Transit time ultrasound perivascular flow probe technology is superior to MR imaging on hepatic blood flow measurement in a porcine model

Background: The hepatic hemodynamics is an essential parameter in surgical planning as well as in various disease processes. The transit time ultrasound(TTUS) perivascular flow probe technology is widely used in clinical practice to evaluate the hepatic inflow, yet invasive. The phase-contrast-MRI(PC-MRI) is not invasive and potentially applicable in assessing the hepatic blood flow. In the present study, we compared the hepatic inflow rates using the PC-MRI and the TTUS probe, and evaluated their predictive value of post-hepatectomy adverse events. Methods: Eighteen large white pigs were anaesthetized for PC-MRI and approximately 75% hepatic resection was performed under a unified protocol. The blood flow was measured in the hepatic artery(Qha), the portal vein(Qpv), and the aorta above the celiac trunk(Qca) using PC-MRI, and was compared to the TTUS probe. The Bland-Altman method was conducted and a partial least squares regression(PLS) model was implemented. Results: The mean Qpv measured in PC-MRI was 0.55 ± 0.12 L/min, and in the TTUS probe was 0.74 ± 0.17 L/min. Qca was 1.40 ± 0.47 L/min in the PC-MRI and 2.00 ± 0.60 L/min in the TTUS probe. Qha was 0.17 ± 0.10 L/min in the PC-MRI, and 0.13 ± 0.06 L/min in the TTUS probe. The Bland-Altman method revealed that the estimated bias of Qca in the PC-MRI was 32%(95% CI:-49% to 15%); Qha 17%(95% CI:-15% to 51%); and Qpv 40%(95% CI:-62% to 18%). The TTUS probe had a higher weight in predicting adverse outcomes after 75% resection compared to the PC-MRI( β= 0.35 and 0.43 vs β = 0.22 and 0.07, for tissue changes and premature death, respectively). Conclusions: There is a tendency of the PC-MRI to underestimate the flow measured by the TTUS probes. The TTUS probe measures are more predictive of relevant post-hepatectomy outcomes.

Measuring Acoustic Wave Transit Time in Furnace Based on Active Acoustic Source Signal

Accurate measurement of transit time for acoustic wave between two sensors installed on two sides of a furnace is a key to implementing the temperature field measurement technique based on acoustical method. A new method for measuring transit time of acoustic wave based on active acoustic source signal is proposed in this paper, which includes the followings： the time when the acoustic source signal arrives at the two sensors is measured first; then, the difference of two arriving time arguments is computed, thereby we get the transit time of the acoustic wave between two sensors installed on the two sides of the furnace. Avoiding the restriction on acoustic source signal and background noise, the new method can get the transit time of acoustic wave with higher precision and stronger ability of resisting noise interference.

Study of capillary transit time distribution in coherent hemodynamics spectroscopy

A recently proposed analytical hemodynamie modell[s.Fantini,Neurolmage 85,202-221(2014)]is able to predict the changes of oxy,deoxy,and total hemoglobin concentrations(model outputs)given arbitrary changes in blood flow,blood volume,and rate of oygen consumption(model inputs).One asumption of this model is that the capillary compartment is characterized by a single blood transit time.In this work,we have extended the original model by considering a distribution of capillary transit times and we have compared the outputs of both models(original and extended)for the case of sinusoidal input signals at different frequencies,which realizes the new technique of coherent hemodynamics spectroscopy(CHS).For the calculations with the original model,we have used the mean value of the distribution of capillary transit times con-sidered in the extended model.We have found that,for distributions of capillary transit times having mean values around 1 s and a standard deviation less than about 45%of the mean value,the original and extended models yield the same CHS spectra(i.e.,model outputs versus fre-quency of ocillation)within typical experimental errors.For wider capillary transit time dis-tributions,the two models yield different CHS spectra.By assuming that Poiseuille's law is valid in the capillary compartment,we have related the distribution of capillary transit times to the distributions of capillary lengths and capillary speed of blood flow to calculate the average capillary and venous saturations.We have found that,for standard deviations of the capillanry transit time distrilbution that are less than about 80%of the mean value,the average capillary saturation is always larger than the venous saturation.By contrast,the average capillary satu-ration may be less than the venous saturation for wider distributions of the capillary transit times.

