Pseudo-continuous Arterial Spin Labeling Research Articles

Noninvasive in vivo assessment of placental insufficiency using pCASL: a prospective case–control study

BackgroundArterial spin labeling is a noninvasive imaging modality that does not use contrast for evaluation of placental perfusion in the placental pathological conditions. Our study enrolled 30 pregnant females with different risk factors for developing IUGR and other 30 females with the same age group having normal pregnancy. The two groups were evaluated by free breathing arterial spin labeling magnetic resonance imaging. Image findings of pseudo-continuous arterial spin labeling were compared to color duplex Doppler ultrasound of umbilical and middle cerebral arteries.AimThe aim of the present study was to evaluate the role of pseudo-continuous arterial spin labeling in measurement of placental perfusion with quantitative analysis of regional placental blood flow.MethodsThis prospective case–control study enrolled 30 pregnant females who had different causes of placental insufficiency, and another healthy group of matched ages, all were evaluated by 2D and color duplex Doppler ultrasound, conventional non-contrast magnetic resonance imaging and MRI perfusion using arterial spin labeling technique. The study was carried out from October 2021 to October 2023.ResultsSignificant relation was found between placental perfusion values and umbilical and middle cerebral artery resistive indices as indicator for placental insufficiency with sensitivity and specificity 77.8%, 80%, respectively, for umbilical artery resistive index and 90%, 83.3%, respectively, for middle cerebral artery resistive index. While the diagnostic value of ASL perfusion was as follows, it had sensitivity = 90%, specificity = 83.3%, PPV = 84.4%, NPV = 89.3% and accuracy = 86.7%.ConclusionsASL-MRI is an excellent noninvasive in vivo MRI technique for evaluation of placental perfusion and quantitative analysis of regional placental blood flow in cases of placental insufficiency. This study supported the value of the new noninvasive MRI techniques in the elaboration of placental pathology.

Impaired insight in schizophrenia is associated with higher frontoparietal cerebral blood flow: an arterial spin labeling study

Impaired insight into illness occurs in up to 98% of patients with schizophrenia, depending on the stage of illness, and leads to negative clinical outcomes. Previous neuroimaging studies suggest that impaired insight in patients with schizophrenia may be related to structural and functional anomalies in frontoparietal brain regions. To date, limited studies have investigated the association between regional cerebral blood flow (CBF) and impaired insight in schizophrenia. Therefore, we sought to investigate the relationship between regional CBF, as measured by arterial spin labeling (ASL), and impaired insight in participants with schizophrenia. A total of 32 participants were included in the analysis. Impaired insight in patients with schizophrenia was measured using the VAGUS, Self-report (VAGUS-SR). Resting-state regional CBF was measured using pseudo-continuous ASL (pCASL) and extracted using SPM12 and REX toolbox. Whole brain analysis found that impaired insight was associated with higher regional CBF in the right angular gyrus, left supramarginal gyrus, and right superior frontal region when controlling for age, gender, smoking status, and illness severity. The results indicate that impaired insight in schizophrenia is related to regional CBF in frontoparietal areas. These neuroimaging findings can serve as therapeutic targets for intervention, such as with non-invasive brain stimulation.

Exercise-induced reductions in central command network cerebral blood flow assessed with arterial spin labeling MRI

Abstract Habitual aerobic exercise positively impacts brain health. However, less is known about the acute effects of exercise on regional cerebral blood flow (CBF). Most studies have used exercise methods that required a 10-minute or longer delay before acquiring CBF data or methods that assessed global, rather than regional, CBF. In the current feasibility study, an aerobic exercise stimulus was administered using an MRI-compatible cardio step module connected to the MRI table. This allowed participants (n = 12, mean age = 20 years) to exercise at light-to-moderate intensity while in the bore of the MRI scanner. Pseudo-continuous arterial spin labeling MRI with multiple delays was collected on a 3T Siemens MRI scanner immediately pre- and post-exercise. CBF and arterial transit time changes were examined within the central command network, which impacts motor and cardiovascular systems during exercise. Associations with perceived exertion and cardiorespiratory fitness were assessed. CBF in central command regions decreased following exercise, with greater decreases in regions associated with cardiovascular control. For example, CBF in the left insula decreased by -9.03 ± 8.69 mL/100 g/min (-11.45%, p < 0.01); CBF in the left and right rostral anterior cingulate decreased by -4.91 ± 6.08 mL/100 g/min (-6.17%, p = 0.02) and by -5.04 ± 6.34 mL/100 g/min (-7.43%, p = 0.02); and CBF in the left lateral orbitofrontal cortex decreased by -7.30 ± 8.11 mL/100 g/min (-9.50%, p = 0.01). Decreased CBF was also associated with greater ratings of perceived exertion in cardiovascular command regions, including right insula (r = -0.67, p = 0.03), medial orbitofrontal cortex (r = -0.64, p = 0.04), and lateral orbitofrontal cortex (r = -0.75, p = 0.01). The current study further demonstrates the feasibility of assessing CBF immediately following exercise using an exercise stimulus in the bore of the MRI scanner. These results contribute to a small but growing body of literature describing cerebral hemodynamics immediately following exercise.

