Arterial Blood Volume Research Articles

Perfusion Computed Tomography for Assessing Pancreas Graft Volumetric Perfusion After Simultaneous Pancreas and Kidney Transplantation

Background: There is paucity of data in the available medical literature regarding the parameters of the volumetric perfusion of pancreas grafts. Methods: From 5 February 2016 to 23 December 2021, we performed perfusion computed tomography in 41 patients at different times after simultaneous pancreas and kidney transplantation. The study group consisted of 18 men (44%) and 23 women (56%) with a long history of type 1 diabetes mellitus complicated by terminal chronic renal failure. The results of the perfusion computed tomography of the pancreas graft were studied, and the effects of post-transplantation timing and graft revascularization peculiarities on volumetric perfusion parameters were evaluated. Results: The median arterial blood flow, arterial blood volume, and permeability of the pancreas graft were 115.1 [99.7;130.3] mL/100 mL/min, 46.7 [37.4;56.9] mL/min, and 8.6 [4.1;11.4] mL/100 mL/min, respectively. No statistically significant differences in the averaged perfusion values were found in the head, body, and tail of the pancreas graft. The post-transplantation timing and the number of arteries involved in graft revascularization did not have a significant effect on the volumetric perfusion of the graft. Conclusion: The volumetric perfusion results of the pancreas graft correspond to those obtained in the study of pancreatic perfusion in healthy participants.

Oxygen extraction fraction mapping based combining quantitative susceptibility mapping and quantitative blood oxygenation level-dependent imaging model using multi-delay PCASL

Background and purposeThe oxygen extraction fraction is an essential biomarker for the assessment of brain metabolism. A recently proposed method combined with quantitative susceptibility mapping and quantitative blood oxygen level-dependent magnitude enables noninvasive mapping of the oxygen extraction fraction. Our study investigated the oxygen extraction fraction mapping variations of single-delay and multi-delay arterial spin-labeling. Materials and methodsA total of twenty healthy participants were enrolled. The multi-echo spoiled gradient-echo, multi-delay arterial spin-labeling, and magnetization-prepared rapid gradient echo sequences were acquired at 3.0 T. The mean oxygen extraction fraction was generated under a single delay time of 1780 ms, multi-delay arterial spin-labeling of transit-corrected cerebral blood flow, and multi-delay arterial spin-labeling of arterial cerebral blood volume. The results were compared via paired t tests and the Wilcoxon test. Linear regression analyses were used to investigate the relationships among the oxygen extraction fraction, cerebral blood flow, and venous cerebral blood volume. ResultsThe oxygen extraction fraction estimate with multi-delay arterial spin-labeling yielded a significantly lower value than that with single-delay arterial spin-labeling. The average values for the whole brain under single-delay arterial spin-labeling, multi-delay arterial spin-labeling of transit-corrected cerebral blood flow, and multi-delay arterial spin-labeling of arterial cerebral blood volume were 41.5 ± 1.7 % (P < 0.05), 41.3 ± 1.9 % (P < 0.001), and 40.9 ± 1.9 % (N = 20), respectively. The oxygen extraction fraction also showed a significant inverse correlation with the venous cerebral blood volume under steady-state conditions when multi-delay arterial spin-labeling was used (r = 0.5834, p = 0.0069). ConclusionThese findings suggest that the oxygen extraction fraction is significantly impacted by the arterial spin-labeling methods used in the quantitative susceptibility mapping plus the quantitative blood oxygen level-dependent model, indicating that the differences should be accounted for when employing oxygen extraction fraction mapping based on this model in diseases.

Noninvasive Method Using Mechanical Extensometer for the Estimation of Intracranial Compliance by Repeated Measures Agreement Analysis.

