Fast Fluid-attenuated Inversion Recovery Research Articles

Yield of Fluid-Attenuated Inversion Recovery in Drug-Resistant Focal Epilepsy with Noninformative Conventional Magnetic Resonance Imaging

Purpose: To determine the role in presurgical assessment and evaluate the yield of fast fluid-attenuated inversion recovery (FLAIR) sequences for patients with intractable partial epilepsy for whom conventional magnetic resonance imaging (MRI) was normal. Material and Methods: Forty patients were selected. Conventional MRI including spin echo T₁-weighted sagittal images and fast spin echo T₂-weighted axial images was normal in 33 patients and showed noninformative lesions in 7. Fast FLAIR and T₂-weighted sequences were performed perpendicularly to the hippocampal long axis. Results: Additional abnormalities were found in 40%. They were correlated with electroclinical data in 13 patients (32.5%) and not correlated or doubtful in 3 (7.5%). Conclusion: Fast FLAIR sequences brought congruent additional information in 32.5% cases and seemed useful in presurgical evaluation.

Cerebral gliomas and metastases: assessment with contrast-enhanced fast fluid-attenuated inversion-recovery MR imaging.

The effect of contrast material on fast fluid-attenuated inversion-recovery (FLAIR) magnetic resonance images was evaluated for 16 patients with enhancing gliomas and 12 patients with cerebral metastases. Because of a marked T1 effect, fast FLAIR imaging provided a marked contrast enhancement, resulting in the highest tumor-to-background contrast ratio compared with standard imaging techniques.

Hyperacute Middle Cerebral Artery Territory Infarction: Comparison of Unenhanced CT, Spin-Echo T2-weighted,Fast FLAIR, and Diffusion-weighted MR Imaging

Purpose : To compare the detection rate of unenhanced CT, spin-echo T2-weighted, fast fluid-attenuatedin-version- recovery(FLAIR), and diffusion-weighted MR imaging in the diagnosis of hyperacute middle cerebralartery(MCA) territory infarction. Materials and Methods : Sixteen patients with clinically proven hyperacute MCAterritory infarction were e-valuated with unenhanced CT and MR. All CT examinations were performed within sixhours of the onset of symptoms and all MR studies were performed within two hours of CT. All images were evaluatedindepen-dently by two radiologists in possession of brief clinical information. Positive imaging criteria wereparenchy-mal hypoattenuation, as seen on CT, and increased signal intensity, as seen on MR. For quantitativeanalysis, we measured the attenuation and signal intensity of the lesion and contralateral normal parenchyma, andper-centage contrast-to-noise ratios(CNRs) of the lesions were also calculated . Results : Positive findings weredetected in all patients on diffusion-weighted images, in 13(81%) on CT, in 10 ( 63 %) on fast FLAIR images, andin 7(44 %) on T2-weighted images. Lesion percentage CNRs were 30% for diffusion-weighted imaging, 15 % for CT, 18% for FLAIR MR imaging, and 16 % for T2-weighted MR imag-ing(p

Subcallosal striations: early findings of multiple sclerosis on sagittal, thin-section, fast FLAIR MR images.

To determine how sensitive and specific the magnetic resonance (MR) imaging finding of subcallosal striations is for multiple sclerosis (MS). In 18 patients with clinically suspected MS and 32 age-matched patients without MS, sagittal 2-mm fast fluid-attenuated inversion-recovery (FLAIR) imaging was added to the routine MR studies of the brain. The images were reviewed for the presence of subcallosal striations, that is, linear, 1-mm-thick foci of hyperintensity perpendicular to the ependyma, like a stack of coins. The images were masked to exclude the hemispheric white matter and were interpreted without knowledge of patient age or medical history. Seventeen patients with clinical MS had subcallosal striations; one did not. Of the 32 patients without MS, five had subcallosal striations and 27 did not. Subcallosal striations were highly associated (P < .001) with clinical MS. Subcallosal striations are thought to represent perivenular demyelination, that is, the same process that later produces the "ovoid" lesions visible on routine MR images. Subcallosal striations are not seen on routine axial MR images and can be seen only on 2-mm sagittal FLAIR images.

