Fluid-attenuated Inversion Recovery Signal Intensity Research Articles

Predicting glioblastoma recurrence using multiparametric MR imaging of non-enhancing peritumoral regions at baseline

BackgroundTo assess the feasibility of multiparametric magnetic resonance imaging in predicting tumor recurrence in nonenhancing peritumoral regions in patients with glioblastoma at baseline. MethodsFifty-eight patients with recurrent glioblastoma underwent multiparametric magnetic resonance imaging, including T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging. Nonenhancing peritumoral regions with glioblastoma recurrence were identified by coregistering preoperative and post-recurrent magnetic resonance images. Regions of interest were placed in nonenhancing peritumoral regions with and without tumor recurrence to calculate the apparent diffusion coefficient value, and relative ratios of T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and cerebral blood volume values. ResultsSignificant lower relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative apparent diffusion coefficient but higher relative cerebral blood volume values were found in the nonenhancing peritumoral regions with tumor recurrence than without recurrence (all P < 0.05). The threshold values ≥ 0.89 for relative cerebral blood volume provide the optimal performance for predicting the nonenhancing peritumoral regions with future tumor recurrence, with the sensitivity, specificity, and accuracy of 84.7%, 83.6%, and 85.8%, respectively. The combination of relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative cerebral blood volume can provide better predictive performance than relative cerebral blood volume (P = 0.015). ConclusionThe combined use of T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging can effectively estimate the risk of future tumor recurrence at baseline.

Subtle white matter intensity changes on fluid-attenuated inversion recovery imaging in patients with ischaemic stroke.

Leukoaraiosis is a neuroimaging marker of small-vessel disease that is characterized by high signal intensity on fluid-attenuated inversion recovery MRI. There is increasing evidence from pathology and neuroimaging suggesting that the structural abnormalities that characterize leukoaraiosis are actually present within regions of normal-appearing white matter, and that the underlying pathophysiology of white matter damage related to small-vessel disease involves blood-brain barrier damage. In this study, we aim to verify whether leukoaraiosis is associated with elevated signal intensity on fluid-attenuated inversion recovery imaging, a marker of brain tissue free-water accumulation, in normal-appearing white matter. We performed a cross-sectional study of adult patients admitted to our hospital with a diagnosis of acute ischaemic stroke or transient ischaemic attack. Leukoaraiosis was segmented using a semi-automated method involving manual outlining and signal thresholding. White matter regions were segmented based on the probabilistic tissue maps from the International Consortium for Brain Mapping 152 atlas. Also, normal-appearing white matter was further segmented based on voxel distance from leukoaraiosis borders, resulting in five normal-appearing white matter strata at increasing voxel distances from leukoaraiosis. The relationship between mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter and leukoaraiosis volume was studied in a multivariable statistical analysis using linear mixed modelling, having normal-appearing white matter strata as a clustering variable. One hundred consecutive patients meeting inclusion and exclusion criteria were selected for analysis (53% female, mean age 68 years). Mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter was higher in the vicinity of leukoaraiosis and progressively lower at increasing distances from leukoaraiosis. In a multivariable analysis, the mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter was positively associated with leukoaraiosis volume and age (B = 0.025 for each leukoaraiosis quartile increase; 95% confidence interval 0.019-0.030). This association was found similarly across normal-appearing white matter strata. Voxel maps of the mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter showed an increase in signal intensity that was not adjacent to leukoaraiosis regions. Our results show that normal-appearing white matter exhibits subtle signal intensity changes on fluid-attenuated inversion recovery imaging that are related to leukoaraiosis burden. These results suggest that diffuse free-water accumulation is likely related to the aetiopathogenic processes underlying the development of white matter damage related to small-vessel disease.