Multiparametric MRI in Diagnosis of Parotid Gland Tumor: An Observational Study in 3-T MRI

Abstract Background Preoperative magnetic resonance imaging (MRI) has an important role in the management and prognostication of parotid gland tumors. We aim to evaluate the role of multiparametric MRI in differentiating the major subgroup of parotid tumors. Material and Methods Multiparametric MRI: T1-weighted imaging (T1WI), T2WI, diffusion-weighted imaging (DWI), pseudo-continuous arterial spin labeling (ASL) and dynamic contrast-enhanced (DCE) imaging were acquired in all patients. Apparent diffusion coefficient (ADC) values and tumor blood flow (TBF) were calculated from DWI and ASL, respectively. Ktrans, Kep, Ve, initial area under the gadolinium enhancement concentration curve (IAUGC), maximum slope, and contrast enhancement ratio (CER) were calculated from DCE-MRI perfusion. The above parameters were compared between three major subgroups of parotid gland tumors, such as non-Warthin benign tumors (NWBT), Warthin's tumors (WT), and malignant parotid tumors (MT). Results The mean ADC of MT (n = 13), WT (n = 5), and NWBT (n = 29) was 1.03 × 10−3 mm2/s, 0.97 × 10−3 mm2/s, and 1.89 × 10−3 mm2/s, respectively. The mean TBF (in mL/100 g/min) was the highest MT (70.33), followed by WT (62.04) and NWBT (21.99). A cutoff of 40.51 mL/100 g/min showed a sensitivity of 96.6% and specificity of 77.8% for predicting NWBT. In DCE-MRI, 96.6% of the NWBT showed a type A time–signal intensity curve. Although the majority of MT and WT had type C and B curves, respectively, there was overlapping. Among the quantitative DCE parameters, Ktrans and Kep were highly sensitive for differentiating NWBT, WT, and MT. Ktrans, Kep, IAUGC, and MS were maximum in WT, followed by MT and NWBT. Kep and Ktrans both had an accuracy of 84.7% for predicting pleomorphic adenoma. Conclusion Multiparametric MRI is useful for differentiating NWBT, WT, and MT. DCE-MRI helps in differentiating benign from malignant tumors. DWI and ASL are useful in differentiating NWBT from parotid malignancy.

Evaluation of Neurovascular Coupling in Early-Onset and Late-Onset Epilepsy of Unknown Etiology.

