Magnetic resonance perfusion imaging findings following flow diversion in patients with complex middle cerebral artery bifurcation aneurysms: a single-center analysis regarding the jailed cortical branches

BACKGROUND

Flow diverter (FD) devices provide a safe and effective treatment option especially for wide-necked intracranial aneurysms. One of the main concerns in patients treated with FD devices is patency of arterial branches jailed by the stent. However, there are no long-term data from magnetic resonance perfusion (MRP) studies regarding jailed branches. In this study we aimed to reveal the MRP findings in patients with jailed middle cerebral artery (MCA) cortical branches during long-term follow-up after flow diversion.

METHODS

Patients who underwent FD stent treatment for MCA aneurysms with a resulting jailed cortical branch were included. Follow-up clinical, angiographic, and MRP examination findings were recorded. Different MRP parameters were measured in the MCA territory regarding the jailed branches.

RESULTS

Eighteen patients treated endovascularly with flow diversion for a total of 20 MCA aneurysms were included. At angiographic follow-up (median 35 months, range 7-95 months) complete occlusion was observed in 13 (65%) aneurysms and partial occlusion was observed in 6 (30%). The mean transit time (MTT) prolongation, MTT ratio, time-to peak (TTP) prolongation, and TTP ratio were 1.34, 1.20, 1.18, and 1.06 s, respectively, when compared with the contralateral side in the MCA territory. MTT, TTP, and cerebral blood volume values of the patients showed statistically significant differences compared with the contralateral side (P<0.05).

CONCLUSIONS

Flow diversion treatment of complex bifurcation aneurysms can be effective and safe. MRP examination may reveal perfusion changes in the territory vascularized via a jailed branch, and these changes are rarely accompanied by clinical findings.

Magnetic resonance imaging-derived relative cerebral blood volume characteristics in a case of pathologically confirmed neurocysticercosis: illustrative case

BACKGROUND

Neurocysticercosis (NCC) is a parasitic infection of the brain caused by ingesting water or food contaminated with tapeworm eggs. When it presents as a solitary mass, differentiation from a primary brain tumor on imaging can be difficult. Magnetic resonance imaging (MRI)-derived relative cerebral blood volume (rCBV) is a newer imaging technique used to identify areas of neovascularization in tumors, which may advance the differential diagnosis.

OBSERVATIONS

A 25-year-old male presented after a seizure. Computed tomography (CT) and MRI demonstrated a partially enhancing lesion with microcalcifications and vasogenic edema. Follow-up rCBV assessment demonstrated mild hyperperfusion and/or small vessels at the lesional margins consistent with either an intermediate grade glioma or infection. Given the radiological equipoise, surgical accessibility, and differential diagnosis including primary neoplasm, metastatic disease, NCC, and abscess, resection was pursued. The calcified mass was excised en bloc and was confirmed as larval-stage NCC.

LESSONS

CT or MRI may not always provide sufficient information to distinguish NCC from brain tumors. Although reports have suggested that rCBV may aid in identifying NCC, here the authors describe a case of pathologically confirmed NCC in which preoperative, qualitative, standardized rCBV findings raised concern for a primary neoplasm. This case documents the first standardized rCBV values reported in a pathologically confirmed case of NCC in the United States.

Intravoxel incoherent motion for differentiating residual/recurrent tumor from post-treatment change in patients with high-grade glioma

PURPOSE

To investigate the diagnostic value of f derived from IVIM technique and to correlate it with rCBV derived from DSC for the differentiation of residual/recurrent tumor from post-treatment change in patients with high-grade glioma.

MATERIALS AND METHODS

Patients who underwent MR imaging with IVIM and DSC studies for evaluation of high-grade glioma after standard treatment were enrolled in this retrospective study. For qualitative analysis, the f and rCBV maps were interpreted as hypoperfused or hyperperfused in each parameter. Quantitative analysis was performed using ROI analysis in f and rCBV parameters. The lesions were divided into residual/recurrent tumor and post-treatment change groups.

RESULTS

Nineteen patients with high-grade glioma were included. In qualitative analysis, the f-map shows higher sensitivity (100.0%) than rCBV map (92.3%), while the rCBV map shows higher specificity (100.0%) than the f-map (83.3%). In quantitative analysis, the optimal cutoff values of 1.19 for f and 1.06 for rCBV are shown to provide high diagnostic value with high sensitivity (91.7%) for both parameters but slightly higher specificity of rCBV (85.7%) than f (71.4%). The correlation between f and rCBV was good with ICC of 0.810.

CONCLUSION

The f value measured by IVIM technique, non-contrast perfusion technique, has high diagnostic performance and potential to be an alternative method to CBV measured by DSC for differentiation between residual/recurrent tumor and post-treatment change in patients with high-grade glioma.

Association between intraprocedural drops in blood pressure and infarct growth rate patterns after acute large-vessel occlusions

BACKGROUND

Infarct growth rate (IGR) differs among patients with acute ischemic stroke due to large vessel occlusion (LVO-AIS), and this variability has critical clinical repercussions. We explored IGR patterns and their association with blood pressure during endovascular therapy (EVT).

METHODS

This is a two-center cohort observational study that included consecutive anterior circulation LVO-AIS patients who underwent EVT and achieved modified Thrombolysis in Cerebral Infarction (mTICI) 2 c-3. Initial and final infarct volumes (FIV) were defined using admission computed tomography perfusion (CTP) defined as relative cerebral blood flow (rCBF) <30%, and diffusion-weighted imaging-magnetic resonance imaging (DWI-MRI) at 24 hours post-EVT. We categorized IGR patterns as exponential (ExpIGR) and Non-exponential (NonExp) based on their growth curves. We then dichotomized ExpIGR clinical significance based on the association of infarct growth with 90-day Modified Rankin Score (mRS) as ExpIGR-A (>13 mL) and ExpIGR-B (<13 mL). Intraprocedural blood pressure (BP) drops were calculated as the difference between median arterial pressure (MAP) at admission and the lowest intraprocedural MAP reading before recanalization, and the area between admission MAP threshold and all lower measurements of intraprocedural MAP. Logistic and linear regression were used to investigate associations between variables of interest.

RESULTS

Of 159 modified Thrombolysis in Cerebral Infarction (mTICI) 2 c-3 patients, we found that 36% demonstrated ExpIGR-A, 31% ExpIGR-B, and 32.7% NonExp patterns. The Exp-A and Exp-B groups differed significantly in National Institutes of Health Stroke Scale (NIHSS) score, Alberta Stroke Program Early CT Score (ASPECTS), glucose, and FIV. The Exp-A and NonExp groups differed in rCBF <30% vol, and time of stroke onset (SO) to admission CTP; and the Exp-B and NonExp groups in NIHSS, rCBF <30%, Tmax <6 s volume, collateral flow measured by hypoperfusion intensity ratio (HIR), and FIV. Hypotensive MAP area (HMA) was independently associated with an ExpIGR-A pattern. Infarct volume increased by 1 mL per 100 units of hypotensive area and 4.2 mL per 0.1 units of HIR, with a significant interaction between both variables.

CONCLUSION

After an LVO-AIS, the IGR can be differentiated into two distinct exponential and non-exponential patterns. A subgroup of patients with the exponential pattern experienced clinically meaningful infarct growth rates between CTP acquisition and reperfusion and seem to be highly vulnerable to episodes of sustained intraprocedural BP drops during EVT.

Clinically important effect sizes for clinical trials using infarct growth reduction as the primary outcome: a systematic review

BACKGROUND

Infarct growth on multimodal imaging is a common lead outcome in phase 2 proof-of-concept and dose-optimization neuroprotective agent stroke trials. However, the effect size in infarct growth reduction that correlates with clinically meaningful differences in clinical global disability outcomes has not been well delineated.

METHODS

A systematic literature search identified all endovascular thrombectomy randomized trials reporting magnitude of treatment effect on both infarct growth reduction and increase in functional independence (modified Rankin Scale (mRS) 0-2). Data aggregation determined the size of infarct growth reductions salient to four types of clinically meaningful effect sizes of increase in functional independence: (1) the minimal clinically important difference (MCID)-outcome specific; (2) the MCID-practice changing; (3) the realistic target difference; and (4) the reasonable comparability effect size.

RESULTS

A systematic search identified four trials enrolling 612 imaged participants. Across the trials, the amount of functional independence (mRS 0-2) increase associated with each 1 mL reduction in infarct growth was mean 2.3±0.6%. An infarct growth reduction of 0.57 mL correlated with the mRS 0-2 increase MCID of 1.3%. Infarct growth reductions of 2.27 mL, 4.35 mL, and 6.53 mL correlated with realistic effect and reasonable comparability effects sizes of mRS 0-2 increases of 5%, 10%, and 15%, respectively.

CONCLUSION

In formal meta-analysis of randomized treatment trials, every 1 mL reduction in infarct growth was associated with a 2.3% increase in functional independence (mRS 0-2) at 3 months. This conversion factor can inform selection of infarct growth effect size targets for phase 2 trials of neuroprotective agents.

