Deep Learning for Perfusion Cerebral Blood Flow (CBF) and Volume (CBV) Predictions and Diagnostics.

Dynamic susceptibility contrast magnetic resonance perfusion (DSC-MRP) is a non-invasive imaging technique for hemodynamic measurements. Various perfusion parameters, such as cerebral blood volume (CBV) and cerebral blood flow (CBF), can be derived from DSC-MRP, hence this non-invasive imaging protocol is widely used clinically for the diagnosis and assessment of intracranial pathologies. Currently, most institutions use commercially available software to compute the perfusion parametric maps. However, these conventional methods often have limitations, such as being time-consuming and sensitive to user input, which can lead to inconsistent results; this highlights the need for a more robust and efficient approach like deep learning. Using the relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) perfusion maps generated by FDA-approved software, we trained a multistage deep learning model. The model, featuring a combination of a 1D convolutional neural network (CNN) and a 2D U-Net encoder-decoder network, processes each 4D MRP dataset by integrating temporal and spatial features of the brain for voxel-wise perfusion parameters prediction. An auxiliary model, with similar architecture, but trained with truncated datasets that had fewer time-points, was designed to explore the contribution of temporal features. Both qualitatively and quantitatively evaluated, deep learning-generated rCBV and rCBF maps showcased effective integration of temporal and spatial data, producing comprehensive predictions for the entire brain volume. Our deep learning model provides a robust and efficient approach for calculating perfusion parameters, demonstrating comparable performance to FDA-approved commercial software, and potentially mitigating the challenges inherent to traditional techniques.

Prediction of Intracranial Atherosclerotic Disease-Related Large-Vessel Occlusion Stroke on the Basis of Novel Cerebral Blood Volume Parameters.

BACKGROUND: Mechanical thrombectomy is an effective treatment method for large-vessel occlusion stroke (LVOS); however, it has limited efficacy for intracranial atherosclerotic disease (ICAD)-related LVOS. We investigated the use of cerebral blood volume (CBV) maps for identifying ICAD as the underlying cause of LVOS before the initiation of endovascular treatment (EVT). METHODS AND RESULTS: We reviewed clinical and imaging data from patients who presented with LVOS and underwent endovascular treatment between January 2011 and May 2021. The CBV patterns were analyzed to identify an increase in CBV within the hypoperfused area and estimate infarct patterns within the area of decreased CBV. Comparisons were made between the patients with an increase in CBV and those without, and among the estimated infarct patterns: territorial, cortical wedge, basal ganglia-only, subcortical, and normal CBV. Overall, 243 patients were included. CBV increase in the hypoperfused area was observed in 23.5% of patients. A significantly higher proportion of ICAD was observed in those with increased CBV than in those without (56.4% versus 19.8%; P<0.001). Regarding the estimated infarct patterns on the CBV, ICAD was most frequently observed in the normal CBV group (territorial, 14.9%; cortical wedge, 10.0%; basal ganglia-only, 43.8%; subcortical, 35.7%; normal, 61.7%). CBV parameters, including "an increase in CBV," "normal CBV infarct pattern," and "an increase in CBV or normal CBV infarct pattern composite," were independently associated with ICAD. CONCLUSIONS: An increased CBV or normal CBV pattern may be associated with ICAD LVOS on the pretreatment perfusion imaging.

Cerebral Microvascular Perfusion Assessed in Elderly Adults by Spin-Echo Dynamic Susceptibility Contrast MRI at 7 Tesla.

