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 ...

controlled-microfluidic-environment-for-dynamic-investigation-red

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white ...

University of Ottawa 

Bioimpedance spectroscopy (BIS) permits evaluation of extra- and intracellular fluid volumes in patients. We wished to examine whether this technique, used in combination with hematocrit measurement, can reliably monitor fluid transfers during dialysis. Ankle to wrist BIS measurements were collected during 21 dialysis runs while hematocrit was continuously monitored in the blood line by an optical device. Extracellular (ECW) and intracellular (ICW) water volumes were calculated using Hanai's electrical model of suspensions. Plasma volume variations were calculated from hematocrit, and changes in interstitial volume were calculated as the difference between ECW and plasma volume changes. Because accuracy of ICW was too low, changes in ICW were calculated as the difference between ultrafiltered volume and ECW changes. Total body water (TBW) volumes calculated pre- and postdialysis were, respectively, 3.25+/-3.2 and 1.95+/-2.5 liters lower on average than TBW given by Watson et al.'s correlation. Average decreases in fluid compartments expressed as percentage of ultrafiltered volume were as follows: plasma, 18%; interstitial, 28%, and ICW, 54%. When the ultrafiltered volume was increased in a patient in successive runs, the relative contributions of ICW and interstitial fluid were augmented so as to reduce the relative drop in plasma volume.

Continuous monitoring of plasma, interstitial, and intracellular fluid volumes in dialyzed patients by bioimpedance and hematocrit measurements.

Spectroscopie de bioimp&eacute;dance (BIS) permet d&#39;&eacute;valuer extra - et intracellulaires volumes de liquide chez les patients. Nous avons voulu examiner si cette technique, utilis&eacute;e en combinaison avec la mesure de l&#39;h&eacute;matocrite, peut surveiller avec fiabilit&eacute; des transferts de fluides pendant la dialyse. Cheville aux mesures BIS poignet ont &eacute;t&eacute; recueillies au cours de 21 pistes de dialyse tandis que l&#39;h&eacute;matocrite a &eacute;t&eacute; surveill&eacute;e de fa&ccedil;on continue dans la lign&eacute;e de sang par un dispositif optique. Extracellular (ECW) et le volume d&#39;eau intracellulaire (ICW) ont &eacute;t&eacute; calcul&eacute;s en utilisant le mod&egrave;le &eacute;lectrique de Hanai de suspensions. Les variations de volume de plasma ont &eacute;t&eacute; calcul&eacute;es de l&#39;h&eacute;matocrite, et les variations du volume interstitiel ont &eacute;t&eacute; calcul&eacute;es comme la diff&eacute;rence entre les changements de volume de plasma et de la ECW. Parce que la pr&eacute;cision de l&#39;ICW &eacute;tait trop faible, les variations ICW ont &eacute;t&eacute; calcul&eacute;es comme la diff&eacute;rence entre ultrafiltr&eacute;, du volume et l&#39;&eacute;volution de la ECW. Volumes d&#39;eau (TBW) corporelle totale calcul&eacute;e pr&eacute;- et postdialysis sont respectivement 3.25+/-3.2 et 1.95+/-2.5 litres baisser en moyenne que TBW donn&eacute;e par corr&eacute;lation de Watson et al. Moyenne diminue dans les compartiments fluides exprim&eacute;es en pourcentage du volume ultrafiltr&eacute; &eacute;tait comme suit : plasma, 18 % ; interstitielle, ICW, 54 % et 28 %. Lorsque le volume obtenu par ultrafiltration a augment&eacute; chez un patient au cours des essais successifs, les contributions relatives de la CIF et le liquide interstitiel ont &eacute;t&eacute; augment&eacute;es afin de r&eacute;duire la baisse relative du volume plasmatique.

Surveillance continue du plasma, interstitiel et les volumes de liquide intracellulaires chez les patients dialys&eacute;s par bioimp&eacute;dance et h&eacute;matocrite mesures.

Bioimpedenza spettroscopia (BIS) consente la valutazione di volumi fluidi intracellulari ed extra - nei pazienti. Abbiamo voluto esaminare se questa tecnica, utilizzata in combinazione con la misurazione dell&#39;ematocrito, pu&ograve; monitorare in modo affidabile trasferimenti fluidi durante la dialisi. Caviglia a misurazioni BIS al polso sono stati raccolti durante le esecuzioni di dialisi 21 mentre l&#39;ematocrito &egrave; stato costantemente monitorato nella linea di sangue da un dispositivo ottico. Extracellular (ECW) e volumi di acqua intracellulare (ICW) sono stati calcolati utilizzando il modello elettrico di Hanai delle sospensioni. Variazioni di volume del plasma sono stati calcolati dall&#39;ematocrito, e le variazioni di volume interstiziale sono state calcolate come differenza tra le variazioni di volume del plasma ed ECW. Perch&eacute; la precisione di ICW era troppo bassa, cambiamenti nella ICW sono stati calcolati come differenza tra il volume di ultrafiltrato e cambiamenti ECW. Volumi di acqua (TBW) corpo totale calcolato pre e postdialysis erano, rispettivamente, 3.25+/-3.2 e 1.95+/-2.5 litri inferiore mediamente pi&ugrave; TBW dato dalla correlazione di Watson et al. Medie diminuisce in compartimenti fluidi espressi come percentuale del volume di ultrafiltrato erano come segue: plasma, 18%; interstiziale, 28% e ICW, il 54%. Quando il volume di ultrafiltrato &egrave; stato aumentato in un paziente in sedute successive, i contributi relativi di ICW e fluido interstiziale erano aumentati in modo da ridurre il relativo calo di volume plasmatico.