Conventional and advanced MR imaging findings of primary Ewing sarcoma of the tentorium: a case report with literature review

BACKGROUND

Primary intracranial Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) is an extremely uncommon tumor. Care should be taken as it can be mistaken for a meningioma radiologically.

CASE DESCRIPTION

This paper reports a case of a 44-year-old male presenting with headache. A magnetic resonance imaging demonstrated a mass involving the tentorium, cerebrum and cerebellum with solid-cystic component. The solid component was hyperintense on T1-weighted images with significant enhancement. There was restriction in diffusion-weighted images and microhemorrhagic signal change in susceptibility weighted images. MR perfusion revealed increased relative cerebral blood volume and mean transit time values. Surgical pathology was reported as ES.

CONCLUSIONS

Intracranial ES/pPNET is a rare tumor that generally arises from the meninges. It must be distinguished from meningioma since it can be mistaken radiologically, because the treatment and prognosis are quite different. Localization and conventional MR signal characteristics of both lesions are similar. Whereas, MR perfusion findings may be helpful in discrimination.

Persistent perfusion abnormalities at day 1 correspond to different clinical trajectories after stroke

BACKGROUND

Perfusion abnormalities after thrombolysis are frequent within and surrounding ischemic lesions, but their relative frequency is not well known.

OBJECTIVE

To describe the different patterns of perfusion abnormalities observed at 24 hours and compare the characteristics of the patients according to their perfusion pattern.

METHODS

From our thrombolysis registry, we included 226 consecutive patients with an available arterial spin labeling (ASL) perfusion sequence at day 1. We performed a blinded assessment of the perfusion status (hypoperfusion-h, hyperperfusion-H, or normal-N) in the ischemic lesion and in the surrounding tissue. We compared the time course of clinical recovery, the rate of arterial recanalization, and hemorrhagic transformations in the different perfusion profiles.

RESULTS

We identified seven different perfusion profiles at day 1. Four of these (h/h, h/H, H/H, and H/N) represented the majority of the population (84.1%). The H/H profile was the most frequent (34.5%) and associated with 3-month good outcome (modified Rankin Scale (mRS): 63.5%). Patients with persistent hypoperfusion within and outside the lesion (h/h, 12.4%) exhibited worse outcomes after treatment (mRS score 0-2: 23.8%) than other patients, were less frequently recanalized (40.7%), and had more parenchymal hematoma (17.8%). The h/H profile had an intermediate clinical trajectory between the h/h profile and the hyperperfused profiles.

CONCLUSION

ASL hypoperfusion within the infarct and the surrounding tissue was associated with poor outcome. A more comprehensive view of the mechanisms in the hypoperfused surrounding tissue could help to design new therapeutic approaches during and after reperfusion therapies.

Are there reliable multiparametric MRI criteria for differential diagnosis between intracranial meningiomas and solitary intracranial dural metastases?

Intracranial meningiomas are the most common tumors of the central nervous system (CNS). Meningiomas account for up to 36% of all brain tumors. The incidence of metastatic brain lesions has not been determined. Up to 30% of adult patients with cancer of one localization or another suffer from a secondary tumor lesion of the brain. The vast majority of meningiomas have meningeal localization; >90% are solitary. The incidence of intracranial dural metastases (IDM) is 8-9% of cases, while in 10% of cases, the brain is the only localization, and in 50% of cases the metastases are solitary. Typically, the task of distinguishing between meningioma and dural metastasis does not involve difficulties. Periodically, there is a situation when the differential diagnosis between these tumors is ambiguous, since meningiomas and solitary IDM may have similar characteristics, in particular, a cavity-less solid structure, limited diffusion of water molecules, the presence of extensive peritumoral edema, and an identical contrast pattern. The present study included 100 patients with newly diagnosed tumors of the CNS, who subsequently underwent examination and neurosurgical treatment at the Federal Center for Neurosurgery with histological verification between May 2019 and October 2022. Depending on the histological conclusion, two study groups of patients were distinguished: The first group consisted of patients diagnosed with intracranial meningiomas (n=50) and the second group of patients were diagnosed with IDM (n=50). The study was performed using a magnetic resonance imaging (MRI) General Electric Discovery W750 3T before and after contrast enhancement. The diagnostic value of this study was estimated using Receiver Operating Characteristic curve and area under the curve analysis. Based on the results of the study, it was found that the use of multiparametric MRI (mpMRI) in the differential diagnosis of intracranial meningiomas and IDM was limited by the similarity of the values of the measured diffusion coefficient. The assumption, previously put forward in the literature, regarding the presence of a statistically significant difference in the apparent diffusion coefficient values, which make it possible to differentiate tumors, was not confirmed. When analyzing perfusion data, IDM showed higher cerebral blood flow (CBF) values compared with intracranial meningiomas (P≤0.001). A threshold value of the CBF index was revealed, which was 217.9 ml/100 g/min, above which it is possible to predict IDM with a sensitivity and specificity of 80.0 and 86.0%, respectively. Diffusion-weighted images are not reliable criteria for differentiating intracranial meningiomas from IDM and should not influence the diagnosis suggested by imaging. The technique for assessing the perfusion of a meningeal lesion makes it possible to predict metastases with a sensitivity and specificity close to 80-90% and deserves attention when making a diagnosis. In the future, in order to reduce the number of false negative and false positive results, mpMRI would require additional criteria to be included in the protocol. Since IDM differs from intracranial meningiomas in the severity of neoangiogenesis and, accordingly, in greater vascular permeability, the technique for assessing vascular permeability (wash-in parameter with dynamic contrast enhancement) may serve as a refining criterion for distinguishing between dural lesions.

[The importance of MR imaging in the diagnosis and management of acute stroke]

Background and purpose

In our collaborative project, called MRI First!, every patient arriving with neurological symptoms of acute stroke and without contraindications was examined by MRI. Our aim was to detect the symptomatic lesions, to obtain appropriate information about the brain parenchyma and to analyse parenchymal perfusion and brain vasculature.

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Methods

The examinations were conduc­ted on a Philips Ingenia 1.5 Tesla scanner with the following protocol: DWI-ADC, FLAIR, T2 FFE/SWI, PWI, and contrast-enhanced MRA. 415 patients were examined between January 2020 and May 2021. 179 patients arrived within-, and 136 patients after 4.5 hours symptoms onset time, while 100 patients had “wake-up” stroke.

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Results

Within the 4.5 hours group, 81 cases had acute ischemic lesion, 48 of them received reperfusion therapy. Acute ische­mic lesion was found in 64 patients in the wake-up stroke group and in 64 in the 4.5-24 hours group. In these groups 10 and 12 patients obtained reperfusion therapy, respectively. Further 117 cases were considered as stroke mimics, in which cases unnecessary intravenous thrombolysis was avoidable.

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Conclusion

MRI is accepted as a sensitive diagnostic modality providing detailed information regarding the brain parenchyma, its perfusion and vasculature. Nonetheless, its worldwide utilization in acute stroke is low and further information should be collected on which patient groups would gain the most benefit from acute MR imaging. Our continuous work is aimed at that goal.

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Imaging Cancer in Neuroradiology

Neuroimaging plays a pivotal role in the diagnosis, management, and prognostication of brain tumors. Recently, the World Health Organization published the fifth edition of the WHO Classification of Tumors of the Central Nervous System (CNS5), which places greater emphasis on tumor genetics and molecular markers to complement the existing histological and immunohistochemical approaches. Recent advances in computational power allowed modern neuro-oncological imaging to move from a strictly morphology-based discipline to advanced neuroimaging techniques with quantifiable tissue characteristics such as tumor cellularity, microstructural organization, hemodynamic, functional, and metabolic features, providing more precise tumor diagnosis and management. The aim of this review is to highlight the key imaging features of the recently published CNS5, outlining the current imaging standards and summarizing the latest advances in neuro-oncological imaging techniques and their role in complementing traditional brain tumor imaging and management.

Assessment of three MR perfusion software packages in predicting final infarct volume after mechanical thrombectomy

AIMS

To evaluate the performance of three MR perfusion software packages (A: RAPID; B: OleaSphere; and C: Philips) in predicting final infarct volume (FIV).

METHODS

This cohort study included patients treated with mechanical thrombectomy following an admission MRI and undergoing a follow-up MRI. Admission MRIs were post-processed by three packages to quantify ischemic core and perfusion deficit volume (PDV). Automatic package outputs (uncorrected volumes) were collected and corrected by an expert. Successful revascularization was defined as a modified Thrombolysis in Cerebral Infarction (mTICI) score ≥2B. Uncorrected and corrected volumes were compared between each package and with FIV according to mTICI score.

