Arterial Spin Labeling MRI Research Articles

Cerebral blood flow patterns in preterm and term neonates assessed with pseudo-continuous arterial spin labeling perfusion MRI.

In preterm (PT) infants, regional cerebral blood flow (CBF) disturbances may predispose to abnormal brain maturation even without overt brain injury. Therefore, it would be informative to determine the spatial distribution of grey matter (GM) CBF in PT and full-term (FT) newborns at term-equivalent age (TEA) and to assess the relationship between the features of the CBF pattern and both prematurity and prematurity-related brain lesions. In this prospective study, we obtained measures of CBF in 66 PT (51 without and 15 with prematurity-related brain lesions) and 38 FT newborns through pseudo-continuous arterial spin labeling (pCASL) MRI acquired at TEA. The pattern of GM CBF was characterized by combining an atlas-based automated segmentation of structural MRI with spatial normalization and hierarchical clustering. The effects of gestational age (GA) at birth and brain injury on the CBF pattern were investigated. We identified 4 physiologically-derived clusters of brain regions that were labeled Fronto-Temporal, Parieto-Occipital, Insular-Deep GM (DGM) and Sensorimotor, from the least to the most perfused. We demonstrated that GM perfusion was associated with GA at birth in the Fronto-Temporal and Sensorimotor clusters, positively and negatively, respectively. Moreover, the presence of periventricular leukomalacia was associated with significantly increased Fronto-Temporal GM perfusion and decreased Insular-DGM perfusion, while the presence of germinal matrix hemorrhage appeared to mildly decrease the Insular-DGM perfusion. Prematurity and prematurity-related brain injury heterogeneously affect brain perfusion. ASL MRI may, therefore, have strong potential as a noninvasive tool for the accurate stratification of individuals at risk of domain-specific impairment.

Delay in Clearance of Labeled Protons in Patients with Acute Head Trauma Utilizing MRI 3D TGSE PASL MRI (Arterial Spin Labeling) (P8-1.007)

<h3>Objective:</h3> The aims of this study are: to use delayed glymphatic clearance (GC)/capillary transit time (CTT) as a tool to measure change in brain function following acute traumatic brain injury (aTBI) to assess whether flow improves when patients are cleared clinically to return to their respective sport. <h3>Background:</h3> Acute TBI is thought to accompany neuroinflammation with disruption of the blood-brain barrier (BBB) and GC/CTT. Currently, concussion is largely a clinical diagnosis utilizing subjective questionnaires as supplemental aids; however, 3D TGSE MRI PASL may serve as an objective way to assess brain health by measuring changes in GC. <h3>Design/Methods:</h3> 3D TGSE PASL MRI with long T1s was used to assess the clearance of ultra-filtered labeled protons 2800–4000 ms post-perfusion in frontal, temporal and parietal regions bilaterally following acute traumatic brain injury within 7 days of injury and when cleared to return to sport. The Sport Concussion Assessment Tool Version 5 (SKAT5) and Brief Oculomotor/Vestibular Assessment were used as cognitive adjuncts to MRI protocol. Subjects fulfilled the clinical diagnostic criteria for mild aTBI. <h3>Results:</h3> Comparing intrasubject results at acute injury versus post-recovery, along with age-and-activity matched controls, we found reduced GC/CTT in select damaged brain regions. Although preliminary statistical analysis is pending, the reduction in clearance among post-aTBI groups based on current linear regression analysis presents a strong trend that will be explored further as we increase our sample size. <h3>Conclusions:</h3> Acute TBI disrupts the BBB and subsequently reduces GC/CTT, allowing inflammatory/toxic substances to remain in the neuropil. In this ongoing pilot study, we have observed reduced signal clearance in our concussive head trauma subjects compared to their recovery scan. This technique may provide a potentially reliable biomarker of acute changes and subsequent recovery following aTBI. <b>Disclosure:</b> Ms. Kang has nothing to disclose. Ms. Zivcevska has nothing to disclose. Mr. Grohol has nothing to disclose. Mr. Clark has nothing to disclose. Mr. Dorman has nothing to disclose. Mr. Lencke has nothing to disclose. Mr. Arrasmith has nothing to disclose. Mr. Kim has nothing to disclose. An immediate family member of Mr. Rich has received personal compensation for serving as an employee of Centra . Dr. Joseph has nothing to disclose.

