Dynamic Susceptibility Contrast MRI Research Articles

Assessment of a simplified spin and gradient echo (sSAGE) approach for human brain tumor perfusion imaging

The goal of this study was to validate a simplified spin- and gradient-echo (sSAGE) approach to obtain T1-corrected dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) data in a clinical brain tumor population. A five-echo SAGE sequence was used to acquire DSC-MRI data (n=8 patients, 3 primary glioma, and 5 brain metastases). The ΔR2⁎ and ΔR2 time series obtained from a nonlinear fit of all echoes (SAGE) were compared to ΔR2⁎ and ΔR2 time series obtained analytically (sSAGE) using three echoes (two GEs and one SE). Through the use of multiple echoes, both methods removed T1 leakage effects from the ΔR2⁎ and ΔR2 time series, and the sSAGE ΔR2⁎ and ΔR2 time series were highly correlated with those from SAGE, with average correlations of 0.9. The resulting hemodynamic parameters included GE and SE cerebral blood volume (CBV), cerebral blood flow (CBF), mean vessel diameter (mVD), volume transfer constant (Ktrans), and volume fraction of the extravascular extracellular space (ve). For each metric, there was good correlation (>0.86) between sSAGE and SAGE, with no significant differences. The sSAGE method provides T1-corrected GE and SE DSC-MRI parameters in an efficient and clinically feasible manner.

Perfusion information extracted from resting state functional magnetic resonance imaging

It is widely known that blood oxygenation level dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) is an indirect measure for neuronal activations through neurovascular coupling. The BOLD signal is also influenced by many non-neuronal physiological fluctuations. In previous resting state (RS) fMRI studies, we have identified a moving systemic low frequency oscillation (sLFO) in BOLD signal and were able to track its passage through the brain. We hypothesized that this seemingly intrinsic signal moves with the blood, and therefore, its dynamic patterns represent cerebral blood flow. In this study, we tested this hypothesis by performing Dynamic Susceptibility Contrast (DSC) MRI scans (i.e. bolus tracking) following the RS scans on eight healthy subjects. The dynamic patterns of sLFO derived from RS data were compared with the bolus flow visually and quantitatively. We found that the flow of sLFO derived from RS fMRI does to a large extent represent the blood flow measured with DSC. The small differences, we hypothesize, are largely due to the difference between the methods in their sensitivity to different vessel types. We conclude that the flow of sLFO in RS visualized by our time delay method represents the blood flow in the capillaries and veins in the brain.

Optimization of two-compartment-exchange-model analysis for dynamic contrast-enhanced mri incorporating bolus arrival time.

To optimize the analysis of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) under the two-compartment-exchange-model (2CXM) and to incorporate voxelwise bolus-arrival-time (BAT). The accuracy of the pharmacokinetic (PK) parameters, extracted from 3T DCE-MRI using 2CXM, was tested under several conditions: eight algorithms for data estimation; correction for BAT; using model selection; different temporal resolution and scan duration. Comparisons were performed on simulated data. The best algorithm was applied to seven patients with brain tumors or following stroke. The extracted perfusion parameters were compared to those of dynamic susceptibility contrast MRI (DSC-MRI). ACoPeD (AIF-corrected-perfusion-DCE-MRI), an analysis using a 2nd derivative regularized-spline and incorporating BAT, achieved the most accurate estimation in simulated data, mean-relative-error: Fp , F, vp , ve : 24.8%, 41.7%, 26.4%, 27.2% vs. 76.5%, 190.8%, 78.8%, 82.39% of the direct four parameters estimation (one-sided two-sample t-test, P < 0.001). Correction for BAT increased the estimation accuracy of the PK parameters by more than 30% and provided a supertemporal resolution estimation of the BAT (higher than the acquired resolution, mean-absolute-error 0.2 sec). High temporal resolution (∼2 sec) is required to avoid biased estimation of PK parameters, and long scan duration (∼20 min) is important for reliable permeability but not for perfusion estimations, mean-error-reduction: E: ∼12%, ve : ∼6%. Using ACoPeD, PK values from normal-appearing white matter, gray matter, and lesion were extracted from patients. Preliminary results showed significant voxelwise correlations to DSC-MRI, between flow values in a patient following stroke (r = 0.49, P < 0.001), and blood volume in a patient with a brain tumor (r = 0.62, P < 0.001). This study proposes an optimized analysis method, ACoPeD, for tissue perfusion and permeability estimation using DCE-MRI, to be used in clinical settings. 1 J. Magn. Reson. Imaging 2017;45:237-249.

