Cerebral hemodynamics and pseudo‐continuous arterial spin labeling considerations in adults with sickle cell anemia

Sickle cell anemia (SCA) is a genetic disorder resulting in reduced oxygen carrying capacity and elevated stroke risk. Pseudo‐continuous arterial spin labeling (pCASL) measures of cerebral blood flow (CBF) may have relevance for stroke risk assessment; however, the effects of elevated flow velocity and reduced bolus arrival time (BAT) on CBF quantification in SCA patients have not been thoroughly characterized, and pCASL model parameters used in healthy adults are often applied to patients with SCA. Here, cervical arterial flow velocities and pCASL labeling efficiencies were computed in adults with SCA (n = 19) and age‐ and race‐matched controls without sickle trait (n = 7) using pCASL in sequence with phase contrast MR angiography (MRA). Controls (n = 7) and a subgroup of patients (n = 8) also underwent multi‐post‐labeling‐delay pCASL for BAT assessment. Mean flow velocities were elevated in SCA adults (velocity = 28.3 ± 4.1 cm/s) compared with controls (velocity = 24.5 ± 3.8 cm/s), and mean pCASL labeling efficiency (α) was reduced in SCA adults (α = 0.72) relative to controls (α = 0.91). In patients, mean whole‐brain CBF from phase contrast MRA was 91.8 ± 18.1 ml/100 g/min, while mean pCASL CBF when assuming a constant labeling efficiency of 0.86 was 75.2 ± 17.3 ml/100 g/min (p < 0.01), resulting in a mean absolute quantification error of 23% when a labeling efficiency appropriate for controls was assumed. This difference cannot be accounted for by BAT (whole‐brain BAT: control, 1.13 ± 0.06 s; SCA, 1.02 ± 0.09 s) or tissue T₁ variation. In conclusion, BAT variation influences pCASL quantification less than elevated cervical arterial velocity and labeling efficiency variation in SCA adults; thus, a lower labeling efficiency (α = 0.72) or subject‐specific labeling efficiency should be incorporated for SCA patients.     

Timing dependence of peripheral pulse‐wave‐triggered pulsed arterial spin labeling

Arterial spin labeling (ASL) has been developed into a useful technique that is capable of quantifying noninvasively local cerebral blood flow (CBF) using the water molecules in arterial blood as diffusible tracers. Pulsed ASL (PASL) is more strongly affected than continuous ASL (CASL) by cardiac pulsation, because the tag bolus is shorter than the cardiac cycle in most cases. No reports have yet clarified the effects of multiple cardiac phases on the quantification of CBF in PASL when triggering is used. Fourteen subjects participated in this study. Peripheral pulse‐wave‐triggered (PPWT)‐ASL was performed at various time points at the carotid artery (delay 0 ms, second point, foot, peak and tail) and compared with nontriggered (NT)‐ASL. Regions of interest (ROIs) were applied based on the anterior, middle and posterior cerebral artery (ACA, MCA, PCA) territories, and CBFs were compared among different time points and ROIs. PPWT‐ASL strongly affects CBF values compared with NT‐ASL in ACA and MCA territories, especially when measured at the foot of the carotid artery flow phase. CBF_NT was assumed to lie approximately between the minimum and maximum CBFs, with clear statistical significance in several ROIs at several time points of PPWT‐ASL, and CBF_NT was assumed to resemble ‘randomly triggered’ PPWT‐ASL. In conclusion, PPWT‐ASL strongly affects CBF values compared with NT‐ASL, particularly at the foot of the carotid artery flow in ACA and MCA territories. Copyright © 2013 John Wiley & Sons, Ltd.     

Robust arterial transit time and cerebral blood flow estimation using combined acquisition of Hadamard‐encoded multi‐delay and long‐labeled long‐delay pseudo‐continuous arterial spin labeling: a simulation and in vivo study

