Letteratura scientifica selezionata sul tema "Blood perfusion rate"
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Articoli di riviste sul tema "Blood perfusion rate"
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Arkin, H., M. M. Chen e K. R. Holmes. "Adaptive Thermal Modeling: A Concept for Measurement of Local Blood Perfusion in Heated Tissues". Journal of Biomechanical Engineering 108, n. 4 (1 novembre 1986): 306–11. http://dx.doi.org/10.1115/1.3138619.
Testo completoAbstract (sommario):
A new Adaptive Thermal Modeling (ATM) method for the measurement of local tissue blood perfusion rate is introduced. The method is based on a two-phase numerical technique. The first phase includes a fast, finite difference scheme for solution of the transient temperature field. The second phase involves iterative corrections of the perfusion until the modeled temperatures coincide with those measured by the temperature sensors. The results obtained from computer generated “data”, as well as from laboratory experiments demonstrate the potential capability of the ATM method to continuously measure local perfusion rates in heated tissues. Rigorous analysis of the technique is planned for the near future so that it can be applied to in vivo measurements of local tissue blood perfusions.
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ZHANG, ZE-WEI, HUI WANG e QING-HUA QIN. "METHOD OF FUNDAMENTAL SOLUTIONS FOR NONLINEAR SKIN BIOHEAT MODEL". Journal of Mechanics in Medicine and Biology 14, n. 04 (3 luglio 2014): 1450060. http://dx.doi.org/10.1142/s0219519414500602.
Testo completoAbstract (sommario):
In this paper, the method of fundamental solution (MFS) coupling with the dual reciprocity method (DRM) is developed to solve nonlinear steady state bioheat transfer problems. A two-dimensional nonlinear skin model with temperature-dependent blood perfusion rate is studied. Firstly, the original bioheat transfer governing equation with nonlinear term induced by temperature-dependent blood perfusion rate is linearized with the Taylor's expansion technique. Then, the linearized governing equation with specified boundary conditions is solved using a meshless approach, in which the DRM and the MFS are employed to obtain particular and homogeneous solutions, respectively. Several numerical examples involving linear, quadratic and exponential relations between temperature and blood perfusion rate are tested to verify the efficiency and accuracy of the proposed meshless model in solving nonlinear steady state bioheat transfer problems, and also the sensitivity of coefficients in the expression of temperature-dependent blood perfusion rate is analyzed for investigating the influence of blood perfusion rate to temperature distribution in skin tissues.
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Usui, A., T. Hotta, M. Hiroura, M. Murase, M. Maeda, T. Koyama, M. Tanaka, E. Takeuchi e T. Abe. "Cerebral Metabolism and Function during Normothermic Retrograde Cerebral Perfusion". Cardiovascular Surgery 1, n. 2 (aprile 1993): 107–12. http://dx.doi.org/10.1177/096721099300100204.
Testo completoAbstract (sommario):
Retrograde cerebral perfusion through a superior vena cava (SVC) cannula is a new technique used to protect the brain during circulatory arrest. Cerebral blood flow, oxygen consumption, blood sugar consumption and auditory brain stem responses were measured at various rates (100, 200 and 300 ml min−1) of retrograde cerebral perfusion in normothermic mongrel dogs ( n = 12, body-weight 13–15 kg). During perfusion about 20% of the perfusate from the SVC was returned via the aorta, while the rest drained into the inferior vena cava. External jugular venous pressure increased as the perfusion rate increased (mean(s.d.) 26.0(6.4) mmHg at a rate of perfusion of 300 ml min−1). Oxygen and blood sugar consumption also increased as the rate of perfusion increased. Retrograde cerebral perfusion at 300 ml min−1 provided half of the cerebral blood flow (mean(s.d.) 14.7(6.4) versus 34.3(7.8)ml min−1) of antegrade cardiopulmonary bypass (CPB). Analysis of the blood returned through the aorta during perfusion at a rate of 300 ml min−1 showed that mean(s.d.) oxygen consumption was about one-third (4.4(2.1) versus 12.3(7.1) ml min−1) and blood sugar consumption about 15% (17(22) versus 114(54) mg min−1) of that seen in blood returned through the SVC during CPB. Auditory brain stem responses disappeared immediately when perfusion was started but recovered completely as soon as CPB was resumed. Although the oxygen provided by perfusion was not sufficient to maintain cerebral function, it should help protect the brain during circulatory arrest.
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Lama Moktan, Sushila, e Manan Karki. "Comparison of non-invasive haemodynamic monitors of stress response to endo-tracheal intubation with perfusion index in patients undergoing elective surgery". Journal of Society of Surgeons of Nepal 23, n. 2 (31 dicembre 2020): 9–13. http://dx.doi.org/10.3126/jssn.v23i2.35797.
Testo completoAbstract (sommario):
Introduction: Laryngoscopy and intubation is always associated with a short term reflex sympathetic pressor response. The perfusion index is an indirect, non-invasive, and continuous measure of peripheral perfusion by pulse oximeter which can detect the stress response to intubation similar to heart rate, systolic blood pressure and diastolic blood pressure.
Methods: This prospective observational study enrolled sixty-five normotensive patients of American society of anesthesiologists physical status grade I and II scheduled for elective surgery under general anaesthesia. Tracheal intubation was performed after induction with intravenous fentanyl, propofol and vecuronium. Heart rate, Systolic and Diastolic Blood Pressure and Perfusion Index were measured before induction of anesthesia, before intubation and one minute, three minutes, five minutes after the insertion of the endotracheal tube. Increase in heart rate by ?10 beats per minute, systolic and diastolic blood pressure by ?15 millimeters of mercury and decrease in Perfusion index ?10% after endotracheal intubation as compared to preintubationvalue were considered positive haemodynamic changes.
Results: Endotracheal intubation produced a significant increase in heart rate and blood pressure whereas perfusion index decreased significantly. Our study showed that perfusion index response criterion achieved 97.7% (Confidence interval 97.58-97.86) sensitivity in detecting the stress response to insertion of endotracheal tube whereas systolic and diastolic blood pressure achieved sensitivity of 90% and 92% respectively.
Conclusion: Perfusion Index is easier, reliable and non-invasive alternative to conventional haemodynamic criteria for detection of stress response to endotracheal intubation.
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pennati, giancarlo, francesco migliavacca, francesca gervaso e gabriele dubini. "assessment by computational and in vitro studies of the blood flow rate through modified blalock-taussig shunts". Cardiology in the Young 14, S3 (ottobre 2004): 24–29. http://dx.doi.org/10.1017/s1047951104006511.
Testo completoAbstract (sommario):
surgical repairs of many severe congenital cardiac malformations, such as the procedures used to redirect the flow of blood in the setting of absent or suboptimal perfusions, are performed either using direct vascular anastomosis, or by the insertion of interpositioned prosthetic shunts. examples of these applications can be found when considering those cardiac malformations characterized by the common physiological feature of having a single pumping ventricle, usually due to the incomplete and rudimentary form of the complementary ventricle. in this situation, since the circulation depends on the functionally single ventricle, pulmonary perfusion can be derived from the systemic circulation through a synthetic tube (gore-tex®, falstaff, az, usa), usually connected between the brachiocephalic or subclavian arteries and the right or left pulmonary arteries. this arrangement is called the modified blalock-taussig shunt (fig. 1, left). the effect is to produce parallel circulations (fig. 1, right). survival at this stage is closely dependent on the balance between systemic and pulmonary flows, and thus on the fluid-dynamics through the interposition shunt, which is often the sole source of pulmonary perfusion.
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MacLean, David A., Lisa M. Vickery e Lawrence I. Sinoway. "Elevated interstitial adenosine concentrations do not activate the muscle reflex". American Journal of Physiology-Heart and Circulatory Physiology 280, n. 2 (1 febbraio 2001): H546—H553. http://dx.doi.org/10.1152/ajpheart.2001.280.2.h546.