Previous studies have shown neurovascular coupling (NVC) dysfunction in epilepsy, suggesting its role in the pathological mechanisms. However, it remains unclear whether NVC abnormalities exist in epilepsy of unknown etiology (EU). To integrate multiparametric MRI to assess NVC and its relationship with cognition in early-onset and late-onset EU patients. Prospective. Ninety-six EU patients (46 early-onset, M/F = 20/26; 50 late-onset, M/F = 29/21) and 60 healthy controls (HCs, M/F = 25/35). 3.0 T, resting-state gradient echo-planar imaging, pseudo-continuous arterial spin labeling (pc-ASL), and T1-weighted brain volume sequence. Functional MRI data were analyzed to assess intrinsic brain activity including amplitude of low-frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), and functional connectivity strength (FCS), while pc-ASL provided cerebral blood flow (CBF) measurements. Coupling correlation coefficients and ratios of CBF to neural activity were calculated to evaluate global and regional NVC. Two-sample t-test, Analysis of Variance, Kruskal-Wallis test, Chi-square test, Analysis of Covariance, family-wise error/Bonferroni correction, partial correlation analyses. Statistical significance was defined as P < 0.05. Whole-brain analysis revealed increased ALFF values in both patient groups' left precentral and postcentral gyri. Both patient groups had lower global NVC coefficients than HCs, with reduced CBF-ALFF (0.28 vs. 0.30), CBF-fALFF (0.43 vs. 0.45), and CBF-ReHo (0.40 vs. 0.41) in early-onset patients, and lower CBF-fALFF (0.38 vs. 0.45) and CBF-ReHo (0.32 vs. 0.41) in late-onset patients. Regional analysis showed significantly decreased CBF/ALFF ratios in the left precentral and postcentral gyri (T = 3.85 to 5.33). Reduced global NVC in early-onset patients was significantly associated with poorer executive function (r = 0.323), while global coupling in late-onset patients was negatively correlated with disease duration (r = -0.348 to -0.426). This study showed abnormal global and regional NVC in both early-onset and late-onset EU patients, emphasizing the potential role of NVC in the pathophysiological mechanisms of EU. 1 TECHNICAL EFFICACY: Stage 1.

Dynamic B0 field shimming for improving pseudo-continuous arterial spin labeling at 7 T.

B0 field inhomogeneity within the brain-feeding arteries is a major issue for pseudo-continuous arterial spin labeling (PCASL) at 7 T because it reduces the labeling efficiency and leads to a loss of perfusion signal. This study aimed to develop a vessel-specific dynamic B0 field shimming method for 7 T PCASL to improve the labeling efficiency by correcting off-resonance within the arteries in the labeling region. We implemented a PCASL sequence with dynamic B0 shimming at 7 T that compensates for B0 field offsets in the brain-feeding arteries by updating linear shimming terms and adding a phase increment to the PCASL RF pulses. Rapidly acquired vessel-specific B0 field maps were used to calculate dynamic B0 shimming parameters. We evaluated both 2D and 3D variants of our method, comparing their performance against the established global frequency offset and optimal encoding scheme-based corrections. Cerebral blood flow (CBF) maps were quantified before and after corrections, and CBF values from different methods were compared across the whole brain, white matter, and gray matter regions. All off-resonance correction methods significantly recovered perfusion signals across the brain. The proposed vessel-specific dynamic B0 shimming method improved the labeling efficiency while maintaining optimal static shimming in the imaging region. Perfusion-weighted images demonstrated the superiority of the 3D dynamic B0 shimming method compared to global or 2D-based correction approaches. CBF analysis revealed that 3D dynamic B0 shimming significantly increased CBF values relative to the other methods. Our proposed dynamic B0 shimming method offers a significant advancement in PCASL robustness and effectiveness, enabling full utilization of 7 T ASL high sensitivity and spatial resolution.

The menopausal transition and multiple physiologic measures of early brain health in the Coronary Artery Risk Development in Young Adults study.

This study proposed to investigate the cross-sectional and longitudinal associations of menopausal status with physiologic brain magnetic resonance imaging measures. The sample included women from the Coronary Artery Risk Development in Young Adults study who self-reported their reproductive histories and participated in the brain magnetic resonance imaging substudies at the year 25 (n = 292) and year 30 (n = 258) follow-up examinations. Menopausal status was classified based on natural menstrual cycle regularity/cessation at both time points. Gray matter cerebrovascular reactivity (CVR) was calculated as mean percent change in blood oxygen level-dependent signals in activated voxels following a breath-hold challenge. Gray matter cerebral blood flow (CBF) was assessed using pseudo-continuous arterial spin labeling. Linear regression models were used to examine cross-sectional and longitudinal associations of menopausal status with gray matter CVR and CBF after adjustment for potential age-related covariates. Women were mean age 50 years at year 25; 37% were Black; and 46% were postmenopausal. Relative to premenopause or perimenopause, postmenopause was associated with lower gray matter CVR at year 30 cross-sectionally (1.86% vs 1.69%, P = 0.03, respectively) and longitudinally for women who were postmenopausal at both time points (-0.32% [95% CI, -0.63% to -0.02%]) after covariate adjustment. Mean CVR values were also lower for these women when compared with women who remained premenopausal or perimenopausal (1.71% compared with 2.04%, respectively). Menopausal status was unrelated to either concurrent or longitudinal gray matter CBF. These findings suggest that the ability of vessels to adapt in response to hypercapnia may be impaired during menopause, even within a relatively short time window.