Perfusion measures of the total vasculature are commonly derived with gradient-echo (GE) dynamic susceptibility contrast (DSC) MR images, which are acquired during the early passes of a contrast agent. Alternatively, spin-echo (SE) DSC can be used to achieve specific sensitivity to the capillary signal. For an improved contrast-to-noise ratio, ultra-high-field MRI makes this technique more appealing to study cerebral microvascular physiology. Therefore, this study assessed the applicability of SE-DSC MRI at 7 T. Forty-one elderly adults underwent 7 T MRI using a multi-slice SE-EPI DSC sequence. The cerebral blood volume (CBV) and cerebral blood flow (CBF) were determined in the cortical grey matter (CGM) and white matter (WM) and compared to values from the literature. The relation of CBV and CBF with age and sex was investigated. Higher CBV and CBF values were found in CGM compared to WM, whereby the CGM-to-WM ratios depended on the amount of largest vessels excluded from the analysis. CBF was negatively associated with age in the CGM, while no significant association was found with CBV. Both CBV and CBF were higher in women compared to men in both CGM and WM. The current study verifies the possibility of quantifying cerebral microvascular perfusion with SE-DSC MRI at 7 T.

Breath-hold BOLD fMRI without CO2 sampling enables estimation of venous cerebral blood volume: potential use in normalization of stimulus-evoked BOLD fMRI data.

BOLD fMRI signal has been used in conjunction with vasodilatory stimulation as a marker of cerebrovascular reactivity (CVR): the relative change in cerebral blood flow (CBF) arising from a unit change in the vasodilatory stimulus. Using numerical simulations, we demonstrate that the variability in the relative BOLD signal change induced by vasodilation is strongly influenced by the variability in deoxyhemoglobin-containing cerebral blood volume (CBV), as this source of variability is likely to be more prominent than that of CVR. It may, therefore, be more appropriate to describe the relative BOLD signal change induced by an isometabolic vasodilation as a proxy of deoxygenated CBV (CBVdHb) rather than CVR. With this in mind, a new method was implemented to map a marker of CBVdHb, termed BOLD-CBV, based on the normalization of voxel-wise BOLD signal variation by an estimate of the intravascular venous BOLD signal from voxels filled with venous blood. The intravascular venous BOLD signal variation, recorded during repeated breath-holding, was extracted from the superior sagittal sinus in a cohort of 27 healthy volunteers and used as a regressor across the whole brain, yielding maps of BOLD-CBV. In the same cohort, we demonstrated the potential use of BOLD-CBV for the normalization of stimulus-evoked BOLD fMRI by comparing group-level BOLD fMRI responses to a visuomotor learning task with and without the inclusion of voxel-wise vascular covariates of BOLD-CBV and the BOLD signal change per mmHg variation in end-tidal carbon dioxide (BOLD-CVR). The empirical measure of BOLD-CBV accounted for more between-subject variability in the motor task-induced BOLD responses than BOLD-CVR estimated from end-tidal carbon dioxide recordings. The new method can potentially increase the power of group fMRI studies by including a measure of vascular characteristics and has the strong practical advantage of not requiring experimental measurement of end-tidal carbon dioxide, unlike traditional methods to estimate BOLD-CVR. It also more closely represents a specific physiological characteristic of brain vasculature than BOLD-CVR, namely blood volume.

Reproducibility of rCBV in glioblastomas using T2*-weighted perfusion MRI: an evaluation of sampling, normalization, and experience.

PURPOSE: The reproducibility of relative cerebral blood volume (rCBV) measurements among readers with different levels of experience is a concern. This study aimed to investigate the inter-reader reproducibility of rCBV measurement of glioblastomas using the hotspot method in dynamic susceptibility contrast perfusion magnetic resonance imaging (DSC-MRI) with various strategies. METHODS: In this institutional review board-approved single-center study, 30 patients with glioblastoma were retrospectively evaluated with DSC-MRI at a 3.0 Tesla scanner. Three groups of reviewers, including neuroradiologists, general radiologists, and radiology residents, calculated the rCBV based on the number of regions of interest (ROIs) and reference areas. For statistical analysis of feature reproducibility, the intraclass correlation coefficient (ICC) and Bland-Altman plots were used. Analyses were made among individuals, reader groups, reader-group pooling, and a population that contained all of them. RESULTS: For individuals, the highest inter-reader reproducibility was observed between neuroradiologists [ICC: 0.527; 95% confidence interval (CI): 0.21-0.74] and between residents (ICC: 0.513; 95% CI: 0.20-0.73). There was poor reproducibility in the analyses of individuals with different levels of experience (ICC range: 0.296-0.335) and in reader-wise and group-wise pooling (ICC range: 0.296-0.335 and 0.397-0.427, respectively). However, an increase in ICC values was observed when five ROIs were used. In an analysis of all strategies, the ICC for the centrum semiovale was significantly higher than that for contralateral white matter (P < 0.001). CONCLUSION: The inter-reader reproducibility of rCBV measurement was poor to moderate regardless of whether it was calculated by neuroradiologists, general radiologists, or residents, which may indicate the need for automated methods. Choosing five ROIs and using the centrum semiovale as a reference area may increase reliability for all users.

