media. The model suggests that the perfusion velocity might not have a significant effect relative to the cellular uptake rate and porosity of the surrounding tissue.

TMOD-07. IN SITU MICROSCOPY OF DRUG AND IMMUNE CELL INTERACTIONS AGAINST BIOFABRICATED TUMOR MODELS

Abstract BACKGROUND &amp; SIGNIFICANCE Cancer is a disease in 3-dimensions and there is a desperate need for infrastructure and models to study immuno-oncology treatment strategies in 3D. A new culture system for long-duration maturation of patient derived microtumors has been developed. This system enables in situconfocal imaging and movies of T-cells and tumor model interactions, including measurements of T-cell migration, infiltration, and killing. HYPOTHESIS: Biofabrication of 3D microtumors using bioprinting in transparent soft granular gel media can facilitate the precise arrangement and stability of extra-cellular matrix components, tumor, and immune cells while maintaining continuous liquid perfusion. METHODS The design, development, and validation of a modular negative pressure perfusion system controls the transport of liquid growth medium, drugs, antibodies, growth factors, and metabolic waste management in 3D. In situ confocal fluorescent microscopy measures cell positions, velocities, and viability during experiments. Steady perfusion velocities are controlled through negative pressure, and velocities from 1–100 nm/s can be achieved. RESULTS Cell motility, adhesion, and dynamic rearrangement of fibroblasts and endothelial cells within a 3D co-culture of microtumors evolved dramatically over the first 72 hours. Tracking of activated CD8+ T-cells revealed super-diffusive motion in the presence of 3D tumors with a range of 250 µm. Activated T-cell migration speeds have been measured to be between 1.3–2.0 um/min in the 3D media, and preliminary estimates of T cell migration forces are on the order of 1 nN. Arrival of CD8+ T-cells to the tumors within the first 30 minutes revealed cell killing which continued for over 3-hours and resulted in a 2-fold reduction in tumor cell numbers. CONCLUSIONS This integrated system of 3D bioprinting, perfusion culture plates, and confocal microscopy enables in situ3D studies of cancer biology, immunotherapy, and drug treatment regimens and provides unique insights and measurements of immune cell invasion dynamics in 3D microtumors.

Abstract 35: 3D in vitro system for immuno-oncology: Real-time imaging of drug delivery, tumoroids, and immune cell activity

Abstract A Liquid Like Solid (LLS) 3D culture system in a convenient microtiter plate format enables long-duration culture of patient derived microtumors (&amp;gt;30 days), in situ confocal imaging, 3D cytotoxic drug studies, inclusion of T cells, and measurements of T cell migration, infiltration, and killing. Introduction: Cancer is a disease in 3-dimensions and there is a desperate need for new tools and infrastructure to study immuno-oncology treatment methods in 3D. Fabrication of microtumors using 3D printing in LLS media comprised of soft granular microgels (3-5 μm crosslinked polyacrylamide (PAA) microgel particles: 7.5% PAA) facilitate precise arrangement of detailed assemblies of extra-cellular matrix components and cells (1), including: epithelial cells (breast ATCC MCF10A), stem cells (bone marrow MSC), cancer cells (breast ATCC MCF7, prostate ATCC-PC3, osteosarcoma ATCC-MG63, melanoma ATCC-A375, primary glioblastoma, and osteosarcoma), fibroblasts (ThermoFisher dermal fibroblasts C0045C), endothelial cells (ThermoFisher HUVECs C0035C), and CD4+/CD8+ T cells (PBMC and Jurkat E6-1). Methods: Long term culture was enabled through the design, development, and validation of a modular perfusion system that uses passive negative pressure within a 96-well microtiter plate format to transport liquid growth medium, drugs (doxorubicin and puromycin), antibodies (aPD1 J43 clone, aCD3, aCD28), growth factors, FBS, and metabolic waste without disturbing the spatial organization and positioning of the experiments (i.e. 3D orientation is preserved and the packed bed of microgel particles remain solid). The perfusion velocities are precisely controlled to between 1-100 nm/s by setting the negative pressure, and complete exchange of liquid media can be tailored from hours to days. Results: Real-time imaging in these 3D assays is performed using in situ confocal microscopy under controlled perfusion. Cell motility, adhesion, and dynamic rearrangement of fibroblasts and endothelial cells within a 3D co-culture of microtumors evolved over the first 72 hours. Immunohistochemistry with Ki-67 and PCNA staining indicated active cell proliferation of the tumoroids after 28 days of continuous culture. Tracking of activated CD8+ T cells revealed super-diffusive motion in the presence of 3D tumors within a range of 250 µm. Activated T cell migration speeds have been measured to be between 1.3 and 2.0 μm/s in the 3D LLS media, and preliminary estimates of T cell migration forces are on the order of 1 nN. Conclusions: This integrated system of 3D bioprinting, perfusion culture plates, and confocal microscopy enables in situ 3D studies of cancer biology, immunotherapy, and drug treatment regimens and provides unique insights and measurements of immune cell invasion dynamics in 3D microtumors.