Lower neurovascular coupling response despite higher cerebral blood flow at rest in apolipoprotein ɛ4 positive adults.

Cerebral blood flow at rest declines with age. However, age-related changes in functional measures of cerebrovascular health including cerebrovascular reactivity and neurovascular coupling are not well understood. Additionally, the effect of apolipoprotein E (APOE) ε4, a strong genetic risk factor for Alzheimer's disease, on cerebral blood flow and cerebrovascular function remains unclear. APOEε4 positive (APOEε4+; n = 37, age = 63±4y) and APOEε4 negative (APOEε4-; n = 50, age = 63±4y) cognitively unimpaired adults participated in this study. Macrovascular cerebral blood flow and microvascular cerebral perfusion were measured using 4D flow MRI and pseudo-continuous arterial spin labeling MRI, respectively. Cerebrovascular reactivity and neurovascular coupling were assessed by measuring middle cerebral artery blood velocity in response to hypercapnia and the n-back test, respectively. Neurovascular coupling was lower in APOEε4+ compared with APOEε4- adults (P<0.05), despite higher cerebral blood flow and cerebrovascular reactivity to hypercapnia. Alterations in neurovascular coupling may occur early, prior to changes in cognition, in aging APOEε4 carriers.

Assessment of cerebral perfusion alterations in dementia with Lewy bodies and Alzheimer's disease.

Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) are common forms of dementia, characterized by overlapping clinical symptoms. Functional neuroimaging can provide valuable information for precise diagnosis. Our objective was to explore cerebral perfusion alterations in DLB and AD, and to determine which perfusion parameters are helpful in distinguishing DLB and AD. A total of 25 DLB patients, 34 AD patients, and 40 normal controls (NC) underwent neuropsychological testing and pseudo-continuous arterial spin labeling (pcASL) for assessing cerebral perfusion [mean cerebral flow (mCBF); arterial transit time (ATT)] indexes. Differences in perfusion indexes among the three groups were analyzed and the family-wise error (FWE) was used for multiple comparisons. Spearman analysis assessed the relationships between the mCBF and neuropsychological scores [mini-mental state examination (MMSE); Montreal Cognitive Assessment (MoCA)]. A receiver operating characteristic (ROC) analysis was conducted to evaluate the performance and discriminant value of different perfusion indices in distinguishing between the two diseases. Compared with NC, the mCBF of patients with DLB was reduced mainly in the bilateral frontal lobe, bilateral parietal lobes, bilateral temporal lobes, and the right occipital lobe. AD patients showed lower mCBF mainly in the bilateral frontal lobes, the right temporal lobe, and the left parietal lobe. Compared with AD, DLB patients showed decreased mCBF in the bilateral frontal and parietal lobes. ATT in almost all major arterial regions was prolonged in DLB and AD when compared to NC. Compared with AD, ATT was significantly prolonged in DLB (P<0.05). Furthermore, the DLB demonstrated a significant positive correlation between mCBF and MMSE scores, particularly in regions such as the left superior parietal lobule (r=0.596, P=0.002) and the right precuneus (r=0.498, P=0.01). Similarly, AD exhibits a positive correlation between mCBF and MMSE scores within regions, such as the right middle temporal gyrus (r=0.550, P=0.001) and the left inferior parietal lobule (r=0.571, P<0.001). The perfusion indexes could help distinguish DLB from AD. DLB demonstrates a different pattern of regional blood flow reduction and prolonged ATT, which is different from that in AD. ASL-derived parameters provide critical discriminative information for differentiating DLB and AD.

Regional changes in cerebral perfusion with age when accounting for changes in gray-matter volume.

