Reproducibility of mean transit time for maximal myocardial flow assessment by videodensitometry

1990 ◽  
Vol 6 (2) ◽  
pp. 101-108 ◽  
Author(s):  
Nico H. J. Pijls ◽  
Gerard J. H. Uijen ◽  
Truus Pijnenburg ◽  
Karel van Leeuwen ◽  
Wim R. M. Aengevaeren ◽  
...  
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Myocardial Flow

Cerebral vascular mean transit time determined by PET and DSC-MRI

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S676-S676
Author(s):  
Masanobu Ibaraki ◽  
Hiroshi Ito ◽  
Eku Shimosegawa ◽  
Hideto Toyoshima ◽  
Keiichi Ishigame ◽  
...  
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Dsc Mri ◽  
Cerebral Vascular

scholarly journals Serial Quantitative Computed Tomography Perfusion in Aneurysmal Subarachnoid Hemorrhage

2016 ◽  
Vol 43 (3) ◽  
pp. 375-380 ◽  
Author(s):  
Cheemun Lum ◽  
Matthew J. Hogan ◽  
John Sinclair ◽  
Shane English ◽  
Howard Lesiuk ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Subarachnoid Hemorrhage ◽  
Middle Cerebral Artery ◽  
Transit Time ◽  
Cerebral Artery ◽  
Computed Tomography Angiography ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Mean Transit Time ◽  
Arterial Diameter ◽  
Computed Tomography Perfusion

AbstractPurpose: Computed tomography perfusion (CTP) has been performed to predict which patients with aneurysmal subarachnoid hemorrhage are at risk of developing delayed cerebral ischemia (DCI). Patients with severe arterial narrowing may have significant reduction in perfusion. However, many patients have less severe arterial narrowing. There is a paucity of literature evaluating perfusion changes which occur with mild to moderate narrowing. The purpose of our study was to investigate serial whole-brain CTP/computed tomography angiography in aneurysm-related subarachnoid hemorrhage (aSAH) patients with mild to moderate angiographic narrowing. Methods: We retrospectively studied 18 aSAH patients who had baseline and follow-up whole-brain CTP/computed tomography angiography. Thirty-one regions of interest/hemisphere at six levels were grouped by vascular territory. Arterial diameters were measured at the circle of Willis. The correlation between arterial diameter and change in CTP values, change in CTP in with and without DCI, and response to intra-arterial vasodilator therapy in DCI patients was evaluated. Results: There was correlation among the overall average cerebral blood flow (CBF; R=0.49, p<0.04), mean transit time (R=–0.48, p=0.04), and angiographic narrowing. In individual arterial territories, there was correlation between changes in CBF and arterial diameter in the middle cerebral artery (R=0.53, p=0.03), posterior cerebral artery (R=0.5, p=0.03), and anterior cerebral artery (R=0.54, p=0.02) territories. Prolonged mean transit time was correlated with arterial diameter narrowing in the middle cerebral artery territory (R=0.52, p=0.03). Patients with DCI tended to have serial worsening of CBF compared with those without DCI (p=0.055). Conclusions: Our preliminary study demonstrates there is a correlation between mild to moderate angiographic narrowing and serial changes in perfusion in patients with aSAH. Patients developing DCI tended to have progressively worsening CBF compared with those not developing DCI.

Probable range for whole kidney mean transit time values determined by reexamination of UK audit studies

2008 ◽  
Vol 29 (11) ◽  
pp. 1006-1014 ◽  
Author(s):  
Cyril C. Nimmon ◽  
John S. Fleming ◽  
Martin Šámal
Keyword(s):  
Transit Time ◽  
Mean Transit Time

scholarly journals The Effects of Changes in PaCO2Cerebral Blood Volume, Blood Flow, and Vascular Mean Transit Time

Stroke ◽  
1974 ◽  
Vol 5 (5) ◽  
pp. 630-639 ◽  
Author(s):  
ROBERT L. GRUBB ◽  
MARCUS E. RAICHLE ◽  
JOHN O. EICHLING ◽  
MICHEL M. TER-POGOSSIAN
Keyword(s):  
Blood Flow ◽  
Blood Volume ◽  
Transit Time ◽  
Mean Transit Time ◽  
Volume Blood ◽  
Volume Blood Flow

scholarly journals Aggregation in environmental systems: seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments

2015 ◽  
Vol 12 (3) ◽  
pp. 3059-3103 ◽  
Author(s):  
J. W. Kirchner
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Strong Nonlinearity ◽  
Isotopic Tracers ◽  
Water Fraction ◽  
Benchmark Tests ◽  
Environmental Systems ◽  
Transit Times ◽  
Event Based ◽  
The Relationship

Abstract. Environmental heterogeneity is ubiquitous, but environmental systems are often analyzed as if they were homogeneous instead, resulting in aggregation errors that are rarely explored and almost never quantified. Here I use simple benchmark tests to explore this general problem in one specific context: the use of seasonal cycles in chemical or isotopic tracers (such as Cl−, δ18O, or δ2H) to estimate timescales of storage in catchments. Timescales of catchment storage are typically quantified by the mean transit time, meaning the average time that elapses between parcels of water entering as precipitation and leaving again as streamflow. Longer mean transit times imply greater damping of seasonal tracer cycles. Thus, the amplitudes of tracer cycles in precipitation and streamflow are commonly used to calculate catchment mean transit times. Here I show that these calculations will typically be wrong by several hundred percent, when applied to catchments with realistic degrees of spatial heterogeneity. This aggregation bias arises from the strong nonlinearity in the relationship between tracer cycle amplitude and mean travel time. I propose an alternative storage metric, the young water fraction in streamflow, defined as the fraction of runoff with transit times of less than roughly 0.2 years. I show that this young water fraction (not to be confused with event-based "new water" in hydrograph separations) is accurately predicted by seasonal tracer cycles within a precision of a few percent, across the entire range of mean transit times from almost zero to almost infinity. Importantly, this relationship is also virtually free from aggregation error. That is, seasonal tracer cycles also accurately predict the young water fraction in runoff from highly heterogeneous mixtures of subcatchments with strongly contrasting transit time distributions. Thus, although tracer cycle amplitudes yield biased and unreliable estimates of catchment mean travel times in heterogeneous catchments, they can be used reliably to estimate the fraction of young water in runoff.

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