Precision and normal values of cerebral blood volume in preterm neonates using time-resolved near-infrared spectroscopy.

AIM: To investigate cerebral blood volume (CBV) in preterm neonates using time-resolved near-infrared spectroscopy. METHODS: In this prospective observational study, time-resolved near-infrared spectroscopy measurements of CBV using tNIRS-1 were performed in 70 preterm neonates. For measurements, a sensor was placed for a duration of 1 min, followed by four further reapplications of the sensor, overall five measurements. RESULTS: In this study, 70 preterm neonates with a mean ± SD gestational age of 33.4 ± 1.7 weeks and a birthweight of 1931 ± 398 g were included with a postnatal age of 4.7 ± 2.0 days. Altogether, 2383 CBV values were obtained with an overall mean of 1.85 ± 0.30 mL/100 g brain. A total of 95% of the measured CBV values varied in a range from -0.31 to 0.33 from the overall individual mean. Taking the deviation of the mean of each single application for each patient, this range reduced from -0.07 to 0.07. The precision of the measurement defined as within-variation in CBV was 0.24 mL/100 g brain. CONCLUSION: The overall mean CBV in stable preterm neonates was 1.85 ± 0.30 mL/100 g brain. The within-variation in CBV was 0.24 mL/100 g brain. Based on the precision obtained by our data, CBV of 1.85 ± 0.30 mL/100 g brain may be assumed as normal value for this cohort.

Tumor treating fields increases blood-brain barrier permeability and relative cerebral blood volume in patients with glioblastoma.

BACKGROUND AND OBJECTIVE: 200 kHz tumor treating fields (TTFields) is clinically approved for newly-diagnosed glioblastoma (nGBM). Because its effects on conventional surveillance MRI brain scans are equivocal, we investigated its effects on perfusion MRI (pMRI) brain scans. METHODS: Each patient underwent institutional standard pMRI: dynamic contrast-enhanced (DCE) and dynamic susceptibility contrast (DSC) pMRI at three time points: baseline, 2-, and 6-months on-adjuvant therapy. At each timepoint, the difference between T1 pre- versus post-contrast tumor volume (ΔT1) and these pMRI metrics were evaluated: normalized and standardized relative cerebral blood volume (nRCBV, sRCBV); fractional plasma volume (Vp), volume of extravascular extracellular space (EES) per volume of tissue (Ve), blood-brain barrier (BBB) permeability (Ktrans), and time constant for gadolinium reflux from EES back into the vascular system (Kep). Between-group comparisons were performed using rank-sum analysis, and bootstrapping evaluated likely reproducibility of the results. RESULTS: Among 13 pMRI datasets (11 nGBM, 2 recurrent GBM), therapies included temozolomide-only (n = 9) and temozolomide + TTFields (n = 4). No significant differences were found in patient or tumor characteristics. Compared to temozolomide-only, temozolomide + TTFields did not significantly affect the percent-change in pMRI metrics from baseline to 2 months. But during the 2- to 6-month period, temozolomide + TTFields significantly increased the percent-change in nRCBV (+26.9% [interquartile range 55.1%] vs -39.1% [37.0%], p = 0.049), sRCBV (+9.5% [39.7%] vs -30.5% [39.4%], p = 0.049), Ktrans (+54.6% [1768.4%] vs -26.9% [61.2%], p = 0.024), Ve (+111.0% [518.1%] vs -13.0% [22.5%], p = 0.048), and Vp (+98.8% [2172.4%] vs -24.6% [53.3%], p = 0.024) compared to temozolomide-only. CONCLUSION: Using pMRI, we provide initial in-human validation of pre-clinical studies regarding the effects of TTFields on tumor blood volume and BBB permeability in GBM.