RESULTS

Ninety-four patients were included, of whom 67 (71.28%) had a mTICI score ≥2B. In patients with successful revascularization, ischemic core volumes did not differ significantly from FIV regardless of the package used for uncorrected and corrected volumes (p>0.15). Conversely, assessment of PDV showed significant differences for uncorrected volumes. In patients with unsuccessful revascularization, the uncorrected PDV of packages A (median absolute difference -40.9 mL) and B (median absolute difference -67.0 mL) overestimated FIV to a lesser degree than package C (median absolute difference -118.7 mL; p=0.03 and p=0.12, respectively). After correction, PDV did not differ significantly from FIV for all three packages (p≥0.99).

CONCLUSIONS

Automated MRI perfusion software packages estimate FIV with high variability in measurement despite using the same dataset. This highlights the need for routine expert evaluation and correction of automated package output data for appropriate patient management.

Association of fluid-attenuated inversion recovery vascular hyperintensity with ischaemic events in internal carotid artery or middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Individuals with intracranial artery occlusion have high rates of ischaemic events and recurrence. It has been challenging to identify patients who had high-risk stroke using a simple, valid and non-invasive screening approach. This study aimed to investigate whether fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH), a specific imaging sign on the FLAIR sequence, could be a predictor of ischaemic events in a population with internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion.

METHODS

We retrospectively analysed 147 patients (mean 60.43±12.83 years) with 149 lesions, including 37 asymptomatic and 112 symptomatic cases of ICA or MCA occlusion. Symptomatic occlusion was considered if ischaemic events were present in the relevant territory within 90 days. FVH Alberta Stroke Program Early Computed Tomography Score (FVH-ASPECTS: 0-7, with 0 indicating absence of FVH and 7 suggesting prominent FVH) and collateral circulation grade were assessed for each participant. Multivariable logistic regression analysis was performed to detect independent markers associated with symptomatic status.

RESULTS

A lower FVH-ASPECTS was associated with a more favourable collateral circulation grade (rho=-0.464, p<0.0001). The FVH-ASPECTS was significantly lower in the asymptomatic occlusion group than in the symptomatic occlusion group (p<0.0001). FVH-ASPECTS (Odd ratio, 2.973; 95% confidence interval, 1.849 to 4.781; p<0.0001) was independently associated with symptomatic status after adjustment for age, sex, lesion location and collateral circulation grade in the multivariate logistic regression. The area under the curve was 0.861 for the use of FVH-ASPECTS to identify symptomatic occlusion.

CONCLUSIONS

The ability to discriminate symptomatic from asymptomatic occlusion suggests that FVH may be a predictor of stroke. As a simple imaging sign, FVH may serve as a surrogate for haemodynamic impairments and can be used to identify high-risk stroke cases early in ICA or MCA occlusion.

The value of arterial spin labelling (ASL) perfusion MRI in the assessment of post-treatment progression in adult glioma: A systematic review and meta-analysis

Background

The distinction between viable tumor and therapy-induced changes is crucial for the clinical management of patients with gliomas. This study aims to quantitatively assess the efficacy of arterial spin labeling (ASL) biomarkers, including relative cerebral blood flow (rCBF) and absolute cerebral blood flow (CBF), for the discrimination of progressive disease (PD) and treatment-related effects.

Methods

Eight articles were included in the synthesis after searching the literature systematically. Data have been extracted and a meta-analysis using the random-effect model was subsequently carried out. Diagnostic accuracy assessment was also performed.

Results

This study revealed that there is a significant difference in perfusion measurements between groups with PD and therapy-induced changes. The rCBF yielded a standardized mean difference (SMD) of 1.25 [95% CI 0.75, 1.75] (p < .00001). The maximum perfusion indices (rCBFmax and CBFmax) both showed equivalent discriminatory ability, with SMD of 1.35 [95% CI 0.78, 1.91] (p < .00001) and 1.56 [95% CI 0.79, 2.33] (p < .0001), respectively. Similarly, accuracy estimates were comparable among ASL-derived metrices. Pooled sensitivities [95% CI] were 0.85 [0.67, 0.94], 0.88 [0.71, 0.96], and 0.93 [0.73, 0.98], and pooled specificities [95% CI] were 0.83 [0.71, 0.91], 0.83 [0.67, 0.92], 0.84 [0.67, 0.93], for rCBF, rCBFmax and CBFmax, respectively. Corresponding HSROC area under curve (AUC) [95% CI] were 0.90 [0.87, 0.92], 0.92 [0.89, 0.94], and 0.93 [0.90, 0.95].

Conclusion

These results suggest that ASL quantitative biomarkers, particularly rCBFmax and CBFmax, have the potential to discriminate between glioma progression and therapy-induced changes.

Perfusion and permeability as diagnostic biomarkers of cavernous angioma with symptomatic hemorrhage

Cavernous angiomas with symptomatic hemorrhage (CASH) have a high risk of rebleeding, and hence an accurate diagnosis is needed. With blood flow and vascular leak as established mechanisms, we analyzed perfusion and permeability derivations of dynamic contrast-enhanced quantitative perfusion (DCEQP) MRI in 745 lesions of 205 consecutive patients. Thirteen respective derivations of lesional perfusion and permeability were compared between lesions that bled within a year prior to imaging (N = 86), versus non-CASH (N = 659) using machine learning and univariate analyses. Based on logistic regression and minimizing the Bayesian information criterion (BIC), the best diagnostic biomarker of CASH within the prior year included brainstem lesion location, sporadic genotype, perfusion skewness, and high-perfusion cluster area (BIC = 414.9, sensitivity = 74%, specificity = 87%). Adding a diagnostic plasma protein biomarker enhanced sensitivity to 100% and specificity to 85%. A slightly modified derivation achieved similar accuracy (BIC = 321.6, sensitivity = 80%, specificity = 82%) in the cohort where CASH occurred 3-12 months prior to imaging after signs of hemorrhage would have disappeared on conventional MRI sequences. Adding the same plasma biomarker enhanced sensitivity to 100% and specificity to 87%. Lesional blood flow on DCEQP may distinguish CASH after hemorrhagic signs on conventional MRI have disappeared and are enhanced in combination with a plasma biomarker.

Contrast Pediatric Brain Perfusion: Dynamic Susceptibility Contrast and Dynamic Contrast-Enhanced MR Imaging

Magnetic resonance (MR) perfusion is a robust imaging technique that assesses the passage of blood through the cerebral vascular network using a variety of techniques. The applications of MR perfusion have been expanded and is well suited to investigate cerebrovascular diseases and cerebral neoplastic processes in pediatric patients. Assessment of brain perfusion can augment the information obtained on conventional MR imaging and provides additional information on the biological and physiologic features of pediatric brain tumors. Similarly, MR perfusion can help guide the management of a variety of pediatric cerebrovascular diseases, including acute ischemic stroke and Moyamoya syndrome.

Advanced Neuroimaging Preceding Intravenous Thrombolysis in Acute Ischemic Stroke Patients Is Safe and Effective

Advanced neuroimaging is one of the most important means that we have in the attempt to overcome time constraints and expand the use of intravenous thrombolysis (IVT). We assessed whether, and how, the prior use of advanced neuroimaging (AN), and more specifically CT/MR perfusion post-processed with RAPID software, regardless of time from symptoms onset, affected the outcomes of acute ischemic stroke (AIS) patients who received IVT. Methods. We retrospectively evaluated consecutive AIS patients who received intravenous thrombolysis monotherapy (without endovascular reperfusion) during a six-year period. The study population was divided into two groups according to the neuroimaging protocol used prior to IVT administration in AIS patients (AN+ vs. AN-). Safety outcomes included any intracranial hemorrhage (ICH) and 3-month mortality. Effectiveness outcomes included door-to-needle time, neurological status (NIHSS-score) on discharge, and functional status at three months assessed by the modified Rankin Scale (mRS). Results. The rate of IVT monotherapy increased from ten patients per year (n = 29) in the AN- to fifteen patients per year (n = 47) in the AN+ group. Although the onset-to-treatment time was longer in the AN+ cohort, the two groups did not differ in door-to-needle time, discharge NIHSS-score, symptomatic ICH, any ICH, 3-month favorable functional outcome (mRS-scores of 0-1), 3-month functional independence (mRS-scores of 0-2), distribution of 3-month mRS-scores, or 3-month mortality. Conclusion. Our pilot observational study showed that the incorporation of advanced neuroimaging in the acute stroke chain pathway in AIS patients increases the yield of IVT administration without affecting the effectiveness and safety of the treatment.