MR imaging of the hippocampus: measurement of T2 with four dual-echo techniques.

To assess the effect of cerebrospinal fluid (CSF) signal nulling and different magnetic resonance (MR) imaging read-out implementations on the precision of T2 measurements in the hippocampus. Oblique coronal MR imaging was performed in 12 healthy volunteers by using four dual-echo MR sequences: conventional spin-echo (SE), fast SE, gradient-echo and SE (GRASE), and fast fluid-attenuated inversion-recovery (FLAIR) imaging. T2 measurements were obtained from T2 maps derived from regions of interest within the head of both hippocampi. T2 measurements obtained with the four MR sequences were compared, as were differences in T2 between right and left hippocampi. Interrater and test-retest consistency were determined. Fast FLAIR imaging provided the smallest normal range and SD of T2 measurements. Fast FLAIR and fast SE imaging provided the smallest coefficients of variation. GRASE imaging provided a lower coefficient of variation than that of conventional SE. The mean difference between left and right hippocampi was smallest at fast FLAIR imaging. Use of a CSF-nulling inversion prepulse, fast SE read-out, or GRASE read-out MR sequence helps improve the precision of the hippocampal T2 measurements in comparison with use of conventional SE imaging. T2 measurements obtained at dual-echo fast FLAIR imaging may help detect subtle hippocampal abnormalities.

3D fast flair: a CSF-nulled 3D fast spin-echo pulse sequence

Since its introduction, the fluid attenuated inversion recovery (FLAIR) sequence has found many applications in the central nervous system (CNS), because of its heavy T 2 weighting and excellent cerebrospinal fluid (CSF) suppression. More recently fast spin-echo based variants have been developed that greatly reduce scan time; such sequences are often referred to as “fast FLAIR.” We present what we believe to be the first implementation of FLAIR using a three dimensional (3D) fast spin-echo-based pulse sequence, which combines the cerebrospinal fluid suppression and good lesion contrast of two-dimensional fast FLAIR with the advantages of a three-dimensional sequence such as higher signal-to-noise ratio (SNR) per unit time, thinner slices (giving reduced partial volume effect) and the ability to reformat the data in an arbitrary plane.

Emergency Magnetic Resonance of the Brain

We will review the role of magnetic resonance (MR) in assessment of patients with acute neurological abnormalities. The major stumbling block to the use of MR in these patients is the belief that MR is insensitive to hyperacute (<12 h) intracranial hemorrhage and acute subarachnoid hemorrhage (SAH). Hyperacute hemorrhage has characteristic features on MR. Hematomas are iso-to hyperintense on T1-weighted and hyperintense on T2-weighted images. Gradient-echo scans that reveal characteristic peripheral hypointensity are critical to the detection and delineation of hyperacute hematomas. Use of fast fluid-attenuated inversion recovery (FLAIR) sequences has made it possible to detect SAH on MR with a sensitivity that is equal to or greater than computed tomography (CT). SAH produces dramatic hyperintensity in the normally hypointense cerebrospinal fluid on FLAIR. MR has proven useful in the detection of hypertensive encephalopathy and venous thrombosis. These entities can be difficult to diagnose on CT, and in both, early treatment can dramatically improve prognosis. The same is true for acute intracranial infections such as pyogenic abscess, subdural empyema, and herpes simplex encephalitis. MR improves diagnostic accuracy, resulting in more rapid institution of appropriate treatment and improved outcome.

Diffusion-weighted echo-planar MRI of lacunar infarcts.