On the optimization of 3D inflow-based vascular-space-occupancy (iVASO) MRI for the quantification of arterial cerebral blood volume (CBVa).

PURPOSE: The inflow-based vascular-space-occupancy (iVASO) MRI was originally developed in a single-slice mode to measure arterial cerebral blood volume (CBVa). When vascular crushers are applied in iVASO, the signals can be sensitized predominantly to small pial arteries and arterioles. The purpose of this study is to perform a systematic optimization and evaluation of a 3D iVASO sequence on both 3 T and 7 T for the quantification of CBVa values in the human brain. METHODS: Three sets of experiments were performed in three separate cohorts. (1) 3D iVASO MRI protocols were compared to single-slice iVASO, and the reproducibility of whole-brain 3D iVASO MRI was evaluated. (2) The effects from different vascular crushers in iVASO were assessed. (3) 3D iVASO MRI results were evaluated in arterial and venous blood vessels identified using ultrasmall-superparamagnetic-iron-oxides-enhanced MRI to validate its arterial origin. RESULTS: 3D iVASO scans showed signal-to-noise ratio (SNR) and CBVa measures consistent with single-slice iVASO with reasonable intrasubject reproducibility. Among the iVASO scans performed with different vascular crushers, the whole-brain 3D iVASO scan with a motion-sensitized-driven-equilibrium preparation with two binomial refocusing pulses and an effective TE of 50 ms showed the best suppression of macrovascular signals, with a relatively low specific absorption rate. When no vascular crusher was applied, the CBVa maps from 3D iVASO scans showed large CBVa values in arterial vessels but well-suppressed signals in venous vessels. CONCLUSION: A whole-brain 3D iVASO MRI scan was optimized for CBVa measurement in the human brain. When only microvascular signals are desired, a motion-sensitized-driven-equilibrium-based vascular crusher with binomial refocusing pulses can be applied in 3D iVASO.

Dynamics of cerebral blood volume during and after middle cerebral artery occlusion in rats - Comparison between ultrafast ultrasound and dynamic susceptibility contrast-enhanced MRI measurements.

Tomographic perfusion imaging techniques are integral to translational stroke research paradigms that advance our understanding of the disease. Functional ultrasound (fUS) is an emerging technique that informs on cerebral blood volume (CBV) through ultrasensitive Doppler and flow velocity (CBFv) through ultrafast localization microscopy. It is not known how experimental results compare with a classical CBV-probing technique such as dynamic susceptibility contrast-enhanced perfusion MRI (DSC-MRI). To that end, we assessed hemodynamics based on uUS (n = 6) or DSC-MRI (n = 7) before, during and up to three hours after 90-minute filament-induced middle cerebral artery occlusion (MCAO) in rats. Recanalization was followed by a brief hyperperfusion response, after which CBV and CBFv temporarily normalized but progressively declined after one hour in the lesion territory. DSC-MRI data corroborated the incomplete restoration of CBV after recanalization, which may have been caused by the free-breathing anesthetic regimen. During occlusion, MCAO-induced hypoperfusion was more discrepant between either technique, likely attributable to artefactual signal mechanisms related to slow flow, and processing algorithms employed for either technique. In vivo uUS- and DSC-MRI-derived measures of CBV enable serial whole-brain assessment of post-stroke hemodynamics, but readouts from both techniques need to be interpreted cautiously in situations of very low blood flow.

Cerebral blood volume index can predict the long-term prognosis after endovascular thrombectomy in patients with acute ischemic stroke due to large vessel occlusion.