Testo completoAbstract (sommario):
The purpose of the present study was to examine the effects of adenosine perfusion of the isolated triceps surae muscle group in the decerebrate cat on interstitial adenosine concentrations as well as heart rate and blood pressure responses. In six male cats (6.0 ± 0.21 kg), the triceps surae muscle group of both legs was perfused with an artificial blood solution containing no additives (control) and then with blood containing 20 mM or 100 μM adenosine for 10 min. An intact muscle reflex was confirmed by bolus injections of 50 mM phosphate and/or saturated KCl administered into the triceps surae muscle via the cannulated popliteal artery before and after adenosine blood perfusion. Microdialysis of the triceps surae muscle group during muscle perfusion revealed that interstitial adenosine was elevated ( P < 0.05) from 0.9 ± 0.3 μM during control blood perfusion to 2,421 ± 547 μM during 20 mM adenosine perfusion. In addition, interstitial adenosine levels were increased ( P < 0.05) from 1.1 ± 0.3 μM during control blood perfusion to 4.1 ± 1.2 μM during perfusion with 100 μM adenosine. Despite the large increases in interstitial adenosine levels, perfusion of the triceps surae muscle group with the two blood adenosine solutions resulted in no significant increases in heart rate or blood pressure. These data strongly suggest that elevated interstitial adenosine concentrations do not play a role in activating the muscle reflex and confirm our previous in vivo human findings ( J Appl Physiol 83: 1045–1053, 1997).
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Murakami, Hideyasu, Hitomi Takanaga, Hirotami Matsuo, Hisakazu Ohtani e Yasufumi Sawada. "Comparison of blood-brain barrier permeability in mice and rats using in situ brain perfusion technique". American Journal of Physiology-Heart and Circulatory Physiology 279, n. 3 (1 settembre 2000): H1022—H1028. http://dx.doi.org/10.1152/ajpheart.2000.279.3.h1022.
Testo completoAbstract (sommario):
Here we present a method for measuring the permeability coefficient-surface area product ( PS) values at the blood-brain barrier in mice, using the in situ brain perfusion technique originally developed for rats by Takasato et al. ( Am J Physiol Heart Circ Physiol 247: H484–H493, 1984). Retrograde infusion into the right external carotid artery increased the carotid perfusion pressure in proportion to the perfusion rate. Intravascular volume and cerebral perfusion fluid flow at a perfusion rate of 1.0 ml/min in mice were similar to those in rats. In addition, the contribution of systemic blood to total flow in the hemisphere was small (only 3.2%). These findings indicated that this perfusion rate is suitable for mice. The PS values of more than 20 different compounds were determined in mice by using the in situ brain perfusion technique, and comparisons were made with data from rats. There was a close relationship (1:1) between the PS values in mice and rats, indicating that brain capillary permeabilities are similar in mice and rats.
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Ajcharanukul, O., E. Chunhacheevachaloke, P. Vorachart e W. Chidchuangchai. "The Postural Autonomic Regulation of Pulpal Blood Flow". Journal of Dental Research 92, n. 2 (19 novembre 2012): 156–60. http://dx.doi.org/10.1177/0022034512469025.
Testo completoAbstract (sommario):
Evidence suggests that postural changes in systemic blood pressure may significantly affect blood flow in the dental pulp. This in vivo study examined the responses of pulpal perfusion, systemic blood pressure, and heart rate to postural changes in humans. The experiments were done on 21 premolars in 16 participants aged 20-31 yrs. Pulpal blood flow recordings were measured by means of a laser Doppler Flowmeter. A blood pressure monitor was used to record blood pressure and heart rate. All measurements were simultaneously recorded for 1 min, 5 min after participants made postural changes. Changing from supine to standing caused a significant reduction in pulpal perfusion, while heart rate and diastolic blood pressure increased significantly. A significant non-linear relationship was found between percentage changes in pulpal perfusion and heart rate resulting from standing up. We speculate that when patients arise from the supine position, the shift in venous blood to the legs transiently (2-10 sec) lowers venous return and cardiac output, causing less inhibition of the vasomotor center, which, in turn, results in increased heart rate and blood pressure, but a decrease in pulpal blood flow. These results suggest that pulpal blood flow is affected by postural change, presumably via the autonomic nervous system.
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Ohlsson, J., M. Middaugh e M. P. Hlastala. "Reduction of lung perfusion increases VA/Q heterogeneity". Journal of Applied Physiology 66, n. 5 (1 maggio 1989): 2423–30. http://dx.doi.org/10.1152/jappl.1989.66.5.2423.
Testo completoAbstract (sommario):
This study addresses the hypothesis that decreases in lung perfusion rate independently worsen gas exchange efficiency in an isolated left lower lobe in zone 2 conditions. In seven anesthetized dogs, the left lower lobe was isolated, leaving the bronchus and bronchial vasculature intact. Blood was taken from the femoral arteries and reinfused at a controlled rate into the pulmonary artery of the left lower lobe. The flow rate was varied between 100 and 400 ml/min. The multiple inert gas elimination technique was used to quantitate the matching of ventilation to perfusion. Reduction in lobe blood flow resulted in a significant increase in perfusion-related indexes of alveolar ventilation-perfusion heterogeneity, such as the log standard deviation of the perfusion distribution, the retention component of the arterial-alveolar difference area, and the retention dispersion index. The increased heterogeneity suggests a worsening of the intraregional matching between the ventilation and the perfusion when perfusion is less than normal.
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Badimon, L., JJ Badimon, VT Turitto e V. Fuster. "Role of von Willebrand factor in mediating platelet-vessel wall interaction at low shear rate; the importance of perfusion conditions". Blood 73, n. 4 (1 marzo 1989): 961–67. http://dx.doi.org/10.1182/blood.v73.4.961.961.
Testo completoAbstract (sommario):
Abstract We have previously observed that von Willebrand factor (vWF) plays an important role in platelet deposition on subendothelium at low values of wall shear rate (200 to 400 seconds-1). In the present study, we have investigated the mechanism responsible for such a defect in platelet deposition at low shear rates in the absence of vWF. Blood from both normal and von Willebrand's disease (vWD) animals was exposed to de-endothelialized aorta from normal pigs for a range of shear rates (200 to 3,000 seconds-1) and exposure times (three to 30 minutes) in a tubular perfusion chamber. Variations in the method of inhibiting coagulation (none, heparin, citrate, hirudin, and EDTA) and of perfusing blood (in vitro v ex vivo) were compared by determining the influence of wall shear rate and vWF on the deposition of 111In-labeled platelets on subendothelium. Whereas platelet deposition was reduced in the absence of vWF for all experimental variations at high shear rates (greater than 850 seconds-1), a defect was observed at low shear rates only when heparinized blood was exposed by means of an ex vivo perfusion system. Maximum sensitivity of the measurement occurs under ex vivo perfusion conditions due to the reduced ability of platelets to deposit in normal blood when recirculated in vitro. Our results indicate that vWF mediates platelet-vessel wall interaction even at low shear rates and that such effect can only be observed in systems where platelet function is minimally affected by the experimental conditions.
Tesi sul tema "Blood perfusion rate"
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Zakhour, Elias Carleton University Dissertation Physics. "Determination of thermal dose and blood perfusion rate from clinical data". Ottawa, 1990.
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Fournet, Gabrielle. "IVIM : modeling, experimental validation and application to animal models". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS367/document.
Testo completoAbstract (sommario):
Cette thèse porte sur l’étude de la séquence d’imagerie IRM IVIM (« Intravoxel incoherent motion »). Cette séquence permet l’étude des microvaisseaux sanguins tels que les capillaires, artérioles et veinules. Pour être sensible seulement aux groupes de spins non statiques dans les tissus, des gradients de diffusion sont ajoutés avant et après l’impulsion 180° d’une séquence d’écho de spin. La composante du signal correspondant aux spins qui diffusent dans le tissu peut être séparée de celle des spins en mouvement dans les vaisseaux sanguins qui est appelée signal IVIM. Ces deux composantes sont pondérées par f IVIM qui représente la fraction volumique du sang à l’intérieur du tissu. Le signal IVIM est en général modélisé par une fonction mono-exponentielle (ME) caractérisée par un coefficient de pseudo-diffusion D*. Nous proposons un modèle IVIM bi-exponentiel formé d’une composante lente caractérisée F slow et D* slow qui correspondrait aux capillaires comme dans le modèle ME, et d’une composante rapide caractérisée par F fast et D* fast qui correspondrait à des vaisseaux plus gros comme des artérioles et veinules. Ce modèle a été validé expérimentalement et des informations supplémentaires ont été obtenues en comparant les signaux expérimentaux avec un dictionnaire de signaux IVIM simulés numériquement. L’influence de la séquence d’impulsions, du temps de répétition et du temps d’encodage de diffusion a également été étudiée. Enfin, la séquence IVIM a été appliquée à l’étude d’un modèle animal de la maladie d’AlzheimerThis PhD thesis is centered on the study of the IVIM (“Intravoxel Incoherent Motion”) MRI sequence. This sequence allows for the study of the blood microvasculature such as the capillaries, arterioles and venules. To be sensitive only to moving groups of spins, diffusion gradients are added before and after the 180° pulse of a spin echo (SE) sequence. The signal component corresponding to spins diffusing in the tissue can be separated from the one related to spins travelling in the blood vessels which is called the IVIM signal. These two components are weighted by f IVIM which represents the volume fraction of blood inside the tissue. The IVIM signal is usually modelled by a mono-exponential (ME) function and characterized by a pseudo-diffusion coefficient, D*. We propose instead a bi-exponential IVIM model consisting of a slow pool, characterized by F slow and D* slow corresponding to the capillaries as in the ME model, and a fast pool, characterized by F fast and D* fast, related to larger vessels such as medium-size arterioles and venules. This model was validated experimentally and more information was retrieved by comparing the experimental signals to a dictionary of simulated IVIM signals. The influence of the pulse sequence, the repetition time and the diffusion encoding time was also studied. Finally, the IVIM sequence was applied to the study of an animal model of Alzheimer’s disease
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Troalen, Thomas. "IRM quantitative de la perfusion myocardique par marquage de spins artériels = Quantitative myocardial perfusion MRI using arterial spin labeling". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5006/document.
