scholarly journals Normal liver-to-heart transit time and shunt fraction after transplenic injection of 99MTC-pertechnetate in healthy cats

2021 ◽  
Vol 90 (6) ◽  
pp. 275-282
Author(s):  
E. Vandermeulen ◽  
K. Peremans ◽  
E. Stock ◽  
T. Bosmans ◽  
M. Hesta ◽  
...  
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Normal Liver ◽  
Vascular Anomalies ◽  
Shunt Fraction ◽  
Actual Performance ◽  
Portosystemic Shunts ◽  
Significant Difference ◽  
Normal Mean ◽  
The Mean

Portosystemic shunts (PSS) are rare vascular anomalies in cats. Transsplenic portal scintigraphy (TSPS) can aid in diagnosing PSS in cats. Although the actual performance of the scan remains the same between species, it is questionable whether the generally accepted transit time of seven seconds for small dogs can be applied to cats, thereby influencing shunt fraction (SF) calculation. In this study, normal mean transit time and SF were determined in a population of cats without PSS following two methods established in canine medicine. For both, the mean ± SD transit time was calculated as 6.75 ± 1.58 seconds and 7.40 ± 1.64 seconds respectively, without significant difference between both methods. The results confirmed the validity of the generally used transit time of seven seconds for SF calculation in cats. The average normal SF (± SD) for the cats in this study was 0.73 % (±0.74; range 0.11-2.48%).

scholarly journals Use of the mean transit time of an intravascular contrast agent as an exchange-insensitive index of myocardial perfusion

1999 ◽  
Vol 9 (3) ◽  
pp. 402-408 ◽  
Author(s):  
Massimo Lombardi ◽  
Richard A. Jones ◽  
J�rgen Westby ◽  
Geir Torheim ◽  
Timothy E. Southon ◽  
...  
Keyword(s):  
Myocardial Perfusion ◽  
Contrast Agent ◽  
Transit Time ◽  
Mean Transit Time ◽  
Intravascular Contrast Agent ◽  
The Mean

Abstract 37: Increased Mean Transit Time and Blood Brain Permeability in Asymptomatic White Matter Lesions of Ischemic Origin

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Blake Dewey ◽  
Xiang Xu ◽  
Linda Knutson ◽  
Amod Jog ◽  
Jerry Prince ◽  
...  
Keyword(s):  
White Matter ◽  
Transit Time ◽  
Gray Matter ◽  
Mean Transit Time ◽  
White Matter Lesions ◽  
Lesion Volume ◽  
Dynamic Susceptibility ◽  
Automated Segmentation ◽  
Blood Brain ◽  
Significant Difference

Introduction: White matter lesions of presumed ischemic origin (WMH) have been associated with increased risk of stroke, cognitive and motor decline, and are a subject of public health research. Engineering new MRI pipelines allowing for determination of mean transit time (MTT), and blood brain barrier permeability (BBBP), within WMH lesions is required for long-term population-based studies of lesion progression in patients with dementia and vascular cognitive impairment. Methods: WMH lesion volumes in 24 asymptomatic individuals was determined using an automated segmentation methodology, S3DL, with manual correction to remove false positives. A double contrast injection scheme was used to measure both K trans using dynamic contrast enhanced (DCE) imaging and K 2 using dynamic susceptibility contrast (DSC) imaging which also provided perfusion-related measures. BBBP was measured as k 2 within segmented WMH lesions and compared with normal white and gray matter. Results: The mean transit time (MTT) was found to be significantly prolonged (8.11, p<0.001Wilcoxon Signed-Rank Test) in WMH lesions when compared to normal appearing white and gray matter. There was no significant difference in DCE-K trans (0.018, p=0.351) between the lesions and the white/gray matter. Permeability measured in the WMH lesions using the DSC-K 2 method was increased and was correlated withincreasing total WMH lesion volume (spearman correlation 0.44; p< 0.046). Conclusion: In this first study using an advanced WMH lesion automated segmentation pipeline, we measured DCE and DSC perfusion and permeability variables within WMH lesions and compared them to normal white and grey matter in healthy people. We observed increasing MTT, within WMH lesions as compared to unaffected white and gray matter. Using the DSC-K 2 method, BBBP was higher within WMH lesions in these asymptomatic people, and correlated with increasing total lesion volume.

Lung water measurements with the mean transit time approach

1985 ◽  
Vol 59 (3) ◽  
pp. 673-683 ◽  
Author(s):  
R. M. Effros
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Tissue Perfusion ◽  
Time Data ◽  
Lung Water ◽  
Thermal Signal ◽  
The Mean ◽  
Points Of View ◽  
Vascular Obstruction ◽  
Pulmonary Vascular Obstruction

The potential usefulness and limitations of the double-indicator mean transit time approach for measuring lung water are evaluated from both theoretical and empirical points of view. It is concluded that poor tissue perfusion is the most serious factor that can compromise the reliability of this approach. Replacement of the conventional water isotopes with a thermal signal enhances indicator delivery to ischemic areas but the diffusion of heat is not sufficiently rapid to permit measurements of water in macroscopic collections of fluid which remain unperfused. The frequency of pulmonary vascular obstruction in patients with pulmonary edema related to lung injury suggests that interpretation of transit time data will be complicated by uncertainties concerning perfusion. Thermal-dye measurements of lung water may prove more helpful in situations where pulmonary blood flow remains relatively uniform.