Intracranial compliance refers to the relationship between changes in volume and the resultant changes in intracranial pressure (ICP). This study aimed to assess the agreement of a noninvasive ICP waveform device for the estimation of compliance compared with invasive ICP monitoring employing three distinct methods. We conducted a retrospective analysis of ICP waveform morphology recorded through both invasive (external ventricular drain) and noninvasive (mechanical extensometer) methods in adult patients with acute brain injury admitted to a neurointensive care unit between August 2021 and August 2022. Compliance was calculated as the amplitude of the fundamental component of cerebral arterial blood volume (estimated with concurrent Transcranial Doppler [TCD] recordings), divided by the amplitude of the fundamental component of the invasive and noninvasive ICP waveforms. Subsequently, we assessed the agreement between invasive and noninvasive intracranial compliance by repeated measures correlation coefficient analysis using three methods: TCD-derived, P2/P1 ratio, and time-to-peak (TTP). A linear mixed-effects model was used to compute the concordance correlation coefficient, total deviation index, and coefficient of individual agreement. Coverage probability plot was calculated to estimate the percent of observations within different cut points for each of the three methods. A total of 21 patients were identified for this study. Repeated measures correlation analysis showed a strong correlation (R = 0.982, 95% confidence interval [0.980-0.984], p < 0.0001) between log-transformed noninvasive and invasive compliance. Agreement statistics for TCD, P2/P1 ratio, and TTP indicated that although the concordance correlation coefficient was highest for log(TCD) values, TTP and P2:P1 ratio measures had better agreement with total deviation index and coverage probability plot analyses. Repeated measures correlations suggest that ICP waveform analyses may offer a more accurate estimate of compliance than TCD-derived methods for noninvasive ICP monitoring. Further validations studies are warranted to confidently establish this method as an indicator of intracranial compliance.

Enhanced parameter estimation in multiparametric arterial spin labeling using artificial neural networks.

Multiparametric arterial spin labeling (MP-ASL) can quantify cerebral blood flow (CBF) and arterial cerebral blood volume (CBVa). However, its accuracy is compromised owing to its intrinsically low SNR, necessitating complex and time-consuming parameter estimation. Deep neural networks (DNNs) offer a solution to these limitations. Therefore, we aimed to develop simulation-based DNNs for MP-ASL and compared the performance of a supervised DNN (DNNSup), physics-informed unsupervised DNN (DNNUns), and the conventional lookup table method (LUT) using simulation and in vivo data. MP-ASL was performed twice during resting state and once during the breath-holding task. First, the accuracy and noise immunity were evaluated in the first resting state. Second, CBF and CBVa values were statistically compared between the first resting state and the breath-holding task using the Wilcoxon signed-rank test and Cliff's delta. Finally, reproducibility of the two resting states was assessed. Simulation and first resting-state analyses demonstrated that DNNSup had higher accuracy, noise immunity, and a six-fold faster computation time than LUT. Furthermore, all methods detected task-induced CBF and CBVa elevations, with the effect size being larger with the DNNSup (CBF, p = 0.055, Δ = 0.286; CBVa, p = 0.008, Δ = 0.964) and DNNUns (CBF, p = 0.039, Δ = 0.286; CBVa, p = 0.008, Δ = 1.000) than that with LUT (CBF, p = 0.109, Δ = 0.214; CBVa, p = 0.008, Δ = 0.929). Moreover, all the methods exhibited comparable and satisfactory reproducibility. DNNSup outperforms DNNUns and LUT with respect to estimation performance and computation time.

A Review of Terlipressin in Hepatorenal Syndrome: Targeting Endothelial Dysfunction and Subsequent Cardiovascular Adverse Events.

Hepatorenal syndrome (HRS) is a serious complication of decompensated liver cirrhosis that results in acute kidney injury (AKI). The mortality rate is high. Endothelial dysfunction secondary to liver cirrhosis is a key driver of the development of portal hypertension, which is eventually complicated by ascites and HRS. Ultimately, splanchnic vasodilation and excess gut lymph production result in ascites, low effective arterial blood volume, and maladaptive compensatory mechanisms that contribute to renal hypoperfusion and injury. While the only curative treatment is liver transplantation, vasoconstrictors and albumin have been the mainstay of treatment for candidates who are ineligible or waiting for transplantation. On September 14, 2022, terlipressin, a V1 vasopressin receptor agonist, was approved by the Food and Drug Administration for the treatment of HRS-AKI. In clinical trials, terlipressin plus albumin have been superior to albumin alone and equivocal to noradrenaline plus albumin in renal function improvement. Terlipressin, however, does not improve survival, is costly, and is associated with severe adverse events-including severe cardiac and vascular complications. The aim of this review is to provide an overview of terlipressin pharmacology, adverse events-with a focus on cardiovascular complications-and comparative randomized controlled trials that resulted in the Food and Drug Administration's approval of terlipressin. New literature since its approval and ongoing clinical trials will also be highlighted.

Kidney computed tomography perfusion in patients with ureteral obstruction.