Case Report: Zolpidem's paradoxical restorative action: A case report of functional brain imaging.

Zolpidem is a sedative drug that has been shown to induce a paradoxical effect, restoring brain function in wide range of neurological disorders. The underlying functional mechanism of the effect of zolpidem in the brain in clinical improvement is still poorly understood. Thus, we aimed to investigate rest brain function to study zolpidem-induced symptom improvement in a patient who developed postoperative pediatric cerebellar mutism syndrome, a postoperative complication characterized by delayed onset transient mutism/reduced speech that can occur after medulloblastoma resection. The patient experienced clinical recovery after a single dose of zolpidem. Brain function was investigated using arterial spin labeling MRI and resting-state functional MRI. Imaging was performed at three time-points: preoperative, postoperative during symptoms, and after zolpidem intake when the symptoms regressed. Whole brain rest cerebral blood flow (CBF) and resting state functional connectivity using Pearson coefficient correlations between pairs of regions of interest were investigated two-by-two at the different time points. A comparison between postoperative and preoperative images showed a significant decrease in rest CBF in the left supplementary motor area, Broca's area, and the left striatum and a decrease in functional connectivity within the dentato-thalamo-cortical and cortico-striato-pallido-thalamo-cortical loops. Post-zolpidem images showed increased CBF in the left striatum and increased functional connectivity within the disrupted loops relative to postoperative images. Thus, we observed functional changes within the broader speech network and thalamo-subcortical interactions associated with the paradoxical effect of zolpidem in promoting clinical recovery. This should encourage further functional investigations in the brain to better understand the mechanism of zolpidem in neurological recovery.

White-Matter Lesions and Cortical Cerebral Blood Flow Evaluation by 3D Arterial Spin-Labeled Perfusion MRI in Asymptomatic Divers: Correlation with Patent Foramen Ovale Ocurrence.

Cerebral white-matter lesions (cWML) can be caused by dilation of Virchow-Robin spaces or may correspond to true lacunar ischemic lesions. The aim of our study was to evaluate in asymptomatic divers the relationship between the presence of patent foramen ovale (PFO) and cWML, as well as their possible effects on cortical cerebral blood flow (CBF) by magnetic resonance (MRI) through the arterial spin labeling (ASL) sequence. Transthoracic echocardiography was performed for the identification of PFO, and cerebral magnetic resonance including the 3D-ASL sequence for CBF quantification. Thirty-eight divers, with a mean age 45.8 ± 8.6 years, were included. Nineteen healthy volunteers, mean age 41 ± 15.2 years, served as the control group. A total of 28.9% of divers had completed more than 1000 dives. It was found that 26.3% of divers presented with PFO in the echocardiographic study. cWML was evidenced in 10.5% of diver MRI studies. There was no statistically significant relationship between the presence of PFO and cWML (p = 0.95). We observed a lower blood flow in all brain areas assessed by the 3D-ASL sequence in the group of divers, compared with the control group. We did not find statistical differences in CBF as a function of the presence or absence of PFO, number of dives, or cWML evidence.

Cerebral hypoperfusion in post-COVID-19 cognitively impaired subjects revealed by arterial spin labeling MRI