scholarly journals Modeling radiocarbon dynamics in soils: SoilR version 1.1

2014 ◽  
Vol 7 (3) ◽  
pp. 3161-3192 ◽  
Author(s):  
C. A. Sierra ◽  
M. Müller ◽  
S. E. Trumbore
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Transit Time ◽  
Mean Transit Time ◽  
Time Data ◽  
Soil System ◽  
Linear Dynamical Systems ◽  
Natural Systems ◽  
Radiocarbon Data ◽  
The Mean

Abstract. Radiocarbon is an important tracer of the global carbon cycle that helps to understand carbon dynamics in soils. It is useful to estimate rates of organic matter cycling as well as the mean residence or transit time of carbon in soils. We included a set of functions to model the fate of radiocarbon in soil organic matter within the SoilR package for the R environment for computing. Here we present the main system equations and functions to calculate the transfer and release of radiocarbon from different soil organic matter pools. Similarly, we present functions to calculate the mean transit time for different pools and the entire soil system. This new version of SoilR also includes a group of datasets describing the amount of radiocarbon in the atmosphere over time, data necessary to estimate the incorporation of radiocarbon in soils. Also, we present examples on how to obtain parameters of pool-based models from radiocarbon data using inverse parameter estimation. This implementation is general enough so it can also be used to trace the incorporation of radiocarbon in other natural systems that can be represented as linear dynamical systems.

The Effects of Thromboxane Antagonism on the Transit Time of Platelets Through the Spleen

1985 ◽  
Vol 54 (02) ◽  
pp. 495-497 ◽  
Author(s):  
A M Peters ◽  
I F Lane ◽  
M Sinclair ◽  
J T C Irwin ◽  
C N McCollum
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Thromboxane A2 ◽  
Time Measurement ◽  
Thromboxane A2 Receptor ◽  
Group Research ◽  
The Mean ◽  
A Site ◽  
Kinetics Of ◽  
Transit Time Measurement

SummaryThe spleen is well-known as a site for platelet pooling, although the mechanisms controlling intrasplenic platelet transit are essentially unknown. We tested the possibility that thromboxane A2 might be involved in this control by measuring intrasplenic platelet transit time in 10 subjects receiving a specific thromboxane A2 receptor antagonist (AH23848B; 70 mg; Glaxo Group Research Ltd), in 10 receiving aspirin (300 mg) plus dipyridamole (75 mg), and in 9 receiving placebo. All doses were administered 3 times daily commencing 4 days prior to transit time measurement.Mean intrasplenic platelet transit time was measured by monitoring the kinetics of equilibration of 111In radiolabelled platelets between blood and spleen following intravenous injection. There was no difference between the mean transit time in the 3 groups of subjects, lending no support to the hypothesis that thromboxane A2 is involved in the control of platelet traffic through the spleen.

Comparison of methods for analyzing gastric isotope emptying

1982 ◽  
Vol 243 (3) ◽  
pp. G237-G242 ◽  
Author(s):  
M. C. Dugas ◽  
R. R. Schade ◽  
D. Lhotsky ◽  
D. Van Thiel
Keyword(s):  
Gastric Emptying ◽  
Transit Time ◽  
Gamma Camera ◽  
Statistical Difference ◽  
Mean Transit Time ◽  
Comparison Of Methods ◽  
Sulfur Colloid ◽  
The Mean ◽  
Linear Regressions ◽  
99Mtc Sulfur Colloid

The gastric emptying of 99mTc-sulfur colloid, ingested in a nutrient liquid test meal, was followed by gamma camera for normals, diabetics, and diabetics receiving intravenous metoclopramide. Gastric emptying patterns of 99mTc by these groups present as normal, slow, and rapid on simple graphic inspection. Half times of indicator emptying were computed from inspection and from least-squares linear regressions of log(base e) residue versus time for the total postpeak curve and for the remainder of the 15-min postpeak curve. In addition, the percent of 99mTc residue leaving at, and the area under, the residue curve until 6, 12, 24, and 60 min postpeak and the indicator mean transit time (MTT) were computed. Standard half-time determinations revealed no significant differences among the three groups, despite obvious visual differences among them. In contrast, the mean transit time of the rapid group was significantly less than that of the slow (P less than 0.01) and normal (P less than 0.05) groups. However, no statistical difference was noted between the slow and the normal emptiers (P greater than 0.1) using the MTT measure. The percent of particles leaving the stomach and the area under the residue curves demonstrated significant differences among the three groups, reflecting the obvious visual perceptions gained from simple curve inspection. Because the percent of indicator particles leaving the stomach region at a given time reflects a single time, it was concluded that the residue area represents the most reliable, objective, and quantifiable parameter for testing of significant differences.

scholarly journals A proof of the occupancy principle and the mean-transit-time theorem for compartmental models

1984 ◽  
Vol 68 (1) ◽  
pp. 121-136 ◽  
Author(s):  
Rajasekhar Ramakrishnan ◽  
Edward F. Leonard ◽  
Ralph B. Dell
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Compartmental Models ◽  
The Mean
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