Mean Passage Time Research Articles

Conceptualization of a functional random walker for the analysis of socio-technical systems

The Functional Resonance Analysis Method (FRAM) has been pointed out by several prior studies as an effective approach for modeling socio-technical systems. Despite previous contributions, FRAM still suffers from limited tractability in case of large models such as a difficulty of carrying out reliable and insightful analysis. This paper addresses this gap by proposing an approach inspired by network theory to enhance traditional FRAM analyses, namely the functional random walker (FRW). The definition of FRW complements the notion of random walks accounting for the variability being transferred inside the system from one function to another, offering a cost-effective means of exploring FRAM instantiations. Five design criteria are presented to reproduce such analysis with any FRAM model, along with two indicators, namely the probability of visiting nodes and the mean passage time. These two metrics permit to study the FRAM model both at function level (how a single function behaves within the model) and at system level (how multiple functions interact with each other). A walk-through application of FRW is presented for a healthcare setting. This application revealed how the FRW sheds light on systems’ strengths and vulnerabilities, and highlighted underlying knowledge, otherwise hidden in cluttered visual representations of FRAM instantiations.

Evaluation of microcirculation in asymptomatic cerebral infarction with multi-parameter imaging of spectral CT

ObjectiveTo investigate the role of spectral CT multiparametric imaging in the evaluation of cerebral microcirculatory perfusion. MethodsThe imaging data of 145 patients with asymptomatic cerebral infarction confirmed by MR were retrospectively analyzed, and all cases underwent head CTA and cranial CT perfusion imaging (CTP) on double-layer detector spectral CT. Single energy level images (MonoE45 keV), iodine density maps, and effective atomic number maps were reconstructed based on spectral CTA data, and CT values, iodine density values, and effective atomic number values were measured in the infarcted area, healthy control area, centrum semiovale and posterior limb of the internal capsule, respectively; perfusion values, such as cerebral blood volume (CBV) values, cerebral blood flow (CBF) values, time to peak (TTP) values, and mean passage time, were measured in the above-mentioned areas on CTP images. (TTP) values, and mean time to passage (MTT) values. CT values, iodine density values, effective atomic number values, and perfused CBV, CBF, TTP, and MTT values were compared between the infarcted area and the healthy side, the center of the hemianopia, and the posterior limb of the internal capsule. The role of spectral CT parameters and perfusion parameters in the evaluation of asymptomatic cerebral infarction was analyzed. ResultsCT values, iodine density values, and effective atomic number values were statistically different between the infarcted area and the healthy side; CT values, iodine density values, and effective atomic number values were not statistically different between the infarcted side and the healthy side of the hemispheric centrum and the posterior limb of the internal capsule; CBV and CBF were statistically different between the infarcted side and the healthy side, and MTT and TTP were not statistically different. There were statistically significant differences in TTP between the infarcted area and the healthy side of the hemiaxial center, and no statistically significant differences in CBV, CBF, and MTT. There were no statistical differences in CBV, CBF, TTP, and MTT in the inner capsule area. ROC curve analysis of spectral CT-related parameters and CT perfusion parameters for the diagnosis of asymptomatic cerebral infarction: area under the curve of MonoE 45Kv 0.71, area under the curve of iodine density values 0.76, area under the curve of effective atomic number values 0.74; area under the curve of CBV value 0.64, area under the curve of CBF value 0.61, area under the curve of MTT value 0.50, The area under the TTP curve was 0.52. The area under the ROC curve of the multivariate logistic regression model based on spectral parameters is 0.76, which is higher than that of the logistic regression model with perfusion parameters (P < 0.05). ConclusionSpectral CT can better demonstrate small intracranial ischemic lesions, and iodine density values have a better evaluation of microcirculation in asymptomatic cerebral infarcts.

