Real-time fMRI neurofeedback of the anterior insula using arterial spin labelling.

Arterial spin labelling (ASL) is the only non-invasive technique that allows absolute quantification of perfusion and is increasingly used in brain activation studies. Contrary to the blood oxygen level-dependent (BOLD) effect ASL measures the cerebral blood flow (CBF) directly. However, the ASL signal has a lower signal-to-noise ratio (SNR), than the BOLD signal, which constrains its utilization in neurofeedback studies. If successful, ASL neurofeedback can be used to aid in the rehabilitation of health conditions with impaired blood flow, for example, stroke. We provide the first ASL-based neurofeedback study incorporating a double-blind, sham-controlled design. A pseudo-continuous ASL (pCASL) approach with background suppression and 3D GRASE readout was combined with a real-time post-processing pipeline. The real-time pipeline allows to monitor the ASL signal and provides real-time feedback on the neural activity to the subject. In total 41 healthy adults (19-56 years) divided into three groups underwent a neurofeedback-based emotion imagery training of the left anterior insula. Two groups differing only in the explicitness level of instruction received real training and a third group received sham feedback. Only those participants receiving real feedback with explicit instruction showed significantly higher absolute CBF values in the trained region during neurofeedback than participants receiving sham feedback. However, responder analyses of percent signal change values show no differences in activation between the three groups. Persisting limitations, such as the lower SNR, confounding effects of arterial transit time and partial volume effects still impact negatively the implementation of ASL neurofeedback.

Trial of the Cerebral Perfusion Response to Sodium Nitrite Infusion in Patients with Acute Subarachnoid Haemorrhage using Arterial Spin Labelling MRI.

Aneurysmal subarachnoid haemorrhage (SAH) is a devastating subset of stroke. One of the major determinants of outcome is an evolving multifactorial injury occurring in the first 72 hours, known as early brain injury. Reduced nitric oxide (NO) bioavailability and an associated disruption to cerebral perfusion is believed to play an important role in this process. We sought to explore this relationship, by examining the effect on cerebral perfusion of the in vivo manipulation of NO levels using an exogenous NO donor (sodium nitrite). We performed a double blind placebo controlled randomised experimental medicine study of the cerebral perfusion response to sodium nitrite infusion during the early brain injury period in 15 low grade (World Federation of Neurosurgeons grade 1-2) SAH patients. Patients were randomly assigned to receive sodium nitrite at 10 mcg/kg/min or saline placebo. Assessment occurred following endovascular aneurysm occlusion, mean time after ictus 66h (range 34-90h). Cerebral perfusion was quantified before infusion commencement and after 3 hours, using multi-post labelling delay (multi-PLD) vessel encoded pseudocontinuous arterial spin labelling (VEPCASL) magnetic resonance imaging (MRI). Administration of sodium nitrite was associated with a significant increase in average grey matter cerebral perfusion. Group level voxelwise analysis identified that increased perfusion occurred within regions of the brain known to exhibit enhanced vulnerability to injury. These findings highlight the role of impaired NO bioavailability in the pathophysiology of early brain injury.

Diurnal variation of cerebral blood flow in healthy humans under normal entrained conditions.

The presence of a circadian cycle of cerebral blood flow may have implications for the occurrence of daily variations in cerebrovascular events in humans, but how cerebral blood flow varies throughout the day and its mechanism are still unclear. The study aimed to explore the diurnal variation of cerebral blood flow in healthy humans and its possible mechanisms. Arterial spin labelling images were collected at six time-points (09:00 hours, 13:00 hours, 17:00 hours, 21:00 hours, 01:00 hours, 05:00 hours) from 18 healthy participants (22-39 years old; eight females) to analyse diurnal variations in cerebral blood flow. Resting heart rate and blood pressure at six time-points and blood indicators (20-hydroxyeicosatetraenoic acid, epoxyeicosatrienoic acids, prostaglandin E2, noradrenaline and nitric oxide) related to cerebral vascular tone at two time-points (09:00 hours and 21:00 hours) were collected to analyse possible influences on diurnal variations in cerebral blood flow. From 21:00 hours to 05:00 hours, parietal cortical relative cerebral blood flow tended to increase, while frontal cortical and cerebellar relative cerebral blood flow tended to decrease. There was a time-dependent negative correlation between parietal cortical relative cerebral blood flow and resting heart rate, whereas there was a time-dependent positive correlation between cerebellar relative cerebral blood flow and resting heart rate. The change of parietal cortical relative cerebral blood flow was positively correlated with the change of nitric oxide. There was also a time-dependent positive correlation between mean arterial pressure and mean whole-brain cerebral blood flow. The findings indicated that parietal cortical relative cerebral blood flow and frontal cortical/cerebellar relative cerebral blood flow showed roughly opposite trends throughout the day. The diurnal variations in relative cerebral blood flow were regional-specific. Diurnal variation of nitric oxide and neurogenic regulation may be potential mechanisms for diurnal variation in regional relative cerebral blood flow.