Cognitive impairment is one of the most prevalent symptoms of post Severe Acute Respiratory Syndrome COronaVirus 2 (SARS-CoV-2) state, which is known as Long COVID. Advanced neuroimaging techniques may contribute to a better understanding of the pathophysiological brain changes and the underlying mechanisms in post-COVID-19 subjects. We aimed at investigating regional cerebral perfusion alterations in post-COVID-19 subjects who reported a subjective cognitive impairment after a mild SARS-CoV-2 infection, using a non-invasive Arterial Spin Labeling (ASL) MRI technique and analysis. Using MRI-ASL image processing, we investigated the brain perfusion alterations in 24 patients (53.0 ± 14.5 years, 15F/9M) with persistent cognitive complaints in the post COVID-19 period. Voxelwise and region-of-interest analyses were performed to identify statistically significant differences in cerebral blood flow (CBF) maps between post-COVID-19 patients, and age and sex matched healthy controls (54.8 ± 9.1 years, 13F/9M). The results showed a significant hypoperfusion in a widespread cerebral network in the post-COVID-19 group, predominantly affecting the frontal cortex, as well as the parietal and temporal cortex, as identified by a non-parametric permutation testing (p < 0.05, FWE-corrected with TFCE). The hypoperfusion areas identified in the right hemisphere regions were more extensive. These findings support the hypothesis of a large network dysfunction in post-COVID subjects with cognitive complaints. The non-invasive nature of the ASL-MRI method may play an important role in the monitoring and prognosis of post-COVID-19 subjects.

The identification and cognitive correlation of perfusion patterns measured with arterial spin labeling MRI in Alzheimer’s disease

BackgroundVascular dysfunction, including cerebral hypoperfusion, plays an important role in the pathogenesis and progression of Alzheimer’s disease (AD), independent of amyloid and tau pathology. We established an AD-related perfusion pattern (ADRP) measured with arterial spin labeling (ASL) MRI using multivariate spatial covariance analysis.MethodsWe obtained multimodal MRI including pseudo-continuous ASL and neurocognitive testing in a total of 55 patients with a diagnosis of mild to moderate AD supported by amyloid PET and 46 normal controls (NCs). An ADRP was established from an identification cohort of 32 patients with AD and 32 NCs using a multivariate analysis method based on scaled subprofile model/principal component analysis, and pattern expression in individual subjects was quantified for both the identification cohort and a validation cohort (23 patients with AD and 14 NCs). Subject expression score of the ADRP was then used to assess diagnostic accuracy and cognitive correlations in AD patients and compared with global and regional cerebral blood flow (CBF) in specific areas identified from voxel-based univariate analysis.ResultsThe ADRP featured negative loading in the bilateral middle and posterior cingulate and precuneus, inferior parietal lobule, and frontal areas, and positive loading in the right cerebellum and bilateral basal areas. Subject expression score of the ADRP was significantly elevated in AD patients compared with NCs (P < 0.001) and showed good diagnostic accuracy for AD with area under receiver–operator curve of 0.87 [95% CI (0.78–0.96)] in the identification cohort and 0.85 in the validation cohort. Moreover, there were negative correlations between subject expression score and global cognitive function and performance in various cognitive domains in patients with AD. The characteristics of the ADRP topography and subject expression scores were supported by analogous findings obtained with regional CBF.ConclusionsWe have reported a characteristic perfusion pattern associated with AD using ASL MRI. Subject expression score of this spatial covariance pattern is a promising MRI biomarker for the identification and monitoring of AD.

Transcranial focused ultrasound selectively increases perfusion and modulates functional connectivity of deep brain regions in humans.

Low intensity, transcranial focused ultrasound (tFUS) is a re-emerging brain stimulation technique with the unique capability of reaching deep brain structures non-invasively. We sought to demonstrate that tFUS can selectively and accurately target and modulate deep brain structures in humans important for emotional functioning as well as learning and memory. We hypothesized that tFUS would result in significant longitudinal changes in perfusion in the targeted brain region as well as selective modulation of BOLD activity and BOLD-based functional connectivity of the target region. In this study, we collected MRI before, simultaneously during, and after tFUS of two deep brain structures on different days in sixteen healthy adults each serving as their own control. Using longitudinal arterial spin labeling (ASL) MRI and simultaneous blood oxygen level dependent (BOLD) functional MRI, we found changes in cerebral perfusion, regional brain activity and functional connectivity specific to the targeted regions of the amygdala and entorhinal cortex (ErC). tFUS selectively increased perfusion in the targeted brain region and not in the contralateral homolog or either bilateral control region. Additionally, tFUS directly affected BOLD activity in a target specific fashion without engaging auditory cortex in any analysis. Finally, tFUS resulted in selective modulation of the targeted functional network connectivity. We demonstrate that tFUS can selectively modulate perfusion, neural activity and connectivity in deep brain structures and connected networks. Lack of auditory cortex findings suggests that the mechanism of tFUS action is not due to auditory or acoustic startle response but rather a direct neuromodulatory process. Our findings suggest that tFUS has the potential for future application as a novel therapy in a wide range of neurological and psychiatric disorders associated with subcortical pathology.