Abstract 89: Portable, Low-Field Magnetic Resonance Imaging: Determining Mismatch Following Acute Ischemic Stroke

Background and Aims: Treatment options for acute ischemic stroke (AIS) are uniquely dependent on the time of stroke onset. Intravenous thrombolysis must be administered within 4.5 hours of symptoms commencing, yet a subset of patients wake-up with symptoms and time of onset is unknown. Mismatch between fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) MRI can be used to qualify wake-up strokes for thrombolysis. This has been shown to lead to improved functional outcomes in multicenter trials (WAKE-UP, MR-WITNESS). However, access to MRI is a barrier to differential diagnosis and subsequent treatment. Recent advances in portable, low-field MRI (LF-MRI) offer a solution to increase access to MRI technologies and circumvent the limitations of conventional systems. As such, in this pilot study, we sought to establish the utility of portable LF-MRI to identify DWI-FLAIR mismatch following AIS. Methods: Patients with a diagnosis of AIS presenting to Emergency Department or Intensive Care Unit of the Yale New Haven Hospital or Massachusetts General Hospital from January 2020 to June 2023 underwent DWI and FLAIR acquisition on a 0.064T MRI (Hyperfine Research Inc.) at &lt;4.5 hours ( n =7), 4.5-6 hours ( n =7), and 6-48 hours ( n =110) since last known well (LKW). Conventional high-field (HF) MR images were acquired within 72 hours of LF-MRI. HF-DWI images were co-registered to LF-FLAIR and the hyperintense DWI stroke lesion segmented and superimposed on the FLAIR. The segmentation was mirrored to the contralateral hemisphere of the LF-FLAIR to establish a FLAIR signal intensity ratio (SIR). Results: The FLAIR SIR on images &lt;4.5 hours since LKW was 0.98±0.08. The SIR for cases 4.5-6 hours was 1.34±0.33. Cases 6-48 hours produced a SIR of 1.56±0.36. The SIR at &lt;4.5 hours was significantly less than that observed &gt;6 hours since LKW ( p =0.03). Conclusion: This pilot study demonstrates that a 0.064T portable MRI is capable of distinguishing hyperacute stroke from later stroke onset using FLAIR SIR. Future research is needed in a larger cohort to determine if this imaging technology can be used to guide thrombolysis in the setting of wake-up stroke.

The effects of normobaric and hyperbaric oxygenation on MRI signal intensities in T1 -weighted, T2 -weighted and FLAIR images in human brain.

Dissolved oxygen has known paramagnetic effects in magnetic resonance imaging (MRI). The aim of this study was to compare the effects of normobaric oxygenation (NBO) and hyperbaric oxygenation (HBO) on human brain MRI signal intensities. Baseline brain MRI was performed in 17 healthy subjects (mean age 27.8 ± 3.2). MRI was repeated after exposure to the NBO and HBO at different time points (0 min, 25 min, 50 min). Signal intensities in T 1-weighted, T 2-weighted images and fluid attenuated inversion recovery (FLAIR) signal intensities of several intracranial structures were compared between NBO and HBO. Increased T 1-weighted signal intensities were observed in white and deep grey brain matter, cerebrospinal fluid (CSF), venous blood and vitreous body after exposure to NBO as well as to HBO compared to baseline (Dunnett's test, p < 0.05) without significant differences between both protocols. There was also no significant difference in T 2-weighted signal intensities between NBO and HBO. FLAIR signal intensities were increased only in the vitreous body after NBO and HBO and FLAIR signal of caudate nucleus was decreased after NBO (Dunnett's test, p < 0.05). The statistically significant differences in FLAIR signal intensities were found between NBO and HBO (paired t-test, p < 0.05) in most observed brain structures (paired t-test, p < 0.05). Our results show that NBO and HBO alters signal intensities T 1-weighted and FLAIR images of human brain. The differences between NBO and HBO are most pronounced in FLAIR imaging.

Abstract TP194: The FLAIR Signal Intensity Ratio Predicts Early Neurologic Deterioration For Small Subcortical Infarcts