Assessment of Blood-Brain Barrier Integrity in Tuberculous Meningitis Using Dynamic Contrast-Enhanced MR Perfusion

Objective Tuberculous meningitis (TBM) is the most common form of central nervous system tuberculosis. The aim of the study was to quantitatively evaluate blood-brain barrier (BBB) perfusion changes in TBM patients using dynamic contrast-enhanced (DCE) MR perfusion. Methods and Material Thirty untreated patients of TBM and 10 healthy controls were prospectively evaluated by conventional imaging and DCE MR perfusion. Mean permeability indices- K trans and Ve-were calculated from multiple regions of interest (ROIs) placed in basal cisterns and comparison was done between the patients and controls. Results The permeability indices were significantly higher (where p < 0.001) in cisterns of TBM patients who showed basal meningeal enhancement when compared with healthy controls. Significant differences in permeability were observed between "enhancing" cases and controls as well as in "enhancing" cases when compared with the "non-enhancing" cases. However, no significant difference was observed in the mean cisternal value between "non-enhancing" cases and the controls. K trans with a cutoff value of > 0.0838 had 81.6% sensitivity and 78.6% specificity in differentiating cases and controls while V e mean value with a cutoff value of 0.0703 showed 86.8% sensitivity and 91.4% specificity in predicting the permeability difference between the cases and controls. Conclusion DCE MR perfusion is useful in the quantitative measurement of disruption of BBB and perfusion alterations in patients of TBM.

Acute Ischemic Stroke: MR Imaging-Based Paradigms

Multimodal MR imaging provides valuable information in the management of patients with acute ischemic stroke (AIS), with diagnostic, therapeutic, and prognostic implications. MR imaging plays a critical role in treatment decision making for (1) thrombolytic treatment of AIS patients with unknown symptom-onset and (2) endovascular treatment of patients with large vessel occlusion presenting beyond 6 hours from the symptom onset. MR imaging provides the most accurate information for detection of ischemic brain and is invaluable for differentiating AIS from stroke mimics.

Perfusion-weighted MRI in cerebral amyloid angiopathy-related transient focal neurological episodes

INTRODUCTION

Sporadic cerebral amyloid angiopathy (CAA) is a common age-related cerebral small vessel disease characterized by progressive ß-amyloid deposition in the walls of small cortical arteries, arterioles, and capillaries in the cerebral cortex and overlying leptomeninges. CAA-related transient focal neurological episodes (CAA-TFNEs) represent a challenging clinical feature interesting from a pathophysiological point of view.

CASE REPORT

Here we present two cases of CAA-TFNEs in which we performed functional imaging with perfusion-weighted imaging MR and brain 18 F-FDG PET. In both cases, we found a topographic relationship between the involved cortical areas and the clinical expression of CAA-TFNEs. Cortical superficial siderosis in the first case and a convexity subarachnoid hemorrhage in the second case were found in the contralateral rolandic area corresponding to the clinical symptoms. The same areas showed a reduction of rCBV and rCBF on perfusion-weighted MR and were also associated in one case with hypometabolism on 18 F-FDG PET.

DISCUSSION

These new findings strengthen the hypothesis that CAA involves the superficial leptomeningeal arteries but also the short penetrating arterioles reaching different depths in the cortex generating hypoperfusion and altered vascular reactivity and consequently reduced neuronal activity.

CONCLUSION

Understanding CAA-TFNEs is pivotal because they carry a very high risk of subsequent lobar intracerebral hemorrhage but are frequently misdiagnosed as TIAs and treated with antithrombotics enhancing the bleeding risk associated with CAA.

Multiparametric MRI for early identification of therapeutic response in recurrent glioblastoma treated with immune checkpoint inhibitors

BACKGROUND

Physiologic changes quantified by diffusion and perfusion MRI have shown utility in predicting treatment response in glioblastoma (GBM) patients treated with cytotoxic therapies. We aimed to investigate whether quantitative changes in diffusion and perfusion after treatment by immune checkpoint inhibitors (ICIs) would determine 6-month progression-free survival (PFS6) in patients with recurrent GBM.

METHODS

Inclusion criteria for this retrospective study were: (i) diagnosis of recurrent GBM treated with ICIs and (ii) availability of diffusion and perfusion in pre and post ICI MRI (iii) at ≥6 months follow-up from treatment. After co-registration, mean values of the relative apparent diffusion coefficient (rADC), Ktrans (volume transfer constant), Ve (extravascular extracellular space volume) and Vp (plasma volume), and relative cerebral blood volume (rCBV) were calculated from a volume-of-interest of the enhancing tumor. Final assignment of stable/improved versus progressive disease was determined on 6-month follow-up using modified Response Assessment in Neuro-Oncology criteria.

RESULTS

Out of 19 patients who met inclusion criteria and follow-up (mean ± SD: 7.8 ± 1.4 mo), 12 were determined to have tumor progression, while 7 had treatment response after 6 months of ICI treatment. Only interval change of rADC was suggestive of treatment response. Patients with treatment response (6/7: 86%) had interval increased rADC, while 11/12 (92%) with tumor progression had decreased rADC (P = 0.001). Interval change in rCBV, Ktrans, Vp, and Ve were not indicative of treatment response within 6 months.

CONCLUSIONS

In patients with recurrent GBM, interval change in rADC is promising in assessing treatment response versus progression within the first 6 months following ICI treatment.

KEY POINTS

• In recurrent GBM treated with ICIs, interval change in rADC suggests early treatment response.• Interval change in rADC can be used as an imaging biomarker to determine PFS6.• Interval change in MR perfusion and permeability measures do not suggest ICI treatment response.

Efficacy of endovascular intratumoral embolization for meningioma: assessment using dynamic susceptibility contrast-enhanced perfusion-weighted imaging

BACKGROUND

In preoperative embolization for intracranial meningioma, endovascular intratumoral embolization is considered to be more effective for the reduction of tumorous vascularity than proximal feeder occlusion. In this study, we aimed to reveal different efficacies for reducing tumor blood flow in meningiomas by comparing endovascular intratumoral embolization and proximal feeder occlusion using dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI).

METHODS

28 consecutive patients were included. DSC-PWI was performed before and after embolization for intracranial meningiomas. Normalized tumor blood volume (nTBV) of voxels of interest of whole tumors were measured from the DSC-PWI data before and after embolization. ΔnTBV% was compared between the cases that received intratumoral embolization and proximal feeder occlusion.

RESULTS

ΔnTBV% in the intratumoral embolization group (42.4±29.8%) was higher than that of the proximal feeder occlusion group (15.3±14.3%, p=0.0039). We used three types of embolic materials and ΔnTBV% did not differ between treatments with or without the use of each material: 42.8±42.4% vs 28.7±20.1% for microspheres (p=0.12), 36.1±20.6% vs 28.1±41.1% for n-butyl cyanoacrylate (p=0.33), and 32.3±37.3% vs 34.1±19.0% for bare platinum coils (p=0.77).

CONCLUSIONS

The flow reduction effect of intratumoral embolization was superior to that of proximal feeder occlusion in preoperative embolization for intracranial meningioma in an assessment using DSC-PWI.

Emerging Utility of Applied Magnetic Resonance Imaging in the Management of Traumatic Brain Injury

Traumatic brain injury (TBI) is a widespread and expensive problem globally. The standard diagnostic workup for new TBI includes obtaining a noncontrast computed tomography image of the head, which provides quick information on operative pathologies. However, given the limited sensitivity of computed tomography for identifying subtle but meaningful changes in the brain, magnetic resonance imaging (MRI) has shown better utility for ongoing management and prognostication after TBI. In recent years, advanced applications of MRI have been further studied and are being implemented as clinical tools to help guide care. These include functional MRI, diffusion tensor imaging, MR perfusion, and MR spectroscopy. In this review, we discuss the scientific basis of each of the above techniques, the literature supporting their use in TBI, and how they may be clinically implemented to improve the care of TBI patients.

Magnetic Resonance Perfusion Changes of Arteriovenous Malformations Treated with Stereotactic Radiosurgery

BACKGROUND

The latency period from stereotactic radiosurgery (SRS) to obliteration of arteriovenous malformations (AVM) requires continuous imaging surveillance. Magnetic resonance (MR) perfusion is promising for noninvasive monitoring of AVMs after SRS. We studied longitudinal MR perfusion changes of brain AVMs treated with SRS.

METHODS

Consecutive patients treated for brain AVMs using SRS who had MR perfusion imaging studies performed before and at least once after SRS were studied. We estimated ipsilateral/contralateral brain hemisphere ratios of MR perfusion indexes, including regional cerebral blood flow (rCBF) and relative cerebral blood volume (rCBV), in the AVM nidus, perinidal region, and remote anterior and posterior brain regions.

RESULTS

Eleven patients (6 women; median age, 21 years) underwent SRS (median prescription dose, 18 Gy; range, 12-20 Gy) for brain AVMs (median Spetzler-Martin grade 2 and median volume 4.6 mL). Before the SRS, rCBV and rCBF ratios were significantly higher in the AVM nidus compared with other investigated brain regions (P < 0.001). Median time from SRS to the first and last post-SRS MR perfusion studies was 8 and 35 months, respectively. There was a statically significant decrease of rCBV (P = 0.043) and rCBF (P = 0.036) ratios in the AVM nidus, but not other brain regions, during post-SRS follow-up.

