IntroductionX-ray Velocimetry (XV) ventilation analysis is a 4-dimensional imaging-based method for quantifying regional ventilation, aiding in the assessment of lung function. We examined the performance characteristics of XV ventilation analysis by examining correlation to spirometry and measurement repeatability. MethodsXV analysis was assessed in 27 patients receiving thoracic radiotherapy for non-lung cancer malignancies. Measurements were obtained pre-treatment and at 4 and 12-months post-treatment. XV metrics such as ventilation defect percent (VDP) and regional ventilation heterogeneity (VH) were compared to spirometry at each time point, using correlation analysis. Repeatability was assessed between multiple runs of the analysis algorithm, as well as between multiple breaths in the same patient. Change in VH and VDP in a case series over 12 months was used to determine effect size and estimate sample sizes for future studies. ResultsVDP and VH were found to significantly correlate with FEV1 and FEV1/FVC (range: -0.36 to -0.57; p < 0.05). Repeatability tests demonstrated that VDP and VH had less than 2% variability within runs and less than 8% change in metrics between breaths. Three cases were used to illustrate the advantage of XV over spirometry, where XV indicated a change in lung function that was either undetectable or delayed in detection by spirometry. Case A demonstrated an improvement in XV metrics over time despite stable spirometric values. Case B demonstrated a decline in XV metrics as early as 4-months, although spirometric values did not change until 12-months. Case C demonstrated a decline in XV metrics at 12 months post-treatment while spirometric values remained normal throughout the study. Based on the effect sizes in each case, sample sizes ranging from 10 to 38 patients would provide 90% power for future studies aiming to detect similar changes. ConclusionsThe performance and safety of XV analysis make it ideal for both clinical and research applications across most lung indications. Our results support continued research and provide a basis for powering future studies using XV as an endpoint to examine lung health and determine therapeutic efficacy.

SESSION TITLE: Imaging Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Radiation pneumonitis (RP) is lung inflammation induced by the high-dose radiation associated with thoracic radiotherapy. Severe or chronic RP can cause permanent lung damage, therefore early diagnosis is vital. Global pulmonary function tests (PFTs) such as diffusing capacity of the lung for carbon monoxide (DLCO) are the primary diagnostics for RP. However, regional function measurements may provide additional sensitivity, enabling earlier detection. Here we assessed X-ray Velocimetry (XV), a unique 4D imaging method that quantifies spatial ventilation distribution throughout the breath. Using XV Technology we compared local radiation dose with changes in ventilation at over 10,000 locations within the lung. METHODS: Lung function of patients receiving radiotherapy for various thoracic cancers (NCT02735746) was assessed using XV Technology and global PFT measurements. Patient data was acquired pre-treatment and at 4- and 12-months post-treatment. XV-derived ventilation data was co-registered to the regional dose distribution planning map. This allowed direct comparison of local radiation dose with corresponding changes in ventilation. DLCO, adjusted for blood hemoglobin concentration (DLCO-adj), was measured at every timepoint. RESULTS: Several patients exhibited considerable changes in regional ventilation throughout the study. In some cases, these changes were related to the local dose, while in other cases they were not. In one case, ventilation heterogeneity (VH) increased from 59% pre-treatment to 67% 4-months post-treatment, indicating declining lung function. However, local changes in ventilation were independent of radiation dose. DLCO-adj was stable throughout the study, suggesting this patient did not develop RP. Conversely, another case demonstrated a clear relationship between dose and function. This patient had considerable VH before treatment (49%) which further increased post-treatment (VH=68%). Notably, for this patient areas that received higher dose had greater decreases in ventilation after 12 months. DLCO-adj dropped from 61% to 46% expected, suggesting the increased VH could be related to the development of RP. CONCLUSIONS: XV regional ventilation measurements offer superior sensitivity, as demonstrated by their use for detecting both radiation-independent and radiation-dependent changes in lung function. Further, XV has the advantage over PFT of being able to target specific regions where high dose is administered. CLINICAL IMPLICATIONS: One of the many potential applications for XV is monitoring patient lung response to radiation therapy. Specifically, XV monitoring could enable earlier detection of declining lung function in response to therapy, leading to earlier treatment and improved prognosis. DISCLOSURES: No relevant relationships by John DeMarco, source=Web Response Employee relationship with 4Dx Please note: $20001 - $100000 Added 05/29/2020 by Chandni Doshi, source=Web Response, value=Salary Employee relationship with 4DMedical Please note: >$100000 Added 05/29/2020 by Jonathan Dusting, source=Web Response, value=Salary Employee relationship with 4DMedical Please note: >$100000 Added 06/01/2020 by Andreas Fouras, source=Web Response, value=Salary Owner/Founder relationship with 4DMedical Please note: >$100000 Added 06/01/2020 by Andreas Fouras, source=Web Response, value=Ownership interest No relevant relationships by Cynthia Martin, source=Web Response No relevant relationships by Stephen Shiao, source=Web Response Employee relationship with 4DMedical Please note: $20001 - $100000 Added 05/27/2020 by Olivia Stephens, source=Web Response, value=Salary 4DMedical Clinical Development relationship with 4DMedical Please note: >$100000 Added 05/29/2020 by Neeraj Vij, source=Web Response, value=CRO service fees Employee relationship with 4DMedical Please note: $20001 - $100000 Added 06/01/2020 by David Wenger, source=Web Response, value=Salary