MRI assessment of cerebral perfusion in clinical trials.

Neurodegenerative mechanisms affect the brain through a variety of processes that are reflected as changes in brain structure and physiology. Although some biomarkers for these changes are well established, others are at different stages of development for use in clinical trials. One of the most challenging biomarkers to harmonize for clinical trials is cerebral blood flow (CBF). There are several magnetic resonance imaging (MRI) methods for quantifying CBF without the use of contrast agents, in particular arterial spin labeling (ASL) perfusion MRI, which has been increasingly applied in clinical trials. In this review, we present ASL MRI techniques, including strategies for implementation across multiple imaging centers, levels of confidence in assessing disease progression and treatment effects, and details of image analysis.

Cerebral blood flow in children with persisting postconcussive symptoms and posttraumatic headache at 2 weeks postconcussion.

Persisting postconcussive symptoms (pPCS), particularly headache, can significantly disrupt children's recovery and functioning. However, the underlying pathophysiology of these symptoms remains unclear. The goal in this study was to determine whether pPCS are related to cerebral blood flow (CBF) at 2 weeks postconcussion. The authors also investigated whether variations in CBF can explain the increased risk of acute posttraumatic headache (PTH) in female children following concussion. As part of a prospective, longitudinal study, the authors recruited children 5-18 years old who were admitted to the emergency department of a tertiary pediatric hospital with a concussion sustained within 48 hours of admission. Participants underwent pseudocontinuous arterial spin labeling MRI at 2 weeks postconcussion to quantify global mean gray and white matter perfusion (in ml/100 g/min). Conventional frequentist analysis and Bayesian analysis were performed. Comparison of recovered (n = 26) and symptomatic (n = 12) groups (mean age 13.15 years, SD 2.69 years; 28 male) found no differences in mean global gray and white matter perfusion at 2 weeks postconcussion (Bayes factors > 3). Although female sex was identified as a risk factor for PTH with migraine features (p = 0.003), there was no difference in CBF between female children with and without PTH. Global CBF was not associated with pPCS and female PTH at 2 weeks after pediatric concussion. These findings provide evidence against the use of CBF measured by arterial spin labeling as an acute biomarker for pediatric concussion recovery.

Hypo- and hyper-perfusion in MCI and AD identified by different ASL MRI sequences.

Arterial spin labeling (ASL) perfusion MRI has been increasingly used in Alzheimer's Disease (AD) research. However, ASL MRI sequences differ greatly in terms of arterial blood signal preparations and data acquisition strategies, both leading to a large difference of signal-to-noise ratio (SNR). It is of great translational importance to compare the several widely used ASL MRI sequences regarding sensitivity of ASL measured cerebral blood flow (CBF) for detecting the between-group difference across the AD continuum. To this end, this study compared three ASL MRI sequences in AD research, including the 2D Pulsed ASL (PASL), 3D Background Suppressed (BS) PASL, and 3D BS Pseudo-Continuous ASL (PCASL). We used data from 100 healthy and cognitively normal elderly control (NC) subjects, 75 patients with mild cognitive impairment (MCI), and 57 Alzheimer's disease (AD) subjects from the AD neuroimaging initiative (ADNI). Both cross-sectional perfusion difference and perfusion versus clinical assessment correlations were examined. The major findings included: 3D PCASL sequence identified stronger patient versus control CBF/rCBF differences than 2D PASL and 3D PASL; MCI showed reduced CBF and CBF redistribution; CBF in orbito-frontal cortex presents a new U-shape change pattern from normal aging to MCI and to AD; 3D PCASL identified a negative rCBF to memory correlation while 2D PASL showed a positive correlation.

