Fast Fluid-attenuated Inversion Recovery Sequences Research Articles

Diagnostic equivalency of fast T2 and FLAIR sequences for pediatric brain MRI: a pilot study.

Faster and motion robust magnetic resonance imaging (MRI) sequences are desirable in pediatric brain MRI as they can help reduce the need for monitored anesthesia care, which is a costly and limited resource that carries medical risks. To evaluate the diagnostic equivalency of commercially available accelerated motion robust MR sequences relative to standard sequences. This was an institutional review board-approved prospective study. Subjects underwent a clinical brain MRI using conventional multiplanar images at 3 Tesla followed by fast axial T2 and FLAIR (fluid-attenuated inversion recovery) sequences optimized for an approximately 50% reduction in acquisition time. Conventional and fast images from each subject were reviewed by two blinded pediatric neuroradiologists. The readers evaluated the presence of 12 findings. Intra-observer agreement was estimated for fast versus conventional sequences. For each set of sequences, interobserver agreement calculations and chi-square tests were used to evaluate differences between fast and conventional acquisitions. An independent third reader reviewed the intra-observer discrepancies and adjudicated them as being more conspicuous on fast sequence, conventional sequence or the equivalent. The readers also were asked to rate motion artifacts with a previously validated score. Images from 77 children (mean age: 11.3years) were analyzed. Intra-observer agreement (fast versus conventional) ranged between 89.2% and 92.3%. Interobserver agreement ranged between 86.1% and 88.4%. Interobserver agreement was significantly higher for conventional FLAIR relative to fast FLAIR for small (<5mm) foci of T2 in the white matter. Otherwise, interobserver agreement was not different between the fast and conventional sequences. For awake subjects, fast sequences had significantly fewer artifacts (P<0.05). Conventional T2 and FLAIR sequences can be optimized to shorten acquisition while maintaining diagnostic equivalency. These faster sequences were also less susceptible to motion artifacts.

Infarct morphology assessment in patients with carotid artery/middle cerebral artery occlusion using fast fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH).

We aim to evaluate the value of fast fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) in assessing infarct morphology in patients with symptomatic internal carotid artery (ICA) or middle cerebral artery (MCA) occlusions. Magnetic resonance (MR) diffusion-weighted imaging (DWI) FLAIR sequences, and carotid/cerebral magnetic resonance angiography of 102 patients with symptomatic ICA or MCA occlusions were evaluated. The location and score of FVH were determined using Olindo’s method; patients were classified as having Low or High FVHs based on FVH score, and either Distal or Proximal FVH based on FVH location. The differences between infarct morphologies were analyzed. FVH were detectable in 62 patients with High FVH and in 40 patients with Low FVHs based on the Olindo’s scale. There were no statistically significant differences in age, gender, hypertension, diabetes, hyperlipidemia, smoking history, and vascular occlusive site between High and Low FVHs patients, except for infarct morphology (P<0.01). Patients with Distal FVH presented with significant (P<0.01) perforating artery and border zone infarcts, whereas those with Proximal FVH had significant (P<0.01) large territorial infarcts. The scores and locations of FVH could be a predictive imaging marker for infarct morphology in patients with symptomatic ICA or MCA occlusion.

Utilidad de la resonancia magnética cerebral con secuencia de difusión y valor b alto en el diagnóstico de la enfermedad de Creutzfeldt-Jakob

Background current diagnostic criteria of probable Creutzfeldt-Jakob disease (CJD) include a combination of clinical, EEG and analytic data. Recent data indicate that brain MRI including fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) sequences can be a valid and reliable tool for the diagnosis of CJD. We describe our experience with high b-value (3000 s/mm 2) diffusion-weighted imaging (DWI) in patients with probable or definite CJD and compare it with standard b-value (1000 s/mm 2) DWI. Methods we performed a retrospective analysis of patients admitted to our Hospital Service between 2002 and 2008 with a final diagnosis of probable or definite CJD. Patients were examined using either a 1.5 Tesla or a 3 Tesla MRI. The MRI protocol included T1-weigthed spin-echo sequences, T2-weighted fast spin-echo, FLAIR and DWI sequences with high b-value and standard b-value. Results during the study period there were 7 patients with probable or definite CJD. Only 3 patients (43%) showed changes on FLAIR sequence consistent with CJD. All the cases were detected with high b-value DWI, including 2 cases (28%) that would have been missed using standard b-value (1000 s/mm 2) DWI. In all the patients the changes were more conspicuous and extensive at high b-value DWI (b = 3000 s/mm 2). Conclusion our data indicate that high b-value DWI may improve the sensitivity of brain MRI for the diagnosis of CJD, allowing the detection of some cases that would have been overlooked by conventional sequences.