Effects on cerebral blood flow after single doses of the ß2 agonist, clenbuterol, in healthy volunteers and patients with mild cognitive impairment or Parkinson's disease.

AIMS: Cerebral hypometabolism occurs years prior to a diagnosis of neurodegenerative diseases and coincides with reduced cerebral perfusion and declining noradrenergic transmission from the locus coeruleus. In pre-clinical models, ß-adrenoceptor (ß-AR) agonists increase cerebrocortical glucose metabolism, and may have therapeutic potential for neurodegenerative diseases. This study investigated the safety and effects on regional cerebral blood flow (rCBF) of the oral, brain-penetrant ß2-AR agonist, clenbuterol, in healthy volunteers (HV) and patients with mild cognitive impairment (MCI) or Parkinson's disease (PD). METHODS: This study evaluated the safety and effects on cerebral activity of the oral, brain-penetrant, ß2-AR agonist clenbuterol (20-160 µg) in healthy volunteers and patients with MCI or PD. Regional CBF, which is tightly coupled to glucose metabolism, was measured by arterial spin labelling MRI in 32 subjects (25 HV and 8 MCI or PD) across five cohorts. In some cohorts, low doses of nadolol (1-5 mg), a ß-AR antagonist with minimal brain penetration, were administered with clenbuterol to control peripheral ß2-AR responses. RESULTS: Significant, dose-dependent increases in rCBF were seen in multiple brain regions, including hippocampus, amygdala and thalamus, following the administration of clenbuterol to HVs (mean changes from baseline in hippocampal rCBF of -1.7%, 7.3%, 22.9%, 28.4% 3 h after 20, 40, 80 and 160 µg clenbuterol, respectively). In patients with MCI or PD, increases in rCBF following 80 µg clenbuterol were observed both without and with 5 mg nadolol (in hippocampus, 18.6%/13.7% without/with nadolol). Clenbuterol was safe and well-tolerated in all subjects; known side effects of ß2-agonists, including increased heart rate and tremor, were mild in intensity and were blocked by low-dose nadolol. CONCLUSIONS: The effects of clenbuterol on rCBF were evident both in the absence and presence of low-dose nadolol, suggesting central nervous system (CNS) involvement. Concomitant inhibition of the peripheral effects of clenbuterol by nadolol confirms that meaningful ß2-AR antagonism in the periphery was achieved without interrupting the central effects of clenbuterol on rCBF.

Alterations of perfusion and functional connectivity of the cingulate motor area are associated with psychomotor retardation in major depressive disorder.

Psychomotor retardation, characterized by slowing of speech, thoughts, and a decrease of movements, is frequent in patients with major depressive disorder (MDD). However, its neurobiological correlates are still poorly understood. This study aimed to explore if cerebral blood flow (CBF) and resting state functional connectivity (rs-FC) of the motor network are altered in patients with MDD and if these changes are associated with psychomotor retardation. Thirty-six right-handed patients with depression and 19 right-handed healthy controls (HC) that did not differ regarding age and sex underwent arterial spin labelling (ASL) and resting-state functional MRI (rs-fMRI) scans. Psychomotor retardation was assessed with the motoric items of the core assessment of psychomotor change (CORE) questionnaire. Patients with MDD had more pronounced psychomotor retardation scores than HC. Patients with MDD had reduced CBF in bilateral cingulate motor area (CMA) and increased resting-state functional connectivity (rs-FC) between the cluster in the CMA and a cluster localized in bilateral supplementary motor areas (SMA). Furthermore, increased rs-FC between the CMA and the left SMA was associated with more pronounced psychomotor retardation. Our results suggest that reduced perfusion of the CMA and increased rs-FC between the CMA and the SMA are associated with psychomotor retardation in patients with depression.

Cerebral perfusion is not impaired in persons with moderate obstructive sleep apnoea when awake.