Testo completoAbstract (sommario):
La perfusion est un facteur important dans la viabilité et la fonction du myocarde. Des atteintes microvasculaires diffuses, précédant l'infarctus ou l'insuffisance cardiaque sont impliqués dans bon nombre de pathologies cardiaques. Ce travail vise à améliorer les techniques existantes de mesure quantitatives et non-invasive de la perfusion myocardique par marquage de spins artériels (ASL). La première partie de mon travail de thèse a consisté en la mise place chez la souris d'une technique alternative pour mesurer la perfusion myocardique. Celle-ci est basée sur un marquage pulsé et régulièrement répété afin de construire un état d'équilibre de l'aimantation sous l'influence de la perfusion (approche steady-pulsed ASL). Le modèle théorique associé à cette technique spASL a été développé en parallèle afin de quantifier le flux sanguin tissulaire. Il a été montré que spASL permettait d'obtenir un résultat similaire aux techniques existantes avec en plus, les avantages d'améliorer la sensibilité au signal de perfusion ainsi que de réduire le temps d'acquisition. Dans un second temps, un transfert vers l'imagerie clinique pour une application chez l'homme a été entrepris. Le marquage de type spASL a été conservé et le module de lecture a été adapté aux spécificités de l'imagerie cardiaque chez l'homme pour une acquisition en respiration libre. Un post-traitement dédié qui comprend une correction de mouvement rétrospective a ensuite vu le jour afin d'améliorer la robustesse de nos mesures. Parallèlement aux développements conduits chez l'homme, nous avons exploité l'approche spASL chez l'animal en proposant diverses améliorations en fonction des études menéesMyocardial blood flow is an important factor of tissue viability and function. Diffuse changes in microcirculation preceding heart failure are involved in various cardiac pathologies. This work aim at improving existing techniques allowing quantitative and non-invasive myocardial perfusion assessment using arterial spin labeling. The first step of my work was to design an alternative approach to quantify myocardial blood flow in mice. The so called steady-pulsed ASL (spASL) is based on a regularly repeated pulsed labeling in order to build up a stationary regime of the magnetization under the influence of perfusion. The associated theoretical model has been developed in parallel to quantify tissue blood flow. We have shown that spASL allows to obtain similar results than the previously employed techniques, with the additional advantages of an increased sensitivity to the perfusion signal and a reduced acquisition time. A transfer towards clinical imaging for human applications was then undertaken. The spASL labeling scheme has been preserved while adapting the readout module to the specificities of cardiac MRI when applied to free-breathing human acquisitions. A dedicated post-processing, which includes a retrospective motion correction, has emerged subsequently to improve the robustness of our measurements. In parallel to the developments made for human studies, some optimization of the spASL technique when applied to rodent have been carried out depending on the conducted studies
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Mello, Junior Edgard José Franco [UNESP]. "Avaliação radioisotópica da perfusão de retalhos cutâneos em ilha com descolamento prévio em relação ao músculo subjacente: estudo no rato". Universidade Estadual Paulista (UNESP), 2001. http://hdl.handle.net/11449/88906.
Testo completoAbstract (sommario):
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mellojunior_ejf_me_botfm.pdf: 990226 bytes, checksum: 1942b9c6092e2c3cce62055f3e57a32f (MD5)A integridade da perfusão sangüínea, em áreas previamente descoladas cirúrgica ou acidentalmente, ainda não foi esclarecida de modo satisfatório. Este detalhe é fundamental para o planejamento de retalhos comprometendo estas áreas. Este trabalho teve por objetivo avaliar, em ratos, a perfusão sangüínea em áreas previamente descoladas cirurgicamente, utilizando-se microesferas radioativas. Foram utilizados 48 ratos Wistar, divididos em quatro grupos. O tegumento cutâneo do flanco esquerdo foi descolado e, após 0, 7, 14 e 28 dias, teve sua perfusão sangüínea avaliada por meio de contagem de microesferas radioativas e das contagens dos vasos dérmicos e subdérmicos. Os resultados observados demonstraram maiores valores nos índices retalho/controle obtidos pelas contagens da radiação gama emitida pelas microesferas marcadas com tecnécio-99m, com diâmetro médio de 15 μm, após 7, 14 e 28 dias, quando comparados ao dia zero (p < 0,001, Teste de Kruskal-Wallis). Os índices obtidos pela contagem de vasos sangüíneos por meio de histologia, foram iguais nos quatro grupos. Concluiu-se que, por meio da técnica das microesferas radioativas, foi possível detectar-se a presença de perfusão sangüínea com 7, 14 e 28 dias após o descolamento prévio do tegumento cutâneo em relação ao músculo subjacente e que não houve diferença na contagem dos vasos dérmicos e subdérmicos nos quatro grupos, pelo método histológico.
The integrity of blood perfusion in accidentally or surgically previously detached areas have not been fully explained. This is a fundamental detail for myocutaneous flap arrangement involving these areas. The objective of this work was to evaluate the blood perfusion in a previously surgically detached area, in rats, using radioactive microspheres. Forty-eight Wistar rats, divided into four groups (day 0, 7, 14 and 28) were used. The cutaneous tegument of the left flank was detached and after 0, 6, 14 and 28 days, its blood perfusion was evaluated by counting of radioactive microspheres and dermal and subdermal vessels. The results showed a significant difference in the mean count indexes evaluated by 15 μm diameter radioactive microspheres between the group of day 0 and the other groups, days 7, 14 and 28 (P<0,001). The vessels counting indexes were the same in all of the groups. It was concluded that there is blood perfusion at 7, 14 and 28 days after previous detachment of the cutaneous tegument and there is no significant difference in dermal and subdermal vessels count detected among the four groups.
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Mello, Junior Edgard José Franco. "Avaliação radioisotópica da perfusão de retalhos cutâneos em ilha com descolamento prévio em relação ao músculo subjacente : estudo no rato /". Botucatu : [s.n.], 2001. http://hdl.handle.net/11449/88906.
Testo completoAbstract (sommario):
Resumo: A integridade da perfusão sangüínea, em áreas previamente descoladas cirúrgica ou acidentalmente, ainda não foi esclarecida de modo satisfatório. Este detalhe é fundamental para o planejamento de retalhos comprometendo estas áreas. Este trabalho teve por objetivo avaliar, em ratos, a perfusão sangüínea em áreas previamente descoladas cirurgicamente, utilizando-se microesferas radioativas. Foram utilizados 48 ratos Wistar, divididos em quatro grupos. O tegumento cutâneo do flanco esquerdo foi descolado e, após 0, 7, 14 e 28 dias, teve sua perfusão sangüínea avaliada por meio de contagem de microesferas radioativas e das contagens dos vasos dérmicos e subdérmicos. Os resultados observados demonstraram maiores valores nos índices retalho/controle obtidos pelas contagens da radiação gama emitida pelas microesferas marcadas com tecnécio-99m, com diâmetro médio de 15 μm, após 7, 14 e 28 dias, quando comparados ao dia zero (p < 0,001, Teste de Kruskal-Wallis). Os índices obtidos pela contagem de vasos sangüíneos por meio de histologia, foram iguais nos quatro grupos. Concluiu-se que, por meio da técnica das microesferas radioativas, foi possível detectar-se a presença de perfusão sangüínea com 7, 14 e 28 dias após o descolamento prévio do tegumento cutâneo em relação ao músculo subjacente e que não houve diferença na contagem dos vasos dérmicos e subdérmicos nos quatro grupos, pelo método histológico.Abstract: The integrity of blood perfusion in accidentally or surgically previously detached areas have not been fully explained. This is a fundamental detail for myocutaneous flap arrangement involving these areas. The objective of this work was to evaluate the blood perfusion in a previously surgically detached area, in rats, using radioactive microspheres. Forty-eight Wistar rats, divided into four groups (day 0, 7, 14 and 28) were used. The cutaneous tegument of the left flank was detached and after 0, 6, 14 and 28 days, its blood perfusion was evaluated by counting of radioactive microspheres and dermal and subdermal vessels. The results showed a significant difference in the mean count indexes evaluated by 15 μm diameter radioactive microspheres between the group of day 0 and the other groups, days 7, 14 and 28 (P<0,001). The vessels counting indexes were the same in all of the groups. It was concluded that there is blood perfusion at 7, 14 and 28 days after previous detachment of the cutaneous tegument and there is no significant difference in dermal and subdermal vessels count detected among the four groups.