One possible contributing factor for cerebral blood flow (CBF) decline in normal aging is the increase in partial volume effects due to brain atrophy, as cortical thinning can exacerbate the contamination of gray-matter (GM) voxels by other tissue types. This work investigates CBF changes in normal aging of a large elderly cohort aged 54 to 84 and how correction for partial volume effects that would accommodate potential changes in GM might affect this. The study cohort consisted of 474 participants aged 54 to 84 years using pseudo-continuous arterial spin labeling MRI. A volumetric pipeline and a surface-based pipeline were applied to measure global and regional perfusion. Volumetric regions of interest (ROIs) included GM, cerebral white matter, vascular territories, and the brain atlas from the UK Biobank. The cortical parcellation was using Desikan-Killiany atlas. Non-partial volume effect correction (PVEc) and PVEc GM-CBF changes with aging were modeled using linear regressions. Global GM CBF decreased by 0.17 mL/100 g/min per year with aging before PVEc (p < 0.05) and was 0.18 mL/100 g/min after PVEc (p < 0.05). All cortical parcels exhibited CBF decreases with age before PVEc. After PVEc, seven parcels retained decreasing trends. However, GM CBF demonstrated increase with age after PVEc in three parcels. Although decreases in global perfusion are observed with aging before PVEc, perfusion variations appear to be more regionally selective after PVEc. This supports the understanding that variation in cerebral perfusion with age observed with imaging is influenced by regional changes in anatomy that can be accommodated with PVEc, but perfusion variation is still observable even after PVE is accounted for.

Interictal EEG spikes increase perfusion in low-grade epilepsy-associated tumors: a pediatric arterial spin labeling study.

Arterial spin labeling (ASL), a noninvasive magnetic resonance (MRI) perfusion sequence, holds promise in the presurgical evaluation of pediatric lesional epilepsy patients, including those with low-grade epilepsy-associated tumors (LEATs). The interpretation of ASL-derived perfusion patterns, however, presents challenges. Our study aims to elucidate these perfusion changes in children with LEATs, exploring their correlations with clinical, electroencephalography (EEG), and anatomical MRI findings. Our cohort included 15 children with LEAT-associated focal lesional epilepsy who underwent single-delay pseudo-continuous ASL imaging; eight were imaged under sedation. We assessed perfusion images both qualitatively and quantitatively, focusing on LEAT-related perfusion changes, as indicated by the asymmetry index (AI) and regional cerebral blood flow (rCBF). ASL revealed LEAT-related perfusion changes in all but two patients: 12 LEATs were hypoperfused and one was hyperperfused relative to the contralateral brain parenchyma (CBP). LEATs showed significantly lower perfusion compared to CBP (median: 38.7 vs. 59.1mL/100g/min for LEAT and CBP, respectively; p value = 0.004, Wilcoxon-Mann-Whitney), regardless of sedation. Notably, elevated AI and rCBF values correlated with interictal spikes on EEG (median: -0.008 and 0.84 vs -0.27 and 0.58, respectively), but not to other clinical, EEG, or MRI variables (p value = 0.036, Wilcoxon-Mann-Whitney). By highlighting the connection between LEAT and brain perfusion, and by correlating perfusion characteristics and epileptogenicity, our research enhanced our understanding of pediatric epilepsy associated with LEATs. Also, by proving the robustness of these findings to sedation we confirmed the importance of adding ASL to epilepsy protocols to as a valuable tool to supplement anatomical imaging.

High-resolution perfusion imaging in rodents using pCASL at 9.4T.

Adequate perfusion is critical for maintaining normal brain function and aberrations thereof are hallmarks of many diseases. Pseudo-Continuous Arterial Spin Labeling (pCASL) MRI enables noninvasive quantitative perfusion mapping without contrast agent injection and with a higher signal-to-noise ratio (SNR) than alternative methods. Despite its great potential, pCASL remains challenging, unstable, and relatively low-resolution in rodents - especially in mice - thereby limiting the investigation of perfusion properties in many transgenic or other relevant rodent models of disease. Here, we address this gap by developing a novel experimental setup for high-resolution pCASL imaging in mice and combining it with the enhanced SNR of cryogenic probes. We show that our new experimental setup allows for optimal positioning of the carotids within the cryogenic coil, rendering labeling reproducible. With the proposed methodology, we managed to increase the spatial resolution of pCASL perfusion images by a factor of 15 in mice; a factor of 6 in rats is gained compared to the state of the art just by virtue of the cryogenic coil. We also show that the improved pCASL perfusion imaging allows much better delineation of specific brain areas, both in healthy animals as well as in rat and mouse models of stroke. Our results bode well for future high-definition pCASL perfusion imaging in rodents.

