Arterial Spin Labeling Imaging Research Articles

Global hyperperfusion after successful endovascular thrombectomy is linked to worse outcome in acute ischemic stroke

Patients with stroke may develop hyperperfusion after a successful endovascular thrombectomy (EVT). However, the relationship between post-EVT hyperperfusion and clinical outcomes remains unclear and requires further clarification. We reviewed consecutive patients with anterior circulation occlusion who were successfully recanalized with EVT. Based on post-EVT arterial spin-labeling images, hyperperfusion was categorized as follows: global hyperperfusion (GHP), increased cerebral blood flow (CBF) in ≥ 50% of the culprit vessel territory; focal hyperperfusion (FHP), increased CBF in < 50% of the culprit vessel territory; no hyperperfusion (NHP), no discernible CBF increase. Factors associated with hyperperfusion were assessed, and clinical outcomes were compared among patients under different hyperperfusion categories. Among 131 patients, 25 and 40 patients developed GHP and FHP, respectively. Compared to other groups, the GHP group had worse National Institutes of Health Stroke Scale score (GHP vs. NHP/FHP, 18.1 ± 7.4 vs. 12.3 ± 6.0; p < 0.001), a larger post-EVT infarct volume (98.9 [42.3–132.7] vs. 13.5 [5.0–34.1] mL; p < 0.001), and a worse 90-day outcome (modified Rankin Scale, 3 [1–4] vs. 2 [0–3]; p = 0.030). GHP was independently associated with infarct volume (B = 0.532, standard error = 0.163, p = 0.001), and infarct volume was a major mediator of the association of GHP with unfavorable outcomes (total effect: β = 0.176, p = 0.034; direct effect: β = 0.045, p = 0.64; indirect effect: β = 0.132, p = 0.017). Patients presenting with post-EVT GHP had poorer neurological prognosis, which is likely mediated by a large infarct volume.

Axial MR Angiography in Evaluating Revascularization after Indirect Bypass Surgery for Moyamoya.

At our institution, revascularization after indirect moyamoya surgery is routinely evaluated using magnetic resonance angiography (MRA) rather than catheter angiography. This study reviews how revascularization can be visualized on axial MRA versus catheter angiography and compares clinical outcomes of surgeries evaluated by routine postoperative MRA versus routine catheter angiography. We reviewed the records of all patients treated at our institution who underwent unilateral encephaloduroarteriosynangiosis (EDAS)/pial synangiosis 2004-2021 at 1-21 years of age. Inclusion criteria included undergoing preoperative MRA within 18 months of surgery and postoperative MRA 3 to 30 months after surgery. Clinical outcome measures included postoperative stroke and transient ischemic attacks (TIAs), changes in symptoms (improved, unchanged, worsened), and new postoperative symptoms. Measures were compared between surgeries evaluated by routine postoperative MRA versus routine postoperative angiograms. For each surgery, we determined the ratios of the diameters and areas of the donor and contralateral corresponding vessels and the relative signal intensities of these two vessels on preoperative- and 3-to-30-month postoperative MRA. We did the same for the middle meningeal artery (MMA) ipsilateral to the donor artery and the contralateral MMA. We assessed changes from pre- to post-operation in diameter ratios, area ratios, relative signal intensity, ivy sign, and brain perfusion on arterial spin labeled (ASL) imaging. MRI and MRA measures of revascularization and flow were compared to Matsushima grades in patients who had postoperative catheter angiograms. Fifty-one operations were included. There were no significant differences in rates of strokes, TIAs, changes or new symptoms after surgeries evaluated by routine postoperative MRA versus catheter angiogram. Significant associations existed between greater collateralization on postoperative MRA and greater median increases in preoperative-to-postoperative ratios of donor-vessel-over-contralateral-vessel diameter (p=0.0461) and ipsilateral-MMA-over-contralateral-MMA diameter (p=0.0135). The median increase in the ratio of the donor-vessel-over-corresponding-contralateral-vessel diameters was significantly higher for Matsushima grade A versus B (p=0.036). The median increase in the ratio of the sum of donor-and-ipsilateral-MMA diameters over the sum of the contralateral vessel diameters was significantly higher for improved-versus-unchanged perfusion on ASL imaging (p=0.0074). There was a nonsignificant association between greater postoperative collateralization on MRA and Matsushima grade (p=0.1160) Conclusion: Cerebral revascularization after EDAS/pial synangiosis can be evaluated on axial MRA by comparing the diameter and/or signal intensity of the donor vessel and ipsilateral MMA to those of the corresponding contralateral vessels on postoperative-versus-preoperative MRA. The use of routine postoperative MRA rather than catheter angiography does not appear to negatively affect outcomes.

Endovascular thrombectomy in wake-up stroke guided by arterial spin-labeling and fluid-attenuated inversion recovery versus diffusion-weighted imaging mismatch on MRI.

