Journal articles: 'Cerebral transit time'

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Liebetrau, Martin, Jürgen Herzog, Christian U. A. Kloss, Gerhard F. Hamann, and Martin Dichgans. "Prolonged Cerebral Transit Time in CADASIL." Stroke 33, no. 2 (February 2002): 509–12. http://dx.doi.org/10.1161/hs0202.102949.

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Kamano, Hironori, Takashi Yoshiura, Akio Hiwatashi, Koichiro Abe, Osamu Togao, Koji Yamashita, and Hiroshi Honda. "Arterial spin labeling in patients with chronic cerebral artery steno-occlusive disease: Correlation with 15O-PET." Acta Radiologica 54, no. 1 (February 2013): 99–106. http://dx.doi.org/10.1258/ar.2012.120450.

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Background Heterogeneity of arterial transit time due to cerebral artery steno-occlusive lesions hampers accurate regional cerebral blood flow measurement by arterial spin labeling (ASL). Purpose To assess the feasibility of regional cerebral blood flow measurement by ASL with multiple-delay time sampling in patients with steno-occlusive diseases by comparing with positron emission tomography (PET), and to determine whether regional arterial transit time measured by this ASL technique is correlated with regional mean transit time, a PET index of perfusion pressure. Material and Methods Sixteen patients with steno-occlusive diseases received both ASL and 15O-PET. The mean regional cerebral blood flow measured by ASL and PET, regional arterial transit time by ASL, and regional mean transit time by PET were obtained by a region-of-interest analysis. Correlation between regional cerebral blood flow by ASL and that by PET, and correlation between regional arterial transit time by ASL and regional mean transit time by PET were tested using Pearson's correlation coefficient for both absolute and relative values. A multivariate regression analysis was performed to test whether regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling the effect of regional cerebral blood flow by ASL. Results A significant positive correlation was found between regional cerebral blood flow by ASL and that by PET for both absolute (r = 0.520, P < 0.0001) and relative (r = 0.691, P < 0.0001) values. A significant positive correlation was found between regional arterial transit time by ASL and regional mean transit time by PET both for absolute (r = 0.369, P = 0.0002) and relative (r = 0.443, P < 0.0001) values. The regression analysis revealed that regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling regional cerebral blood flow by ASL (P = 0.0011). Conclusion The feasibility of regional cerebral blood flow measurement using ASL with multiple-delay time sampling was confirmed in patients with cerebral artery steno-occlusive diseases. Moreover, it was suggested that mapping of regional arterial transit time has the potential to detect hemodynamic impairment.

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Engedal, Thorbjørn S., Niels Hjort, Kristina D. Hougaard, Claus Z. Simonsen, Grethe Andersen, Irene Klærke Mikkelsen, Jens K. Boldsen, et al. "Transit time homogenization in ischemic stroke – A novel biomarker of penumbral microvascular failure?" Journal of Cerebral Blood Flow & Metabolism 38, no. 11 (July 31, 2017): 2006–20. http://dx.doi.org/10.1177/0271678x17721666.

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Cerebral ischemia causes widespread capillary no-flow in animal studies. The extent of microvascular impairment in human stroke, however, is unclear. We examined how acute intra-voxel transit time characteristics and subsequent recanalization affect tissue outcome on follow-up MRI in a historic cohort of 126 acute ischemic stroke patients. Based on perfusion-weighted MRI data, we characterized voxel-wise transit times in terms of their mean transit time (MTT), standard deviation (capillary transit time heterogeneity – CTH), and the CTH:MTT ratio (relative transit time heterogeneity), which is expected to remain constant during changes in perfusion pressure in a microvasculature consisting of passive, compliant vessels. To aid data interpretation, we also developed a computational model that relates graded microvascular failure to changes in these parameters. In perfusion–diffusion mismatch tissue, prolonged mean transit time (>5 seconds) and very low cerebral blood flow (≤6 mL/100 mL/min) was associated with high risk of infarction, largely independent of recanalization status. In the remaining mismatch region, low relative transit time heterogeneity predicted subsequent infarction if recanalization was not achieved. Our model suggested that transit time homogenization represents capillary no-flow. Consistent with this notion, low relative transit time heterogeneity values were associated with lower cerebral blood volume. We speculate that low RTH may represent a novel biomarker of penumbral microvascular failure.

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Arsava, Ethem M., Mikkel B. Hansen, Berkan Kaplan, Ahmet Peker, Rahsan Gocmen, Anil Arat, Kader K. Oguz, Mehmet A. Topcuoglu, Leif Østergaard, and Turgay Dalkara. "The effect of carotid artery stenting on capillary transit time heterogeneity in patients with carotid artery stenosis." European Stroke Journal 3, no. 3 (April 26, 2018): 263–71. http://dx.doi.org/10.1177/2396987318772686.

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Introduction Carotid revascularisation improves haemodynamic compromise in cerebral circulation as an additional benefit to the primary goal of reducing future thromboembolic risk. We determined the effect of carotid artery stenting on cerebral perfusion and oxygenation using a perfusion-weighted MRI algorithm that is based on assessment of capillary transit-time heterogeneity together with other perfusion and metabolism-related metrics. Patients and methods A consecutive series of 33 patients were evaluated by dynamic susceptibility contrast perfusion-weighted MRI prior to and within 24 h of the endovascular procedure. The level of relative change induced by stenting, and relationship of these changes with respect to baseline stenosis degree were analysed. Results Stenting led to significant increase in cerebral blood flow ( p < 0.001), and decrease in cerebral blood volume ( p = 0.001) and mean transit time ( p < 0.001); this was accompanied by reduction in oxygen extraction fraction ( p < 0.001) and capillary transit-time heterogeneity ( p < 0.001), but an overall increase in relative capillary transit-time heterogeneity (RTH: CTH divided by MTT; p = 0.008). No significant change was observed with respect to cerebral metabolic rate of oxygen. The median volume of tissue with MTT > 2s decreased from 24 ml to 12 ml ( p = 0.009), with CTH > 2s from 29 ml to 19 ml ( p = 0.041), and with RTH < 0.9 from 61 ml to 39 ml ( p = 0.037) following stenting. These changes were correlated with the baseline degree of stenosis. Discussion: Stenting improved the moderate stage of haemodynamic compromise at baseline in our cohort. The decreased relative transit-time heterogeneity, which increases following stenting, is probably a reflection of decreased functional capillary density secondary to chronic hypoperfusion induced by the proximal stenosis. Conclusion: Carotid artery stenting, is not only important for prophylaxis of future vascular events, but also is critical for restoration of microvascular function in the cerebral tissue.

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Lo, E. H., J. Rogowska, P. Bogorodzki, M. Trocha, K. Matsumoto, B. Saffran, and G. L. Wolf. "Temporal Correlation Analysis of Penumbral Dynamics in Focal Cerebral Ischemia." Journal of Cerebral Blood Flow & Metabolism 16, no. 1 (January 1996): 60–68. http://dx.doi.org/10.1097/00004647-199601000-00007.

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A novel temporal correlation technique was used to map the first-pass transit of iodinated contrast agents through the brain. Transit profiles after bolus injections were measured with dynamic computed tomography (CT) scanning (1 image/s over 50 s). A rabbit model of focal cerebral ischemia (n = 6) was used, and dynamic CT scans were performed at 30, 60, 90, and 120 min postocclusion. Within the ischemic core, no bolus transit was detectable, demonstrating that complete ischemia was present after arterial occlusion. In the periphery of the ischemic distribution, transit dynamics showed smaller peaks, broadened profiles, and overall delay in bolus transit. A cross-correlation method was used to generate maps of delays in ischemic transit profiles compared with normal transit profiles from the contralateral hemisphere. These maps showed that penumbral regions surrounding the ischemic core had significantly delayed bolus transit profiles. Enlargement of the ischemic core over time (from 30 to 120 min postocclusion) was primarily accomplished by the progressive deterioration of the penumbral regions. These results suggest that (a) temporal correlation methods can define regions of abnormal perfusion in focal cerebral ischemia, (b) peripheral regions of focal cerebral ischemia are characterized by delays in bolus transit profiles, and (c) these regions of bolus transit delay deteriorate over time and thus represent a hemodynamic penumbra.

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Bush, Adam M., Roberta Miyeko Kato, Thomas D. Coates, and John C. Wood. "Cerebral Tissue Transit Time in Patients with Sickle Cell Anemia." Blood 126, no. 23 (December 3, 2015): 280. http://dx.doi.org/10.1182/blood.v126.23.280.280.