SESSION TITLE: Imaging Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: X-ray Velocimetry (XV) is a powerful 4D imaging-based method for quantifying regional ventilation, aiding in the assessment of lung function. Developed through extensive preclinical research, XV has recently been validated in a first-in-human study. Here, we report on the comparison of XV to spirometry and computed tomography (CT) through global correlations and case studies. METHODS: XV Technology was assessed in a clinical trial to monitor changes in lung function in patients receiving radiotherapy for various thoracic cancers (NCT02735746). Patient data were obtained at screening, treatment initiation, and 4 and 12-months post-treatment. Repeatability tests confirmed reproducibility of the analysis. XV metrics such as ventilation defect percent (VDP) and regional ventilation heterogeneity (VH) were compared to pulmonary function tests (PFT) and CT at each time-point. Ventilation histograms and spatial distributions were analyzed at each time-point, enabling monitoring of subtle changes in lung function. RESULTS: Overall, VDP and VH significantly correlated with FEV1 and FEV1/FVC (p<0.05). Additionally, several cases illustrated the advantage of XV over PFT and CT. Here we show two cases where patients had normal PFTs which were stable throughout the study. However, XV analysis showed regional lung function varied over time. In one case, FEV1 and FVC were >100% expected and CT showed mostly clear lungs pre-treatment. However, VDP and VH were well above baseline (15% and 55%, respectively) suggesting functional abnormalities. At 12-months post-treatment, XV metrics had improved (VDP=9% and VH=37%), while PFTs remained stable. Conversely, in another patient, pre-treatment CT could not rule out airway or interstitial disease however VDP and VH were relatively low (10% and 39%, respectively). At 12-months post-treatment, VDP and VH had increased to 13% and 53%, respectively, despite no change in PFTs. Further, regional ventilation maps demonstrated increased specific ventilation in the right lung compared to the left at 12-months, suggesting compensation in the right lung masked dysfunction in PFTs. CONCLUSIONS: XV analysis provided rich lung function information, revealing local variations in ventilation related to dysfunction and compensation that were not identified via PFT or CT. CLINICAL IMPLICATIONS: While XV metrics are consistent overall with gold-standard diagnostics, they offer superior sensitivity, providing considerable value to clinicians and researchers. The enhanced sensitivity associated with XV regional ventilation analysis promises to be invaluable for detecting, monitoring, and treating early stage disease. DISCLOSURES: No relevant relationships by John DeMarco, source=Web Response Employee relationship with 4Dx Please note: $20001 - $100000 Added 05/29/2020 by Chandni Doshi, source=Web Response, value=Salary Employee relationship with 4DMedical Please note: >$100000 Added 05/29/2020 by Jonathan Dusting, source=Web Response, value=Salary Employee relationship with 4DMedical Please note: >$100000 Added 06/01/2020 by Andreas Fouras, source=Web Response, value=Salary Owner/Founder relationship with 4DMedical Please note: >$100000 Added 06/01/2020 by Andreas Fouras, source=Web Response, value=Ownership interest No relevant relationships by Cynthia Martin, source=Web Response No relevant relationships by Stephen Shiao, source=Web Response Employee relationship with 4DMedical Please note: $20001 - $100000 Added 05/27/2020 by Olivia Stephens, source=Web Response, value=Salary 4DMedical Clinical Development relationship with 4DMedical Please note: >$100000 Added 05/29/2020 by Neeraj Vij, source=Web Response, value=CRO service fees Employee relationship with 4DMedical Please note: $20001 - $100000 Added 06/01/2020 by David Wenger, source=Web Response, value=Salary