Cerebral blood flow and arterial transit time responses to exercise training in older adults

Brain vascular health worsens with age, as is made evident by resting grey matter cerebral blood flow (CBFGM) reductions and lengthening arterial transit time (ATTGM). Exercise training can improve aspects of brain health in older adults, yet its effects on CBFGM and ATTGM remain unclear. This randomised controlled trial assessed responses of CBFGM and ATTGM to a 26 week exercise intervention in 65 healthy older adults (control: n = 33, exercise: n = 32, aged 60–81 years), including whether changes in CBFGM or ATTGM were associated with changes in cognitive functions. Multiple-delay pseudo-continuous arterial spin labelling data were used to estimate resting global and regional CBFGM and ATTGM. Results showed no between-group differences in CBFGM or ATTGM following the intervention. However, exercise participants with the greatest cardiorespiratory gains (n = 17; ∆V̇O2peak >2 mL/kg/min) experienced global CBFGM reductions (-4.0 [-7.3, -0.8] mL/100 g/min). Cognitive functions did not change in either group and changes were not associated with changes in CBFGM or ATTGM. Our findings indicate that exercise training in older adults may induce global CBFGM reductions when high cardiorespiratory fitness gains are induced, but this does not appear to affect cognitive functions.

Age-related decline in blood-brain barrier function is more pronounced in males than females in parietal and temporal regions.

The blood-brain barrier (BBB) plays a pivotal role in protecting the central nervous system (CNS), and shielding it from potential harmful entities. A natural decline of BBB function with aging has been reported in both animal and human studies, which may contribute to cognitive decline and neurodegenerative disorders. Limited data also suggest that being female may be associated with protective effects on BBB function. Here, we investigated age and sex-dependent trajectories of perfusion and BBB water exchange rate (kw) across the lifespan in 186 cognitively normal participants spanning the ages of 8-92 years old, using a non-invasive diffusion-prepared pseudo-continuous arterial spin labeling (DP-pCASL) MRI technique. We found that the pattern of BBB kw decline with aging varies across brain regions. Moreover, results from our DP-pCASL technique revealed a remarkable decline in BBB kw beginning in the early 60 s, which was more pronounced in males. In addition, we observed sex differences in parietal and temporal regions. Our findings provide in vivo results demonstrating sex differences in the decline of BBB function with aging, which may serve as a foundation for future investigations into perfusion and BBB function in neurodegenerative and other brain disorders.

The Influence of Anthropometric Factors on Renal mpMRI: Insights From Regional Analysis.

Multiparametric MRI (mpMRI) provides detailed insights into renal function, but the impact of anthropometric factors on renal imaging is not fully understood. To investigate regional correlations between mpMRI parameters and age, body mass index (BMI), and body surface area (BSA). Prospective, cross-sectional observational study. Twenty-nine healthy volunteers (44.5 ± 18.3 years, 18 females) without a history of renal disease. 3-T, pseudo-continuous arterial spin labeling, multi-echo gradient-recalled echo, diffusion-weighted imaging, T1 and T2 mapping. Bilateral kidneys were segmented into nine concentric layers (outer cortex to inner regions) and nine equiangular sections (lower to upper pole). Key parameters (renal blood flow [RBF], , apparent diffusion coefficient [ADC], T1 and T2 maps) were correlated with age, BMI, and BSA. Differences in parameters between age and BMI groups were also evaluated. Spearman correlation, Mann-Whitney U test, and rank-biserial correlation coefficient for effect size. A P-value <0.05 was considered statistically significant. RBF correlated negatively with age in all regions and BMI in inner layers and lower pole. ADC negatively correlated with BMI (significance was not reached in layers 2, 7, 8; P-value = 0.06-0.12) and BSA in layers 1-7. T1 negatively correlated with age in inner regions and lower medial pole. Significant positive correlations were found between age and (outermost layer, upper pole), age and T2 (inner and cranial-caudal regions), as well as BMI and T2 (except upper pole; P-value = 0.06). Significant differences between age groups were observed for RBF (all regions), (outermost and second innermost layers, central lateral region), T1 (innermost layer), and T2 (upper medial pole). Between BMI groups, ADC (middle layers, upper medial pole) and T2 (outermost and inner layers, lower pole to lateral region) differed significantly. Intrarenal variance of mpMRI parameters correlated with age, BMI, and BSA. 4 TECHNICAL EFFICACY: Stage 1.