Monitoraggio continuo di plasma, interstiziale e volumi fluidi intracellulari in pazienti dializzati da misurazioni bioimpedenza e dell&#39;ematocrito.

Espectroscopia de bioimpedancia (BIS) permite la evaluaci&oacute;n de vol&uacute;menes de fluido intracelulares y extra en pacientes. Deseamos examinar si esta t&eacute;cnica, utilizada en combinaci&oacute;n con la medici&oacute;n de hematocrito, confiablemente puede supervisar las transferencias de fluidos durante la di&aacute;lisis. Tobillo para mediciones de mu&ntilde;eca BIS se recolectaron durante 21 carreras de di&aacute;lisis mientras hematocrito fue monitoreado continuamente en la l&iacute;nea de sangre por un dispositivo &oacute;ptico. Extracellular (ECW) y vol&uacute;menes de agua intracelulares (ICW) se calcularon usando el modelo el&eacute;ctrico de Hanai de suspensiones. Se calcularon las variaciones de volumen del plasma de hematocrito, y cambios en el volumen intersticial se calcularon como la diferencia entre los cambios de volumen ECW y plasma. Exactitud de ICW fue demasiado bajo, cambios en ICW se calculan como la diferencia entre ultrafiltrada volumen y los cambios ECW. Caudales de corporal total (TBW) calculan pre- y postdialysis eran, respectivamente, 3.25+/-3.2 y 1.95+/-2.5 litros menores en promedio que TBW dada por correlaci&oacute;n de Watson et al. Promedio disminuye en compartimientos l&iacute;quidos expresados como porcentaje del volumen de ultrafiltrada fueron los siguientes: plasma, 18%; intersticial, 28% y ICW, 54%. Cuando el volumen ultrafiltrada fue aumentado en un paciente en las ejecuciones, las contribuciones relativas de ICW y l&iacute;quido intersticial fueron aumentadas con el fin de reducir la ca&iacute;da relativa del volumen plasm&aacute;tico.

Monitorizaci&oacute;n continua del plasma, intersticial y vol&uacute;menes de l&iacute;quido intracelulares en pacientes dializados por medidas de bioimpedancia y hematocrito.

Extracellular (ECW) y vol&uacute;menes intracelulares (ICW) fueron medidos usando ambos segmentaria y espectroscopia de bioimpedancia de mu&ntilde;eca y tobillo (W-A) (5-1000 kHz) en 15 sujetos sanos (7 hombres, 8 mujeres). En el protocolo i, el tema, despu&eacute;s de estar sentado durante 30 minutos, puso supino durante al menos 30 minutos. En el segundo Protocolo, el tema, que hab&iacute;a sido supino durante 1 hora, se sent&oacute; en la cama durante 10 minutos y regres&oacute; a la posici&oacute;n supina durante otra hora. Resistencias de ECW y ICW segmentarias de piernas, brazos y tronco fueron medidas por la colocaci&oacute;n de cuatro electrodos de tensi&oacute;n en la mu&ntilde;eca, hombro, parte superior del muslo y tobillo y usando teor&iacute;a de conductividad de Hanai. W A resistencias fueron encontradas para estar muy cerca de la suma de las resistencias segmentarias. Cuando el cambio desde una posici&oacute;n sentada a la supina (Protocolo n &deg; 1), la resistencia media de la pierna ECW aumentaron 18,2%, de brazo y W-A 12.4%. Resistencia del tronco tambi&eacute;n aumentada, pero no de forma significativa en un 4,8%. Resistencia de ICW correspondientes incrementos fueron menores para piernas (3,7%) y el brazo (-0,7%) pero m&aacute;s grande para el tronco (21,4%). Vol&uacute;menes ECW corporal total de mediciones segmentarias estaban de acuerdo con W-A y correlaci&oacute;n antropomorfo de Watson. La disminuci&oacute;n en el volumen total de ECW (cuando supina) calculada a partir de las resistencias segmentarias fue 0,79 l menos que el W-A uno (1,12 l). Reducci&oacute;n de volumen ICW total fueron (segmentaria) de 3,4% y 3,8% (W-A). Las pruebas del Protocolo 2 confirmaron que la resistencia y los valores de volumen de l&iacute;quido no fueron afectados por un cambio de posici&oacute;n temporal.