Quantitative Measurement of Polar-Molecule Perfusion for Tumor Detection by Thermoacoustic Doppler Ultrasound Dual-Modality Imaging

The authors propose a method for determining the supply of nutrient molecules in the body, and establish a dual-modality imaging system to realize this method. In their approach, thermoacoustic imaging reveals the density of nutrient molecules (which are not visible to conventional techniques), while Doppler ultrasound imaging shows the velocity of blood flow. Combining these results, one can obtain the nutritional perfusion velocity, and thus the nutritional supply level of living tissue, which can be an indicator for tumor detection.

This issue of Acta

This issue of Acta

A Perfusion Bioreactor System for Cell Seeding and Oxygen-Controlled Cultivation of Three-Dimensional Cell Cultures.

Bioreactor systems facilitate three-dimensional (3D) cell culture by coping with limitations of static cultivation techniques. To allow for the investigation of proper cultivation conditions and the reproducible generation of tissue-engineered grafts, a bioreactor system, which comprises the control of crucial cultivation parameters in independent-operating parallel bioreactors, is beneficial. Furthermore, the use of a bioreactor as an automated cell seeding tool enables even cell distributions on stable scaffolds. In this study, we developed a perfusion microbioreactor system, which enables the cultivation of 3D cell cultures in an oxygen-controlled environment in up to four independent-operating bioreactors. Therefore, perfusion microbioreactors were designed with the help of computer-aided design, and manufactured using the 3D printing technologies stereolithography and fused deposition modeling. A uniform flow distribution in the microbioreactor was shown using a computational fluid dynamics model. For oxygen measurements, microsensors were integrated in the bioreactors to measure the oxygen concentration (OC) in the geometric center of the 3D cell cultures. To control the OC in each bioreactor independently, an automated feedback loop was developed, which adjusts the perfusion velocity according to the oxygen sensor signal. Furthermore, an automated cell seeding protocol was implemented to facilitate the even distribution of cells within a stable scaffold in a reproducible way. As proof of concept, the human mesenchymal stem cell line SCP-1 was seeded on bovine cancellous bone matrix of 1 cm3 and cultivated in the developed microbioreactor system at different oxygen levels. The oxygen control was capable to maintain preset oxygen levels ±0.5% over a cultivation period of several days. Using the automated cell seeding procedure resulted in evenly distributed cells within a stable scaffold. In summary, the developed microbioreactor system enables the cultivation of 3D cell cultures in an automated and thus reproducible way by providing up to four independently operating, oxygen-controlled bioreactors. In combination with the automated cell seeding procedure, the bioreactor system opens up new possibilities to conduct more reproducible experiments to investigate optimal cultivation parameters and to generate tissue-engineering grafts in an oxygen-controlled environment.

Short-term external counterpulsation augments cerebral blood flow and tissue oxygenation in chronic cerebrovascular occlusive disease.

Background and purposeExternal counterpulsation improves cerebral perfusion velocity in acute stroke and may stimulate collateral artery growth. However, whether (non‐acute) at‐risk patients with high‐grade carotid artery disease may benefit from counterpulsation needs to be validated.MethodsTwenty‐eight patients (71 ± 6.5 years, five women) with asymptomatic unilateral chronic severe internal carotid artery stenosis (>70%) or occlusion were randomized to receive 20 min active counterpulsation followed by sham treatment or vice versa. Cerebral blood flow velocity (CBFV) (measured bilaterally by transcranial middle cerebral artery Doppler), tissue oxygenation index (TOI) (measured over the bilateral prefrontal cortex by near‐infrared spectroscopy) and cerebral hemodynamic parameters, such as relative pulse slope index (RPSI), were monitored.ResultsIpsilateral mean CBFV (ΔV mean +3.5 ± 1.2 cm/s) and tissue oxygenation (ΔTOI +2.86 ± 0.8) increased significantly during active counterpulsation compared to baseline, whilst the sham had little effect (ΔV mean +1.13 ± 1.1 cm/s; ΔTOI +1.25 ± 0.65). On contralateral sides, neither counterpulsation nor sham control had any effect on either parameter. During counterpulsation, early dynamic changes in ΔRPSI of the ipsilateral CBFV signal predicted improved tissue oxygenation during counterpulsation (odds ratio 1.179, 95% confidence interval 1.01–1.51), whilst baseline cerebrovascular reactivity to hypercapnia failed to show an association.ConclusionsIn patients with high‐grade carotid disease, ipsilateral cerebral oxygenation and blood flow velocity are increased by counterpulsation. This is a necessary condition for the stimulation of regenerative collateral artery growth and thus a therapeutic concept for the prevention of cerebral ischaemia. This study provides a rationale for further clinical investigations on the long‐term effects of counterpulsation on cerebral hemodynamics and collateral growth.