Orientador: Fausto Viterbo
Coorientador: Beatriz Griva Viterbo
Mestre
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Schönfeld, Stefan Georg. "Dynamische Autoregulation der Nierengefässe von wachen Ratten". Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2004. http://dx.doi.org/10.18452/15092.
Testo completoAbstract (sommario):
An 23 wachen Ratten wurde die dynamische Regulation der Nierengefäße als Antwort auf schwingungsförmige Änderung des renalen Perfusionsdruckes (RPP) gemessen. Es wurden der Renale Perfusionsdruck (RPP), der Nierenarterienfluss (RBF) sowie lokale Gefäßflüsse der Nierenrinde und des äußeren Nierenmark (Laser-Doppler) aufgezeichnet und daraus die entsprechende Conductance (Leitwert) der Gefäße errechnet. Der mittlere RPP wurde rampenförmig mit einer langsamen Änderungsrate gesenkt (dp/dt), wobei nach jeder absteigenden Flanke eine aufsteigende Rampe gleicher Geschwindigkeit gemessen wurde. Eine Überlagerung des RPP mit Schwingungen unterschiedlicher Frequenz (f=0,005, f=0,01 und f=0,02 Hz) bei einer Amplitude von 20 mmHg führte zu einem Anstieg von dp/dt und einem erhöhten Shearstress an der Gefäßwand (WSS). Der Einfluss der Schwingungen auf RCV war signifikant abhängig vom mittleren RPP. So war die Conductance in tieferen Druckbereichen des RPP mehrfach höher als in den Ausgangsdruckwerten. Innerhalb der absteigenden Rampen führte ein Erhöhung der Frequenz zu einem Anstieg der maximalen Amplitude des RVC des Nierengesamtflusses. Die größten Amplituden wurden bei RPP Werten zwischen 58 und 46 mmHg gemessen. Diese Abhängigkeit war bei den ansteigenden Flanken nicht gegeben. Außerdem zeigte sich in den abfallenden Versuchsteilen ein plötzlicher Phasenwechsel zwischen der RPP- und der RVC-Schwingung bei mittleren RPP-Werten zwischen 95 und 80 mmHg. Dies lässt schließen, dass oberhalb dieses Druckwertes aktive myogenen Vasokonstriktion die passiven Gefäßdilatation vollständig ausgleicht, während unterhalb dieses RPP-Wertes die Vasokonstriktion insuffizient reagiert, bis bei ca. 50 mmHg die RCV ausschließlich der passiven Vasodilatation folgt. Höhere Schwingungsfrequenzen führen durch einen Anstieg des WSS zu einer Erhöhung der Amplitude des RVC. Dies bewirkt eine Änderung der charakteristischen renalen Autoregulation des RPP. Auf diese Weise ändert sich die Effizienz der Autoregulation.In 23 conscious rats, the dynamic features of renal vascular conductance (RVC) in response to oscillatory changes in renal perfusion pressure (RPP) were studied at different mean RPPs. RPP, renal blood flow, and regional cortical and outer-medullary fluxes (laser-Doppler) were continuously recorded and the respective RVCs calculated. Mean RPP was changed ramp-wise with a low rate of change (dp/dt), whereby a decremental ramp was immediately followed by an incremental ramp. Superimposing RPP oscillations (amplitude 20 mmHg) of different frequencies (f=0.005, f=0.01, and f=0.02 Hz) increased maximum dp/dt, and thus increased vascular wall shear stress (WSS). The impact of RPP oscillations on RVC critically depended on mean RPP. RVC oscillations were several times higher at lower mean RPPs than at control RPP During the decremental ramps, increasing the frequency led to an increase in the maximum amplitude of total RVC, and decreased mean RPP where maximum amplitude occurred from 58 to 46 mmHg. This frequency dependence was abolished during incremental ramps. Lowering mean RPP resulted in a sudden reversal of phase between RPP and RVC oscillations at mean RPP between 95 and 80 mmHg. It is concluded that, above this RPP, myogenic vasoconstriction fully counterbalances passive vasodilatation, whereas, below that RPP, myogenic constriction gradually tapers off until, at about 50 mmHg, RVC is exclusively determined by passive dilation. Higher oscillatory frequencies, assumed to be due to increased WSS, elicit a greater response in RVC amplitude as an expression of vessel compliance, and, thus change the RPP characteristics of renal autoregulation. However, the efficiency of autoregulation is thereby barely changed.
7
Ying-Ping, Wang, e 王穎平. "The effect of perfusion rate on pulmonary blood flow distribution in isolated rabbit lung". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/00313200848691468070.
Testo completoAbstract (sommario):
碩士國防醫學院
海底醫學研究所
96
中文摘要 低血容性休克是因為全身性有效血量降低，使得心輸出量降低，肺動脈壓降低，並且使肺血管阻力增加，進而影響了氧氣的運送。正常的生理代償機制應該是提升氧氣供應量回復組織的需氧量。 已知動脈血氧分壓間接反應氧氣含量及通氣-灌流分布，過去文獻中的結果發現休克造成動脈血氧分壓表現不一致，是否因為心輸出量的改變造成肺血流重新分布，改善肺臟氣體交換而使得動脈血氧分壓增加，提高氧氣輸送能力。為了減少活體動物心輸出量不易控制及神經反應等變數，故選用兔子離體肺模式來觀察灌流量對於肺血流重分布的影響。實驗根據灌流量的增減順序分成三組，控制組的灌流量不變，向上調控組(Upward)的灌流量先增後減，向下調控組(Downward)的灌流量先減後增，利用螢光微粒技術分析肺臟整體相對血流的改變及肺血流空間分布，各組間生理參數及動脈氧分壓並沒有差異，灌流量的增減並不影響肺部氧氣之氣體交換。當灌流量增加時，肺血管阻力會明顯降低，離體肺模式維持正常的肺生理表現。灌流量的增減，並不影響高血流，中血流，低血流肺塊佔整體肺區的比例，皆維持約1: 1: 1.2的比例；各分區單獨來看，原本屬於高血流、中血流、低血流區的肺塊，當灌流量改變時，都會有部份比例的血流有增減的表現，但是沒有統計上的一致性。配合座標值觀察肺相對血流的空間分布，灌流量的改變對於左-右(Left- Right)平面及背-腹(Dorsal- Ventral)平面相對血流的分布沒有影響，但是在底-頂(Caudal-Cranial)的平面可以發現，當灌流量增加時，肺血流的空間分布會往頂部(Cranial)偏移， 肺底部減少的血流比例較大，相對血流斜率會明顯增加。當灌流量降低量較大時，底部(Caudal)的肺血流會有增加的趨勢，但可能增減變異性過大，無統計上的意義。結合立體空間發現，當灌流量不變時，肺血流的增減改變並沒有特定方向性；而灌流量增加時，肺頂部(Cranial)的相對血流有增加，而底部(Caudal)的肺血流是減少的；灌流量降低時，增加的血流分布到肺底部(Caudal)，而頂部(Cranial)的相對血流是減少的趨勢。從實驗結果得知，灌流量的改變並不會影響高、中、低血流佔整體肺區的比例，但是會使得肺血流的重新分布，使血流往特定空間偏移，且此一趨勢與重力相關。 關鍵字: 低血容性休克、離體肺、螢光微粒分析技術、灌流量、肺血流分布、動脈氧分壓 Abstract Hypovolemic shock is a particular form of shock in which the heart is unable to supply enough blood to the body. It is caused by blood loss or inadequate blood volume, increase the pulmonary vascular resistance, and hider the delivery of oxygen, it may stop the tissue functioning. We expect a physiological compensatory mechanism would recover the tissue oxygen by elevation of the oxygen content. VA/Q match or not is an important determinant of arterial partial pressure. It’s difficult to control the cardiac output and neural reaction during the in vivo experiments, and the isolated lung model can prevent the problems. It’s the suitable model for investigate the effect of perfusion rate on pulmonary blood flow distribution. Animals have been separate 3 groups depend on the perfusion rate sequence. The perfusion rate is consistent on control group, and is raise first then reduce on upward group, downward group is opposite. Fluorescent Microsphere Technique (FMS) is used to analysis the change of relative blood flow in total lung and the redistribution. We observe there is no difference on physiological parameters and the blood gas data, the gas exchange remain saturation even the perfusion rate has been change. Fall in pulmonary vascular resistance as the perfusion rate is raised, and the isolated lung model can imitate normal pulmonary physiological. When the perfusion rate increase, the ratio of total lung region and the lung pieces of high、middle、and low region is remain consistent, the ratio is always keep 1:1:1.2. If we separate the region, the blood flow of each region increase and decrease both, but no prominent difference. The spatial distribution of pulmonary blood flow is observed, and there is no difference in left-right plane and dorsal-ventral plane. The pulmonary relative blood flow would shift to the cranial side during the perfusion rate increase on caudal-cranial plane. The relative blood flow trend toward the caudal side during the perfusion rate decrease, but no difference in statistics. Combine the spatial coordinate, the change of relative blood flow is scattered during the perfusion rate consistent. The relative blood flow of the lung pieces at cranial region is almost increased, and at caudal region is decreased during the perfusion rate raised. And during the perfusion rate reduced, there is a tendency to the relative blood flow of the lung pieces at caudal region is increased. We conclude that if the perfusion rate is change or not don’t affect the ratio of the blood flow of each region and the total lung. The redistribution of pulmonary relative blood flow would happen and there is a correction with the tendency and gravity.