Variaciones de volumen extracelular e intracelular durante el cambio postural midieron segmentaria y espectroscopia de bioimpedancia de mu&ntilde;eca y tobillo.

Extracellular (ECW) and intracellular (ICW) volumes were measured using both segmental and wrist-ankle (W-A) bioimpedance spectroscopy (5-1000 kHz) in 15 healthy subjects (7 men, 8 women). In the 1st protocol, the subject, after sitting for 30 min, laid supine for at least 30 min. In the second protocol, the subject, who had been supine for 1 hr, sat up in bed for 10 min and returned to supine position for another hour. Segmental ECW and ICW resistances of legs, arms and trunk were measured by placing four voltage electrodes on wrist, shoulder, top of thigh and ankle and using Hanai's conductivity theory. W-A resistances were found to be very close to the sum of segmental resistances. When switching from sitting to supine (protocol 1), the mean ECW leg resistance increased by 18.2%, that of arm and W-A by 12.4%. Trunk resistance also increased but not significantly by 4.8%. Corresponding increases in ICW resistance were smaller for legs (3.7%) and arm (-0.7%) but larger for the trunk (21.4%). Total body ECW volumes from segmental measurements were in good agreement with W-A and Watson anthropomorphic correlation. The decrease in total ECW volume (when supine) calculated from segmental resistances was at 0.79 l less than the W-A one (1.12 l). Total ICW volume reductions were 3.4% (segmental) and 3.8% (W-A). Tests of protocol 2 confirmed that resistance and fluid volume values were not affected by a temporary position change.

Extracellular and intracellular volume variations during postural change measured by segmental and wrist-ankle bioimpedance spectroscopy.

Extracellular (ECW) et intracellulaires (ICW) volumes ont &eacute;t&eacute; mesur&eacute;s &agrave; l&#39;aide des deux segmentaire et spectroscopie de bioimp&eacute;dance poignet-cheville (W-A) (5-1000 kHz) dans 15 sujets sains (7 hommes, 8 femmes). Dans le premier protocole, le sujet, apr&egrave;s s&#39;&ecirc;tre assis pendant 30 min, mis en position couch&eacute;e pendant au moins 30 min. Dans le second protocole, le sujet, qui avait &eacute;t&eacute; en position couch&eacute;e pour 1 heure, se redressa dans son lit pendant 10 min et remis en position couch&eacute;e pendant une autre heure. Des r&eacute;sistances ECW et ICW segmentaires des jambes, bras et du tronc ont &eacute;t&eacute; mesur&eacute;s en pla&ccedil;ant quatre &eacute;lectrodes de voltage sur le poignet, &eacute;paule, haut de cuisse et de la cheville et &agrave; l&#39;aide de la th&eacute;orie de conductivit&eacute; de Hanai. W-A r&eacute;sistances se sont r&eacute;v&eacute;l&eacute;s pour &ecirc;tre tr&egrave;s proche de la somme des r&eacute;sistances segmentaires. Quand passer d&#39;assise &agrave; la position couch&eacute;e (protocole 1), la r&eacute;sistance de jambe ECW moyenne a augment&eacute; de 18,2 %, celle de bras et de W-A de 12,4 %. R&eacute;sistance de tronc a &eacute;galement augment&eacute;e, mais pas de fa&ccedil;on significative de 4,8 %. Des hausses correspondantes dans la r&eacute;sistance de l&#39;ICW &eacute;taient plus petits pour les jambes (3,7 %) et les bras (-0,7 %) mais plus grand pour le tronc (21,4 %). Volumes ECW corporelle totale de mesures segmentaires sont en bon accord avec W-A et corr&eacute;lation anthropomorphe Watson. La diminution de volume total de ECW (lorsqu&#39;il est en position couch&eacute;e) calcul&eacute;e &agrave; partir des r&eacute;sistances segmentaires est &agrave; 0,79 l de moins que le W-A (1,12 l). Des r&eacute;ductions de volume totales ICW ont &eacute;t&eacute; (segmentaire) de 3,4 % et 3,8 % (W-A). Tests de protocole 2 ont confirm&eacute; que la r&eacute;sistance et les valeurs de volume de fluide ne sont pas affect&eacute;es par un changement de poste temporaire.

Mesur&eacute; les variations de volume extracellulaire et intracellulaire pendant changement postural par segmentaire et spectroscopie de bioimp&eacute;dance poignet-cheville.