Arterial transit time (ATT) prolongation causes an error of cerebral blood flow (CBF) measurement during arterial spin labeling (ASL). To improve the accuracy of ATT and CBF in patients with prolonged ATT, we propose a robust ATT and CBF estimation method for clinical practice. The proposed method consists of a three‐delay Hadamard‐encoded pseudo‐continuous ASL (H‐pCASL) with an additional‐encoding and single‐delay with long‐labeled long‐delay (1dLLLD) acquisition. The additional‐encoding allows for the reconstruction of a single‐delay image with long‐labeled short‐delay (1dLLSD) in addition to the normal Hadamard sub‐bolus images. Five different images (normal Hadamard 3 delay, 1dLLSD, 1dLLLD) were reconstructed to calculate ATT and CBF. A Monte Carlo simulation and an in vivo study were performed to access the accuracy of the proposed method in comparison to normal 7‐delay (7d) H‐pCASL with equally divided sub‐bolus labeling duration (LD). The simulation showed that the accuracy of CBF is strongly affected by ATT. It was also demonstrated that underestimation of ATT and CBF by 7d H‐pCASL was higher with longer ATT than with the proposed method. Consistent with the simulation, the 7d H‐pCASL significantly underestimated the ATT compared to that of the proposed method. This underestimation was evident in the distal anterior cerebral artery (ACA; P = 0.0394) and the distal posterior cerebral artery (PCA; 2 P = 0.0255). Similar to the ATT, the CBF was underestimated with 7d H‐pCASL in the distal ACA (P = 0.0099), distal middle cerebral artery (P = 0.0109), and distal PCA (P = 0.0319) compared to the proposed method. Improving the SNR of each delay image (even though the number of delays is small) is crucial for ATT estimation. This is opposed to acquiring many delays with short LD. The proposed method confers accurate ATT and CBF estimation within a practical acquisition time in a clinical setting.     

MR fingerprinting ASL: Sequence characterization and comparison with dynamic susceptibility contrast (DSC) MRI

MR Fingerprinting (MRF)‐based Arterial‐Spin‐Labeling (ASL) has the potential to measure multiple parameters such as cerebral blood flow (CBF), bolus arrival time (BAT), and tissue T₁ in a single scan. However, the previous reports have only demonstrated a proof‐of‐principle of the technique but have not examined the performance of the sequence in the context of key imaging parameters. Furthermore, there has not been a study to directly compare the technique to clinically used perfusion method of dynamic‐susceptibility‐contrast (DSC) MRI. The present report consists of two studies. In the first study (N = 8), we examined the dependence of MRF‐ASL sequence on TR time pattern. Ten different TR patterns with a range of temporal characteristics were examined by both simulations and experiments. The results revealed that there was a significance dependence of the sequence performance on TR pattern (p < 0.001), although there was not a single pattern that provided dramatically improvements. Among the TR patterns tested, a sinusoidal pattern with a period of 125 TRs provided an overall best estimation in terms of spatial consistency. These experimental observations were consistent with those of numerical simulations. In the second study (N = 8), we compared MRF‐ASL results with those of DSC MRI. It was found that MRF‐ASL and DSC MRI provided highly comparable maps of cerebral blood flow (CBF) and bolus‐arrival‐time (BAT), with spatial correlation coefficients of 0.79 and 0.91, respectively. However, in terms of quantitative values, BAT obtained with MRF‐ASL was considerably lower than that from DSC (p < 0.001), presumably because of the differences in tracer characteristics in terms of diffusible versus intravascular tracers. Test–retest assessment of MRF‐ASL MRI revealed that the spatial correlations of parametric maps were 0.997, 0.962, 0.746 and 0.863 for B₁⁺, T₁, CBF, and BAT, respectively. MRF‐ASL is a promising technique for assessing multiple perfusion parameters simultaneously without contrast agent.     

Structural MRI of carotid artery atherosclerotic lesion burden and characterization of hemispheric cerebral blood flow before and after carotid endarterectomy