PURPOSE: It is well established that, together with a multitude of other adverse effects on health, severe obstructive sleep apnoea causes reduced cerebral perfusion and, in turn, reduced cerebral function. Less clear is the impact of moderate obstructive sleep apnoea (OSA). Our aim was to determine if cerebral blood flow is impaired in people diagnosed with moderate OSA. METHODS: Twenty-four patients diagnosed with moderate OSA (15 ≤ apnoea-hypopnea index (AHI) < 30) were recruited (aged 32-72, median 59 years, 10 female). Seven controls (aged 42-73 years, median 62 years, 4 female) with an AHI < 5 were also recruited. The OSA status of all participants was confirmed at baseline by unattended polysomnography and they had an MRI arterial-spin-labelling scan of cerebral perfusion. RESULTS: Neither global perfusion nor voxel-wise perfusion differed significantly between the moderate-OSA and control groups. We also compared the average perfusion across three regional clusters, which had been found in a previous study to have significant perfusion differences with moderate-severe OSA versus control, and found no significant difference in perfusion between the two groups. The perfusions were also very close, with means of 50.2 and 51.8 mL/100 g/min for the moderate-OSAs and controls, respectively, with a negligible effect size (Cohen's d = 0.10). CONCLUSION: We conclude that cerebral perfusion is not impaired in people with moderate OSA and that cerebral flow regulatory mechanisms can cope with the adverse effects which occur in moderate OSA. This is an important factor in clinical decisions for prescription of continuous positive airway pressure therapy (CPAP).

Evaluation of the effect of intraventricular haemorrhage on cerebral perfusion in preterm neonates using three-dimensional pseudo-continuous arterial spin labelling.

BACKGROUND: Intraventricular haemorrhage (IVH) often arises as a cerebral complication directly related to preterm birth. The impaired autoregulation of cerebral blood flow is closely associated with IVH in preterm neonates. Three-dimensional pseudo-continuous arterial spin labelling (3D-pCASL) is a noninvasive magnetic resonance imaging (MRI) technique used for evaluating cerebral perfusion. OBJECTIVE: This study aimed to compare cerebral blood flow values among three distinct groups using 3D-pCASL: preterm neonates with and without IVH and preterm neonates at term-equivalent age. MATERIALS AND METHODS: A total of 101 preterm neonates who underwent conventional MRI and 3D-pCASL were included in this study. These neonates were categorised into three groups: 12 preterm neonates with IVH, 52 preterm neonates without IVH, and 37 healthy neonates at term-equivalent age. Cerebral blood flow measurements were obtained from six brain regions of interest (ROIs)-the frontal lobe, temporal lobe, parietal lobe, occipital lobe, basal ganglia, and thalamus-in the right and left hemispheres. RESULTS: The cerebral blood flow values measured in all ROIs of preterm neonates with IVH were significantly lower than those of neonates at term-equivalent age (all P<0.05). Additionally, the cerebral blood flow in the temporal lobe was lower in preterm neonates without IVH than in neonates at term-equivalent age (16.87±5.01 vs. 19.76±5.47 ml/100 g/min, P=0.012). Furthermore, a noteworthy positive correlation was observed between post-menstrual age and cerebral blood flow in the temporal lobe (P=0.037), basal ganglia (P=0.010), and thalamus (P=0.010). CONCLUSION: The quantitative cerebral blood flow values, as measured by 3D-pCASL, highlighted that preterm neonates with IVH had decreased cerebral perfusion. This finding underscores the potential of 3D-pCASL as a technique for evaluating the developmental aspects of the brain in preterm neonates.

Connectivity of the insular subdivisions differentiates posttraumatic headache-associated from nonheadache-associated mild traumatic brain injury: an arterial spin labelling study.