Noninvasively detecting Isocitrate dehydrogenase 1 gene status in astrocytoma by dynamic susceptibility contrast MRI.

To investigate the value of dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) in the noninvasive evaluation of isocitrate dehydrogenase (IDH) 1 gene status in astrocytoma. The preoperative DSC MRI data of 91 lesions with pathologically confirmed astrocytoma were retrospectively analyzed. MR examination was performed on a 3T MRI scanner. The normalized maximum ratios of relative cerebral blood volume (rCBV ratio) of tumor parenchyma were measured. The enrolled astrocytoma patients were divided into six groups according to the World Health Organization (WHO) classification method and IDH1 gene status. The differences in the rCBV ratio of tumor parenchyma between the IDH1 gene mutant and wildtype groups of WHO grade II, III, and IV were compared and plotted receiver operating characteristic (ROC) curves were drawn. The IDH1 gene mutant and wildtype groups of WHO grade II, III, and IV astrocytoma showed differences in the rCBV ratio (P = 0.005, 0.045, and 0.005, respectively). In WHO grade II, III, and IV astrocytoma, the area under the ROC curve was respectively 0.83, 0.86, and 0.94. The cutoff value of the rCBV ratio was respectively 2.20, 3.14, and 5.63. The rCBV ratio value provided by DSC MRI provides a new potential imaging method for the noninvasive evaluation of the IDH1 status in astrocytoma. 3 J. Magn. Reson. Imaging 2017;45:492-499.

A linear mixed perfusion model for tissue partial volume correction of perfusion estimates in dynamic susceptibility contrast MRI: Impact on absolute quantification, repeatability, and agreement with pseudo-continuous arterial spin labeling

The partial volume effect (PVE) is an important source of bias in brain perfusion measurements. The impact of tissue PVEs in perfusion measurements with dynamic susceptibility contrast MRI (DSC-MRI) has not yet been well established. The purpose of this study was to suggest a partial volume correction (PVC) approach for DSC-MRI and to study how PVC affects DSC-MRI perfusion results. A linear mixed perfusion model for DSC-MRI was derived and evaluated by way of simulations. Twenty healthy volunteers were scanned twice, including DSC-MRI, arterial spin labeling (ASL), and partial volume measurements. Two different algorithms for PVC were employed and assessed. Simulations showed that the derived model had a tendency to overestimate perfusion values in voxels with high fractions of cerebrospinal fluid. PVC reduced the tissue volume dependence of DSC-MRI perfusion values from 44.4% to 4.2% in gray matter and from 55.3% to 14.2% in white matter. One PVC method significantly improved the voxel-wise repeatability, but PVC did not improve the spatial agreement between DSC-MRI and ASL perfusion maps. Significant PVEs were found for DSC-MRI perfusion estimates, and PVC successfully reduced those effects. The findings suggest that PVC might be an important consideration for DSC-MRI applications. Magn Reson Med 77:2203-2214, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Dynamic susceptibility contrast and dynamic contrast-enhanced MRI characteristics to distinguish microcystic meningiomas from traditional Grade I meningiomas and high-grade gliomas