This purpose of this study is to investigate the effectiveness and safety of utilizing the arterial spin-labeling (ASL) combined with diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) combined with DWI double mismatch in the endovascular treatment of patients diagnosed with wake-up stroke (WUS). In this single-center trial, patients diagnosed with WUS underwent thrombectomy if acute ischemic lesions were observed on DWI indicating large precerebral circulation occlusion. Patients with no significant parenchymal hypersignal on FLAIR and ASL imaging showing a hypoperfusion tissue to infarct core volume ratio of at least 1.2 were included. The participants were divided into groups receiving endovascular thrombectomy plus medical therapy or medical therapy alone, based on their subjective preference. Functional outcomes were assessed using the ordinal score on the modified Rankin scale (mRs) at 90 days, along with the rate of functional independence. In this study, a total of 77 patients were included, comprising 38 patients in the endovascular therapy group and 39 patients in the medical therapy group. The endovascular therapy group exhibited more favorable changes in the distribution of functional prognosis measured by mRs at 90 days, compared to the medical therapy group (adjusted common odds ratio, 3.25; 95% CI, 1.03 to 10.26; P < 0.01). Additionally, the endovascular therapy group had a higher proportion of patients achieving functional independence (odds ratio, 4.0; 95% CI, 1.36 to 11.81; P < 0.01). Importantly, there were no significant differences observed in the incidence of intracranial hemorrhage or mortality rates between the two groups. Guided by the ASL-DWI and FLAIR-DWI double mismatch, endovascular thrombectomy combined with standard medical treatment appears to yield superior functional outcomes in patients with WUS and large vessel occlusion compared to standard medical treatment alone.

Cortical Hyperperfusion on MRI Arterial Spin-Labeling during the Interictal Period of Patients with Migraine Headache.

Concentrations of calcitonin gene-related peptide, a neuropeptide and potent endogenous vasodilator, are reportedly higher in patients with migraine than in healthy subjects, both during and between migraine attacks, reflecting ongoing activation of the trigeminal nervous system. In this prospective study, we measured CBF during the interictal period of patients with migraine after considering insomnia and depression and examined the effects of ongoing activation of the trigeminal nervous system, including during the interictal period, on CBF. In a total of 242 patient with migraine (age range, 18-75 years), CBF was measured by MR imaging arterial spin-labeling during the interictal period and was compared with results from 26 healthy volunteers younger than 45 years of age as control subjects (age range, 22-45 years). Cortical hyperperfusion was defined as identification of ≥2 cerebral cortical regions with regional CBF values at least 2 SDs above the mean regional CBF in control subjects. The overall frequency of cortical hyperperfusion was significantly higher in patients with migraine (115 of 242, 48%) than in control subjects (1 of 26, 4%). Multivariable analysis revealed the 18- to 40-year age group and patients with migraine without insomnia as significant positive clinical factors associated with cortical hyperperfusion. Among patients with migraine without insomnia, the frequency of cortical hyperperfusion was >92% (89 of 97). One-way ANOVA showed that in all ROIs of the cortex, regional CBF was significantly higher in patients with migraine without insomnia than in patients with migraine with insomnia or control subjects. In patients with migraine without insomnia, cortical hyperperfusion findings showed a sensitivity of 0.918 and a specificity of 0.962 for migraine in the interictal period, representing excellent accuracy. In contrast, among patients with migraine with insomnia, sensitivity was only 0.179 but specificity was 0.962. Patients with migraine without insomnia may have cortical hyperperfusion during the interictal period; however, the findings of the present study need to be prospectively validated on a larger scale before clinical applicability can be considered.

Influence of arterial transit time delays on the differentiation between tumor progression and pseudoprogression in glioblastoma by arterial spin labeling magnetic resonance imaging.

Arterial spin labeling (ASL) and dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) have shown potential for differentiating tumor progression from pseudoprogression. For pseudocontinuous ASL with a single postlabeling delay, the presence of delayed arterial transit times (ATTs) could affect the evaluation of ASL-MRI perfusion data. In this study, the influence of ATT artifacts on the perfusion assessment and differentiation between tumor progression and pseudoprogression were studied. This study comprised 66 adult patients (mean age 60 ± 13 years; 40 males) with a histologically confirmed glioblastoma who received postoperative radio (chemo)therapy. ASL-MRI and DSC-MRI scans were acquired at 3months postradiotherapy as part of the standard clinical routine. These scans were visually scored regarding (i) the severity of ATT artifacts (%) on the ASL-MRI scans only, scored by two neuroradiologists; (ii) perfusion of the enhancing tumor lesion; and (iii) radiological evaluation of tumor progression versus pseudoprogression by one neuroradiologist. The final outcome was based on combined clinical and radiological follow-up until 9months postradiotherapy. ATT artifacts were identified in all patients based on the mean scores of two raters. A significant difference between the radiological evaluation of ASL-MRI and DSC-MRI was observed only for ASL images with moderate ATT severity (30%-65%). The perfusion assessment showed ASL-MRI tending more towards hyperperfusion than DSC-MRI in the case of moderate ATT artifacts. In addition, there was a significant difference between the prediction of tumor progression with ASL-MRI and the final outcome in the case of severe ATT artifacts (McNemar test, p= 0.041). Despite using ASL imaging parameters close to the recommended settings, ATT artifacts frequently occur in patients with treated brain tumors. Those artifacts could hinder the radiological evaluation of ASL-MRI data and the detection of true disease progression, potentially affecting treatment decisions for patients with glioblastoma.

