Conventional and Advanced Magnetic Resonance Imaging Assessment of Non-Enhancing Peritumoral Area in Brain Tumor.

The non-enhancing peritumoral area (NEPA) is defined as the hyperintense region in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images surrounding a brain tumor. The NEPA corresponds to different pathological processes, including vasogenic edema and infiltrative edema. The analysis of the NEPA with conventional and advanced magnetic resonance imaging (MRI) was proposed in the differential diagnosis of solid brain tumors, showing higher accuracy than MRI evaluation of the enhancing part of the tumor. In particular, MRI assessment of the NEPA was demonstrated to be a promising tool for distinguishing high-grade gliomas from primary lymphoma and brain metastases. Additionally, the MRI characteristics of the NEPA were found to correlate with prognosis and treatment response. The purpose of this narrative review was to describe MRI features of the NEPA obtained with conventional and advanced MRI techniques to better understand their potential in identifying the different characteristics of high-grade gliomas, primary lymphoma and brain metastases and in predicting clinical outcome and response to surgery and chemo-irradiation. Diffusion and perfusion techniques, such as diffusion tensor imaging (DTI), diffusional kurtosis imaging (DKI), dynamic susceptibility contrast-enhanced (DSC) perfusion imaging, dynamic contrast-enhanced (DCE) perfusion imaging, arterial spin labeling (ASL), spectroscopy and amide proton transfer (APT), were the advanced MRI procedures we reviewed.

Assessment of brain tumors by magnetic resonance dynamic susceptibility contrast perfusion-weighted imaging and computed tomography perfusion: a comparison study.

PURPOSE: To investigate the association and agreement between magnetic resonance dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) and computed tomography perfusion (CTP) in determining vascularity and permeability of primary and secondary brain tumors. MATERIAL AND METHODS: DSC-PWI and CTP studies from 97 patients with high-grade glioma, low-grade glioma and solitary brain metastasis were retrospectively reviewed. Normalized cerebral blood flow (nCBF), cerebral blood volume (nCBV), capillary transfer constant (nK2) and permeability surface area product (nPS) values were obtained. Variables among groups were compared, and correlation and agreement between DSC-PWI and CTP were tested. RESULTS: All DSC-PWI and CTP parameters were higher in high-grade than in low-grade gliomas (p < 0.01 and p < 0.001). Metastases had greater DSC-PWI nCBV (p < 0.05), nCTP-CBF (p < 0.05), nCTP-CBV (p < 0.01) and nCTP-PS (p < 0.0001) than low-grade gliomas and more elevated nCTP-PS (p < 0.01) than high-grade gliomas. The correlation was strong between DSC-PWI nCBF and CTP nCBF (r = 0.79; p < 0.00001) and between DSC-PWI nCBV and CTP nCBV (r = 0.83; p < 0.00001), weaker between DSC-PWI nK2 and CTP nPS (r = 0.29; p < 0.01). Bland-Altman plots indicated that the agreement was strong between DSC-PWI nCBF and CTP nCBF, good between DSC-PWI nCBV and CTP nCBV and poorer between DSC-PWI nK2 and CTP nPS. CONCLUSION: DSC-PWI and CTP CBF and CBV maps were comparable and interchangeable in the assessment of tumor vascularity, unlike DSC-PWI K2 and CTP PS maps that were more discordant in the analysis of tumor permeability. CTP could be an alternative method to quantify tumor neoangiogenesis when MRI is not available or when the patient does not tolerate it.

Tmax Volumes Predict Final Infarct Size and Functional Outcome in Ischemic Stroke Patients Receiving Endovascular Treatment.

OBJECTIVE: The objective of this paper was to explore the utility of time to maximum concentration (Tmax )-based target mismatch on computed tomography perfusion (CTP) in predicting radiological and clinical outcomes in patients with acute ischemic stroke (AIS) with anterior circulation large vessel occlusion (LVO) selected for endovascular treatment (EVT). METHODS: Patients with AIS underwent CTP within 24 hours from onset followed by EVT. Critically hypoperfused tissue and ischemic core volumes were automatically calculated using Tmax thresholds >9.5 seconds and >16 seconds, respectively. The difference between Tmax > 9.5 seconds and Tmax > 16 seconds volumes and the ratio between Tmax > 9.5 seconds and Tmax > 16 seconds volumes were considered ischemic penumbra and Tmax mismatch ratio, respectively. Final infarct volume (FIV) was measured on follow-up non-contrast computed tomography (CT) at 24 hours. Favorable clinical outcome was defined as 90-day modified Rankin Scale 0 to 2. Predictors of FIV and outcome were assessed with multivariable logistic regression. Optimal Tmax volumes for identification of good outcome was defined using receiver operating curves. RESULTS: A total of 393 patients were included, of whom 298 (75.8%) achieved successful recanalization and 258 (65.5%) achieved good outcome. In multivariable analyses, all Tmax parameters were independent predictors of FIV and outcome. Tmax  > 16 seconds volume had the strongest association with FIV (beta coefficient = 0.596 p <0.001) and good outcome (odds ratio [OR] = 0.96 per 1 ml increase, 95% confidence interval [CI] = 0.95-0.97, p < 0.001). Tmax  > 16 seconds volume had the highest discriminative ability for good outcome (area under the curve [AUC] = 0.88, 95% CI = 0.842-0.909). A Tmax  > 16 seconds volume of ≤67 ml best identified subjects with favorable outcome (sensitivity = 0.91 and specificity = 0.73). INTERPRETATION: Tmax target mismatch predicts radiological and clinical outcomes in patients with AIS with LVO receiving EVT within 24 hours from onset. ANN NEUROL 2022;91:878-888.