OBJECTIVE Microcystic meningioma (MM) is a meningioma variant with a multicystic appearance that may mimic intrinsic primary brain tumors and other nonmeningiomatous tumor types. Dynamic susceptibility contrast (DSC) and dynamic contrast-enhanced (DCE) MRI techniques provide imaging parameters that can differentiate these tumors according to hemodynamic and permeability characteristics with the potential to aid in preoperative identification of tumor type. METHODS The medical data of 18 patients with a histopathological diagnosis of MM were identified through a retrospective review of procedures performed between 2008 and 2012; DSC imaging data were available for 12 patients and DCE imaging data for 6. A subcohort of 12 patients with Grade I meningiomas (i.e., of meningoepithelial subtype) and 54 patients with Grade IV primary gliomas (i.e., astrocytomas) was also included, and all preoperative imaging sequences were analyzed. Clinical variables including patient sex, age, and surgical blood loss were also included in the analysis. Images were acquired at both 1.5 and 3.0 T. The DSC images were acquired at a temporal resolution of either 1500 msec (3.0 T) or 2000 msec (1.5 T). In all cases, parameters including normalized cerebral blood volume (CBV) and transfer coefficient (kTrans) were calculated with region-of-interest analysis of enhancing tumor volume. The normalized CBV and kTrans data from the patient groups were analyzed with 1-way ANOVA, and post hoc statistical comparisons among groups were conducted with the Bonferroni adjustment. RESULTS Preoperative DSC imaging indicated mean (± SD) normalized CBVs of 5.7 ± 2.2 ml for WHO Grade I meningiomas of the meningoepithelial subtype (n = 12), 4.8 ± 1.8 ml for Grade IV astrocytomas (n = 54), and 12.3 ± 3.8 ml for Grade I meningiomas of the MM subtype (n = 12). The normalized CBV measured within the enhancing portion of the tumor was significantly higher in the MM subtype than in typical meningiomas and Grade IV astrocytomas (p < 0.001 for both). Preoperative DCE imaging indicated mean kTrans values of 0.49 ± 0.20 min-1 in Grade I meningiomas of the meningoepithelial subtype (n = 12), 0.27 ± 0.12 min-1 for Grade IV astrocytomas (n = 54), and 1.35 ± 0.74 min-1 for Grade I meningiomas of the MM subtype (n = 6). The kTrans was significantly higher in the MM variants than in the corresponding nonmicrocystic Grade 1 meningiomas and Grade IV astrocytomas (p < 0.001 for both). Intraoperative blood loss tended to increase with increased normalized CBV (R = 0.45, p = 0.085). CONCLUSIONS An enhancing cystic lesion with a normalized CBV greater than 10.3 ml or a kTrans greater than 0.88 min-1 should prompt radiologists and surgeons to consider the diagnosis of MM rather than traditional Grade I meningioma or high-grade glioma in planning surgical care. Higher normalized CBVs tend to be associated with increased intraoperative blood loss.

Dynamic susceptibility contrast perfusion imaging in biopsy-proved adult medulloblastoma

Medulloblastoma (MB) is a high-grade rare brain tumor in adults, with heterogeneous imaging features and variable enhancing patterns. Diffusion and spectroscopy multimodal imaging have already been described in adult MB, yet perfusion has not been explored. This study aimed to evaluate vascularity in adult classic and desmoplastic MB, using perfusion-weighted dynamic susceptibility contrast (DSC) MRI and histopathology. Six histologically proved MB patients were classified as classic (n=3) and desmoplastic (n=3). DSC perfusion MRI was performed in three centers and retrospectively evaluated. Postprocessing included automatic arterial input function, motion and contrast leakage correction. Region of interest (ROI) delineation was performed on three perfusion slices to obtain a total of three cerebral blood volume ratios (rCBV) that were averaged to serve as the main rCBV. Permeability was evaluated on K2 maps. Low rCBVs were observed in all cases (mean rCBV=1.19±0.39). rCBV values were lower than 2 for classic MB and lower than 1 for desmoplastic MB. All cases showed an increase of permeability on K2 maps. Our preliminary results suggest that MB exhibits rCBV values close to 1 and increased permeability on DSC perfusion imaging, especially in desmoplastic cases, which could be explained by fibrous matrix. This type of perfusion pattern contrasts with those given by other enhancing subtentorial tumors such as metastasis, high-grade gliomas or hemangioblastomas.