Retrospective correction of second-order concomitant fields in 3D axial stack-of-spirals imaging on a high-performance gradient system.

MRI using 3D stack-of-spirals (SoS) readout on a high-performance gradient system is subject to strong second-order, spatially varying concomitant fields, which can lead to signal dropout and blurring artifacts that become more significant at locations farther from the gradient isocenter. A method for compensating for second-order concomitant fields in 3D axial SoS image reconstruction is described. We retrospectively correct for second-order concomitant field-induced phase error in the 3D SoS data by slice-dependent k-space phase compensation based on the nominal spiral readout trajectories. The effectiveness of the method was demonstrated in phantom and healthy volunteer scans in which 3D pseudo-continuous arterial spin labeling imaging was performed with SoS fast spin-echo readout at 3 T. Substantial reduction in blurring was observed with the proposed method. In phantom scans, blurring was reduced by about 53% at 98 mm from the gradient isocenter. In the in vivo 3D pseudo-continuous arterial spin labeling scans, differences of up to 10% were observed at 78 mm from the isocenter, especially around the white-matter and gray-matter interfaces, between the corrected and uncorrected proton density images, perfusion-weighted images, and cerebral blood flow maps. The described retrospective correction method provides a means to correct erroneous phase accruals due to second-order concomitant fields in 3D axial stack-of-spirals imaging.

Functional magnetic resonance imaging for staging chronic kidney disease: a systematic review and meta-analysis.

The commonly used clinical indicators are not sensitive and comprehensive enough to evaluate the early staging of chronic kidney disease (CKD). This study aimed to evaluate the differences in arterial spin labeling (ASL) and blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-MRI) parameter values among patients at various stages of chronic kidney disease and healthy individuals. Electronic databases PubMed, Web of Science, Cochrane, and Embase were searched from inception to March 29, 2024, to identify relevant studies on ASL and BOLD in CKD. The renal blood flow (RBF) and apparent relaxation rate (R2*) values were obtained from healthy individuals and patients with various stages of CKD. The meta-analysis was conducted using STATA version 12.0. The random-effects model was used to obtain estimates of the effects, and the results were expressed as 95% confidence intervals (CIs) and mean differences (MDs) of continuous variables. A total of 18 published studies were included in this meta-analysis. The cortical RBF and R2* values and medulla RBF values were considerably distinct between patients with various stages of CKD and healthy controls (MD, - 78.162; 95% CI, - 85.103 to - 71.221; MD, 2.440; 95% CI, 1.843 to 3.037; and MD, - 36.787; 95% CI, - 47.107 to - 26.468, respectively). No obvious difference in medulla R2* values was noted between patients with various stages of CKD and healthy controls (MD, - 1.475; 95% CI, - 4.646 to 1.696). ASL and BOLD may provide complementary and distinct information regarding renal function and could potentially be used together to gain a more comprehensive understanding of renal physiology.

Effects of the Fasting-Postprandial State on Arterial Spin Labeling MRI-Based Cerebral Perfusion Quantification in Alzheimer's Disease.