Effect of dietary fiber on fecal androgens levels: An experimental analysis in brown brocket deer (Mazama gouazoubira)

Non-invasive endocrinology is an important tool for animal conservation, but its success depends on many factors (e.g. adequate hormonal extraction, diet, antibody used in the assay). Dietary fiber is one of the main sources that can lead to erroneous interpretation of the endocrine status provided by EIA analysis. This study aimed to evaluate the dietary fiber effect on the fecal androgen metabolites (FAM) detection, on the daily defecation rate and fecal production, as well as to analyze the gastrointestinal passage and retention time of the experimental diets. Eight brown brocket deer (Mazama gouazoubira) males were randomly assigned to two groups and submitted to both isocaloric and isoproteic experimental diets for 10 days, in a crossover system: low fiber percentage feed (LF, 7% fiber) and high fiber percentage feed (HF, 19% fiber). Such groups were alternated in the middle of this period, with an interval of 10 days between them. In addition, there was a five-day adaptation phase at the beginning of each diet. Fecal collection for FAM measurement was performed during 10 days of treatment, whereas,the defecation rate and fecal production were performed every two hours, for 6 days. The mean FAM level in the HF group was 5038.0 ± 1529.1 ng/g, while for LF, 2178.7 ± 824.9 ng/g (p < 0.05). The mean HF fecal production was 182.6 ± 36.2 g DM/day and 117.5 ± 12.6 g DM/day for LF (p < 0.05). There were no differences in terms of mean defecation rate, passage, and retention times between groups. The results suggest that dietary fiber affects the FAM detection, and this should be taken into consideration before conducting experiments using fecal samples as a source of reproductive hormones profiling.

A logistic function to track time-dependent fish population dynamics

This paper uses a two-parameter logistic function to model the dynamics of length-at-maturation for the Barents Sea capelin over the past 47 years. We estimate the function parameters using a combination of length-age data from scientific surveys, and commercial catch statistics.Using temporal variability in the function parameters, we demonstrate that the time series of stock biomass defines a three-state Markov process, that qualitatively represent high, moderate, and collapse states of the stock biomass. We make inference about transition times between the states by calculating the mean passage times for the Markov process.Our analyses also show that maturation intensity is higher at low stock size (leading to shorter lengths at maturation), compared to when biomass levels are either high or moderately high. Our results are central to management of this stock, as uncertainty in estimating the proportion of maturing biomass affects harvest decisions and ultimately, the sustainability of the stock.

Anatomic-radiographic aspects and gastrointestinal transit time in boa constrictor amarali stull, 1932 (Squamata, Boidae)

ABSTRACT The goal of this study was to describe the gastrointestinal transit technique in the Boa constrictor amarali. For that purpose, we obtained simple radiographic images of seven serpents, subsequently administering a 25mL/kg dose of barium sulfate and establishing a radiographic sequence at the following times: 5 minutes; 1, 2, 3, 6, 9, 24, 48, 72 and 96 hours, extending to 120 and 126 hours for one animal. The mean esophageal transit was 26.71±19.48 hours; the mean gastric filling time was 28.57±27.22 minutes and the emptying time was 60±12 hours; the mean filling time of the contrast medium in the small intestine was 3±2.16 hours and the emptying time was 97±15.65 hours. We also obtained the mean filling time of the large intestine, which was 40±11.31 hours. We found that the mean passage time of the contrast medium through the cranial gastrointestinal tract - until the complete elimination of barium sulfate from the small intestine -was 97±15.65 hours. In addition to determining the gastrointestinal transit time, the technique used allowed for the morphological identification of the alimentary canal.

Collective navigation can facilitate passage through human-made barriers by homeward migrating Pacific salmon.