Analytical Modeling of Base Transit Time of SiGe HBTS Including Concentration Dependent Bandgap Narrowing Effect

Heterojunction Bipolar Transistors with SiGe base and Si emitter and collector have increasingly become important in high speed applications in electronics due to better performance of these devices with a modest increase in complexity of fabrication process. Speed of these devices is mainly determined by transit time of minority carriers across the device. Base transit time is the most important component of the total transit time. An analytical model is developed here to predict the variation of base transit time with Ge content, base doping concentration, temperature, and other device parameters. Studies have been made for both uniform and exponential doping distributions with different Ge profiles in the base region. Band gap narrowing effect due to high doping concentration is also taken into account in the model.

Effect of small bowel transit time on accuracy of video capsule endoscopy in evaluating suspected small bowel bleeding

BACKGROUND Obscure small bowel bleeding is defined as gastrointestinal bleeding(GIB)that is unidentifiable with esophagogastroduodenoscopy and a colonoscopy with video capsule endoscopy(VCE)being the next gold standard step for evaluation.Small bowel transit time(SBTT)is a metric of a VCE study that is defined as the time the capsule takes to travel through the small intestine.AIM To determine if SBTT within the VCE study,correlates to overall detection of obscure small bowel bleeds.Furthermore,we attempted to identify any existing correlation between SBTT and re-bleeding after a negative VCE study.METHODS This is a single center retrospective analysis of VCE studies performed for overt and occult GIB at Einstein Medical Center,Philadelphia,between 2015 and 2019.Inclusion criteria primarily consisted of patients 18 years or older who had a VCE study done as part of the workup for a GIB.Patients with incomplete VCEs,poor preparation,or with less than 6 mo of follow up were excluded.A re-bleeding event was defined either as overt or occult within a 6-mo timeframe.Overt rebleeding was defined as Visible melena or hematochezia with>2 gm/dL drop in hemoglobin defined an overt re-bleeding event;whereas an unexplained>2 gm/dL drop in hemoglobin with no visible bleeding defined an occult re-bleed.RESULTS Results indicated that there was a significant and positive point biserial correlation between SBTT of 220 min and detection of a bleeding focus with a statistically significant p value of 0.008.However,the area under the curve was negligible when trying to identify a threshold time for SBTT to discriminate between risk of re-bleeding events after a negative VCE.CONCLUSION In terms of SBTT and association with accuracy of VCE finding a bleeding focus,220 min was found to be adequate transit time to accurately find a bleeding focus,when present.It was found that no threshold SBTT could be identified to help predict re-bleeding after a negative VCE.

Increased colon transit time and faecal load in irritable bowel syndrome

BACKGROUND Irritable bowel syndrome(IBS)is a bowel disorder involving abdominal pain or discomfort along with irregularity of stool form and passage frequency.The pathophysiology is poorly understood and seems to be multifactorial.Investigations of possible causes of IBS have included only a few colonic transit studies and no simultaneous determination of the colonic faecal content.AIM To compare colon transit time and faecal load between IBS-patients and healthy control subjects.METHODS The study included 140 patients with IBS,with a mean age of 50.0 years.The control group comprised 44 healthy persons with a mean age of 43.4 years,who were selected at random from the National Civil Register.Both the patient group and the control group underwent a marker study to measure colon transit time(CTT)and to calculate a faecal loading score.The patient group underwent treatment with a combined prokinetic regime,after which their CTT and faecal loading were reassessed.Analyses were performed to compare measurements between the control group and the patient group before and after treatment.RESULTS Compared to healthy controls,IBS-patients exhibited a significantly prolonged mean CTT(45.48 h vs 24.75 h,P=0.0002)and significantly greater mean faecal loading scores in all colonic segments(P<0.001).Among IBS patients,we found no significant differences between the 48 h and 96 h radiographs.Among patients exhibiting increased CTT and faecal loading,approximately half exhibited a palpable mass in the right iliac fossa.After intervention with a prokinetic treatment,the mean CTT among IBS patients was reduced from 45.48 h to 34.50 h(P=0.091),with the post-treatment CTT not significantly differing from the CTT among control subjects(P=0.095).The faecal loading score among IBS patients did not significantly differ before and after treatment(P=0.442).The posttreatment faecal loading score in IBS patients remained significantly higher compared to that in controls(5.3 vs 4.3,P=0.014).After treatment,half of the IBSpatients were relieved of bloating,while the majority no longer experienced abdominal pain and achieved a daily consistent stool.CONCLUSION IBS-patients exhibited prolonged CTT and heavier faecal loading.These assessments may aid in diagnosis.Faecal retention may contribute to IBS symptoms,which can be treated using a prokinetic regime.