Introduction: Early neurologic deterioration (END) occurs in nearly 40% of small subcortical infarct (SSI), with the majority occurring as a byproduct of completion of the initial infarct leading to significant morbidity. Presently there is not a robust predictive radiographic biomarker for END from SSI. The fluid-attenuated inversion recovery signal intensity ratio (FLAIR-SIR) ≥ 1.15 was shown to aid in differentiation of completed infarcts from those with penumbra allowing in identifying those that may benefit from alteplase. We aimed to use the FLAIR-SIR as a biomarker for predicting END from SSI. We hypothesized that those with a higher FLAIR-SIR had less risk of developing END due to completion of infarct. Methods: We retrospectively enrolled individuals who were seen at the Rhode Island Hospital between 2019 and 2022. Those included had a radiographic diagnosis of a SSI per STRIVE criteria. The primary outcome was END diagnosed as ≥ 2-point increase in NIH Stroke Scale score within 24 hours of admission. The primary exposure was FLAIR-SIR, defined as the ratio of ipsilateral FLAIR intensity within the region of infarct divided by the FLAIR of the contralateral identical anatomical location. Standard descriptive and unadjusted regression analyses were used. Results: A total of 195 individuals were included with a mean age 68 (± 13) years, and 59.5% (116/195) being male. END was identified in 3.6% (7/195). The mean overall FLAIR-SIR was 1.26 (± 0.30) with a mean of 1.26 (± 0.34) for those without END and 1.07 (± 0.25) for those with END ( p = 0.66). Using Youden’s J index for FLAIR-SIR, the optimal cutoff was determined to be ≤ 1.15. For a FLAIR-SIR ≤ 1.15, unadjusted Cox regression finds a hazard ratio of 4.1 (95%CI 0.79 - 21.1, p = 0.092) for END within 24 hours. Conclusions: FLAIR-SIR measurement above 1.15 may serve as a radiographic predictor of less risk of END amongst SSI. Our findings corroborate prior studies identifying 1.15 as a threshold for at-risk and completed SSI and should receive thrombolytics to minimize risk of END. Future studies are needed to increase power and confirm our findings.

MRI evidence of olfactory system alterations in patients with COVID-19 and neurological symptoms.

Despite olfactory disorders being among the most common neurological complications of coronavirus disease 2019 (COVID-19), their pathogenesis has not been fully elucidated yet. Brain MR imaging is a consolidated method for evaluating olfactory system's morphological modification, but a few quantitative studies have been published so far. The aim of the study was to provide MRI evidence of olfactory system alterations in patients with COVID-19 and neurological symptoms, including olfactory dysfunction. 196 COVID-19 patients (median age: 53years, 56% females) and 39 controls (median age 55years, 49% females) were included in this cross-sectional observational study; 78 of the patients reported olfactory loss as the only neurological symptom. MRI processing was performed by ad-hoc semi-automatic processing procedures. Olfactory bulb (OB) volume was measured on T2-weighted MRI based on manual tracing and normalized to the brain volume. Olfactory tract (OT) median signal intensity was quantified on fluid attenuated inversion recovery (FLAIR) sequences, after preliminary intensity normalization. COVID-19 patients showed significantly lower left, right and total OB volumes than controls (p < 0.05). Age-related OB atrophy was found in the control but not in the patient population. No significant difference was found between patients with olfactory disorders and other neurological symptoms. Several outliers with abnormally high OT FLAIR signal intensity were found in the patient group. Brain MRI findings demonstrated OB damage in COVID-19 patients with neurological complications. Future longitudinal studies are needed to clarify the transient or permanent nature of OB atrophy in COVID-19 pathology.

In Mild and Moderate Acute Ischemic Stroke, Increased Lipid Peroxidation and Lowered Antioxidant Defenses Are Strongly Associated with Disabilities and Final Stroke Core Volume.

In acute ischemic stroke (AIS), there are no data on whether oxidative stress biomarkers have effects above and beyond known risk factors and measurements of stroke volume. This study was conducted in 122 mild-moderate AIS patients and 40 controls and assessed the modified ranking scale (mRS) at baseline, and 3 and 6 months later. We measured lipid hydroperoxides (LOOH), malondialdehyde (MDA), advanced oxidation protein products, paraoxonase 1 (PON1) activities and PON1 Q192R genotypes, high density lipoprotein cholesterol (HDL), sulfhydryl (-SH) groups), and diffusion-weighted imaging (DWI) stroke volume and fluid-attenuated inversion recovery (FLAIR) signal intensity. We found that (a) AIS is characterized by lower chloromethyl acetate CMPAase PON1 activity, HDL and -SH groups and increased LOOH and neurotoxicity (a composite of LOOH, inflammatory markers and glycated hemoglobin); (b) oxidative and antioxidant biomarkers strongly and independently predict mRS scores 3 and 6 months later, DWI stroke volume and FLAIR signal intensity; and (c) the PON1 Q192R variant has multiple effects on stroke outcomes that are mediated by its effects on antioxidant defenses and lipid peroxidation. Lipid peroxidation and lowered -SH and PON1-HDL activity are drug targets to prevent AIS and consequent neurodegenerative processes and increased oxidative reperfusion mediators due to ischemia-reperfusion injury.

Voxel-Based Morphometric MRI Postprocessing-Assisted Laser Interstitial Thermal Therapy for Focal Cortical Dysplasia-Suspected Lesions: Technique and Outcomes.

