scholarly journals Assessing potential errors of MRI-based measurements of pulmonary blood flow using a detailed network flow model

2012 ◽  
Vol 113 (1) ◽  
pp. 130-141 ◽  
Author(s):  
K. S. Burrowes ◽  
R. B. Buxton ◽  
G. K. Prisk
Keyword(s):  
Blood Flow ◽  
Network Flow ◽  
Pulmonary Blood Flow ◽  
Sagittal Plane ◽  
Flow Distribution ◽  
Image Plane ◽  
Relative Dispersion ◽  
Plane Flow ◽  
Image Planes ◽  
Imaging Plane

MRI images of pulmonary blood flow using arterial spin labeling (ASL) measure the delivery of magnetically tagged blood to an image plane during one systolic ejection period. However, the method potentially suffers from two problems, each of which may depend on the imaging plane location: 1) the inversion plane is thicker than the imaging plane, resulting in a gap that blood must cross to be detected in the image; and 2) ASL includes signal contributions from tagged blood in conduit vessels (arterial and venous). By using an in silico model of the pulmonary circulation we found the gap reduced the ASL signal to 64–74% of that in the absence of a gap in the sagittal plane and 53–84% in the coronal. The contribution of the conduit vessels varied markedly as a function of image plane ranging from ∼90% of the overall signal in image planes that encompass the central hilar vessels to <20% in peripheral image planes. A threshold cutoff removing voxels with intensities >35% of maximum reduced the conduit vessel contribution to the total ASL signal to ∼20% on average; however, planes with large contributions from conduit vessels underestimate acinar flow due to a high proportion of in-plane flow, making ASL measurements of perfusion impractical. In other image planes, perfusion dominated the resulting ASL images with good agreement between ASL and acinar flow. Similarly, heterogeneity of the ASL signal as measured by relative dispersion is a reliable measure of heterogeneity of the acinar flow distribution in the same image planes.

scholarly journals Steep head-down tilt has persisting effects on the distribution of pulmonary blood flow

2006 ◽  
Vol 101 (2) ◽  
pp. 583-589 ◽  
Author(s):  
A. Cortney Henderson ◽  
David L. Levin ◽  
Susan R. Hopkins ◽  
I. Mark Olfert ◽  
Richard B. Buxton ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Regional Blood Flow ◽  
Flow Distribution ◽  
Normal Subjects ◽  
Relative Dispersion ◽  
Lung Water ◽  
Before And After ◽  
Capillary Pressures ◽  
The Right

Head-down tilt has been shown to increase lung water content in animals and alter the distribution of ventilation in humans; however, its effects on the distribution of pulmonary blood flow in humans are unknown. We hypothesized that head-down tilt would increase the heterogeneity of pulmonary blood flow in humans, an effect analogous to the changes seen in the distribution of ventilation, by increasing capillary hydrostatic pressure and fluid efflux in the lung. To test this, we evaluated changes in the distribution of pulmonary blood flow in seven normal subjects before and after 1 h of 30° head-down tilt using the magnetic resonance imaging technique of arterial spin labeling. Data were acquired in triplicate before tilt and at 10-min intervals for 1 h after tilt. Pulmonary blood flow heterogeneity was quantified by the relative dispersion (standard deviation/mean) of signal intensity for all voxels within the right lung. Relative dispersion was significantly increased by 29% after tilt and remained elevated during the 1 h of measurements after tilt (0.84 ± 0.06 pretilt, 1.09 ± 0.09 calculated for all time points posttilt, P < 0.05). We speculate that the mechanism most likely responsible for our findings is that increased pulmonary capillary pressures and fluid efflux in the lung resulting from head-down tilt alters regional blood flow distribution.

Fractal properties of pulmonary blood flow: characterization of spatial heterogeneity

1990 ◽  
Vol 69 (2) ◽  
pp. 532-545 ◽  
Author(s):  
R. W. Glenny ◽  
H. T. Robertson
Keyword(s):  
Blood Flow ◽  
Spatial Heterogeneity ◽  
Pulmonary Blood Flow ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Fractal Model ◽  
Relative Dispersion ◽  
Flow Measurements ◽  
Residual Capacity ◽  
Blood Flow Measurements

The heterogeneity of pulmonary blood flow was examined using a fractal analytic procedure, and the results were compared with the traditional gravitational model of flow distribution. 99mTc-labeled macroaggregate was injected intravenously at functional residual capacity in six supine anesthetized dogs. The lungs were fixed in situ and sliced in transverse sections. The slices were imaged on a planar gamma camera, and a three-dimensional array of blood flow measurements was reconstructed for each lung. Fractal analysis was used to examine the spatial heterogeneity or RDs (relative dispersion = SD/mean) as a function of the number of pieces into which the flow array was subdivided. RDs was fractal and could be characterized by a fractal dimension (Ds) of 1.09 +/- 0.02, where a Ds of 1.0 reflects homogeneous flow and 1.5 indicates a random flow distribution. The data fit the fractal model exceptionally well with an average r = 0.98. RDs was examined in gravitational and isogravitational planes and as expected was greatest in the gravitational direction. However, the difference was small, suggesting that gravitation plays a secondary role to an underlying process producing heterogeneity. Within the limits of resolution attained by this study (piece volumes greater than 0.25 cm3), the heterogeneity of pulmonary blood flow is well characterized by a fractal model.