The fasting-postprandial state remains an underrecognized confounding factor for quantifying cerebral blood flow (CBF) in the cognitive assessment and differential diagnosis of Alzheimer's disease (AD). To investigate the effects of fasting-postprandial state on arterial spin labeling (ASL)-based CBF in AD patients. Prospective. Ninety-two subjects (mean age = 62.5 ± 6.4 years; females 29.3%), including 30 with AD, 32 with mild cognitive impairment (MCI), and 30 healthy controls (HCs). Differential diagnostic models were developed with a 4:1 training to testing set ratio. 3-T, T1-weighted imaging using gradient echo and pseudocontinuous ASL imaging using turbo spin echo. Two ASL scans were acquired to quantify fasting state and postprandial state regional CBFs based on an automated anatomical labeling atlas. Two-way ANOVA was used to assess the effects of fasting/postprandial state and disease state (AD, MCI, and HC) on regional CBF. Pearson's correlation analysis was conducted between regional CBF and cognitive scores (Mini-Mental State Examination [MMSE] and Montreal Cognitive Assessment [MoCA]). The diagnostic performances of the fasting state, postprandial state, and mixed state (random mixing of the fasting and postprandial state CBF) in differential diagnosis of AD were conducted using support vector machine and logistic regression models. Two-way ANOVA, Pearson's correlation, and area under the curve (AUC) of diagnostic model were performed. P values <0.05 indicated statistical significance. Fasting-state CBF was correlated with cognitive scores in more brain regions (17 vs. 4 [MMSE] and 15 vs. 9 [MoCA]) and had higher absolute correlation coefficients than postprandial-state CBF. In the differential diagnosis of AD patients from MCI patients and HCs, fasting-state CBF outperformed mixed-state CBF, which itself outperformed postprandial-state CBF. Compared with postprandial CBF, fasting-state CBF performed better in terms of cognitive score correlations and in differentiating AD patients from MCI patients and HCs. 2 TECHNICAL EFFICACY: Stage 3.

Pathologic burden goes with the flow: MRI perfusion and pathologic burden in frontotemporal lobar degeneration due to tau

Abstract Regional cerebral blood flow (CBF) changes quantified using arterial spin labeling (ASL) are altered in neurodegenerative disorders such as frontotemporal lobar degeneration due to tau (FTLD-tau), but the relationship between ASL CBF and pathologic burden has not been assessed. Our objective was to determine whether regional ASL CBF acquired antemortem in patients with FTLD-tau is related to pathologic burden measured at autopsy in those same regions in the same patients to directly test the imaging-pathology relationship. In this case-control study, data were acquired between 3/4/2010 and 12/16/2018. Data processing and analysis were completed in 2023. Twenty-one participants with autopsy-confirmed FTLD-tau (N = 10 women, mean[SD] age 67.9[7.56] years) along with 25 control participants (N = 15 women, age 64.7[7.53]) were recruited through the cognitive neurology clinic at the University of Pennsylvania. All participants had ASL and T1-weighted images collected antemortem. ASL images were processed to estimate CBF and T1-weighted images were processed to estimate gray matter (GM) volumes in regions corresponding to regions sampled postmortem. Digital quantification of pathologic burden was performed to find the percent area occupied (%AO) of pathologic FTLD-tau at autopsy. Regional CBF and GM volumes were both related to pathologic burden in the same regions from the same participants. Strengths of model fits of imaging measures to pathologic burden were compared. CBF in FTLD-tau and controls were compared, with results considered significant at p &amp;lt; 0.05 after Bonferroni correction. We found that relative to controls, FTLD-tau displayed hypoperfusion in anterior cingulate, orbitofrontal, middle frontal, and superior temporal regions, as well as angular gyrus. For patients with FTLD-tau regional CBF was significantly associated with pathologic burden (beta = -1.07, t = -4.80, p &amp;lt; 0.005). Models including both GM volume and CBF provided significantly better fits to pathologic burden data than single modality models (p &amp;lt; 0.05, Bonferroni-corrected). Our results indicate that reduced CBF measured using ASL MRI is associated with increased pathologic burden in FTLD-tau and adds complementary predictive value of pathologic burden to structural MRI.

Amide proton transfer weighted contrast has diagnostic capacity in detecting diabetic foot: an MRI-based case-control study.

To evaluate the role of foot muscle amide proton transfer weighted (APTw) contrast and tissue rest perfusion in quantifying diabetic foot (DF) infection and its correlation with blood parameters. With approval from an ethical review board, this study included 40 diabetes mellitus (DM) patients with DF and 31 DM patients without DF or other lower extremity arterial disease. All subjects underwent MRI, which included foot sagittal APTw and coronal arterial spin labeling (ASL) imaging. The normalized MTRasym (3.5 ppm) and the ratio of blood flow (rBF) in rest status of the affected side lesions to the non-affected contralateral side were determined. The inter-group differences of these variables were evaluated. Furthermore, the association between normalized MTRasym (3.5 ppm), rBF, and blood parameters [fasting blood glucose (FBG), glycosylated hemoglobin content, C-reactive protein, neutrophil percentage, and white blood cell count] was explored. Using an ROC curve, the diagnostic capacity of normalized MTRasym (3.5 ppm), BF, and blood biochemical markers in differentiating with or without DF in DM was assessed. In the DF group, MTRasym (3.5 ppm) and BF in lesion and normalized MTRasym (3.5 ppm) were higher than those in the control group (p < 0.05). In addition, correlations were identified between normalized MTRasym (3.5 ppm) and blood parameters, such as C-reactive protein, glycosylated hemoglobin content, FBG, neutrophil ratio, and white blood cell (p < 0.001). Meanwhile, association between BF in lesion and blood parameters, such as C-reactive protein, neutrophil percentage, and FBG (p < 0.01). AUC of normalized MTRasym (3.5 ppm) in identifying with/without DF in patients with DM is 0.986 (95% CI, 0.918-1.00) with the sensitivity of 97.22% and the specificity of 100%. Normalized MTRasym (3.5 ppm) and the BF in lesion may be treated as a safer and more convenient new indicator to evaluate the tissue infection without using a contrast agent, which may be useful in monitoring and preoperatively assessing DF patients with renal insufficiency.