Extracellular (ECW) e intracellulare (ICW) volumi sono stati misurati utilizzando entrambi segmentale e spettroscopia di bioimpedenza polso-caviglia (W-A) (5-1000 kHz) in 15 soggetti sani (7 uomini, 8 donne). Nel protocollo 1, il soggetto, dopo la seduta per 30 min, pose supino per almeno 30 min. Il secondo protocollo, il soggetto, che era stato supino per 1 ora, mise a sedere nel letto per 10 min e torn&ograve; in posizione supina per un&#39;altra ora. Le resistenze di ECW e ICW segmentale di gambe, braccia e tronco sono state misurate ponendo quattro elettrodi di tensione sul polso, spalla, parte superiore della coscia e della caviglia e utilizzando la teoria di conducibilit&agrave; di Hanai. W-A resistenze sono state trovate per essere molto vicino alla somma delle resistenze segmentale. Quando il passaggio da seduto a Supino (protocollo 1), la resistenza di gamba ECW media aumentata del 18,2%, quella del braccio e W-A del 12,4%. Resistenza di tronco anche aumentata, ma non in modo significativo da 4,8%. Corrispondente aumento della resistenza ICW era pi&ugrave; piccoli per le gambe (3,7%) e il braccio (-0,7%) ma pi&ugrave; grande per il tronco (21,4%). Total body ECW volumi da misurazioni segmentale erano in buon accordo con W-A e correlazione antropomorfi Watson. La diminuzione di volume totale di ECW (quando supina) calcolata dalle resistenze segmentale era a 0,79 l W-A meno uno (1,12 l). Riduzioni di volume totale ICW erano 3,4% (segmentale) e il 3,8% (W-A). Test del protocollo 2 ha confermato che resistenza e i valori del volume del liquido non sono stati colpiti da un cambiamento di posizione temporanea.

Variazioni di volume extracellulare e intracellulare durante il cambiamento posturale misurata da segmentale e spettroscopia bioimpedenza polso-caviglia.

We propose a method for calculating directly total body water (TBW) volumes (V (t)) from whole body resistance extrapolated at infinite frequency (R (infinity)) using a XITRON 4200 impedance meter. Mean TBW resistivities for men and women were determined from measurements of R (infinity) and fat-free mass (FFM(d)) measured by DXA in 58 healthy subjects assuming an average hydration coefficient of 73.2%. Mean differences between V (t) measured by our new method and those deduced from DXA data were +0.11 +/- 1.61 L for women and +0.13 +/- 2.16 L for men. For validation, this method was tested with the same resistivities against a 2nd group of 16 volunteers and the mean difference between V (t) from impedance and DXA was -0.80 +/- 1.43 L. Since the resistance at 50 kHz (R (50)) was found to be equal, in average, to 1.230 R (infinity) for men and 1.223 R (infinity) for women, this method can also be applied at 50 kHz with a similar accuracy by estimating R (infinity) from R (50). When our new method was applied to the monitoring of water loss during 28 dialysis runs performed on 13 patients, it predicted a mean water loss equal to 94% of ultrafiltered volume.

Total body water measurement by a modification of the bioimpedance spectroscopy method.

Nous proposons une m&eacute;thode pour calculer directement totale du corps (V (t)) de r&eacute;sistance de l&#39;organisme entier extrapol&eacute;e &agrave; fr&eacute;quence infinie (R (infini)) &agrave; l&#39;aide d&#39;un imp&eacute;dancem&egrave;tre XITRON 4200 de volumes d&#39;eau (TBW). Moyenne des r&eacute;sistivit&eacute;s TBW pour hommes et femmes ont &eacute;t&eacute; d&eacute;termin&eacute;es &agrave; partir des mesures de R (infini) et de la masse sans gras (mesur&eacute;e par DXA dans 58 sujets sains, en supposant un coefficient moyen d&#39;hydratation de 73,2 % de FFM(d)). Les diff&eacute;rences moyennes entre V (t) mesur&eacute;e par notre nouvelle m&eacute;thode et celles d&eacute;duites de donn&eacute;es DXA &eacute;taient + 0,11 +/-1,61 L pour les femmes et + 0,13 +/-2,16 L pour les hommes. Pour la validation, cette m&eacute;thode a &eacute;t&eacute; test&eacute;e avec les r&eacute;sistivit&eacute;s m&ecirc;mes contre un 2&egrave;me groupe de 16 volontaires et la diff&eacute;rence moyenne entre V (t) d&#39;imp&eacute;dance et DXA a &eacute;t&eacute; -0,80 +/-1,43 L. Comme la r&eacute;sistance &agrave; 50 kHz (R (50)) s&#39;est av&eacute;r&eacute;e pour &ecirc;tre &eacute;gal, en moyenne, &agrave; 1.230 R (infini) pour les hommes et 1,223 R (infini) pour les femmes, cette m&eacute;thode peut &eacute;galement &ecirc;tre appliqu&eacute;e &agrave; 50 kHz avec une pr&eacute;cision similaire en estimant R (infini) de R (50). Lorsque notre nouvelle m&eacute;thode a &eacute;t&eacute; appliqu&eacute;e &agrave; la surveillance d&#39;eau perte pendant la dialyse 28 runs effectu&eacute;e sur 13 patients, il pr&eacute;dit une perte d&#39;eau moyenne &eacute;gale &agrave; 94 % du volume d&#39;ultrafiltr&eacute;.