CONCLUSIONS

There is a gradual decrease of rCBV and rCBF in the AVM nidus after SRS. MR perfusion imaging is promising for monitoring of hemodynamic changes of AVMs after SRS. Larger studies investigating clinical value of MR perfusion imaging for AVMs after SRS are warranted.

The Application of MR Spectroscopy and MR Perfusion in Cerebral Syphilitic Gumma: A Case Report

Cerebral syphilitic gumma is a rare disease and can be misdiagnosed as a common brain tumor when only conventional imaging results are adopted. Differentiating between syphilitic gumma and tumors may be achieved by applying advanced magnetic resonance (MR) techniques, such as MR spectroscopy and MR perfusion. However, the MR perfusion characteristics of cerebral syphilitic gumma have not been reported yet. Here, we report a case of cerebral syphilitic gumma in a 52-year-old woman and discuss the imaging features of conventional MR, MR spectroscopy, and MR perfusion. The results suggest that the application of MR spectroscopy and MR perfusion could provide additional information that contributes to the diagnosis of cerebral syphilitic gumma.

Percentage signal intensity recovery: A step ahead of rCBV in DSC MR perfusion imaging for the differentiation of common neoplasms of brain

Context

Relative cerebral blood volume (rCBV) and percentage signal recovery (PSR) obtained from T2* dynamic susceptibility contrast magnetic resonance imaging are important parameters for brain tumor assessment.

Aim

To study the accuracy of PSR in the differentiation of low-grade glioma, high-grade glioma, lymphoma, and metastases particularly in comparison to rCBV.

Settings and Design

Retrospective observational study.

Subjects and Methods

Study included pathologically confirmed cases of 10 low-grade glioma, 22 high-grade glioma, 6 lymphoma, and 12 metastases (Total 50). PSR, relative PSR (rPSR), and rCBV were calculated.

Statistical Analysis Used

Accuracy of these parameters studied statistically using analysis of variance and ROC (Receiver operating characteristic) curves.

Results

rCBV was higher in metastases (3.45 ± 2.82) and high-grade glioma (3.47 ± 1.62), whereas was low in lymphoma (1.03 ± 0.74) and low-grade glioma (1.43 ± 0.47) with P value of 0.030. PSR was low in metastases (48 ± 16.18), intermediate in glioma (73.24 ± 6.39 and 88.26 ± 6.05, high and low grade), and high in lymphoma (112.16 ± 10.57) with P value < 0.000. rPSR was higher for lymphoma (1.73 ± 0.57) than high-grade glioma (0.85 ± 0.11) and metastasis (0.69 ± 0.19) with P value <.000. Area under ROC for PSR was greater than rCBV in differentiating metastases from lymphoma (1.00 vs 0.13), high-grade glioma from lymphoma (1.00 vs 0.38), high-grade glioma from metastases (0.89 vs 0.58), and high-grade glioma from low-grade glioma (0.96 vs 0.03) with excellent curve characteristics. F values for PSR and rPSR from ANOVA analysis were 71.47 and 36.77, was better than rCBV (3.84) in differentiating these groups.

Conclusions

Percentage of signal recovery shows low recovery values in metastases, intermediate recovery values in glioma, and overshoot in lymphoma. PSR values show lower overlap than rCBV between lymphoma and metastases; and between high grade glioma and metastases. PSR difference is also higher than rCBV between low- and high-grade gliomas. Hence, PSR can potentially help as an additional perfusion parameter in the preoperative differentiation of these tumors.

Linear scleroderma en coup de sabre presenting with seizures

Scleroderma is a rare connective tissue disorder categorized into systemic sclerosis and localized scleroderma, also called morphea. Linear scleroderma of the scalp, also called en coup de sabre, is infrequently associated with neurologic symptoms. We describe a case of linear scleroderma en coup de sabre in a 28-year-old female presenting with seizures and characteristic cutaneous lesions. Imaging findings over a course of 7 years demonstrated waxing and waning signal changes. MR perfusion and spectroscopic imaging, demonstrating decreased cerebral blood volume, increased mean transit time, and decreased metabolites, was performed during a time of progressing radiological and clinical findings. Comparison with other reports in the literature supported several clinical and imaging findings that while not pathognomic, highly suggest the diagnosis of linear scleroderma en coup de sabre. Hyperintense signal on T2W magentic resonance imaging and contrast enhancement on computed tomography and magnetic resonance imaging have been the most commonly described imaging findings. To our knowledge, no previous description of spectroscopic or perfusion imaging of linear scleroderma en coup de sabre have been reported. It is our hope that this report may add MRS and magnetic resonance perfusion findings to a growing knowledge of this rare entity.

Bilateral posterior cerebral artery territory infarction in a SARS-Cov-2 infected patient: discussion about an unusual case

In time of SARS-Cov2 pandemic, neurologists need to be vigilant for cerebrovascular complications of Covid-19. We present a case of bilateral occipito-temporal infarction revealed by a sudden cortical blindness with haemorrhagic transformation after intravenous thrombolysis in a diabetic patient infected by Covid-19. Differential diagnoses are discussed in front of this unusual presentation and evolution.

The role of dynamic contrast-enhanced MRI in evaluation of percutaneous transluminal angioplasty outcome in patients with critical limb ischemia

PURPOSE

Imaging modalities such as CTA and MRA provide significant information about the distribution of macrovascular lesions of the limbs in patients with peripheral arterial disease but not for the local microvascular perfusion of the feet. The purpose of this study is to evaluate foot perfusion in patients with critical limb ischemia (CLI) and estimate percutaneous transluminal angioplasty (PTA) results, using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

METHODS

Ten patients (6 male, median age 68 years) with CLI were examined. All patients underwent DCE-MRI of the lower limb before and within first month after PTA. Perfusion parameters such as blood flow (BF), Ktrans, Kep were analyzed and applied for statistical comparisons. The studies were also examined by a second observer to determine inter-observer reproducibility.

RESULTS

Revascularization was technically successful in all patients and mean ankle brachial index (ABI) increased from 0.37 ± 0.18 to 0.76 ± 0.23, p < 0.05. After PTA, mean BF increased from 6.232 ± 2.867-9.867 ± 2.965 mL/min/100 g, K^trans increased from 0.060 ± 0.022 to 0.107 ± 0.041 min^-1 and K_ep increased from 0.103 ± 0.024 to 0.148 ± 0.024 min^-1, p < 0.05. All measurements demonstrated very good inter-observer reliability with an ICC > 0.85 for all perfusion parameters.

CONCLUSIONS

DCE-MRI is a safe and reproducible modality for the diagnosis of foot hypo-perfusion. It seems also to be a promising tool for evaluation of PTA outcome, as significant restitution of perfusion parameters was observed after successful revascularization.

Advanced Imaging Techniques in Diagnosis of Posterior Reversible Encephalopathy Syndrome (PRES)

Diagnosis of Posterior Reversible Encephalopathy Syndrome (PRES) in some circumstances can be challenging and structural imaging may not be sufficient to distinguish it from other differential diagnostic considerations. Advanced imaging techniques, such as MR spectroscopy or positron emission tomography (PET) can provide additional information to determine the diagnosis. Other techniques, such as susceptibility weighted imaging (SWI) improves detection of hemorrhage which has prognostic role. CT or MR Perfusion as well as Single-Photon Emission Computed Tomography (SPECT) are more useful to understand the underlying vasculopathic changes in PRES and may answer some of the unresolved controversies in pathophysiology of this complex disease. In this review we summarized the findings of previous studies using these advanced methods and their utilities in diagnosis or prognosis of PRES.

Multidelay Arterial Spin Labeling MRI in the Assessment of Cerebral Blood Flow: Preliminary Clinical Experience in Pediatrics

OBJECTIVES

We attempted to demonstrate the clinical applicability and utility of a three-dimensional multidelay arterial spin labeling magnetic resonance imaging technique in pediatric neuroimaging through a series of case studies.

METHODS

Whole-brain three-dimensional multidelay arterial spin labeling data were acquired in five pediatric patients with different neurological conditions using 3 mm to 4 mm slices and a scan time of six to seven minutes.

RESULTS

Three-dimensional multidelay arterial spin labeling provided complementary diagnostic information via quantitative cerebral blood flow and arterial transit time maps.

CONCLUSIONS

Three-dimensional multidelay arterial spin labeling sequence provides simultaneous quantification of cerebral blood flow and arterial transit time and is feasible for pediatric patients.

Using Magnetic Resonance Perfusion to Stratify Overall Survival in Treated High-Grade Gliomas

BACKGROUND

MR perfusion imaging is a relatively new technique that may aid in identifying recurrent tumor (RT) in those with radically treated high-grade gliomas (HGG). We aim to assess the relationship between dynamic susceptibility contrast-enhanced MR perfusion (DSC-MRP) and overall survival to establish a baseline for future research and to determine the utility of DSC-MRP as a clinical decision-making and prognostic tool.