Diagnostic yield of small bowel capsule endoscopy depends on the small bowel transit time

AIM:To investigate whether the small bowel transit time(SBTT)influences the diagnostic yield of capsule endoscopy(CE).METHODS:Six hundred and ninety-one consecutive CE procedures collected in a database were analyzed.SBTT and CE findings were recorded.A running mean for the SBTT was calculated and correlated to the diagnostic yield with a Spearman's correlation test.Subgroup analyses were performed for the various indications for the procedure.RESULTS:There was a positive correlation between the diagnostic yield and SBTT(Spearman's rho 0.58,P <0.01).Positive correlations between diagnostic yield and SBTT were found for the indication obscure gastrointestinal bleeding(r=0.54,P<0.01),for polyposis and carcinoid combined(r=0.56,P<0.01)and for the other indications(r=0.90,P<0.01),but not for suspected Crohn's disease(r=-0.40).CONCLUSION:The diagnostic yield in small bowel capsule endoscopy is positively correlated with the small bowel transit time.This is true for all indications except for suspected Crohn's disease.

Effect of erythromycin on image quality and transit time of capsule endoscopy: A two-center study

AIM: To compare the effect of oral erythromycin vs no preparation with prokinetics on the transit time and the image quality of capsule endoscopy (CE) in evaluating small bowel (SB) pathology. METHODS: We conducted a retrospective, blinded (to the type of preparation) review of 100 CE studies, 50 with no preparation with prokinetics from one medical center (Group A) and 50 from another center with administration of a single dose of 200 mg oral erythromycin 1 h prior to CE (Group B). Gastric, SB and total transit times were calculated, the presence of bile in the duodenum was scored, as was cleanliness within the proximal, middle and distal intestine. RESULTS: The erythromycin group had a slightly shorter gastric transit time (21 min vs 28 min, with no statistical significance). SB transit time was similar for both groups (all P > 0.05). Total transit time was almost identical in both groups. The rate of incomplete examination was 16% for Group A and 10% for Group B (P = 0.37). Bile and cleanliness scores in different parts of the intestine were similar for the two groups (P > 0.05). CONCLUSION: Preparation for capsule endoscopy with erythromycin does not affect SB or total transit time. It tends to reduce gastric transit time, but it does not increase the cecum-reaching rate. Erythromycin does not adversely affect image quality. We consider the routine use of oral erythromycin preparation as being unjustified, although it might be considered in patients with known prolonged gastric emptying time.

Probiotic supplementation decreases intestinal transit time: Meta-analysis of randomized controlled trials