Collateral circulation plays a major role in maintaining cerebral blood flow (CBF) in patients with internal carotid artery (ICA) stenosis. CBF can remain normal despite severe ICA stenosis, making the benefit of carotid endarterectomy (CEA) or stenting difficult to assess. Before and after surgery, we assessed CBF supplied through the ipsilateral (stenotic) or contralateral ICA individually with a novel hemisphere-selective arterial spin-labeling (ASL) perfusion MR technique. We further explored the relationship between CBF and ICA obstruction ratio (OR) acquired with a multislice black-blood imaging sequence. For patients with unilateral ICA stenosis (n = 19), conventional bilateral labeling did not reveal interhemispheric differences. With unilateral labeling, CBF in the middle cerebral artery (MCA) territory on the surgical side from the ipsilateral supply (53.7 +/- 3.3 ml/100 g/min) was lower than CBF in the contralateral MCA territory from the contralateral supply (58.5 +/- 2.7 ml/100 g/min), although not statistically significant (p = 0.09). The ipsilateral MCA territory received significant (p = 0.02) contralateral supply (7.0 +/- 2.7 ml/100 g/min), while ipsilateral supply to the contralateral side was not reciprocated. After surgery (n = 11), ipsilateral supply to the MCA territory increased from 57.3 +/- 5.7 to 67.3 +/- 5.4 ml/100 g/min (p = 0.03), and contralateral supply to the ipsilateral MCA territory decreased. The best predictor of increased CBF on the side of surgery was normalized presurgical ipsilateral supply (r(2) = 0.62, p = 0.004). OR was less predictive of change, although the change in normalized contralateral supply was negatively correlated with OR(excess) (=OR(ipsilateral) - OR(contralateral)) (r(2) = 0.58, p = 0.006). The results demonstrate the effect of carotid artery stenosis on blood supply to the cerebral hemispheres, as well as the relative role of collateral pathways before surgery and redistribution of blood flow through these pathways after surgery. Unilateral ASL may better predict hemodynamic surgical outcome (measured by improved perfusion) than ICA OR.     

Reliability and precision of pseudo‐continuous arterial spin labeling perfusion MRI on 3.0 T and comparison with 15O‐water PET in elderly subjects at risk for Alzheimer's disease

Arterial spin labeling (ASL) offers MRI measurement of cerebral blood flow (CBF) in vivo, and may offer clinical diagnostic utility in populations such as those with early Alzheimer's disease (AD). In the current study, we investigated the reliability and precision of a pseudo‐continuous ASL (pcASL) sequence that was performed two or three times within one hour on eight young normal control subjects, and 14 elderly subjects including 11 with normal cognition, one with AD and two with Mild Cognitive Impairment (MCI). Six of these elderly subjects including one AD, two MCIs and three controls also received ¹⁵O‐water positron emission tomography (PET) scans 2 h before their pcASL MR scan. The instrumental reliability of pcASL was evaluated with the intraclass correlation coefficient (ICC). The ICCs were greater than 0.90 in pcASL global perfusion measurements for both the young and the elderly groups. The cross‐modality perfusion imaging comparison yielded very good global and regional agreement in global gray matter and the posterior cingulate cortex. Significant negative correlation was found between age and the gray/white matter perfusion ratio (r = –0.62, p < 0.002). The AD and MCI patients showed the lowest gray/white matter perfusion ratio among all the subjects. The data suggest that pcASL provides a reliable whole brain CBF measurement in young and elderly adults whose results converge with those obtained with the traditional ¹⁵O‐water PET perfusion imaging method. pcASL perfusion MRI offers an alternative method for non‐invasive in vivo examination of early pathophysiological changes in AD. Copyright © 2009 John Wiley & Sons, Ltd.     

Time‐efficient measurement of multi‐phase arterial spin labeling MR signal in white matter

White matter (WM) perfusion has great potential as a physiological biomarker in many neurological diseases. Although it has been demonstrated previously that arterial spin labeling magnetic resonance imaging (ASL‐MRI) enables the detection of the perfusion‐weighted signal in most voxels in WM, studies of cerebral blood flow (CBF) in WM by ASL‐MRI are relatively scarce because of its particular challenges, such as significantly lower perfusion and longer arterial transit times relative to gray matter (GM). Recently, ASL with a spectroscopic readout has been proposed to enhance the sensitivity for the measurement of WM perfusion. However, this approach suffers from long acquisition times, especially when acquiring multi‐phase ASL datasets to improve CBF quantification. Furthermore, the potential increase in the signal‐to‐noise ratio (SNR) by spectroscopic readout compared with echo planar imaging (EPI) readout has not been proven experimentally. In this study, we propose the use of time‐encoded pseudo‐continuous ASL (te‐pCASL) with single‐voxel point‐resolved spectroscopy (PRESS) readout to quantify WM cerebral perfusion in a more time‐efficient manner. Results are compared with te‐pCASL with a conventional EPI readout for both WM and GM perfusion measurements. Perfusion measurements by te‐pCASL PRESS and conventional EPI showed no significant difference for quantitative WM CBF values (Student's t‐test, p = 0.19) or temporal SNR (p = 0.33 and p = 0.81 for GM and WM, respectively), whereas GM CBF values (p = 0.016) were higher using PRESS than EPI readout. WM CBF values were found to be 18.2 ± 7.6 mL/100 g/min (PRESS) and 12.5 ± 5.5 mL/100 g/min (EPI), whereas GM CBF values were found to be 77.1 ± 11.2 mL/100 g/min (PRESS) and 53.6 ± 9.6 mL/100 g/min (EPI). This study demonstrates the feasibility of te‐pCASL PRESS for the quantification of WM perfusion changes in a highly time‐efficient manner, but it does not result in improved temporal SNR, as does traditional te‐pCASL EPI, which remains the preferred option because of its flexibility in use.     