METHODS

We conducted a retrospective cohort study. Adults with pathologically confirmed HGG at the Juravinski Cancer Centre, Ontario between January 2011 and April 2014 with at least one post-treatment DSC-MRP were included. DSC-MRP was interpreted as positive or negative for tumor recurrence by experienced radiologists. The primary outcome was overall survival.

RESULTS

Sixty-one patients were enrolled. Median survival for patients with a positive DSC-MRP scan was 4.5 months compared with 10.2 months for those with a negative DSC-MRP scan (hazard ratio [unadjusted] = 2.51; 95% confidence interval = 1.10-5.67; p-value = 0.03). Multivariable modeling (adjusted) that included all pre-selected variables showed similar results.

CONCLUSION

Survival time in patients with HGG is generally low, and almost all patients will demonstrate RT. Our data suggest a positive DSC-MRP correlates with lower overall survival and may signify the presence of highly active RT. These results generate a hypothesis that there may be a prognostic role for the use of serial DSC-MRP for tumor surveillance. More importantly, this biomarker may aid in decision making for treatment plans and palliation.

Update on MR imaging of the pulmonary vasculature

Magnetic resonance imaging (MRI) plays an increasingly important role in the non-invasive evaluation of the pulmonary vasculature. MR angiographic (MRA) techniques provide morphological information, while MR perfusion techniques provide functional information of the pulmonary vasculature. Contrast-enhanced MRA can be performed at high spatial resolution using 3D T1-weighted spoiled gradient echo sequence or at high temporal resolution using time-resolved techniques. Non-contrast MRA can be performed using 3D steady state free precession, double inversion fast spin echo, time of flight or phase contrast sequences. MR perfusion can be done using dynamic contrast-enhanced technique or using non-contrast techniques such as arterial spin labelling and time-resolved imaging of lungs during free breathing with Fourier decomposition analysis. MRI is used in the evaluation of acute and chronic pulmonary embolism, pulmonary hypertension and other vascular abnormalities, congenital anomalies and neoplasms. In this article, we review the different MR techniques used in the evaluation of pulmonary vasculature and its clinical applications.

Advanced MR Imaging Techniques for Pancreas Imaging

Advances in MR imaging with optimization of hardware, software, and techniques have allowed for an increased role of MR in the identification and characterization of pancreatic disorders. Diffusion-weighted imaging improves the detection and staging of pancreatic neoplasms and aides in the evaluation of acute, chronic and autoimmune pancreatitis. The use of secretin-enhanced MR cholangiography improves the detection of morphologic ductal anomalies, and assists in the characterization of pancreatic cystic lesions and evaluation of acute and chronic pancreatitis. Emerging MR techniques such as MR perfusion, T1 mapping/relaxometry, and MR elastography show promise in further evaluating pancreatic diseases.

Hypoperfusion in lenticulostriate arteries territory related to unexplained early neurological deterioration after intravenous thrombolysis

BACKGROUND

Early neurological deterioration occurs in approximately 10% acute ischemic stroke patients after thrombolysis. Over half of the early neurological deterioration occurred without known causes and is called unexplained early neurological deterioration.

AIMS

We aimed to explore the development of early neurological deterioration at 24 h after thrombolysis, and whether it could be predicted by the presence of baseline hypoperfusion in lenticulostriate arteries territory in acute ischemic stroke patients.

METHODS

We retrospectively reviewed our prospectively collected database of acute ischemic stroke patients in the unilateral middle cerebral artery territory who had baseline perfusion image and received thrombolysis. Unexplained early neurological deterioration was defined as ≥ 2 points increase of National Institutes of Health Stroke Scale (NIHSS) from baseline to 24 h, without known causes. Hypoperfusion lesions in different territories were identified on perfusion maps.

RESULTS

A total of 306 patients were included in analysis. Patients with pure lenticulostriate arteries hypoperfusion (defined as the presence of hypoperfusion in lenticulostriate artery territory, but not in middle cerebral artery terminal branch territory) were more likely to have unexplained early neurological deterioration than others (27.6% vs. 6.1%; OR, 5.974; p = 0.001), after adjusting for age, baseline NIHSS and onset to treatment time.

CONCLUSIONS

Patients presenting hypoperfusion in pure lenticulostriate arteries territory were easier to experience unexplained early neurological deterioration.

[The use of MR perfusion in assessing the efficacy of treatment for malignant brain tumors]

This literature review analyzes the capabilities of magnetic resonance imaging (MRI)-based cerebral perfusion for differentiation between post-radiation changes (e.g., radionecrosis) and continued growth. The technique is compared with other highly informative radiodiagnostic techniques used in neuroradiology. The use of MR perfusion is important in a comprehensive examination protocol. Trends in the technique development are analyzed.

Selective middle cerebral artery occlusion in the rabbit: Technique and characterization with pathologic findings and multimodal MRI

BACKGROUND

A reliable animal model of ischemic stroke is vital for pre-clinical evaluation of stroke therapies. We describe a reproducible middle cerebral artery (MCA) embolic occlusion in the French Lop rabbit characterized with multimodal MRI and histopathologic tissue analysis.

NEW METHOD

Fluoroscopic-guided microcatheter placement was performed in five consecutive subjects with angiographic confirmation of MCA occlusion with autologous clot. Multimodal MRI was obtained prior to occlusion and up to six hours post after which repeat angiography confirmed sustained occlusion. The brain was harvested for histopathologic examination.

RESULTS

Angiography confirmed successful MCA catheterization and durable (>6 h) MCA occlusion in all animals. There was increase of ADC volume over time and variable final core volume presumably related to individual variation in collateral flow. FLAIR hyperintensity indicative of cytotoxic edema and parenchymal contrast enhancement reflective of blood brain barrier disruption was observed over time. Tissue staining of the ischemic brain showed edema and structural alterations consistent with infarction.

COMPARISON WITH EXISTING METHODS

This study describes a technique of selective catheterization and embolic occlusion of the MCA in the rabbit with MRI characterization of evolution of ischemia in the model.

CONCLUSIONS

We demonstrate the feasibility of a rabbit model of embolic MCA occlusion with angiographic documentation. Serial MR imaging demonstrated changes comparable to those observed in human ischemic stroke, confirmed histopathologically.

Spatial-temporal perfusion patterns of the human liver assessed by pseudo-continuous arterial spin labeling MRI

PURPOSE

To investigate the capabilities of a modern pseudo-continuous arterial spin labeling (PCASL) technique for non-invasive assessment of the temporal and spatial distribution of the liver perfusion in healthy volunteers on a clinical MR system at 3T.

MATERIALS AND METHODS

A 2D-PCASL multi-slice echo planar imaging sequence was adapted to the specific conditions in liver: a) labeling by PCASL was optimized to the flow characteristics in the portal vein, b) background suppression was applied for reduction of motion related artifacts, c) post labeling delays (PLDs) were varied over a large range (0.7-3.5s) in order to get better insight in the temporal and spatial distribution of tagged blood in the liver, and d) a special timed-breathing protocol was used allowing for recording of 16 to 18 label-control image pairs and a reference M0 image for each of 4 to 6 slices within approx. 5min for one PLD.

RESULTS

Measurements with multiple PLDs showed dominating perfusion signal in macroscopic blood vessels for PLDs up to 1.5 s, whereas pure liver parenchyma revealed maximum perfusion signal for a PLD of approx. 2 s, and detectable signal up to PLDs of 3.5 s. Data fitting to a perfusion model for liver provided a mean global perfusion of 153±15ml/100g/min and a mean transit time of 1938±332ms in liver parenchyma. Measurements with a single PLD of 2 s demonstrated that portal-venous and arterial perfusion components can be measured separately by two measurements with two different positions of the labeling plane (one for labeling of the global hepatopetal blood flow and one for selective labeling of the portal blood flow only). Relative contribution of blood from the hepatic artery to the global liver perfusion, the hepatic perfusion index (HPI), amounted to approx. 23%.

CONCLUSION

Modern and adapted protocols for assessment of liver perfusion by PCASL have the potential to provide perfusion and blood transit time maps in reasonable acquisition time.

The Imaging of Localization Related Symptomatic Epilepsies: The Value of Arterial Spin Labelling Based Magnetic Resonance Perfusion

Accurate identification of the epileptogenic zone is an important prerequisite in presurgical evaluation of refractory epilepsy since it affects seizure-free outcomes. Apart from structural magnetic resonance imaging (sMRI), delineation has been traditionally done with electroencephalography and nuclear imaging modalities. Arterial spin labelling (ASL) sequence is a non-contrast magnetic resonance perfusion technique capable of providing similar information. Similar to single-photon emission computed tomography, its utility in epilepsy is based on alterations in perfusion linked to seizure activity by neurovascular coupling. In this article, we discuss complementary value that ASL can provide in the evaluation and characterization of some basic substrates underlying epilepsy. We also discuss the role that ASL may play in sMRI negative epilepsy and acute scenarios such as status epilepticus.