Kidney perfusion on CT is an encouraging surrogate for renal scintigraphy in assessing renal function. However, data on dynamic volumetric CT in patients with kidney obstruction is lacking. Thus, the aim of this study is to determine the feasibility of CT-based renal perfusion using a dynamic volume to assess renal hemodynamics at different degrees and durations of obstruction. We included patients with unilateral kidney obstruction in our single-center, prospective study. The patients were divided into three groups. Patients without dilatation of the pelvicalyceal system (PCS) and normal parenchyma thickness were included into Group 1; patients with PCS dilatation and parenchyma thickness 1.8-2.4 cm-into Group 2; and patients with ureteropyelocalicoectasia and parenchyma thickness less than 1.8 cm-into Group 3. Total of 56 patients were enrolled. In Group 1 mean values of cortical and medullar arterial blood flow, blood volume, and extraction fraction were within the normal range. Changes in contralateral kidney were not determined. Patients from Group 2 showed significant differences in blood flow parameters in the cortical and medulla of the obstructed kidney. No changes in perfusion values in the contralateral kidney was observed. In patients from Group 3 there was a marked decrease in perfusion on the side of obstruction compared to Group 2, indicating that the degree of expansion of the PCS directly correlates with the change in blood flow. However, in the contralateral kidney, these indicators exceeded the normal values of perfusion. CT perfusion allows to objectively assess changes in blood flow in the setting of renal obstruction. The degree of obstruction directly affects the measured rate of blood flow.

Hyponatremia in the Context of Liver Disease.

Hyponatremia is common in patients with liver disease and is associated with increased mortality, morbidity, and a reduced quality of life. In liver transplantation, the inclusion of hyponatremia in organ allocation scores has reduced waitlist mortality. Portal hypertension and the resulting lowering of the effective arterial blood volume are important pathogenetic factors, but in most patients with liver disease, hyponatremia is multifactorial. Treatment requires a multifaceted approach that tries to reduce electrolyte-free water intake, restore urinary dilution, and increase nonelectrolyte solute excretion. Albumin therapy for hyponatremia is a peculiarity of advanced liver disease. Its use appears to be increasing, while the vaptans are currently only given in selected cases. Osmotic demyelination is a special concern in patients with liver disease. Serial checks of serum sodium concentrations and urine volume monitoring are mandatory.

CT-perfusion in the diagnosis of oropharyngeal cancer and monitoring of chemoradiotherapy.

Purpose of the study: to identify diagnostic effectiveness of the CT perfusion method in diagnosing squamous cell carcinoma of the oropharynx and in assessing dynamic changes in the affected area after chemoradiotherapy.Materials and methods. The results of CT perfusion and CT with intravenous contrast were analyzed in 27 patients aged 40 to 76 years, who were divided into three groups: 1) a control group of patients with suspected oropharyngeal tumors – 9 people (33.4%); 2) group of primary (untreated) patients – 8 people. (29.6%) with a verified diagnosis of squamous cell carcinoma; 3) a group of patients with this diagnosis only after chemoradiotherapy – 10 people (37.0%).Results. Our own algorithm for CT perfusion of the oropharynx region was developed. Digital indicators characterizing the presence of tumor tissue in the tissues of the oropharynx were determined: arterial blood flow (AF) and blood volume (BV). When studying CT perfusion indicators, the following was established: in the group of untreated patients, in contrast to the control group of patients, the values of equivalent blood volume (BV), arterial blood flow velocity (AF) and permeability (FE) were statistically significantly increased. Whereas in patients after chemoradiation treatment, compared with the group of untreated patients, CT perfusion indices were statistically significantly reduced in the following parameters: equivalent blood volume (BV), arterial blood flow velocity (AF). The vascular permeability indicator (FE) is only of secondary importance in identifying the tumor process. Analysis of the results of CT perfusion in patients after chemoradiation treatment revealed an almost complete restoration of tissue perfusion indices in terms of AF and BV relative to perfusion indices in patients in the control group.Conclusion. The results of our study indicate the diagnostic effectiveness of CT perfusion in detecting oropharyngeal cancer and in assessing the corresponding changes in the affected area that occur after chemoradiotherapy. Changes in CT perfusion parameters are associated with microcirculation in the tumor area, which is confirmed by a statistically significant decrease in BV and AF parameters after chemoradiotherapy.