Sleep disorders in spinocerebellar ataxia type 10

As sleep disturbances have been reported in spinocerebellar ataxias (SCAs), including types SCA1, SCA2, SCA3, SCA6 and SCA13, identification and management of these disturbances can help minimise their impact on SCA patients' overall body functions and quality of life. To our knowledge, there are no studies that investigate sleep disturbances in SCA10. Therefore, the aim of this study was to assess sleep disturbances in patients with SCA10. Twenty‐three SCA10 patients and 23 healthy controls were recruited. Patients were evaluated in terms of their demographic and clinical data, including disease severity (Scale for the Assessment and Rating of Ataxia, SARA) and excessive daytime sleepiness (Epworth Sleepiness Scale, ESS), and underwent polysomnography. SCA10 patients had longer rapid eye movement (REM) sleep (p = .04) and more REM arousals than controls (p< .0001). There was a correlation of REM sleep onset with the age of onset of symptoms (r = .459), and with disease duration (r = ?.4305). There also was correlation between the respiratory disturbance index (RDI) and SARA (r = ?.4013), and a strong indirect correlation between arousal index and age at onset of symptoms (r = ?.5756). In conclusion, SCA10 patients had sleep abnormalities that included more REM arousals and higher RDI than controls. Our SCA10 patients had sleep disorders related to shorter disease duration and lower severity of ataxia, in a pattern similar to that of other neurodegenerative diseases.     

Systemic inflammation and alterations to cerebral blood flow in obstructive sleep apnea

Systemic inflammation and alterations to regional cerebral blood flow (CBF) have been reported previously in obstructive sleep apnea (OSA). This study utilized arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI) to evaluate CBF in OSA patients and determine its relationship with systemic inflammation. Twenty male patients with moderate and severe OSA [apnea–hypopnea index (AHI) >15] and 16 healthy male volunteers (AHI <5) were recruited. Early‐ or late‐phase changes in leucocyte apoptosis and its subsets were determined by flow cytometry. Perfusion MRI data were acquired with a pulsed continuous ASL technique. The CBF maps were compared using voxel‐based statistics to determine differences between the OSA and control groups. The differences in CBF, clinical severity and leucocyte apoptosis were correlated. Exploratory groupwise comparison between the two groups revealed that the OSA patients exhibited low CBF values in the vulnerable regions. The lower regional CBF values were correlated with higher clinical disease severity and leucocyte apoptosis. OSA impairs cerebral perfusion in vulnerable regions, and this deficit is associated with increased disease severity. The apparent correlation between systemic inflammation and cerebral perfusion may be indicative of haemodynamic alterations and their consequences in OSA.     

动脉自旋标记在急性脑梗死中的应用

目的 探讨动脉自旋标记（ASL）在急性脑梗死中的应用价值。方法 选取2016年8月~2018年2月我院收治的脑梗死患者29例,所有患者均行扩散加权（DWI）、ASL及脑血管成像（MRA）扫描。分析急性脑梗死患者的基线ASL数据,比较治疗前后存在缺血半暗带（IP）患者DWI高信号区与周边低灌注区CBF患侧、CBF对侧、rCBF以及ASL-CBF。结果 29例急性脑梗死患者中,22例患者存在IP,7例患者不存在IP。22例IP患者中,DWI高信号区CBF患侧血流值低于CBF对侧,周边低灌注区3、6、9、12点钟ROI CBF患侧血流值低于CBF对侧,且高于DWI高信号区,差异有统计学意义（P＜0.05）。DWI高信号区与周边低灌注区对侧血流值比较,差异无统计学意义（P＞0.05）。DWI高信号区治疗前后ASL-CBF比较,差异无统计学意义（P＞0.05）。治疗后,周边低灌注区3、6、9、12点钟ROI ASL-CBF均高于治疗前,差异有统计学意义（P＜0.05）。结论 ASL能在一定程度上反映脑低灌注水平,与DWI配合可辅助诊断IP,可提示预后。     