We studied 35 patients with lacunar infarcts, using diffusion-weighted echo-planar imaging (DW-EPI) at 1.5 T. The relative apparent diffusion coefficient ratio (ADCR) of each lesion was calculated and lesion conspicuity on DW-EPI was compared to that on images acquired with fast fluid-attenuated inversion recovery and T2-weighted fast spin-echo sequences. Acute small infarcts (within 3 days) were identified with DW-EPI as an area of decreased ADCR (range 0.33-0.87; mean 0.67) and high signal, subacute small infarcts (4-30 days) as a high-signal or isointense areas of decreased or nearly normal ADCR (0.54-0.98; 0.73), and chronic small infarcts (> 30 days) as low- or high-signal areas of nearly normal or increased ADCR (0.97-1.92; 1.32). In three patients, small infarcts of the brain stem in the hyperacute phase (within 6 h) were seen only with DW-EPI. In five patients, fresh small infarcts adjacent to multiple old infarcts could be distinguished only with DW-EPI.

Fast fluid-attenuated inversion-recovery (FLAIR) MRI in the assessment of intraaxial brain tumors.

This study demonstrates the value of a fast fluid-attenuated inversion-recovery (FLAIR) technique in the assessment of primary intraaxial brain tumors. Twenty-one patients with primary intraaxial brain tumors were examined by T2-weighted, proton-density-weighted fast spin echo, fast FLAIR, and contrast-enhanced T1-weighted spin echo using identical slice parameters. The images were evaluated using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid (CSF) contrast and contrast-to-noise ratio (CNR). The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation, and image artifacts. In the qualitative evaluation, all readers found the fast FLAIR to be superior to fast spin echo in the exact delineation of intraaxial brain tumors (P < .001) and the delineation of enhancing and nonenhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF CNR (P < .001). The tumor-to-background contrast and tumor-to-background CNR of the fast FLAIR images were lower than those of T2-weighted spin-echo images but higher than those of proton-density-weighted spin-echo images. FLAIR images had more image artifacts influencing the image interpretation in only two patients. Signal hyperintensities at the ventricular border were present in 92% of the patients. They are common findings in fast FLAIR and should be included into the image interpretation.

An algorithm for automatic segmentation and classification of magnetic resonance brain images.

In this article, we describe the development and validation of an automatic algorithm to segment brain from extracranial tissues, and to classify intracranial tissues as cerebrospinal fluid (CSF), gray matter (GM), white matter (WM) or pathology. T1 weighted spin echo, dual echo fast spin echo (T2 weighted and proton density (PD) weighted images) and fast Fluid Attenuated Inversion Recovery (FLAIR) magnetic resonance (MR) images were acquired in 100 normal patients and 9 multiple sclerosis (MS) patients. One of the normal studies had synthesized MS-like lesions superimposed. This allowed precise measurement of the accuracy of the classification. The 9 MS patients were imaged twice in one week. The algorithm was applied to these data sets to measure reproducibility. The accuracy was measured based on the synthetic lesion images, where the true voxel class was known. Ninety-six percent of normal intradural tissue voxels (GM, WM, and CSF) were labeled correctly, and 94% of pathological tissues were labeled correctly. A low coefficient of variation (COV) was found (mean, 4.1%) for measurement of brain tissues and pathology when comparing MRI scans on the 9 patients. A totally automatic segmentation algorithm has been described which accurately and reproducibly segments and classifies intradural tissues based on both synthetic and actual images.

Automated Detection and Characterization of Multiple Sclerosis Lesions in Brain MR Images

In the present study an automatic algorithm for detection and contouring of multiple sclerosis (MS) lesions in brain magnetic resonance (MR) images is introduced. This algorithm automatically detects MS lesions in axial proton density, T 2-weighted, gadolinium enhanced, and fast fluid attenuated inversion recovery (FLAIR) brain MR images. Automated detection consists of three main stages: (1) detection and contouring of all hyperintense signal regions within the image; (2) partial elimination of false positive segments (defined herein as artifacts) by size, shape index, and anatomical location; (3) the use of an artificial neural paradigm (Back-Propagation) for final removal of artifacts by differentiating them from true MS lesions. The algorithm was applied to 45 images acquired from 14 MS patients. The algorithm’s sensitivity was 0.87 and the specificity 0.96. In 34 images, 100% of the lesions were detected. The algorithm potentially may serve as a useful preprocessing tool for quantitative MS monitoring via magnetic resonance imaging.