Generalized Venous Prominence on Susceptibility-Weighted Imaging Correlates With Global Cerebral Blood Flow Decline.

Objective This study investigated the global correlation between cerebral blood flow (CBF) decline and increased venous prominence, utilizing arterial spin labeling (ASL) and susceptibility-weighted imaging (SWI) MRI techniques. Methods The study was conducted at the Department of Diagnostic Imaging, St. Marina University Hospital, Varna, Bulgaria. Through a retrospective analysis, we examined data from 115 patients undergoing neurological assessment. CBF decline was assessed through ASL MRI, while global venous visibility was evaluated using SWI MRI. Results The analysis revealed a significant positive correlation between CBF decline and venous prominence (Spearman's rho = 0.261, p = 0.005), indicating a systemic interaction between cerebral perfusion and the venous system. Logistic regression further underscored CBF decline as a significant predictive factor for increased venous visibility (odds ratio (OR) = 1.690, p = 0.004). The assessments' high inter-rater reliability (Cohen's kappa = 0.82) supports the consistency and validity of our findings. Conclusion The integration of ASL and SWI MRI provides critical insights into cerebral hemodynamics, emphasizing the significance of these imaging modalities in both neurovascular research and clinical practice. Our findings suggest a systemic relationship between CBF decline and venous system alterations, underscoring the potential for these techniques to enhance our understanding of neurovascular disorders. Future studies should pursue longitudinal and quantitative analyses to deepen our comprehension of these relationships and their clinical implications.

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.

Multi‑parameter quantitative magnetic resonance imaging in the early assessment of radiation‑induced parotid damage in patients with nasopharyngeal carcinoma following intensity‑modulated radiotherapy.

The present study aimed to investigate the value of intravoxel incoherent motion imaging (IVIM) and three-dimensional pulsed continuous arterial spin labeling (ASL) in assessing dynamic changes of the parotid gland in patients with nasopharyngeal carcinoma (NPC) following radiotherapy (RT). A total of 18 patients with NPC who underwent intensity-modulated RT were enrolled in the present study. All patients underwent conventional magnetic resonance imaging, plus IVIM and ASL imaging of the bilateral parotid glands within 2 weeks prior to RT, and 1 week (1W) and 3 months (3M) following RT. Pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (F) and blood flow (BF) were analyzed. D and BF values were significantly increased from pre-RT to 1W post-RT [change rate: Median (IQR), ΔD1W%: 39.28% (38.23%) and ΔBF1W%: 60.84% (54.88%)] and continued to increase from 1W post-RT to 3M post-RT [55.44% (40.56%) and ΔBF%: 120.39% (128.74%)]. In addition, the F value was significantly increased from pre-RT to 1W post-RT, [change rate: Median (IQR), ΔF1W%: 28.13% (44.66%)], and this decreased significantly from 1W post-RT to 3M post-RT. However, no significant differences were observed between pre-RT and 3M post-RT. Results of the present study also demonstrated that the D* value was significantly decreased from pre-RT to 1W post-RT and 3M post-RT [change rate: Median (IQR), ΔD*1w%: -41.86% (51.71%) and ΔD*3M: -29.11% (42.67%)]. No significant difference was observed between the different time intervals post-RT. There was a significant positive correlation between percentage change in ΔBF1W and radiation dose (ρ=0.548, P=0.001). Thus, IVIM-diffusion-weighted imaging and ASL may aid in the detection and prediction of radiation-induced parotid damage in the early stages following RT. They may contribute to further understanding the potential association between damage to the parotid glands and patient-/treatment-related variables, through the assessment of individual microcapillary perfusion and tissue diffusivity.

Improving advanced intraoperative MRI methods during pediatric neurosurgery.