Mesure de l&#39;eau corporelle totale par une modification de la m&eacute;thode de spectroscopie de bioimp&eacute;dance.

Vi proponiamo un metodo per calcolare direttamente total body volumi di acqua (TBW) (V (t)) da tutto il corpo resistenza estrapolati a frequenza infinita (R (infinito)) utilizzando un misuratore di impedenza Xitron s 4200. Dire resistivities TBW per uomini e donne sono state determinate dalle misure di R (infinito) e priva di grassi massa (misurata da DXA in 58 soggetti sani, assumendo un coefficiente medio di idratazione del 73,2% FFM(d)). Medie differenze tra V (t) misurata dal nostro nuovo metodo e quelli desunti da dati DXA erano +0.11 + /-L 1,61 per le donne e +0.13 + 2,16 L per gli uomini. Per la convalida, questo metodo &egrave; stato testato con la stessa resistivities contro un secondo gruppo di 16 volontari e la differenza media tra V (t) dall&#39;impedenza e DXA &egrave; stato-0.80 + 1,43 L. Poich&eacute; la resistenza a 50 kHz (R (50)) &egrave; stata trovata per essere uguale, in media, a 1.230 R (infinito) per gli uomini e 1.223 R (infinito) per le donne, questo metodo pu&ograve; anche essere applicato a 50 kHz con una precisione simile stimando R (infinito) da R (50). Quando il nostro nuovo metodo &egrave; stato applicato al monitoraggio dell&#39;acqua perdita durante la dialisi 28 va eseguita su 13 pazienti, predisse una perdita media dell&#39;acqua pari al 94% del volume di ultrafiltrato.

Misurazione di acqua totale del corpo da una modifica del metodo di spettroscopia di bioimpedenza.

Proponemos un m&eacute;todo para calcular directamente cuerpo vol&uacute;menes de agua (TBW) (V (t)) de resistencia de cuerpo entero extrapoladas a frecuencia infinita (R (infinito)) usando un medidor de impedancia de XITRON 4200. Significa resistividades TBW para hombres y mujeres se determinaron a partir de mediciones de R (infinito) y masa libre de grasa (medido por DXA en sujetos sanos 58 suponiendo un coeficiente de hidrataci&oacute;n promedio de 73,2% de FFM(d)). Las diferencias de medias entre V (t) medido por nuestro nuevo m&eacute;todo y los deducen datos DXA fueron 0.11 +/-1,61 L para las mujeres y +0.13 +/-2,16 L para los hombres. Para la validaci&oacute;n, este m&eacute;todo fue probado con las mismas resistencias contra un segundo grupo de 16 voluntarios y la diferencia de medias entre V (t) de impedancia y DXA fue-0.80 + /-1,43 L. Puesto que la resistencia a 50 kHz (R (50)) fue encontrada para ser igual, en promedio, a 1.230 R (infinito) para los hombres y 1.223 R (infinito) para las mujeres, este m&eacute;todo puede aplicarse tambi&eacute;n a 50 kHz con una exactitud similar al estimar R (infinito) de R (50). Cuando nuestro nuevo m&eacute;todo se aplic&oacute; a la supervisi&oacute;n de agua p&eacute;rdida durante di&aacute;lisis 28 ejecuta realizada en 13 pacientes, predijo que una p&eacute;rdida de agua media igual a 94% del volumen de ultrafiltrada.

Medici&oacute;n de agua corporal total por una modificaci&oacute;n del m&eacute;todo de espectroscopia de bioimpedancia.

Power Doppler imaging (PDI) has been shown to be influenced by the wall filter when assessing arterial stenoses. Real-time 3-D Doppler imaging may likely become a widespread practice in the near future, but how the wall filter could affect PDI during the cardiac cycle has not been investigated. The objective of the study was to demonstrate that the wall filter may produce unexpected major signal losses in real-time 3-D PDI. To test our hypothesis, we first validated binary images obtained from analytical simulations with in vitro PDI acquisitions performed in a tube under pulsatile flow conditions. We then simulated PDI images in the presence of a severe stenosis, considering physiological conditions by finite element modeling. Power Doppler imaging simulations revealed important signal losses within the lumen area at different instants of the flow cycle, and there was a very good concordance between measured and predicted PDI binary images in the tube. Our results show that the wall filter may induce severe PDI signal losses that could negatively influence the assessment of vascular stenosis. Clinicians should therefore be aware of this cause of signal loss to properly interpret power Doppler angiographic images.

Signal losses with real-time three-dimensional power Doppler imaging.