MRI-guided laser interstitial thermal therapy (MRgLITT) is a novel treatment modality for focal cortical dysplasia (FCD). However, identifying the location and extent of subtle FCD by visual analysis during MRgLITT remains challenging. To introduce voxel-based morphometric MRI postprocessing into the procedure of MRgLITT for FCD-suspected lesions and assess the complementary value of the MRI postprocessing technique for the trajectory design and thermal parameter setting of MRgLITT. Junction and normalized fluid-attenuated inversion recovery signal intensity images were used to detect the gray-white matter junction blurring and cortical fluid-attenuated inversion recovery hyperintensity, respectively. According to the 2 postprocessing images, the region of interest (ROI) for ablation was drawn. The main principle of presurgical planning is that the trajectory of the laser fiber was designed as far as possible along the long axis of the ROI while the extent of planned ablation covered the entire ROI. The subsequent intraoperative procedure was performed under the guidance of the presurgical plan. Nine patients with epilepsy with FCD-suspected lesions underwent MRgLITT with the assistance of MRI postprocessing images. Among them, 4 patients were junction positive, 2 patients were normalized fluid-attenuated inversion recovery signal intensity positive, and the remaining 3 patients were positive for both. Postsurgical MRI demonstrated that the ROIs were ablated entirely in 7 patients. Engel Ia, Ib, and IV scores were obtained at 1-year follow-up for 6, 1, and 2 patients, respectively. MRI postprocessing provides complementary information for designing the laser fiber trajectory and subsequent ablation for FCDs.

Discrimination between glioblastoma and solitary brain metastasis: a quantitative analysis based on FLAIR signal intensity.

This study determined the diagnostic performance of fluid-attenuated inversion recovery (FLAIR) signal intensity (SI) in discriminating between glioblastoma (GBM) and solitary brain metastasis (SBM). We recruited 40 patients with a histologically confirmed diagnosis of GBM or SBM who underwent conventional 3 Tesla magnetic resonance imaging before surgery or biopsy between August 2020 and January 2022. Three regions of interest were placed to assess FLAIR SI: the enhancing region (eFLAIR), the peritumoral region (pFLAIR), and the contralateral normal white matter (nFLAIR). The diagnostic performance of significantly different parameters between the two tumor entities was analyzed by receiver operating characteristic (ROC) curve analysis. The pFLAIR SI was significantly lower in GBM than in SBM (p < 0.05). The eFLAIR SI and the SI ratio eFLAIR and nFLAIR (e/nFLAIR) were significantly higher in GBM than in SBM (p < 0.05). On ROC curve analysis, the e/nFLAIR ratio provided the highest area under the curve value of 81%, with a sensitivity of 80.8% and a specificity of 85.7%, for distinguishing between the two tumor types. The eFLAIR, pFLAIR, and e/nFLAIR parameters are useful for differentiating between GBM and SBM.

Diffusion-Weighted Imaging and Fluid-Attenuated Inversion Recovery Quantification to Predict Diffusion-Weighted Imaging-Fluid-Attenuated Inversion Recovery Mismatch Status in Ischemic Stroke With Unknown Onset.

Visual rating of diffusion-weighted imaging (DWI)-fluid-attenuated inversion recovery (FLAIR) mismatch can be challenging. We evaluated quantification of DWI and FLAIR to predict DWI-FLAIR mismatch status in ischemic stroke. In screened patients from the WAKE-UP trial (Efficacy and Safety of Magnetic Resonance Imaging-Based Thrombolysis in Wake-Up Stroke), we retrospectively studied relative DWI (rDWI SI) and FLAIR signal intensity (rFLAIR SI). We defined the optimal mean rFLAIR SI and interquartile range of the rDWI SI in the DWI lesion to predict DWI-FLAIR mismatch status. We investigated agreement between each quantitative parameter and the DWI-FLAIR mismatch and the association between both quantitative parameters. We evaluated the predictive value of the quantitative parameters for excellent functional outcome by logistic regression, adjusted for DWI lesion volume, treatment, age, and National Institutes of Health Stroke Scale score. In the rFLAIR and rDWI SI analysis, 213/369 and 241/421 subjects respectively had a DWI-FLAIR mismatch. A mean rFLAIR SI cutoff of 1.09 and interquartile range rDWI SI cutoff of 0.47 were optimal to predict the DWI-FLAIR mismatch with a sensitivity and specificity of 77% (95% CI, 71%-83%) and 67% (95% CI, 59%-74%), and 76% (95% CI, 70%-81%) and 72% (95% CI, 65%-79%), respectively. For both quantitative parameters, agreement with the DWI-FLAIR mismatch was fair (73%, κ=0.44 [95% CI, 0.35-0.54] for rFLAIR and 74%, κ=0.48 [95% CI, 0.39-0.56] for rDWI). Both quantitative parameters correlated moderately (Pearson R=0.54 [95% CI, 0.46-0.61]; P<0.001, n=367). The interquartile range rDWI SI (n=188), but not the mean rFLAIR SI (n=172), was an independent predictor of excellent functional outcome (odds ratio, 0.67 per 0.1 unit increase of interquartile range rDWI SI, 95% CI, 0.51-0.89, P=0.01). Agreement between the quantitative and qualitative approach may be insufficient to advocate DWI or FLAIR quantification as alternative for visual rating.