OBJECTIVE: The insula is an important part of the posttraumatic headache (PTH) attributed to mild traumatic brain injury (mTBI) neuropathological activity pattern. It is composed of functionally different subdivisions and each of which plays different role in PTH neuropathology. METHODS: Ninety-four mTBI patients were included in this study. Based on perfusion imaging data obtained from arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI), this study evaluated the insular subregion perfusion-based functional connectivity (FC) and its correlation with clinical characteristic parameters in patients with PTH after mTBI and non-headache mTBI patients. RESULTS: The insular subregions of mTBI + PTH (mTBI patients with PTH) and mTBI-PTH (mTBI patients without PTH) group had positive perfusion-based functional connections with other insular nuclei and adjacent discrete cortical regions. Compared with mTBI-PTH group, significantly increased resting-state perfusion-based FC between the anterior insula (AI) and middle cingulate cortex (MCC)/Rolandic operculum (ROL), between posterior insula (PI) and supplementary motor area (SMA), and decreased perfusion-based FC between PI and thalamus were found in mTBI + PTH group. Changes in the perfusion-based FC of the left posterior insula/dorsal anterior insula with the thalamus/MCC were significant correlated with headache characteristics. CONCLUSIONS: Our findings provide new ASL-based evidence for changes in the perfusion-based FC of the insular subregion in PTH patients attributed to mTBI and the association with headache features, revealing the possibility of potential neuroplasticity after PTH. These findings may contribute to early diagnosis of the disease and follow-up of disease progression.

Blood-brain barrier water exchange measurements using contrast-enhanced ASL.

A technique for quantifying regional blood-brain barrier (BBB) water exchange rates using contrast-enhanced arterial spin labelling (CE-ASL) is presented and evaluated in simulations and in vivo. The two-compartment ASL model describes the water exchange rate from blood to tissue, k b , but to estimate k b in practice it is necessary to separate the intra- and extravascular signals. This is challenging in standard ASL data owing to the small difference in T 1 values. Here, a gadolinium-based contrast agent is used to increase this T 1 difference and enable the signal components to be disentangled. The optimal post-contrast blood T 1 ( T 1 , b post ) at 3 T was determined in a sensitivity analysis, and the accuracy and precision of the method quantified using Monte Carlo simulations. Proof-of-concept data were acquired in six healthy volunteers (five female, age range 24-46 years). The sensitivity analysis identified the optimal T 1 , b post at 3 T as 0.8 s. Simulations showed that k b could be estimated in individual cortical regions with a relative error ϵ < 1 % and coefficient of variation CoV = 30 %; however, a high dependence on blood T 1 was also observed. In volunteer data, mean parameter values in grey matter were: arterial transit time t A = 1 . 15 ± 0 . 49 s, cerebral blood flow f = 58 . 0 ± 14 . 3 mL blood/min/100 mL tissue and water exchange rate k b = 2 . 32 ± 2 . 49 s-1 . CE-ASL can provide regional BBB water exchange rate estimates; however, the clinical utility of the technique is dependent on the achievable accuracy of measured T 1 values.

Reduced cortical cerebral blood flow in antipsychotic-free first-episode psychosis and relationship to treatment response.

BACKGROUND: Altered cerebral blood flow (CBF) has been found in people at risk for psychosis, with first-episode psychosis (FEP) and with chronic schizophrenia (SCZ). Studies using arterial spin labelling (ASL) have shown reduction of cortical CBF and increased subcortical CBF in SCZ. Previous studies have investigated CBF using ASL in FEP, reporting increased CBF in striatum and reduced CBF in frontal cortex. However, as these people were taking antipsychotics, it is unclear whether these changes are related to the disorder or antipsychotic treatment and how they relate to treatment response. METHODS: We examined CBF in FEP free from antipsychotic medication (N = 21), compared to healthy controls (N = 22). Both absolute and relative-to-global CBF were assessed. We also investigated the association between baseline CBF and treatment response in a partially nested follow-up study (N = 14). RESULTS: There was significantly lower absolute CBF in frontal cortex (Cohen's d = 0.84, p = 0.009) and no differences in striatum or hippocampus. Whole brain voxel-wise analysis revealed widespread cortical reductions in absolute CBF in large cortical clusters that encompassed occipital, parietal and frontal cortices (Threshold-Free Cluster Enhancement (TFCE)-corrected <0.05). No differences were found in relative-to-global CBF in the selected region of interests and in voxel-wise analysis. Relative-to-global frontal CBF was correlated with percentage change in total Positive and Negative Syndrome Scale after antipsychotic treatment (r = 0.67, p = 0.008). CONCLUSIONS: These results show lower cortical absolute perfusion in FEP prior to starting antipsychotic treatment and suggest relative-to-global frontal CBF as assessed with magnetic resonance imaging could potentially serve as a biomarker for antipsychotic response.

Arterial spin labeling MRI applied to migraine: current insights and future perspectives.