Visuomotor adaptive improvement and aftereffects are impaired differentially following cerebellar lesions in SCA and PICA territory

The aim of the present study was to elucidate the contribution of the superior and posterior inferior cerebellum to adaptive improvement and aftereffects in a visuomotor adaptation task. Nine patients with ischemic lesions within the territory of the posterior inferior cerebellar artery (PICA), six patients with ischemic lesions within the territory of the superior cerebellar artery (SCA) and 17 age-matched controls participated. All subjects performed center-out reaching movements under 60° rotation of visual feedback. For the assessment of aftereffects, we tested retention of adaptation and de-adaptation under 0° visual rotation. From this data we also quantified five measures of motor performance. Cerebellar lesion-symptom mapping was performed using magnetic resonance imaging subtraction analysis. Adaptive improvement during 60° rotation was significantly degraded in PICA patients and even more in SCA patients. Subtraction analysis revealed that posterior (Crus I) as well as anterior cerebellar regions (lobule V) showed a common overlap related to deficits in adaptive improvement. However, for aftereffect measures as well as for motor performance variables only SCA patients, but not PICA patients showed significant differences to control subjects. Subtraction analysis showed that affection of lobules V and VI were more common in patients with impaired retention and de-adaptation, respectively. Data shows that areas both within the superior and posterior inferior cerebellum are involved in adaptive improvement. However, only the superior cerebellum including lobules V and VI appears to be important for aftereffects and therefore true adaptive ability.     

Hemodynamic Effect of Cerebral Vasospasm in Humans: A Modeling Study

A mathematical model of cerebral hemodynamics during vasospasm is presented. The model divides arterial hemodynamics into two cerebral territories: with and without spasm. It also includes collateral circulation between the two territories, cerebral venous hemodynamics, cerebrospinal fluid circulation, intracranial pressure (ICP) and the craniospinal storage capacity. Moreover, the pial artery circulation in both territories is affected by cerebral blood flow (CBF) autoregulation mechanisms. In this work, a numerical value to model parameters was given assuming that vasospasm affects only a single middle cerebral artery (MCA). In a first stage, the model is used to simulate some clinical results reported in the literature, concerning the patterns of MCA velocity, CBF and pressure losses during vasospasm. The agreement with clinical data turns out fairly good. In a second stage, a sensitivity analysis on some model parameters is performed (severity of caliber reduction, longitudinal extension of the spasm, autoregulation gain, ICP, resistance of the collateral circulation, and mean systemic arterial pressure) to clarify their influence on hemodynamics in the spastic territory. The results suggest that the clinical impact of vasospasm depends on several concomitant factors, which should be simultaneously taken into account to reach a proper diagnosis. In particular, while a negative correlation between MCA velocity and cross sectional area can be found until CBF is well preserved, a positive correlation may occur when CBF starts to decrease significantly. This might induce false-negative results if vasospasm is assessed merely through velocity measurements performed by the transcranial Doppler technique. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8719La, 8710+e     

Amplitude changes of unconditioned eyeblink responses in patients with cerebellar lesions

Timing and amplitude parameters of unconditioned eyeblink responses were investigated in 24 patients with unilateral cerebellar lesions following infarcts within the territory of the superior cerebellar artery (SCA, n=12) and of the posterior inferior cerebellar artery (PICA, n=12). The extent of cortical cerebellar lesions, i.e., which lobules were affected and possible involvement of cerebellar nuclei, was determined by three-dimensional magnetic resonance imaging (3D MRI). Amplitude parameters of eyeblink responses were normalized and expressed as percentage of the unaffected side in patients and the second tested side in age-matched controls. Normalized peak amplitudes, burst area and burst duration were significantly increased in SCA patients with lesions restricted to cortical areas. Burst onset and time to peak were not significantly different compared with controls. Temporal and amplitude parameters of eyeblink responses were unchanged in SCA patients with additional involvement of cerebellar nuclei and in patients with lesions of the PICA territory. Consistent with animal lesion and recording studies and a recent human functional magnetic resonance imaging (fMRI) study, the present data suggest that cortical areas of the superior cerebellum are of importance in eyeblink control in humans. These areas partly overlap with areas known to be critical in eyeblink conditioning.     