Reversible Edema in the Penumbra Correlates With Severity of Hypoperfusion.

We aimed to investigate fluid-attenuated inversion recovery changes in the penumbra. We determined core and perfusion lesions in subjects from the WAKE-UP trial (Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke) and AXIS 2 trial (Granulocyte Colony-Stimulating Factor in Patients With Acute Ischemic Stroke) with perfusion- and diffusion-weighted imaging at baseline. Only subjects with a mismatch volume >15 mL and ratio >1.2 were included. We created voxel-based relative fluid-attenuated inversion recovery signal intensity (rFLAIR SI) maps at baseline and follow-up. We studied rFLAIR SI in 2 regions of interest: baseline penumbra (baseline perfusion lesion−[core lesion+voxels with apparent diffusion coefficient <620 10−6 mm2/s]) and noninfarcted penumbra (baseline perfusion lesion−follow-up fluid-attenuated inversion recovery lesion) at 24 hours (WAKE-UP) or 30 days (AXIS 2). We analyzed the association between rFLAIR SI and severity of hypoperfusion, defined as time to maximum of the residue function. In the baseline penumbra, rFLAIR SI was elevated (ratio, 1.04; P=1.7×10−13; n=126) and correlated with severity of hypoperfusion (Pearson r, 0.03; P<1.0×10−4; n=126). In WAKE-UP, imaging at 24 hours revealed a further increase of rFLAIR SI in the noninfarcted penumbra (ratio, 1.05 at 24 hours versus 1.03 at baseline; P=7.1×10−3; n=43). In AXIS 2, imaging at 30 days identified reversibility of the rFLAIR SI (ratio, 1.02 at 30 days versus 1.04 at baseline; P=1.5×10−3; n=26) since it was no longer different from 1 (ratio, 1.01 at 30 days; P=0.099; n=26). Penumbral rFLAIR SI increases appear early after stroke onset, correlate with severity of hypoperfusion, further increase at 24 hours, and are reversible by 30 days. URL: https://clinicaltrials.gov; Unique identifier: NCT01525290. URL: https://clinicaltrials.gov; Unique identifier: NCT00927836.

Abstract P352: Reversible Relative FLAIR Signal Intensity Changes in the Penumbra Correlate With Severity of Hypoperfusion