INTRODUCTION: Advanced neuroimaging techniques have extensively contributed to elucidate the complex mechanisms underpinning the pathophysiology of migraine, a neurovascular disorder characterized by episodes of headache associated with a constellation of non-pain symptoms. The present manuscript, summarizing the most recent progresses of the arterial spin labelling (ASL) MRI techniques and the most significant findings from ASL studies conducted in migraine, is aimed to clarify how ASL investigations are contributing to the evolving insight on migraine pathophysiology and their putative role in migraine clinical setting. ASL techniques, allowing to quantitatively demonstrate changes in cerebral blood flow (CBF) both during the attacks and in the course of interictal period, could represent the melting point between advanced neuroimaging investigations, conducted with pure scientific purposes, and conventional neuroimaging approaches, employed in the diagnostic decision-making processes. MAIN BODY: Converging ASL evidences have demonstrated that abnormal CBF, exceeding the boundaries of a single vascular territory, with biphasic trend dominated by an initial hypoperfusion (during the aura phenomenon but also in the first part of the headache phase) followed by hyperperfusion, characterizes migraine with aura attack and can represent a valuable clinical tool in the differential diagnosis from acute ischemic strokes and epileptic seizures. Studies conducted during migraine without aura attacks are converging to highlight the involvement of dorsolateral pons and hypothalamus in migraine pathophysiology, albeit not able to disentangle their role as "migraine generators" from mere attack epiphenomenon. Furthermore, ASL findings tend to support the presence of perfusion abnormalities in brain regions known to be involved in aura ignition and propagation as well as in areas involved in multisensory processing, in both patients with migraine with aura and migraine without aura. CONCLUSION: Although ASL studies have dramatically clarified quality and timing of perfusion abnormalities during migraine with aura attacks, the same cannot be said for perfusion changes during migraine attacks without aura and interictal periods. Future studies with more rigorous methodological approaches in terms of study protocol, ASL technique and sample selection and size are mandatory to exploit the possibility of better understanding migraine pathophysiology and identifying neuroimaging biomarkers of each migraine phase in different migraine phenotypes.

Neurotransmitter receptor densities are associated with changes in regional Cerebral blood flow during clinical ongoing pain.

Arterial spin labelling (ASL) plays an increasingly important role in neuroimaging pain research but does not provide molecular insights regarding how regional cerebral blood flow (rCBF) relates to underlying neurotransmission. Here, we integrate ASL with positron emission tomography (PET) and brain transcriptome data to investigate the molecular substrates of rCBF underlying clinically relevant pain states. Two data sets, representing acute and chronic ongoing pain respectively, were utilised to quantify changes in rCBF; one examining pre-surgical versus post-surgical pain, and the second comparing patients with painful hand Osteoarthritis to a group of matched controls. We implemented a whole-brain spatial correlation analysis to explore associations between change in rCBF (ΔCBF) and neurotransmitter receptor distributions derived from normative PET templates. Additionally, we utilised transcriptomic data from the Allen Brain Atlas to inform distributions of receptor expression. Both datasets presented significant correlations of ΔCBF with the µ-opioid and dopamine-D2 receptor expressions, which play fundamental roles in brain activity associated with pain experiences. ΔCBF also correlated with the gene expression distributions of several receptors involved in pain processing. Overall, this is the first study illustrating the molecular basis of ongoing pain ASL indices and emphasises the potential of rCBF as a biomarker in pain research.

Future of kidney imaging: Functional magnetic resonance imaging and kidney disease progression.

INTRODUCTION: Chronic kidney disease (CKD) which is a common cause of death has an increasing trend, but there is no established approach for predicting CKD progression yet. Functional magnetic resonance imaging (fMRI) studies such as blood oxygenation level-dependent MRI (BOLD-MRI), diffusion-weighted MRI (DWI-MRI), diffusion-tensor MRI (DTI-MRI) and arterial spin labelling MRI (ASL-MRI) are rising methods for the assessment of kidney functions in native and transplanted kidneys as well as the estimation of CKD progression. METHODS: Systematic literature review was performed through the Embase (Elsevier), Cochrane Central Register of Controlled Trials (Wiley), PubMed/Medline and Web of Science databases, and studies investigating the role of fMRI methods assessing kidney functions in native and transplanted kidneys, as well as the value of fMRI methods to predict CKD progression, were included. Working mechanisms, advantages and limitations of the fMRI modalities were reviewed, and three studies investigating the role of fMRI studies in kidney functions were analysed. RESULTS AND CONCLUSION: BOLD-MRI signal was found to be inversely correlated with annual eGFR change, and DWI/ADC (apparent diffusion coefficient map) values were shown to be correlated with annual eGFR decline. fMRI methods which are currently used for other systems can be utilized to provide more detailed information about kidney functions, and doctors should be ready to interpret kidney MRIs.