Associations between everyday activities and arterial spin labeling‐derived cerebral blood flow: A longitudinal study in community‐dwelling elderly volunteers

Cerebral blood flow (CBF) is critical for brain metabolism and function. Age-related changes in CBF are associated with increased risk of neurocognitive disorders and vascular events such as stroke. Identifying correlates and positive modifiers of age-related changes in CBF before the emergence of incipient clinical decline may inform public health advice and clinical practice. Former research has been inconclusive regarding the association between regular physical activity and CBF, and there is a lack of studies on the association between level of everyday activities and CBF, in older adults. To investigate these relationships, 118 healthy community-dwelling adults (65-89 years) underwent pseudo-continuous arterial spin labeling (ASL) MRI, neurocognitive, physical, and activity assessments at baseline. Eighty-six participants completed a follow-up ASL MRI, on average 506 (SD=113) days after the baseline scan. Cross-sectional analysis revealed credible evidence for positive associations between time spent on low intensity physical activity and CBF in multiple cortical and subcortical regions, time spent on moderate to vigorous intensity physical activity and accumbens CBF, participation in social activity and CBF in multiple cortical regions, and between reading and thalamic CBF, indicating higher regional CBF in more active adults. Longitudinal analysis revealed anecdotal evidence for an interaction between time and baseline level of gardening on occipital and parietal CBF, and baseline reading on pallidum CBF, indicating more change in CBF in adults with lower level of activity. The findings support that malleable lifestyle factors contribute to healthy brain aging, with relevance for public health guidelines.

Altered cerebral neurovascular coupling in medication-overuse headache: A study combining multi-modal resting-state fMRI with 3D PCASL.

Structural and functional changes in the brain have been identified in individuals with medication-overuse headache (MOH) using MRI. However, it has not been clearly established whether neurovascular dysfunction occurs in MOH, which could be elucidated by examining neurovascular coupling (NVC) from the viewpoints of neuronal activity and cerebral blood flow. The aim of this study was to investigate potential alterations in NVC function of the brain in individuals with MOH using resting-state functional MRI (rs-fMRI) and 3D pseudo-continuous arterial spin labeling (3D PCASL) imaging techniques. A total of 40 patients with MOH and 32 normal controls (NCs) were recruited, and rs-fMRI and 3D PCASL data were obtained using a 3.0 T MR scanner. Standard preprocessing of the rs-fMRI data was performed to generate images representing regional homogeneity (ReHo), fractional amplitude of low-frequency fluctuation (fALFF), and degree centrality (DC); cerebral blood flow (CBF) images were generated using 3D PCASL sequence data. These functional maps were all normalized into Montreal Neurological Institute (MNI) space, and NVC was subsequently determined on the basis of Pearson correlation coefficients between the rs-fMRI maps (ReHo, fALFF, and DC) and CBF maps. The statistical significance of differences between the MOH and NC groups in terms of NVC in different brain regions was established via Z-test. Further analysis was performed to examine correlations between NVC in the brain regions with NVC dysfunction and clinical variables among patients with MOH. NVC mainly presented a negative correlation in patients with MOH and NCs. No significant difference between the two groups was detected in terms of average NVC over the entire gray matter area. However, several brain regions with significantly decreased NVC in patients with MOH compared to NCs were identified: the left orbital region of the superior frontal gyrus, the bilateral gyrus rectus, and the olfactory cortex (P < 0.05). A correlation analysis revealed that the DC of the brain regions with NVC dysfunction was significantly positively correlated with disease duration (r = 0.323, P = 0.042), and DC-CBF connectivity was negatively correlated with VAS score (r = -0.424, P = 0.035). The current study demonstrated that cerebral NVC dysfunction occurs in patients with MOH, and the NVC technique could function as a new imaging biomarker in headache research.

MRI arterial spin labeling in evaluating hemorrhagic transformation following endovascular recanalization of subacute ischemic stroke.