Multiparametric MRI for Differentiation of Radiation Necrosis From Recurrent Tumor in Patients With Treated Glioblastoma

OBJECTIVE

Differentiation of radiation necrosis (RN) from recurrent tumor (RT) in treated patients with glioblastoma remains a diagnostic challenge. The purpose of this study is to evaluate the diagnostic performance of multiparametric MRI in distinguishing RN from RT in patients with glioblastoma, with the use of a combination of MR perfusion and diffusion parameters.

MATERIALS AND METHODS

Patients with glioblastoma who had a new enhancing mass develop after completing standard treatment were retrospectively evaluated. Apparent diffusion coefficient (ADC), volume transfer constant (K^trans), and relative cerebral blood volume (rCBV) values were calculated from the MR images on which the enhancing lesions first appeared. Repeated measure of analysis, logistic regression, and ROC analysis were performed.

RESULTS

Of a total of 70 patients evaluated, 46 (34 with RT and 12 with RN) met our inclusion criteria. Patients with RT had significantly higher mean rCBV (p < 0.001) and K^trans (p = 0.006) values and lower ADC values (p = 0.004), compared with patients with RN. The overall diagnostic accuracy was 85.8% for rCBV, 75.5% for K^trans, and 71.3% for ADC values. The logistic regression model showed a significant contribution of rCBV (p = 0.024) and K^trans (p = 0.040) as independent imaging classifiers for differentiation of RT from RN. Combined use of rCBV and K^trans at threshold values of 2.2 and 0.08 min^-1, respectively, improved the overall diagnostic accuracy to 92.8%.

CONCLUSION

In patients with treated glioblastoma, rCBV outperforms ADC and K^trans as a single imaging classifier to predict recurrent tumor versus radiation necrosis; however, the combination of rCBV and K^trans may be used to improve overall diagnostic accuracy.

Perfusion magnetic resonance imaging in pediatric brain tumors

PURPOSE

The use of DSC-MR imaging in pediatric neuroradiology is gradually growing. However, the number of studies listed in the literature remains limited. We propose to assess the perfusion and permeability parameters in pediatric brain tumor grading.

METHODS

Thirty children with a brain tumor having benefited from a DSC-MR perfusion sequence have been retrospectively explored. Relative CBF and CBV were computed on the ROI with the largest lesion coverage. Assessment of the lesion's permeability was also performed through the semi-quantitative PSR parameter and the K2 model-based parameter on the whole-lesion ROI and a reduced ROI drawn on the permeability maps. A statistical comparison of high- and low-grade groups (HG, LG) as well as a ROC analysis was performed on the histogram-based parameters.

RESULTS

Our results showed a statistically significant difference between LG and HG groups for mean rCBV (p < 10^-3), rCBF (p < 10^-3), and for PSR (p = 0.03) but not for the K2 factor (p = 0.5). However, the ratio K2/PSR was shown to be a strong discriminating factor between the two groups of lesions (p < 10^-3). For rCBV and rCBF indicators, high values of ROC AUC were obtained (> 0.9) and mean value thresholds were observed at 1.07 and 1.03, respectively. For K2/PSR in the reduced area, AUC was also superior to 0.9.

CONCLUSIONS

The implementation of a dynamic T2* perfusion sequence provided reliable results using an objective whole-lesion ROI. Perfusion parameters as well as a new permeability indicator could efficiently discriminate high-grade from low-grade lesions in the pediatric population.

Perfusion Imaging in Neuro-Oncology: Basic Techniques and Clinical Applications

Perfusion imaging is a method for assessing the flow of blood occurring at the tissue level and can be accomplished by both CT and MR perfusion techniques. The use of perfusion imaging has increased substantially in the past decade, particularly in neuro-oncologic imaging, where it is has been used for brain tumor grading and directing biopsies or targeted therapy, as well as for the evaluation of treatment response and disease progression. This article discusses the basic principles and techniques of perfusion imaging, as well as its applications in neuro-oncology.

Comparison between MR Perfusion and 18F-FDG PET in Differentiating Tumor Recurrence from Nonneoplastic Contrast-enhancing Tissue

Objective: Comparison of the accuracy of MR perfusion and 18-FDG-PET for differentiating tumor progression from nonneoplastic contrast-enhancing tissue. Methods and Materials: Retrospective review of MR perfusion and 18-FDG-PET in 23 cases of primary brain tumors (17 high grade and 6 low grade glial neoplasms) and 5 cases of metastatic lesions with enhancing lesions on post-treatment MRI was performed. The accuracy of MR perfusion versus 18-FDG-PET for distinguishing between nonneoplastic contrast-enhancing tissue and tumor recurrence was assessed. Results: Both CBV (p<0.004) and SUV (p<0.02) are higher in recurrent tumors than necrosis. MR perfusion has an accuracy of 94.5% for differentiating between tumor recurrence and necrosis, while 18-FDG-PET has an accuracy of 85.1% for differentiating between tumor recurrence and nonneoplastic contrast-enhancing tissue. Conclusion: Overall, recurrent tumor demonstrates significantly higher CBV and SUV than nonneoplastic contrast-enhancing tissue. However, MR perfusion appears to be more accurate than FDG PET for distinguishing the two entities.

MR imaging of brain pilocytic astrocytoma: beyond the stereotype of benign astrocytoma

BACKGROUND

Pilocytic astrocytoma (PA) is the most common pediatric brain glioma and is considered the prototype of benign circumscribed astrocytoma. Despite its low malignancy, the CT and MRI features of brain PA may resemble those of much more aggressive brain tumors. Misdiagnosis of PA is particularly easy when it demonstrates MR morphological and non-morphological findings that are inconsistent with its non-aggressive nature and that overlap with the features of more aggressive brain tumors.

METHOD

Basing on the evidence that the variation in the histological, genetic, and metabolic "fingerprint" for brain PA is dependent on tumor location, and the hypothesis that tumor location is related to the broad spectrum of morphological and non-morphological MR imaging findings, the authors discuss the MR imaging appearance of brain PA using a location-based approach to underline the typical and less typical imaging features and the main differential diagnosis of brain PA. A brief summary of the main pathological and clinical features, the natural history, and the treatment of brain PA is also provided.

RESULT

A combination of morphological and non-morphological MR imaging features and a site-based approach to differential diagnosis are required for a pre-operative diagnosis. The new "cutting-edge" MR imaging sequences have the potential to impact the ease and confidence of pediatric brain tumor interpretation and offer a more efficient diagnostic work-up.

CONCLUSIONS

Although the typical imaging features of brain pilocytic astrocytoma make radiological diagnosis relatively easy, an atypical and more aggressive appearance can lead to misdiagnosis. Knowing the broad spectrum of imaging characteristics on conventional and advanced MR imaging is important for accurate pre-operative radiological diagnosis and correctly interpreting changes during follow-up.

Acetazolamide-augmented dynamic BOLD (aczBOLD) imaging for assessing cerebrovascular reactivity in chronic steno-occlusive disease of the anterior circulation: An initial experience

The purpose of this study was to measure cerebrovascular reactivity (CVR) in chronic steno-occlusive disease using a novel approach that couples BOLD imaging with acetazolamide (ACZ) vasoreactivity (aczBOLD), to evaluate dynamic effects of ACZ on BOLD and to establish the relationship between aczBOLD and dynamic susceptibility contrast (DSC) perfusion MRI. Eighteen patients with unilateral chronic steno-occlusive disease of the anterior circulation underwent a 20-min aczBOLD imaging protocol, with ACZ infusion starting at 5 min of scan initiation. AczBOLD reactivity was calculated on a voxel-by-voxel basis to generate CVR maps for subsequent quantitative analyses. Reduced CVR was observed in the diseased vs. the normal hemisphere both by qualitative and quantitative assessment (gray matter (GM): 4.13% ± 1.16% vs. 4.90% ± 0.98%, P = 0.002; white matter (WM): 2.83% ± 1.23% vs. 3.50% ± 0.94%, P = 0.005). In all cases BOLD signal began increasing immediately following ACZ infusion, approaching a plateau at ~ 8.5 min after infusion, with the tissue volume of reduced augmentation increasing progressively with time, peaking at 2.60 min (time range above 95% of the maximum value: 0–4.43 min) for the GM and 1.80 min (time range above 95% of the maximum value: 1.40–3.53 min) for the WM. In the diseased hemisphere, aczBOLD CVR significantly correlated with baseline DSC time-to-maximum of the residue function (T_max) (P = 0.008 for the WM) and normalized cerebral blood flow (P = 0.003 for the GM, and P = 0.001 for the WM). AczBOLD provides a novel, safe, easily implementable approach to CVR measurement in the routine clinical environments. Further studies can establish quantitative thresholds from aczBOLD towards identification of patients at heightened risk of recurrent ischemia and cognitive decline.

•

A method coupling BOLD with ACZ challenge (aczBOLD) for CVR assessment was proposed.