In ischemic stroke, the study of edema, measurable as fluid attenuated inversion recovery (FLAIR) signal increase, has mainly focused on the ischemic core and less on the surrounding penumbra. To the naked eye, no FLAIR changes are present in the penumbra. However, changes in perfusion status could induce physiological changes resulting in subtle penumbral FLAIR signal alterations. To investigate penumbral FLAIR changes, we included subjects from the Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke (WAKE-UP) and Granulocyte Colony-Stimulating Factor in Patients With Acute Ischemic Stroke (AXIS 2) trial with perfusion- and diffusion-weighted imaging (PWI, DWI) and FLAIR at baseline. We used RAPID software to calculate the core and perfusion lesion on DWI and PWI and selected subjects with a minimal mismatch volume (15 ml) and ratio (1.2). We created voxel-based relative FLAIR signal intensity (rFLAIR SI) maps at baseline and follow up (FU) by calculating the ratio of the FLAIR intensity in one voxel and the median FLAIR intensity in a sphere with 15 mm radius around a contralateral homologues voxel. We studied rFLAIR SI in two regions of interest: the baseline penumbra (baseline perfusion lesion - [core lesion + voxels with apparent diffusion coefficient &lt;620 10 -6 mm 2 /s]) and the non-infarcted penumbra (baseline perfusion lesion - FU FLAIR lesion) at 24 hours (WAKE-UP) or 30 days (AXIS 2). Severity of hypoperfusion was defined as the time to maximum of the residue function. In the baseline penumbra, rFLAIR SI was elevated (ratio=1.04, p=1.7*10 -13 , n=126) and correlated with severity of hypoperfusion (Pearson’s r 0.03, p&lt;1.0*10 -4 , n=126). At 24 hours in a subgroup from WAKE-UP, rFLAIR SI in the non-infarcted penumbra further increased (ratio=1.05 at 24h vs 1.03 at baseline, p=7.1*10 -3 , n=43). In a different subgroup from AXIS 2, this increase in rFLAIR SI was reversible (ratio=1.02 at 30d vs 1.04 at baseline, p=1.5*10 -3 n=26) since it was no longer different from 1 at 30 days (ratio=1.01 at 30 days, p=0.099, n=26). Increases in rFLAIR SI, likely representing edema, are not restricted to the ischemic core and correlate with severity of hypoperfusion in the penumbra. They appear early after stroke onset, further increase at 24 hours and are reversible by 30 days.

The Feasibility of Magnetic Resonance Imaging for the Differentiation of Cerebrospinal Fluid Leak From Middle Ear Effusion: A Quantitative Analysis.

Assess quantitatively whether magnetic resonance imaging (MRI) signal intensity can be used to distinguish cerebrospinal fluid (CSF) leaks in the temporal bone from middle ear effusions. Retrospective case review. Tertiary referral center. Forty-nine patients, 18 with middle ear effusions (MEE), 30 with CSF leaks, and 1 with an MEE on one side and a CSF leak on the other, were evaluated in the study. Primary inclusion criteria for CSF leak patients were operative management of CSF leak with confirmatory diagnosis in follow-up. Primary inclusion criteria for MEE patients were electronic medical record documentation of an effusion with subsequent resolution on follow-up. For all patients, inclusion criteria included MRI imaging with 3D-T2 weighted sequences (3DT2) and fluid-attenuated inversion recovery (FLAIR) sequences performed within 1 year of diagnosis code entry. Computational analysis of signal intensity of fluid collections in MRI imaging. Sensitivity and specificity of 3DT2 and FLAIR signal intensity in the detection of CSF leak. For 3DT2 sequences with a chosen normalized signal intensity threshold (CSF leak if ≥ 0.5), sensitivity was 100% (95% CI: 86.3-100) and specificity was 83.3% (95% CI: 51.6-97.9). For FLAIR sequences with a threshold of 1.0 (CSF leak if < 1.0), sensitivity was 77.4% (95% CI: 58.9-90.4) and specificity was 85.7% (95% CI: 63.6-97.0). For a combined test in which a fluid collection was considered CSF if both 3DT2 ≥ 0.5 and FLAIR < 1.0, sensitivity was 76% (95% CI: 54.9-90.6) and specificity was 100% (95% CI: 73.5-100).

FLAIR-Wise Machine-Learning Classification and Lateralization of MRI-Negative 18F-FDG PET-Positive Temporal Lobe Epilepsy.

Objective: In this study, we investigated the ability of fluid-attenuated inversion recovery (FLAIR) data coupled with machine-leaning algorithms to differentiate normal and epileptic brains and identify the laterality of focus side in temporal lobe epilepsy (TLE) patients with visually negative MRI.Materials and Methods: The MRI data were acquired on a 3-T MR system (Philips Medical Systems). After pre-proceeding stage, the FLAIR signal intensities were extracted from specific regions of interest, such as the amygdala, cerebral white matter, inferior temporal gyrus, middle temporal gyrus, parahippocampal gyrus, superior temporal gyrus, and temporal pole, and fed into a classification framework followed by a support vector machine as classifier. The proposed lateralization framework was assessed in a group of MRI-negative unilateral TLE patients (N = 42; 23 left TLE and 19 right TLE) and 34 healthy controls (HCs) based on a leave-one-out cross-validation strategy.Results: Using the FLAIR data, we obtained a 75% accuracy for discriminating the three groups, as well as 87.71, 83.01, and 76.19% accuracies for HC/right TLE, HC/left TLE, and left TLE/right TLE tasks, respectively.Interpretation: The experimental results show that FLAIR data can potentially be considered an informative biomarker for improving the pre-surgical diagnostic confidence in patients with MRI-negative TLE.