To investigate the value of the MRI arterial spin labeling (ASL) in evaluating the blood-brain barrier permeability of anterior circulation ischemic lesions in subacute ischemic stroke (SIS) and the risk of hemorrhage transformation (HT) after endovascular recanalization. Patients with anterior circulation SIS treated with endovascular recanalization were prospectively enrolled. The imaging presentations in the MRI ASL sequences, dynamic contrast-enhanced (DCE) sequence, and Xper CT were studied. The relative cerebral blood flow (rCBF), volume transfer constant (Ktrans), and the weighted Kappa coefficient (rKtrans) were analyzed. Among 27 eligible patients, HT occurred in 7 patients (25.92%). Patients with HT had significantly higher rCBF value (1.56 ± 0.16 vs. 1.16 ± 0.16), Ktrans, (0.08 ± 0.03 min vs. 0.03 ± 0.01 min) and rKtrans (3.02 ± 0.89 vs. 1.89 ± 0.56). The ASL imaging sequence had a high consistency with the DCE sequence and Xper CT with a high weighted Kappa coefficient of 0.91 for the DCE sequence and 0.70 for the Xper CT imaging. The DCE sequence was also highly consistent with the Xper CT in imaging classification with a high weighted Kappa coefficient of 0.78. The rCBF value in the 21 patients with the subcortical and basal ganglia infarction was significantly lower than that in the other 6 patients with the cortical infarction (1.222 ± 0.221 vs. 1.413 ± 0.259, t = 1.795, P = 0.004). The MRI ASL sequence has an important role in evaluating the blood-brain barrier permeability and the risk of hemorrhagic transformation of anterior circulation SIS following endovascular recanalization.

The spatial-temporal dynamics of pulmonary blood flow are altered in pulmonary arterial hypertension.

Global fluctuation dispersion (FDglobal), a spatial-temporal metric derived from serial images of the pulmonary perfusion obtained with MRI-arterial spin labeling, describes temporal fluctuations in the spatial distribution of perfusion. In healthy subjects, FDglobal is increased by hyperoxia, hypoxia, and inhaled nitric oxide. We evaluated patients with pulmonary arterial hypertension (PAH, 4F, aged 47 ± 15, mean pulmonary artery pressure 48 ± 7 mmHg) and healthy controls (CON, 7F, aged 47 ± 12) to test the hypothesis that FDglobal is increased in PAH. Images were acquired at ∼4-5 s intervals during voluntary respiratory gating, inspected for quality, registered using a deformable registration algorithm, and normalized. Spatial relative dispersion (RD = SD/mean) and the percent of the lung image with no measurable perfusion signal (%NMP) were also assessed. FDglobal was significantly increased in PAH (PAH = 0.40 ± 0.17, CON = 0.17 ± 0.02, P = 0.006, a 135% increase) with no overlap in values between the two groups, consistent with altered vascular regulation. Both spatial RD and %NMP were also markedly greater in PAH vs. CON (PAH RD = 1.46 ± 0.24, CON = 0.90 ± 0.10, P = 0.0004; PAH NMP = 13.4 ± 6.1%; CON = 2.3 ± 1.4%, P = 0.001 respectively) consistent with vascular remodeling resulting in poorly perfused regions of lung and increased spatial heterogeneity. The difference in FDglobal between normal subjects and patients with PAH in this small cohort suggests that spatial-temporal imaging of perfusion may be useful in the evaluation of patients with PAH. Since this MR imaging technique uses no injected contrast agents and has no ionizing radiation it may be suitable for use in diverse patient populations.NEW & NOTEWORTHY Using proton MRI-arterial spin labeling to obtain serial images of pulmonary perfusion, we show that global fluctuation dispersion (FDglobal), a metric of temporal fluctuations in the spatial distribution of perfusion, was significantly increased in female patients with pulmonary arterial hypertension (PAH) compared with healthy controls. This potentially indicates pulmonary vascular dysregulation. Dynamic measures using proton MRI may provide new tools for evaluating individuals at risk of PAH or for monitoring therapy in patients with PAH.