AIM: To determine the efficacy of probiotic supplementation on intestinal transit time (ITT) and to identify factors that influence these outcomes. METHODS: A systematic review of randomized controlled trials (RCTs) of probiotic supplementation that measured ITT in adults was conducted by searching MEDLINE and EMBASE using relevant combinations. Main search limits included RCTs of probiotic supplementation in healthy or constipated adults that measured ITT. Study quality was assessed using the Jadad scale. A random effects meta-analysis was performed with standardized mean difference (SMD) of ITT between probiotic and control groups as the primary outcome. Meta-regression and subgroup analyses were conducted to examine the impact of moderator variables on ITT SMD. RESULTS: A total of 11 clinical trials with 13 treatment effects representing 464 subjects were included in this analysis. Probiotic supplementation was associated with decreased ITT in relation to controls, with an SMD of 0.40 (95%CI: 0.20-0.59, P < 0.001). Constipation (r 2 = 39%, P = 0.01), higher mean age (r 2 = 27%, P = 0.03), and higher percentage of female subjects (r 2 = 23%, P < 0.05) were predictive of decreased ITT with probiotics in meta-regression. Subgroup analyses demonstrated statistically greater reductions in ITT with probiotics in subjects with vs without constipation and in older vs younger subjects [both SMD: 0.59 (95%CI: 0.39-0.79) vs 0.17 (95%CI: -0.08-0.42), P = 0.01]. Medium to large treatment effects were identified with Bifidobacterium Lactis (B. lactis ) HN019 (SMD: 0.72, 95%CI: 0.27-1.18, P < 0.01) and B. lactis DN-173 010 (SMD: 0.54, 95%CI: 0.15-0.94, P < 0.01) while other single strains and combination products yielded small treatment effects. CONCLUSION: Overall, short-term probiotic supplementation decreases ITT with consistently greater treatment effects identified in constipated or older adults and with certain probiotic strains.

Capsule endoscopy: Improving transit time and image view

AIM: To evaluate the effect of various methods of small bowel preparation on the transit time and the quality of visualization of the entire small bowel mucosa.METHODS: Ninety-five patients underwent capsule endoscopy (CE) by easily swallowing the capsule. They were divided into three study groups according to the preparation used: group A (n = 26) by polyethylene glycol (PEG) liter or with sodium phosphate (SP) 12 h prior to the CE study; group B (n = 29) by erythromycin 1 h prior to the CE study; and group C (n = 40) without any preparation. Visualization ranged from good to satisfactory to poor.RESULTS: The gastric emptying time in the group prepared with erythromycin was shorter but without statistical significance and the small bowel transit time was unaffected. In elderly subjects prepared by PEG or SP, the gastric emptying time was significantly longer (163.7 min, P = 0.05). The transit times of the three sub-groups were not affected by gender or pathology.The grade of cleaning of the entire study group was 3.27±1.1. The erythromycin group presented significantly the worst quality of images (P = 0.05) compared to the other sub-groups. Age, gender, and pathology had no effect on the quality of the cleaning of the small bowel in the sub-groups. One (1.05%) case had no natural excretion.CONCLUSION: Erythromycin markedly reduces gastric emptying time, but has a negative effect on the quality of the image in the small bowel. The preparation of elderly subjects with PEG or SP has a negative effect on the small bowel transit time.

Implications of small-bowel transit time in the detection rate of capsule endoscopy: A multivariable multicenter study of patients with obscure gastrointestinal bleeding

AIM To define the role of small-bowel transit time in the detection rate of significant small-bowel lesions.METHODS Small-bowel capsule endoscopy records, prospectively collected from 30 participating centers in the Lombardy Registry from October 2011 to December 2013, were included in the study if the clinical indication was obscure gastrointestinal bleeding and the capsule reached the cecum. Based on capsule findings, we created two groups: P2(significant findings) and P0-1(normal/negligible findings). Groups were compared for age, gender, small-bowel transit time, type of instrument, modality of capsule performance(outpatients vs inpatients), bowel cleanliness, and center volume.RESULTS We retrieved and scrutinized 1,433 out of 2,295 capsule endoscopy records(62.4%) fulfilling the inclusion criteria. Patients were 67 ± 15 years old, and 815(57%) were males. In comparison with patients in the P0-1 group, those in the P2 group(n = 776, 54%) were older(P < 0.0001), had a longer small-bowel transit time(P = 0.0015), and were more frequently examined in low-volume centers(P < 0.001). Age and smallbowel transit time were correlated(P < 0.001), with age as the sole independent predictor on multivariable analysis. Findings of the P2 group were artero-venous malformations(54.5%), inflammatory(23.6%) and protruding(10.4%) lesions, and luminal blood(11.5%).CONCLUSION In this selected, prospectively collected cohort of small-bowel capsule endoscopy performed for obscure gastrointestinal bleeding, a longer small-bowel transit time was associated with a higher detection rate of significant lesions, along with age and a low center volume, with age serving as an independent predictor.