Quantification of neurovascular compliance with retrospectively gated phase-contrast MRI.

Neurovascular compliance (NVC) is the change in the brain's arterial tree blood volume, ΔV, divided by the change in intra-vascular blood pressure, ΔP, during the cardiac cycle. The primary aim of this work was to evaluate the performance of MRI measurement of NVC obtained from time-resolved measurements of internal carotid artery (ICA) and vertebral artery (VA) flow rates. A secondary aim was to explore whether NVC could be estimated from common carotid (CCA) flow in conjunction with prior knowledge of mean ICA and VA fractional flow rates, given the small cross-section of ICA and VA in some populations, in particular small children. ΔV was quantified from the blood flow rate measured at the ICA and VA for actual NVC derivation. It was further estimated from individually measured CCA flow rate and mean flow fractions ICA/CCA and VA/CCA (which could alternatively be obtained from literature data), to yield estimated NVC. Time-resolved blood flow rate in CCA, ICA and VA was obtained via retrospectively-gated 2D PC-MRI at 1.5 T in healthy subjects (N = 16, 8 women, mean age 36 ± 13years). ΔP was determined via a brachial pressure measurement. Actual and estimated mean NVC were 27 ± 15 and 38 ± 15μL/mmHg, respectively, and the two measurements were strongly correlated (r = 0.80; p = 0.0002) with test-retest intra-class correlation coefficients of 0.964 and 0.899. Both methods yielded excellent retest precision. In spite of a large bias, actual and estimated NVC were strongly correlated.

Quantitative analysis of similarity between cerebral arterial blood volume and intracranial pressure pulse waveforms during intracranial pressure plateau waves

IntroductionBoth intracranial pressure (ICP) and cerebral arterial blood volume (CaBV) have a pulsatile character related to the cardiac cycle. The evolution of the shape of ICP pulses under increasing ICP or decreasing intracranial compliance is well documented. Nevertheless, the exact origin of the alterations in the ICP morphology remains unclear. Research questionDoes ICP pulse waveform become similar to non-invasively estimated CaBV pulse during ICP plateau waves. Material and methodsA total of 15 plateau waves recorded in 15 traumatic brain injured patients were analyzed. CaBV pulse waveforms were calculated using global cerebral blood flow model from transcranial Doppler cerebral blood flow velocity (CBFV) signals. The difference index (DI) was used to quantify the similarity between ICP and CaBV waveforms. DI was calculated as the sum of absolute sample-by-sample differences between ICP and CaBV waveforms, representing the area between the pulses. ResultsICP increased (19.4 mm Hg [Q1–Q3: 18.2–23.4 mm Hg] vs. 42.7 mm Hg [Q1–Q3: 36.5–45.1 mm Hg], p < 0.001) while CBFV decreased (44.2 cm/s [Q1–Q3: 34.8–69.5 cm/s] vs. 32.9 cm/s [Q1–Q3: 24.7–68.2 cm/s], p = 0.002) during plateau waves. DI was smaller during the plateau waves (20.4 [Q1–Q3: 15.74–23.0]) compared to the baselines (26.3 [Q1–Q3: 24.2–34.7], p < 0.001). Discussion and conclusionThe area between corresponding ICP and CaBV pulse waveforms decreased during the plateau waves which suggests they became similar in shape. CaBV may play a significant role in determining the shape of ICP pulses during the plateau waves and might be a driving force in formulating ICP elevation.

On the optimization of 3D inflow-based vascular-space-occupancy (iVASO) MRI for the quantification of arterial cerebral blood volume (CBVa).