The mass migration of animals is one of the great wonders of the natural world. Although there are multiple benefits for individuals migrating in groups, an increasingly recognized benefit is collective navigation, whereby social interactions improve animals’ ability to find their way. Despite substantial evidence from theory and laboratory-based experiments, empirical evidence of collective navigation in nature remains sparse. Here we used a unique large-scale radiotelemetry dataset to analyse the movements of adult Pacific salmon (Oncorhynchus sp.) in the Columbia River Basin, USA. These salmon face substantial migratory challenges approaching, entering and transiting fishways at multiple large-scale hydroelectric mainstem dams. We assess the potential role of collective navigation in overcoming these challenges and show that Chinook salmon (O. tshawytscha), but not sockeye salmon (O. nerka) locate fishways faster and pass in fewer attempts at higher densities, consistent with collective navigation. The magnitude of the density effects were comparable to major established drivers such as water temperature, and model simulations predicted that major fluctuations in population density can have substantial impacts on key quantities including mean passage time and fraction of fish with very long passage times. The magnitude of these effects indicates the importance of incorporating conspecific density and social dynamics into models of the migration process. Density effects on both ability to locate fishways and number of passage attempts have the potential to enrich our understanding of migratory energetics and success of migrating anadromous salmonids. More broadly, our work reveals a potential role of collective navigation, in at least one species, to mitigate the effects of anthropogenic barriers to animals on the move.

Clinical value of brain CT perfusion imaging combined with head and neck CTA in the diagnosis of acute ischemic stroke

Objective To investigate the clinical value of whole brain CT perfusion imaging combined with head and neck CTA in the diagnosis of acute ischemic stroke. Methods From November 2016 to November 2018, the clinical data and medical imaging data of 220 patients diagnosed as acute ischemic stroke in the Department of Neurology, Dajiangdong Hospital were selected.All patients underwent CT scan followed by a CT perfusion scan and a routine cranial CTA.The radiation dose was recorded.The ischemic lesions and their stenosis were analyzed by CTA.CT perfusion imaging was used to analyze regional cerebral blood flow imaging (rCBF), tissue perfusion (rCBV) and mean passage time (MTT) in all patients..And the test performance of the two inspection methods was compared. Results CTA was used to analyze vascular stenosis.The stenotic vessels were mainly distributed in the M1~M3 segment (3 cases of them were completely obstructed, 11 cases were obstructed ≥50%, 19 cases were 30% ≤ stenosis<50%), and A1~A3 segments (4 cases of them were obstructed, 7 cases were 30% ≤ stenosis<50%), and basilar artery (2 cases of them occlusion, 6 cases of ≥ 50%, 11 cases of 30% ≤ stenosis<50%). CT perfusion examination was performed in the whole brain.The rCBF of the control area was higher than that of the ischemic penumbra and higher than the infarct area.The rCBF values were (50.31±11.21)100 g/min, (34.45±22.17)100 g/min and (6.87±3.52)100 g/min, respectively, the difference was statistically significant (t=17.81, 19.14, all P<0.05). The region rCBV of the control area was higher than that of the ischemic penumbra and the infarct region, and the rCBV values were (3.35±1.01)mL/100g, (2.87±0.55)mL/100g and (6.87±0.51)mL/100g, respectively, the differences are statistically significant (t=6.47, 9.19, all P<0.05). The MTT in the control area was lower than that in the ischemic penumbra and the infarct area, and the MTT values were (4.52±1.21)s, (7.88±1.01)s and (11.81±1.18)s, respectively, the differences are statistically significant(t=10.50, 13.54, all P<0.05). The two methods were compared for consistency, and the kappa value was greater than 0.75, showed a high degree of consistency. Conclusion CT perfusion imaging and CTA have little difference in the diagnostic efficacy for patients with acute ischemic cerebral infarction, and can accurately diagnose the disease.CT perfusion imaging can determine the location of the ischemic penumbra, and CTA can be analyzed based on the stage of the diseased vessel.Both two methods can play different guiding role for individualized treatment. Key words: Tomography, spiral computed; Perfusion imaging; Angiography; Cerebrovascular disorders; Retrospective study