Effects of MASP2 haplotypes and MASP‐2 levels in hepatitis C‐infected patients

Mannan‐binding lectin (MBL) and MBL‐associated serine protease 2 (MASP‐2) are components of the lectin pathway, which activate the complement system after binding to the HCV structural proteins E1 and E2. We haplotyped 11 MASP2 polymorphisms in 103 HCV patients and 205 controls and measured MASP‐2 levels in 67 HCV patients and 77 controls to better understand the role of MASP‐2 in hepatitis C susceptibility and disease severity according to viral genotype and fibrosis levels. The haplotype block MASP2*ARDP was associated with protection against HCV infection (OR = 0.49, p = .044) and lower MASP‐2 levels in controls (p = .021), while haplotype block AGTDVRC was significantly increased in patients (OR = 7.58, p = .003). MASP‐2 levels were lower in patients than in controls (p < .001) and in patients with viral genotype 1 or 4 (poor responders to treatment) than genotype 3 (p = .022) and correlated inversely with the levels of alkaline phosphatase, especially in individuals with fibrosis 3 or 4 (R = ?.7, p = .005). MASP2 gene polymorphisms modulate basal gene expression, which may influence the quality of complement response against HCV. MASP‐2 levels decrease during chronic disease, independently of MASP2 genotypes, most probably due to consumption and attenuation mechanisms of viral origin and by the reduced liver function, the site of MASP‐2 production.     

Background suppression in arterial spin labeling MRI with a separate neck labeling coil

In arterial spin labeling (ASL) MRI to measure cerebral blood flow (CBF), pair-wise subtraction of temporally adjacent non-labeled and labeled images often can not completely cancel the background static tissue signal because of temporally fluctuating physiological noise. While background suppression (BS) by inversion nulling improves CBF temporal stability, imperfect pulses compromise CBF contrast. Conventional BS techniques may not be applicable in small animals because the arterial transit time is short. This study presents a novel approach of BS to overcome these drawbacks using a separate 'neck' radiofrequency coil for ASL and a 'brain' radiofrequency coil for BS with the inversion pulse placed before spin labeling. The use of a separate 'neck' coil for ASL should also improve ASL contrast. This approach is referred to as the inversion-recovery BS with the two-coil continuous ASL (IR-cASL) technique. The temporal and spatial contrast-to-noise characteristics of basal CBF and CBF-based fMRI of hypercapnia and forepaw stimulation in rats at 7 Tesla were analyzed. IR-cASL yielded two times better temporal stability and 2.0-2.3 times higher functional contrast-to-noise ratios for hypercapnia and forepaw stimulation compared with cASL without BS in the same animals. The Bloch equations were modified to provide accurate CBF quantification at different levels of BS and for multislice acquisition where different slices have different degree of BS and residual degree of labeling. Improved basal CBF and CBF-based fMRI sensitivity should lead to more accurate CBF quantification and should prove useful for imaging low CBF conditions such as in white matter and stroke.     

Sleep‐disordered breathing in major depressive disorder

Individuals with major depressive disorder often experience obstructive sleep apnea. However, the relationship between depression and less severe sleep‐disordered breathing is unclear. This study examined the rate of sleep‐disordered breathing in depression after excluding those who had clinically significant sleep apnea (>5 apneas?h^?1). Archival data collected between 1991 and 2005 were used to assess the prevalence of sleep‐disordered breathing events in 60 (31 depressed; 29 healthy controls) unmedicated participants. Respiratory events were automatically detected using a program developed in‐house measuring thermal nasal air‐flow and chest pressure. Results show that even after excluding participants with clinically significant sleep‐disordered breathing, individuals with depression continue to exhibit higher rates of sleep‐disordered breathing compared with healthy controls (depressed group: apnea–hypopnea index mean = 0.524, SE = 0.105; healthy group: apnea–hypopnea index mean = 0.179, SE = 0.108). Exploratory analyses were also conducted to assess for rates of exclusion in depression studies due to sleep‐disordered breathing. Study exclusion of sleep‐disordered breathing was quantified based on self‐report during telephone screening, and via first night polysomnography. Results from phone screening data reveal that individuals reporting depression were 5.86 times more likely to report a diagnosis of obstructive sleep apnea than presumptive control participants. Furthermore, all of the participants excluded for severe sleep‐disordered breathing detected on the first night were participants with depression. These findings illustrate the importance of understanding the relationship between sleep‐disordered breathing and depression, and suggest that screening and quantification of sleep‐disordered breathing should be considered in depression research.     