The inflow-based vascular-space-occupancy (iVASO) MRI was originally developed in a single-slice mode to measure arterial cerebral blood volume (CBVa). When vascular crushers are applied in iVASO, the signals can be sensitized predominantly to small pial arteries and arterioles. The purpose of this study is to perform a systematic optimization and evaluation of a 3D iVASO sequence on both 3 T and 7 T for the quantification of CBVa values in the human brain. Three sets of experiments were performed in three separate cohorts. (1) 3D iVASO MRI protocols were compared to single-slice iVASO, and the reproducibility of whole-brain 3D iVASO MRI was evaluated. (2) The effects from different vascular crushers in iVASO were assessed. (3) 3D iVASO MRI results were evaluated in arterial and venous blood vessels identified using ultrasmall-superparamagnetic-iron-oxides-enhanced MRI to validate its arterial origin. 3D iVASO scans showed signal-to-noise ratio (SNR) and CBVa measures consistent with single-slice iVASO with reasonable intrasubject reproducibility. Among the iVASO scans performed with different vascular crushers, the whole-brain 3D iVASO scan with a motion-sensitized-driven-equilibrium preparation with two binomial refocusing pulses and an effective TE of 50 ms showed the best suppression of macrovascular signals, with a relatively low specific absorption rate. When no vascular crusher was applied, the CBVa maps from 3D iVASO scans showed large CBVa values in arterial vessels but well-suppressed signals in venous vessels. A whole-brain 3D iVASO MRI scan was optimized for CBVa measurement in the human brain. When only microvascular signals are desired, a motion-sensitized-driven-equilibrium-based vascular crusher with binomial refocusing pulses can be applied in 3D iVASO.

Brain blood flow pulse analysis may help to recognize individuals who suffer from hydrocephalus

BackgroundNormal pressure hydrocephalus (NPH) is often associated with altered cerebral blood flow. Recent research with the use of the ultrasonic method suggests specific changes in the shape of cardiac-related cerebral arterial blood volume (CaBV) pulses in NPH patients. Our study aims to provide a quantitative analysis of the shape of CaBV pulses, estimated based on transcranial Doppler ultrasonography (TCD) in NPH patients and healthy individuals.MethodsThe CaBV pulses were estimated using TCD cerebral blood flow velocity signals recorded from probable NPH adults and age-matched healthy individuals at rest. The shape of the CaBV pulses was compared to a triangular shape with 27 similarity parameters calculated for every reliable CaBV pulse and compared between patients and volunteers. The diagnostic accuracy of the most prominent parameter for NPH classification was evaluated using the area under the receiver operating characteristic curve (AUC).ResultsThe similarity parameters were calculated for 31 probable NPH patients (age: 59 years (IQR: 47, 67 years), 14 females) and 23 healthy volunteers (age: 54 years (IQR: 43, 61 years), 18 females). Eighteen of 27 parameters were different between healthy individuals and NPH patients (p < 0.05). The most prominent differences were found for the ascending slope of the CaBV pulse with the AUC equal to 0.87 (95% confidence interval: 0.77, 0.97, p < 0.001).ConclusionsThe findings suggest that in NPH, the ascending slope of the CaBV pulse had a slower rise, was more like a straight line, and generally was less convex than in volunteers. Prospective research is required to verify the clinical utility of these findings.

Hyperperfusion of bilateral amygdala in patients with chronic migraine: an arterial spin-labeled magnetic resonance imaging study

BackgroundAmygdala, an essential element of the limbic system, has served as an important structure in pain modulation. There is still a lack of clarity about altered cerebral perfusion of amygdala in migraine. This study aimed to investigate the perfusion variances of bilateral amygdala in episodic migraine (EM) and chronic migraine (CM) using multi-delay pseudo-continuous arterial spin-labeled magnetic resonance imaging (pCASL-MRI).MethodsTwenty-six patients with EM, 55 patients with CM (33 CM with medication overuse headache (MOH)), and 26 age- and sex-matched healthy controls (HCs) were included. All participants underwent 3D multi-delay pCASL MR imaging to obtain cerebral perfusion data, including arrival-time-corrected cerebral blood flow (CBF) and arterial cerebral blood volume (aCBV). The CBF and aCBV values in the bilateral amygdala were compared among the three groups. Correlation analyses between cerebral perfusion parameters and clinical variables were performed.ResultsCompared with HC participants, patients with CM were found to have increased CBF and aCBV values in the left amygdala, as well as increased CBF values in the right amygdala (all P < 0.05). There were no significant differences of CBF and aCBV values in the bilateral amygdala between the HC and EM groups, the EM and CM groups, as well as the CM without and with MOH groups (all P > 0.05). In patients with CM, the increased perfusion parameters of bilateral amygdala were positively correlated with MIDAS score after adjustments for age, sex, and body mass index (BMI).ConclusionHyperperfusion of bilateral amygdala might provide potential hemodynamics evidence in the neurolimbic pain network of CM.