Multiple Cerebrovascular Occlusion With Hypothyroidism: A Powerful Compensation

Cerebral vascular occlusion can often cause severe neurological deficits. This study aims to describe a case characterized by multiple large vessel occlusions with hypothyroidism and without clinical symptoms. The patient’s blood vessel condition, compensatory pathway and perfusion situation were understood through medical history inquiry, neurological physical examination, combined with blood lipid, blood glucose, electrocardiogram, transcranial Doppler (TCD), brain computed tomography (CT), cerebral angiography, cerebral perfusion imaging and other examinations. The main symptoms of the patient were dizziness and headache, with no symptoms of neurological function loss. Digital subtraction angiography (DSA) showed multiple large vessel occlusions in the head and neck: the initial part of the left internal carotid artery, the M1 segment of the left middle cerebral artery, the V2 segment of the right vertebral artery, and the V3 terminal segment of the left vertebral artery. According to CT perfusion (CTP) examination, the blood flow (BF) value of the left temporoparietal occipital lobe was lower than that of the contralateral side, the mean blood flow passage time value was increased, and the cerebral blood volume (BV) was slightly higher than that of the contralateral side. Cerebral vascular occlusion is affected by many factors, hypothyroidism can accelerate the process of atherosclerosis, and in severe cases multiple large vessel occlusions may occur. Powerful compensatory mechanisms can reduce the incidence of stroke. J Med Cases. 2019;10(6):158-163 doi: https://doi.org/10.14740/jmc3303

Providing refuges for adult Pacific lamprey Entosphenus tridentatus inside fishways

Fishways at hydroelectric dams are unnatural environments that typically present fish with channels of uniform depth, variable water velocity, and lack of cover. Fish retention and overall passage success may be improved by providing rest and sheltering areas inside fishways. We examined adult Pacific lamprey Entosphenus tridentatus use of two specially designed fishway refuges at Bonneville Dam on the Columbia River (northwestern USA). These relatively small boxes (1.1 m × 0.4 m × 0.2 m) provided low-velocity, dark refuge from predation for Pacific lamprey, a largely nocturnal species. Refuge boxes were equipped with antennas to detect entry of lamprey tagged with passive integrated transponder (PIT) tags. We PIT tagged and released 3,247 lamprey, including 599 that were double-tagged with a PIT and a radio transmitter, over three study years (2012–2014). In each year, PIT-tagged lamprey detected at nearby fishway exits had used a refuge: 12% in 2012, 28% in 2013, and 36% in 2014. Median residence time of PIT-tagged lamprey in the refuges for each year was 20.3 h, 16.6 h, and 13.1 h. Lamprey entrance into refuges peaked at 0300–0500 PDT, and they typically exited at around 2000 PDT, suggesting that refuges primarily functioned as shelter from daylight. Probability of refuge use increased with a morphological indicator of sexual maturity (distance between dorsal fins). In the radio-tagged group, refuge users were equally likely to pass Bonneville Dam as non-users. However, refuge users were less likely than non-users to be detected at sites upstream from the dam, perhaps owing to their maturation status or longer mean passage time through our study area (2.0 vs. 0.6 d for non-users). Refuges show promise for improving fish retention in fishways, particularly for nocturnal and/or small-bodied species that seek shelter from light or predation.