"Trapped labelled spins"-related signal on arterial spin labelling in the assessment of flow-diverted aneurysms: preliminary experience.

PURPOSE: To investigate ASL-MRI features of flow-diverted aneurysms, review their haemodynamic surrogates, and discuss their pertinent clinical implications. METHODS: Retrospective single institutional analysis was performed on the clinical and imaging data of patients who underwent digital subtraction angiography (DSA) and ASL-MRI after endovascular flow diversion for cerebral aneurysms. Pseudo-continuous ASL-MRI was performed with post-label delays of 1525-1800 ms. Intra-aneurysmal "trapped labelled spins" (TLS)-related hypersignal, as seen on cerebral blood flow (CBF)-weighted maps of ASL-MRI, was investigated. Intermodality equivalence with DSA [O'Kelly-Marotta (OKM) grading for occlusion], 3D-TOF-MRA, and 3D spin-echo T1-weighted ("black-blood") images was assessed. RESULTS: Ten cases were included. "TLS" signal was demonstrable in 7/8 (87.5%) of the DSA-visible flow-diverted aneurysms (OKM grade B3, n = 6; OKM grade A3, n = 2). No TLS was seen in both OKM-D (excluded) aneurysms. TLS was not visualised in an OKM-B3 aneurysm with < 3 mm opacifying remnant. 3D-TOF-MRA and ASL-MRI were discordant at 5 instances (45.4%; TOF-MRA false negative, n = 4; false positive, n = 1). Loss of flow void on black-blood images corresponded to the absence of TLS and vice versa in all cases but one. CONCLUSION: "Trapped labelled spins"-related signal on ASL-MRI occurs in patent large aneurysms that have undergone successful endovascular flow diversion. This phenomenon likely represents an interplay of a multitude of haemodynamic factors including decelerated intra-aneurysmal inflow and outflow restriction. Serial intra-saccular TLS signal changes may hold diagnostic value, including contexts where 3D-TOF-MRA interpretation becomes dubious. "Trapped labelled spins"-related signal as a non-invasive proxy marker of aneurysm patency can possibly obviate unnecessary DSA.

Repeatability of perfusion measurements in adult gliomas using pulsed and pseudo-continuous arterial spin labelling MRI.

OBJECTIVES: To investigate the repeatability of perfusion measures in gliomas using pulsed- and pseudo-continuous-arterial spin labelling (PASL, PCASL) techniques, and evaluate different regions-of-interest (ROIs) for relative tumour blood flow (rTBF) normalisation. MATERIALS AND METHODS: Repeatability of cerebral blood flow (CBF) was measured in the Contralateral Normal Appearing Hemisphere (CNAH) and in brain tumours (aTBF). rTBF was normalised using both large/small ROIs from the CNAH. Repeatability was evaluated with intra-class-correlation-coefficient (ICC), Within-Coefficient-of-Variation (WCoV) and Coefficient-of-Repeatability (CR). RESULTS: PASL and PCASL demonstrated high reliability (ICC > 0.9) for CNAH-CBF, aTBF and rTBF. PCASL demonstrated a more stable signal-to-noise ratio (SNR) with a lower WCoV of the SNR than that of PASL (10.9-42.5% vs. 12.3-29.2%). PASL and PCASL showed higher WCoV in aTBF and rTBF than in CNAH CBF in WM and GM but not in the caudate, and higher WCoV for rTBF than for aTBF when normalised using a small ROI (PASL 8.1% vs. 4.7%, PCASL 10.9% vs. 7.9%, respectively). The lowest CR was observed for rTBF normalised with a large ROI. DISCUSSION: PASL and PCASL showed similar repeatability for the assessment of perfusion parameters in patients with primary brain tumours as previous studies based on volunteers. Both methods displayed reasonable WCoV in the tumour area and CNAH. PCASL's more stable SNR in small areas (caudate) is likely to be due to the longer post-labelling delays.

Perfusion imaging of neuroblastoma and nephroblastoma in a paediatric population using pseudo-continuous arterial spin-labelling magnetic resonance imaging.