•

Compromised CVR was detected in patients with cerebrovascular disease.

•

Dynamic effects of ACZ on BOLD were characterized.

•

CVR correlated with baseline dynamic susceptibility contrast perfusion MRI.

Utility of perfusion imaging in acute stroke treatment: a systematic review and meta-analysis

BACKGROUND

Variability in imaging protocols and techniques has resulted in a lack of consensus regarding the incorporation of perfusion imaging into stroke triage and treatment. The objective of our study was to evaluate the available scientific evidence regarding the utility of perfusion imaging in determining treatment eligibility in patients with acute stroke and in predicting their clinical outcome.

METHODS

We performed a systematic review of the literature using PubMed, Web of Science, and Cochrane Library focusing on themes of medical imaging, stroke, treatment, and outcome (CRD42016037817). We included randomized controlled trials, cohort studies, and case-controlled studies published from 2011 to 2016. Two independent reviewers conducted the study appraisal, data abstraction, and quality assessments of the studies.

RESULTS

Our literature search yielded 13 studies that met our inclusion criteria. In total, 994 patients were treated with the aid of perfusion imaging compared with 1819 patients treated with standard care. In the intervention group 51.1% of patients had a favorable outcome at 3 months compared with 45.6% of patients in the control group (p=0.06). Subgroup analysis of studies that used multimodal therapy (IV tissue plasminogen activator, endovascular thrombectomy) showed a significant benefit of perfusion imaging (OR 1.89, 95% CI 1.43 to 2.51, p<0.01).

CONCLUSIONS

Perfusion imaging may represent a complementary tool to standard radiographic assessment in enhancing patient selection for reperfusion therapy, with a subset of patients having up to 1.9 times the odds of achieving independent functional status at 3 months. This is particularly important as patients selected based on perfusion status often included individuals who did not meet the current treatment eligibility criteria.

Advanced MR imaging in hemispheric low-grade gliomas before surgery; the indications and limits in the pediatric age

INTRODUCTION

Advanced magnetic resonance imaging (MRI) techniques is an umbrella term that includes diffusion (DWI) and diffusion tensor (DTI), perfusion (PWI), spectroscopy (MRS), and functional (fMRI) imaging. These advanced modalities have improved the imaging of brain tumors and provided valuable additional information for treatment planning. Despite abundant literature on advanced MRI techniques in adult brain tumors, few reports exist for pediatric brain ones, potentially because of technical challenges.

REVIEW OF THE LITERATURE

The authors review techniques and clinical applications of DWI, PWI, MRS, and fMRI, in the setting of pediatric hemispheric low-grade gliomas.

PERSONAL EXPERIENCE

The authors propose their personal experience to highlight benefits and limits of advanced MR imaging in diagnosis, grading, and presurgical planning of pediatric hemispheric low-grade gliomas.

DISCUSSION

Advanced techniques should be used as complementary tools to conventional MRI, and in theory, the combined use of the three techniques should ensure achieving the best results in the diagnosis of hemispheric low-grade glioma and in presurgical planning to maximize tumor resection and preserve brain function.

FUTURE PERSPECTIVES

In the setting of pediatric neurooncology, these techniques can be used to distinguish low-grade from high-grade tumor. However, these methods have to be applied on a large scale to understand their real potential and clinical relapse, and further technical development is required to reduce the excessive scan times and other technical limitations.

Arterial spin labeling: Pathologically proven superiority over conventional MRI for detection of high-grade glioma progression after treatment

BACKGROUND

Standard of care for high-grade gliomas (HGGs) includes surgical debulking and adjuvant chemotherapy and radiation. Patients under treatment require frequent clinical and imaging monitoring for therapy modulation. Differentiating tumor progression from treatment-related changes can be challenging on conventional MRI, resulting in delayed recognition of tumor progression. Arterial spin labeling (ASL) may be more sensitive for tumor progression.

MATERIALS AND METHODS

ASL and associated conventional MR images obtained in patients previously treated for HGGs and before biopsy or re-resection were reviewed by three neuroradiologists who were blinded to the histopathologic results. Regions of interest (ROIs) of greatest perfusion were chosen by consensus, and mirror-image contralateral ROIs were also placed. Sensitivity of ASL for tumor progression was compared with those of contrast-enhanced T1-weighted (T1W-CE) and fluid-attenuated inversion recovery (FLAIR) images using McNemar's test. We tested for an association between cerebral blood flow (CBF) and apparent diffusion correlation (ADC) using a Hotelling-Lawley trace. Finally, we used a Pearson's analysis to test for a correlation between CBF and percentage of tumor within each resection.

RESULTS

Twenty-two patients were studied. ASL demonstrated hyperperfusion in all cases with mean CBF ratio 3.37 (±1.71). T1W-CE and FLAIR images were positive in 15 (p = 0.0233) and 16 (p = 0.0412) cases, respectively. There was no association between ADC and CBF (p = 0.687). There was a correlation between CBF and percentage of tumor (p = 0.048).

CONCLUSION

ASL may be more sensitive than conventional MR sequences for the detection of tumor progression in patients treated for HGGs.

MR perfusion-weighted imaging in the evaluation of high-grade gliomas after treatment: a systematic review and meta-analysis

BACKGROUND

Distinction between tumor and treatment related changes is crucial for clinical management of patients with high-grade gliomas. Our purpose was to evaluate whether dynamic susceptibility contrast-enhanced (DSC) and dynamic contrast enhanced (DCE) perfusion-weighted imaging (PWI) metrics can effectively differentiate between recurrent tumor and posttreatment changes within the enhancing signal abnormality on conventional MRI.

METHODS

A comprehensive literature search was performed for studies evaluating PWI-based differentiation of recurrent tumor and posttreatment changes in patients with high-grade gliomas (World Health Organization grades III and IV). Only studies published in the "temozolomide era" beginning in 2005 were included. Summary estimates of diagnostic accuracy were obtained by using a random-effects model.

RESULTS

Of 1581 abstracts screened, 28 articles were included. The pooled sensitivities and specificities of each study's best performing parameter were 90% and 88% (95% CI: 0.85-0.94; 0.83-0.92) and 89% and 85% (95% CI: 0.78-0.96; 0.77-0.91) for DSC and DCE, respectively. The pooled sensitivities and specificities for detecting tumor recurrence using the 2 most commonly evaluated parameters, mean relative cerebral blood volume (rCBV) (threshold range, 0.9-2.15) and maximum rCBV (threshold range, 1.49-3.1), were 88% and 88% (95% CI: 0.81-0.94; 0.78-0.95) and 93% and 76% (95% CI: 0.86-0.98; 0.66-0.85), respectively.

CONCLUSIONS

PWI-derived thresholds separating viable tumor from treatment changes demonstrate relatively good accuracy in individual studies. However, because of significant variability in optimal reported thresholds and other limitations in the existing body of literature, further investigation and standardization is needed before implementing any particular quantitative PWI strategy across institutions.

Normal saline as a natural intravascular contrast agent for dynamic perfusion-weighted MRI of the brain: Proof of concept at 1.5T

PURPOSE

Gadolinium-based contrast agents have associated risks. Normal saline (NS) is a nontoxic sodium chloride water solution that can significantly increase the magnetic resonance imaging (MRI) relaxation times of blood via transient hemodilution (THD). The purpose of this pilot study was to test in vivo in the head the potential of normal saline as a safer, exogenous perfusion contrast agent.

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act (HIPAA)-compliant prospective study was approved by the local Institutional Review Board (IRB): 12 patients were scanned with T₁ -weighted inversion recovery turbo spin echo pulse sequence at 1.5T. The dynamic inversion recovery pulse sequence was run before, during, and after the NS injection for up to 5 minutes: 100 ml of NS was power-injected via antecubital veins at 3-4 ml/s. Images were processed to map maximum enhancement area-under-the-curve, time-to-peak, and mean-transit-time. These maps were used to identify the areas showing significant NS injection-related signal and to generate enhancement time curves. Hardware and pulse sequence stability were studied via phantom experimentation. Main features of the time curves were tested against theoretical modeling of THD signal effects using inversion recovery pulse sequences. Pearson correlation coefficient (R) mapping was used to differentiate genuine THD effects from motion confounders and noise.

RESULTS

The scans of 8 out of 12 patients showed NS injection-related effects that correlate in magnitude with tissue type (gray matter ∼15% and white matter ∼3%). Motion artifacts prevented ascertaining NS signal effects in the remaining four patients. Positive and negative time curves were observed in vivo and this dual THD signal polarity was also observed in the theoretical simulations. R-histograms that were approximately constant in the range 0.1 < |R| < 0.8 and leading to correlation fractions of F_corr (|R| > 0.5) = 0.45 and 0.59 were found to represent scans with genuine THD signal effects.

CONCLUSION

A measurable perfusion effect in brain tissue was demonstrated in vivo using NS as an injectable intravascular contrast agent. J. Magn. Reson. Imaging 2016;44:1580-1591.