Trajectories and sex differences of brain structure, oxygenation and perfusion functions in normal aging

Background: Brain structure, oxygenation and perfusion are important factors in aging. Coupling between regional cerebral oxygen consumption and perfusion also reflects functions of neurovascular unit (NVU). Their trajectories and sex differences during normal aging important for clinical interpretation are still not well defined. In this study, we aim to investigate the relationship between brain structure, functions and age, and exam the sex disparities.Method: A total of 137 healthy subjects between 20∼69 years old were enrolled with conventional MRI, structural three-dimensional T1-weighted imaging (3D-T1WI), 3D multi-echo gradient echo sequence (3D-mGRE), and 3D pseudo-continuous arterial spin labeling (3D-pCASL). Oxygen extraction fraction (OEF) and cerebral blood flow (CBF) were respectively reconstructed from 3D-mGRE and 3D-pCASL images. Cerebral metabolic rate of oxygen (CMRO2) were calculated as follows: CMRO2=CBF·OEF·[H]a, [H]a=7.377 μmol/mL. Brains were segmented into global gray matter (GM), global white matter (WM), and 148 cortical subregions. OEF, CBF, CMRO2, and volumes of GM/WM relative to intracranial volumes (rel_GM/rel_WM) were compared between males and females. Generalized additive models were used to evaluate the aging trajectories of brain structure and functions. The coupling between OEF and CBF was analyzed by correlation analysis. P or PFDR < 0.05 was considered statistically significant.Results: Females had larger rel_GM, higher CMRO2 and CBF of GM/WM than males (P < 0.05). With control of sex, CBF of GM significantly declined between 20 and 32 years, CMRO2 of GM declined subsequently from 33 to 41 years and rel_GM decreased significantly at all ages (R2 = 0.27, P < 0.001; R2 = 0.17, P < 0.001; R2 = 0.52, P < 0.001). In subregion analysis, CBF declined dispersedly while CMRO2 declined widely across most subregions of the cortex during aging. Robust negative coupling between OEF and CBF was found in most of the subregions (r range = -0.12∼-0.48, PFDR < 0.05).Conclusion: The sex disparities, age trajectories of brain structure and functions as well as the coupling of NVU in healthy individuals provide insights into normal aging which are potential targets for study of pathological conditions.

Repeatability and Reproducibility of pseudo-Continuous Arterial Spin Labeling Measured Brain Perfusion in Healthy Volunteers and Glioblastoma Patients.

Arterial spin labeled (ASL) MRI has gained recognition as a quantitative perfusion imaging method for managing patients with brain tumors. Limited studies have so far investigated the reproducibility of ASL-derived perfusion in patients with brain tumors. This study aims to evaluate intrasession repeatability and intersession reproducibility of perfusion measurements using 3D pseudo-continuous ASL (pCASL) with Cartesian TSE (TSE-CASPR) in healthy volunteers (HV) and glioblastoma (GBM) patients at 3 Tesla and compare against 3D pCASL with GRASE. This prospective study (NCT03922984) was approved by the institutional review board and written informed consent was obtained from all subjects. HV underwent repeated pCASL evaluations 2-4 weeks apart between November 2021 and October 2022. GBM patients were recruited for longitudinal MRI from September 2019 to February 2023. Intrasession repeatability (HV and GBM) and intersession reproducibility (HV only) of pCASL were assessed using linear regression, Bland-Altman analyses, intraclass correlation coefficient (ICC) with 95% confidence interval (CI), and within-subject coefficients of variation (wsCV). Twenty HV (9 men, age: 25.1±1.7 years, range 23-30 years) and 21 GBM patients (15 men; age: 59.8±14.3 years, range 28-81 years) were enrolled. Within imaging session, 3D pCASL measured perfusion with TSE-CASPR and GRASE respectively achieved high R2 values (0.88-0.95; 0.93-0.96), minimal biases (-0.46 to 0.81; -0.08 to 0.35 mL/100g/min), high ICC [95% CI] (0.96-0.98 [0.94-0.98]; 0.96-0.98 [0.92-0.99]), and low wsCV (6.64%-9.07%; 5.20%-8.16%) in HV (N=20) and GBM patients (N=21). Across imaging session, 3D pCASL in HV (N=20) achieved high R2 values (0.71; 0.82), minimal biases (-1.2; -0.90 mL/100g/min), high ICC [95% CI] values (0.85 [0.81-0.89]; 0.90 [0.87-0.93]), and low wsCV values (13.82%; 9.98%). Our study demonstrated excellent intrasession repeatability of 3D pCASL measured cerebral perfusion in HV and GBM patients and good to excellent intersession reproducibility in HV. 3D pCASL with GRASE performed slightly better than 3D pCASL with TSE-CASPR in HV; however, in GBM patients, 3D pCASL with TSE-CASPR showed better performance in tumor regions with nearly twofold higher SNR. ASL measured perfusion could serve as a non-contrast quantitative imaging biomarker to facilitate the management of GBM patients. ASL = arterial spin labeling; pCASL = pseudo-continuous arterial spin labeling; GBM = glioblastoma; CBF = cerebral blood flow; CASPR = Cartesian acquisition with spiral profile reordering; GRASE = gradient and spin echo; NAGM = normal-appearing gray matter.