Long-term prognosis and factors influencing endovascular therapy (EVT) remain unclear. This study aimed to investigate the association between computed tomography perfusion (CTP) parameters and long-term prognosis of patients with acute ischemic stroke (AIS) treated with EVT. Patients with AIS due to large vessel occlusion treated with EVT were prospectively included for a 1-year follow-up. All patients and their data were grouped based on the hypoperfusion intensity ratio (HIR, ＜0.3 vs. ≥ 0.3) and cerebral blood volume (CBV) index (＞0.7 vs. ≤ 0.7). The primary outcome was favorable prognosis, defined as a modified Rankin Scale (mRS) score of 0-2. Multivariate logistic regression was used to analyze factors influencing long-term favorable prognosis. Of 69 patients included, 35 (50.7 %) achieved mRS 0-2 at one year. A favorable prognosis was observed predominantly in patients with higher CBV index (75.0 % vs. 34.1 %, p= 0.001) and lower HIR (72.0 % vs. 38.6 %, p=0.008). In the multivariate logistic regression, CBV index (odds ratio (OR) = 4.362; 95 % confidence interval (CI): 1.052, 18.082; p = 0.042), baseline National Institutes of Health Stroke Scale (NIHSS) score (OR = 0.913; 95 % CI: 0.836, 0.997; p = 0.044), and symptomatic intracranial hemorrhage (sICH) (OR = 0.089; 95 % CI: 0.009, 0.925; p = 0.043) were independently associated with a long-term favorable prognosis. The CBV index may serve as a predictor of the long-term prognosis of patients treated with EVT. The novel finding is that the baseline NIHSS score and sICH were associated with long-term prognosis.

Experimenting with ASL-based arterialized cerebral blood volume as a novel imaging biomarker in grading glial neoplasms.

BACKGROUND: Perfusion imaging is one of the methods used to grade glial neoplasms, and in this study we evaluated the role of ASL perfusion in grading brain glioma. PURPOSE: The aim is to evaluate the role of arterialized cerebral blood volume (aCBV) of multi-delay ASL perfusion for grading glial neoplasm. MATERIALS AND METHODS: This study is a prospective observational study of 56 patients with glial neoplasms of the brain who underwent surgery, and only cases with positive diagnosis of glioma are included to evaluate the novel diagnostic parameter. RESULTS: In the study, ASL-derived normalized aCBV (naCBV) and T2*DSC-derived normalized CBV (nCBV) are showing very high correlation (Pearson's correlation coefficient value of 0.94) in grading glial neoplasms. naCBV and nCBF are also showing very high correlation (Pearson's correlation coefficient value of 0.876). The study also provides cutoff values for differentiating LGG from HGG for normalized aCBV(naCBV) of ASL, normalized CBV (nCBV), and normalized nCBF derived from T2* DCS as 1.12, 1.254, and 1.31, respectively. ASL-derived aCBV also shows better diagnostic accuracy than ASL-derived CBF. CONCLUSION: This study is one of its kind to the best of our knowledge where multi-delay ASL perfusion-derived aCBV is used as a novel imaging biomarker for grading glial neoplasms, and it has shown high statistical correlation with T2* DSC-derived perfusion parameters.

Quantitative Cerebral Blood Volume Image Synthesis from Standard MRI Using Image-to-Image Translation for Brain Tumors.