Advanced intraoperative MR images (ioMRI) acquired during the resection of pediatric brain tumors could offer additional physiological information to preserve healthy tissue. With this work, we aimed to develop a protocol for ioMRI with increased sensitivity for arterial spin labeling (ASL) and diffusion MRI (dMRI), optimized for patient positioning regularly used in the pediatric neurosurgery setting. For ethical reasons, ASL images were acquired in healthy adult subjects that were imaged in the prone and supine position. After this, the ASL cerebral blood flow (CBF) was quantified and compared between both positions. To evaluate the impact of the RF coils setups on image quality, we compared different setups (two vs. four RF coils) by looking at T1-weighted (T1w) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), as well as undertaking a qualitative evaluation of T1w, T2w, ASL, and dMR images. Mean ASL CBF did not differ between the surgical prone and supine positions in any of the investigated regions of interest or the whole brain. T1w SNR (gray matter: p = 0.016, 34% increase; white matter: p = 0.016, 32% increase) and CNR were higher (p = 0.016) in the four versus two RF coils setups (18.0± 1.8 vs. 13.9± 1.8). Qualitative evaluation of T1w, T2w, ASL, and dMR images resulted in acceptable to good image quality and did not differ statistically significantly between setups. Only the nonweighted diffusion image maps and corticospinal tract reconstructions yielded higher image quality and reduced susceptibility artifacts with four RF coils. Advanced ioMRI metrics were more precise with four RF coils as the standard deviation decreased. Taken together, we have investigated the practical use of advanced ioMRI during pediatric neurosurgery. We conclude that ASL CBF quantification in the surgical prone position is valid and that ASL and dMRI acquisition with two RF coils can be performed adequately for clinical use. With four versus two RF coils, the SNR of the images increases, and the sensitivity to artifacts reduces.

Assessing the pulmonary vascular responsiveness to oxygen with proton MRI.

Ventilation-perfusion matching occurs passively and is also actively regulated through hypoxic pulmonary vasoconstriction (HPV). The extent of HPV activity in humans, particularly normal subjects, is uncertain. Current evaluation of HPV assesses changes in ventilation-perfusion relationships/pulmonary vascular resistance with hypoxia and is invasive, or unsuitable for patients because of safety concerns. We used a noninvasive imaging-based approach to quantify the pulmonary vascular response to oxygen as a metric of HPV by measuring perfusion changes between breathing 21% and 30%O2 using arterial spin labeling (ASL) MRI. We hypothesized that the differences between 21% and 30%O2 images reflecting HPV release would be 1) significantly greater than the differences without [Formula: see text] changes (e.g., 21-21% and 30-30%O2) and 2) negatively associated with ventilation-perfusion mismatch. Perfusion was quantified in the right lung in normoxia (baseline), after 15 min of 30% O2 breathing (hyperoxia) and 15 min normoxic recovery (recovery) in healthy subjects (7 M, 7 F; age = 41.4 ± 19.6 yr). Normalized, smoothed, and registered pairs of perfusion images were subtracted and the mean square difference (MSD) was calculated. Separately, regional alveolar ventilation and perfusion were quantified from specific ventilation, proton density, and ASL imaging; the spatial variance of ventilation-perfusion (σ2V̇a/Q̇) distributions was calculated. The O2-responsive MSD was reproducible (R2 = 0.94, P < 0.0001) and greater (0.16 ± 0.06, P < 0.0001) than that from subtracted images collected under the same [Formula: see text] (baseline = 0.09 ± 0.04, hyperoxia = 0.08 ± 0.04, recovery = 0.08 ± 0.03), which were not different from one another (P = 0.2). The O2-responsive MSD was correlated with σ2V̇a/Q̇ (R2 = 0.47, P = 0.007). These data suggest that active HPV optimizes ventilation-perfusion matching in normal subjects. This noninvasive approach could be applied to patients with different disease phenotypes to assess HPV and ventilation-perfusion mismatch.NEW & NOTEWORTHY We developed a new proton MRI method to noninvasively quantify the pulmonary vascular response to oxygen. Using a hyperoxic stimulus to release HPV, we quantified the resulting redistribution of perfusion. The differences between normoxic and hyperoxic images were greater than those between images without [Formula: see text] changes and negatively correlated with ventilation-perfusion mismatch. This suggests that active HPV optimizes ventilation-perfusion matching in normal subjects. This approach is suitable for assessing patients with different disease phenotypes.

Arterial transit artifact as a short-term prognostic indicator in acute ischemic stroke