Colon transit time according to physical activity and characteristics in South Korean adults

AIM:To investigate factors contributing to the colon transit time(CTT),physical activity and characteristics were examined.METHODS:Forty-seven Korean adults(males,n=23;females,n=24) took a capsule containing 20 radioopaque markers to measure the CTT.The subjects used an accelerometer to measure the physical activity and underwent a bioelectrical impedance analysis to determine the physical characteristics.Macro-nutrient was also surveyed.RESULTS:The mean total CTTs(TCTT) in the males and females were 8.8 and 24.7 h(P=0.002),respectively.In the male subjects,the right CTT(3.5±4.9 h vs 10.0±11.6 h,P=0.023) and recto-sigmoid CTT(4.4±4.7 vs 13.6±12.5 h,P=0.004) were significantly shorter and the total energy expenditure(637.6±44.3 kcal vs 464.3±64.9 kcal,P=0.003),total activity count(247 017±75 022 count vs 178 014±75 998 count,P=0.003),energy expenditure of light intensity(148.5±6.9 kcal vs 120.0±16.8 kcal,P=0.006),energy expenditure of moderate intensity(472.0±36.2 kcal vs 281.4±22.2 kcal,P < 0.001),fat intake(65.5±23.3 g vs 51.2±17.4 g,P=0.010),and water consumption(1714.3±329.4 g vs 1164.7±263.6 g,P=0.009) were significantly higher than in the female subjects.Regarding correlations,when adjusted for gender,fiber(r =-0.545,P < 0.001) and water intake(r =-0.257,P < 0.05) correlated significantly with the TCTT in all subjects.In addition,the body mass index(r =-0.424,P < 0.05) and fiber intake(r =-0.417,P < 0.05) in the males as well as the fiber intake(r =-0.655,P < 0.001) in the females showed significant correlations with the TCTT.CONCLUSION:The subjects showed significant gender differences in the TCTT,right CTT,and recto-sigmoid CTT.Furthermore,the intake of the fiber and water contributed to the CTT.

Effects of anatomical position on esophageal transit time:A biomagnetic diagnostic technique

AIM: To study the esophageal transit time (ETT) and compare its mean value among three anatomical inclinations of the body; and to analyze the correlation of ETT to body mass index (BMI). METHODS: A biomagnetic technique was implemented to perform this study: (1) The transit time of a magnetic marker (MM) through the esophagus was measured using two fluxgate sensors placed over the chest of 14 healthy subjects; (2) the ETT was assessed in three anatomical positions (at upright, fowler, and supine positions; 90o, 45o and 0o, respectively). RESULTS: ANOVA and Tuckey post-hoc tests demonstrated significant differences between ETT mean of the different positions. The ETT means were 5.2 ± 1.1 s, 6.1 ± 1.5 s, and 23.6 ± 9.2 s for 90o, 45o and 0o, respectively. Pearson correlation results were r = -0.716 and P < 0.001 by subjects' anatomical position, and r = -0.024 and P > 0.05 according the subject's BMI. CONCLUSION: We demonstrated that using this biomagnetic technique, it is possible to measure the ETT and the effects of the anatomical position on the ETT.

USE OF PULSE TRANSIT TIME AS A MEASURE OF AUTONOMIC AROUSALS IN PATIENTS WITH OBSTRUCTIVE SLEEP APNEA

Objective To evaluate the feasibility of pulse transit time (PTT) arousals as an index of sleep fragmentation in patients with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods Individuals referred for evaluation of possible OSAHS underwent overnight polysomnography (PSG). Three conventional indices of sleep fragmentation [electroencephalography (EEG) arousals, apnea/hypopnea index (AHI), oxygen desaturation index (ODI)], PTT arousals, and Epworth sleepiness scale (ESS) were compared. Results PTT arousals were positively correlated with EEG arousals (r= 0.746, P<0.001), AHI (r= 0.786, P<0.001), and ODI (r= 0.665, P<0.001), respectively. But, both PTT arousals and EEG arousals had no correlation with ESS (r= 0.432, P=0.201; r= 0.196, P=0.591, respectively). Conclusion PTT arousals are correlated well with other standard measures estimating severity of OSAHS and potentially a non-invasive marker with which to measure the sleep fragmentation in patients with OSAHS.