Effects of pulmonary blood flow on the fractal nature of flow heterogeneity in sheep lungs

1994 ◽  
Vol 77 (3) ◽  
pp. 1474-1479 ◽  
Author(s):  
S. D. Caruthers ◽  
T. R. Harris
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Random Order ◽  
Portion Size ◽  
Relative Dispersion ◽  
Fractal Nature ◽  
Total Flow ◽  
Blood Flows

The spatial heterogeneity of pulmonary blood flow can be described by the relative dispersion (RD) of weight-flow histograms (RD = SD/mean). Glenny and Robertson (J. Appl. Physiol. 69: 532–545, 1990) showed that RD of flow in the lung is fractal in nature, characterized by the fractal dimension (D) and RD for the smallest realizable volume element (RDref). We studied the effects of increasing total pulmonary blood flow on D and RDref. In eight in situ perfused sheep lung preparations, 15-microns radio-labeled microspheres were injected into the pulmonary artery at five different blood flows ranging, in random order, from 1.5 to 5.0 l/m. The lungs were in zone 2 at the lower flows and in zone 3 at the higher flows. The lungs were removed, dried, cut into 2 x 2 x 2-cm3 pieces, weighed, and then counted for microsphere radioactivity. Fractal plots of log(weight) vs. log(RD) were constructed by iteratively combining neighboring pieces and then calculating RD with the increasingly larger portion size. D, which is one minus the slope of the fit through this plot, was 1.14 +/- 0.09 and did not change as blood flow increased. However, RDref decreased significantly (P < 0.01) as total flow increased. We conclude that the fractal nature of pulmonary blood flow distribution is not altered by changes in overall flow.

Mechanisms of improvement in pulmonary gas exchange during isovolemic hemodilution

1999 ◽  
Vol 87 (1) ◽  
pp. 132-141 ◽  
Author(s):  
Steven Deem ◽  
Richard G. Hedges ◽  
Steven McKinney ◽  
Nayak L. Polissar ◽  
Michael K. Alberts ◽  
...  
Keyword(s):  
Blood Flow ◽  
Fractal Dimension ◽  
Gas Exchange ◽  
Spatial Correlation ◽  
Pulmonary Blood Flow ◽  
Minute Ventilation ◽  
Flow Distribution ◽  
Pulmonary Gas Exchange ◽  
Normal Lung ◽  
Blood Flow Distribution

Severe anemia is associated with remarkable stability of pulmonary gas exchange (S. Deem, M. K. Alberts, M. J. Bishop, A. Bidani, and E. R. Swenson. J. Appl. Physiol. 83: 240–246, 1997), although the factors that contribute to this stability have not been studied in detail. In the present study, 10 Flemish Giant rabbits were anesthetized, paralyzed, and mechanically ventilated at a fixed minute ventilation. Serial hemodilution was performed in five rabbits by simultaneous withdrawal of blood and infusion of an equal volume of 6% hetastarch; five rabbits were followed over a comparable time. Ventilation-perfusion (V˙a/Q˙) relationships were studied by using the multiple inert-gas-elimination technique, and pulmonary blood flow distribution was assessed by using fluorescent microspheres. Expired nitric oxide (NO) was measured by chemiluminescence. Hemodilution resulted in a linear fall in hematocrit over time, from 30 ± 1.6 to 11 ± 1%. Anemia was associated with an increase in arterial [Formula: see text] in comparison with controls ( P < 0.01 between groups). The improvement in O2 exchange was associated with reducedV˙a/Q˙heterogeneity, a reduction in the fractal dimension of pulmonary blood flow ( P = 0.04), and a relative increase in the spatial correlation of pulmonary blood flow ( P = 0.04). Expired NO increased with anemia, whereas it remained stable in control animals ( P < 0.0001 between groups). Anemia results in improved gas exchange in the normal lung as a result of an improvement in overallV˙a/Q˙matching. In turn, this may be a result of favorable changes in pulmonary blood flow distribution, as assessed by the fractal dimension and spatial correlation of blood flow and as a result of increased NO availability.