8
Jun-YiLiu e 劉俊易. "Study on Living Tissue Non-linear Heat Transfer and Inverse Estimation of Blood Perfusion Rate". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ktv85e.
Testo completo
9
Zhang, Zewei. "Transient bioheat transfer analysis in biological tissues by fundamental-solution-based numerical methods". Phd thesis, 2015. http://hdl.handle.net/1885/15827.
Testo completoAbstract (sommario):
Taylor's expansion approach was applied to linearize the nonlinear term in the original nonlinear bioheat transfer governing equation. Then the DRM and the MFS was established to obtain the particular and homogeneous solutions. The influence of blood perfusion rate on temperature distribution in the skin tissue was analysed by changing the coefficients in the three expressions of blood perfusion rate. Numerical results showed that the variation of blood perfusion rate plays a significant role in the temperature distribution within the skin tissue.
Finally, a meshless numerical scheme combining the operator splitting method (OSM), the RBF interpolation and the MFS was developed for solving transient nonlinear bioheat problems in two-dimensional skin tissue. In the numerical scheme, the nonlinearity caused by the temperature-dependent blood perfusion rate (TDBPR) is taken into consideration. In the procedure, the OSM is used to separate the Laplacian operator and the nonlinear source term, and then second-order time-stepping schemes are employed for approximating two splitting operators in order to convert the original governing equation into a linear nonhomogeneous Helmholtz-type governing equation (NHGE) at each time step. The full fields consisting of the particular and homogeneous solutions are enforced to fit the NHGE at interpolation points and the boundary conditions at boundary collocations to determine unknowns at each time step. The proposed method was verified by comparison with other methods. Furthermore, the sensitivity of the coefficients in cases of a linear and an exponential relationship of TDBPR was investigated to reveal their bioheat effect on the skin tissue.
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Deschênes, Micheline Céline. "Effect of hormone replacement therapy on retinal and optic nerve head blood flow and topography in postmenopausal women, and retinal tissue perfusion in ovariectomized rats". Thèse, 2007. http://hdl.handle.net/1866/6502.
Testo completoLibri sul tema "Blood perfusion rate"
1
Perkins, Gavin D. Cardiac massage and blood flow management during cardiac arrest. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0062.
Testo completoAbstract (sommario):
When cardiac arrest occurs, blood flow to the vital organs diminishes rapidly. Chest compressions are an essential element of cardiopulmonary resuscitation (CPR), yet they achieve, at best, one-third of the normal cardiac output. The speed of initiating CPR, as well as its quality is critical to patient outcomes. Optimal chest characteristics of compressions are defined as pushing hard (depth > 5 cm) and fast (compression rate 100–120/min). Pressure should be released fully between sequential chest compressions and interruptions in chest compressions should be minimized. Even short interruptions in CPR around the time of attempted defibrillation can be harmful. CPR feedback and prompt devices can be used to monitor the quality of CPR. Studies have shown these devices can improve the quality of CPR, but do not improve overall survival. Mechanical chest compression devices may be usefully deployed when it is difficult or unsafe to perform manual CPR, but there is no evidence that the routine deployment of these devices improves outcome. Vasoactive drugs improve coronary perfusion pressure and increase the chances of return of spontaneous circulation. However, there is no definitive evidence that they improve long-term survival. Recent data have raised the possibility that adrenaline may worsen long-term outcomes.
2
Navaratnam, M., e C. Ramamoorthy. Hypoplastic Left Heart Syndrome. A cura di Kirk Lalwani, Ira Todd Cohen, Ellen Y. Choi e Vidya T. Raman. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190685157.003.0009.
Testo completoAbstract (sommario):
Approximately 960 babies are born per year in the United States with hypoplastic left heart syndrome. Over the last 20 years, advances in surgical techniques, perioperative care, cardiopulmonary bypass, and intensive care unit management have converted this previously fatal condition to one with a neonatal survival rate of 90% to 92% for standard risk patients. Understanding the factors affecting the balance of pulmonary blood flow and systemic blood flow and ensuring adequate cardiac output and end-organ perfusion is critical to successful outcomes. Extracorporeal membrane oxygenation remains an important support modality following stage I palliation. This chapter discusses this syndrome and describes treatment options.
3
Suri, Ajay, e Jean R. McEwan. Anti-anginal agents in critical illness. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0037.
Testo completoAbstract (sommario):
Angina is chest pain resulting from the lack of blood supply to heart muscle most commonly due to obstructive atherosclerotic. Intensive care unit patients are subject to various stresses that will increase the demand on the heart and are in a pro-thrombotic state. Patients in an intensive treatment unit may be sedated and so cardiac ischaemia may be detected by electrocardiogram, haemodynamic monitoring, and echocardiographic imaging of function. These signs may indicate critical coronary perfusion heralding a myocardial infarction and are alleviated by anti-anginal drugs. Beta-blockers and calcium channel blockers are the usual first-line treatments for angina, but may not be ideal in the critically-ill patient. Nitrates reduce blood pressure without typically affecting heart rate. Nicorandil is a similar mechanism of action and tends to be given orally, while ivabridine, an If channel blocker, is a newer anti-anginal, which acts by reducing heart rate, while not affecting blood pressure. Ranolazine is the one of the newest anti-anginal agents and is believed to alter the transcellular late sodium current thereby decreasing sodium entry into ischaemic myocardial cells.
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Taillefer, Raymond, e Frans J. Th Wackers. Kinetics of Conventional and New Cardiac Radiotracers. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199392094.003.0004.
Testo completoAbstract (sommario):
The kinetics of radiotracers, that is the mode of uptake, retention and release from the myocardium, are relevant for designing and implementing optimized nuclear cardiac imaging protocols. This chapter addresses the kinetics of commonly used radiotracers for imaging myocardial perfusion, sympathetic neuronal function and cardiac metabolism, both with SPECT and PET cardiac imaging. The optimal timing of imaging after injection either at stress or at rest is determined by rate of uptake in the heart and adjacent organs, as well as the residence time of radiotracers within the myocytes. The efficiency of myocardial extraction over a wide range myocardial blood flows is relevant for reliable detection of obstructive coronary artery disease and absolute quantification of regional myocardial blood flow. For each cardiac imaging agent the cellular mechanism of uptake and its release or retention are discussed with an emphasis on the clinical impact of these parameters.
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Jacquemyn, Yves, e Anneke Kwee. Antenatal and intrapartum fetal evaluation. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198713333.003.0006.