Background Cerebral blood volume (CBV) maps derived from dynamic susceptibility contrast-enhanced (DSC) MRI are useful but not commonly available in clinical scenarios. Purpose To test image-to-image translation techniques for generating CBV maps from standard MRI sequences of brain tumors using the bookend technique DSC MRI as ground-truth references. Materials and Methods A total of 756 MRI examinations, including quantitative CBV maps produced from bookend DSC MRI, were included in this retrospective study. Two algorithms, the feature-consistency generative adversarial network (GAN) and three-dimensional encoder-decoder network with only mean absolute error loss, were trained to synthesize CBV maps. The performance of the two algorithms was evaluated quantitatively using the structural similarity index (SSIM) and qualitatively by two neuroradiologists using a four-point Likert scale. The clinical value of combining synthetic CBV maps and standard MRI scans of brain tumors was assessed in several clinical scenarios (tumor grading, prognosis prediction, differential diagnosis) using multicenter data sets (four external and one internal). Differences in diagnostic and predictive accuracy were tested using the z test. Results The three-dimensional encoder-decoder network with T1-weighted images, contrast-enhanced T1-weighted images, and apparent diffusion coefficient maps as the input achieved the highest synthetic performance (SSIM, 86.29% ± 4.30). The mean qualitative score of the synthesized CBV maps by neuroradiologists was 2.63. Combining synthetic CBV with standard MRI improved the accuracy of grading gliomas (standard MRI scans area under the receiver operating characteristic curve [AUC], 0.707; standard MRI scans with CBV maps AUC, 0.857; z = 15.17; P < .001), prediction of prognosis in gliomas (standard MRI scans AUC, 0.654; standard MRI scans with CBV maps AUC, 0.793; z = 9.62; P < .001), and differential diagnosis between tumor recurrence and treatment response in gliomas (standard MRI scans AUC, 0.778; standard MRI scans with CBV maps AUC, 0.853; z = 4.86; P < .001) and brain metastases (standard MRI scans AUC, 0.749; standard MRI scans with CBV maps AUC, 0.857; z = 6.13; P < .001). Conclusion GAN image-to-image translation techniques produced accurate synthetic CBV maps from standard MRI scans, which could be used for improving the clinical evaluation of brain tumors. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Branstetter in this issue.

Longitudinal Assessment of Cerebral Blood Volume Variation in Human Neonates Using Ultrafast Power Doppler and Diverging Waves.

Longitudinal assessment of brain perfusion is a critical parameter for neurodevelopmental outcome of neonates undergoing cardiopulmonary bypass procedure. In this study, we aim to measure the variations of cerebral blood volume (CBV) in human neonates during cardiac surgery, using Ultrafast Power Doppler and freehand scanning. To be clinically relevant, this method must satisfy three criteria: being able to image a wide field of view in the brain, show significant longitudinal CBV variations, and present reproducible results. To address the first point, we performed for the first time transfontanellar Ultrafast Power Doppler using a hand-held phased-array transducer with diverging waves. This increased the field of view more than threefold compared to previous studies using linear transducers and plane waves. We were able to image vessels in the cortical areas as well as the deep grey matter and temporal lobes. Second, we measured the longitudinal variations of CBV on human neonates undergoing cardiopulmonary bypass. When compared to a pre-operative baseline acquisition, the CBV exhibited significant variation during bypass: on average, + 20±3 % in the mid-sagittal full sector ( [Formula: see text]), - 11±3 % in the cortical regions ( [Formula: see text]) and - 10±4 % in the basal ganglia ( [Formula: see text]). Third, a trained operator performing identical scans was able to reproduce CBV estimates with a variability of 4% to 7.5% depending on the regions considered. We also investigated whether vessel segmentation could further improve reproducibility, but found that it actually introduced greater variability in the results. Overall, this study demonstrates the clinical translation of ultrafast power Doppler with diverging-waves and freehand scanning.

Co-variations of cerebral blood volume and single neurons discharge during resting state and visual cognitive tasks in non-human primates.

To better understand how the brain allows primates to perform various sets of tasks, the ability to simultaneously record neural activity at multiple spatiotemporal scales is challenging but necessary. However, the contribution of single-unit activities (SUAs) to neurovascular activity remains to be fully understood. Here, we combine functional ultrasound imaging of cerebral blood volume (CBV) and SUA recordings in visual and fronto-medial cortices of behaving macaques. We show that SUA provides a significant estimate of the neurovascular response below the typical fMRI spatial resolution of 2mm3. Furthermore, our results also show that SUAs and CBV activities are statistically uncorrelated during the resting state but correlate during tasks. These results have important implications for interpreting functional imaging findings while one constructs inferences of SUA during resting state or tasks.

Relationship of cerebral blood volume with arterial and venous flow velocities in extremely low-birth-weight infants.