SESSION TITLE: Late Breaking Pulmonary Fibrosis SESSION TYPE: Original Investigations PRESENTED ON: 10/22/2019 08:45 AM - 09:45 AM PURPOSE: Quantification of small changes in lung function is necessary for early diagnosis and intervention in chronic lung diseases. Pneumonitis is a frequent complication of lung radiation that currently has no known therapy and can only be diagnosed late when it manifests changes in the pulmonary function tests (PFT). Unlike existing PFT, X-ray Velocimetry (XV) technology uniquely measures 4D lung motion to quantify regional lung function with high resolution and accuracy providing a novel diagnostic tool for early assessment of risk of radiation induced pneumonitis and/or pulmonary fibrosis. METHODS: This study was primarily designed to assess the performance of XV technology in comparison to other clinically available measures (spirometry, CT) in diagnosing radiation pneumonitis. Patients with a predicted risk for pneumonitis of 25% (V20 Gy>20%) were consented and enrolled in this study. In order to test the capacity of XV to detect changes in lung function over time, XV-scans were acquired pre-treatment, weekly on treatment and at 4-months and 12-months following treatment in combination with PFTs, and/or 4DCT or CT. RESULTS: Compared to PFT, the tidal volume and ventilation (Heterogeneity Index, HI% and Ventilation Defect Percentage, VDP) data from XV scans obtained 1 week apart showed excellent reproducibility in preliminary analysis. Moreover, derived global metrics such as ventilation heterogeneity and VDP varied by less than 2% for each patient analyzed. In the case of normal lung function (as indicated by PFT), XV scan results were consistent over multiple days, despite variability in imaging conditions. In the next case, XV and PFT measurements at 4-months and 12-months post-treatment were validated. At 4-months this subject’s FEV1 was >100% of expected levels for normal lung function, and the FEV1/FVC ratio was 1.07. By 12-months, FEV1s had decreased to 81% of expected, with FEV1/FVC = 0.89. Similarly, XV indicates a moderate change in lung function over this period, with an increase in HI from 56.2% to 66.1% and an increase in VDP from 7.1% to 11.6%. Moreover, contour maps of specific ventilation highlight changes in the regional distribution of ventilation. The lower region of the right lung was substantially less ventilated at twelve months post-treatment, with compensation occurring in other regions, showing the potential of XV in capturing regional lung function changes not available from PFT. CONCLUSIONS: This ongoing trial demonstrate that XV is repeatable and sensitive, detecting modest regional changes in lung function, such as the location of abnormally ventilated regions that may be an early indicator for lung fibrosis. CLINICAL IMPLICATIONS: XV analysis using existing fluoroscopes, has significantly lower radiation-exposure (compared to CT), and huge potential for early detection and treatment of a variety of lung diseases. DISCLOSURES: Employee relationship with 4Dx Limited Please note: $20001 - $100000 Added 06/20/2019 by Richard Carnibella, source=Web Response, value=Salary No relevant relationships by John DeMarco, source=Web Response Employee $100000 Added 06/16/2019 by Jonathan Dusting, source=Web Response, value=Salary Owner/Founder relationship with 4Dx Please note: >$100000 Added 06/21/2019 by Andreas Fouras, source=Web Response, value=Ownership interest Owner/Founder relationship with 4Dx Please note: >$100000 Added 06/21/2019 by Andreas Fouras, source=Web Response, value=Ownership interest Employee relationship with 4Dx Please note: >$100000 Added 06/20/2019 by Robert Jamison, source=Web Response, value=Salary Owner/Founder relationship with 4Dx Please note: >$100000 Added 06/20/2019 by Robert Jamison, source=Web Response, value=Ownership interest No relevant relationships by Cynthia Martin, source=Admin input Employee relationship with 4Dx Please note: $20001 - $100000 Added 06/20/2019 by Punit Shah, source=Web Response, value=Salary No relevant relationships by Stephen Shiao, source=Web Response Employee relationship with 4Dx Limited Please note: >$100000 Added 06/20/2019 by Neeraj Vij, source=Web Response, value=Salary Employee relationship with 4Dx Please note: $20001 - $100000 Added 06/20/2019 by David Wenger, source=Web Response, value=Salary Employee relationship with 4Dx Limited Please note: $20001 - $100000 Added 06/20/2019 by Alex Winnett, source=Web Response, value=Salary