Effect of percutaneous nephrolithotomy on stone removal and complications in patients with renal calculi under low velocity perfusion.

Objective To investigate the effect of percutaneous nephrolithotomy (PCNL) on stone removal and complications in patients with renal calculi under low velocity perfusion. Methods A retrospective analysis was used to select 90 patients with renal calculi in the People′s Hospital of Kaizhou District of chongqing from January 2015 to June 2017. The patients were divided into control group and study group in random double-blind method, with 45 cases in each group. The control group was treated with high speed perfusion of PCNL, and the study group was treated with low speed perfusion of PCNL, and the operating time, blood loss, stone clearance rate, incidence of complications, percentage of neutrophil and shock index were compared with the two groups. Measurement data were expressed by (±s). t test was used to compare with the two groups. Counting data were expressed in percentage (%), and Chi-square test was used to compare wth the two groups. Results There was no significant difference in the treatment effect of the two groups, including operating time, blood loss, stone clearance rate (the P values were 0.392 4, 0.446 1, and 0.693 9, respectively). The incidence of complications in the study group was significantly lower than that in the control group (31.09% vs 53.31%, χ2=5.408 6, P=0.020 0), and the incidence of infectious diseases was much lower than that in the control group(17.78% vs 40.00%). After treatment, the percentage of neutrophil and shock index in the study group was lower than those in the control group. Conclusion Low rate perfusion of PCNL has less negative effect on the effect of stone removal in patients with renal calculi, and it also reduces the incidence of complications and is worth promoting in clinical practice. Key words: Nephrostomy, percutaneous; Kidney calculi; Postoperative complications; Low velocity

Perfusion double-channel micropipette probes for oxygen flux mapping with single-cell resolution.

Measuring cellular respiration with single-cell spatial resolution is a significant challenge, even with modern tools and techniques. Here, a double-channel micropipette is proposed and investigated as a probe to achieve this goal by sampling fluid near the point of interest. A finite element model (FEM) of this perfusion probe is validated by comparing simulation results with experimental results of hydrodynamically confined fluorescent molecule diffusion. The FEM is then used to investigate the dependence of the oxygen concentration variation and the measurement signal on system parameters, including the pipette’s shape, perfusion velocity, position of the oxygen sensors within the pipette, and proximity of the pipette to the substrate. The work demonstrates that the use of perfusion double-barrel micropipette probes enables the detection of oxygen consumption signals with micrometer spatial resolution, while amplifying the signal, as compared to sensors without the perfusion system. In certain flow velocity ranges (depending on pipette geometry and configuration), the perfusion flow increases oxygen concentration gradients formed due to cellular oxygen consumption. An optimal perfusion velocity for respiratory measurements on single cells can be determined for different system parameters (e.g., proximity of the pipette to the substrate). The optimum perfusion velocities calculated in this paper range from 1.9 to 12.5 μm/s. Finally, the FEM model is used to show that the spatial resolution of the probe may be varied by adjusting the pipette tip diameter, which may allow oxygen consumption mapping of cells within tissue, as well as individual cells at subcellular resolution.

Estimating Retinal Blood Flow Velocities by Optical Coherence Tomography.