大脑中动脉供血区脑缺血后同侧丘脑继发性损害的MR实验研究

本文应用磁共振(magnetic resonance,MR)成像在体观察大脑中动脉(middle cerebral artery,MCA)供血区脑缺血后同侧丘脑的信号变化。结果显示:(1)通过MRA(magnetic resonance angiography)可以观测到单侧MCA的闭塞与血流再通,而供应丘脑的大脑后动脉信号无变化;(2)脑缺血后1d MR T2WI(T2weighted imaging)显示单侧MCA供血区原发病灶呈高信号,3d、7d时此原发病灶信号增高程度有所降低,至14d信号强度再次明显增高;(3)脑缺血后1d和3d时双侧丘脑T2信号无差别,7d和14d时脑缺血同侧丘脑T2信号减低,T2值降低;(4)MCA供血区脑缺血后原发病灶和同侧丘脑T2值的变化不同步。上述结果证实MR能够在活体显示MCA供血区脑缺血后同侧丘脑的继发性损害。     

ASL‐MRICloud: An online tool for the processing of ASL MRI data

Arterial spin labeling (ASL) MRI is increasingly used in research and clinical settings. The purpose of this work is to develop a cloud‐based tool for ASL data processing, referred to as ASL‐MRICloud, which may be useful to the MRI community. In contrast to existing ASL toolboxes, which are based on software installation on the user's local computer, ASL‐MRICloud uses a web browser for data upload and results download, and the computation is performed on the remote server. As such, this tool is independent of the user's operating system, software version, and CPU speed. The ASL‐MRICloud tool was implemented to be compatible with data acquired by scanners from all major MRI manufacturers, is capable of processing several common forms of ASL, including pseudo‐continuous ASL and pulsed ASL, and can process single‐delay and multi‐delay ASL data. The outputs of ASL‐MRICloud include absolute and relative values of cerebral blood flow, arterial transit time, voxel‐wise masks indicating regions with potential hyper‐perfusion and hypo‐perfusion, and an image quality index. The ASL tool is also integrated with a T₁‐based brain segmentation and normalization tool in MRICloud to allow generation of parametric maps in standard brain space as well as region‐of‐interest values. The tool was tested on a large data set containing 309 ASL scans as well as on publicly available ASL data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study.     

磁共振3D-ASL定量评估儿童病毒性脑炎脑灌注特征

目的:探讨儿童病毒性脑炎的磁共振三维动脉自旋标记（3D-ASL）成像的灌注特征。方法:回顾性收集25例急性病毒性脑炎患儿和25名年龄相仿的健康对照组。在脑血流量（CBF）伪彩图上对每个患者进行视觉评估，定量分析病变区与对照组CBF值差异，确定儿童病毒性脑炎的脑灌注特征。结果:25例病毒性脑炎患儿在急性期灌注显著增高，急性病变的CBF值、标准化CBF值显著高于对照组，其ROC-AUC值分别为0.971和0.992。9例患儿在治疗好转后进行复查，病变区血流灌注随病情好转而减低。结论:儿童病毒性脑炎的3D-ASL成像表现有一定特征，病灶在急性期灌注显著增高，病情好转后减低。3D-ASL可以为儿童病毒性脑炎诊断和随访提供一种新的影像学参考。     

Anaphylaxis to galacto‐oligosaccharides – an evaluation in an atopic population in Singapore

Anaphylaxis to galacto‐oligosaccharides (GOS), a prebiotic, has been described in atopic patients following its supplementation in commercial milk formula in South‐East Asia. The epidemiology of this usual allergy to a carbohydrate is unknown. This study evaluated the prevalence of allergy to two formulations of commercial GOS, Vivinal^? GOS (vGOS) and Oligomate^?, in an atopic cohort. Atopic subjects (n = 487) from two specialist allergy clinics were surveyed via structured questionnaire and underwent skin prick tests to GOS. Subjects with positive skin prick tests to GOS (n = 30, 6.2%) underwent basophil activation tests, and a subset (n = 13) underwent oral challenge tests to both formulations of GOS. Six subjects had positive challenges to vGOS; and none to Oligomate. By extrapolating the BAT and oral challenge results, the prevalence of allergy to vGOS is estimated at up to 3.5% (95% CI 2.2–5.5%) of our atopic population. Our findings show that GOS allergy may be common amongst atopics in Singapore.