SU‐G‐IeP1‐04: Comparison of Cerebral Blood Volume Estimated by DSC‐ and DCEMRI

Purpose:The cerebral blood volume (CBV) is commonly estimated from T2*/T2‐weighted dynamic susceptibility contrast (DSC) MRI acquired by an EPI sequence. There are several challenges with DSC imaging, including geometric distortion, limited brain spatial coverage, and unreliable arterial input function (AIF) due to the partial volume effect. However, CBV can be estimated from T1‐weighted dynamic contrast enhanced (DCE) MRI. This study aimed to examine whether CBV estimated from DCE‐MRI is comparable to one from DSC‐MRI. Methods and Materials: Of 16 patients with brain metastases, both DCE and DSC series were acquired on a 3T scanner. 3D T1‐weighted DCE images were acquired using a gradient‐echo (GRE) sequence, while 2D multi‐slice DSC (14–19 slices) were obtained using a GRE EPI sequence. CBV maps were generated from DCE images by the modified Toft model and from DSC images by a pharmacokinetic model with leakage correction. After image registration, CBV values estimated by the two methods were compared in two volumes of interest (VOIs) of normal appearing gray matter and white matter (NAGMWM) and in metastatic lesions at both voxel‐level and the VOI‐level.Results:In the two normal tissue VOIs, means (±std) of CBV were 2.04(±0.45)% and 1.86(±0.45)% from DCE imaging and 1.95(±0.46)% and 1.82(±0.44)% from DSC imaging, which were not significantly different in either VOIs. The voxel‐by‐voxel correlations within the two normal tissue VOIs led to averaged R=0.53 and 0.59 across 16 patients, suggesting high correlation between the two methods.Conclusion:The CBV estimated from DCE imaging was highly comparable to one from DSC imaging. The CBV estimated from DCE imaging is less affected by the susceptibility effect, and can cover the whole brain, which could be an alternative approach for the CBV estimation.This research work was supported by NIH grant: U01 CA183848

Phase 2 study of aldoxorubicin in relapsed glioblastoma.

2027Background: Glioblastoma (GBM) is the most common primary brain tumor with a median survival of ~14 months after initial therapy. Relapsed patients usually receive bevacizumab with an ORR of~20%, and OS of ~31 weeks. Recently Prakash et al demonstrated in an orthotopic mouse model of GBM that IV aldoxorubicin (A) but not doxorubicin (D) significantly delayed tumor growth and prolonged survival by over 100%. D does not pnetrate the blood-brain barrier. A is a prodrug of D that is attached to a pH sensitive linker that binds covalently to albumin and is released preferentially within tumors. We assessed the preliminary efficacy and safety of A administered to GBM patients who progressed after first line therapy. Methods: Patients > 18 yrs with 1st relapse GBM received either 250 mg/m2 (21) or 350 mg/m2(7) every 21 days until tumor progression, unacceptable toxicity or withdrawal. Tumors were assessed every 6 weeks by MRI and in some instances Dynamic Susceptibility Contrast (DSC) MRI. Safety monitoring ...

Advanced neuroimaging in the clinic: critical appraisal of the evidence base.

The shortage of high-quality systematic reviews in the field of radiology limits evidence-based integration of imaging methods into clinical practice and may perpetuate misconceptions regarding the efficacy and appropriateness of imaging techniques for specific applications. Diffusion tensor imaging for patients with mild traumatic brain injury (DTI-mTBI) and dynamic susceptibility contrast MRI for patients with glioma (DSC-glioma) are applications of quantitative neuroimaging, which similarly detect manifestations of disease where conventional neuroimaging techniques cannot. We performed a critical appraisal of reviews, based on the current evidence-based medicine methodology, addressing the ability of DTI-mTBI and DSC-glioma to (a) detect brain abnormalities and/or (b) predict clinical outcomes. 23 reviews of DTI-mTBI and 26 reviews of DSC-glioma met criteria for inclusion. All reviews addressed detection of brain abnormalities, whereas 12 DTI-mTBI reviews and 22 DSC-glioma reviews addressed prediction of a clinical outcome. All reviews were assessed using a critical appraisal worksheet consisting of 19 yes/no questions. Reviews were graded according to the total number of positive responses and the 2011 Oxford Centre for evidence-based medicine levels of evidence criteria. Reviews addressing DTI-mTBI detection had moderate quality, while those addressing DSC-glioma were of low quality. Reviews addressing prediction of outcomes for both applications were of low quality. Five DTI-mTBI reviews, but only one review of DSC-glioma met criteria for classification as a meta-analysis/systematic/quantitative review.