Multiple Cerebrovascular Occlusion With Hypothyroidism: A Powerful Compensation

Cerebral vascular occlusion can often cause severe neurological deficits. This study aims to describe a case characterized by multiple large vessel occlusions with hypothyroidism and without clinical symptoms. The patient’s blood vessel condition, compensatory pathway and perfusion situation were understood through medical history inquiry, neurological physical examination, combined with blood lipid, blood glucose, electrocardiogram, transcranial Doppler (TCD), brain computed tomography (CT), cerebral angiography, cerebral perfusion imaging and other examinations. The main symptoms of the patient were dizziness and headache, with no symptoms of neurological function loss. Digital subtraction angiography (DSA) showed multiple large vessel occlusions in the head and neck: the initial part of the left internal carotid artery, the M1 segment of the left middle cerebral artery, the V2 segment of the right vertebral artery, and the V3 terminal segment of the left vertebral artery. According to CT perfusion (CTP) examination, the blood flow (BF) value of the left temporoparietal occipital lobe was lower than that of the contralateral side, the mean blood flow passage time value was increased, and the cerebral blood volume (BV) was slightly higher than that of the contralateral side. Cerebral vascular occlusion is affected by many factors, hypothyroidism can accelerate the process of atherosclerosis, and in severe cases multiple large vessel occlusions may occur. Powerful compensatory mechanisms can reduce the incidence of stroke. J Med Cases. 2019;10(6):158-163 doi: https://doi.org/10.14740/jmc3303

Transitions from low-density state towards high-density state in stochastic bistable plasma-condensate systems

In this article we study transitions from low-density states towards high-density states in bistable plasma-condensate systems. We take into account an anisotropy in transference of adatoms between neighbour layers induced by the electric field near substrate. We derive the generalized one-layer model by assuming that the strength of the electric field is subjected to both periodic oscillations and multiplicative fluctuations. By studying the homogeneous system we discuss the corresponding mean passage time. In the limit of weak fluctuations, we show the optimization of the mean passage time with variation in the frequency of periodic driving in the non-adiabatic limit. Noise induced effects corresponding to asynchronization and acceleration in the transition dynamics are studied in detail.

Decoding and modelling of time series count data using Poisson hidden Markov model and Markov ordinal logistic regression models.

Hidden Markov models are stochastic models in which the observations are assumed to follow a mixture distribution, but the parameters of the components are governed by a Markov chain which is unobservable. The issues related to the estimation of Poisson-hidden Markov models in which the observations are coming from mixture of Poisson distributions and the parameters of the component Poisson distributions are governed by an m-state Markov chain with an unknown transition probability matrix are explained here. These methods were applied to the data on Vibrio cholerae counts reported every month for 11-year span at Christian Medical College, Vellore, India. Using Viterbi algorithm, the best estimate of the state sequence was obtained and hence the transition probability matrix. The mean passage time between the states were estimated. The 95% confidence interval for the mean passage time was estimated via Monte Carlo simulation. The three hidden states of the estimated Markov chain are labelled as 'Low', 'Moderate' and 'High' with the mean counts of 1.4, 6.6 and 20.2 and the estimated average duration of stay of 3, 3 and 4 months, respectively. Environmental risk factors were studied using Markov ordinal logistic regression analysis. No significant association was found between disease severity levels and climate components.

Some analysis of a stochastic logistic growth model

ABSTRACTWe derive several new results on a well-known stochastic logistic equation. For the martingale case, we compute the distribution of the solution, mean passage times, and the distribution of hitting times, all in closed form. For the case of constant coefficients, we also find mean passage times and for the general equation we give the weak solution expressed in terms of stochastic quadratures. We also show how these quadratures may be considerably simplified using the results for the martingale case. As it turns out, the martingale case has a particularly elegant weak solution, and to a large degree its structure carries over to the general case.

Volume increment modeling and subsidies for the management of the tree Mora paraensis (Ducke) Ducke based on the study of growth rings