Unstable cerebral blood flow is theorised to contribute to the occurrence of intraventricular haemorrhage (IVH) in extremely low-birth-weight infants (ELBWIs), which can be caused by increased arterial flow, increased venous pressure, and impaired autoregulation of brain vasculature. As a preliminary step to investigate such instability, we aimed to check for correlations of cerebral blood volume (CBV), as measured using near-infrared spectroscopy, with the flow velocities of the anterior cerebral artery (ACA) and internal cerebral vein (ICV), as measured using Doppler ultrasonography. Data were retrospectively analysed from 30 ELBWIs uncomplicated by symptomatic patent ductus arteriosus, which can influence ACA velocity, and severe IVH (grade ≥ 3), which can influence ICV velocity and CBV. The correlation between tissue oxygen saturation (StO2) and mean blood pressure was also analysed as an index of autoregulation. CBV was not associated with ACA velocity; however, it was significantly correlated with ICV velocity (Pearson R = 0.59 [95% confidence interval: 0.29-0.78], P = 0.00061). No correlation between StO2 and mean blood pressure was observed, implying that autoregulation was not impaired.    Conclusion: Although our findings are based on the premise that cerebral autoregulation was unimpaired in the ELBWIs without complications, the same result cannot be directly applied to severe IVH cases. However, our results may aid future research on IVH prediction by investigating the changes in CBV when severe IVH occurs during ICV velocity fluctuation. What is Known: • The pathogenesis of IVH includes unstable cerebral blood flow affected by increased arterial flow, increased venous pressure, and impaired cerebral autoregulation. • The approaches that can predict IVH are under discussion. What is New: • ACA velocity is not associated with CBV, but ICV velocity is significantly correlated with CBV. • CBV measured using NIRS may be useful in future research on IVH prediction.

Cerebral blood volume sensitive layer-fMRI in the human auditory cortex at 7T: Challenges and capabilities.

The development of ultra high field fMRI signal readout strategies and contrasts has led to the possibility of imaging the human brain in vivo and non-invasively at increasingly higher spatial resolutions of cortical layers and columns. One emergent layer-fMRI acquisition method with increasing popularity is the cerebral blood volume sensitive sequence named vascular space occupancy (VASO). This approach has been shown to be mostly sensitive to locally-specific changes of laminar microvasculature, without unwanted biases of trans-laminar draining veins. Until now, however, VASO has not been applied in the technically challenging cortical area of the auditory cortex. Here, we describe the main challenges we encountered when developing a VASO protocol for auditory neuroscientific applications and the solutions we have adopted. With the resulting protocol, we present preliminary results of laminar responses to sounds and as a proof of concept for future investigations, we map the topographic representation of frequency preference (tonotopy) in the auditory cortex.

T1-Weighted Contrast Enhancement, Apparent Diffusion Coefficient, and Cerebral-Blood-Volume Changes after Glioblastoma Resection: MRI within 48 Hours vs. beyond 48 Hours.

BACKGROUND: The aim of the study is to identify the advantages, if any, of post-operative MRIs performed at 48 h compared to MRIs performed after 48 h in glioblastoma surgery. MATERIALS AND METHODS: To assess the presence of a residual tumor, the T1-weighted Contrast Enhancement (CE), Apparent Diffusion Coefficient (ADC), and Cerebral Blood Volume (rCBV) in the proximity of the surgical cavity were considered. The rCBV ratio was calculated by comparing the rCBV with the contralateral normal white matter. After the blind image examinations by the two radiologists, the patients were divided into two groups according to time window after surgery: ≤48 h (group 1) and >48 h (group 2). RESULTS: A total of 145 patients were enrolled; at the 6-month follow-up MRI, disease recurrence was 89.9% (125/139), with a mean patient survival of 8.5 months (SD 7.8). The mean ADC and rCBV ratio values presented statistical differences between the two groups (p < 0.05). Of these 40 patients in whom an ADC value was not obtained, the rCBV values could not be calculated in 52.5% (21/40) due to artifacts (p < 0.05). CONCLUSION: The study showed differences in CE, rCBV, and ADC values between the groups of patients undergoing MRIs before and after 48 h. An MRI performed within 48 h may increase the ability of detecting GBM by the perfusion technique with the calculation of the rCBV ratio.