Prolonged Mean Transit Time Detected by Dynamic Susceptibility Contrast Magnetic Resonance Imaging Predicts Cerebrovascular Reserve Impairment in Patients with Moyamoya Disease

Background: Evaluating cerebrovascular reserve (CVR) is important for patients with moyamoya disease (MMD). ¹²³I-iodoamphetamine single-photon emission CT (SPECT) with acetazolamide (ACZ) challenge is widely carried out, but using ACZ becomes problematic owing to its off-label use and its adverse effects. Here, we report the efficacy of dynamic susceptibility contrast MRI (DSC-MRI) for the evaluation of CVR in MMD patients. Methods: All 33 MMD patients underwent both SPECT and DSC-MRI at an interval of <10 days from each other (mean age 38.3 years). The region of interest (ROI) was the anterior cerebral artery (ACA) territory, middle cerebral artery (MCA) territory, basal ganglia and cerebellum hemisphere for cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) images. The ratios of the ROIs to the ipsilateral cerebellum were calculated for each parameter and evaluated. The CVR was calculated using images acquired by SPECT before and after ACZ administration. The ratios of DSC-MRI parameters and CVR were compared and evaluated for each ROI. Results: The MTT of the ACA and MCA territories significantly correlated with CVR (p < 0.0001). However, CBF and CBV had no correlation with CVR. The MTT ratio had a threshold of 1.966, with a sensitivity of 68.4% and a specificity of 91.5% for predicting decreased CVR (<10%). Conclusion: MTT had a negative correlation with CVR. DSC-MRI is easy, safe and useful for detecting decreased CVR and can be used as a standard examination in MMD patient's care.

Measurement of arteriolar blood volume in brain tumors using MRI without exogenous contrast agent administration at 7T.

Arteriolar cerebral-blood-volume (CBVa) is an important perfusion parameter that can be measured using inflow-based vascular-space-occupancy (iVASO) MRI without exogenous contrast agent administration. The purpose of this study is to assess the potential diagnostic value of CBVa in brain tumor patients by comparing it with total-CBV (including arterial, capillary and venous vessels) measured by dynamic-susceptibility-contrast (DSC) MRI. Twelve brain tumor patients were scanned using iVASO (on 7T as part of a research project) and DSC (on 3T as part of routine clinical protocols) MRI. Region-of-interest analysis was performed to compare the resulting perfusion measures between tumoral and contralateral regions, and to evaluate their associations with tumor grades. CBVa measured by iVASO MRI significantly correlated with WHO grade (ρ = 0.37, P = 0.04). Total-CBV measured by DSC MRI showed a trend of correlation with WHO grade (ρ = 0.28, P = 0.5). The signal-to-noise ratio was comparable (P > 0.1) between the two methods, while the contrast-to-noise ratio between tumoral and contralateral regions was higher in iVASO-CBVa than DSC-CBV in WHO II/III patients (P < 0.05) but comparable in WHO IV patients (P > 0.1). A trend of positive correlation between DSC-CBV and iVASO-CBVa was observed (R2 = 0.28, P = 0.07). In this initial patient study, CBVa demonstrated a stronger correlation with WHO grade than total-CBV. Further investigation with a larger cohort is warranted to validate whether CBVa can be a better classifier than total-CBV for the stratification of brain tumors, and whether iVASO MRI can be a useful alternative method for the assessment of tumor perfusion, especially when exogenous contrast agent administration is difficult in certain patient populations. J. Magn. Reson. Imaging 2016;44:1244-1255.