First study that demonstrated the formation of annual growth rings in Amazonian Estuary trees. Growth patterns of Mora paraensis and specific management criteria, such as felling cycle, are presented. The aim of the present study was to contribute to increased sustainability in the timber management of Mora paraensis, through the estimation of minimum logging diameter (MLD) and felling cycle, using volume increment models based on tree-ring analysis and allometric relationships. We collected stem discs from 17 trees of five diameter classes. The diameters and heights of the trees were also measured. We estimated tree ages by ring-counting and the radial increment rates by measuring the ring widths with a digital analysis system. We built growth models based on relationships between age, diameter and tree height to estimate volume increment along the tree’s whole life cycle. The maximum current diameter increment in M. paraensis occurs at an age of around 26 years, reaching 4.91 mm year-1. The MLD was 46.4 ± 0.6 cm (standard error), which trees achieve at an age of about 115 years. The felling cycle, estimated by the mean passage time through 10 cm diameter classes until achieving the MLD, was 24.7 ± 1.3 years. These results corroborated the norms of the current Brazilian legislation that regulates forest management of high intensity in the Amazon basin. In future, more specific growth models are needed for other commercial tree species in the Amazonian Estuary to define the optimal harvest rate to maintain sustainable timber resource management practices. Through such practices, the conservation of these ecosystems and their multiple services and functions, as well as the welfare of the forest-dependent human populations can be secured.

Stochastic transitions between attractors in a tristable thermochemical system: competition between stable states

We present the thermochemical model in the tristable regime which is characterized by three distinct attractors: two stationary states and a limit cycle. Transitions between the attractors are studied on the basis of the stochastic dynamics at the mesoscopic level, in which internal fluctuations are described by means of the master equation. Simulations of the stochastic dynamics follow the master equation, which has the specific form due to the necessary description of a continuous spectrum of temperature changes related to the exchange of energy with a thermostat. The mean first passage times are calculated for transitions from the limit cycle to each stable steady state. The effect of competition between the states is demonstrated: the duration of the passage can be strongly increased if the system during the transition to one state is also visiting the second competitive one. The variation of the passage times is studied for systems with different reaction heat, and the obtained dependence is explained by the location of the attractors and repellers in the phase space of system temperature and composition. The proportion between the mean passage times for the two states can be related to their relative strength of attraction.

Simplified Analysis for the Association of a Constrained Receptor to an Oscillating Ligand

The stability of a bond cluster upon oscillated loads under physiological conditions is strongly regulated by the kinetics of association and dissociation of a single bond, which can play critical roles in cell–matrix adhesion, cell–cell adhesion, etc. Here, we obtain a simplified analysis for the bond association process of a constrained receptor to an oscillating ligand due to its diffusion-independence, which can facilitate the potential multiscale studies in the future. Based on the analysis, our results indicate that the mean passage time for bond association intriguingly saturates at high oscillating frequencies, and there can also surprisingly exist optimal bond elasticity for bond association. This work can bring important insights into understanding of the behaviors of bond cluster under cyclic loads at the level of a single bond.

Longitudinal data analysis of mean passage time among malnutrition states: an application of Markov chains

ABSTRACTClinical prognosis of patients can be best described from a longitudinal study and a Markov regression model is an appropriate way of analyzing the prognosis of disease when the outcomes are serially dependent. Mean first passage time (MFPT) is a method to estimate the average number of transitions between the states of a Markov chain. The present study used the secondary data from a longitudinal study which was done during 1982–1986. This study was to illustrate the MFPT among the states of malnutrition, which were classified as Normal, Mild/Moderate andSevere among children aged 5–7 years, in South India. The 95% confidence interval (CI) for the MFPT was calculated using Monte Carlo simulation. Markov regression models were used to test for the association of state transitions across the risk factors. The average time taken for an underweight child to transit from Severe state of malnutrition to become Normal was nearly 2.73 (95% CI 2.60–2.86) years and 3.41 (95% CI 3.25–3.58) years in Rural area and 2.31(95% CI 2.20–2.42) in Urban area. The significant difference between the MFPT for some risk factors are useful to plan interventions. It will especially be useful to find the impact of duration among school-going children on their cognitive disorders.