Puissance Doppler imaging (PDI) s&#39;est av&eacute;r&eacute; &ecirc;tre influenc&eacute; par le filtre du mur lors de l&#39;&eacute;valuation des st&eacute;noses art&eacute;rielles. Imagerie Doppler 3D en temps r&eacute;el peut vraisemblablement devenir une pratique r&eacute;pandue dans un proche avenir, mais comment le filtre mural pourrait affecter les PDI au cours du cycle cardiaque n&#39;a pas &eacute;t&eacute; &eacute;tudi&eacute;e. L&#39;objectif de l&#39;&eacute;tude &eacute;tait de d&eacute;montrer que le filtre mural peut produire des pertes de signal majeur inattendu dans PDI 3D en temps r&eacute;el. Pour tester notre hypoth&egrave;se, nous avons tout d&#39;abord valid&eacute; images binaires obtenus &agrave; partir des simulations analytiques avec in vitro PDI acquisitions effectu&eacute;es dans un tube dans des conditions de flux pulsatile. Ensuite, nous avons simul&eacute; images PDI en pr&eacute;sence d&#39;une st&eacute;nose s&eacute;v&egrave;re, compte tenu des conditions physiologiques de la mod&eacute;lisation par &eacute;l&eacute;ments finis. Doppler de puissance des simulations d&#39;imagerie a r&eacute;v&eacute;l&eacute; des pertes de signal important au sein de la zone de lumen &agrave; diff&eacute;rents moments du cycle du flux, et il y avait une tr&egrave;s bonne concordance entre mesur&eacute;es et pr&eacute;dites images de binaires PDI dans le tube. Nos r&eacute;sultats montrent que le filtre mural peut induire de graves pertes de signal PDI qui pourraient influer n&eacute;gativement sur l&#39;&eacute;valuation de la st&eacute;nose vasculaire. Cliniciens devraient donc &ecirc;tre au courant de cette cause de perte de signal pour interpr&eacute;ter correctement les images angiographiques Doppler de puissance.

Pertes de signal avec en temps r&eacute;el en trois dimensions de puissance Doppler imaging.

Power Doppler imaging (PDI) ha dimostrato di essere influenzato dal filtro di parete quando valutare stenosi arteriose. Imaging Doppler 3D in tempo reale probabilmente pu&ograve; diventare una pratica diffusa nel prossimo futuro, ma come il filtro di parete potrebbe influenzare PDI durante il ciclo cardiaco non &egrave; stato studiato. L&#39;obiettivo dello studio era quello di dimostrare che il filtro di parete pu&ograve; produrre perdite di segnale imprevisto principali in tempo reale 3D PDI. Per testare la nostra ipotesi, abbiamo convalidato prima immagini binarie ottenute da simulazioni analitiche con acquisizioni di PDI in vitro eseguiti in un tubo in condizioni di flusso pulsatile. Abbiamo quindi simulato immagini PDI in presenza di una stenosi grave, considerando le condizioni fisiologiche di modellazione agli elementi finiti. Power Doppler imaging simulazioni hanno rivelato le perdite di segnale importante all&#39;interno dell&#39;area di lume a diversi momenti del ciclo del flusso, e c&#39;era una buona concordanza tra misurate e prevedibili immagini binarie PDI nel tubo. I nostri risultati mostrano che il filtro di parete pu&ograve; indurre gravi perdite di segnale PDI che potrebbero influenzare negativamente la valutazione delle stenosi vascolare. I medici dovrebbero quindi essere consapevoli di questa causa di perdita di segnale per interpretare correttamente power Doppler angiografica immagini.

Perdite di segnale con tempo reale tridimensionale power Doppler imaging.

Energ&iacute;a Doppler imaging (PDI) se ha demostrado para ser influenciado por el filtro de la pared al evaluar las estenosis arteriales. Imagen Doppler 3D en tiempo real puede probablemente se convierta en una pr&aacute;ctica generalizada en un futuro pr&oacute;ximo, pero como el filtro de pared podr&iacute;a afectar PDI durante el ciclo card&iacute;aco no se ha investigado. El objetivo del estudio fue demostrar que el filtro de la pared puede producir p&eacute;rdidas de se&ntilde;al importante inesperada en PDI 3D en tiempo real. Para probar nuestra hip&oacute;tesis, primero validamos im&aacute;genes binarias de simulaciones anal&iacute;ticas con adquisiciones de PDI in vitro realizados en un tubo bajo condiciones de flujo puls&aacute;til. Nosotros entonces PDI im&aacute;genes simuladas en presencia de una estenosis severa, teniendo en cuenta las condiciones fisiol&oacute;gicas de modelado de elementos finitos. Energ&iacute;a Doppler imaging simulaciones revel&oacute; p&eacute;rdidas de se&ntilde;al importante dentro de la zona de luz en diferentes momentos del ciclo de flujo, y hubo una muy buena concordancia entre medidas y predijo im&aacute;genes binarias de PDI en el tubo. Nuestros resultados muestran que el filtro de la pared puede inducir graves p&eacute;rdidas de se&ntilde;al PDI que podr&iacute;an influir negativamente en la evaluaci&oacute;n de estenosis vascular. Por lo tanto, los cl&iacute;nicos deben ser conscientes de esta causa de p&eacute;rdida de se&ntilde;al para interpretar adecuadamente el poder las im&aacute;genes angiogr&aacute;ficas Doppler.