Self‐powered broadband kesterite photodetector with ultrahigh specific detectivity for weak light applications

AbstractKesterite Cu2ZnSn(S,Se)4 (CZTSSe) is a promising candidate for photodetector (PD) applications thanks to its excellent optoelectronic properties. In this work, a green solution‐ processed spin coating and selenization‐processed thermodynamic or kinetic growth of high‐quality narrow bandgap kesterite CZTSSe thin film is developed. A self‐powered CZTSSe/CdS thin‐film PD is then successfully fabricated. Under optimization of light absorber and heterojunction interface, especially tailoring the defect and carrier kinetics, it can achieve broadband response from 300 to 1300 nm, accompanied with a high responsivity of 1.37 A/W, specific detectivity (D*) up to 4.0 × 1014 Jones under 5 nW/cm2, a linear dynamic range (LDR) of 126 dB, and a maximum Ilight/Idark ratio of 1.3 × 108 within the LDR, and ultrafast response speed (rise/decay time of 16 ns/85 ns), representing the leading‐level performance to date, which is superior to those of commercial and well‐researched photodiodes. Additionally, an imaging system with a 905 nm laser is built for weak light response evaluation, and can respond to 718 pW weak light and infrared imaging at a wavelength as low as 5 nW/cm2. It has also been employed for photoplethysmography detection of pulsating signals at both the finger and wrist, presenting obvious arterial blood volume changes, demonstrating great application potential in broadband and weak light photodetection scenarios.

Effect of Nifedipine Used in the Treatment of the Threat of Preterm Labor on Total Uterine Artery Blood Volume Flow Rate.

Evaluation of the effect of maternal nifedipine treatment on total uterine artery blood volume flow rate (TVFR). In this prospective study, 43 women who were admitted to the Perinatology Department of the University of Health Sciences Etlik Zübeyde Hanım Gynecology Training and Research Hospital, with the diagnosis of the threat of preterm labor, and 40 healthy pregnant women, who were randomly selected as the control group, were evaluated between July 1, 2018, and September 1, 2018. A transabdominal ultrasound examination of uterine arteries was performed both before and 48 hours after administration of oral nifedipine for TVFR measurement. For the final analysis, the TVFR levels of the group diagnosed with the threat of preterm labor and the control group were compared. There was no significant difference in either uterine artery pulsatility index or resistance index values as well as the diameters of the uterine arteries after nifedipine treatment (p>0.05 for all). Total uterine artery blood volume flow rate (TVFR) was 424.66±236.74 mL/min before and 543.39±309.68 mL/min after treatment with nifedipine and was statistically significantly higher (p < 0.05). Our study showed a statistically significant increase in total uterine artery blood volume flow rate 48 hours after oral nifedipine treatment.

Brain perfusion imaging by multi-delay arterial spin labeling: Impact of modeling dispersion and interaction with denoising strategies and pathology.

Arterial spin labeling (ASL) acquisitions at multiple post-labeling delays may provide more accurate quantification of cerebral blood flow (CBF), by fitting appropriate kinetic models and simultaneously estimating relevant parameters such as the arterial transit time (ATT) and arterial cerebral blood volume (aCBV). We evaluate the effects of denoising strategies on model fitting and parameter estimation when accounting for the dispersion of the label bolus through the vasculature in cerebrovascular disease. We analyzed multi-delay ASL data from 17 cerebral small vessel disease patients (50 ± 9 y) and 13 healthy controls (52 ± 8 y), by fitting an extended kinetic model with or without bolus dispersion. We considered two denoising strategies: removal of structured noise sources by independent component analysis (ICA) of the control-label image timeseries; and averaging the repetitions of the control-label images prior to model fitting. Modeling bolus dispersion improved estimation precision and impacted parameter values, but these effects strongly depended on whether repetitions were averaged before model fitting. In general, repetition averaging improved model fitting but adversely affected parameter values, particularly CBF and aCBV near arterial locations in patients. This suggests that using all repetitions allows better noise estimation at the earlier delays. In contrast, ICA denoising improved model fitting and estimation precision while leaving parameter values unaffected. Our results support the use of ICA denoising to improve model fitting to multi-delay ASL and suggest that using all control-label repetitions improves the estimation of macrovascular signal contributions and hence perfusion quantification near arterial locations. This is important when modeling flow dispersion in cerebrovascular pathology.