While optical coherence tomography (OCT) angiography has been considered to evaluate retinal capillary blood flow instead of fluorescein angiography, the reflectance pattern of blood vessels on structural OCT might also provide retinal capillary flow data in the absence of fluorescein angiography. This potential has been insufficiently explored, despite promising data concerning a possible relationship between the reflectance pattern of blood vessels and their perfusion velocity in a laboratory setting. To evaluate the potential of retinal blood flow velocity estimation by structural OCT. Cross-sectional observational study conducted from June to November 2015 at a tertiary clinical referral center. Sixty arteries (the superior and inferior temporal arteries) from 30 eyes of 30 patients (17 female, 13 male) were included in the study. Based on the intraluminal contrast patterns of retinal arteries on OCT, 3 independent graders categorized the blood flow velocities as low, medium, or high. These results and the results from a software-based intraluminal contrast analysis were compared with the retinal blood flow velocities measured by video fluorescein angiography. Among the 30 eyes of 30 patients (mean [SD] age, 72.6 [12.3] years; 17 female, 13 male), 15 were controls without retinal occlusion, 6 had a branch retinal artery occlusion, and 9 had a central retinal artery occlusion. When discriminating between low flow velocities and medium or high flow velocities, the graders' sensitivity ranged from 88.2% to 100% (grader 1: 88.2%; 95% CI, 63.6%-98.5%; grader 2: 88.2%; 95% CI, 63.6%-98.5%; and grader 3: 100%; 95% CI, 69.8%-100%) and their specificity ranged from 97.6% to 100% (grader 1: 100%; 95% CI, 87.7%-100%; grader 2: 97.6%; 95% CI, 87.4%-99.9%; and grader 3: 100%; 95% CI, 87.7%-100%). The κ coefficients of the comparison between the 3 graders and the angiography were 0.77 (95% CI, 0.60-0.93; P < .001), 0.64 (95% CI, 0.44-0.83; P < .001), and 0.87 (95% CI, 0.74-0.99; P < .001). In the computer-based assessment, the contrast reduction of the intraluminal pattern could be numerically expressed in a specific coefficient in the model (I2, describing the angular change of the backscattering intensity in the model), which presented nonoverlapping intervals between low flow velocities and medium or high flow velocities (mean [SD] I2, 0.3 [5.3], 20.4 [6.4], and 21.7 [4.0], respectively). This study suggests that a low retinal blood flow velocity reflects in a visually distinct contrast reduction of the intraluminal pattern of retinal vessels on OCT. Larger studies are required to assess the clinical benefits.

Retinal characteristics during 1year of insulin pump therapy in type 1 diabetes: a prospective, controlled, observational study.

To investigate changes in retinal metabolism, function, structure and morphology in relation to initiation of insulin pump therapy (continuous subcutaneous insulin infusion, CSII). Visual acuity, retinopathy level, dark adaptation kinetics, retinal and subfoveal choroidal thickness, macular perfusion velocities, retinal vessel diameters and blood oxygen saturations were measured at baseline and after 1, 4, 16, 32 and 52weeks in 31 patients with type 1 diabetes who startedCSII and 20 patients who continued multiple daily insulin injections (MDI). One year of CSII reduced haemoglobin A1c (HbA1c ) by 1.6% (17.8mmol/mol) compared with 0.3% (3.1mmol/mol) in the MDI group (p<0.0001). Central retinal thickness increased by 1.5% in the CSII group (within-group p=0.0098; between-group p=0.063) without producing macular oedema. No detectable change was found in any other primary outcome measure. The proportion of patients with retinopathy worsening did not differ between groups. At baseline, longer disease duration was associated with higher retinal artery oxygen saturation (p=0.014) and lower macular venous perfusion velocity (p=0.045). One year of CSII led to an HbA1c reduction relative to continued MDI and a small increase in retinal thickness but not to early retinopathy worsening or to changes in retinal vascular, structural or functional characteristics. Longer duration of type 1 diabetes appears to be associated with lower macular venous perfusion velocity and higher retinal artery oxygen saturation. The latter could potentially reflect cumulative glycaemia.

A New Fluidized Bed Bioreactor Based on Diversion-Type Microcapsule Suspension for Bioartificial Liver Systems.

A fluidized bed bioreactor containing encapsulated hepatocytes may be a valuable alternative to a hollow fiber bioreactor for achieving the improved mass transfer and scale-up potential necessary for clinical use. However, a conventional fluidized bed bioreactor (FBB) operating under high perfusion velocity is incapable of providing the desired performance due to the resulting damage to cell-containing microcapsules and large void volume. In this study, we developed a novel diversion-type microcapsule-suspension fluidized bed bioreactor (DMFBB). The void volume in the bioreactor and stability of alginate/chitosan microcapsules were investigated under different flow rates. Cell viability, synthesis and metabolism functions, and expression of metabolizing enzymes at transcriptional levels in an encapsulated hepatocyte line (C3A cells) were determined. The void volume was significantly less in the novel bioreactor than in the conventional FBB. In addition, the microcapsules were less damaged in the DMFBB during the fluidization process as reflected by the results for microcapsule retention rates, swelling, and breakage. Encapsulated C3A cells exhibited greater viability and CYP1A2 and CYP3A4 activity in the DMFBB than in the FBB, although the increases in albumin and urea synthesis were less prominent. The transcription levels of several CYP450-related genes and an albumin-related gene were dramatically greater in cells in the DMFBB than in those in the FBB. Taken together, our results suggest that the DMFBB is a promising alternative for the design of a bioartificial liver system based on a fluidized bed bioreactor with encapsulated hepatocytes for treating patients with acute hepatic failure or other severe liver diseases.