Increasing FLAIR signal intensity in the postoperative cavity predicts progression in gross-total resected high-grade gliomas.

To evaluate the prognostic value of fluid-attenuated inversion recovery (FLAIR) signal intensity of postoperative cavity on progression free survival (PFS) and overall survival (OS) in patients with high-grade gliomas (HGG). This study retrospectively enrolled 45 consecutive HGG patients. These patients had chemoradiotherapy after gross-total resection of tumors. Quantitative analysis of the FLAIR signal intensity in postoperative cavity and background was made. We evaluated the threshold value, accuracy, sensitivity, specificity, and survival state with this technique. The patients who progressed and patients who did not progress were 33 and 12 cases separately. The ratio of postoperative cavity and background (C-B) on FLAIR sequence in patients who progressed was higher than that of patients who did not progress (P = 0.014). The PFS of the patients who progressed was shorter than that of patients who did not progress (P = 0.008). The area under ROC curve, threshold, sensitivity, specificity of C-B ratio for predicting tumor progression were 0.875, 62.3, 69.7, 0.84, and 0.50% respectively. The PFS of lower signal group was much longer than that of higher signal group (P = 0.004). The OS of the patients with higher signal was shorter than that of patients with lower signal (P = 0.034). The increase of gray value of FLAIR in postoperative cavity may be used as an imaging marker for predicting tumor progression.

Differences in signal intensities of temporomandibular joint (TMJ) effusion on fluid-attenuated inversion recovery (FLAIR) images.

Joint effusion is demonstrated by high signal intensity in the upper and lower temporomandibular joint (TMJ) spaces on T2-weighted images. The fluid-attenuated inversion recovery (FLAIR) technique can be applied to analyze joint effusion in the TMJ. FLAIR signal intensity can be more sensitively influenced by the contents of joint effusion than T2-weighted signal intensity. The purpose of this study was to analyze the signal intensity of joint effusion on FLAIR images and to investigate the changes in joint effusion contents according to the status of TMJ disorders. A total of 48 joints (45 patients) with joint effusion were investigated by magnetic resonance (MR) imaging. Regions of interest were placed over the joint effusion and gray matter on FLAIR images. The joints were categorized as normal disk position (NL), disk displacement with reduction (DWR), disk displacement without reduction (DWOR), and osteoarthritis (OA). The signal intensity ratio of joint effusion was calculated using gray matter as the reference point. The Kruskal-Wallis test and Steel test were applied. A probability of less than 0.05 was considered statistically significant. The median signal intensity ratios of joint effusion differed significantly among the four joint categories (p = 0.02, Kruskal-Wallis test). The median signal intensity ratio of joint effusion in the OA category was significantly higher than that in the NL category (p = 0.04, Steel test). The present findings suggest that FLAIR images can demonstrate the changes in joint effusion contents according to the status of TMJ disorders.

Fluid-Attenuated Inversion Recovery Signal Intensity as a Predictor of Gadolinium Enhancement in Relapsing-Remitting Multiple Sclerosis.

Magnetic resonance imaging (MRI) is used to diagnose and monitor disease activity in relapsing-remitting multiple sclerosis (RRMS). The objective of this study was to explore the association of "ultrabright" axial fluid-attenuated inversion recovery (FLAIR) lesions with gadolinium enhancement in patients with RRMS using qualitative and quantitative approaches. MRIs from patients with RRMS from 2010 to 2015 were reviewed. Two radiologists independently identified ultrabright lesions on axial FLAIR sequences. The contrast-to-noise ratio (CNR) was measured for ultrabright and control lesions. Of 301 lesions included in the study, 77 (26%) were identified by both radiologists as ultrabright. Interrater agreement was moderate (κ = 0.77, P < .001). Lesions identified by both radiologists as ultrabright demonstrated an association with gadolinium enhancement (χ21 = 30.8, P < .001) but were not associated with MRI magnet strength (χ21 = 0.24, P = .65). Higher CNR values were associated with gadolinium enhancement for 1.5-T studies (OR, 1.05; 95% CI, 1.02-1.07; P = .001) and 3-T studies (OR, 1.02; 95% CI, 1.02-1.03; P < .001). Diagnostic accuracy of the quantitative model was good for 1.5-T studies (area under the curve, 0.79; 95% CI, 0.68-0.9; P < .001) and 3-T studies (area under the curve, 0.78; 95% CI, 0.73-0.84; P < .001). Positive predictive value of 100% was obtained for CNR values of 92 for 1.5-T and 184 for 3-T studies. Qualitatively and quantitatively identified ultrabright axial FLAIR lesions are significantly associated with gadolinium enhancement.