SESSION TITLE: Wednesday Abstract Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM PURPOSE: PE is 3rd leading cause of death in hospitalized patients. There are well validated clinical scores (Wells, Geneva score) and laboratory test like d-dimer to rule out PE as potential diagnosis. Unfortunately, implementation of such algorithm remains poor and under-utilized in busy clinical practice. The rate of CT pulmonary angiogram (CTPA) has significantly increased over number of years. CTPA has several disadvantages such as contrast induced nephropathy and potentially renal failure. Many patients also have contrast allergy and chronic kidney disease where CTPA can't be performed. Alternative is nuclear medicine ventilation perfusion (V/Q) scan that is time consuming and often not readily available. Given, above reasons we feel there is potentially role of CT and fluoroscopy based 4Dx CFPA and 4DxV analysis in diagnosis and follow up for patients presenting with PE. Our hypothesis is CFPA technology will reduce overuse of CTPA and serve as an follow up imaging modality that is simple and doesn't involve contrast METHODS: We are currently performing P&F study evaluating 4Dx CFPA technology in diagnosis of PE. As per our IRB-approved protocol total of 30 de-identified images of CTPA (15 positive and 15 negative) will be selected. First 4 cases (2 positive and 2 negative) will be utilized to standardize and validate CFPA analysis of pulmonary vessel caliber at 4DX. Next 26 cases (13 positive and 13 negative) will be blinded to research team at 4DX and clinical team at Temple University will have full clinical information. Primary Objective – Determine if 4DX CFPA technology can identify the patients with PE as compared to gold standard CTPA. Secondary Objective – Determine if 4Dx CFPA technology can identify degree of vasculature abnormality compared to CTPA. RESULTS: We are reporting result of first 4 unblinded cases (two cases with PE and two without PE). 4Dx software derives non-contrast image from de-identified CTPA imaging for measuring vessel caliber that are color coded as large [Red (>10 mm)], medium [Yellow/Green/Orange (5-10 mm)] and small [Blue (< 5 mm)]and scaled according to vessel diameter. There are significant global changes in cross sectional vessel area (mm2) and volume (mm) in cases of pulmonary embolism vs those without. CONCLUSIONS: Our initial results demonstrate contrast-free qualitative and quantitative analysis of vessel caliber in PE vs non-PE subjects. We aim to further validate CFPA technique in in next phase, where research staff will be blinded to original CTPA results. This study will be followed by future prospective study where CFPA will be validated prior to performance of CTPA. CLINICAL IMPLICATIONS: A) Reduce over utilization of CTPA. B) Reduce chances of contrast induced nephropathy. C) Simple, effective way of rapid diagnosis of PE and reduce time to therapeutic anti-coagulation. D) CFPA can be used as follow up testing following acute PE. DISCLOSURES: No relevant relationships by Ryan Cobb, source=Web Response No relevant relationships by Gary Cohen, source=Web Response No relevant relationships by Chandra Dass, source=Web Response Employee $100000 Added 06/16/2019 by Jonathan Dusting, source=Web Response, value=Salary Owner/Founder relationship with 4Dx Please note: >$100000 Added 06/21/2019 by Andreas Fouras, source=Web Response, value=Ownership interest No relevant relationships by Joseph Panaro, source=Web Response No relevant relationships by Parth Rali, source=Web Response Employee relationship with 4Dx Limited Please note: >$100000 Added 06/20/2019 by Neeraj Vij, source=Web Response, value=Salary

