micro-particle-image-velocimetry-for-velocity-profile-measurements

Micro-particle Image Velocimetry for Velocity Profile Measurements of Micro Blood Flows

Micro-particle image velocimetry (&mu;PIV) is used to visualize paired images of micro particles seeded in blood flows. The images are cross-correlated to ...

University of Ottawa 

Micro particle image velocimetry (&micro;PIV) est une m&eacute;thode commune pour &eacute;valuer le comportement de l&#39;&eacute;coulement dans les microvaisseaux sanguins in vitro comme in vivo. L&#39;utilisation de globules rouges (h&eacute;maties) sous forme de particules de traceur, g&eacute;n&eacute;ralement consid&eacute;r&eacute; comme in vivo, cr&eacute;e une grande profondeur de corr&eacute;lation (DOC), m&ecirc;me plus grande que le navire lui-m&ecirc;me, ce qui diminue la pr&eacute;cision de la m&eacute;thode. Les limitations de &micro;PIV pour les mesures du d&eacute;bit sanguin issu de RBC suivi encore doivent &ecirc;tre &eacute;valu&eacute;s. Dans cette &eacute;tude, in vitro et in silico mod&egrave;les ont servi &agrave; comprendre l&#39;effet de la DOC sur les mesures du d&eacute;bit sanguin &agrave; l&#39;aide de particules de traceur de RBC &micro;PIV. Nous avons donc utilis&eacute; une technique &micro;PIV pour &eacute;valuer l&#39;&eacute;coulement de sang dans un tube de verre 15 &micro;m rayon avec une cam&eacute;ra CMOS &agrave; haute vitesse. Le tube a &eacute;t&eacute; perfus&eacute; avec un &eacute;chantillon de sang d&#39;h&eacute;matocrite 40 %. Le d&eacute;bit mesur&eacute; par un chatoiement corr&eacute;l&eacute;es Croix suivi technique a &eacute;t&eacute; compar&eacute; au d&eacute;bit de la pompe. En outre, un mod&egrave;le tridimensionnel de la RBC-flux m&eacute;canique a &eacute;t&eacute; utilis&eacute; pour simuler optique speckle mobile &agrave; h&eacute;matocrite de 20 % et 40 %, de 15 &agrave; 20 &micro;m rayon circulaire tubes, aux plans de nettet&eacute; diff&eacute;rents, d&eacute;bits et pour diverses formes de profil de vitesse. Les profils de vitesse extraites des images simul&eacute;es ont &eacute;t&eacute; compar&eacute;s avec le bon accord avec les profils de vitesse correspondantes impl&eacute;ment&eacute;es dans le mod&egrave;le m&eacute;canique. Les d&eacute;bits &agrave; la fois le fant&ocirc;me de flux in vitro et le mod&egrave;le math&eacute;matique ont &eacute;t&eacute; mesur&eacute;es avec pr&eacute;cision avec moins de 10 % d&#39;erreurs. R&eacute;sultats de la simulation ont d&eacute;montr&eacute; que l&#39;h&eacute;matocrite (jumel&eacute; tests t, p = 0,5) et le rayon du tube (p = 0,1) n&#39;influencent pas la pr&eacute;cision du d&eacute;bit mesur&eacute;, alors que la forme du profil de la vitesse (p &lt; 0,001) et l&#39;emplacement de la do (p &lt; 0,001) plan de mise au point, comme indiqu&eacute; par mesur&eacute;e Erreurs allant de 3 % &agrave; 97 %. En conclusion, l&#39;utilisation de globules rouges sous forme de particules traceur rend un grand DOC et affecte le traitement de l&#39;image n&eacute;cessaire pour estimer la vitesse d&#39;&eacute;coulement. Nous avons trouv&eacute; que la m&eacute;thode actuelle de &micro;PIV est acceptable pour estimer la vitesse d&#39;&eacute;coulement &agrave; la condition que la mesure s&#39;effectue dans le plan &eacute;quatorial du navire. Dans le cas contraire, il n&#39;est pas une m&eacute;thode appropri&eacute;e pour estimer la forme du profil de la vitesse.

Pr&eacute;cision de mesure de vitesse en microhemodynamics optique : exp&eacute;rience et simulation.