Correcting for non-compliance when determining colonic transit time with radio-opaque markers

The use of radio-opaque markers and abdominal X-ray is the standard method for determining colonic transit time(CTT). However, when there are deviations in the intake of these markers by participants in clinical trials it is desirable to improve observations by introducingcorrections, where possible. To date, there is no standard procedure to adjust for such deviations. This report proposes a series of alternatives based on possible scenarios for deviations from the intended intake of radio-opaque markers. The proposed method to correct for missed or delayed consumption of radioopaque markers can help to increase the accuracy of the CTT measurements in clinical trials.

A method to measure transit time spread of photomultiplier tubes with Cherenkov light

With the technology of coincidence method, transit time spreads (TTSs) of PMTs are measured with Cherenkov light on the photocathode window of photomultiplier tube (PMT) produced by cascade γ radiation source, 60Co. TTSs with single and multi-photoelectron which are analyzed by convolution of Poisson and Gaussian are obtained. The study to XP2020 and XP2020Q PMTs shows that TTSs are consistent with data supplied by Philips. TTSs are inversely proportional to the square roots of number of photoelectrons. The method is feasible when single and multi-photoelectron can be distinguished.

A Probabilistic Method of Characterizing Transit Times for Quantum Particles in Non-Stationary States

We present a probabilistic approach to characterizing the transit time for a quantum particle to flow between two spatially localized states. The time dependence is investigated by initializing the particle in one spatially localized “orbital” and following the time development of the corresponding non-stationary wavefunction of the time-independent Hamiltonian as the particle travels to a second orbital. We show how to calculate the probability that the particle, initially localized in one orbital, has reached a second orbital after a given elapsed time. To do so, discrete evaluations of the time-dependence of orbital occupancy, taken using a fixed time increment, are subjected to conditional probability analysis with the additional restriction of minimum flow rate. This approach yields transit-time probabilities that converge as the time increment used is decreased. The method is demonstrated on cases of two-state oscillations and shown to produce physically realistic results.

Data processing in pulse transit time measurement

PuLse transit time(FIT)is used as a noninvasive and cull-less parameter to estimate blood pressure.In this paper,we develop an algorithm to obtain FTT rapidly,which is appropriate for micro-processor and could achieve good accuracy in PTT,even in noisy measurements.The algorithm is based on finite impulse response(FIR)filter to reduce the noise and an adaptive threshold to detect the significant points of ECG and PPG.Evaluation of this method is based on the signals from our PTr-based blood pressure devices.It is shown that the method works well for PPT calculation.

Data processing in pulse transit time measurement

Pulse transit time (PTT) is used as a noninvasive and cuff-less parameter to estimate blood pressure. In this paper, we develop an algorithm to obtain PTT rapidly, which is appropriate for micro-processor and could achieve good accuracy in PTT, even in noisy measurements. The algorithm is based on finite impulse response (FIR) filter to reduce the noise and an adaptive threshold to detect the significant points of ECG and PPG. Evaluation of this method is based on the signals from our PTT-based blood pressure devices. It is shown that the method works well for PPT calculation.

Transit time difference and equal or non-equal transit time theory for airfoils with lift

The transit time difference of fluid particles moving along the upper and lower surfaces of a lift-producing airfoil is studied here both theoretically and numerically.We show that,under thin airfoil assumption and for potential flow,the transit time difference is equal to the circulation divided by the square of the inflow velocity and the lift coefficient is equal to half of the number of chords travelled by the airfoil during the transit time difference.An analysis of transit time difference for very thick airfoil(c.f.very large angle of attack)suggests the transit time may change sign beyond thin airfoil assumption,a conclusion supported by an example of flow with an attached vortex.Thus,fluid particles may transit the upper surface with less,equal and more time than those transiting the lower surface for lift producing airfoils,depending on the configuration of flow structure and geometry.