Testo completoAbstract (sommario):
Antenatal and intrapartum fetal monitoring aim to identify the beginning of the process of fetal hypoxia before irreversible fetal damage has taken place. Fetal movement counting by the mother has not been reported to be of any benefit. The biophysical profile score, incorporating ultrasound and fetal heart rate monitoring, has not been proven to reduce perinatal mortality in randomized trials. Doppler ultrasound allows the exploration of the perfusion of different fetal organ systems and provides data on possible hypoxia and fetal anaemia. Maternal uterine artery Doppler can be used to select women with a high risk for intrauterine growth restriction and pre-eclampsia but does not directly provide information on fetal status. Umbilical artery Doppler has been shown to reduce perinatal mortality significantly in high-risk pregnancies (but not in low-risk women). Adding middle cerebral artery Doppler to umbilical artery Doppler does not increase accuracy for detecting adverse perinatal outcome. Ductus venosus Doppler demonstrates moderate value in diagnosing fetal compromise; it is not known whether its use adds any value to umbilical artery Doppler alone. Cardiotocography (CTG) reflects the interaction between the fetal brain and peripheral cardiovascular system. Prelabour routine use of CTG in low-risk pregnancies has not been proven to improve outcome; computerized CTG significantly reduces perinatal mortality in high-risk pregnancies. Monitoring the fetus during labour with intermittent auscultation has not been compared to no monitoring at all; when compared with CTG no difference in perinatal mortality or cerebral palsy has been noted. CTG does lower neonatal seizures and is accompanied by a statistically non-significant rise in caesarean delivery. Fetal blood sampling to detect fetal pH and base deficit lowers caesarean delivery rate and neonatal convulsions when used in adjunct to CTG. Determination of fetal scalp lactate has not been shown to have an effect on neonatal outcome or on the rate of instrumental deliveries but is less often hampered by technical failure than fetal scalp pH. Analysis of the ST segment of the fetal ECG (STAN®) in combination with CTG during labour results in fewer vaginal operative deliveries, less need for neonatal intensive care, and less use of fetal blood sampling during labour, without a change in fetal metabolic acidosis when compared to CTG alone.
Capitoli di libri sul tema "Blood perfusion rate"
1
Andres, Matthias, e René Pinnau. "The Cattaneo Model for Laser-Induced Thermotherapy: Identification of the Blood-Perfusion Rate". In SEMA SIMAI Springer Series, 25–41. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99983-4_2.
Testo completo
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Pedersen, Michael, Pietro Irrera, Walter Dastrù, Frank G. Zöllner, Kevin M. Bennett, Scott C. Beeman, G. Larry Bretthorst, Joel R. Garbow e Dario Livio Longo. "Dynamic Contrast Enhancement (DCE) MRI–Derived Renal Perfusion and Filtration: Basic Concepts". In Methods in Molecular Biology, 205–27. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_12.
Testo completoAbstract (sommario):
AbstractDynamic contrast-enhanced (DCE) MRI monitors the transit of contrast agents, typically gadolinium chelates, through the intrarenal regions, the renal cortex, the medulla, and the collecting system. In this way, DCE-MRI reveals the renal uptake and excretion of the contrast agent. An optimal DCE-MRI acquisition protocol involves finding a good compromise between whole-kidney coverage (i.e., 3D imaging), spatial and temporal resolution, and contrast resolution. By analyzing the enhancement of the renal tissues as a function of time, one can determine indirect measures of clinically important single-kidney parameters as the renal blood flow, glomerular filtration rate, and intrarenal blood volumes. Gadolinium-containing contrast agents may be nephrotoxic in patients suffering from severe renal dysfunction, but otherwise DCE-MRI is clearly useful for diagnosis of renal functions and for assessing treatment response and posttransplant rejection.Here we introduce the concept of renal DCE-MRI, describe the existing methods, and provide an overview of preclinical DCE-MRI applications to illustrate the utility of this technique to measure renal perfusion and glomerular filtration rate in animal models.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction is complemented by two separate publications describing the experimental procedure and data analysis.
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Jerome, Neil Peter, Anna Caroli e Alexandra Ljimani. "Renal Diffusion-Weighted Imaging (DWI) for Apparent Diffusion Coefficient (ADC), Intravoxel Incoherent Motion (IVIM), and Diffusion Tensor Imaging (DTI): Basic Concepts". In Methods in Molecular Biology, 187–204. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_11.
Testo completoAbstract (sommario):
AbstractThe specialized function of the kidney is reflected in its unique structure, characterized by juxtaposition of disorganized and ordered elements, including renal glomerula, capillaries, and tubules. The key role of the kidney in blood filtration, and changes in filtration rate and blood flow associated with pathological conditions, make it possible to investigate kidney function using the motion of water molecules in renal tissue. Diffusion-weighted imaging (DWI) is a versatile modality that sensitizes observable signal to water motion, and can inform on the complexity of the tissue microstructure. Several DWI acquisition strategies are available, as are different analysis strategies, and models that attempt to capture not only simple diffusion effects, but also perfusion, compartmentalization, and anisotropy. This chapter introduces the basic concepts of DWI alongside common acquisition schemes and models, and gives an overview of specific DWI applications for animal models of renal disease.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
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Forbes, Michael L., Kristy S. Hendrich, Joanne K. Schiding, Donald S. Williams, Chien Ho, Steven T. DeKosky, Donald W. Marion e Patrick M. Kochanek. "Perfusion MRI Assessment of Cerebral Blood Flow and CO2 Reactivity after Controlled Cortical Impact in Rats". In Advances in Experimental Medicine and Biology, 7–12. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4615-5865-1_2.
Testo completo
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Zachariah, Joseph. "Cerebrospinal Physiology". In Mayo Clinic Critical and Neurocritical Care Board Review, a cura di Eelco F. M. Wijdicks, James Y. Findlay, William D. Freeman e Ayan Sen, 74–78. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190862923.003.0009.
Testo completoAbstract (sommario):
With its high metabolic rate and lack of substrate stores, the brain is dependent on a constant supply of oxygen and glucose. If blood flow stops, alterations in brain function occur within seconds and irreversible injury can occur within a few minutes. Many patients admitted to neurosciences intensive care units have acute strokes, are eligible for endovascular procedures, and may need other measures to preserve adequate cerebral blood flow. An understanding of the blood supply, venous drainage, and factors affecting cerebral perfusion is thus pivotal to the practice of neurologic critical care. This chapter reviews the anatomical and physiologic principles governing cerebral circulation and blood flow.
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Andriessen, Peter. "Autonomic Cardiovascular Regulation in the Newborn". In Neonatal Monitoring Technologies, 201–21. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-4666-0975-4.ch009.
Testo completoAbstract (sommario):
This paper reviews the baroreflex mediated heart rate response in human infants with a focus on data acquisition, signal processing and autonomic cardiovascular modeling. Baroreflex mediated heart rate response is frequently used as an estimate of autonomic cardiovascular regulation. Baroreflex mediated heart rate response may be viewed in terms of a negative-feedback system. To study fluctuations in this feedback system, continuous registration of ECG and blood pressure waveforms are required. From these waveforms, time series of R-R interval and blood pressure values are derived. This paper focus on spontaneous baroreflex sensitivity (e.g., R-R interval change per unit of arterial blood pressure change, ms/mmHg) calculated from cross-spectral analysis of spontaneous occurring changes in R-R interval and blood pressure. Despite different methodology (sequence method; transfer function analysis; head-up tilt) there is fairly good agreement of spontaneous baroreflex sensitivity values during homeostasis. Preterm infants and term newborns have values of 2-4 and 10-15 ms/mmHg, respectively. These values are much lower than found in adults, approximately 25 ms/mmHg. The clinical relevance of a limited baroreflex function may be that acute perturbations of the cardiovascular system are poorly counteracted and may result in poor cerebral perfusion.
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Farne, Hugo, Edward Norris-Cervetto e James Warbrick-Smith. "Blackout". In Oxford Cases in Medicine and Surgery. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780198716228.003.0009.