Micro particle image velocimetry (ÂµPIV) is a common method to assess flow behavior in blood microvessels in vitro as well as in vivo. The use of red blood cells (RBCs) as tracer particles, as generally considered in vivo, creates a large depth of correlation (DOC), even as large as the vessel itself, which decreases the accuracy of the method. The limitations of ÂµPIV for blood flow measurements based on RBC tracking still have to be evaluated. In this study, in vitro and in silico models were used to understand the effect of the DOC on blood flow measurements using ÂµPIV RBC tracer particles. We therefore employed a ÂµPIV technique to assess blood flow in a 15Â Âµm radius glass tube with a high-speed CMOS camera. The tube was perfused with a sample of 40% hematocrit blood. The flow measured by a cross-correlating speckle tracking technique was compared to the flow rate of the pump. In addition, a three-dimensional mechanical RBC-flow model was used to simulate optical moving speckle at 20% and 40% hematocrits, in 15 and 20Â Âµm radius circular tubes, at different focus planes, flow rates and for various velocity profile shapes. The velocity profiles extracted from the simulated pictures were compared with good agreement with the corresponding velocity profiles implemented in the mechanical model. The flow rates from both the in vitro flow phantom and the mathematical model were accurately measured with less than 10% errors. Simulation results demonstrated that the hematocrit (paired t tests, p = 0.5) and the tube radius (p = 0.1) do not influence the precision of the measured flow rate, whereas the shape of the velocity profile (p < 0.001) and the location of the focus plane (p < 0.001) do, as indicated by measured errors ranging from 3% to 97%. In conclusion, the use of RBCs as tracer particles makes a large DOC and affects the image processing required to estimate the flow velocities. We found that the current ÂµPIV method is acceptable to estimate the flow rate on the condition that the measurement takes place at the equatorial plane of the vessel. Otherwise, it is not an appropriate method to estimate the shape of the velocity profile.

Velocity measurement accuracy in optical microhemodynamics: experiment and simulation.

Micro particle image velocimetry (&micro;PIV) &egrave; un metodo comune per valutare il comportamento di flusso di sangue Talengectasia in vitro, cos&igrave; come in vivo. L&#39;uso di cellule rosse del sangue (globuli rossi) come particelle di tracciante, come generalmente considerati in vivo, crea una grande profondit&agrave; di correlazione (DOC), anche grandi come la nave stessa, che fa diminuire la precisione del metodo. Le limitazioni di &micro;PIV per misure di flusso di sangue basato su RBC ancora di rilevamento devono essere valutati. In questo studio, in vitro ed in silico modelli sono stati utilizzati per capire l&#39;effetto del DOC su misure di flusso di sangue usando &micro;PIV RBC tracciante particelle. Di conseguenza abbiamo impiegato una tecnica &micro;PIV per valutare il flusso di sangue in un tubo di vetro di raggio &micro;m 15 con una fotocamera CMOS ad alta velocit&agrave;. Il tubo &egrave; stato irrorato con un campione di sangue ematocrito 40%. Il flusso misurato da un cross-correlazione speckle tracking tecnica &egrave; stato confrontato con la portata della pompa. Inoltre, un modello tridimensionale di RBC-flusso meccanico &egrave; stato utilizzato per simulare speckle movimento ottico al 20% e 40% ematocrito, in 15 e 20 &micro;m raggio circolare tubi, a fuoco diversi piani, portate e per varie forme di profilo di velocit&agrave;. I profili di velocit&agrave; estratti dalle immagini simulate sono stati confrontati con buon accordo con i profili di velocit&agrave; corrispondente implementati nel modello meccanico. Le portate dal fantasma di flusso in vitro sia il modello matematico sono state misurate con precisione con meno di 10% errori. Risultati delle simulazioni hanno dimostrato che l&#39;ematocrito (accoppiato t test, p = 0.5) e il raggio del tubo (p = 0.1) non influenzano la precisione della portata misurata, considerando che la forma del profilo di velocit&agrave; (p &lt; 0,001) e la posizione del do di fuoco aereo (p &lt; 0.001), come indicato dal misurato errori che vanno dal 3% al 97%. In conclusione, l&#39;uso di globuli rossi come particelle di tracciante rende un grande DOC e influisce sull&#39;elaborazione immagine necessaria per stimare la velocit&agrave; di flusso. Abbiamo trovato che il metodo attuale di &micro;PIV &egrave; accettabile per la stima della portata a condizione che la misura avviene presso il piano equatoriale della nave. In caso contrario, non &egrave; un metodo adeguato per valutare la forma del profilo di velocit&agrave;.

Katie L. Pitts

Department of Chemical and Biological Engineering

University of Ottawa

Micro-particle Image Velocimetry for Velocity Profile Measurements of Micro Blood Flows

Katie L. Pitts

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Chemical and Biological Engineering

University of Ottawa

Micro-particle Image Velocimetry for Velocity Profile Measurements of Micro Blood Flows

Department of Chemical and Biological Engineering