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Abstract Introduction Accurate characterization of cerebral blood flow (CBF) in patients with sickle cell anemia (SCA) is imperative given the occurrence of neurovascular sequelae in this population. Arterial Spin Labeling (ASL) is a promising MRI modality that has been used to quantify CBF in SCA by several groups. Unfortunately, ASL quantification has proven challenging in SCA given the unique phenotype found in these patients including decreased hematocrit, elevated blood velocity an abnormal rheologic properties. As a result, there are conflicting accounts of ASL perfusion in this population. One of the key parameters of ASL quantification is the time between the labeling of spins in the neck and the downstream diffusion of those spins into parenchymal tissue, termed tissue transit time (TT). Delayed tissue TT is a known consequence of many neurovascular pathologies, including stroke. Given the elevated cerebral blood velocity and flow in response to anemia, however it is generally assumed that tissue TT is shorter in SCA but has yet to be studied. In order to improve ASL quantification and characterize this neurovascular biomarker we measured ASL derived tissue TT in healthy patients with SCA and ethnicity matched controls. Methods All patients were recruited with informed consent or assent and this study was approved by the Children's Hospital Los Angeles institutional review board. Exclusion criteria included pregnancy, previous stroke, acute chest, pain crisis or hospitalization within one month. All MRI scans were performed on an Achieva 3T scanner with an 8 channel head coil. Tissue TT was measured using two single shot, GRASE, ASL acquisitions, one with velocity spoiling gradients (venc 5 cm/s) and one without. Pseudo continuous ASL had a label duration of 1150ms and delay of 1500ms. Single slice phase contrast MRI of the carotids and vertebral arteries measured arterial blood velocity and global CBF. Hemoglobin level was determined on the day of the study. Results Eight patients with SCA (7 SS, 1 SC; 15.8 + 4.4yo; 5F, 3M) and nine ethnicity matched healthy controls (36.4 + 4.1yo; 6 F, 3M) were recruited. Patients with SCA had a lower hemoglobin levels (SCA, 10.1 + 0.64 g/dl, CTRL 13.7 + 0.58) and elevated CBF (SCA, 76.6 + 5.8 ml/100g/min, CTRL 49.0 + 4.4 ml/100g/min). Regional ASL perfusion asymmetries were observed in several SCA subjects. These asymmetries were not present in corresponding tissue TT maps (Figure 1). There was a trending difference in tissue TT between the two groups (SCA 1588 + 49.8, CTRL 1696 + 46.9 ms, p=.1). After multivariate analysis, sex and global CBF were the only predictors of tissue TT, r2=.54 (Figure 2). Discussion Our data is the first of our knowledge to measure the tissue TT in patients with SCA. Tissue TT is distinct from the bolus arrival time or arterial TT which corresponds to the arrival time of tracer at the imaging region. Tissue transit time is more sensitive to microvascular flow and diffusion effects and may reflect microvascular health and blood brain barrier integrity. Our measurement of tissue TT is congruent with other findings in separate neurovascular pathologies and suggests that gender and global CBF must be considered when quantifying ASL perfusion. These preliminary results also offer insight into the perfusion asymmetries observed in the ASL SCA literature. We found that perfusion asymmetries do not correlate with tissue TT suggesting either 1) tissue TT is conserved despite differences in regional flow or 2) a separate source of error is leading to spurious regional perfusion quantification, ie labeling efficiency. Figure 1. Relative perfusion map (top) vs transit time map (bottom) in a healthy control (left) and patient with SCA (right). Posterior region in healthy control demonstrates longer transit time. Right left perfusion asymmetry in SCA patient is not observed in corresponding transit map. Univariate analysis of sex vs tissue TT (left). Males demonstrate shorter transit time than females. After correcting for gender there is an observed inverse flow effect where larger CBF corresponds to shortened tissue TT (right). Figure 1. Relative perfusion map (top) vs transit time map (bottom) in a healthy control (left) and patient with SCA (right). Posterior region in healthy control demonstrates longer transit time. Right left perfusion asymmetry in SCA patient is not observed in corresponding transit map. / Univariate analysis of sex vs tissue TT (left). Males demonstrate shorter transit time than females. After correcting for gender there is an observed inverse flow effect where larger CBF corresponds to shortened tissue TT (right). Disclosures No relevant conflicts of interest to declare.

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Koch, Klaus Ulrik, Anna Tietze, Joel Aanerud, Gorm von Öettingen, Niels Juul, Jens Christian Hedemann Sørensen, Lone Nikolajsen, Leif Østergaard, and Mads Rasmussen. "Effect of ephedrine and phenylephrine on brain oxygenation and microcirculation in anaesthetised patients with cerebral tumours: study protocol for a randomised controlled trial." BMJ Open 7, no. 11 (November 2017): e018560. http://dx.doi.org/10.1136/bmjopen-2017-018560.

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IntroductionDuring brain tumour surgery, vasopressor drugs are commonly administered to increase mean arterial blood pressure with the aim of maintaining sufficient cerebral perfusion pressure. Studies of the commonly used vasopressors show that brain oxygen saturation is reduced after phenylephrine administration, but unaltered by ephedrine administration. These findings may be explained by different effects of phenylephrine and ephedrine on the cerebral microcirculation, in particular the capillary transit-time heterogeneity, which determines oxygen extraction efficacy. We hypothesised that phenylephrine is associated with an increase in capillary transit-time heterogeneity and a reduction in cerebral metabolic rate of oxygen compared with ephedrine. Using MRI and positron emission tomography (PET) as measurements in anaesthetised patients with brain tumours, this study will examine whether phenylephrine administration elevates capillary transit-time heterogeneity more than ephedrine, thereby reducing brain oxygenation.Methods and analysisThis is a double-blind, randomised clinical trial including 48 patients scheduled for surgical brain tumour removal. Prior to imaging and surgery, anaesthetised patients will be randomised to receive either phenylephrine or ephedrine infusion until mean arterial blood pressure increases to above 60 mm Hg or 20% above baseline. Twenty-four patients were allocated to MRI and another 24 patients to PET examination. MRI measurements include cerebral blood flow, capillary transit-time heterogeneity, cerebral blood volume, blood mean transit time, and calculated oxygen extraction fraction and cerebral metabolic rate of oxygen for negligible tissue oxygen extraction. PET measurements include cerebral metabolic rate of oxygen, cerebral blood flow and oxygen extraction fraction. Surgery is initiated after MRI/PET measurements and subdural intracranial pressure is measured.Ethics and disseminationThis study was approved by the Central Denmark Region Committee on Health Research Ethics (12 June 2015; 1-10-72-116-15). Results will be disseminated via peer-reviewed publication and presentation at international conferences.Trial registration numberNCT02713087; Pre-results. 2015-001359-60; Pre-results.

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Alsop, D. C., and J. A. Detre. "Reduced Transit-Time Sensitivity in Noninvasive Magnetic Resonance Imaging of Human Cerebral Blood Flow." Journal of Cerebral Blood Flow & Metabolism 16, no. 6 (November 1996): 1236–49. http://dx.doi.org/10.1097/00004647-199611000-00019.

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Herein, we present a theoretical framework and experimental methods to more accurately account for transit effects in quantitative human perfusion imaging using endogenous magnetic resonance imaging (MRI) contrast. The theoretical transit time sensitivities of both continuous and pulsed inversion spin tagging experiments are demonstrated. We propose introducing a delay following continuous labeling, and demonstrate theoretically that introduction of a delay dramatically reduces the transit time sensitivity of perfusion imaging. The effects of magnetization transfer saturation on this modified continuous labeling experiment are also derived, and the assumption that the perfusion signal resides entirely within tissue rather than the arterial microvasculature is examined. We present results demonstrating the implementation of the continuous tagging experiment with delay on an echoplanar scanner for measuring cerebral blood flow (CBF) in normal volunteers. By varying the delay, we estimate transit times in the arterial system, values that are necessary for assessing the accuracy of our quantification. The effect of uncertainties in the transit time from the tagging plane to the arterial microvasculature and the transit time to the tissue itself on the accuracy of perfusion quantification is discussed and found to be small in gray matter but still potentially significant in white matter. A novel method for measuring T1, which is fast, insensitive to contamination by cerebrospinal fluid, and compatible with the application of magnetization transfer saturation, is also presented. The methods are combined to produce quantitative maps of resting and hypercarbic CBF.

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Kamp, Marcel A., Philipp Slotty, Bernd Turowski, Nima Etminan, Hans-Jakob Steiger, Daniel Hänggi, and Walter Stummer. "Microscope-Integrated Quantitative Analysis of Intraoperative Indocyanine Green Fluorescence Angiography for Blood Flow Assessment: First Experience in 30 Patients." Operative Neurosurgery 70, suppl_1 (August 1, 2011): ons65—ons74. http://dx.doi.org/10.1227/neu.0b013e31822f7d7c.

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Abstract BACKGROUND: Intraoperative measurements of cerebral blood flow are of interest during vascular neurosurgery. Near-infrared indocyanine green (ICG) fluorescence angiography was introduced for visualizing vessel patency intraoperatively. However, quantitative information has not been available. OBJECTIVE: To report our experience with a microscope with an integrated dynamic ICG fluorescence analysis system supplying semiquantitative information on blood flow. METHODS: We recorded ICG fluorescence curves of cortex and cerebral vessels using software integrated into the surgical microscope (Flow 800 software; Zeiss Pentero) in 30 patients undergoing surgery for different pathologies. The following hemodynamic parameters were assessed: maximum intensity, rise time, time to peak, time to half-maximal fluorescence, cerebral blood flow index, and transit times from arteries to cortex. RESULTS: For patients without obvious perfusion deficit, maximum fluorescence intensity was 177.7 arbitrary intensity units (AIs; 5-mg ICG bolus), mean rise time was 5.2 seconds (range, 2.9-8.2 seconds; SD, 1.3 seconds), mean time to peak was 9.4 seconds (range, 4.9-15.2 seconds; SD, 2.5 seconds), mean cerebral blood flow index was 38.6 AI/s (range, 13.5-180.6 AI/s; SD, 36.9 seconds), and mean transit time was 1.5 seconds (range, 360 milliseconds-3 seconds; SD, 0.73 seconds). For 3 patients with impaired cerebral perfusion, time to peak, rise time, and transit time between arteries and cortex were markedly prolonged (>20, >9 , and >5 seconds). In single patients, the degree of perfusion impairment could be quantified by the cerebral blood flow index ratios between normal and ischemic tissue. Transit times also reflected blood flow perturbations in arteriovenous fistulas. CONCLUSION: Quantification of ICG-based fluorescence angiography appears to be useful for intraoperative monitoring of arterial patency and regional cerebral blood flow.

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Elting, Jan Willem J., Jeanette Tas, Marcel JH Aries, Marek Czosnyka, and Natasha M. Maurits. "Dynamic cerebral autoregulation estimates derived from near infrared spectroscopy and transcranial Doppler are similar after correction for transit time and blood flow and blood volume oscillations." Journal of Cerebral Blood Flow & Metabolism 40, no. 1 (October 24, 2018): 135–49. http://dx.doi.org/10.1177/0271678x18806107.

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We analysed mean arterial blood pressure, cerebral blood flow velocity, oxygenated haemoglobin and deoxygenated haemoglobin signals to estimate dynamic cerebral autoregulation. We compared macrovascular (mean arterial blood pressure-cerebral blood flow velocity) and microvascular (oxygenated haemoglobin-deoxygenated haemoglobin) dynamic cerebral autoregulation estimates during three different conditions: rest, mild hypocapnia and hypercapnia. Microvascular dynamic cerebral autoregulation estimates were created by introducing the constant time lag plus constant phase shift model, which enables correction for transit time, blood flow and blood volume oscillations (TT-BF/BV correction). After TT-BF/BV correction, a significant agreement between mean arterial blood pressure-cerebral blood flow velocity and oxygenated haemoglobin-deoxygenated haemoglobin phase differences in the low frequency band was found during rest (left: intraclass correlation=0.6, median phase difference 29.5° vs. 30.7°, right: intraclass correlation=0.56, median phase difference 32.6° vs. 39.8°) and mild hypocapnia (left: intraclass correlation=0.73, median phase difference 48.6° vs. 43.3°, right: intraclass correlation=0.70, median phase difference 52.1° vs. 61.8°). During hypercapnia, the mean transit time decreased and blood volume oscillations became much more prominent, except for very low frequencies. The transit time related to blood flow oscillations was remarkably stable during all conditions. We conclude that non-invasive microvascular dynamic cerebral autoregulation estimates are similar to macrovascular dynamic cerebral autoregulation estimates, after TT-BF/BV correction is applied. These findings may increase the feasibility of non-invasive continuous autoregulation monitoring and guided therapy in clinical situations.

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Hunter, R., M. V. Merrick, C. Ferrington, A. Notghi, R. McLuskie, J. E. Christie, and G. M. Goodwin. "Cerebral Vascular Transit Time in Alzheimer's Disease and Korsakoff's Psychosis and its Relation to Cognitive Function." British Journal of Psychiatry 154, no. 6 (June 1989): 790–96. http://dx.doi.org/10.1192/bjp.154.6.790.

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The cerebral vascular transit time of 17 patients with presenile dementia of the Alzheimer type (ATD), nine abstinent patients with alcoholic Korsakoff's psychosis (KOR), and ten age-matched controls was determined by the bolus intravenous injection of pertechnetate. A gamma camera was used to estimate the median transit time (MTT) of the radioactive bolus in a planar (non-tomographic) projection normal to the vertex. The spread of the bolus arriving at the aortic arch was measured independently by a single external detector over the chest, and correction made for the transit time of this input function in calculating the net MTT for the head. Both ATD and KOR groups showed lengthened net MTTs, compatible with reduced cerebral blood flow, and which were correlated with reduced cognitive function. It is concluded that the method employed gives a simple, inexpensive estimate of function-related blood flow to the brain in presenile dementia.

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Ferrari, M., D. A. Wilson, D. F. Hanley, and R. J. Traystman. "Effects of graded hypotension on cerebral blood flow, blood volume, and mean transit time in dogs." American Journal of Physiology-Heart and Circulatory Physiology 262, no. 6 (June 1, 1992): H1908—H1914. http://dx.doi.org/10.1152/ajpheart.1992.262.6.h1908.

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This study tested the hypothesis that cerebral blood flow (CBF) is maintained by vasodilation, which manifests itself as a progressive increase in mean transit time (MTT) and cerebral blood volume (CBV) when cerebral perfusion pressure is reduced. Cerebral perfusion pressure was decreased in 10 pentobarbital-anesthetized dogs by controlled hemorrhage. Microsphere-determined CBF was autoregulated in all tested cerebral regions over the 40- to 130-mmHg cerebral perfusion pressure range but decreased by 50% at approximately 30 mmHg. MTT and CBV progressively and proportionately increased in the right parietal cerebral cortex over the 40- to 130-mmHg cerebral perfusion pressure range. Total hemoglobin content (Hb1), measured in the same area by an optical method, increased in parallel with the increases in CBV computed as the (CBF.MTT) product. At 30 mmHg cerebral perfusion pressure, CBV and Hb were still increased and MTT was disproportionately lengthened (690% of control). We conclude that within the autoregulatory range, CBF constancy is maintained by both increased CBV and MTT. Outside the autoregulatory range, substantial prolongation of the MTT occurs. When CBV is maximal, further reductions in cerebral perfusion pressure produce disproportionate increases in MTT that signal the loss of cerebral vascular dilatory hemodynamic reserve.

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Menon, Bijoy K., Helin Daniel Bai, Jayesh Modi, Andrew M. Demchuk, Mark Hudon, Mayank Goyal, and Timothy W. J. Watson. "The ICV Sign as a Marker of Increased Cerebral Blood Transit Time." Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 40, no. 2 (March 2013): 187–91. http://dx.doi.org/10.1017/s0317167100013718.

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Objective/Background:We describe the internal cerebral vein (ICV) sign, which is a hypo-opacification of the ICV on computed tomogram angiography (CTA) as a new marker of increased cerebral blood transit-time in ipsilateral internal carotid artery occlusions (ICAO).Methods:A retrospective analysis of 153 patients with acute unilateral M1 middle cerebral artery (MCA) occlusions ± ICAOs was performed. The degree of contrast opacification of the ICV on the ipsilesional side was compared to that of the unaffected side.Results:Of 153 patients in our study, 135 had M1 MCA occlusions ± intra-cranial ICAO (M1±iICAO) and 18 had isolated extracranial ICAO (eICAO). In the patients with proximal M1±iICAO, 57/65 (87.1%) showed the ICV sign. Of the 8 patients without the ICV sign in this group, 6 had prominent lenticulostriate arteries arising from the non-occluded M1 segment, 1 had a recurrent artery of Huebner, and 1 had filling of distal ICA/M1 segment through prominent Circle of Willis collaterals. For the 70 patients with isolated distal M1±iICAO, 7/70 (10%) showed the ICV sign, with all 7 showing occluded lenticulostriate arteries. Of the patients with eICAO, 8/18 showed the ICV sign, all 8 with the ICV sign had poor Circle of Willis collaterals.Conclusions:The ICV sign correlates well with presence of proximal M1±iICAO in patients with either occluded lenticulostriate arteries or poor Circle of Willis collaterals. In patients with eICAO, the sign correlates with reduced Circle of Willis collaterals and may be a marker of increased ipsilateral cerebral blood transit time.

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Muer, Jessica D., Aaron T. Ward, Katrina J. Carter, J. Mikhail Kellawan, John W. Harrell, Alejandro Roldan, Oliver Wieben, Marlowe W. Eldridge, and William G. Schrage. "Does insulin resistance alter pulse transit time in the cerebral circulation?" FASEB Journal 34, S1 (April 2020): 1. http://dx.doi.org/10.1096/fasebj.2020.34.s1.05993.

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Park, Eun Sook, Chang Il Park, Sung-Rae Cho, Sang-il Na, and Youn Soo Cho. "Colonic transit time and constipation in children with spastic cerebral palsy." Archives of Physical Medicine and Rehabilitation 85, no. 3 (March 2004): 453–56. http://dx.doi.org/10.1016/s0003-9993(03)00479-9.

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Ibaraki, Masanobu, Hiroshi Ito, Eku Shimosegawa, Hideto Toyoshima, Keiichi Ishigame, Kazuhiro Takahashi, Syuichi Miura, and Iwao Kanno. "Cerebral vascular mean transit time determined by PET and DSC-MRI." Journal of Cerebral Blood Flow & Metabolism 25, no. 1_suppl (August 2005): S676. http://dx.doi.org/10.1038/sj.jcbfm.9591524.0676.

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Kuroki, Soemu. "Relations of brain mean transit time, hematocrit and cerebral blood flow in chronic cerebral infarcts." Nosotchu 11, no. 3 (1989): 223–29. http://dx.doi.org/10.3995/jstroke.11.223.

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Puls, Imke, Georg Becker, Mathias Mäurer, and Wolfgang Müllges. "Cerebral arteriovenous transit time (cTT): a sonographic assessment of cerebral microcirculation using ultrasound contrast agents." Ultrasound in Medicine & Biology 25, no. 4 (May 1999): 503–7. http://dx.doi.org/10.1016/s0301-5629(99)00002-2.

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Angleys, Hugo, Leif Østergaard, and Sune N. Jespersen. "The Effects of Capillary Transit Time Heterogeneity (CTH) on Brain Oxygenation." Journal of Cerebral Blood Flow & Metabolism 35, no. 5 (February 11, 2015): 806–17. http://dx.doi.org/10.1038/jcbfm.2014.254.

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We recently extended the classic flow–diffusion equation, which relates blood flow to tissue oxygenation, to take capillary transit time heterogeneity ( CTH) into account. Realizing that cerebral oxygen availability depends on both cerebral blood flow ( CBF) and capillary flow patterns, we have speculated that CTH may be actively regulated and that changes in the capillary morphology and function, as well as in blood rheology, may be involved in the pathogenesis of conditions such as dementia and ischemia-reperfusion injury. The first extended flow–diffusion equation involved simplifying assumptions which may not hold in tissue. Here, we explicitly incorporate the effects of oxygen metabolism on tissue oxygen tension and extraction efficacy, and assess the extent to which the type of capillary transit time distribution affects the overall effects of CTH on flow–metabolism coupling reported earlier. After incorporating tissue oxygen metabolism, our model predicts changes in oxygen consumption and tissue oxygen tension during functional activation in accordance with literature reports. We find that, for large CTH values, a blood flow increase fails to cause significant improvements in oxygen delivery, and can even decrease it; a condition of malignant CTH. These results are found to be largely insensitive to the choice of the transit time distribution.

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Ibaraki, Masanobu, Kazuhiro Nakamura, Hideto Toyoshima, Kazuhiro Takahashi, Keisuke Matsubara, Atsushi Umetsu, Josef Pfeuffer, Hideto Kuribayashi, and Toshibumi Kinoshita. "Spatial coefficient of variation in pseudo-continuous arterial spin labeling cerebral blood flow images as a hemodynamic measure for cerebrovascular steno-occlusive disease: A comparative 15O positron emission tomography study." Journal of Cerebral Blood Flow & Metabolism 39, no. 1 (June 5, 2018): 173–81. http://dx.doi.org/10.1177/0271678x18781667.

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Pseudo-continuous arterial spin labeling (pCASL) is a completely non-invasive method of cerebral perfusion measurement. However, cerebral blood flow (CBF) quantification is hampered by arterial transit artifacts characterized by bright vascular signals surrounded by decreased signals in tissue regions, which commonly appear in patients with reduced cerebral perfusion pressure. The spatial coefficient of variation (CoV) of pCASL CBF images has been proposed as an alternative region-of-interest (ROI)-based hemodynamic measure to predict prolonged arterial transit time (ATT). This retrospective study investigates the utility of spatial CoV by comparison with 15O positron emission tomography (PET). For patients with cerebrovascular steno-occlusive disease ( n = 17), spatial CoV was positively correlated with ATT independently measured by pulsed arterial spin labeling ( r = 0.597, p < 0.001), confirming its role as an ATT-like hemodynamic measure. Comparisons with 15O PET demonstrated that spatial CoV was positively correlated with vascular mean transit time ( r = 0.587, p < 0.001) and negatively correlated with both resting CBF ( r = −0.541, p = 0.001) and CBF response to hypercapnia ( r = −0.373, p = 0.030). ROI-based spatial CoV calculated from single time-point pCASL can potentially detect subtle perfusion abnormalities in clinical settings.

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Lear, James L., Ravindra Kasliwal, and Angela Feyerabend. "Mapping regional cerebral vascular transit time by simultaneous determination of local cerebral blood flow and local cerebral blood volume." Metabolic Brain Disease 5, no. 3 (September 1990): 155–65. http://dx.doi.org/10.1007/bf00999842.

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Shakur, Sophia F., Denise Brunozzi, Ahmed E. Hussein, Andreas Linninger, Chih-Yang Hsu, Fady T. Charbel, and Ali Alaraj. "Validation of cerebral arteriovenous malformation hemodynamics assessed by DSA using quantitative magnetic resonance angiography: preliminary study." Journal of NeuroInterventional Surgery 10, no. 2 (February 24, 2017): 156–61. http://dx.doi.org/10.1136/neurintsurg-2017-012991.

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BackgroundThe hemodynamic evaluation of cerebral arteriovenous malformations (AVMs) using DSA has not been validated against true flow measurements.ObjectiveTo validate AVM hemodynamics assessed by DSA using quantitative magnetic resonance angiography (QMRA).Materials and methodsPatients seen at our institution between 2007 and 2016 with a supratentorial AVM and DSA and QMRA obtained before any treatment were retrospectively reviewed. DSA assessment of AVM flow comprised AVM arterial-to-venous time (A-Vt) and iFlow transit time. A-Vt was defined as the difference between peak contrast intensity in the cavernous internal carotid artery and peak contrast intensity in the draining vein. iFlow transit times were determined using syngo iFlow software. A-Vt and iFlow transit times were correlated with total AVM flow measured using QMRA and AVM angioarchitectural and clinical features.Results33 patients (mean age 33 years) were included. Nine patients presented with hemorrhage. Mean AVM volume was 9.8 mL (range 0.3–57.7 mL). Both A-Vt (r=−0.47, p=0.01) and iFlow (r=−0.44, p=0.01) correlated significantly with total AVM flow. iFlow transit time was significantly shorter in patients who presented with seizure but A-Vt and iFlow did not vary with other AVM angioarchitectural features such as venous stenosis or hemorrhagic presentation.ConclusionsA-Vt and iFlow transit times on DSA correlate with cerebral AVM flow measured using QMRA. Thus, these parameters may be used to indirectly estimate AVM flow before and after embolization during angiography in real time.

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Crumrine, R. Christian, and Joseph C. LaManna. "Regional Cerebral Metabolites, Blood Flow, Plasma Volume, and Mean Transit Time in Total Cerebral Ischemia in the Rat." Journal of Cerebral Blood Flow & Metabolism 11, no. 2 (March 1991): 272–82. http://dx.doi.org/10.1038/jcbfm.1991.59.

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Cerebral high-energy metabolites and metabolic end products were measured during and following total cerebral ischemia in the rat. During cerebral ischemia, lactate accumulation was greatest in the hippocampus, followed by the cerebral cortex and striatum. Following reperfusion, the rate of lactate clearance was slower in the hippocampus than in the other two regions. Regional CBF, cerebral plasma volume (CPV), and calculated mean transit time (MTT) were determined following refow of ischemic tissue. During hyperemia, CPV, used as an indicator of capillary volume, increased concomitantly with CBF while the MTT remained near the control value, suggesting that the linear flow rate through the vasculature was unchanged. During hypoperfusion, CPV returned to control values, but there was a signif-cant increase in MTT that would result from a decreased linear velocity. The finding of normal tissue energy charge, pHi, and concentration of other metabolites during hypoperfusion shows that hypoperfusion does not result in CBF-metabolic mismatch.

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Ruprecht-Drfler, Petra, Dirk Brechtelsbauer, Mira Schließer, Imke Puls, and Georg Becker. "Prognostic and diagnostic value of global cerebral blood flow volume and cerebral transit time in acute stroke." Ultrasound in Medicine & Biology 28, no. 11-12 (November 2002): 1405–11. http://dx.doi.org/10.1016/s0301-5629(02)00649-x.

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Østergaard, Leif, Thorbjørn S. Engedal, Rasmus Aamand, Ronni Mikkelsen, Nina K. Iversen, Maryam Anzabi, Erhard T. Næss-Schmidt, et al. "Capillary Transit Time Heterogeneity and Flow-Metabolism Coupling after Traumatic Brain Injury." Journal of Cerebral Blood Flow & Metabolism 34, no. 10 (July 23, 2014): 1585–98. http://dx.doi.org/10.1038/jcbfm.2014.131.

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Most patients who die after traumatic brain injury (TBI) show evidence of ischemic brain damage. Nevertheless, it has proven difficult to demonstrate cerebral ischemia in TBI patients. After TBI, both global and localized changes in cerebral blood flow (CBF) are observed, depending on the extent of diffuse brain swelling and the size and location of contusions and hematoma. These changes vary considerably over time, with most TBI patients showing reduced CBF during the first 12hours after injury, then hyperperfusion, and in some patients vasospasms before CBF eventually normalizes. This apparent neurovascular uncoupling has been ascribed to mitochondrial dysfunction, hindered oxygen diffusion into tissue, or microthrombosis. Capillary compression by astrocytic endfeet swelling is observed in biopsies acquired from TBI patients. In animal models, elevated intracranial pressure compresses capillaries, causing redistribution of capillary flows into patterns argued to cause functional shunting of oxygenated blood through the capillary bed. We used a biophysical model of oxygen transport in tissue to examine how capillary flow disturbances may contribute to the profound changes in CBF after TBI. The analysis suggests that elevated capillary transit time heterogeneity can cause critical reductions in oxygen availability in the absence of ‘classic’ ischemia. We discuss diagnostic and therapeutic consequences of these predictions.

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El-Tawil, Salwa, Grant Mair, Xuya Huang, Eleni Sakka, Jeb Palmer, Ian Ford, Lalit Kalra, et al. "Observer Agreement on Computed Tomography Perfusion Imaging in Acute Ischemic Stroke." Stroke 50, no. 11 (November 2019): 3108–14. http://dx.doi.org/10.1161/strokeaha.119.026238.

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Background and Purpose— Computed tomography (CT) perfusion (CTP) provides potentially valuable information to guide treatment decisions in acute stroke. Assessment of interobserver reliability of CTP has, however, been limited to small, mostly single center studies. We performed a large, internet-based study to assess observer reliability of CTP interpretation in acute stroke. Methods— We selected 24 cases from the IST-3 (Third International Stroke Trial), ATTEST (Alteplase Versus Tenecteplase for Thrombolysis After Ischaemic Stroke), and POSH (Post Stroke Hyperglycaemia) studies to illustrate various perfusion abnormalities. For each case, observers were presented with noncontrast CT, maps of cerebral blood volume, cerebral blood flow, mean transit time, delay time, and thresholded penumbra maps (dichotomized into penumbra and core), together with a short clinical vignette. Observers used a structured questionnaire to record presence of perfusion deficit, its extent compared with ischemic changes on noncontrast CT, and an Alberta Stroke Program Early CT Score for noncontrast CT and CTP. All images were viewed, and responses were collected online. We assessed observer agreement with Krippendorff-α. Intraobserver agreement was assessed by inviting observers who reviewed all scans for a repeat review of 6 scans. Results— Fifty seven observers contributed to the study, with 27 observers reviewing all 24 scans and 17 observers contributing repeat readings. Interobserver agreement was good to excellent for all CTP. Agreement was higher for perfusion maps compared with noncontrast CT and was higher for mean transit time, delay time, and penumbra map (Krippendorff-α =0.77, 0.79, and 0.81, respectively) compared with cerebral blood volume and cerebral blood flow (Krippendorff-α =0.69 and 0.62, respectively). Intraobserver agreement was fair to substantial in the majority of readers (Krippendorff-α ranged from 0.29 to 0.80). Conclusions— There are high levels of interobserver and intraobserver agreement for the interpretation of CTP in acute stroke, particularly of mean transit time, delay time, and penumbra maps.

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Brunozzi, Denise, Sophia F. Shakur, Fady T. Charbel, and Ali Alaraj. "Intracranial contrast transit times on digital subtraction angiography decrease more in patients with delayed intraparenchymal hemorrhage after Pipeline." Interventional Neuroradiology 24, no. 2 (December 12, 2017): 140–45. http://dx.doi.org/10.1177/1591019917747248.

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Background Pipeline embolization devices (PEDs) are used for endovascular treatment of cerebral aneurysms but can be associated with delayed ipsilateral intraparenchymal hemorrhage (DIPH). Changes in intracranial hemodynamics after PED are poorly understood. Objective Here, we assess hemodynamic changes after PED in patients and compare these changes in patients with and without DIPH (DIPH+ and DIPH–). Methods Records of patients with distal internal carotid artery (ICA) aneurysms treated with PED at our institution between 2012 and 2017 were retrospectively reviewed. Regions of interest were selected proximally to PED over the cavernous ICA and distally over the middle cerebral artery (MCA), and then transit times were determined using syngo iFlow software (Siemens). Ratio of MCA to ICA transit time was compared before, after treatment, and at follow-up. Ratios were also compared between DIPH+ and DIPH– subgroups. Correlations between aneurysm size, age, and ratios were investigated. Results Fifty-three patients were included. The ratio of MCA to ICA transit time decreased significantly after PED deployment (1.13 vs. 1.22, p < 0.01). The ratio in the DIPH + subgroup ( n = 4) was significantly lower (1.00 vs. 1.14, p = 0.01) and decreased significantly more (21% vs. 4.4%, p = 0.02) compared to the DIPH– subgroup ( n = 49). The ratio tended to be higher in larger aneurysms at baseline ( r = 0.25, p = 0.07) but not after PED treatment ( r = 0.11, p = 0.15). Age did not correlate with ratio. Conclusion The ratio of MCA to ICA transit time decreases following PED treatment and decreases more in patients with DIPH. These contrast transit time changes can be detected in real time immediately after PED deployment.

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Kamba, Masayuki, Yuji Suto, and Toshihide Ogawa. "Measurement of cerebral mean transit time by dynamic susceptibility contrast magnetic resonance imaging." European Journal of Radiology 31, no. 3 (September 1999): 170–73. http://dx.doi.org/10.1016/s0720-048x(98)00152-1.

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Puls, Imke, Kurt Hauck, Klaus Demuth, Anja Horowski, Mira Schließer, Petra Dörfler, Peter Scheel, et al. "Diagnostic Impact of Cerebral Transit Time in the Identification of Microangiopathy in Dementia." Stroke 30, no. 11 (November 1999): 2291–95. http://dx.doi.org/10.1161/01.str.30.11.2291.

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Kelly, Michael E., Christoph W. Blau, Karen M. Griffin, Oliviero L. Gobbo, James FX Jones, and Christian M. Kerskens. "Quantitative Functional Magnetic Resonance Imaging of Brain Activity Using Bolus-Tracking Arterial Spin Labeling." Journal of Cerebral Blood Flow & Metabolism 30, no. 5 (January 13, 2010): 913–22. http://dx.doi.org/10.1038/jcbfm.2009.284.

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Blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) is the most widely used method for mapping neural activity in the brain. The interpretation of altered BOLD signals is problematic when cerebral blood flow (CBF) or cerebral blood volume change because of aging and/or neurodegenerative diseases. In this study, a recently developed quantitative arterial spin labeling (ASL) approach, bolus-tracking ASL (btASL), was applied to an fMRI experiment in the rat brain. The mean transit time (MTT), capillary transit time (CTT), relative cerebral blood volume of labeled water (rCBVlw), relative cerebral blood flow (rCBF), and perfusion coefficient in the forelimb region of the somatosensory cortex were quantified during neuronal activation and in the resting state. The average MTT and CTT were 1.939±0.175 and 1.606±0.106 secs, respectively, in the resting state. Both times decreased significantly to 1.616±0.207 and 1.305±0.201 secs, respectively, during activation. The rCBVlw, rCBF, and perfusion coefficient increased on average by a factor of 1.123±0.006, 1.353±0.078, and 1.479±0.148, respectively, during activation. In contrast to BOLD techniques, btASL yields physiologically relevant indices of the functional hyperemia that accompanies neuronal activation.

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Sorensen, A. Gregory, William A. Copen, Leif Østergaard, Ferdinando S. Buonanno, R. Gilberto Gonzalez, Guy Rordorf, Bruce R. Rosen, Lee H. Schwamm, Robert M. Weisskoff, and Walter J. Koroshetz. "Hyperacute Stroke: Simultaneous Measurement of Relative Cerebral Blood Volume, Relative Cerebral Blood Flow, and Mean Tissue Transit Time." Radiology 210, no. 2 (February 1999): 519–27. http://dx.doi.org/10.1148/radiology.210.2.r99fe06519.

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Mouridsen, Kim, Mikkel Bo Hansen, Leif Østergaard, and Sune Nørhøj Jespersen. "Reliable Estimation of Capillary Transit Time Distributions Using DSC-MRI." Journal of Cerebral Blood Flow & Metabolism 34, no. 9 (June 18, 2014): 1511–21. http://dx.doi.org/10.1038/jcbfm.2014.111.

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The regional availability of oxygen in brain tissue is traditionally inferred from the magnitude of cerebral blood flow ( CBF) and the concentration of oxygen in arterial blood. Measurements of CBF are therefore widely used in the localization of neuronal response to stimulation and in the evaluation of patients suspected of acute ischemic stroke or flow-limiting carotid stenosis. It was recently demonstrated that capillary transit time heterogeneity ( CTH) limits maximum oxygen extraction fraction ( OEFmax) that can be achieved for a given CBF. Here we present a statistical approach for determining CTH, mean transit time ( MTT), and CBF using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). Using numerical simulations, we demonstrate that CTH, MTT, and OEFmax can be estimated with low bias and variance across a wide range of microvascular flow patterns, even at modest signal-to-noise ratios. Mean transit time estimated by singular value decomposition (SVD) deconvolution, however, is confounded by CTH. The proposed technique readily identifies malperfused tissue in acute stroke patients and appears to highlight information not detected by the standard SVD technique. We speculate that this technique permits the non-invasive detection of tissue with impaired oxygen delivery in neurologic disorders such as acute ischemic stroke and Alzheimer's disease during routine diagnostic imaging.

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Wilson, Timothy D., J. Kevin Shoemaker, R. Kozak, T.-Y. Lee, and Adrian W. Gelb. "Reflex-Mediated Reduction in Human Cerebral Blood Volume." Journal of Cerebral Blood Flow & Metabolism 25, no. 1 (January 2005): 136–43. http://dx.doi.org/10.1038/sj.jcbfm.9600015.

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Adrenergic nerves innervate the human cerebrovasculature, yet the functional role of neurogenic influences on cerebral hemodynamics remains speculative. In the current study, regional cerebrovascular responses to sympathoexcitatory reflexes were evaluated. In eight volunteers, contrast-enhanced computed tomography was performed at baseline, –40 mmHg lower body negative pressure (LBNP), and a cold pressor test (CPT). Cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF) were evaluated in cortical gray matter (GM), white matter (WM), and basal ganglia/thalamus (BGT) regions. Lower body negative pressure resulted in tachycardia and decreased central venous pressure while mean arterial pressure was maintained. Cold pressor test resulted in increased mean arterial pressure concomitant with tachycardia but no change in central venous pressure. Neither reflex altered end-tidal carbon dioxide. Cerebral blood volume was reduced in GM during both LBNP and CPT ( P<0.05) but was unchanged in WM and BGT. Mean transit time was reduced in WM and GM during CPT ( P<0.05). Cerebral blood flow was only modestly affected with either reflex ( P<0.07). The combined reductions in GM CBV (˜ –25%) and MTT, both with and without any change in central venous pressure, with small CBF changes (˜ –11%), suggest that active venoconstriction contributed to the volume changes. These data demonstrate that CBV is reduced during engagement of sympathoexcitatory reflexes and that these cerebrovascular changes are heterogeneously distributed.

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Touho, Hajime, and Jun Karasawa. "Evaluation of time-dependent thresholds of cerebral blood flow and transit time during the acute stage of cerebral embolism: A retrospective study." Surgical Neurology 46, no. 2 (August 1996): 135–45. http://dx.doi.org/10.1016/0090-3019(95)00464-5.

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Bartolini, A., B. Gasparetto, F. Roncallo, L. Sullo, and L. Giberti. "Misure di flusso cerebrale, tempo di transito, volume vascolare e permebilità di barriera nelle lesioni ischemiche con immagini funzionali derivate dall'angio-TC." Rivista di Neuroradiologia 10, no. 2_suppl (October 1997): 124–27. http://dx.doi.org/10.1177/19714009970100s249.

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Transit time, vascular volume, blood brain barrier permeability and rCBF images, obtained by computerized analysis of Angio-CT, were applied to the study of cerebral ischemic patients. Our results show a considerable increase in information with respect to conventional contrast examination.

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Wilkinson, Iain D., David A. Jellineck, David Levy, Frederik L. Giesel, Charles A. J. Romanowski, Barbara-Ann Miller, and Paul D. Griffiths. "Dexamethasone and Enhancing Solitary Cerebral Mass Lesions: Alterations in Perfusion and Blood-tumor Barrier Kinetics Shown by Magnetic Resonance Imaging." Neurosurgery 58, no. 4 (April 1, 2006): 640–46. http://dx.doi.org/10.1227/01.neu.0000204873.68395.a0.

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Abstract OBJECTIVE: Glucocorticoid analogues are often administered to patients with intracranial space-occupying lesions. Clinical response can be dramatic, but the neurophysiological response is not well documented. This study sought to investigate the blood-lesion barrier, blood-brain barrier, and cerebral perfusion characteristics of patients who have undergone such therapy using magnetic resonance imaging. METHODS: Seventeen patients with intracranial mass-enhancing lesions underwent magnetic resonance imaging before and after 3 days of high-dose dexamethasone therapy. Assessments of blood-lesion barrier and blood-brain barrier integrity were based on a dynamic T1-weighted exogenous contrast technique that yielded the normalized maximal change in contrast uptake (T1-uptake). Perfusion was assessed using a dynamic T2*-weighted exogenous contrast technique to yield relative regional cerebral blood volume and first-moment mean transit time. Comparisons were made in T1-uptake, regional cerebral blood volume, and first-moment mean transit time of both enhancing lesion and contralateral normal-appearing white matter (CNAWM) obtained before and after dexamethasone. RESULTS: Significant reduction in T1-uptake was observed (19% decrease, P < 0.005) within enhancing pathological tissue, whereas no significant alteration was detected in CNAWM. Regional cerebral blood volume was significantly reduced in both enhancing tissue (28% decrease, P < 0.005) and in CNAWM (20% decrease, P < 0.001). Bolus first-moment mean transit time significantly increased (2.0 s prolongation, P < 0.05) in CNAWM, whereas there was no significant change (1.4 s prolongation, P > 0.05) within enhancing tissue. CONCLUSION: Glucocorticoid-analogue therapy not only affects the permeability of the blood-lesion barrier and lesion blood volume but also affects blood flow within normal-appearing contralateral parenchyma. There is a need for controls in steroid therapy in magnetic resonance imaging studies, which involve assessments of cerebrovascular function.

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Czabanka, Marcus, Pablo Peña-Tapia, Gerrit Alexander Schubert, Johannes Woitzik, Peter Horn, Peter Schmiedek, and Peter Vajkoczy. "Clinical Implications of Cortical Microvasculature in Adult Moyamoya Disease." Journal of Cerebral Blood Flow & Metabolism 29, no. 8 (June 3, 2009): 1383–87. http://dx.doi.org/10.1038/jcbfm.2009.69.

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We analyzed cortical microvascular parameters using intraoperative ICG (Indocyaninegreen)-Videoangiography in 13 patients with Moyamoya disease, and carried out correlative studies by comparing them with clinical parameters obtained by digital subtraction angiography, physical examination, and regional cerebral blood flow studies. Patients with reduced cerebrovascular reserve capacity were characterized by increased microvascular surface area (MVSA). In addition, MVSA correlated positively with arterial microvascular transit time. Asymptomatic patients were characterized by increased arterial microvascular transit time. We show that patients with a higher arteriogenic potential to alter cortical microvasculature are characterized by a more favorable hemodynamic situation and reduced clinical symptoms.

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Chou, Yen-Chun, Chia-Feng Lu, Wan-Yuo Guo, and Yu-Te Wu. "Blind Source Separation of Hemodynamics from Magnetic Resonance Perfusion Brain Images Using Independent Factor Analysis." International Journal of Biomedical Imaging 2010 (2010): 1–9. http://dx.doi.org/10.1155/2010/360568.

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Perfusion magnetic resonance brain imaging induces temporal signal changes on brain tissues, manifesting distinct blood-supply patterns for the profound analysis of cerebral hemodynamics. We employed independent factor analysis to blindly separate such dynamic images into different maps, that is, artery, gray matter, white matter, vein and sinus, and choroid plexus, in conjunction with corresponding signal-time curves. The averaged signal-time curve on the segmented arterial area was further used to calculate the relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and mean transit time (MTT). The averaged ratios for rCBV, rCBF, and MTT between gray and white matters for normal subjects were congruent with those in the literature.

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Alemseged, Fana, Darshan G. Shah, Andrew Bivard, Timothy J. Kleinig, Nawaf Yassi, Marina Diomedi, Francesca Di Giuliano, et al. "Cerebral blood volume lesion extent predicts functional outcome in patients with vertebral and basilar artery occlusion." International Journal of Stroke 14, no. 5 (November 21, 2017): 540–47. http://dx.doi.org/10.1177/1747493017744465.

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Background CT perfusion may improve diagnostic accuracy in posterior circulation stroke. The posterior circulation Acute Stroke Prognosis Early CT score (pc-ASPECTS) on Computed Tomography Angiography source images (CTA-SI) predicts functional outcome in patients with basilar artery occlusion. Aims We assessed the prognostic value of pc-ASPECTS on CT perfusion in patients with vertebral and basilar artery occlusion (VBAO) in comparison with CTA-SI. Methods Whole-brain CT perfusion from consecutive stroke patients with VBAO at four stroke centers was retrospectively analyzed. pc-ASPECTS – a 10-point score assessing hypoattenuation on CTA-SI – was calculated from CT perfusion parameters as focally reduced cerebral blood flow or cerebral blood volume, focally increased time to peak of the deconvolved tissue residue function (Tmax) or mean transit time. Two investigators independently reviewed the images. Reliability was assessed with intraclass correlation coefficient. Good outcome was defined as modified Rankin scale ≤3 at three months. Results We included 60 patients with VBAO. After assessment of four CT perfusion maps simultaneously, area-under-ROC curve (AROC) was 0.83 (95%CI 0.72–0.93) for cerebral blood volume, 0.76 (95%CI 0.64–0.89) for cerebral blood flow, 0.77 (95%CI 0.64–0.89) for Tmax, 0.70 (95%CI 0.56–0.84) for mean transit time versus area-under-ROC curve 0.64 (95%CI 0.50–0.79) for CTA-SI. Cerebral blood volume had greater accuracy compared with CTA-SI for poor outcome (p = 0.04). In logistic regression analysis, cerebral blood volume pc-ASPECTS≤8 was independently associated with poor outcome (OR 9.3 95%CI 2.2–41; p = 0.003, adjusted for age and clinical severity). Inter-rater agreement was substantial for cerebral blood volume pc-ASPECTS (intraclass correlation coefficient 0.82 95%CI 0.71–0.90 versus 0.67 for CTA-SI 95%CI 0.43–0.81). Conclusions Cerebral blood volume pc-ASPECTS may identify VBAO patients at higher risk of disability.

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Kang, Hye-Min, Inkyung Sohn, Seunggyu Kim, Daehwan Kim, Junyang Jung, Joo-Won Jeong, and Chan Park. "Optical Measurement of Mouse Strain Differences in Cerebral Blood Flow Using Indocyanine Green." Journal of Cerebral Blood Flow & Metabolism 35, no. 6 (April 1, 2015): 912–16. http://dx.doi.org/10.1038/jcbfm.2015.50.

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C57BL/6 mice have more cerebral arterial branches and collaterals than BALB/c mice. We measured and compared blood flow dynamics of the middle cerebral artery (MCA) in these two strains, using noninvasive optical imaging with indocyanine green (ICG). Relative maximum fluorescence intensity ( Imax) and the time needed for ICG to reach Imax in the MCA of C57BL/c were lower than that in BALB/c mice. Moreover, the mean transit time was significantly lower in C57BL/6 than in BALB/c mice. These data suggest that the higher number of arterial branches and collaterals in C57BL/6 mice yields a lower blood flow per cerebral artery.

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Tong, Yunjie, Jinxia (Fiona) Yao, J. Jean Chen, and Blaise deB Frederick. "The resting-state fMRI arterial signal predicts differential blood transit time through the brain." Journal of Cerebral Blood Flow & Metabolism 39, no. 6 (January 15, 2018): 1148–60. http://dx.doi.org/10.1177/0271678x17753329.

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Previous studies have found that aperiodic, systemic low-frequency oscillations (sLFOs) are present in blood-oxygen-level-dependent (BOLD) data. These signals are in the same low frequency band as the “resting state” signal; however, they are distinct signals which represent non-neuronal, physiological oscillations. The same sLFOs are found in the periphery (i.e. finger tips) as changes in oxy/deoxy-hemoglobin concentration using concurrent near-infrared spectroscopy. Together, this evidence points toward an extra-cerebral origin of these sLFOs. If this is the case, it is expected that these sLFO signals would be found in the carotid arteries with time delays that precede the signals found in the brain. To test this hypothesis, we employed the publicly available MyConnectome dataset (a two-year longitudinal study of a single subject) to extract the sLFOs in the internal carotid arteries (ICAs) with the help of the T1/T2-weighted images. Significant, but negative, correlations were found between the LFO BOLD signals from the ICAs and (1) the global signal (GS), (2) the superior sagittal sinus, and (3) the jugulars. We found the consistent time delays between the sLFO signals from ICAs, GS and veins which coincide with the blood transit time through the cerebral vascular tree.

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MATSUMURA, Hideaki, Yoshiro ITO, Kazuya UEMURA, Yasunobu NAKAI, Yoji KOMATSU, Eiichi ISHIKAWA, Yuji MATSUMARU, and Akira MATSUMURA. "Prediction of the Cerebral Hyperperfusion Phenomenon after Carotid Endarterectomy Using a Transit Time Flowmeter." Neurologia medico-chirurgica 60, no. 2 (2020): 94–100. http://dx.doi.org/10.2176/nmc.oa.2019-0114.

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Murphy, Matthew J., Kenneth M. Tichauer, Louise Sun, Xiaogang Chen, and Ting-Yim Lee. "Mean transit time as an index of cerebral perfusion pressure in experimental systemic hypotension." Physiological Measurement 32, no. 4 (February 23, 2011): 395–405. http://dx.doi.org/10.1088/0967-3334/32/4/002.

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Wilson, David A., Marco Ferrari, Daniel F. Hanley, Mark C. Rogers, and Richard J. Traystman. "CEREBRAL BLOOD FLOW/VOLUME/MEAN TRANSIT TIME RELATIONSHIPS IN THE DOG DURING HEMORRHAGIC HYPOTENSION." Critical Care Medicine 15, no. 4 (April 1987): 432. http://dx.doi.org/10.1097/00003246-198704000-00186.

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Beck, Jürgen, Walter Stummer, Jens Lehmberg, Alexander Baethmann, and Eberhard Uhl. "ARTERIOVENOUS TRANSIT TIME AS A MEASURE FOR MICROVASCULAR PERFUSION IN CEREBRAL ISCHEMIA AND REPERFUSION." Neurosurgery 61, no. 4 (October 1, 2007): 826–34. http://dx.doi.org/10.1227/01.neu.0000298912.86506.b1.

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Ito, Hiroshi, Iwao Kanno, Kazuhiro Takahashi, Masanobu Ibaraki, and Shuichi Miura. "Regional distribution of human cerebral vascular mean transit time measured by positron emission tomography." NeuroImage 19, no. 3 (July 2003): 1163–69. http://dx.doi.org/10.1016/s1053-8119(03)00156-3.

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Qin, Qin, Wenbo Li, Dexiang Liu, and John J. Strouse. "Simultaneous Measurement of Cerebral Blood Flow and Arterial Transit Time for Sickle Cell Disease." Blood 128, no. 22 (December 2, 2016): 1298. http://dx.doi.org/10.1182/blood.v128.22.1298.1298.

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Abstract Introduction Studies of patients with ischemic stroke and silent cerebral infarcts from sickle cell anemia (SCA) have revealed abnormalities of both large and small vessels. Cerebral blood flow (CBF), a measure of the microvascular perfusion of the brain, has been recognized as a potentially sensitive and specific indicator of early cerebrovascular impairment in both children and adults with SCA. Arterial spin labeling (ASL) MRI is a non-invasive technique to acquire perfusion-weighted signal. This is typically at a single post-labeling delay (PLD) and provides only CBF measurement. The addition of multiple PLDs also permits the measurement of arterial transit time (ATT), the transit time from the labeled plane to the imaging voxels. ATT is prolonged with stenosis and/or occlusion of large vessels. In order to allow detection of both small and large vessel disease simultaneously for SCA, we employed a 4D whole-brain ASL protocol to measure CBF and ATT concurrently. Methods Experiments were performed on a 3T Philips Achieva scanner using a 32-channel head coil for reception. Seven healthy volunteers (age 36 ± 8 yrs; 3M / 4F) and 5 SCA patients with no history of stroke, recent transfusion, or renal impairment (21 ± 3 yrs; 3M / 2F) were enrolled after informed consent. The clinical laboratory performed complete blood counts on venous blood obtained the same day. The Pseudo continuous ASL (PCASL) sequence was implemented with 1000ms labeling duration and 12 PLDs (from 500 ms to 2700 ms in 200 ms intervals). A 3D acquisition scheme was employed with a field of view of 240 x 240 x 140 mm3 and acquisition resolution = 6.7 x 7.4 x 7 mm3. Total scan time was about 5 min. Fitting was performed per voxel using nonlinear-least-squares algorithm (Matlab) and maps of CBF and ATT were extracted concurrently. For each subject, five ROIs in the gray matter (frontal lobe, temporal lobe, parietal lobe, occipital lobe, and cerebellum) were manually drawn bilaterally from the corresponding anatomical image. Results Figure 1 display representative CBF and ATT maps of a participant with SCA estimated from the multi-delay PCASL scans. CBF maps (Figure 1a) were found to be uniform within the gray matter. White matter has lower CBF than gray matter and shows a longer transit time as expected. ATT maps (Figure 1b) reflected the heterogeneity between different brain regions. ATT values were about 200-400 ms shorter in the temporal lobe and medial frontal lobe, compared to the parietal/occipital lobes and cerebellum. Averaged CBF values from the five ROIs of all the subjects were calculated. For the control group (Hb = 14.1 ± 1.5 g/dL) and SCA group (Hb = 9.1 ± 2.1 g/dL), the mean CBF values were 49 ± 15 mL/100g/min vs 102 ± 23 mL/100g/min, and the mean ATT values were 1662 ± 317 ms vs 1245 ± 171 ms, respectively. Linear regression identified significant correlations between mean CBF and hemoglobin: CBF = - 9.8 Hb + 189 (r = -0.94; p < 0.001) and ATT = 81.2 Hb + 511 (r = 0.76; p = 0.004) (Figure 2). Discussion We have successfully implemented a fast and non-invasive MRI technique to measure two perfusion metrics (CBF and ATT) with a whole-brain coverage on SCA patients. It was well established only using other perfusion imaging modalities that CBF, among subjects with normal hemodynamic regulation and without neurovascular impairment, is inversely correlated with hemoglobin concentration. Conversely, a linear correlation between ATT and Hb is expected as a result of adaptive vasodilatation and lower blood viscosity. Our study's cross-subject validation of this relationship using the multi-delay PCASL method with 3D acquisition shows the potential of this technique to accurately define blood flow from both small and large vessels. This may be useful to identify people with SCA at increased risk of brain injury from silent cerebral infarct and stroke. Figure 1 Representative CBF (a) and ATT (b) maps acquired with 3D whole-brain coverage in axial, coronal and sagittal planes. Figure 1. Representative CBF (a) and ATT (b) maps acquired with 3D whole-brain coverage in axial, coronal and sagittal planes. Figure 2 Linear relationship between Hb and (a) CBF; (b) ATT. Figure 2. Linear relationship between Hb and (a) CBF; (b) ATT. Disclosures No relevant conflicts of interest to declare.

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Vogel, J., R. Abounader, H. Schrock, K. Zeller, R. Duelli, and W. Kuschinsky. "Parallel changes of blood flow and heterogeneity of capillary plasma perfusion in rat brains during hypocapnia." American Journal of Physiology-Heart and Circulatory Physiology 270, no. 4 (April 1, 1996): H1441—H1445. http://dx.doi.org/10.1152/ajpheart.1996.270.4.h1441.

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Plasma perfusion patterns were investigated in brain capillaries during decreased cerebral blood flow induced by hyperventilation. Anesthetized rats were decapitated 3-4 s after being given an intravenous bolus injection of Evans blue dye. the measured steep increase of the arterial dye concentration at this moment ensures that different capillary plasma transit times are reflected in different intracapillary dye concentrations. The observed heterogeneity of capillary plasma transit time was expressed as the coefficient of variation (means +/- SD) of the intracapillary dye concentrations. For comparison, cerebral blood flow was determined at comparable PCO2 values in a second experimental group. At arterial PCO2 values between 40 and 25 mmHg, the cerebral blood flow and the coefficient of variation of the intracapillary dye concentration decreased with decreasing PCO2, whereas at PCO2 values <25 mmHg cerebral blood flow and coefficient of variation did not correlate with the arterial PCO2. However, it cannot be excluded that the coefficient of variation of the intracapillary dye concentration increases between 25 and 14 mmHg and decreases between 14 and 10 mmHg. It is concluded that the reduction of cerebral blood flow measured during moderate hypocapnia is paralleled by a decreased heterogeneity of the brain capillary perfusion. During severe hypocapnia this relationship is lost, indicating a potential disturbance of the cerebral microcirculation.

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Bartolini, A., B. Gasparetto, F. Roncallo, L. Sullo, and L. Giberti. "Valutazione emodinamica delle malformazioni vascolari cerebrali con Angio-TC." Rivista di Neuroradiologia 10, no. 2_suppl (October 1997): 143–44. http://dx.doi.org/10.1177/19714009970100s258.

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Transit time, vascular volume, blood brain barrier permeability and rCBF images, obtained by computerized analysis of Angio-CT, were applied to the study of cerebral vascular malformations. Useful information with respect to the haemodynamic conditions of the lesions as well as the surrounding brain tissue was obtained.

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Martin, Steve Z., Vince I. Madai, Federico C. von Samson-Himmelstjerna, Matthias A. Mutke, Miriam Bauer, Cornelius X. Herzig, Stefan Hetzer, Matthias Günther, and Jan Sobesky. "3D GRASE Pulsed Arterial Spin Labeling at Multiple Inflow Times in Patients with Long Arterial Transit Times: Comparison with Dynamic Susceptibility-Weighted Contrast-Enhanced MRI at 3 Tesla." Journal of Cerebral Blood Flow & Metabolism 35, no. 3 (March 2015): 392–401. http://dx.doi.org/10.1038/jcbfm.2014.200.

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Pulsed arterial spin labeling (PASL) at multiple inflow times (multi-TIs) is advantageous for the measurement of brain perfusion in patients with long arterial transit times (ATTs) as in steno-occlusive disease, because bolus-arrival-time can be measured and blood flow measurements can be corrected accordingly. Owing to its increased signal-to-noise ratio, a combination with a three-dimensional gradient and spin echo (GRASE) readout allows acquiring a sufficient number of multi-TIs within a clinically feasible acquisition time of 5 minutes. We compared this technique with the clinical standard dynamic susceptibility-weighted contrast-enhanced imaging—magnetic resonance imaging in patients with unilateral stenosis >70% of the internal carotid or middle cerebral artery (MCA) at 3 Tesla. We performed qualitative (assessment by three expert raters) and quantitative (region of interest (ROI)/volume of interest (VOI) based) comparisons. In 43 patients, multi-TI PASL-GRASE showed perfusion alterations with moderate accuracy in the qualitative analysis. Quantitatively, moderate correlation coefficients were found for the MCA territory (ROI based: r=0.52, VOI based: r=0.48). In the anterior cerebral artery (ACA) territory, a readout related right-sided susceptibility artifact impaired correlation (ROI based: r=0.29, VOI based: r=0.34). Arterial transit delay artifacts were found only in 12% of patients. In conclusion, multi-TI PASL-GRASE can correct for arterial transit delay in patients with long ATTs. These results are promising for the transfer of ASL to the clinical practice.

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Journal articles on the topic 'Cerebral transit time'

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