Diagnostic Value of Multi‐delay Multi‐parametric 3D pCASL in Early Alzheimer' Disease

AbstractBackgroundSingle post‐labeling delay (PLD) pseudo‐continuous arterial spin‐labeling (pCASL) measures cerebral blood Flow (CBF). The altered CBF is associated with cognitive decline in early Alzheimer’s disease (AD). However, multi‐delay pCASL that measures multi‐parametric measurements including CBF, arterial cerebral blood volume (aCBV) and arterial transit time (ATT) has rarely been applied to AD studies and its diagnostic performance to recognize AD in early stage remains unclear. The purpose of this study is to compare the diagnostic value between the CBF measured by single PLD pCASL and the CBF/aCBV/ATT measured by multi‐PLD pCASL for early‐stage AD.MethodBoth 1 PLD and 7 PLD 3D pCASL protocols on 3T GE scanner were performed within one MR session for 26 cognitively normal (CN), 37 mild cognitive impairment (MCI) and 39 AD subjects who were recruited in Chinese Imaging, Biomarkers, and Lifestyle Study of Ageing Project (CIBL) from April to October 2021. Comparisons on CBF/aCBV/ATT in 10 regions of interest (ROIs), including left and right regions of olfactory, post cingulate, hippocampus, cuneus and precuneus, were performed across different groups. The area under the curve (AUC) were assessed through receiver operating characteristic (ROC) analysis.ResultAll ROIs showed significant decrease in CBF and increase in ATT of AD groups compared with that of CN and MCI groups (P &lt; 0.05). There was no significant difference in aCBV between groups and CBF/ATT between CN and MCI (P &gt; 0.05). The area under the ROC curve (AUC) of CBF in ROIs for both3D pCASL protocols was similar for discriminating AD against HC (0.949 vs. 0.965 for 1 PLD vs. 7 PLD, respectively), AD against MCI (0.836 vs. 0.830), MCI against HC (0.686 vs. 0.786). However, the combination of CBF/aCBV/ATT in ROIs measured by 7 PLD 3D pCASL could significantly improve diagnostic performance, which AUC was 1.000, 0.967 and 0.918 for identifying AD against HC, AD against MCI and MCI against HC respectively.ConclusionMulti‐parametric perfusion data from multi‐delay pCASL can improve the diagnostic value of AD in early stage, which could be a promising imaging biomarker in AD patients.

Modelling spatiotemporal dynamics of cerebral blood flow using multiple-timepoint arterial spin labelling MRI.

Introduction: Cerebral blood flow (CBF) is an important physiological parameter that can be quantified non-invasively using arterial spin labelling (ASL) imaging. Although most ASL studies are based on single-timepoint strategies, multi-timepoint approaches (multiple-PLD) in combination with appropriate model fitting strategies may be beneficial not only to improve CBF quantification but also to retrieve other physiological information of interest. Methods: In this work, we tested several kinetic models for the fitting of multiple-PLD pCASL data in a group of 10 healthy subjects. In particular, we extended the standard kinetic model by incorporating dispersion effects and the macrovascular contribution and assessed their individual and combined effect on CBF quantification. These assessments were performed using two pseudo-continuous ASL (pCASL) datasets acquired in the same subjects but during two conditions mimicking different CBF dynamics: normocapnia and hypercapnia (achieved through a CO2 stimulus). Results: All kinetic models quantified and highlighted the different CBF spatiotemporal dynamics between the two conditions. Hypercapnia led to an increase in CBF whilst decreasing arterial transit time (ATT) and arterial blood volume (aBV). When comparing the different kinetic models, the incorporation of dispersion effects yielded a significant decrease in CBF (∼10-22%) and ATT (∼17-26%), whilst aBV (∼44-74%) increased, and this was observed in both conditions. The extended model that includes dispersion effects and the macrovascular component has been shown to provide the best fit to both datasets. Conclusion: Our results support the use of extended models that include the macrovascular component and dispersion effects when modelling multiple-PLD pCASL data.