Can angiographic Flat Detector Computed Tomography blood volume measurement be used to predict final infarct size in acute ischemic stroke?

INTRODUCTION AND PURPOSE: Flat detector computed tomography (FD-CT) technology is becoming more widely available in the angiography suites of comprehensive stroke centers. In patients with acute ischemic stroke (AIS), who are referred for endovascular therapy (EVT), FD-CT generates cerebral pooled blood volume (PBV) maps, which might help in predicting the final infarct area. We retrospectively analyzed pre- and post-recanalization therapy quantitative PBV measurements in both the infarcted and hypoperfused brain areas of AIS patients referred for EVT. MATERIALS AND METHODS: We included AIS patients with large vessel occlusion in the anterior circulation referred for EVT from primary stroke centers to our comprehensive stroke center. The pre- and post-recanalization FD-CT regional relative PBV (rPBV) values were measured between ipsilateral lesional and contralateral non-lesional areas based on final infarct area on post EVT follow-up cross-sectional imaging. Statistical analysis was performed to identify differences in PBV values between infarcted and non-infarcted, recanalized brain areas. RESULTS: We included 20 AIS patients. Mean age was 63 years (ranging from 36 to 86 years). The mean pre- EVT rPBV value was 0.57 (±0.40) for infarcted areas and 0.75 (±0.43) for hypoperfusion areas. The mean differences (Δ) between pre- and post-EVT rPBV values for infarcted and hypoperfused areas were respectively 0.69 (±0.59) and 0.69 (±0.90). We found no significant differences (p > 0.05) between pre-EVT rPBV and ΔrPBV values of infarct areas and hypoperfusion areas. CONCLUSION: Angiographic PBV mapping is useful for the detection of cerebral perfusion deficits, especially in combination with the fill run images. However, we were not able to distinguish irreversibly infarcted tissue from potentially salvageable, hypoperfused brain tissue based on quantitative PBV measurement in AIS patients.

Hypoperfusion intensity ratio and CBV index as predictive parameters to identify underlying intracranial atherosclerotic stenosis in endovascular thrombectomy.

BACKGROUND AND PURPOSE: Intracranial atherosclerotic stenosis (ICAS)-related large vessel occlusion (LVO) is difficult to diagnose before endovascular thrombectomy (EVT) in an emergency. We hypothesized that hypoperfusion intensity ratio (HIR) and cerebral blood volume (CBV) index reflect collateral flow and would be useful parameters to predict underlying ICAS. MATERIALS AND METHODS: Clinical and perfusion imaging parameters of patients receiving EVT for LVO were reviewed retrospectively. Patients were divided into ICAS and embolism groups with angiographical findings. The association between prespecified parameters and underlying ICAS were assessed using multivariable logistic regression analyses. Discriminative ability was assessed using receiver operating characteristic analysis. RESULTS: Among 238 consecutive patients, 47 satisfied the inclusion criteria, including 10 with ICAS-related LVO. In ROC analyses, HIR showed good discrimination with a cutoff value of 0.22 (area under the curve, 0.85; 95%CI, 0.75-0.96; sensitivity, 0.84; specificity, 0.80) for underlying ICAS. CBV index showed excellent discrimination with a cutoff value of 0.90 (area under the curve, 0.92; 95%CI, 0.81-0.98; sensitivity, 0.92; specificity, 0.79). Multivariable logistic regression analysis revealed that HIR ≤ 0.22 (OR, 22.5; 95%CI, 2.9-177.0; P = 0.003) and CBV index ≥ 0.9 (OR, 75.7; 95%CI, 5.8-994.0; P < 0.001) were significantly associated with underlying ICAS. CONCLUSION: HIR ≤ 0.22 and CBV index ≥ 0.9 were associated with underlying ICAS and may predict underlying ICAS before EVT.