BackgroundArterial transit artifact (ATA) observed on arterial spin labeling (ASL) was recently suggested to be associated with improved functional outcomes following acute ischemic stroke (AIS). AIS is a heterogeneous disease with diverse pathogenic mechanisms depending on the stroke subtype. This study aimed to investigate the association between ATA and 3-month functional outcomes in AIS patients according to etiology subtypes.MethodsConsecutive patients with AIS were included. All patients underwent ASL MRI with postlabeling delay (PLD) of 1.5 and 2.5 s. ATA was assessed from the ASL images of both PLDs. Stroke etiologic subtypes were determined according to the modified TOAST (Trial of ORG 10172 in Acute Stroke Treatment) classification. Short-term functional outcomes were evaluated using the 3-month modified Rankin scale (mRS). Log-binomial regression was applied to analyze the association between ATA and functional outcomes at 3 months after stroke.ResultsNinety-eight AIS patients (62.73 ± 13.05 years; 68 men) were finally included. ATA was detected in forty-six patients and most frequently seen in the large-artery atherosclerosis (LAA) subtype (35/46). The ATA group exhibited a lower percentage of patients with mRS > 2 compared to the group without ATA (36.5% vs. 19.6%; P < 0.001). ATA was independently associated with better 3-month clinical outcomes (adjusted risk ratio, 0.35[95% CI, 0.16—0.74]) in the multivariate log-binomial regression model. After stratification by TOAST subtypes, a significant association was found between ATA and better outcomes in the LAA subtype (adjusted risk ratio, 0.20[ 95% CI, 0.05—0.72]) but not in cardioembolism and small artery occlusion (SVO) subtype.ConclusionATA is associated with better outcomes at 3 months in patients with AIS, especially in the LAA subtype, but this association attenuated in the cardioembolism and SVO subtypes.

Abstract TMP55: Arterial Spin Labeling Study Immediately After Thrombectomy: A Mechanism of Poor Prognosis Despite Recanalization

Introduction: In thrombectomy, the mechanism of poor prognosis despite complete recanalization is still unclear. Hyperperfusion may be a such poor prognostic mechanism. Residual microcirculatory dysfunction after restored large artery blood flow (no-reflow phenomenon) may also be a potential mechanism. MRI with arterial spin labeling (ASL) can easily assess cerebral perfusion. We here investigated the mechanism of poor prognosis despite recanalization by analyzing ASL images immediately after thrombus retrieval. Methods: This study included 41 consecutive cases (July 2019 to July 2023) with ICA or M1 embolic occlusions who underwent successful thrombectomy (mTICI3) and immediate post-operative ASL-MRI. Regional cerebral blood flow (CBF) on the ASL images were automatically quantified by means of 3DSRT software using 318 constant ROIs classified into 12 segments in each hemisphere. We evaluated the contralesional CBF ratio not only for the entire middle cerebral artery area and each of its segments, but also for each 3DSRT ROIs around the central sulcus (central arterial segment including 28 ROIs). These results of the post-operative ASL evaluation were compared between the favorable prognosis group (mRS 0-2 at 3 months) and the poor prognosis group (mRS 3-6). Results: There was no difference between the poor prognosis group (n=14) and the favorable prognosis group (n=27) in the comparison of the contralesional CBF ratio for the entire middle cerebral artery area or for each segment. However, the number of ROIs in the central segment decreased by 10% CBF or more and by 20% CBF or more compared to the contralesional side were significantly higher (both p&lt;0.01) in the poor prognosis group (19.1% against 11.8%, 3.1% against 0%, respectively). There was no difference in comparing the number of ROIs with increased CBF. Conclusions: This study showed that a high number of small-area (ROI) circulatory dysfunction (suggesting no-reflow phenomenon) was associated with a poor prognosis despite complete recanalization.

Evaluation of Kidney Injury Using Arterial Spin Labeling and Blood Oxygen Level-Dependent MRI: An Experimental Study in Rats With Carbon Tetrachloride-Induced Liver Cirrhosis.

Serum creatinine (Scr) may be not suited to timely and accurately reflect kidney injury related to chronic liver disease. Currently, the ability of arterial spin labeling (ASL) and blood oxygen level-dependent (BOLD) sequences to evaluate renal blood flow (RBF) and blood oxygen in chronic liver disease remains to be verified. To investigate the value of ASL and BOLD imaging in evaluating hemodynamics and oxygenation changes during kidney injury in an animal model of chronic liver disease. Prospective. Chronic liver disease model was established by subcutaneous injection of carbon tetrachloride. Forty-three male Sprague-Dawley rats (8 weeks) were divided into a pathological group (0, 2, 4, 6, 8, 12 weeks, each group: N = 6) and a continuous-scanning group (N = 7). 3-T, ASL, BOLD, and T2W. Regions of interest in the cortex (CO), outer stripe of the outer medulla (OSOM), and inner stripe of the outer medulla (ISOM) are manually delineated. The RBF and T2* values at each time point (0, 2, 4, 6, 8, 12 weeks) are measured and compared. Hematoxylin-eosin score (HE Score, damage area scoring method), alpha-smooth muscle actin (α-SMA), hypoxia-inducible factor-1alpha (HIF-1α), peritubular capillar (PTC) density, Scr, and neutrophil gelatinase-associated lipocalin were harvested. Analysis of variance, Spearman correlation analysis, Kruskal-Wallis tests, and receiver operating characteristic analysis with the area under the curve (AUC). A P-value <0.05 was considered statistically significant. Renal RBF and T2* values of CO, OSOM, and ISOM were significantly different from baseline. Both RBF and T2* were significantly correlated with HE Score, α-SMA, HIF-1α, and PTC density (|r| = 0.406-0.853). RBF demonstrated superior diagnostic capability in identifying severe kidney injury in this model of chronic liver disease (AUC = 0.964). Imaging by ASL and BOLD may detect renal hemodynamics and oxygenation changes related to chronic liver disease early. 5 TECHNICAL EFFICACY: Stage 2.