A 2D or 3D velocity field is reconstructed from a cross correlation analysis of image pairs of a sample, without first reconstructing images of the sample spatial structure. The method can be implemented via computer tomographic X-ray particle image Velocimetry, using multiple projection angles, with phase contrast images forming dynamic speckle pat terns. Estimated cross-correlations may be generated via con Volution of a measured autocorrelation function with a Veloc ity probability density function, and the velocity coefficients iteratively optimized to minimize the error between the esti mated cross-correlations and the measured cross-correla tions. The method may be applied to measure blood flow, and the motion of tissue and organs such as heart and lungs.

The effect of erythrocyte aggregation on blood viscosity and microcirculatory flow is a poorly understood area of haemodynamics, especially with relevance to serious pathological conditions. Advances in microfluidics have made it possible to study the details of blood flow in the microscale, however, important issues such as the relationship between the local microstructure and local flow characteristics have not been investigated extensively. In the present study an experimental system involving simple brightfield microscopy has been successfully developed for simultaneous, time-resolved quantification of velocity fields and local aggregation of human red blood cells (RBC) in microchannels. RBCs were suspended in Dextran and phosphate buffer saline solutions for the control of aggregation. Local aggregation characteristics were investigated at bulk and local levels using statistical and edge-detection image processing techniques. A special case of aggregating flow in a microchannel, in which hematocrit gradients were present, was studied as a function of flowrate and time. The level of aggregation was found to strongly correlate with local variations in velocity in both the bulk flow and wall regions. The edge detection based analysis showed that near the side wall large aggregates are associated with regions corresponding to high local velocities and low local shear. On the contrary, in the bulk flow region large aggregates occurred in regions of low velocity and high erythrocyte concentration suggesting a combined effect of hematocrit and velocity distributions on local aggregation characteristics. The results of this study showed that using multiple methods for aggregation quantification, albeit empirical, could help towards a robust characterisation of the structural properties of the fluid.

Microscale blood flow is characterised by heterogeneous distributions of hematocrit, viscosity and velocity. In microvascular bifurcations, cells are unevenly distributed between the branches, and this effect can be amplified in subsequent branches depending on a number of parameters. We propose an approach to infer hematocrit profiles of human blood flowing through a bifurcating microchannel. The influence of aggregation, induced by the addition of Dextran 2000 to the samples, is also considered. Averaged values indicate plasma skimming, particularly in the presence of red blood cell (RBC) aggregation. Using an empirical model, the hematocrit profiles are used to estimate local relative viscosity distributions. Simulations are used to predict how the non-uniform viscosity influences the velocity profiles. Comparing these data to velocity profiles of RBCs measured using particle image velocimetry provides validation of the model. It is observed that aggregation blunts velocity profiles after a long straight section of channel. Downstream of the bifurcation, skewing of the velocity profiles is detected, which is enhanced by aggregation. The proposed methodology is capable of providing hitherto unreported information on important aspects of microscale blood rheology.