Delayed perihematomal hypoperfusion is associated with poor outcome in intracerebral haemorrhage.

BACKGROUND: The aim of this study was to characterize the temporal evolution and prognostic significance of perihematomal perfusion in acute intracerebral haemorrhage (ICH). METHODS: A single-centre prospective cohort of patients with primary spontaneous ICH receives computed tomography perfusion (CTP) within 6 h from onset (T0) and at 7 days (T7). Cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were measured in the manually outlined perihematomal low-density area. Poor functional prognosis (modified Rankin Scale 3-6) at 90 days was the outcome of interest, and predictors were explored with multivariable logistic regression. RESULTS: A total of 150 patients were studied, of whom 52 (34.7%) had a mRS 3-6 at 90 days. Perihematomal perfusion decreased from T0 to T7 in all patients, but the magnitude of CBF and CBV reduction was larger in patients with unfavourable outcome (median CBF change -7.8 vs. -6.0 ml/100 g/min, p < .001, and median CBV change -0.5 vs. -0.4 ml/100 g, p = .010, respectively). This finding remained significant after adjustment for confounders (odds ratio [OR] for 1 ml/100 g/min CBF reduction: 1.33, 95% confidence interval [CI] (1.15-1.55), p < .001; OR for 0.1 ml/100 g CBV reduction: 1.67, 95% CI 1.18-2.35, p = .004). The presence of CBF < 20 ml/100 g/min at T7 was then demonstrated as an independent predictor of poor functional outcome (adjusted OR: 2.45, 95% CI 1.08-5-54, p = .032). CONCLUSION: Perihaemorrhagic hypoperfusion becomes more severe in the days following acute ICH and is independently associated with poorer outcome. Understanding the underlying biological mechanisms responsible for delayed decrease in perihematomal perfusion is a necessary step towards outcome improvement in patients with ICH.

Association Between Perihematomal Perfusion and Intracerebral Hemorrhage Outcome.

BACKGROUND: The prognostic impact of perihematomal hypoperfusion in patients with acute intracerebral hemorrhage (ICH) remains unclear. We tested the hypothesis that perihematomal hypoperfusion predicts poor ICH outcome and explored whether hematoma growth (HG) is the pathophysiological mechanism behind this association. METHODS: A prospectively collected single-center cohort of consecutive ICH patients undergoing computed tomography perfusion on admission was analyzed. Cerebral blood flow (pCBF) was measured in the manually outlined perihematomal low-density area. pCBF was categorized into normal (40-55 mL/100 g/min), low (< 40 mL/100 g/min), and high (> 55 mL/100 g/min). HG was calculated as total volume increase from baseline to follow-up CT. A modified Rankin scale > 2 at three months was the outcome of interest. The association between cerebral perfusion and outcome was investigated with logistic regression, and potential mediators of this relationship were explored with mediation analysis. RESULTS: A total of 155 subjects were included, of whom 55 (35.5%) had poor outcome. The rates of normal pCBF, low pCBF, and high pCBF were 17.4%, 68.4%, and 14.2%, respectively. After adjustment for confounders and keeping subjects with normal pCBF as reference, the risk of poor outcome was increased in patients with pCBF < 40 mL/100 g/min (odds ratio 6.11, 95% confidence interval 1.09-34.35, p = 0.040). HG was inversely correlated with pCBF (R = -0.292, p < 0.001) and mediated part of the association between pCBF and outcome (proportion mediated: 82%, p = 0.014). CONCLUSION: Reduced pCBF is associated with poor ICH outcome in patients with mild-moderate severity. HG appears a plausible biological mediator but does not fully account for this association, and other mechanisms might be involved.

Comparison of perihematomal perfusion in deep and lobar intracerebral hemorrhage.

PURPOSE: Hypoperfusion in the perihematomal rim is common in acute intracerebral hemorrhage (ICH) but its determinants remain incompletely characterized. Despite known biological differences between deep and lobar ICH, the association between ICH location and cerebral perfusion has not been investigated. We tested the hypothesis that perihematomal perfusion differs between deep and lobar ICH. METHODS: Prospectively collected cohort of subjects with primary spontaneous ICH undergoing CT perfusion on admission. Cerebral blood flow (CBF), blood volume (CBV), and mean transit time (MTT) were measured in the manually outlined perihematomal low-density area. The association between perihematomal perfusion and ICH location was explored with multivariable linear regression. RESULTS: A total of 155 patients were enrolled (59 with a lobar bleeding). In univariate analysis, median perihematomal CBF and CBV were lower in lobar ICH compared with deep ICH (23.8 vs 33.4 mL/100 g/min, p = 0.001 and 1.7 vs 2.3 mL/100 g, p = 0.001, respectively). Lobar ICH location remained inversely associated with CBF (ß = - 0.17, p = 0.038) and CBV (ß = - 0.19, p = 0.023) after adjustment for confounders in linear regression. CONCLUSION: Lobar ICH location is inversely related with perihematomal CBF and CBV. Further studies are needed to confirm this association and define the underlying biological mechanisms.