Bidirectional Contrast agent leakage correction of dynamic susceptibility contrast (DSC)-MRI improves cerebral blood volume estimation and survival prediction in recurrent glioblastoma treated with bevacizumab.

To evaluate a leakage correction algorithm for T1 and T2* artifacts arising from contrast agent extravasation in dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) that accounts for bidirectional contrast agent flux and compare relative cerebral blood volume (CBV) estimates and overall survival (OS) stratification from this model to those made with the unidirectional and uncorrected models in patients with recurrent glioblastoma (GBM). We determined median rCBV within contrast-enhancing tumor before and after bevacizumab treatment in patients (75 scans on 1.5T, 19 scans on 3.0T) with recurrent GBM without leakage correction and with application of the unidirectional and bidirectional leakage correction algorithms to determine whether rCBV stratifies OS. Decreased post-bevacizumab rCBV from baseline using the bidirectional leakage correction algorithm significantly correlated with longer OS (Cox, P = 0.01), whereas rCBV change using the unidirectional model (P = 0.43) or the uncorrected rCBV values (P = 0.28) did not. Estimates of rCBV computed with the two leakage correction algorithms differed on average by 14.9%. Accounting for T1 and T2* leakage contamination in DSC-MRI using a two-compartment, bidirectional rather than unidirectional exchange model might improve post-bevacizumab survival stratification in patients with recurrent GBM. J. Magn. Reson. Imaging 2016;44:1229-1237.

Differentiation of Hemangioblastoma from Metastatic Brain Tumor using Dynamic Contrast-enhanced MR Imaging.

The aim of this study was to differentiate hemangioblastomas from metastatic brain tumors using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and compare the diagnostic performances with diffusion-weighted imaging (DWI) and dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). We retrospectively reviewed 7 patients with hemangioblastoma and 15 patients with metastatic adenocarcinoma with magnetic resonance imaging (MRI) including DWI, DSC-MRI, and DCE-MRI. Apparent diffusion coefficient (ADC), relative cerebral blood volume (rCBV), and DCE-MRI parameters (K trans, k ep, v e, and v p) were compared between the two groups. The diagnostic performance of each parameter was evaluated with receiver operating characteristic (ROC) curve analysis. v p, k ep, and rCBV were significantly different between patients with hemangioblastoma and those with metastatic brain tumor (p < 0.001, p = 0.005, and p = 0.017, respectively). A v p cutoff value of 0.012 and a rCBV cutoff value of 8.0 showed the highest accuracy for differentiating hemangioblastoma from metastasis. The area under the ROC curve for v p and rCBV was 0.99 and 0.89, respectively. A v p > 0.012 showed 100 % sensitivity, 93.3 % specificity, and 95.5 % accuracy and a rCBV > 8.0 showed 85.7 % sensitivity, 93.3 % specificity, and 90.9 % accuracy for differentiating hemangioblastoma from metastatic brain tumor. DCE-MRI was useful for differentiating hemangioblastoma from metastatic brain tumor.

Investigating tumor perfusion by hyperpolarized 13 C MRI with comparison to conventional gadolinium contrast-enhanced MRI and pathology in orthotopic human GBM xenografts.

Dissolution dynamic nuclear polarization (DNP) enables the acquisition of 13 C magnetic resonance data with a high sensitivity. Recently, metabolically inactive hyperpolarized 13 C-labeled compounds have shown to be potentially useful for perfusion imaging. The purpose of this study was to validate hyperpolarized perfusion imaging methods by comparing with conventional gadolinium (Gd)-based perfusion MRI techniques and pathology. Dynamic 13 C data using metabolically inactive hyperpolarized bis-1,1-(hydroxymethyl)-[1-13 C]cyclopropane-d8 (HMCP) were obtained from an orthotopic human glioblastoma (GBM) model for the characterization of tumor perfusion and compared with standard Gd-based dynamic susceptibility contrast (DSC) MRI data and immunohistochemical analysis from resected brains. Distinct HMCP perfusion characteristics were observed within the GBM tumors compared with contralateral normal brain tissue. The perfusion parameters obtained from the hyperpolarized HMCP data in tumor were strongly correlated with normalized peak height measured from the DSC images. The results from immunohistochemical analysis supported these findings by showing a high level of vascular staining for tumor that exhibited high levels of hyperpolarized HMCP signal. The results from this study have demonstrated that hyperpolarized HMCP data can be used as an indicator of tumor perfusion in an orthotopic xenograft model for GBM. Magn Reson Med 77:841-847, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Abstract WP43: Advanced White Matter Disease is Associated With Increased Blood-Brain Barrier Permeability and Early Diffuse Microstructural Changes in Patients With Acute Ischemic Stroke