Fluid-Attenuated Inversion Recovery (FLAIR) Signal Intensity Can Identify Stroke Within 6 and 8 Hours

Patients with wake-up or unknown time of onset stroke are usually excluded from recanalization. However, a few studies indicate that some magnetic resonance sequences can help predict time from symptom onset (SxO). Our goal was to assess the value of fluid-attenuated inversion recovery (FLAIR) signal intensity ratio (SIR) in identifying patients within 6 and 8 hours of stroke onset. We studied consecutive acute stroke patients with known time of onset who underwent magnetic resonance imaging (MRI) within 48 hours of SxO. SIR was calculated as the value of the FLAIR signal intensity of the identified area of infarction divided by the signal intensity in the homologous contralateral side of the brain. Out of 160 patients included in this study, 72 and 80 patients had MRI within 6 and 8 hours of SxO, respectively. We found a positive correlation between SIR and time from SxO (Pearson coefficient, .63). Receiver operating characteristic curves indicated that SIR ≤ 1.18 could accurately identify patients within 6 hours of SxO (86% sensitivity, 79% specificity) and a SIR ≤ 1.20 can be identified within 8 hours (89% sensitivity, 76% specificity). Among patients with no visible FLAIR hyperintensity, 83% (95% CI, 77%-89%) were within the 6-hour window. Quantitative assessment of FLAIR sequence can be used to identify patients within 6 and 8 hours of stroke onset.

Evaluation of lateral pterygoid muscles in painful temporomandibular joints by signal intensity on fluid-attenuated inversion recovery images.

Pathological changes of the lateral pterygoid muscle (LPM) have been investigated using various modalities, including magnetic resonance (MR) imaging and electromyography. Fluid-attenuated inversion recovery (FLAIR) is an MR sequence that we hypothesized can be used to evaluate abnormalities of the LPM. The purpose of this study was to analyze the FLAIR signal intensity of the LPM in painful temporomandibular joints (TMJs) and investigate the pathological changes of the muscle. The study was based on 149 TMJs of 77 patients who were referred for MR imaging of the TMJ. Patients rated their degree of pain during chewing and mouth opening using a visual analog scale (VAS). Regions of interest were placed over the superior and inferior heads of the LPM and gray matter on FLAIR sagittal images. Using the signal intensity of gray matter as a reference, the signal intensity ratio (SIR) of the LPM was calculated. Spearman's rank-correlation coefficient was used to analyze the correlation between the SIR and the VAS score (p < 0.05). A significant correlation was present between the SIR on FLAIR images and the VAS score. These results suggest that the FLAIR signal intensity of the superior and inferior heads of the LPM significantly increases as TMJ pain becomes more severe. Thus, FLAIR could be useful in assessing the relationship between the MR signals of the LPM and clinical symptoms.

Relative FLAIR Signal Intensities over Time in Acute Ischemic Stroke: Comparison of Two Methods

Visibility of lesions on fluid attenuated inversion recovery (FLAIR) images appears indicative of the time window in acute ischemic stroke. We compared two published methods for calculation of relative FLAIR signal intensities (rSI) regarding their association with time from symptom onset in a longitudinal fashion. We prospectively included patients receiving serial MRI examinations between 4.5 and 35 hours from symptom onset. FLAIR rSI was determined using two methods: a whole regions-of-interest (ROI) method and a hotspot method, selecting only a single area of visually highest signal. Signal intensity (rSI) was calculated relative to the contralateral side for each time point. We included 21 patients with 3-6 MRI examinations on the first 2 days after stroke onset. FLAIR rSI determined with both methods shows a linear association with time from onset, although the hotspot results showed higher variability. Both methods with their previously published thresholds are reliable for identifying patients outside the 4.5 hours time window. Both methods show a similar performance, and might be a suitable help for the visual assessment of FLAIR lesion visibility.