A new approach is presented for detecting the early onset of amyloid fibril formation of insulin in a fluidic environment. The fibrillogenesis of insulin in a well-characterized Taylor-Couette flow cell was analyzed in situ using Raman spectroscopy in combination with principal components analysis (PCA). Raman spectra recorded using a 532.5 nm excitation laser revealed a more rapid fibrillogenesis process during the first 90 min of shearing than previously reported for samples exposed to flow. Bands corresponding to intermolecular H-bonded β-sheet structure of insulin at 1678, 1630, and 1625 cm(-1) observed in the Raman difference spectra between unsheared insulin and sheared insulin show an increase in intensity as a function of shear exposure time, which is characteristic of fibril formation, with the first changes detected after 10 min. Additional analysis of samples removed from the flow cell after specific time periods provided conformation of the flow-enhanced fibrillogenesis process, including the detection of early fibril formation after only 1 min of shearing. FT-IR spectra of the insulin solutions showed evolution of bands at 1673 and 1633 cm(-1) from an increase in H-bonded β-turn and β-sheet structures, respectively, while fluorescence emission spectra detected the presence of a new emission band at 482 nm. TEM images confirmed the early onset of fibril formation at 1 min shear exposure, before a maturation and concentration increase of fibrils with further shearing. This study highlights the ability of fluid flows to accelerate insulin fibril formation, which has important implications for biotechnology applications such as the purification process of insulin therapeutic drugs in the pharmaceutical industry, as well as the use of optical-based methods for detecting fibrillogenesis.

The spatial characteristics of blood viscosity were investigated by combining a newly developed constitutive equation with shear deformation fields calculated from velocity measurements obtained by a μPIV based technique. Blood at physiological hematocrit levels and in the presence of aggregation was sheared in a narrow gap plate-plate geometry and the velocity and aggregation characteristics were determined from images captured using a high resolution camera. Changes in the microstructure of blood caused by aggregation were observed to affect the flow characteristics. At low shear rates, high aggregation and network formation caused the RBC motion to become essentially two-dimensional. The measured velocity fields were used to estimate the magnitude of shear which was subsequently used in conjunction with the new model to assess the spatial variation of viscosity across the flow domain. It was found that the non-uniform microstructural characteristics of blood influence its viscosity distribution accordingly. The viscosity of blood estimated in the core of the examined flow, using a zero-gradient core velocity profile assumption, was found to be significantly higher than the overall effective viscosity determined using other velocity profile assumptions.

This paper describes an experimental study of the response of a freely vibrating cylinder with low mass ratio and high damping to steady and pulsating crossflow for Reynolds numbers in the range 120–2900. A rigid circular cylinder was cantilevered by means of a plate spring allowing it to oscillate in the stream-wise direction only. A camera-based technique was employed for tracking the cylinder vibration while the wake fluctuations were measured by a laser-Doppler system. The results show that the forced excitation from pulsating flow can take over control of the wake and/or the cylinder oscillations in a complex manner. The overall response depends strongly on two main parameters: the ratios of the pulsation frequency to the structural frequency and to the vortex shedding frequency from a fixed cylinder in steady flow. When the excitation frequency from both the wake and the external pulsation coincided with the natural frequency of the structure, the r.m.s. amplitude of the cylinder vibration increased up to 400% compared to that for the same reduced velocity in steady flow. In this case, maximum end displacements exceeded 35% of the cylinder diameter.