Background: In acute ischemic stroke (AIS), cerebral tissue damage and clinical outcomes are linked to pre-existing microvascular dysfunction, manifesting as white matter hyperintensity (WMH). Elevated blood-brain barrier permeability (BBB-P) has been implicated in advanced WMH. We tested the microstructural integrity of BBB as measured by dynamic susceptibility contrast (DSC) MRI K 2 coefficient values in AIS patients with advanced WMH. Methods: Twenty patients enrolled in a prospective acute MRI study underwent diffusion tensor (DTI) and DSC MRI on admission for AIS. BBB-P estimates were derived from DSC MRI using the K 2 coefficients. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) maps were calculated. Mean K 2 , MD, AD, RD and FA values were measured in regions of WMH and normally appearing white matter (NAWM) in the hemisphere contralateral to AIS and compared (two-tailed Student t-Test). WMH volume (WMHv) was assessed on acute FLAIR using a validated semi-automated volumetric protocol. Linear regression was performed to evaluate significant predictors of K 2 , MD, AD, RD, and FA. Correlation analysis was performed (Pearson product-moment). Results: Mean age of subjects was 66 (±10) years, 30% were women, median WMHv 3.5cm 3 [IQR 1.6-7.4]. K 2 values differed significantly between WMH and NAWM (0.32 x10 -3 vs. 1.1 x10 -3 , p&lt;0.03), as did the diffusivity metrics for WMH and NAWM (FA: 0.25 vs 0.38; MD: 1.3 x10 -3 vs 0.84 x10 -3 ; AD: 1.6 x10 -3 vs 1.2 x10 -3 ; RD: 1.14 x10 -3 vs 0.66 x10 -3 ; all p&lt;0.0001). K 2 and RD values were correlated within WMH (R=-0.45, P=0.046) but not in NAWM (R=0.06, P=0.81). Multivariate analysis found systolic BP (SBP) and lnWMHv to be significant predictors of MD (P=0.0009), AD (P=0.002), and RD (P=0.002) in NAWM. Discussion: BBB-P and diffusivity values in patients with AIS and advanced leukoaraiosis differed significantly between WMH and NAWM in the hemisphere contralateral to acute infarct. Association between the RD and K 2 coefficients in WMH suggests the role of BBB-P in pathophysiology of WMH and the loss of microstructural white matter integrity associated with it. Further, the influence of SBP and lnWMHv on NAWM diffusivity values suggests ongoing risk for developing future WMH.

Correlation of 3D Arterial Spin Labeling and Multi-Parametric Dynamic Susceptibility Contrast Perfusion MRI in Brain Tumors.

Arterial spin labeling (ASL) is an alternative method to Dynamic susceptibility contrast (DSC) perfusion MRI for brain tumors. However, ASL cerebral blood flow (CBF) can be easily affected by transit time. DSC MRI derived time to maximum of the residue function (Tmax) is possible to assess the transit time on ASL. Thirty patients with brain tumors were studied using ASL and DSC MRI. The relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), Tmax, and mean transit time (MTT) were obtained from DSC MRI. The ratios of the parameters were analyzed. ASL CBF ratio correlated with the DSC rCBF ratio (r=0.78, p<0.001) and rCBV ratio (r=0.74, p<0.001). There was a moderate correlation between ASL CBF ratio and Tmax ratio (r=-0.43, p<0.05) in brain tumors. ASL CBF strongly correlated with DSC rCBF and rCBV. In addition, a negative correlation was found between ASL CBF and Tmax in brain tumors, indicating that these parameters would be affected by transit time. This may explain why ASL CBF is different from DSC rCBF and rCBV. The decreased DSC Tmax value may suggest high vascularity in a tumor. J. Med. Invest. 63: 175-181, August, 2016.