Pulmonary blood flow distribution after the total cavopulmonary connection for complex cardiac anomalies

1999 ◽  
Vol 14 (3) ◽  
pp. 154-160 ◽  
Author(s):  
Masao Tayama ◽  
Nobuaki Hirata ◽  
Tohru Matsushita ◽  
Tetsuya Sano ◽  
Norihide Fukushima ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Total Cavopulmonary Connection ◽  
Blood Flow Distribution ◽  
Cardiac Anomalies ◽  
Cavopulmonary Connection

scholarly journals Pulmonary NO synthase inhibition and inspired CO2: effects on V ′/Q ′ and pulmonary blood flow distribution

2000 ◽  
Vol 16 (2) ◽  
pp. 288 ◽  
Author(s):  
T.V. Brogan ◽  
R.G. Hedges ◽  
S. McKinney ◽  
H.T. Robertson ◽  
M.P. Hlastala ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
No Synthase ◽  
Blood Flow Distribution ◽  
Co2 Effects

Pulmonary Blood Flow Distribution during Normal Ambulation

Respiration ◽  
1974 ◽  
Vol 31 (4) ◽  
pp. 289-295
Author(s):  
M. Arborelius, jr. ◽  
V. Lopéz-Majano ◽  
R.C. Reba ◽  
T.K. Natarajan
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Blood Flow Distribution

scholarly journals Headed in the Wrong Direction: Chronic and Acute Derangements in Pulmonary Blood Flow Distribution in a Patient with Severe Pulmonary Vein Stenosis

2019 ◽  
Vol 16 (10) ◽  
pp. 1321-1326 ◽  
Author(s):  
Luisa Morales-Nebreda ◽  
Christopher S. Chung ◽  
Rishi Agrawal ◽  
Anjana V. Yeldandi ◽  
Benjamin D. Singer ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Vein ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Pulmonary Vein Stenosis ◽  
Blood Flow Distribution ◽  
Wrong Direction ◽  
Vein Stenosis

Effects of pulmonary edema on regional pulmonary perfusion in the intact dog lung

1980 ◽  
Vol 49 (5) ◽  
pp. 834-840 ◽  
Author(s):  
A. B. Malik ◽  
H. van der Zee ◽  
P. H. Neumann ◽  
N. B. Gertzberg
Keyword(s):  
Blood Flow ◽  
Pulmonary Edema ◽  
Pulmonary Blood Flow ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Weight Ratio ◽  
Flow Distribution ◽  
Base Line ◽  
Dependent Lung ◽  
Lung Water ◽  
Pulmonary Hemodynamics

Regional pulmonary blood flow was determined in dogs during varying degrees of pulmonary edema induced by infusing 179.2-659.4 ml/kg normal saline over 2-3 h. Pulmonary hemodynamics and regional blood flows were measured during the base-line period and at 30 min postinfusion. The degree of pulmonary edema was determined by the final extravascular lung water-to-bloodless dry lung weight ratio (W/D). In dogs developing gross alveolar edema (W/D of 10.70 +/- 0.88 vs. 3.10 +/- 0.30 in controls), the blood flow was shifted to either upper or dependent lung regions. The shift to the upper regions was associated with an increased (P < 0.05) pulmonary arterial pressure (Ppa), whereas the shift to the dependent lung was not associated with a significant change in Ppa. Breathing 100% O2 did not prevent these shifts, suggesting that they were not due to localized hypoxic pulmonary vasoconstriction. The flow distribution patterns were also not related to regional differences in edema. In contrast to the changes during fulminant edema, blood flow distribution did not change after moderate levels of pulmonary edema (W/D of 6.03 0.69), suggesting that gross alveolar flooding is required for a redistribution of pulmonary blood flow. Flow redistribution to the upper lung during airway flooding may be due to increase in Ppa, whereas the increased flow in the dependent lung during the same degree of edema may be due to "bulging" of alveolar vessels into the air spaces, secondary to a decrease in surface activity.

Effect of furosemide on pulmonary blood flow distribution in resting and exercising horses

1999 ◽  
Vol 86 (6) ◽  
pp. 2034-2043 ◽  
Author(s):  
Howard H. Erickson ◽  
Susan L. Bernard ◽  
Robb W. Glenny ◽  
M. Roger Fedde ◽  
Nayak L. Polissar ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Flow Distribution ◽  
Thoroughbred Horses ◽  
Dorsal Portion ◽  
Primary Finding ◽  
Pulmonary Arterial ◽  
Relationship Of ◽  
The Relationship ◽  
Rest And Exercise

We determined the spatial distribution of pulmonary blood flow (PBF) with 15-μm fluorescent-labeled microspheres during rest and exercise in five Thoroughbred horses before and 4 h after furosemide administration (0.5 mg/kg iv). The primary finding of this study was that PBF redistribution occurred from rest to exercise, both with and without furosemide. However, there was less blood flow to the dorsal portion of the lung during exercise postfurosemide compared with prefurosemide. Furosemide did alter the resting perfusion distribution by increasing the flow to the ventral regions of the lung; however, that increase in flow was abated with exercise. Other findings included 1) unchanged gas exchange and cardiac output during rest and exercise after vs. before furosemide, 2) a decrease in pulmonary arterial pressure after furosemide, 3) an increase in the slope of the relationship of PBF vs. vertical height up the lung during exercise, both with and without furosemide, and 4) a decrease in blood flow to the dorsal region of the lung at rest after furosemide. Pulmonary perfusion variability within the lung may be a function of the anatomy of the pulmonary vessels that results in a predominantly fixed spatial pattern of flow distribution.

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