By directly monitoring stirred protein solutions with Raman spectroscopy, the reversible unfolding of proteins caused by fluid shear is examined for several natural proteins with varying structural properties and molecular weight. While complete denaturation is not observed, a wide range of spectral variances occur for the different proteins, indicating subtle conformational changes that appear to be protein-specific. A number of significant overall trends are apparent from the study. For globular proteins, the overall extent of spectral variance increases with protein size and the proportion of β-structure. For two less structured proteins, fetuin and α-casein, the observed changes are of relatively low magnitude, despite the greater molecular structural mobility of these proteins. This implies that other protein-specific factors, such as posttranslational modifications, may also be significant. Individual band changes occurring in the spectral profiles of each individual protein are also discussed in detail.

The transition pathway leading to chaotic flow in a Taylor–Couette vessel of aspect ratio γ=11.2 and radius ratio η=0.81 with only the inner cylinder rotating has been studied using time-resolved particle image velocimetry. A hitherto unreported sequence of transitions, whereby the flow changes from wavy vortex flow to a quasiperiodic state of high modulation frequency, is identified using spatially resolved spectral analysis. The nature of the modulated wavy vortex flow is detailed using proper orthogonal decomposition, through which it is revealed that the modulation is similar to a fast moving azimuthal wave (FMAW). In contrast with previous observations of the FMAW at a much higher aspect ratio, the mode appears directly after wavy vortex flow and as a precursor to the CVF regime. The FMAW is also associated with codirectional vorticity fluctuations on each Taylor vortex core that diminish in strength close to the endwalls.

The mixing in a Taylor–Couette flow cell is quantified with laser induced fluorescence (LIF). Time-resolved, two-dimensional measurements of dye concentration have been obtained in the non-wavy Taylor vortex flow regime (Re=330) and analysed in order to characterise the intervortex and intravortex mixing. The results show clear evidence of intervortex mixing especially near the inner wall region and the inflow boundaries, and demonstrate that Taylor vortex flow cannot be simply assumed as a series of well mixed tanks. Intravortex mixing is slow in relation to the mixing between adjacent vortices and is more rapid in the azimuthal direction than the meridional plane. Increasing Re towards the upper limit of the Taylor vortex flow regime (Re=950) results in enhanced mixing despite the apparent absence of an azimuthal wave. Both the intervortex and intravortex mixing times reduce substantially and the intravortex mixing in the azimuthal and meridional planes occur at similar timescales.

The flow of red blood cells is investigated by means of a micro-PIV based technique at physiological hematocrit levels and in the presence of aggregation. The technique developed differs from typical micro-PIV as the RBCs are used as tracer particles and illumination is provided by a simple halogen light source. Changes in the microstructure of blood caused by aggregation were observed to affect the RBC flow characteristics in a narrow-gap plate-plate geometry. At low shear rates, high aggregation caused the RBC motion to become essentially two-dimensional and network formation lead to the flow deviating from the expected radial profile. The accuracy of the micro-PIV technique was shown to be dependent on aggregation, illustrating the need to take aggregation into account in future RBC flow studies.

Conformational changes due to externally applied physiochemical parameters, including pH, temperature, solvent composition, and mechanical forces, have been extensively reported for numerous proteins. However, investigations on the effect of fluid shear flow on protein conformation remain inconclusive despite its importance not only in the research of protein dynamics but also for biotechnology applications where processes such as pumping, filtration, and mixing may expose protein solutions to changes in protein structure. By combining particle image velocimetry and Raman spectroscopy, we have successfully monitored reversible, shear-induced structural changes of lysozyme in well-characterized flows. Shearing of lysozyme in water altered the protein's backbone structure, whereas similar shear rates in glycerol solution affected the solvent exposure of side-chain residues located toward the exterior of the lysozyme alpha-domain. The results demonstrate the importance of measuring conformational changes in situ and of quantifying fluid stresses by the three-dimensional shear tensor to establish reversible unfolding or misfolding transitions occurring due to flow exposure.