Perfusion magnetic resonance imaging provides additional information as compared to anatomical imaging for decision-making in vestibular schwannoma

ObjectiveThe added value of perfusion MRI for decision-making in vestibular schwannoma (VS) patients is unknown. MRI offers two perfusion methods: the first employing contrast agent (dynamic susceptibility contrast (DSC)-MRI) that provides information on cerebral blood volume (CBV) and cerebral blood flow (CBF), the second by magnetic labeling of blood (arterial spin labeling (ASL)-MRI), providing CBF-images. The goal of the current study is to investigate whether DSC and ASL perfusion MRI provides complimentary information to current anatomical imaging in treatment selection process of VS. MethodsNine patients with growing VS with extrameatal diameter >9mm were included (>2mm/year and 20% volume expansion/year) and one patient with 23mm extrameatal VS without growth. DSC and ASL perfusion MRI were obtained on 3T MRI. Perfusion in VS was scored as hyperintense, hypointense or isointense compared to the contralateral region. ResultsSeven patients showed hyperintense signal on DSC and ASL sequences. Three patients showed iso- or hypointense signal on at least one perfusion map (1 patient hypointense on both DSC-MRI and ASL; 1 patient isointense on DSC-CBF; 1 patient isointense on ASL). All patients showed enhancement on post-contrast T1 anatomical scan. ConclusionPerfusion MR provides additional information compared to anatomical imaging for decision-making in VS.

Automated Determination of Arterial Input Function for Dynamic Susceptibility Contrast MRI from Regions around Arteries Using Independent Component Analysis

Purpose. Quantitative cerebral blood flow (CBF) measurement using dynamic susceptibility contrast- (DSC-) MRI requires accurate estimation of the arterial input function (AIF). The present work utilized the independent component analysis (ICA) method to determine the AIF in the regions adjacent to the middle cerebral artery (MCA) by the alleviated confounding of partial volume effect. Materials and Methods. A series of spin-echo EPI MR scans were performed in 10 normal subjects. All subjects received 0.2 mmol/kg Gd-DTPA contrast agent. AIFs were calculated by two methods: (1) the region of interest (ROI) selected manually and (2) weighted average of each component selected by ICA (weighted-ICA). The singular value decomposition (SVD) method was then employed to deconvolve the AIF from the tissue concentration time curve to obtain quantitative CBF values. Results. The CBF values calculated by the weighted-ICA method were 41.1 ± 4.9 and 22.1 ± 2.3 mL/100 g/min for cortical gray matter (GM) and deep white matter (WM) regions, respectively. The CBF values obtained based on the manual ROIs were 53.6 ± 12.0 and 27.9 ± 5.9 mL/100 g/min for the same two regions, respectively. Conclusion. The weighted-ICA method allowed semiautomatic and straightforward extraction of the ROI adjacent to MCA. Through eliminating the partial volume effect to minimum, the CBF thus determined may reflect more accurate physical characteristics of the T2⁎ signal changes induced by the contrast agent.

Predicting and optimizing the territory of blood–brain barrier opening by superselective intra-arterial cerebral infusion under dynamic susceptibility contrast MRI guidance

Interventional neuroradiology techniques are minimally invasive and allow for superselective drug delivery to specific brain regions. The passage of most agents, however, is impaired by the blood–brain barrier (BBB). Despite its discovery over 40 years ago, hyperosmotic BBB opening (BBBO) remains highly variable, preventing its widespread implementation. Here, we report on a technique that enables the prediction and optimization of the BBBO territory. We found that the microcatheter tip position and the speed of hyperosmolar mannitol injection, both major determinants of the targeted territory, can be modulated in real-time as guided by trans-catheter perfusion MRI.