Free-breathing Arterial Spin Labeling MRI for the Detection of Pulmonary Embolism.

Background Arterial spin labeling (ASL) MRI can be used to assess organ perfusion but has yet to be implemented for perfusion evaluation of the lung. Purpose To evaluate pseudo-continuous ASL (PCASL) MRI for the detection of acute pulmonary embolism (PE) and its potential as an alternative to CT pulmonary angiography (CTPA). Materials and Methods Between November 2020 and November 2021, 97 patients (median age, 61 years; 48 women) with suspected PE were enrolled in this prospective study. PCASL MRI was performed within a 72-hour period following CTPA under free-breathing conditions and included three orthogonal planes. The pulmonary trunk was labeled during systole, and the image was acquired during diastole of the subsequent cardiac cycle. Additionally, multisection, coronal, balanced, steady-state free-precession imaging was carried out. Two radiologists blindly assessed overall image quality, artifacts, and diagnostic confidence (five-point Likert scale, 5 = best). Patients were categorized as positive or negative for PE, and a lobe-wise assessment in PCASL MRI and CTPA was conducted. Sensitivity and specificity were calculated on a patient level with the final clinical diagnosis serving as the reference standard. Interchangeability between MRI and CTPA was also tested with use of an individual equivalence index (IEI). Results PCASL MRI was performed successfully in all patients with high scores for image quality, artifact, and diagnostic confidence (κ ≥ .74). Of the 97 patients, 38 were positive for PE. PCASL MRI depicted PE correctly in 35 of 38 patients with three false-positive and three false-negative findings, resulting in a sensitivity of 35 of 38 patients (92% [95% CI: 79, 98]) and a specificity of 56 of 59 patients (95% [95% CI: 86, 99]). Interchangeability analysis revealed an IEI of 2.6% (95% CI: 1.2, 3.8). Conclusion Free-breathing pseudo-continuous arterial spin labeling MRI depicted abnormal lung perfusion caused by acute pulmonary embolism and may be useful as a contrast material-free alternative to CT pulmonary angiography for selected patients. German Clinical Trials Register no. DRKS00023599 © RSNA, 2023.

Vascular function in women: when studying perimenopause is peri important.

Vascular function in women: when studying perimenopause is peri important.

Effects of Post-Labeling Delay on Magnetic Resonance Evaluation of Brain Tumor Blood Flow Using Arterial Spin Labeling.

We investigated the effect of post-labeling delay (PLD) on the evaluation of brain tumor blood flow using arterial spin labeling (ASL) magnetic resonance (MR) imaging to assess the need for imaging with two PLDs. Retrospective analysis was conducted on 63 adult patients with brain tumors who underwent contrast-enhanced MR imaging including ASL imaging with PLDs of both 1525 and 2525 ms on a 1.5 T or 3 T MR unit. Blood flow was estimated in the tumors and normal-appearing brain parenchyma, and tumor blood flow was normalized by parenchymal flow. Estimates of tumor blood flow, parenchymal flow, and normalized tumor flow showed no statistically significant differences between PLDs of 1525 and 2525 ms. Close correlations between different PLDs were found, with the closest correlation for normalized tumor flow. These results were similarly observed for the 1.5 T and 3 T units. The blood flow estimates obtained using ASL MR imaging in patients with brain tumors were highly concordant between PLDs of 1525 and 2525 ms, irrespective of the magnetic field strength. It is indicated that imaging with a single, standard PLD is acceptable for ASL assessment of brain tumor perfusion and that additional imaging with a long PLD is not required.

Assessment of Arterial Transit Time and Cerebrovascular Reactivity in Moyamoya Disease by Simultaneous PET/MRI.