OBJECTIVES: To examine the feasibility of performing ASL-MRI in paediatric patients with solid abdominal tumours. METHODS: Multi-delay ASL data sets were acquired in ten paediatric patients diagnosed with either a neuroblastoma (n = 4) or nephroblastoma (n = 6) during a diagnostic MRI examination at a single visit (n = 4 at initial staging, n = 2 neuroblastoma and n = 2 nephroblastoma patients; n = 6 during follow-up, n = 2 neuroblastoma and n = 4 nephroblastoma patients). Visual evaluation and region-of-interest (ROI) analyses were performed on the processed perfusion-weighted images to assess ASL perfusion signal dynamics in the whole tumour, contralateral kidney, and tumour sub-regions with/without contrast enhancement. RESULTS: The majority of the included abdominal tumours presented with relatively low perfusion-weighted signal (PWS), especially compared with the highly perfused kidneys. Within the tumours, regions with high PWS were observed which, at short PLD, are possibly related to labelled blood inside vessels and at long PLD, reflect labelled blood accumulating inside tumour tissue over time. Conversely, comparison of ASL perfusion-weighted image findings with T1w enhancement after contrast administration showed that regions lacking contrast enhancement also were void of PWS. DISCUSSION: This pilot study demonstrates the feasibility of utilizing ASL-MRI in paediatric patients with solid abdominal tumours and provides a basis for further research on non-invasive perfusion measurements in this study population.

Cerebral perfusion changes of the basal ganglia and thalami in full-term neonates with hypoxic-ischaemic encephalopathy: a three-dimensional pseudo continuous arterial spin labelling perfusion magnetic resonance imaging study.

BACKGROUND: Neonatal hypoxic-ischemic encephalopathy (HIE) is one of the common causes of neurological injury in full-term neonates following perinatal asphyxia. The conventional magnetic resonance technique has low sensitivity in detecting variations in cerebral blood flow in patients with HIE. OBJECTIVE: This article evaluates the clinical diagnostic value of three-dimensional pseudo-continuous arterial spin labelling (3-D pcASL) perfusion magnetic resonance imaging (MRI) for early prediction of neurobehavioral outcomes in full-term neonates with HIE. MATERIALS AND METHODS: All neonates diagnosed with HIE underwent MRI (conventional and 3-D pcASL perfusion MRI). Cerebral blood flow values were measured in the basal ganglia (caudate nuclei, lenticular nuclei), thalami and white matter regions (frontal lobes, corona radiata). After 1-month follow-up, the Neonatal Behavioral Neurological Assessment scores were used to divide patients into favourable outcome group versus adverse outcome group. RESULTS: Twenty-three patients were enrolled in this study. There were no statistical differences between the symmetrical cerebral blood flow values of bilateral basal ganglia, thalami and white matter regions. However, the cerebral blood flow values of grey matter nuclei were higher than the white matter regions. The average value of cerebral blood flow in the basal ganglia and thalami in the adverse outcome group was 37.28±6.42 ml/100 g/min, which is greater than the favourable outcome group (22.55 ± 3.21 ml/100 g/min) (P<0.01). The area under the curve (AUC) of 3-D pcASL perfusion MRI was 0.992 with a cutoff value of 28.75 ml/100 g/min, with a Youden's index of 0.9231. The sensitivity and specificity were 92.3% and 100%, respectively. CONCLUSION: The 3-D pcASL demonstrated higher perfusion alteration in the basal ganglia and thalami of neonatal HIE with adverse outcomes. The 3-D pcASL perfusion MRI has the potential to predict neurobehavioral outcomes of neonates with HIE.

Hypoperfusion in nucleus accumbens in chronic migraine using 3D pseudo-continuous arterial spin labeling imaging MRI.