Recent Advances in the Management of Hepatorenal Syndrome: A US Perspective

Acute kidney injury (AKI) is a common complication among decompensated patients with cirrhosis and is associated with significant mortality. 1 Garcia-Tsao G. Parikh C.R. Viola A. Acute kidney injury in cirrhosis. Hepatology. 2008; 48: 2064-2077 Crossref PubMed Scopus (441) Google Scholar In this setting, the most common phenotypes of AKI are hypovolemic/prerenal, acute tubular injury/necrosis, and hepatorenal syndrome (HRS). In this article, the most recent terminology put forth by the International Club of Ascites is used, HRS-AKI, which replaces the prior term HRS type 1. 2 Angeli P. Gines P. Wong F. et al. Diagnosis and management of acute kidney injury in patients with cirrhosis: revised consensus recommendations of the International Club of Ascites. Gut. 2015; 64: 531-537 Crossref PubMed Google Scholar HRS-AKI is a devastating complication of advanced cirrhosis occurring in approximately 17% of AKI cases 1 Garcia-Tsao G. Parikh C.R. Viola A. Acute kidney injury in cirrhosis. Hepatology. 2008; 48: 2064-2077 Crossref PubMed Scopus (441) Google Scholar and is associated with a high 90-day mortality rate of 45% to 51%. 3 Wong F. Pappas S.C. Curry M.P. et al. Terlipressin plus albumin for the treatment of type 1 hepatorenal syndrome. N Engl J Med. 2021; 384: 818-828 Crossref PubMed Scopus (86) Google Scholar ,4 Sanyal A.J. Boyer T.D. Frederick R.T. et al. Reversal of hepatorenal syndrome type 1 with terlipressin plus albumin vs. placebo plus albumin in a pooled analysis of the OT-0401 and REVERSE randomised clinical studies. Aliment Pharmacol Ther. 2017; 45: 1390-1402 Crossref PubMed Scopus (54) Google Scholar The pathophysiology of HRS-AKI is complex. 5 Biggins S.W. Angeli P. Garcia-Tsao G. et al. Diagnosis, evaluation, and management of ascites, spontaneous bacterial peritonitis and hepatorenal syndrome: 2021 practice guidance by the American Association for the Study of Liver Diseases. Hepatology. 2021; 74: 1014-1048 Crossref PubMed Scopus (110) Google Scholar Because of portal hypertension, blood pools in the splanchnic circulation, leading to decreased effective arterial blood volume. As a result, endogenous vasoconstricting systems are activated, leading to sodium and water retention and decreased kidney perfusion. Overlapping with this process there also is increased gut permeability, bacterial translocation, and up-regulation of systemic inflammatory mediators, a secondary cascade that contributes further to impaired kidney perfusion and concomitantly leads to the functional kidney injury seen in HRS-AKI. These dynamic pathophysiologic changes could be potentiated further by infections, acute-on-chronic liver failure (ACLF), or variceal bleeding.

Impact of rigid cervical collars on the vital signs and cervical vasculature: Should we be on the alert for anything?

ObjectiveIn this study, it was aimed to reveal the effect of RCC application on vital signs and physiology of the neck vascular structures. MethodsThe study was designed as a prospective interventional study on 11 volunteers. The factors that would affect the hemodynamics of the volunteers were standardized before the measurements. The vital signs before and after RCC were measured and under the guidance of ultrasonography (USG), internal jugular vein cross-sectional area (CSA), diameter of the common carotid artery (CCAD), peak systolic velocity (PSV). end-diastolic velocity (EDV), time-averaged maximum velocity (TAMAX), Pulsatility Index, Resistivity Index, time averaged mean velocity (TAMEAN), Volume Flow (FV) measurements were made and compared with each other. ResultsAmong 11 volunteers, the study included 5 women (45.5%). 10 min of RCC application was associated with a reduction of the heart rate by 7.9 bpm (95% CI 4.84–10.98) (pre-collar 74.73 + −8.84, post-collar 66.82 + −9.05, p < 0.001). A corresponding 7.18 mmHg (95% CI 2.11–12.25) decrease in systolic blood pressure (pre-collar mean 115.82 mmHg + −12.55, post-collar mean 108.64 mmHg + −11.46, p = 0.01) and 108.55 mL/min reduction of mean common carotid artery blood volume (95% CI 22.28–194.82) (pre-collar 590.14 mL/min + −194.63, post-collar 481.59 mL/min + −279.36, p = 0.019) were noted. Internal jugular vein CSA has decreased for 0.17 cm2 (95% CI 0.05–0.29) (pre-collar CSA 0.53 + −0.29, post-collar CSA 0.36 + −0.17, p = 0.012). ConclusionIn healthy volunteers, RCC application lasting for ten minutes may reduce systolic blood pressure and heart rate, while decreasing blood volume in both the common carotid artery and the internal jugular vein. It has also been noted that the collapse is larger in the internal jugular vein than in the common carotid artery following the pressure applied by RCC.