P&eacute;rdidas de se&ntilde;al con en tiempo real tridimensionales energ&iacute;a a Doppler imaging.

To elucidate the relationship between microscopic red blood cell (RBC) interactions and macroscopic rheological behavior, we propose a two-dimensional particle model capable of mimicking the main characteristics of RBC aggregation kinetics. The mechanical model of RBCs sheared in Couette flow is based on Newton law. We assumed a hydrodynamic force to move particles, a force to describe aggregation and an elasticity force. The role of molecular mass and concentration of neutral polymers on aggregation [Neu, B., and H. J. Meiselman. Biophys. J. 83:2482-2490, 2002] could be mimicked. Specifically, it was shown that for any shear rate (SR), the mean aggregate size (MAS) grew with time until it reached a constant value, which is consistent with in vitro experiments. It was also demonstrated that we could mimic the modal relationship between MAS and SR and the occurrence of maximum aggregation at about 0.1 s(-1). As anticipated, simulations indicated that an increase in aggregation force augmented MAS. Further, augmentation of the depletion layer thickness influenced MAS only for SR close to zero, which is a new finding. To conclude, our contribution reveals that the aggregation force intensity and SR influence the steady state MAS, and that the depletion and layer thickness affect the aggregation speed.

A particle dynamic model of red blood cell aggregation kinetics.

Afin d&#39;&eacute;lucider la relation entre les interactions microscopiques des globules rouges (RBC) et comportement rh&eacute;ologique macroscopique, nous proposons un mod&egrave;le de particule bidimensionnel capable d&#39;imiter les principales caract&eacute;ristiques de la cin&eacute;tique de l&#39;agr&eacute;gation de RBC. Le mod&egrave;le m&eacute;canique de globules rouges cisaill&eacute; en &eacute;coulement de Couette repose sur la Loi de Newton. Nous avons suppos&eacute; une force hydrodynamique pour d&eacute;placer des particules, une force pour d&eacute;crire l&#39;agr&eacute;gation et une force de l&#39;&eacute;lasticit&eacute;. Le r&ocirc;le de la masse mol&eacute;culaire et de la concentration des polym&egrave;res neutres sur l&#39;agr&eacute;gation [Neu, B. et H. J. Meiselman. Biophys. J. 83:2482-2490, 2002] pourrait &ecirc;tre imit&eacute;. Plus pr&eacute;cis&eacute;ment, il a &eacute;t&eacute; d&eacute;montr&eacute; que pour n&#39;importe quel taux de cisaillement (SR), la taille moyenne globale (MAS) a augment&eacute; avec le temps jusqu&#39;&agrave; ce qu&#39;il atteigne une valeur constante, ce qui concorde avec les exp&eacute;riences in vitro. On a &eacute;galement d&eacute;montr&eacute; que nous pouvions imitent les relations modales entre MAS et SR et l&#39;apparition d&#39;agr&eacute;gation maximale au sujet de 0,1 s(-1). Comme pr&eacute;vu, les simulations ont montr&eacute; qu&#39;une augmentation de la force de l&#39;agr&eacute;gation augment&eacute;e MAS. Augmentation de l&#39;&eacute;paisseur de couche de d&eacute;pl&eacute;tion influence &eacute;galement MAS que pour SR proche de z&eacute;ro, ce qui est un nouveau verdict. Pour conclure, notre contribution r&eacute;v&egrave;le que l&#39;agr&eacute;gation force intensit&eacute; et influence SR les MAS de l&#39;&eacute;tat d&#39;&eacute;quilibre, et que l&#39;&eacute;paisseur de l&#39;appauvrissement de la couche et couche affecte la vitesse de l&#39;agr&eacute;gation.

Un mod&egrave;le dynamique de la particule de cin&eacute;tique d&#39;agr&eacute;gation des globules rouges.