We investigated the relationship between MRI-arterial spin labeling (ASL) parameters and PET-cerebral blood flow (CBF)/cerebrovascular reactivity (CVR) simultaneously obtained by PET/MRI in Moyamoya disease. Twelve patients underwent 15O-water PET/MRI with the acetazolamide (ACZ) challenge test. PET-CBF and PET-CVR were measured using 15O-water PET. Pseudo-continuous ASL obtained the robust arterial transit time (ATT) and ASL-CBF estimation. ASL parameters were compared with PET-CBF and PET-CVR. Before ACZ loading, absolute and relative ASL-CBF were significantly correlated with absolute and relative PET-CBF (r = 0.44, p < 0.0001, and r = 0.55, p < 0.0001, respectively). After ACZ loading, absolute and relative ASL-CBF were significantly correlated with absolute and relative PET-CBF (r = 0.56, p < 0.001, and r = 0.75, p < 0.0001, respectively), and ΔASL-CBF was significantly correlated with ΔPET-CBF (r = 0.65, p < 0.0001). Baseline ASL-ATT had strong negative correlations with ΔPET-CBF and PET-CVR (r = -0.72, p < 0.0001, and r = -0.66, p < 0.0001, respectively). Baseline ASL-ATT of MCA territories with CVR <30% (1546 ± 79 ms) was significantly higher than that with CVR > 30% (898 ± 197 ms). ASL-ATT ratio of MCA territories with CVR < 30% (94.0 ± 10.5%) was significantly higher than that with CVR > 30% (81.4 ± 11.3%). ATT correction using multiple postlabeling delays increased the accuracy of ASL-CBF quantitation. Baseline ASL-ATT is a hemodynamic parameter and may represent an efficient alternative to PET-CVR.

Cerebral oxygen extraction fraction declines with ventricular enlargement in patients with normal pressure hydrocephalus

ObjectiveNormal pressure hydrocephalus (NPH) is a neurodegenerative disease that is potentially reversible by shunt surgery in approximately 60% of patients. Imaging may provide a means to investigate brain tissue viability and oxygen metabolism in NPH patients. MethodsOxygen extraction fraction (OEF) mapping was generated from 3D multi-echo gradient echo MRI (mGRE) data using QQ-CCTV algorithm and cerebral blood flow (CBF) using 3D arterial spin labeling (ASL) MRI data, thereby calculating the cerebral metabolic rate of oxygen (CMRO2 = CBF × OEF × [H]a) in 16 NPH patients. Regression analyses using cortical gray matter and deep gray matter regions were conducted with age, gender, CSF stroke volume and normalized ventricular volume as independent variables. ResultsOEF showed significant negative correlations with normalized brain ventricular volumes in the whole brain (p = 0.004, q = 0.01), cortical gray matter (p = 0.004, q = 0.01), caudate (p = 0.02, q = 0.04), and pallidum (p = 0.03, q = 0.04), but no significant correlation with CSF stroke volume (q > 0.05). There was no significant finding with CBF or CMRO2. ConclusionIn NPH patients, low OEF in several regions was significantly correlated with large ventricular volumes, indicating decreased tissue oxygen metabolism with increased NPH severity. OEF mapping may provide a functional understanding of neurodegeneration in NPH and may improve monitoring of disease course and treatment outcomes.

Cognitive reserve moderates the association between cerebral blood flow and language performance in older adults with mild cognitive impairment

Higher cognitive reserve (CR) may offer protection from cognitive changes associated with reduced cerebral blood flow (CBF). We investigated CR as a moderator of the effect of CBF on cognition in older adults with mild cognitive impairment (MCI; N = 46) and those who are cognitively unimpaired (CU; N = 101). Participants underwent arterial spin labeling MRI, which was used to quantify CBF in 4 a priori regions. Estimated verbal intelligence quotient (VIQ) served as a proxy for CR. Multiple linear regressions examined whether VIQ moderated associations between CBF and cognition and whether this differed by cognitive status. Outcomes included memory and language performance. There were 3-way interactions (CBF*VIQ*cognitive status) on category fluency when examining hippocampal, superior frontal, and inferior frontal CBF. Follow-up analyses revealed that, within the MCI but not CU group, there were CBF*VIQ interactions on fluency in all a priori regions examined, where there were stronger, positive associations between CBF and fluency at higher VIQ. Conclusion: In MCI, higher CR plays a role in strengthening CBF-fluency associations.