Testo completoAbstract (sommario):
Note that the terms ‘syncope’ and ‘loss of consciousness’ are not interchangeable as loss of consciousness can be due to either syncopal or non-syncopal causes. Syncope is a form of loss of consciousness in which hypoperfusion of the brain is the cause (from the Greek syn (together) and kopein (to cut), referring to the fact that the blood flow that joins the brain together with the rest of the body has been cut). Syncopal causes can be subdivided by mechanism as follows: • ‘Reflex’: this is believed to involve activation of a primitive reflex that leads mammals to ‘play dead’ when faced with danger. Their heart rate slows and their blood pressure drops temporarily, reducing cerebral perfusion and leading to syncope. Some people appear to have a low threshold for activating this reflex in specific situations—for example after standing still for a long time, after seeing something frightening (e.g. blood, needles), or when straining (micturition, defecation). • ‘Cardiac’: pathologies causing a reduction in cardiac output (such as arrhythmias or outlet obstruction) can also lead to syncope. • ‘Orthostatic’: orthostatic hypotension basically means low blood pressure on sitting or standing (as opposed to lying flat). When we stand up there is a sudden drop in blood pressure that we compensate for by vasoconstriction, particularly of the ‘capacitance’ veins in the legs. This reduces the intravascular space, enabling us to maintain the pressure. However, this vasoconstriction takes a few seconds, so to prevent a transient fall in blood pressure every time we stand, there is a temporary increase in heart rate. Patients with reduced intravascular volume (e.g. from dehydration) and/or in whom the normal autonomic response (transient tachycardia and peripheral vasoconstriction) to standing is blunted (e.g. due to drugs or autonomic neuropathy) are vulnerable to blackouts. • ‘Cerebrovascular’: these are non-cardiac structural causes of reduced cerebral perfusion, i.e. obstructions to the blood flow between the heart and the brain. They are relatively uncommon. The main causes of a transient loss of consciousness are summarized in Figure 3.1, with the most common in large font. You should also remember that patients may believe they have lost consciousness when in fact they haven’t.
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Pierard, Luc A., Paola Gargiulo, Pasquale Perrone-Filardi, Bernhard Gerber e Joseph B. Selvanayagam. "Assessment of viability". In The ESC Textbook of Cardiovascular Imaging, a cura di José Luis Zamorano, Jeroen J. Bax, Juhani Knuuti, Patrizio Lancellotti, Fausto J. Pinto, Bogdan A. Popescu e Udo Sechtem, 545–64. Oxford University Press, 2021. http://dx.doi.org/10.1093/med/9780198849353.003.0037.
Testo completoAbstract (sommario):
Ischaemic left ventricular (LV) dysfunction due to coronary artery disease (CAD) is steadily increasing as a consequence of the ageing of the population and of improved survival of patients with acute coronary syndromes and currently represents the first cause of heart failure (HF). Myocardial function is dependent on blood supply, as anaerobic reserve is minimum due to a nearly maximal arteriovenous oxygen extraction. At rest, myocardial blood flow remains normal even in the presence of severe coronary artery stenosis (up to 85% diameter stenosis) by coronary autoregulation. In the presence of transstenotic pressure gradient due to epicardial coronary stenosis, arteriolar dilatation maintains normal myocardial flow at rest but with a progressive reduction in flow reserve. When arteriolar dilatation is maximal, autoregulation is exhausted and myocardial ischaemia develops. The limit of autoregulation depends on myocardial oxygen demand and is influenced by heart rate. Tachycardia increases oxygen demand and supply is reduced because of a decreased diastolic perfusion time. In the presence of acute ischaemia, there is a close relation between subendocardial perfusion and transmural function. Indeed, the contribution of subendocardium to myocardial thickening largely exceeds the contribution of the subepicardium. Akinesia can therefore result from subendocardial ischaemia and transmural ischaemia is not necessary. This chapter looks at how viability of the different techniques for treating myocardial dysfunction is assessed.
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Singh, Deepika, Ashutosh Kumar Singh e Sonia Tiwari. "Thermal Analysis of Realistic Breast Model With Tumor and Validation by Infrared Images". In Research Anthology on Medical Informatics in Breast and Cervical Cancer, 532–44. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-6684-7136-4.ch027.
Testo completoAbstract (sommario):
Breast thermography is an emerging adjunct tool to mammography in early breast cancer detection due to its non-invasiveness and safety. Steady-state infrared imaging proves promising in this field as it is not affected by tissue density. The main aim of the present study is to develop a computational thermal model of breast cancer using real breast surface geometry and internal tumor specification. The model depicting the thermal profile of the subject's aggressive ductal carcinoma is calibrated by variation of blood perfusion and metabolic heat generation rate. The subject's IR image is used for validation of the simulated temperature profile. The thermal breast model presented here may prove useful in monitoring the response of tumor post-chemotherapy for female subjects with similar breast cancer characteristics.
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Singh, Deepika, Ashutosh Kumar Singh e Sonia Tiwari. "Thermal Analysis of Realistic Breast Model With Tumor and Validation by Infrared Images". In Computational Methodologies for Electrical and Electronics Engineers, 208–18. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-3327-7.ch017.
Testo completoAbstract (sommario):
Breast thermography is an emerging adjunct tool to mammography in early breast cancer detection due to its non-invasiveness and safety. Steady-state infrared imaging proves promising in this field as it is not affected by tissue density. The main aim of the present study is to develop a computational thermal model of breast cancer using real breast surface geometry and internal tumor specification. The model depicting the thermal profile of the subject's aggressive ductal carcinoma is calibrated by variation of blood perfusion and metabolic heat generation rate. The subject's IR image is used for validation of the simulated temperature profile. The thermal breast model presented here may prove useful in monitoring the response of tumor post-chemotherapy for female subjects with similar breast cancer characteristics.
Atti di convegni sul tema "Blood perfusion rate"
1
Wang, Xian-ju, Chang-chun Zeng, Han-ping Liu, Song-hao Liu e Liang-gang Liu. "Effects of laser acupuncture on blood perfusion rate". In Fourth International Conference on Photonics and Imaging in Biology and Medicine, a cura di Kexin Xu, Qingming Luo, Da Xing, Alexander V. Priezzhev e Valery V. Tuchin. SPIE, 2006. http://dx.doi.org/10.1117/12.709706.
Testo completo
2
Robinson, Paul S., Elaine P. Scott e Thomas E. Diller. "Validation of Methodologies for the Estimation of Blood Perfusion Using a Minimally Invasive Probe". In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0805.
Testo completoAbstract (sommario):
Abstract Parameter estimation techniques have been utilized in the development of methodologies to noninvasively measure blood perfusion using a new thermal surface probe. The core of this probe is comprised of a small, lightweight heat flux sensor that is placed in contact with tissue and provides time-resolved signals of heat flux and surface temperature while the probe is cooled by air jets. Parameter estimation techniques were developed that incorporate heat flux and temperature data with calculated data from a biothermal model of the tissue and probe. The technique simultaneously estimates blood perfusion and thermal contact resistance between the probe and tissue. Validation of this concept was carried out by experimentation with controlled perfusion through non-biological porous media. A controlled rate of uniform flow of warm water through a fine pore sponge provided a phantom model for blood perfusion through biological tissue. The parameter estimation technique was applied to measurements taken over a range of flow rates. Heat flux and temperature measurements and the resulting perfusion estimates correlated well with the experimentally imposed perfusion rate. This research helps establish the validity of using this method to develop a practical, noninvasive probe to clinically measure blood perfusion.
3
Yuan, Ping, Hsueh-Erh Liu, Chih-Wei Chen e Hong-Sen Kou. "Analysis of Temperature Response in Biological Tissue With Sinusoidal Temperature Oscillation on the Skin". In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56493.
Testo completoAbstract (sommario):
This study investigates the transient temperature response in biological tissue with sinusoidal temperature oscillation on the skin surface. Based on the Laplace transform, an exact solution of the Pennes bioheat transfer equation has been derived which includes the whole time domain from the initial transient oscillation to the final steady periodic oscillation. Furthermore, the exact solutions of special cases under no perfusion rate, constant temperature, and the combination of those two assumptions are demonstrated in this study. The primary application for this type of analysis is to assess the blood perfusion rate in the skin by imposing a periodic temperature load onto the skin surface. Through the noninvasive measurement of the maximum heat flux or minimum heat flux on the skin, equation (15) can be utilized to estimate the blood perfusion rate in living tissues. The results show that both the larger perfusion rate and greater tissue depth decrease the amplitude of the sinusoidal temperature response. A larger perfusion rate can also reduce the unstable duration for the estimation of the blood perfusion rate. Meanwhile, the shift of phase angle related to the sinusoidal temperature variation increases with tissue that is deeper and has lower perfusion rate.
4
Ricketts, Patricia L., Ashvinikumar V. Mudaliar, Brent E. Ellis, Thomas E. Diller, Elaine P. Scott e Otto I. Lanz. "Noninvasive Blood Perfusion Measurement on the Liver of an Anesthetized Rat". In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176538.
Testo completoAbstract (sommario):
Blood perfusion is the local, non-directional blood flow through living tissue. It is measured as the volumetric flow rate of blood per volume of tissue and a large range of perfusion values have been reported for human tissue (i.e. 0.002–0.5 ml/ml/s). This large range is thought to be due to measurement sensitivity, environmental factors, and tissue type and location.