Asymptomatic spinal cord lesions in clinically isolated optic nerve, brain stem, and spinal cord syndromes suggestive of demyelination

OBJECTIVESConventional T2 weighted MRI studies have highlighted the fact that the presence of clinically silent brain lesions increases the risk of developing clinically definite multiple sclerosis after an isolated syndrome...

MRI lesion volume measurement in multiple sclerosis and its correlation with disability: a comparison of fast fluid attenuated inversion recovery (fFLAIR) and spin echo sequences

OBJECTIVESTo assess whether multiple sclerosis lesion volume measurements derived using the fast fluid attenuated inversion recovery (fFLAIR) sequence show better reproducibility or correlation with disability than those derived using the...

FLAIR AND HASTE IMAGING IN NEUROLOGIC DISEASES

The need to develop faster imaging techniques has led to the implementation of fast spin-echo imaging, EPI, and hybrid imaging techniques. This article discusses two of these faster imaging techniques, fast fluid-attenuated inversion-recovery (FLAIR) imaging and half-Fourier acquisition single-shot turbo spin-echo (HASTE) imaging, and their potential clinical application in neurologic diseases. FLAIR imaging, in particular, has demonstrated considerable promise for the evaluation of intracranial pathology. HASTE imaging can be used for rapid imaging of the brain or spine in those patients who are claustrophobic or who have difficulty remaining still, but it does not yet have a primary role in clinical neuroradiology.

35 Fast-FLAIR法におけるクロストーク効果について

35 Fast-FLAIR法におけるクロストーク効果について

37 高速FLAIR法のCSF flow artifact低減について : 180°inversion pulseの励起幅の検討

37 高速FLAIR法のCSF flow artifact低減について : 180°inversion pulseの励起幅の検討

高速FLAIR法のCSF flow artifact低減について : 180゜inversion pulseの励起幅の検討

高速FLAIR法のCSF flow artifact低減について : 180゜inversion pulseの励起幅の検討

Fluid-attenuated inversion recovery MR imaging: identification of protein concentration thresholds for CSF hyperintensity.

Using human volunteers and phantoms emulating CSF, we analyzed the effects of varying protein concentration on the signal intensity of saline solution. Also, for different fluid-attenuated inversion recovery (FLAIR) sequences, we compared protein concentration thresholds above which the signal from these solutions becomes hyperintense to that from brain parenchyma. Nine albumin solutions of varying concentrations (3.9 mg/dl to 2500 mg/dl) were imaged using fast FLAIR MR sequences (TR, 6000 msec: inversion time, 1730 msec: echo train length, 20) at different effective TEs (110, 150, 200, and 250 signal-to-noise ratios from the different albumin solutions versus albumin concentration were generated and correlated with average signal-to-noise ratios from brain parenchyma and CSF. We saw a gradual increase in signal-to-noise ratios from the albumin solutions as a function of albumin concentration. As the effective TE increased, the point of intersection between the plots and the average signal-to-noise ratio from brain parenchyma occurred at lower albumin concentrations. FLAIR MR imaging is potentially useful to evaluate pathologic conditions that increase CSF protein concentration. Using phantoms and healthy volunteers, we defined a protein concentration threshold above which the signal from saline solutions becomes hyperintense to that from brain parenchyma. This threshold depends on the effective TE used in the FLAIR sequence and is 250 mg/dl for an effective TE of 110 msec, 125 mg/dl for 150 msec. 110 mg/dl for 200 msec, and 95 mg/dl for 250 msec.

35 fast FLAIR法におけるクロストーク効果について(第25回秋季学術大会一般研究発表予稿集)

35 fast FLAIR法におけるクロストーク効果について(第25回秋季学術大会一般研究発表予稿集)

37 高速FLAIR法のCSF flow artifact低減について : 180°inversion pulseの励起幅の検討(第25回秋季学術大会一般研究発表予稿集)

37 高速FLAIR法のCSF flow artifact低減について : 180°inversion pulseの励起幅の検討(第25回秋季学術大会一般研究発表予稿集)