Per chiarire il rapporto tra interazioni microscopiche di globuli rossi (RBC) e comportamento reologico macroscopico, proponiamo un modello bidimensionale della particella capace di mimando le principali caratteristiche di cinetica di aggregazione di RBC. Il modello meccanico di globuli rossi rotti nel flusso di Couette &egrave; basato sulla legge di Newton. Abbiamo assunto una forza idrodinamica per spostare particelle, una forza per descrivere aggregazione e una forza di elasticit&agrave;. Il ruolo della massa molecolare e concentrazione dei polimeri neutri di aggregazione [Neu, B. e H. J. Meiselman. Biophys. J. 83:2482-2490, 2002] potrebbe essere imitato. In particolare, &egrave; stato dimostrato che per qualsiasi shear rate (SR), la pezzatura media (MAS) &egrave; cresciuta con il tempo fino a raggiungere un valore costante, che &egrave; coerenza con gli esperimenti in vitro. &Egrave; stato anche dimostrato che noi potremmo imitare il rapporto modale tra MAS e SR e la comparsa di massima aggregazione a circa 0.1 s(-1). Come anticipato, simulazioni indicato che un aumento della forza di aggregazione aumentata MAS. Aumento di spessore dello strato di impoverimento influenzato ulteriormente, MAS solo per SR vicino allo zero, che &egrave; una nuova scoperta. Per concludere, il nostro contributo rivela che l&#39;aggregazione forza SR influenza il MAS stazionario e intensit&agrave;, e che la deplezione e strato di spessore possono influenzare la velocit&agrave; di aggregazione.

Un modello dinamico della particella di cinetica di aggregazione di globuli rossi.

Para aclarar la relaci&oacute;n entre las interacciones microsc&oacute;picas de gl&oacute;bulos rojos (RBC) y comportamiento reol&oacute;gico macrosc&oacute;pico, proponemos un modelo de dos dimensiones de la part&iacute;cula capaz de imitar las caracter&iacute;sticas principales de la cin&eacute;tica de la agregaci&oacute;n de RBC. El modelo mec&aacute;nico de gl&oacute;bulos rojos cortado en flujo de Couette se basa en la ley de Newton. Asumimos una fuerza hidrodin&aacute;mica para mover las part&iacute;culas, una fuerza para describir la agregaci&oacute;n y una fuerza de la elasticidad. El papel de masa molecular y concentraci&oacute;n de pol&iacute;meros neutros en agregaci&oacute;n [Neu, B. y H. J. Meiselman. Biophys. J. 83:2482-2490, 2002] podr&iacute;a m&iacute;mico. Espec&iacute;ficamente, se comprob&oacute; que para cualquier tasa de corte (SR), la talla media de agregado (MAS) creci&oacute; con el tiempo hasta alcanzar un valor constante, que concuerda con los experimentos in vitro. Tambi&eacute;n se demostr&oacute; que podr&iacute;amos imitar la relaci&oacute;n modal entre el MAS y el SR y la ocurrencia de m&aacute;xima agregaci&oacute;n en acerca de 0.1 s(-1). Seg&uacute;n lo previsto, simulaciones indicaron que un aumento en la fuerza de agregaci&oacute;n hab&iacute;a aumentada a MAS. Adem&aacute;s, aumento del espesor de capa de agotamiento hab&iacute;a influenciado a MAS solo para SR cercano a cero, que es un nuevo hallazgo. Para concluir, nuestra contribuci&oacute;n revela que la agregaci&oacute;n fuerza de intensidad y SR influencia el MAS de estado estacionario, y que el grueso de agotamiento y de la capa afecta a la velocidad de agregaci&oacute;n.

Un modelo din&aacute;mico de la part&iacute;cula de la cin&eacute;tica de la agregaci&oacute;n de gl&oacute;bulos rojos.

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) 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 (&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;.

Precisione di misura di velocit&agrave; in microhemodynamics ottico: esperimento e simulazione.

It is desired to understand the effect of alginic acid sodium salt from brown algae (alginate) as a viscosity modifier on the behavior of blood in vitro using a micro-particle image velocimetry (µPIV) system. The effect of alginate on the shape of the velocity profile, the flow rate and the maximum velocity achieved in rectangular microchannels channels are measured. The channels were constructed of polydimethylsiloxane (PDMS), a biocompatible silicone. Porcine blood cells suspended in saline was used as the working fluid at twenty percent hematocrit (H = 20). While alginate was only found to have minimal effect on the maximum velocity and the flow rate achieved, it was found to significantly affect the shear rate at the wall by between eight to a hundred percent.

An analytic study on the effect of alginate on the velocity profiles of blood in rectangular microchannels using microparticle image velocimetry.

High speed photography in micro-particle image velocimetry (μPIV) using red blood cells as tracer particles and the use of fluorescing tracer particles (in conjunction with pulsed images) are directly compared by using both methods simultaneously. Measurements are taken on the same blood sample in the same microchip using both methods. This work directly and statistically compares the two methods of μPIV measurement in a controlled in vitro environment for the first time in literature. The pulsed method using fluorescing tracer particles is found to decrease the depth of correlation as expected, and to better represent the shape of the velocity profile. Two methods of velocity characterization are used (single and double parameter) and the pulsed images provide better shape representation in both cases.

High speed versus pulsed images for micro-particle image velocimetry: a direct comparison of red blood cells versus fluorescing tracers as tracking particles.

Marianne Fenech

Department of Chemical and Biological Engineering

University of Ottawa

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

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation