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Hachaj, Tomasz, and Marek R. Ogiela. "Automatic Detection and Lesion Description in Cerebral Blood Flow and Cerebral Blood Volume Perfusion Maps." Journal of Signal Processing Systems 61, no. 3 (February 4, 2010): 317–28. http://dx.doi.org/10.1007/s11265-010-0454-0.
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Bergonzi, Karla M., Adam Q. Bauer, Patrick W. Wright, and Joseph P. Culver. "Mapping Functional Connectivity Using Cerebral Blood Flow in the Mouse Brain." Journal of Cerebral Blood Flow & Metabolism 35, no. 3 (March 2015): 367–70. http://dx.doi.org/10.1038/jcbfm.2014.211.
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Brain function can be assessed from resting-state functional connectivity (rs-fc) maps, most commonly created by analyzing the dynamics of cerebral hemoglobin concentration. Here, we develop the use of Laser Speckle Contrast Imaging (LSCI) for mapping rs-fc using cerebral blood flow (CBF) dynamics. Because LSCI is intrinsically noisy, we used spatial and temporal averaging to sufficiently raise the signal-to-noise ratio for observing robust functional networks. Although CBF-based rs-fc maps in healthy mice are qualitatively similar to simultaneously-acquired [HbO2]-based maps, some quantitative regional differences were observed. These combined flow/concentration maps might help clarify mechanisms involved in network disruption during disease.
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Johannsen, P., J. Jakobsen, and A. Gjedde. "Statistical maps of cerebral blood flow deficits in Alzheimer’s disease." European Journal of Neurology 7, no. 4 (July 2000): 385–92. http://dx.doi.org/10.1046/j.1468-1331.2000.00088.x.
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Scremin, Oscar U., Daniel P. Holschneider, Kevin Chen, Mingen G. Li, and Jean C. Shih. "Cerebral cortical blood flow maps are reorganized in MAOB-deficient mice." Brain Research 824, no. 1 (April 1999): 36–44. http://dx.doi.org/10.1016/s0006-8993(99)01167-1.
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Lacalle-Aurioles, María, José M. Mateos-Pérez, Juan A. Guzmán-De-Villoria, Javier Olazarán, Isabel Cruz-Orduña, Yasser Alemán-Gómez, María-Elena Martino, and Manuel Desco. "Cerebral Blood Flow is an Earlier Indicator of Perfusion Abnormalities than Cerebral Blood Volume in Alzheimer's Disease." Journal of Cerebral Blood Flow & Metabolism 34, no. 4 (January 15, 2014): 654–59. http://dx.doi.org/10.1038/jcbfm.2013.241.
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The purpose of this study was to elucidate whether cerebral blood flow (CBF) can better characterize perfusion abnormalities in predementia stages of Alzheimer's disease (AD) than cerebral blood volume (CBV) and whether cortical atrophy is more associated with decreased CBV or with decreased CBF. We compared measurements of CBV, CBF, and mean cortical thickness obtained from magnetic resonance images in a group of healthy controls, patients with mild cognitive impairment (MCI) who converted to AD after 2 years of clinical follow-up (MCI-c), and patients with mild AD. A significant decrease in perfusion was detected in the parietal lobes of the MCI-c patients with CBF parametric maps but not with CBV maps. In the MCI-c group, a negative correlation between CBF values and cortical thickness in the right parahippocampal gyrus suggests an increase in CBF that depends on cortical atrophy in predementia stages of AD. Our study also suggests that CBF deficits appear before CBV deficits in the progression of AD, as CBV abnormalities were only detected at the AD stage, whereas CBF changes were already detected in the MCI stage. These results confirm the hypothesis that CBF is a more sensitive parameter than CBV for perfusion abnormalities in MCI-c patients.
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Taylor, Stephan F., Satoshi Minoshima, and Robert A. Koeppe. "Instability of Localization of Cerebral Blood Flow Activation Foci with Parametric Maps." Journal of Cerebral Blood Flow & Metabolism 13, no. 6 (November 1993): 1040–41. http://dx.doi.org/10.1038/jcbfm.1993.134.
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Adam, Jean-François, Hélène Elleaume, Géraldine Le Duc, Stéphanie Corde, Anne-Marie Charvet, Irène Troprès, Jean-François Le Bas, and François Estève. "Absolute Cerebral Blood Volume and Blood Flow Measurements Based on Synchrotron Radiation Quantitative Computed Tomography." Journal of Cerebral Blood Flow & Metabolism 23, no. 4 (April 2003): 499–512. http://dx.doi.org/10.1097/01.wcb.0000050063.57184.3c.
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Synchrotron radiation computed tomography opens new fields by using monochromatic x-ray beams. This technique allows one to measure in vivo absolute contrast-agent concentrations with high accuracy and precision, and absolute cerebral blood volume or flow can be derived from these measurements using tracer kinetic methods. The authors injected an intravenous bolus of an iodinated contrast agent in healthy rats, and acquired computed tomography images to follow the temporal evolution of the contrast material in the blood circulation. The first image acquired before iodine infusion was subtracted from the others to obtain computed tomography slices expressed in absolute iodine concentrations. Cerebral blood volume and cerebral blood flow maps were obtained after correction for partial volume effects. Mean cerebral blood volume and flow values (n = 7) were 2.1 ± 0.38 mL/100 g and 129 ± 18 mL · 100 g–1 · min–1 in the parietal cortex; and 1.92 ± 0.32 mL/100 g and 125 ± 17 mL · 100 g–1 · min–1 in the caudate putamen, respectively. Synchrotron radiation computed tomography has the potential to assess these two brain-perfusion parameters.
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Ohta, Shinsuke, Ernst Meyer, Hitoshi Fujita, David C. Reutens, Alan Evans, and Albert Gjedde. "Cerebral [15O]Water Clearance in Humans Determined by PET: I. Theory and Normal Values." Journal of Cerebral Blood Flow & Metabolism 16, no. 5 (September 1996): 765–80. http://dx.doi.org/10.1097/00004647-199609000-00002.
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When used to measure blood flow in the brain, water leaves a residue in the vascular bed that influences the estimation of blood flow by current methods. To assess the magnitude of this influence, we developed a two-compartment model of blood flow with separate parameters for transport and vascular distribution of brain water. Maps of the water clearance, K1 into brain tissue, separated from the circulation by a measurably resistant blood–brain barrier (BBB), were generated by time-weighted integration. Depending on the validity of the assumptions underlying the two-compartment model presented here, the maps revealed a significant overestimation of the clearance of water when the vascular residue was ignored. Maps of Vo the estimate of the apparent vascular distribution volume of tracer H215O, clearly revealed major cerebral arteries. Thus, we claim that the accumulation of radioactive water in brain tissue also reflects the volume of the arterial vascular bed of the brain.
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Arteaga, Daniel F., Megan K. Strother, L. Taylor Davis, Matthew R. Fusco, Carlos C. Faraco, Brent A. Roach, Allison O. Scott, and Manus J. Donahue. "Planning-free cerebral blood flow territory mapping in patients with intracranial arterial stenosis." Journal of Cerebral Blood Flow & Metabolism 37, no. 6 (July 20, 2016): 1944–58. http://dx.doi.org/10.1177/0271678x16657573.
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A noninvasive method for quantifying cerebral blood flow and simultaneously visualizing cerebral blood flow territories is vessel-encoded pseudocontinuous arterial spin labeling MRI. However, obstacles to acquiring such information include limited access to the methodology in clinical centers and limited work on how clinically acquired vessel-encoded pseudocontinuous arterial spin labeling data correlate with gold-standard methods. The purpose of this work is to develop and validate a semiautomated pipeline for the online quantification of cerebral blood flow maps and cerebral blood flow territories from planning-free vessel-encoded pseudocontinuous arterial spin labeling MRI with gold-standard digital subtraction angiography. Healthy controls (n = 10) and intracranial atherosclerotic disease patients (n = 34) underwent 3.0 T MRI imaging including vascular (MR angiography) and hemodynamic (cerebral blood flow-weighted arterial spin labeling) MRI. Patients additionally underwent catheter and/or CT angiography. Variations in cross-territorial filling were grouped according to diameters of circle of Willis vessels in controls. In patients, Cohen’s k-statistics were computed to quantify agreement in perfusion patterns between vessel-encoded pseudocontinuous arterial spin labeling and angiography. Cross-territorial filling patterns were consistent with circle of Willis anatomy. The intraobserver Cohen's k-statistics for cerebral blood flow territory and digital subtraction angiography perfusion agreement were 0.730 (95% CI = 0.593–0.867; reader one) and 0.708 (95% CI = 0.561–0.855; reader two). These results support the feasibility of a semiautomated pipeline for evaluating major neurovascular cerebral blood flow territories in patients with intracranial atherosclerotic disease.
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Kato, Naoki, Vincent Prinz, Julius Dengler, and Peter Vajkoczy. "Blood Flow Assessment of Arteriovenous Malformations Using Intraoperative Indocyanine Green Videoangiography." Stroke Research and Treatment 2019 (March 17, 2019): 1–8. http://dx.doi.org/10.1155/2019/7292304.
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Intraoperative indocyanine green (ICG) videoangiography is widely used in patients undergoing neurosurgery. FLOW800 is a recently developed analytical tool for ICG videoangiography to assess semi-quantitative flow dynamics; however, its efficacy is unknown. In this study, we evaluated its functionality in the assessment of flow dynamics of arteriovenous malformation (AVM) through ICG videoangiography under clinical settings. ICG videoangiography was performed in the exposed AVM in eight patients undergoing surgery. FLOW800 analysis was applied directly, and gray-scale and color-coded maps of the surgical field were obtained. After surgery, a region of interest was placed on the individual vessels to obtain time-intensity curves. Parameters of flow dynamics, including the maximum intensity, transit time, and cerebral blood flow index, were calculated using the curves. The color-coded maps provided high-resolution images; however, reconstruction of colored images was restricted by the depth, approach angle, and brain swelling. Semi-quantitative parameters were similar among the feeders, niduses, and drainers. However, a higher cerebral blood flow index was observed in the feeders of large AVM (>3 cm) than in those of small AVM (P < 0.05). Similarly, the cerebral blood flow index values were positively correlated with the nidus volume (P < 0.01). FLOW800 enabled visualization of the AVM structure and safer resection, except in case of deep-seated AVM. Moreover, semi-quantitative values in the individual vessels through using ICG intensity diagram showed different patterns according to size of the AVM. ICG videoangiography showed good performance in evaluating flow dynamics of the AVM in patients undergoing surgery.
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Renú, Arturo, Carlos Laredo, Raúl Tudela, Xabier Urra, Antonio Lopez-Rueda, Laura Llull, Laura Oleaga, Sergio Amaro, and Ángel Chamorro. "Brain hemorrhage after endovascular reperfusion therapy of ischemic stroke: a threshold-finding whole-brain perfusion CT study." Journal of Cerebral Blood Flow & Metabolism 37, no. 1 (July 22, 2016): 153–65. http://dx.doi.org/10.1177/0271678x15621704.
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Endovascular reperfusion therapy is increasingly used for acute ischemic stroke treatment. The occurrence of parenchymal hemorrhage is clinically relevant and increases with reperfusion therapies. Herein we aimed to examine the optimal perfusion CT-derived parameters and the impact of the duration of brain ischemia for the prediction of parenchymal hemorrhage after endovascular therapy. A cohort of 146 consecutive patients with anterior circulation occlusions and treated with endovascular reperfusion therapy was analyzed. Recanalization was assessed at the end of reperfusion treatment, and the rate of parenchymal hemorrhage at follow-up neuroimaging. In regression analyses, cerebral blood volume and cerebral blood flow performed better than Delay Time maps for the prediction of parenchymal hemorrhage. The most informative thresholds (receiver operating curves) for relative cerebral blood volume and relative cerebral blood flow were values lower than 2.5% of normal brain. In binary regression analyses, the volume of regions with reduced relative cerebral blood volume and/or relative cerebral blood flow was significantly associated with an increased risk of parenchymal hemorrhage, as well as delayed vessel recanalization. These results highlight the relevance of the severity and duration of ischemia as drivers of blood-brain barrier disruption in acute ischemic stroke and support the role of perfusion CT for the prediction of parenchymal hemorrhage.
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Valeeva, K. G., S. K. Perminova, A. Ya Nazipova, S. V. Kurochkin, and A. A. Yakupova. "A trial of the use of perfusion computed tomography of the brain in combination with transcranial Doppler ultrasonography of blood vessels in patients with acute cerebrovascular accident." Kazan medical journal 101, no. 1 (February 11, 2020): 124–31. http://dx.doi.org/10.17816/kmj2020-124.
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Aim. Assessment of cerebral blood flow in various vascular beds in patients with an acute cerebrovascular accident in the acute period by perfusion computed tomography in combination with transcranial Doppler ultrasonography of cerebral vessels.
Methods. Data was analyzed from perfusion computed tomography of the brain and transcranial Doppler ultrasonography in 35 patients with an acute cerebrovascular accident, based at the vascular centre of the City Clinical Hospital No. 7 of Kazan. The study included 18 (51.4%) women and 17 (48.6%) men who had arrived in the first hours after a vascular accident. When analyzing the stroke subtype, atherothrombotic subtype was determined in 27 (77.1%) patients, cardioembolic subtype in 5 (14.3%) patients, and 3 (8.6%) patients had had a transient ischemic attack.
Results. Perfusion computed tomography is a method that allowed evaluation of the structure of the brain, and blood supply to the anterior cerebral (in 2.9% of the studied patients), middle cerebral (in 62.9% of the studied patients), posterior cerebral (in 11.4% of the studied patients) and vertebral (in 14.2% of the studied patients) arteries of patients with a stroke. The method revealed a zone of critical perfusion (ischemic penumbra) by quantitatively processing perfusion indicators in the anterior cerebral blood flow system (decrease in rate and increase in average volume of cerebral blood flow and average transit time) and in the posterior cerebral circulation system (decrease in blood flow and prolongation of transit time) in the bed of the right vertebral artery). The method also aided the construction of perfusion maps. Transcranial Doppler ultrasonography of cerebral vessels revealed breaches in the cerebral circulation: a decrease in the linear velocity of blood flow in the right middle cerebral arterial bed and in the posterior circulatory system of blood flow in the brain, and an increase in the pulsatility index in all the studied vascular beds.
Conclusion. Perfusion computed tomography of the brain in combination with transcranial Doppler ultrasonography is applicable to patients with stroke in various vascular beds, followed by determination of indications for thrombolytic therapy and thrombectomy.
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Peretz, Shlomi, David Orion, David Last, Yael Mardor, Yotam Kimmel, Shelly Yehezkely, Eyal Lotan, et al. "Incorporation of relative cerebral blood flow into CT perfusion maps reduces false ’at risk' penumbra." Journal of NeuroInterventional Surgery 10, no. 7 (September 30, 2017): 657–62. http://dx.doi.org/10.1136/neurintsurg-2017-013268.
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PurposeThe region defined as ‘at risk’ penumbra by current CT perfusion (CTP) maps is largely overestimated. We aimed to quantitate the portion of true ‘at risk’ tissue within CTP penumbra and to determine the parameter and threshold that would optimally distinguish it from false ‘at risk’ tissue, that is, benign oligaemia.MethodsAmong acute stroke patients evaluated by multimodal CT (NCCT/CTA/CTP) we identified those that had not undergone endovascular/thrombolytic treatment and had follow-up NCCT. Maps of absolute and relative CBF, CBV, MTT, TTP and Tmax as well as summary maps depicting infarcted and penumbral regions were generated using the Intellispace Portal (Philips Healthcare, Best, Netherlands). Follow-up CT was automatically co-registered to the CTP scan and the final infarct region was manually outlined. Perfusion parameters were systematically analysed – the parameter that resulted in the highest true-negative-rate (ie, proportion of benign oligaemia correctly identified) at a fixed, clinically relevant false-negative-rate (ie, proportion of ‘missed’ infarct) of 15%, was chosen as optimal. It was then re-applied to the CTP data to produce corrected perfusion maps.ResultsForty seven acute stroke patients met selection criteria. Average portion of infarcted tissue within CTP penumbra was 15%±2.2%. Relative CBF at a threshold of 0.65 yielded the highest average true-negative-rate (48%), enabling reduction of the false ‘at risk’ penumbral region by ~half.ConclusionsApplying a relative CBF threshold on relative MTT-based CTP maps can significantly reduce false ‘at risk’ penumbra. This step may help to avoid unnecessary endovascular interventions.
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Okell, Thomas W., Michael A. Chappell, Michael E. Kelly, and Peter Jezzard. "Cerebral Blood Flow Quantification Using Vessel-Encoded Arterial Spin Labeling." Journal of Cerebral Blood Flow & Metabolism 33, no. 11 (August 7, 2013): 1716–24. http://dx.doi.org/10.1038/jcbfm.2013.129.
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Arterial spin labeling (ASL) techniques are gaining popularity for visualizing and quantifying cerebral blood flow (CBF) in a range of patient groups. However, most ASL methods lack vessel-selective information, which is important for the assessment of collateral flow and the arterial supply to lesions. In this study, we explored the use of vessel-encoded pseudocontinuous ASL (VEPCASL) with multiple postlabeling delays to obtain individual quantitative CBF and bolus arrival time maps for each of the four main brain-feeding arteries and compared the results against those obtained with conventional pseudocontinuous ASL (PCASL) using matched scan time. Simulations showed that PCASL systematically underestimated CBF by up to 37% in voxels supplied by two arteries, whereas VEPCASL maintained CBF accuracy since each vascular component is treated separately. Experimental results in healthy volunteers showed that there is no systematic bias in the CBF estimates produced by VEPCASL and that the signal-to-noise ratio of the two techniques is comparable. Although more complex acquisition and image processing is required and the potential for motion sensitivity is increased, VEPCASL provides comparable data to PCASL but with the added benefit of vessel-selective information. This could lead to more accurate CBF estimates in patients with a significant collateral flow.
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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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Frey, K. A., S. Minoshima, R. A. Koeppe, M. R. Kilbourn, K. L. Berger, and D. E. Kuhl. "Stereotaxic Summation Analysis of Human Cerebral Benzodiazepine Binding Maps." Journal of Cerebral Blood Flow & Metabolism 16, no. 3 (May 1996): 409–17. http://dx.doi.org/10.1097/00004647-199605000-00007.
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Summation analysis strategies are recognized throughout diverse scientific fields as powerful means of differentially enhancing experimental signals over random fluctuations (noise). Such techniques, applied to emission tomographic cerebral blood flow scans, reveal subtle alterations in neuronal activity during specific behavioral states. In the present work, we extend the principles of intersubject image summation analysis to the evaluation of emission tomographic ligand-binding studies. A general methodology is presented that may be applied to a wide variety of binding site determinations. The procedure consists of anatomic standardization of individual brains to a common stereotaxic orientation, followed by statistical analyses of group versus group or individual versus group differences. We develop and evaluate performance of our technique with the use of positron emission tomographic [11C]flumazenil scans from normal volunteers, depicting the regional cerebral distribution of benzodiazepine binding sites.
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Singer, Oliver C., Richard du Mesnil de Rochemont, Christian Foerch, Astrid Stengel, Heiner Lanfermann, Matthias Sitzer, and Tobias Neumann-Haefelin. "Relation between Relative Cerebral Blood Flow, Relative Cerebral Blood Volume, and Mean Transit Time in Patients with Acute Ischemic Stroke Determined by Perfusion-Weighted MRI." Journal of Cerebral Blood Flow & Metabolism 23, no. 5 (May 2003): 605–11. http://dx.doi.org/10.1097/01.wcb.0000062342.57257.28.
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The relation between relative cerebral blood flow (relCBF), relative cerebral blood volume (relCBV), and mean transit time (MTT) changes was examined in 20 patients with acute cerebral ischemia (<6 h) using perfusion-weighted magnetic resonance imaging. Regions of interest (ROI) were selected on MTT maps covering the entire MTT abnormal cortical area. These ROIs were transferred to the relCBF and relCBV maps to analyze the relation between relCBF, relCBV, and MTT on a voxel-by-voxel basis. On the unaffected side, a tight coupling of relCBF and relCBV was found with little variation of MTT. In hypoperfused cortex, relCBV was increased at all investigated relCBF categories, and there was greater relCBV variability than on the unaffected side. Only a severe decrease of relCBF, to less than 0.3, in comparison with the unaffected side was associated with a reduction of relCBV less than 1.0. In contrast to the unaffected side, a power law function (relCBV = 2.283 × relCBF0.549) resulted in a better fit than using a linear function for the correlation of relCBF and relCBV. MTT ratios increased steadily with decreasing CBF values. In conclusion, there is a clear relation between different perfusion-weighted magnetic resonance imaging parameters in acute ischemia, reflecting both the degree of hemodynamic failure as well as compensatory mechanisms including vasodilation.
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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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Andersson, JLR, C. Muhr, A. Lilja, S. Valind, PO Lundberg, and B. Långström. "Regional Cerebral Blood Flow and Oxygen Metabolism during Migraine with and Without Aura." Cephalalgia 17, no. 5 (August 1997): 570–79. http://dx.doi.org/10.1046/j.1468-2982.1997.1705570.x.
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Eleven cases of migraine with and without aura were investigated with positron emission tomography (PET). Regional cerebral blood flow (rCBF), oxygen metabolism (rCMRO2) and oxygen extraction (rOER) were measured during baseline ( n = 11), aura ( n = 6), headache ( n = 10) and after treatment with sumatriptan ( n = 4). Data were analysed using and ROI-based approach from 26 different anatomically defined regions, and also an exploratory approach whereby all subjects were normalized to a stereotactic brain atlas; t-maps were constructed by depicting significant changes between states. The exploratory approach revealed a region corresponding to the primary visual cortex with significant reductions in rCBF (23.1%) and rCMRO2 (22.5%), but no change in rOER during the headache phase compared to baseline. These data suggest that cerebral ischemia was not the primary cause of the attacks in these cases.
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Liu, Qian, Zheng Wang, and Qingming Luo. "Temporal clustering analysis of cerebral blood flow activation maps measured by laser speckle contrast imaging." Journal of Biomedical Optics 10, no. 2 (2005): 024019. http://dx.doi.org/10.1117/1.1891105.
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Kamran, Mudassar, Jonathan Downer, Rufus Corkill, and James V. Byrne. "Non-invasive assessment of vasospasm following aneurysmal SAH using C-arm FDCT parenchymal blood volume measurement in the neuro-interventional suite: Technical feasibility." Interventional Neuroradiology 21, no. 4 (May 27, 2015): 479–89. http://dx.doi.org/10.1177/1591019915582376.
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Introduction Cerebral vasospasm is the leading cause of morbidity and mortality in patients with aneurysmal subarachnoid haemorrhage (SAH) surviving the initial ictus. Commonly used techniques for vasospasm assessment are digital subtraction angiography and transcranial Doppler sonography. These techniques can reliably identify only the major vessel spasm and fail to estimate its haemodynamic significance. To overcome these issues and to enable comprehensive non-invasive assessment of vasospasm inside the interventional suite, a novel protocol involving measurement of parenchymal blood volume (PBV) using C-arm flat detector computed tomography (FDCT) was implemented. Materials and methods Patients from the neuro-intensive treatment unit (ITU) with suspected vasospasm following aneurysmal SAH were scanned with a biplane C-arm angiography system using an intravenous contrast injection protocol. The PBV maps were generated using prototype software. Contemporaneous clinically indicated MR scan including the diffusion- and perfusion-weighted sequences was performed. C-arm PBV maps were compared against the MR perfusion maps. Results Distribution of haemodynamic impairment on C-arm PBV maps closely matched the pattern of abnormality on MR perfusion maps. On visual comparison between the two techniques, the extent of abnormality indicated PBV to be both cerebral blood flow and cerebral blood volume weighted. Conclusion C-arm FDCT PBV measurements allow an objective assessment of the severity and localisation of cerebral hypoperfusion resulting from vasospasm. The technique has proved feasible and useful in very sick patients after aneurysmal SAH. The promise shown in this early study indicates that it deserves further evaluation both for post-SAH vasospasm and in other relevant clinical settings.
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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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Campbell, Bruce C. V., Søren Christensen, Christopher R. Levi, Patricia M. Desmond, Geoffrey A. Donnan, Stephen M. Davis, and Mark W. Parsons. "Cerebral Blood Flow Is the Optimal CT Perfusion Parameter for Assessing Infarct Core." Stroke 42, no. 12 (December 2011): 3435–40. http://dx.doi.org/10.1161/strokeaha.111.618355.
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Background and Purpose— CT perfusion (CTP) is widely and rapidly accessible for imaging acute ischemic stroke but has limited validation. Cerebral blood volume (CBV) has been proposed as the best predictor of infarct core. We tested CBV against other common CTP parameters using contemporaneous diffusion MRI. Methods— Patients with acute ischemic stroke <6 hours after onset had CTP and diffusion MRI <1 hour apart, before any reperfusion therapies. CTP maps of time to peak (TTP), absolute and relative CBV, cerebral blood flow (CBF), mean transit time (MTT), and time to peak of the deconvolved tissue residue function (Tmax) were generated. The diffusion lesion was manually outlined to its maximal visual extent. Receiver operating characteristic (ROC) analysis area under the curve (AUC) was used to quantify the correspondence of each perfusion parameter to the coregistered diffusion-weighted imaging lesion. Optimal thresholds were determined (Youden index). Results— In analysis of 98 CTP slabs (54 patients, median onset to CT 190 minutes, median CT to MR 30 minutes), relative CBF performed best (AUC, 0.79; 95% CI, 0.77–81), significantly better than absolute CBV (AUC, 0.74; 95% CI, 0.73–0.76). The optimal threshold was <31% of mean contralateral CBF. Specificity was reduced by low CBF/CBV in noninfarcted white matter in cases with reduced contrast bolus intensity and leukoaraiosis. Conclusions— In contrast to previous reports, CBF corresponded with the acute diffusion-weighted imaging lesion better than CBV, although no single threshold avoids detection of false-positive regions in unaffected white matter. This relates to low signal-to-noise ratio in CTP maps and emphasizes the need for optimized acquisition and postprocessing.
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Liu, Yawu, Jari O. Karonen, Ritva L. Vanninen, Leif Østergaard, Reina Roivainen, Juho Nuutinen, Jussi Perkio, et al. "Cerebral Hemodynamics in Human Acute Ischemic Stroke: A Study with Diffusion- and Perfusion-Weighted Magnetic Resonance Imaging and SPECT." Journal of Cerebral Blood Flow & Metabolism 20, no. 6 (June 2000): 910–20. http://dx.doi.org/10.1097/00004647-200006000-00003.
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Nineteen patients with acute ischemic stroke (<24 hours) underwent diffusion-weighted and perfusion-weighted (PWI) magnetic resonance imaging at the acute stage and 1 week later. Eleven patients also underwent technetium-99m ethyl cysteinate dimer single-photon emission computed tomography (SPECT) at the acute stage. Relative (ischemic vs. contralateral control) cerebral blood flow (relCBF), relative cerebral blood volume, and relative mean transit time were measured in the ischemic core, in the area of infarct growth, and in the eventually viable ischemic tissue on PWI maps. The relCBF was also measured from SPECT. There was a curvilinear relationship between the relCBF measured from PWI and SPECT ( r = 0.854; P < 0.001). The tissue proceeding to infarction during the follow-up had significantly lower initial CBF and cerebral blood volume values on PWI maps ( P < 0.001) than the eventually viable ischemic tissue had. The best value for discriminating the area of infarct growth from the eventually viable ischemic tissue was 48% for PWI relCBF and 87% for PWI relative cerebral blood volume. Combined diffusion and perfusion-weighted imaging enables one to detect hemodynamically different subregions inside the initial perfusion abnormality. Tissue survival may be different in these subregions and may be predicted.
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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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Mendrik, Adriënne M., Evert-jan Vonken, Bram van Ginneken, Hugo W. de Jong, Alan Riordan, Tom van Seeters, Ewoud J. Smit, Max A. Viergever, and Mathias Prokop. "TIPS bilateral noise reduction in 4D CT perfusion scans produces high-quality cerebral blood flow maps." Physics in Medicine and Biology 56, no. 13 (June 8, 2011): 3857–72. http://dx.doi.org/10.1088/0031-9155/56/13/008.
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Gioia, Laura C., Mahesh Kate, Rebecca McCourt, Bronwen Gould, Shelagh B. Coutts, Dariush Dowlatshahi, Negar Asdaghi, et al. "Perihematoma Cerebral Blood Flow is Unaffected by Statin Use in Acute Intracerebral Hemorrhage Patients." Journal of Cerebral Blood Flow & Metabolism 35, no. 7 (March 11, 2015): 1175–80. http://dx.doi.org/10.1038/jcbfm.2015.36.
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Statin therapy has been associated with improved cerebral blood flow (CBF) and decreased perihematoma edema in animal models of intracerebral hemorrhage (ICH). We aimed to assess the relationship between statin use and cerebral hemodynamics in ICH patients. A post hoc analysis of 73 ICH patients enrolled in the Intracerebral Hemorrhage Acutely Decreasing Arterial Pressure Trial (ICH ADAPT). Patients presenting < 24 hours from ICH onset were randomized to a systolic blood pressure target < 150 or < 180 mm Hg with computed tomography perfusion imaging 2 hours after randomization. Cerebral blood flow maps were calculated. Hematoma and edema volumes were measured planimetrically. Regression models were used to assess the relationship between statin use, perihematoma edema and cerebral hemodynamics. Fourteen patients (19%) were taking statins at the time of ICH. Statin-treated patients had similar median (IQR Q25 to 75) hematoma volumes (21.1 (9.5 to 38.3) mL versus 14.5 (5.6 to 27.7) mL, P = 0.25), but larger median (IQR Q25 to 75) perihematoma edema volumes (2.9 (1.7 to 9.0) mL versus 2.2 (0.8 to 3.5) mL, P = 0.02) compared with nontreated patients. Perihematoma and ipsilateral hemispheric CBF were similar in both groups. A multivariate linear regression model revealed that statin use and hematoma volumes were independent predictors of acute edema volumes. Statin use does not affect CBF in ICH patients. Statin use, along with hematoma volume, are independently associated with increased perihematoma edema volume.
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Bench, Christopher J., Karl J. Friston, Richard G. Brown, Lynette C. Scott, Richard S. J. Frackowiak, and Raymond J. Dolan. "The anatomy of melancholia – focal abnormalities of cerebral blood flow in major depression." Psychological Medicine 22, no. 3 (August 1992): 607–15. http://dx.doi.org/10.1017/s003329170003806x.
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SynopsisUsing positron emission tomography (PET) and 15Oxygen, regional cerebral blood flow (rCBF) was measured in 33 patients with primary depression, 10 of whom had an associated severe cognitive impairment, and 23 age-matched controls. PET scans from these groups were analysed on a pixel-by-pixel basis and significant differences between the groups were identified on Statistical Parametric Maps (SPMs). In the depressed group as a whole rCBF was decreased in the left anterior cingulate and the left dorsolateral prefrontal cortex (P < 0·05 Bonferroni-corrected for multiple comparisons). Comparing patients with and without depression-related cognitive impairment, in the impaired group there were significant decreases in rCBF in the left medial frontal gyrus and increased rCBF in the cerebellar vermis (P < 0·05 Bonferroni-corrected). Therefore an anatomical dissociation has been described between the rCBF profiles associated with depressed mood and depression-related cognitive impairment. The pre-frontal and limbic areas identified in this study constitute a distributed anatomical network that may be functionally abnormal in major depressive disorder.
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Fujita, Hitoshi, Ernst Meyer, David C. Reutens, Hiroto Kuwabara, Alan C. Evans, and Albert Gjedde. "Cerebral [15O] Water Clearance in Humans Determined by Positron Emission Tomography: II. Vascular Responses to Vibrotactile Stimulation." Journal of Cerebral Blood Flow & Metabolism 17, no. 1 (January 1997): 73–79. http://dx.doi.org/10.1097/00004647-199701000-00010.
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When used to measure blood flow, water leaves a residue in the vascular bed, which may contribute to the calculation of increased blood flow during functional activation of brain tissue. To assess the magnitude of this contribution with the two-compartment positron emission tomography (PET) method, we mapped the water clearance ( K1) of the brain as an index of cerebral blood flow (CBF) and the apparent vascular distribution of nonextracted H215O ( Vo). The latter map represented mainly the cerebral arterial and arteriolar volume. We also prepared subtraction maps (Δ K1, Δ Vo) of the response to vibrotactile stimulation of the fingertips of the right hand of six normal volunteers. Using magnetic resonance (MR) images of all subjects, the data were rendered into Talairach's stereotaxic coordinates and the averaged subtraction images (activation minus baseline) merged with the corresponding averaged MRI image. The Δ K1 map revealed the expected response in the primary sensory hand area; the Δ Vo response was located about 13 mm more anteriorly, close to the central fissure, most likely reflecting changes of the arteries feeding the primary sensory hand area. We conclude that cerebral perfusion and cerebrovascular responses to vibrotactile stimulation may occur in disparate locations that can be identified separately by using the two-compartment method.
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Jandric, Danka, Ilona Lipp, David Paling, David Rog, Gloria Castellazzi, Hamied Haroon, Laura Parkes, Geoff J. M. Parker, Valentina Tomassini, and Nils Muhlert. "Mechanisms of Network Changes in Cognitive Impairment in Multiple Sclerosis." Neurology 97, no. 19 (October 14, 2021): e1886-e1897. http://dx.doi.org/10.1212/wnl.0000000000012834.
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Background and ObjectivesCognitive impairment in multiple sclerosis (MS) is associated with functional connectivity abnormalities. While there have been calls to use functional connectivity measures as biomarkers, there remains to be a full understanding of why they are affected in MS. In this cross-sectional study, we tested the hypothesis that functional network regions may be susceptible to disease-related “wear and tear” and that this can be observable on co-occurring abnormalities on other magnetic resonance metrics. We tested whether functional connectivity abnormalities in cognitively impaired patients with MS co-occur with (1) overlapping, (2) local, or (3) distal changes in anatomic connectivity and cerebral blood flow abnormalities.MethodsMultimodal 3T MRI and assessment with the Brief Repeatable Battery of Neuropsychological tests were performed in 102 patients with relapsing-remitting MS and 27 healthy controls. Patients with MS were classified as cognitively impaired if they scored ≥1.5 SDs below the control mean on ≥2 tests (n = 55) or as cognitively preserved (n = 47). Functional connectivity was assessed with Independent Component Analysis and dual regression of resting-state fMRI images. Cerebral blood flow maps were estimated, and anatomic connectivity was assessed with anatomic connectivity mapping and fractional anisotropy of diffusion-weighted MRI. Changes in cerebral blood flow and anatomic connectivity were assessed within resting-state networks that showed functional connectivity abnormalities in cognitively impaired patients with MS.ResultsFunctional connectivity was significantly decreased in the anterior and posterior default mode networks and significantly increased in the right and left frontoparietal networks in cognitively impaired relative to cognitively preserved patients with MS (threshold-free cluster enhancement corrected at p ≤ 0.05, 2 sided). Networks showing functional abnormalities showed altered cerebral blood flow and anatomic connectivity locally and distally but not in overlapping locations.DiscussionWe provide the first evidence that functional connectivity abnormalities are accompanied by local cerebral blood flow and structural connectivity abnormalities but also demonstrate that these effects do not occur in exactly the same location. Our findings suggest a possibly shared pathologic mechanism for altered functional connectivity in brain networks in MS.
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Lauritzen, Martin. "Relationship of Spikes, Synaptic Activity, and Local Changes of Cerebral Blood Flow." Journal of Cerebral Blood Flow & Metabolism 21, no. 12 (December 2001): 1367–83. http://dx.doi.org/10.1097/00004647-200112000-00001.
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The coupling of electrical activity in the brain to changes in cerebral blood flow (CBF) is of interest because hemodynamic changes are used to track brain function. Recent studies, especially those investigating the cerebellar cortex, have shown that the spike rate in the principal target cell of a brain region (i.e. the efferent cell) does not affect vascular response amplitude. Subthreshold integrative synaptic processes trigger changes in the local microcirculation and local glucose consumption. The spatial specificity of the vascular response on the brain surface is limited because of the functional anatomy of the pial vessels. Within the cortex there is a characteristic laminar flow distribution, the largest changes of which are observed at the depth of maximal synaptic activity (i.e. layer IV) for an afferent input system. Under most conditions, increases in CBF are explained by activity in postsynaptic neurons, but presynaptic elements can contribute. Neurotransmitters do not mediate increases in CBF that are triggered by the concerted action of several second messenger molecules. It is important to distinguish between effective synaptic inhibition and deactivation that increase and decrease CBF and glucose consumption, respectively. In summary, hemodynamic changes evoked by neuronal activity depend on the afferent input function (i.e. all aspects of presynaptic and postsynaptic processing), but are totally independent of the efferent function (i.e., the spike rate of the same region). Thus, it is not possible to conclude whether the output level of activity of a region is increased based on brain maps that use blood-flow changes as markers.
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Wang, Zheng, and Anna W. Roe. "Columnar Specificity of Microvascular Oxygenation and Blood Flow Response in Primary Visual Cortex: Evaluation by Local Field Potential and Spiking Activity." Journal of Cerebral Blood Flow & Metabolism 32, no. 1 (October 26, 2011): 6–16. http://dx.doi.org/10.1038/jcbfm.2011.152.
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The relation of cortical microcirculation, oxygen metabolism, and underlying neuronal network activity remains poorly understood. Anatomical distribution of cortical microvasculature and its relationship to cortical functional domains suggests that functional organizations may be revealed by mapping cerebral blood flow responses. However, there is little direct experimental evidence and a lack of electrophysiological evaluation. In this study, we mapped ocular-dominance columns in primary visual cortex (V1) of anesthetized macaques with capillary flow-based laser speckle contrast imaging and deoxyhemoglobin-based intrinsic optical imaging. In parallel, the local field potentials (LFPs) and spikes were recorded from a linear array of eight microelectrodes, carefully positioned into left and right eye columns in V1. We found differential activation maps of blood flow, after masking large superficial draining vessels, exhibited a column-like pattern similar as the oximetric maps. Both the activated spikes and γ-band LFP demonstrated corresponding eye preference, consistent with the imaging maps. Our results present direct support in favor of previous proposals that the regulation of microcirculation can be as fine as the submillimeter scale, suggesting that cortical vasculature is functionally organized at the columnar level in a manner appropriate for supplying energy demands of functionally specific neuronal populations.
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Thow, Lisa A., Kathleen MacDonald, William M. Holmes, Keith W. Muir, I. Mhairi Macrae, and Deborah Dewar. "Hyperglycaemia does not increase perfusion deficits after focal cerebral ischaemia in male Wistar rats." Brain and Neuroscience Advances 2 (January 2018): 239821281879482. http://dx.doi.org/10.1177/2398212818794820.
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Background: Hyperglycaemia is associated with a worse outcome in acute ischaemic stroke patients; yet the pathophysiological mechanisms of hyperglycaemia-induced damage are poorly understood. We hypothesised that hyperglycaemia at the time of stroke onset exacerbates ischaemic brain damage by increasing the severity of the blood flow deficit. Methods: Adult, male Wistar rats were randomly assigned to receive vehicle or glucose solutions prior to permanent middle cerebral artery occlusion. Cerebral blood flow was assessed semi-quantitatively either 1 h after middle cerebral artery occlusion using 99mTc-D, L-hexamethylpropyleneamine oxime (99mTc-HMPAO) autoradiography or, in a separate study, using quantitative pseudo-continuous arterial spin labelling for 4 h after middle cerebral artery occlusion. Diffusion weighted imaging was performed alongside pseudo-continuous arterial spin labelling and acute lesion volumes calculated from apparent diffusion coefficient maps. Infarct volume was measured at 24 h using rapid acquisition with refocused echoes T2-weighted magnetic resonance imaging. Results: Glucose administration had no effect on the severity of ischaemia when assessed by either 99mTc-HMPAO autoradiography or pseudo-continuous arterial spin labelling perfusion imaging. In comparison to the vehicle group, apparent diffusion coefficient–derived lesion volume 2–4 h post-middle cerebral artery occlusion and infarct volume 24 h post-middle cerebral artery occlusion were significantly greater in the glucose group. Conclusions: Hyperglycaemia increased acute lesion and infarct volumes but there was no evidence that the acute blood flow deficit was exacerbated. The data reinforce the conclusion that the detrimental effects of hyperglycaemia are rapid, and that treatment of post-stroke hyperglycaemia in the acute period is essential but the mechanisms of hyperglycaemia-induced harm remain unclear.
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Pandey, Pawan Kumar, Chandan Paul, Malay K. Das, and Krishnamurthy Muralidhar. "Assessment and visualization of hemodynamic loading in aneurysm sac and neck: Effect of foam insertion." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 235, no. 8 (May 10, 2021): 927–39. http://dx.doi.org/10.1177/09544119211015569.
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Shape memory polymer (SMP) foam is often proposed as the future alternative of coils in aneurysm treatment devices. Present work numerically investigates the unsteady, three-dimensional simulation of blood flow in a cerebral aneurysm filled with SMP foam. Simulations are conducted on patient-specific geometries with realistic blood velocity waveform imposed at the inlet while SMP foam is treated as a porous medium. The present study introduces a “loading risk map” that helps to visualize the hemodynamic effect of foam insertion on the aneurysm sac and neck. The loading risk maps suggest that while the SMP foam subdues the flow and wall shear pulsations in the aneurysm sac, the pressure distribution is minimally affected. The maps suggest that while the downstream lip is the most risk-prone site for both geometries, downstream vascular anatomy significantly influences foam efficiency in reducing pressure and wall shear stress loading.
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Kew, J. J., M. C. Ridding, J. C. Rothwell, R. E. Passingham, P. N. Leigh, S. Sooriakumaran, R. S. Frackowiak, and D. J. Brooks. "Reorganization of cortical blood flow and transcranial magnetic stimulation maps in human subjects after upper limb amputation." Journal of Neurophysiology 72, no. 5 (November 1, 1994): 2517–24. http://dx.doi.org/10.1152/jn.1994.72.5.2517.
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1. Two complimentary techniques were used to study cortical function in six human upper limb amputees: positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) were made in subjects during limb movements to study activation of the primary motor (M1), primary somatosensory (S1), and association cortices; and electromyographic responses to transcranial magnetic stimulation (TMS) were measured in proximal upper limb muscles to assess the excitability of corticospinal neurons in subjects at rest. 2. To explore possible cortical mechanisms governing the phantom limb phenomenon, PET and TMS findings were compared between subjects with acquired, traumatic upper limb amputations (n = 3), in whom phantom limb symptoms were prominent, and congenital upper limb amputees (n = 3) without phantom limbs. 3. Paced shoulder movements were associated with significant blood flow increases in the contralateral M1/S1 cortex of both groups of amputees. In traumatic amputees, these increases were present over a wider area and were of significantly greater magnitude in the partially deafferented cortex contralateral to the amputation. In congenital amputees blood flow increases were also present over a wider area in the partially deafferented M1/S1 cortex, but their magnitude was not significantly different from that in the normally afferented M1/S1 cortex. 4. Abnormal blood flow increases also were present in the partially deafferented M1/S1 cortex of traumatic amputees during movement of the ipsilateral, intact arm. Abnormal ipsilateral M1/S1 responses were not present during movement of the intact arm in the congenital group. 5. TMS studies showed that the abnormal blood flow increases in the partially deafferented M1 cortex of traumatic amputees were associated with increased corticospinal excitability.(ABSTRACT TRUNCATED AT 250 WORDS)
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Schreiber, Wolfgang G., Friedemann Gückel, Peter Stritzke, Peter Schmiedek, Andreas Schwartz, and Gunnar Brix. "Cerebral Blood Flow and Cerebrovascular Reserve Capacity: Estimation by Dynamic Magnetic Resonance Imaging." Journal of Cerebral Blood Flow & Metabolism 18, no. 10 (October 1998): 1143–56. http://dx.doi.org/10.1097/00004647-199810000-00011.
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We have developed a new method for estimation of regional CBF (rCBF) and cerebrovascular reserve capacity on a pixel-by-pixel basis by means of dynamic magnetic resonance imaging (MRI). Thirteen healthy volunteers, 8 patients with occlusion and/or high grade stenosis of the internal carotid artery (ICA), and 2 patients with acute stroke underwent dynamic susceptibility-weighted contrast enhanced MRI. Using principles of indicator dilution theory and deconvolution analysis, maps of rCBF, regional cerebral blood volume, and of the mean transit time (MTT) were calculated. In patients with ICA occlusion/stenosis, cerebrovascular reserve capacity was assessed by the rCBF increase after acetazolamide stimulation. Mean gray and white matter rCBF values in normals were 67.1 and 23.7 mL · 100 g−1 · min−1, respectively. Before acetazolamide stimulation, six of eight patients with ICA occlusions showed decreased rCBF values; and in seven patients increased MTT values were observed in tissue ipsilateral to the occlusion. After acetazolamide stimulation, decreased cerebrovascular reserve capacity was observed in five of eight patients with ICA occlusion. In acute stroke, rCBF in the central core of ischemia was less than 8 mL · 100 g−1 · min−1. In peri-infarct tissue, rCBF and MTT were higher than in unaffected tissue but rCBF was normal. Dynamic MRI provides important clinical information on the hemodynamic state of brain tissue in patients with occlusive cerebrovascular disease or acute stroke.
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Zarei, Mehrdad, Mohammad Ali Ansari, and Kourosh Zare. "The Temporal Confounding Effects of Extra-cerebral Contamination Factors on the Hemodynamic Signal Measured by Functional Near-Infrared Spectroscopy." Journal of Lasers in Medical Sciences 10, no. 5 (December 1, 2019): S73—S81. http://dx.doi.org/10.15171/jlms.2019.s14.
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Introduction: Functional near-infrared spectroscopy (fNIRS) has been broadly applied for optical brain imaging. This method is hemodynamic-based functional brain imaging relying on the measurement of the neurovascular coupling to detect changes in cerebral neuronal activities. The extra-cerebral hemodynamic changes are important contaminating factors in fNIRS measurements. This error signal can be misinterpreted as cerebral activities during fNIRS studies. Recently, it was assumed that temporal changes in deoxygenated hemoglobin concentration [HHb] was hardly affected by superficial blood flow, and it was proposed that the activation maps could be determined from [HHb] at large source-detector separation. Methods: In the current study, we measured the temporal changes in [HHb] using a continueswave fNIRS device at large source-detector separation, while superficial blood flow was stimulated by infrared lasers. A mesh-based Monte Carlo code was applied to estimate fNIRS sensitivity to superficial hemodynamic changes in a realistic 3D MRI-based brain phantom. Results: First, we simulated photon migration in a four-layered human-head slab model to calculate PPLs and fNIRS sensitivity. Then, the localization of the infrared laser inside a realistic brain model was studied using the Monte Carlo method. Finally, the changes in [HHb] over the prefrontal cortex of six adult males were measured by fNIRS at a source-detector separation of 3 cm. The results demonstrated that the relation between fNIRS sensitivity and an increase in S-D separation was nonlinear and a correlation between shallow and deep signals was observed. Conclusion: The presented results demonstrated that the temporal changes in the superficial blood flow could strongly affect HHb measurement at large source-detector separation. Hence, the cerebral activity map extracted from the [HHb] signal was mainly contaminated by superficial blood flow.
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Sainbhi, Amanjyot Singh, Nuray Vakitbilir, Alwyn Gomez, Kevin Y. Stein, Logan Froese, and Frederick A. Zeiler. "Non-Invasive Mapping of Cerebral Autoregulation Using Near-Infrared Spectroscopy: A Study Protocol." Methods and Protocols 6, no. 3 (June 9, 2023): 58. http://dx.doi.org/10.3390/mps6030058.
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The ability of cerebral vessels to maintain a fairly constant cerebral blood flow is referred to as cerebral autoregulation (CA). Using near-infrared spectroscopy (NIRS) paired with arterial blood pressure (ABP) monitoring, continuous CA can be assessed non-invasively. Recent advances in NIRS technology can help improve the understanding of continuously assessed CA in humans with high spatial and temporal resolutions. We describe a study protocol for creating a new wearable and portable imaging system that derives CA maps of the entire brain with high sampling rates at each point. The first objective is to evaluate the CA mapping system’s performance during various perturbations using a block-trial design in 50 healthy volunteers. The second objective is to explore the impact of age and sex on regional disparities in CA using static recording and perturbation testing in 200 healthy volunteers. Using entirely non-invasive NIRS and ABP systems, we hope to prove the feasibility of deriving CA maps of the entire brain with high spatial and temporal resolutions. The development of this imaging system could potentially revolutionize the way we monitor brain physiology in humans since it would allow for an entirely non-invasive continuous assessment of regional differences in CA and improve our understanding of the impact of the aging process on cerebral vessel function.
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Langner, Soenke, Steffen Fleck, Rebecca Seipel, Henry W. S. Schroeder, Norbert Hosten, and Michael Kirsch. "Perfusion CT scanning and CT angiography in the evaluation of extracranial-intracranial bypass grafts." Journal of Neurosurgery 114, no. 4 (April 2011): 978–83. http://dx.doi.org/10.3171/2010.6.jns10117.
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Object Extracranial-intracranial (EC-IC) bypass surgery remains an important treatment alternative for patients with occlusive cerebrovascular disease. The aim of the present study was to use perfusion CT and CT angiography (CTA) to evaluate cerebral hemodynamics and bypass patency in patients with occlusive cerebrovascular disease before and after EC-IC bypass surgery. Methods Ten patients underwent perfusion CT and CTA before and after bypass surgery. Preoperative and postoperative digital subtraction angiography served as the diagnostic gold standard. An artery bypass was established from the superficial temporal artery to a cortical branch of the middle cerebral artery. Perfusion CT scanning was performed at the level of the basal ganglia. Color-coded perfusion maps of cerebral blood volume, cerebral blood flow, and time to peak were calculated. Results Preoperative perfusion CT showed significant prolonged time to peak and reduced cerebral blood flow of the affected hemisphere. Postoperative neurological deterioration did not develop in any patient. Computed tomography angiography provided adequate evaluation of the anastomoses as well as the course and caliber of the bypass and confirmed bypass patency in all patients. Postoperative perfusion CT showed improved cerebral hemodynamics with a return to nearly normal perfusion parameters. Conclusions Computed tomography angiography is a noninvasive and reliable tool for evaluating patients with EC-IC bypass. Perfusion CT allows monitoring of hemodynamic changes after bypass surgery. The combination of both modalities enables noninvasive anatomical and functional analysis of superficial temporal artery–middle cerebral artery anastomoses using a single CT protocol. Hemodynamic evaluation of patients with occlusive cerebrovascular disease before and after surgery may improve the prediction of outcome and may help identify patients in whom a bypass procedure can be performed.
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Becker, James T., Wei Wang, Cyrus Raji, Weiying Dai, Michael Gach, and Oscar L. Lopez. "IC-P-066: Statistical properties of maps of regional cerebral blood flow generated by continuous arterial spin labeling." Alzheimer's & Dementia 5, no. 4S_Part_1 (July 2009): P31. http://dx.doi.org/10.1016/j.jalz.2009.05.620.
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Selvaggi, Pierluigi, Sameer Jauhar, Vasileia Kotoula, Fiona Pepper, Mattia Veronese, Barbara Santangelo, Fernando Zelaya, Federico Turkheimer, Mitul Mehta, and Oliver Howes. "M18. REDUCED CORTICAL CEREBRAL BLOOD FLOW IN FIRST EPISODE PSYCHOSIS PATIENTS." Schizophrenia Bulletin 46, Supplement_1 (April 2020): S140. http://dx.doi.org/10.1093/schbul/sbaa030.330.
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Abstract Background Abnormal Cerebral Blood Flow (CBF) has been found in patients with chronic schizophrenia (SCZ), first-episode psychosis patients (FEP) and individuals at clinical high-risk (CHR). In particular, previous studies using Arterial Spin Labelling (ASL) found that SCZ have a global reduction of CBF in the cortex and increased CBF in the basal ganglia, the hippocampus, and the amygdala as compared with controls. To date, only one study investigated CBF using ASL in a small cohort of medicated FEP reporting increased CBF in the striatum and reduced frontal CBF as compared with controls. However, it is still not clear whether these abnormalities are related to antipsychotic treatment or rather they reflect a disease state independent from medication. Critically, clinical and pre-clinical evidence suggests that antipsychotics increase CBF, especially in the basal ganglia through dopamine D2 receptors blockade. Here, we assessed CBF differences between FEP and controls in a larger cohort of unmedicated or minimally treated patients. In addition, we tested the association between CBF abnormalities and clinical features. Methods 26 FEP (13 medication-free, 9 antipsychotics naïve, 4 minimally treated) and 22 healthy controls (HC) were recruited. FEP and HC were matched for age and gender. Among FEP, 11 had a diagnosis of affective psychosis and 15 of non-affective psychosis. MRI scans were acquired using a GE MR750 3T scanner and a 12-channel head coil. ASL data was acquired using a pseudo-continuous ASL sequence (pCASL). Four control-label pairs were used. Quantification of the CBF data was made using a coil sensitivity map and a proton density image. CBF maps were normalized using non-linear registration and smoothed using a 6 mm full width at half maximum (FWHM) kernel. Grey matter CBF and regional CBF values in each Region of Interest (ROI) were extracted using individual grey matter images and WFU-Pickatlas ROIs with the MarsBar toolbox. Based on previous studies the following ROIs were selected: right and left hippocampus, right and left striatum, right and left frontal cortex. Whole-brain voxel-wise analysis was performed using a non-parametric independent t-test as implemented in FSL randomize (Threshold Free Cluster Enhancement, TFCE, and 5000 permutations). Bonferroni method was used to correct ROI analysis for multiple comparisons (alpha = 0.05, n = 7). Results Significantly reduced CBF was found in FEP as compared with controls in total grey matter CBF (p = 0.004). Whole-brain voxel-wise analysis FEP-HC comparison revealed a widespread cortical reduction in large cortical clusters that encompass the occipital, parietal and frontal cortices (pFWE TFCE corrected < 0.05). ROI analysis revealed a significant reduction in CBF in the right frontal cortex (p = 0.002). A nominal significant reduction was also detected in the left frontal cortex (p = 0.014). No statistically significant differences were found in the other ROI considered (all p > 0.1). Sub-analysis after removing minimally treated patients did not change the results. Both global grey matter CBF and right frontal CBF were reduced in both affective and non-affective psychosis as compared with controls (p < 0.05), whereas no differences were detected between the two clinical groups. Discussion Our results confirm earlier evidence on reduction of cortical perfusion in FEP. However, in contrast with previous studies, we did not detect any difference in striatal perfusion in our cohort of unmedicated/minimally treated patients. Hence, our results support the hypothesis that alteration in striatal perfusion are likely due to medication. Finally, our results suggest that CBF alterations might have a trans-diagnostic role in the pathophysiology of psychosis.
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Xu, Lei, Sati Mazumdar, Philip J. Greer, and Julie Price. "Stimulant-Induced Spatial Temporal Patterns in Pet Data : Illustrations Using SPM, Manacova-CVA and PLS." Calcutta Statistical Association Bulletin 56, no. 1-4 (March 2005): 209–30. http://dx.doi.org/10.1177/0008068320050512.
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Summary Functional brain images arc extraordinarily rich data sets that reflect brain function such as cerebral blood flow. These images are widely applied to study brain activity after drug administration or in response to perceptual and cognitive stimuli. Positron Emission Tomography (PET) constitutes one important modality that provides functional brain images. Spatial and temporal patterns in brain activities captured from these images have helped to better understand brain dysfunction in disease and aid in diagnosis and treatment of diseases including ncurogenerative disorders. As PET provides maps consisting of average levels of activity for cuboidal voxels of tissue, it is a substantial analytic challenge to integrate the temporal, spatial and statistical signals making up these data. This paper presents a comparative analysis of three voxel-based methods for characterization of spatial-temporal patterns provided by PET images of cerebral blood flow . The methods are: (i) statistical parametric mapping (SPM) providing a voxel-wise brain map of a selected statistic; (ii) multivariate analysis of covariance jointly with canonical variate analysis (MANCOVA-CVA) identifying regions of the brain that are most responsible for global statistical significance; and (iii) partial least squares (PLS) that uses a path modeling technique with latent variables for dimension reduction. The methods are illustrated using data from sequential [Formula: see text] PET studies in baboons to examine whether amphetamine affects relative cerebral blood flow (rCBF) differentially over time and over different regions of brain. The results are found to be consistent across the three methods.
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Rasmussen, Mads, Niels Juul, Søren M. Christensen, Kristjana Y. Jónsdóttir, Carsten Gyldensted, Peter Vestergaard-Poulsen, Georg E. Cold, and Leif Østergaard. "Cerebral Blood Flow, Blood Volume, and Mean Transit Time Responses to Propofol and Indomethacin in Peritumor and Contralateral Brain Regions." Anesthesiology 112, no. 1 (January 1, 2010): 50–56. http://dx.doi.org/10.1097/aln.0b013e3181c38bd3.
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Background The regional cerebral blood flow (CBF) response to propofol and indomethacin may be abnormal in patients with brain tumors. First, the authors tested the hypothesis that during propofol anesthesia alone and combined with indomethacin, changes in CBF, cerebral blood volume (CBV), and plasma mean transit time (MTT) differ in the peritumoral tissue compared with the contralateral normal brain region. Second, the authors tested the hypothesis that CBF and CBV are reduced and MTT is prolonged, in both regions during propofol anesthesia and indomethacin administration compared with propofol alone. Methods The authors studied eight patients subjected to craniotomy under propofol-fentanyl anesthesia for supratentorial brain tumors. Magnetic resonance imaging, including perfusion- and diffusion-weighted and structural sequences, was performed (1) on the day before surgery, (2) before and (3) after administration of indomethacin in the propofol-fentanyl anesthetized patient, and (4) 2 days after surgery. Maps of CBF, CBV, and MTT were calculated. The regions of interest were peritumoral gray matter and opposite contralateral gray matter. Analysis of variance was used to analyze flow data. Results Propofol anesthesia was associated with a median 32% (range, 3-61%) and 47% (range, 17-67%) reduction in CBF in the peritumoral and contralateral regions, respectively.The interaction between intervention with propofol and indomethacin and region of interest was not significant for any flow modalities. Neither intervention nor region was significant for MTT, CBF, and CBV (P > 0.05). Conclusion The CBF, CBV, and MTT responses to propofol and indomethacin are not different in the peritumoral region compared with contralateral brain tissue. Indomethacin did not further influence regional CBF, CBV, and MTT during propofol anesthesia.
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VIDEBECH, P., B. RAVNKILDE, A. R. PEDERSEN, A. EGANDER, B. LANDBO, N. A. RASMUSSEN, F. ANDERSEN, H. STØDKILDE-JØRGENSEN, A. GJEDDE, and R. ROSENBERG. "The Danish PET/depression project: PET findings in patients with major depression." Psychological Medicine 31, no. 7 (October 2001): 1147–58. http://dx.doi.org/10.1017/s0033291701004469.
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Background. It is hypothesized from previous positron emission tomography (PET) studies of patients with major depression that dysfunction of regions of the limbic system and the frontal lobes in close connection with the basal ganglia is involved in the pathophysiology of major depression.Methods. By means of PET and 15O labelled radioactive water we determined an index of the neuronal activity by mapping the cerebral blood flow distribution of 42 unselected in-patients suffering from moderate to severe depression and 47 healthy controls controlling for age and gender. The PET maps were co-registered to magnetic resonance images of the anatomy of the brain.Results. The functions-of-interest analysis revealed significant gender differences in cerebral blood flow and changes in the relative distribution of the blood with increasing age. The patients had increased activity of the hippocampus and the cerebellum compared to the healthy controls when corrected for these confounders and the influence of antidepressant medication. Furthermore, data in the Danish Psychiatric Central Register showed that the patients studied were representative of the population of depressed patients admitted to the hospital during the study period.Conclusion. Our main finding is increased blood flow to the hippocampus, even when controlling for a number of confounders. This is in accordance with a rapidly expanding literature suggesting an important role for this structure in major depression.
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Schmid, Sophie, Dennis FR Heijtel, Henri JMM Mutsaerts, Ronald Boellaard, Adriaan A. Lammertsma, Aart J. Nederveen, and Matthias JP van Osch. "Comparison of Velocity- and Acceleration-Selective Arterial Spin Labeling with [15O]H2O Positron Emission Tomography." Journal of Cerebral Blood Flow & Metabolism 35, no. 8 (March 18, 2015): 1296–303. http://dx.doi.org/10.1038/jcbfm.2015.42.
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In the last decade spatially nonselective arterial spin labeling (SNS-ASL) methods such as velocity-selective ASL (VS-ASL) and acceleration-selective ASL have been introduced, which label spins based on their flow velocity or acceleration rather than spatial localization. Since labeling also occurs within the imaging plane, these methods suffer less from transit delay effects than traditional ASL methods. However, there is a need for validation of these techniques. In this study, a comparison was made between these SNS-ASL techniques with [15O]H2O positron emission tomography (PET), which is regarded as gold standard to measure quantitatively cerebral blood flow (CBF) in humans. In addition, the question of whether these techniques suffered from sensitivity to arterial cerebral blood volume (aCBV), as opposed to producing pure CBF contrast, was investigated. The results show high voxelwise intracranial correlation (0.72 to 0.89) between the spatial distribution of the perfusion signal from the SNS-ASL methods and the PET CBF maps. A similar gray matter (GM) CBF was measured by dual VS-ASL compared with PET (46.7 ± 4.1 versus 47.1 ± 6.5 mL/100 g/min, respectively). Finally, only minor contribution of aCBV patterns in GM to all SNS-ASL methods was found compared with pseudo-continuous ASL. In conclusion, VS-ASL provides a similar quantitative CBF, and all SNS-ASL methods provide qualitatively similar CBF maps as [15O]H2O PET.
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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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Dake, Manmohi D., Matteo De Marco, Daniel J. Blackburn, Iain D. Wilkinson, Anne Remes, Yawu Liu, Maria Pikkarainen, Merja Hallikainen, Hilkka Soininen, and Annalena Venneri. "Obesity and Brain Vulnerability in Normal and Abnormal Aging: A Multimodal MRI Study." Journal of Alzheimer's Disease Reports 5, no. 1 (January 20, 2021): 65–77. http://dx.doi.org/10.3233/adr-200267.
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Background: How the relationship between obesity and MRI-defined neural properties varies across distinct stages of cognitive impairment due to Alzheimer’s disease is unclear. Objective: We used multimodal neuroimaging to clarify this relationship. Methods: Scans were acquired from 47 patients clinically diagnosed with mild Alzheimer’s disease dementia, 68 patients with mild cognitive impairment, and 57 cognitively healthy individuals. Voxel-wise associations were run between maps of gray matter volume, white matter integrity, and cerebral blood flow, and global/visceral obesity. Results: Negative associations were found in cognitively healthy individuals between obesity and white matter integrity and cerebral blood flow of temporo-parietal regions. In mild cognitive impairment, negative associations emerged in frontal, temporal, and brainstem regions. In mild dementia, a positive association was found between obesity and gray matter volume around the right temporoparietal junction. Conclusion: Obesity might contribute toward neural tissue vulnerability in cognitively healthy individuals and mild cognitive impairment, while a healthy weight in mild Alzheimer’s disease dementia could help preserve brain structure in the presence of age and disease-related weight loss.
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Zappe, Anne C., Josef Pfeuffer, Hellmut Merkle, Nikos K. Logothetis, and Jozien BM Goense. "The Effect of Labeling Parameters on Perfusion-Based fMRI in Nonhuman Primates." Journal of Cerebral Blood Flow & Metabolism 28, no. 3 (October 24, 2007): 640–52. http://dx.doi.org/10.1038/sj.jcbfm.9600564.
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The blood oxygenation level-dependent (BOLD) signal is the most commonly used modality of functional magnetic resonance imaging (fMRI) today. Although easy to implement, it is an ambiguous signal since it results from a combination of several hemodynamic factors. Functional cerebral blood flow changes, as measured by using arterial spin labeling (ASL), typically occur in the parenchyma and have been demonstrated to be more closely coupled to neural activation compared with BOLD. However, the intrinsically low signals from ASL techniques have hindered its widespread application to fMRI for basic research and even more so for clinical applications. Here, we report the first implementation of continuous ASL in the anaesthetized macaque at high magnetic field of 7T. The technique was optimized to permit maximum signal-to-noise ratio of functional perfusion-based images at high spatial resolution. The effect of labeling parameters, such as label time and post-label delay ( PLD), on functional cerebral blood flow (fCBF) in the visual cortex was evaluated. Functional cerebral blood flow maps did not change with increasing label time after 2,000 ms, indicating that a label time of 2,000 ms is sufficient for reliable mapping of fCBF. The percent changes obtained using fCBF were better localized to gray matter, than those obtained with BOLD. A short PLD of 200 ms revealed significantly higher fCBF changes at the cortical surface, indicating large-vessel contamination, than a long PLD of 800 ms. However, the effect of the PLD on fCBF was smaller than on baseline CBF. These results are of importance for high-resolution applications, and when accurate quantification is required for studies in monkeys as well as in humans.
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Hara, Shoko, Masaaki Hori, Ryo Ueda, Akifumi Hagiwara, Shihori Hayashi, Motoki Inaji, Yoji Tanaka, et al. "Intravoxel incoherent motion perfusion in patients with Moyamoya disease: comparison with 15O-gas positron emission tomography." Acta Radiologica Open 8, no. 5 (May 2019): 205846011984658. http://dx.doi.org/10.1177/2058460119846587.
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Background Intravoxel incoherent motion magnetic resonance imaging (IVIM) enables non-invasive measurement of brain perfusion. Purpose To investigate whether IVIM could be used to evaluate the hemodynamic disturbance of Moyamoya disease (MMD) by comparison with the gold-standard 15O-gas positron emission tomography (PET) method. Material and Methods Ten consecutive patients with MMD (six women; mean age = 42.8 years) and 10 age-matched healthy controls were evaluated by diffusion-weighted images with 12 different b values in the range of 0–900 s/mm2 and 15O-gas PET. Tomographic maps of IVIM parameters, perfusion fraction ( f ), pseudo-diffusion coefficient ( D*), and f・D*, as well as cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps obtained with PET, were normalized and hemispheric gray and white matter values were calculated. IVIM parametric values were compared with PET parameters and with clinically assessed disease severity. Results There was significant correlation between D* and MTT ( r = –0.74, P < 0.001) and between f・D* and CBF ( r = 0.52, P = 0.02) in the cortical areas. The f values in the white matter were significantly higher in symptomatic MMD patients than in healthy controls ( P = 0.01). Conclusion IVIM may be used to non-invasively investigate cerebral hemodynamic impairment in patients with MMD. Further evaluation is needed to establish IVIM usage in clinical settings.
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Khalili-Mahani, Najmeh, Matthias JP van Osch, Evelinda Baerends, Roelof P. Soeter, Marieke de Kam, Remco WM Zoethout, Albert Dahan, Mark A. van Buchem, Joop MA van Gerven, and Serge ARB Rombouts. "Pseudocontinuous Arterial Spin Labeling Reveals Dissociable Effects of Morphine and Alcohol on Regional Cerebral Blood Flow." Journal of Cerebral Blood Flow & Metabolism 31, no. 5 (January 19, 2011): 1321–33. http://dx.doi.org/10.1038/jcbfm.2010.234.
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We have examined sensitivity and specificity of pseudocontinuous arterial spin labeling (PCASL) to detect global and regional changes in cerebral blood flow (CBF) in response to two different psychoactive drugs. We tested alcohol and morphine in a placebo-controlled, double-blind randomized study in 12 healthy young men. Drugs were administered intravenously. Validated pharmacokinetic protocols achieved minimal intersubject and intrasubject variance in plasma drug concentration. Permutation-based statistical testing of a mixed effect repeated measures model revealed a widespread increase in absolute CBF because of both morphine and alcohol. Conjunction analysis revealed overlapping effects of morphine and alcohol on absolute CBF in the left anterior cingulate, right hippocampus, right insula, and left primary sensorimotor areas. Effects of morphine and alcohol on relative CBF (obtained from z-normalization of absolute CBF maps) were significantly different in the left putamen, left frontoparietal network, cerebellum, and the brainstem. Corroborating previous PET results, our findings suggest that PCASL is a promising tool for central nervous system drug research.