BACKGROUND: Nucleus accumbens (NAcc) played an important role in pain mediation, and presents changes of neuronal plasticity and functional connectivity. However, less is known about altered perfusion of NAcc in chronic migraine (CM). The aim of this study is to investigate the altered perfusion of the NAcc in CM using a MR three-dimensional pseudo-continuous arterial spin labeling (3D PCASL) imaging. METHODS: Thirteen CM patients and 15 normal controls (NC) were enrolled and underwent 3D PCASL and brain structural imaging. The cerebral blood flow (CBF) images were co-registered with the brain structural images, and the volume and CBF value of NAcc were extracted from the raw brain structural images and co-registered CBF images using an individual NAcc mask, which was obtained from the AAL3 template under transformation by the inverse deformation field generated from the segmentation of the brain structural images. The independent sample t test and receiver operating characteristic (ROC) curve was used to investigate the altered volume and perfusion of the NAcc in CM patients. RESULTS: There was no significant difference for the volume of bilateral NAccs between CM and NC (p > 0.05). CM presented a lower CBF value (49.34 ± 6.09 ml/100 mg/min) compared with that of NC (55.83 ± 6.55 ml/100 mg/min) in left NAcc (p = 0.01), while right NAcc showed no significant difference between CM and NC (p = 0.11). ROC analysis identified that the area under the curve was 0.73 (95CI% 0.53-0.88) with cut-off value 48.63 ml/100 mg/min with sensitivity 50.00% and specificity 93.33%. The correlation analysis found a negative correlation between the CBF value of the left NAcc and VAS score (r = -0.61, p = 0.04). CONCLUSION: Hypoperfusion of the left NAcc was observed in CM, which could be considered as a potential diagnostic imaging biomarker in CM.

Age-related normative changes in cerebral perfusion: Data from The Irish Longitudinal Study on Ageing (TILDA).

OBJECTIVE: To establish normative reference values for total grey matter cerebral blood flow (CBFGM) measured using pseudo-continuous arterial spin labelling (pCASL) MRI in a large cohort of community-dwelling adults aged 54 years and older. BACKGROUND: Quantitative assessment of CBFGM may provide an imaging biomarker for the early detection of those at risk of neurodegenerative diseases, such as Alzheimer's and dementia. However, the use of this method to differentiate normal age-related decline in CBFGM from pathological reduction has been hampered by the lack of reference values for cerebral perfusion. METHODS: The study cohort comprised a subset of wave 3 (2014-2015) participants from The Irish Longitudinal Study on Ageing (TILDA), a large-scale prospective cohort study of individuals aged 50 and over. Of 4309 participants attending for health centre assessment, 578 individuals returned for 3T multi-parametric MRI brain examinations. In total, CBFGM data acquired from 468 subjects using pCASL-MRI were included in this analysis. Normative values were estimated using Generalised Additive Models for Location Shape and Scale (GAMLSS) and are presented as percentiles, means and standard deviations. RESULTS: The mean age of the cohort was 68.2 ± 6.9 years and 51.7% were female. Mean CBFGM for the cohort was 36.5 ± 8.2 ml/100 g/min. CBFGM decreased by 0.2 ml/100 g/min for each year increase in age (95% CI = -0.3, -0.1; p ≤ 0.001) and was 3.1 ml/100 g/min higher in females (95% CI = 1.6, 4.5; p ≤ 0.001). CONCLUSIONS: This study is by far the largest single-site study focused on an elderly community-dwelling cohort to present normative reference values for CBFGM measured at 3T using pCASL-MRI. Significant age- and sex-related differences exist in CBFGM.

Pharmacological MRI with Simultaneous Measurement of Cerebral Perfusion and Blood-Cerebrospinal Fluid Barrier Function using Interleaved Echo-Time Arterial Spin Labelling.

Pharmacological MRI (phMRI) studies seek to capture changes in brain haemodynamics in response to a drug. This provides a methodological platform for the evaluation of novel therapeutics, and when applied to disease states, may provide diagnostic or mechanistic information pertaining to common brain disorders such as dementia. Changes to brain perfusion and blood-cerebrospinal fluid barrier (BCSFB) function can be probed, non-invasively, by arterial spin labelling (ASL) and blood-cerebrospinal fluid barrier arterial spin labelling (BCSFB-ASL) MRI respectively. Here, we introduce a method for simultaneous recording of pharmacological perturbation of brain perfusion and BCSFB function using interleaved echo-time ASL, applied to the anesthetized mouse brain. Using this approach, we capture an exclusive decrease in BCSFB-mediated delivery of arterial blood water to ventricular CSF, following anti-diuretic hormone, vasopressin, administration. The commonly used vasodilatory agent, CO2, induced similar increases (~21%) in both cortical perfusion and the BCSFB-ASL signal. Furthermore, we present evidence that caffeine administration triggers a marked decrease in BCSFB-mediated labelled water delivery (41%), with no significant changes in cortical perfusion. Finally, we demonstrate a marked decrease in the functional response of the BCSFB to, vasopressin, in the aged vs adult brain. Together these data, the first of such kind, highlight the value of this translational approach to capture simultaneous and differential pharmacological modulation of vessel tone at the blood brain barrier and BCSFB and how this relationship may be modified in the ageing brain.