Evaluation of an Image-based Classification Model to Identify Glioma Subtypes Using Arterial Spin Labeling Perfusion MRI On the Publicly Available UCSF Glioma Dataset.

Glioma is acomplex cancer comprising various subtypes and mutations, which may have different metabolic characteristics that can potentially be investigated and identified using perfusion imaging. Therefore, the aim of this work was to use radiomics and machine learning analysis of arterial spin labeling MRI data to automatically differentiate glioma subtypes and mutations. Atotal of 495 Arterial Spin Labeling (ASL) perfusion imaging datasets from the UCSF Glioma database were used in this study. These datasets were segmented to delineate the tumor volume and classified according to tumor grade, pathological diagnosis, and IDH status. Perfusion image data was obtained from a3T MRI scanner using pseudo-continuous ASL. High level texture features were extracted for each ASL dataset using PyRadiomics after tumor volume segmentation and then analyzed using amachine learning framework consisting of ReliefF feature ranking and logistic model tree classification algorithms. The results of the evaluation revealed balanced accuracies for the three endpoints ranging from 55.76% (SD = 4.28, 95% CI: 53.90-57.65) for the tumor grade using 25.4 ± 37.21 features, 62.53% (SD = 2.86, 95% CI: 61.27-63.78) for the mutation status with 23.3 ± 29.17 picked features, and 80.97% (SD = 1.83, 95% CI: 80.17-81.78) for the pathological diagnosis which used 47.3 ± 32.72 selected features. Radiomics and machine learning analysis of ASL perfusion data in glioma patients hold potential for aiding in the diagnosis and treatment of glioma, mainly for discerning glioblastoma from astrocytoma, while performance for tumor grading and mutation status appears limited.

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.

Cerebral blood flow from arterial spin labeling as an imaging biomarker of outcome after endovascular therapy for ischemic stroke.

Arterial spin labeling (ASL) is a contrast agent-free magnetic resonance imaging (MRI) technique to measure cerebral blood flow (CBF). We sought to investigate effects of CBF within the infarct on outcome and risk of hemorrhagic transformation (HT). In 111 patients (median age: 74 years, 50 men) who had undergone mechanical thrombectomy (MT) for ischemic stroke of the anterior circulation (median interval: 4 days between MT and MRI), post-stroke %CBF difference from pseudo-continuous ASL was calculated within the diffusion-weighted imaging (DWI)-positive infarct territory following lesion segmentation in relationship to the unaffected contralateral side. Functional independence was defined as a modified Rankin Scale (mRS) of 0-2 at 90 days post-stroke. %CBF difference, pre-stroke mRS, and infarct volume were independently associated with functional independence in a multivariate regression model. %CBF difference was comparable between patients with and without HT. A subcohort of 10 patients with decreased infarct-CBF despite expanded Treatment in Cerebral Infarction (eTICI) 2c or 3 recanalization was identified (likely related to the no-reflow phenomenon). Outcome was significantly worse in this group compared to the remaining cohort. In conclusion, ASL-derived %CBF difference from the DWI-positive infarct territory independently predicted functional independence, but %CBF difference was not significantly associated with an increased risk of HT.