Diagnostic and Prognostic Potential of Multiparametric Renal MRI in Kidney Transplant Patients.

Multiparametric MRI provides assessment of functional and structural parameters in kidney allografts. It offers a non-invasive alternative to the current reference standard of kidney biopsy. To evaluate the diagnostic and prognostic utility of MRI parameters in the assessment of allograft function in the first 3-months post-transplantation. Prospective. 32 transplant recipients (54 ± 17 years, 20 females), divided into two groups according to estimated glomerular filtration rate (eGFR) at 3-months post-transplantation: inferior graft function (IGF; eGFR<45 mL/min/1.73 m2 , n = 10) and superior graft function (SGF; eGFR ≥ 45 mL/min/1.73 m2 , n = 22). Further categorization was based on the need for hemodialysis (C1) and decrease in s-creatinine (C2) at 1-week post-transplantation: delayed-graft-function (DGF: n = 4 C1, n = 10 C2) and early graft-function (EGF: n = 28 C1, n = 22 C2). 3-T, pseudo-continuous arterial spin labeling, T1-mapping, and diffusion-weighted imaging. Multiparametric MRI was evaluated at 1-week in all patients and 3-months after transplantation in 28 patients. Renal blood flow (RBF), diffusion coefficients (ADC, ΔADC, D, D, D*, flowing fraction f), T1 and T1 were calculated in cortex and medulla. The diagnostic and prognostic value of these parameters, obtained at 3-months and 1-week post-transplantation, respectively, was evaluated in the cortex to discriminate between DGF and EGF, and between SGF and IGF. Logistic regression, receiver-operating-characteristics, area-under-the-curve (AUC), confidence intervals (CIs), analysis-of-variance, t-test, Wilcoxon-Mann-Whitney test, Fisher's exact test, Pearson's correlation. P-value<0.05 was considered significant. DGF patients exhibited significantly lower cortical RBF and f and higher D*. The diagnostic value of MRI for detecting DGF was excellent (AUC = 100%). Significant differences between patients with IGF and SGF were found in RBF, ∆T1 , and ∆D. Multiparametric MRI showed higher diagnostic (AUC = 95.32%; CI: 88%-100%) and prognostic (AUC = 97.47%, CI: 92%-100%) values for detecting IGF than eGFR (AUC = 89.50%, CI: 79%-100%). Multiparametric MRI may show high diagnostic and prognostic value in transplanted patients, yielding better results compared to eGFR measurements. 2 TECHNICAL EFFICACY: Stage 1.

MRI Assessment of Cerebral White Matter Microvascular Hemodynamics Across the Adult Lifespan.

Changes in cerebral hemodynamics with aging are important for understanding age-related variation in neuronal health. While many prior studies have focused on gray matter, less is known regarding white matter due in part to measurement challenges related to the lower vascular density in white matter. To investigate the impact of age and sex on white matter hemodynamics in a Human Connectome Project in Aging (HCP-A) cohort using tract-based spatial statistics (TBSS). Retrospective cross-sectional. Six hundred seventy-eight typically aging individuals (381 female), aged 36-100 years. Multi-delay pseudo-continuous arterial spin labeling (ASL) and diffusion-weighted pulsed-gradient spin-echo echo planar imaging sequences at 3.0 T. A skeleton of mean fractional anisotropy (FA) was produced using TBSS. This skeleton was used to project ASL-derived cerebral blood flow (CBF) and arterial transit time (ATT) measures onto white matter tracts. General linear models were applied to white matter FA, CBF, and ATT maps, while covarying for age and sex. Threshold-free cluster enhancement multiple comparisons correction was performed for the effects of age and sex, thresholded at PFWE < 0.05. CBF, ATT, and FA were compared between sex for each tract using analysis of covariance, with multiple comparisons correction for the number of tracts at PFDR < 0.05. Significantly lower white matter CBF and significantly prolonged white matter ATTs were associated with older age. These effects were widespread across tracts for ATT. Significant (PFDR < 0.05) sex differences in ATT were observed across all tracts, and significant sex differences in CBF were observed in all tracts except the bilateral uncinate fasciculus. Females demonstrated significantly higher CBF compared to males across the lifespan. Few tracts demonstrated significant sex differences in FA. This study identified significant sex- and age-associated differences in white matter hemodynamics across tracts. 3 TECHNICAL EFFICACY: Stage 3.