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Zhu, Liang, Zhengxin Mi e Lisa X. Xu. "Temperature Distribution in Prostate During Transurethral Radio Frequency Thermotherapy Treatment of Benign Prostatic Hyperplasia". In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0806.
Testo completoAbstract (sommario):
Abstract The heating pattern of a radio frequency (RF) electrode catheter and its induced temperature field in prostate during transurethral thermal therapy treatment were investigated in this study. Experiments were performed in a tissue-equivalent phantom gel to quantitatively examine the volumetric heating produced by a RF electrode catheter for transurethral prostatic thermotherapy. The specific absorption rate (SAR) of RF energy in the gel was measured from the initial transient temperatures at various locations within the gel. An expression for the SAR was proposed and its unknown parameters in this expression were determined by comparing the predicted and measured SAR values. The SAR distribution was then used in conjunction with the Pennes bioheat transfer equation to model the temperature field in prostate during the thermotherapy treatment. The prostatic tissue temperature rise and its relation to the effect of blood perfusion were analyzed. Blood perfusion is found to be an important factor for removal of heat especially at the higher RF heating level. The minimum RF power required to achieve a maximum tissue temperature above 45 °C is in the range from 14 W to 60 W depending on the local blood perfusion rate (0.2 ∼ 1.5 ml/gm/min). An empirical expression for the detailed temperature field within the prostate for various blood perfusion rates and RF power levels was also provided for clinical purposes.
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Badimon, L., J. J. Badimon e V. Fuster. "ACUTE THROMBOSIS IN STENOTIC AREAS: IMPORTANCE OF THE VASCULAR MATRIX EXPOSED TO BLOOD". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642842.
Testo completoAbstract (sommario):
The platelet response to angioplasty or spontaneous plaque rupture leads to acute thrombotic occlusion under certain conditions. We analyzed the role of local shear rate (flow and vessel cross-section related), the nature of the exposed matrix and the effect of thrombin inhibition in platelet acute response to injury. Collagen type I (exposed in plaque rupture) and de-endothelialized pig aorta (mild injury) were exposed to pig blood in a tubular perfusion chamber with well characterized flow conditions, placed within an extracorporeal circuit in swine (N=20). Platelet deposition was measured by labeling autologous platelets with Indium and optical morphometry of epoxy embedded specimens. Selected specimens were analyzed by electron microscopy. Unanticoagulated blood and blood from animals treated with 300u/Kg of heparin were perfused over the substrate for 3 and 10 min at local shear rates typical of unobstructed arteries (212s™1 - 424s™1) and of stenotic vessel (824s™1 - 1690s™1). Platelet deposition (Platelets × 106/cm2 ± SE) for 3 min perfusions were:Platelet deposition is dependent on the reactivity of the vascular matrix exposed to blood and on the local shear rate. The greatest rate of thrombus growth is observed with collagen and high shear rate conditions which may precipitate acute thrombotic occlusion in stenotic regions, mainly when the coagulation pathway is not inhibited (255×l06 platelets/ cm2 in 3 minutes. The relative contribution of rheology and the isolated components of the atherosclerotic plaque matrix exposed to blood in the onset of acute coronary syndromes will be differentiated with this experimental model.
7
Salloum, M., N. Ghaddar e K. Ghali. "A New Transient Bio-Heat Model of the Human Body". In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72303.
Testo completoAbstract (sommario):
A new mathematical multi-segmented model based on an improved Stolwijk model is developed for predicting nude human thermal and regulatory responses within body segments and the environment. The passive model segments the body into the 15 cylindrical parts. Each body part is divided into four nodes of core, skin, artery blood, and vein blood. The body nodes interact with each other through convection, perfusion and conduction. In any body element, the blood exiting the arteries and flowing into the capillaries is divided into blood flowing in the core (exchanges heat by perfusion in the core) and blood flowing into the skin layer (exchanges heat by perfusion in the skin). The model calculates the blood circulation flow rates based on exact physiological data of Avolio [1], real dimensions, and anatomic positions of the arteries in the body. The circulatory system model takes into consideration the pulsatile blood flow in the macro arteries with its effect on the convective heat transport. The inclusion of calculated blood perfusion in both the tissue and the skin, based on the arterial system model and the heart rate is unique for the current model. The bio-heat human model is capable of predicting accurately nude human transient physiological responses such as the body’s skin, tympanic, and core temperatures, sweat rates, and the dry and latent heat losses from each body segment. The nude body model predictions are compared with published theoretical and experimental data at a variety of ambient conditions and activity. The current model agrees well with experimental data during transient hot exposures. The nude human model has an accuracy of less than 8% for the whole-body heat gains or losses and ±0.48°C for skin temperature values.
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Bastida, E., G. Escolar, R. Castillo, A. Ordinas e J. J. Sixma. "FIBRONECTIN IS REQUIRED FOR PLATELET ADHESION AND FOR THROMBUS FORMATION ON SUBENDOTHELIUM AND COLLAGEN SURFACES". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643558.
Testo completoAbstract (sommario):
Fibronectin (FN) plays a role in several adhesion mediated functions including the interaction of platelets with subendothelium.We investigated the role of plasma FN in platelet adhesion and platelet thrombus formation under flow conditions.To do this we used two different perfusion models:1)the annular chamber with α -chymotrypsin-treated rabbit vessel segments and 2)the flat chamber with coverslips coated with fibrillar purified human collagen type III.Perfusates consisted of washed platelets, and washed red blood celIs,suspended in normal or FN-depleted plasma.Perfusions were carried out for 10 min at shear rates of 300 or 1300 sec™1 Platelet deposition and thrombus dimensions were morphometrically evaluated by a computerized system. We found that depletion of plasma FN significantly reduced the percentage of total coverage surface and percentage of platelet thrombus, at both shear rates studied, and in both perfusion systems (p < 0.01)(p < 0.01).The dimensions of the platelet thrombi formed in perfusions at high shear rate were also significantly reduced in perfusions carried out with FN-depleted plasma.(p < 0.01). Addition of purified FN to FN-depleted perfusates restored all the values to those measured in the control perfusions.These results indicate that, in addition to supporting platelet adhesion to the subendothelium and to fibrillar collagen, FN contributes to platelet thrombus formation under flow conditions.
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Okajima, Junnosuke, Takahiro Okabe, Tessai Sugiura, Atsuki Komiya, Takashi Seki e Shigenao Maruyama. "Estimation of Blood Perfusion Rate and Its Temperature Dependency in Human Abdominal Area under Heating Condition". In The 15th International Heat Transfer Conference. Connecticut: Begellhouse, 2014. http://dx.doi.org/10.1615/ihtc15.bma.009884.
Testo completo
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Inauen, W., T. Bombeli, H. R. Baumgartner, A. Haeberli e P. W. Straub. "EFFECTS OF HEPARIN AND COUMARIN ON DEPOSITION OF FIBRIN, PLATELETS AND PLATELET THROMBI ON RABBIT AORTA SUBENDOTHELIUM EXPOSED TO FLOWING HUMAN BLOOD". In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643876.
Testo completoAbstract (sommario):
The effect of heparin and phenprocoumon on thrombogenesis induced by rabbit aorta subendothelium (SE) was investigated in 20 volunteers using an ex vivo perfusion system. Blood was drawn directly from an antecubital vein through an annular chamber with exposed SE at lOml/min flow rate (650sec−1 shear rate) for 5min. Following buffer perfusion for 15sec, the middle portion of SE was removed for plasmin digestion and adjacent segments were fixed and embedded for morphometric analysis. Perfusions were performed 20 min after i.v. injection of heparin 1000, 2500 and 5000 IU, respectively; and during the decline and steady-state of prothrombin activity during a 2 weeks treatment with phenprocoumon to target INR of 5.0.The amount of fibrin attached to SE, as measured by fragment E RIA in plasmin digests, correlated negatively with the dose of heparin (r=−0.83, P<0.001, n=48) and with INR during coumarin intake (r=−0.58, P<0.01, n=40). After high doses of either heparin or coumarin fibrin deposition on SE was virtually abolished (table). Platelet adhesion was increased. Platelet thrombus volumes and heights were reduced by heparin and coumarin.We conclude that both heparin and coumarin dose-dependently inhibit fibrin formation induced by SE. In addition, both drugs impair platelet thrombus growth and/or stability indicating that these processes may also depend on the coagulation mechanism.