Age and Growth Patterns of Brazil Nut Trees (Bertholletia excelsa Bonpl.) in Amazonia, Brazil

AbstractVarious techniques have been used to estimate the age of Brazil nut trees (Bertholletia excelsa Bonpl.), but these techniques produce large discrepancies. Here, we first verified that two individuals of known ages from a plantation in central Amazonia, Brazil, have a congruent number of growth rings. The indexed average tree‐ring curve was significantly correlated with total precipitation during the rainy season (November–June) over a 50‐yr period, confirming the annual nature of the tree rings. Second, we analyzed Brazil nut trees from two populations in the Trombetas (eastern Amazon) and Purus (central Amazon) regions, performing tree‐ring analysis to estimate tree age and diameter increment rates. We compared age–diameter relationships, mean passage time through 10‐cm diameter size classes, and growth trajectories of individual trees. The maximum age of Brazil nut trees analyzed was 361 yr in the Purus and 401 yr in the Trombetas. Trees at the Purus site had higher mean diameter increment rates and showed more variation compared to trees at the Trombetas site. Individual growth trajectories show that the majority of trees attained the canopy by direct growth, while a smaller number passed through one release or one suppression event before becoming established in the canopy. None of the trees passed through multiple release and suppression events. The age estimations presented here are comparable to previous tree‐ring analyses for the species, and the observed growth patterns support earlier work indicating B. excelsa as a gap‐dependent tree species.

Factors predicting the spontaneous passage of a ureteric calculus of ⩽10 mm

ObjectiveTo evaluate the outcome of the expectant management of ureteric stones and to determine the factors predictive of the spontaneous passage of stones. Patients and methodsWe retrospectively reviewed the medical records of patients who had ureteric stones of ⩽10mm and who were treated conservatively at our institutions during the period 2008–2013. The stone-passage rate and time, and different clinical, laboratory and radiological variables, were analysed. ResultsIn all, 163 patients with ureteric stones were enrolled in the study, of whom 127 (77.9%) passed their stones spontaneously, with a mean (SD) passage time of 24.0 (8.09)days. The cumulative stone-passage rate was 1.6%, 15%, 41.7%, 72.4%, 89.8% and 98.4% at 7, 14, 21, 28, 35 and 42days from the first presentation, respectively. Patients with a high pain-scale score, stones of ⩽5mm, a lower ureteric stone, a high white blood cell count and those with absent computed tomography (CT) findings of perinephric fat stranding (PFS) and tissue-rim sign (TRS) had a higher likelihood of spontaneous stone passage. Patients with stones of ⩽5mm, stones in the lower ureter and those with no PFS had a shorter spontaneous passage time. In a multivariate analysis the absence of PFS and TRS were the only significant predictors for spontaneous stone passage (P<0.001 and 0.002, respectively). ConclusionsThe spontaneous ureteric stone-passage rate and time varies with different factors. The absence of CT findings of PFS and TRS are significant predictors for stone passage, and should be considered when choosing the expectant management.

Evaluation of Circulation Disorder in Coronary Slow Flow by Fundus Fluorescein Angiography

Coronary slow flow (CSF) may be a reflection of a systemic slow-flow phenomenon in the coronary arterial tree. In this study, the CSF group consisted of 24 men (77.4%) and 7 women (22.5%). An age- and gender-matched normal coronary artery (control) group was composed of 21 men (72.4%) and 8 women (27.5%). Retinal arteriovenous circulation time was measured using fundus fluorescein angiography as a part of the microcirculation and the circulation time between the antecubital vein and the retina as a part of the systemic circulation in patients with CSF and controls with normal coronary arteries. The mean arm-retina circulation time was 19.0 ± 5.7 seconds in the CSF group and 14.1 ± 3.1 seconds in the control group (p <0.001). The mean retinal arteriovenous passage time was 2.6 ± 0.9 seconds in the CSF group and 2.1 ± 0.7 seconds in the control group (p= 0.001). Strikingly, retinal findings of chronic central serous retinopathy were observed in 3 patients in the CSF group. In conclusion, CSF may indeed be a part of a systemic slow-flow phenomenon. The association of central serous retinopathy with this condition suggests that corticosteroids and the sympathetic system may play important roles in the pathogenesis of the disease by causing or contributing to increases in microvascular resistance and tonus.