Usefulness of high b-value diffusion-weighted MRI in the diagnosis of Creutzfeldt-Jakob disease

Background Current diagnostic criteria of probable Creutzfeldt-Jakob disease (CJD) include a combination of clinical, EEG and analytic data. Recent data indicate that brain MRI including fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) sequences can be a valid and reliable tool for the diagnosis of CJD. We describe our experience with high b-value (3000s/mm 2) diffusion-weighted imaging (DWI) in patients with probable or definite CJD and compare it with standard b-value (1000s/mm 2) DWI. Methods We performed a retrospective analysis of patients admitted to our Hospital Service between 2002 and 2008 with a final diagnosis of probable or definite CJD. Patients were examined using either a 1.5 Tesla or a 3 Tesla MRI. The MRI protocol included T1-weigthed spin-echo sequences, T2-weighted fast spin-echo, FLAIR and DWI sequences with high b-value and standard b-value. Results During the study period there were 7 patients with probable or definite CJD. Only 3 patients (43%) showed changes on FLAIR sequence consistent with CJD. All the cases were detected with high b-value DWI, including 2 cases (28%) that would have been missed using standard b-value (1000s/mm 2) DWI. In all the patients the changes were more conspicuous and extensive at high b-value DWI (b=3000s/mm 2). Conclusion Our data indicate that high b-value DWI may improve the sensitivity of brain MRI for the diagnosis of CJD, allowing the detection of some cases that would have been overlooked by conventional sequences.

Comparison of T1-weighted fast spin-echo and T1-weighted fluid-attenuated inversion recovery images of the lumbar spine at 3.0 tesla

T1-weighted fluid-attenuated inversion recovery (FLAIR) sequence has been reported to provide improved contrast between lesions and normal anatomical structures compared to T1-weighted fast spin-echo (FSE) imaging at 1.5T regarding imaging of the lumbar spine. To compare T1-weighted FSE and fast T1-weighted FLAIR imaging in normal anatomic structures and degenerative and metastatic lesions of the lumbar spine at 3.0T. Thirty-two consecutive patients (19 females, 13 males; mean age 44 years, range 30-67 years) with lesions of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted FSE and fast T1-weighted FLAIR sequences. Both qualitative and quantitative analyses measuring the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and relative contrast (ReCon) between degenerative and metastatic lesions and normal anatomic structures were conducted, comparing these sequences. On quantitative evaluation, SNRs of cerebrospinal fluid (CSF), nerve root, and fat around the root of fast T1-weighted FLAIR imaging were significantly lower than those of T1-weighted FSE images (P<0.001). CNRs of normal spinal cord/CSF and disc herniation/ CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). ReCon of normal spinal cord/CSF, disc herniation/CSF, and vertebral lesions/CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). On qualitative evaluation, it was found that CSF nulling and contrast at the spinal cord (cauda equina)/CSF interface for T1-weighted FLAIR images were significantly superior compared to those for T1-weighted FSE images (P<0.001), and the disc/spinal cord (cauda equina) interface was better for T1-weighted FLAIR images (P<0.05). The T1-weighted FLAIR sequence may be considered as the preferred lumbar spine imaging sequence compared to T1-weighted FSE, as it has demonstrated superior CSF nulling, better conspicuousness of normal anatomic structures and degenerative and metastatic lesions, and improved image contrast.

Magnetic resonance imaging evaluation of radiation: Cranial radiation therapy-induced diffuse white matter injury

e13033 Background: To study the value of MRI in detection and grading of diffuse white matter injury induced by cranial radiation therapy for brain tumors and to evaluate the influence of various risk factors for its development. Methods: This study included 60 patients who had primary brain tumors and received external beam conventionally fractionated radiotherapy. Twenty-three out of 60 patients received chemotherapy after radiotherapy. Post radiotherapy follow-up MRI examination was performed for all patients at 6 weeks, 3, 6, 9, 12 months, and at more than 1 year from completion of radiotherapy. MR imaging was performed with T2-weighted turbo spin echo, fast fluid-attenuated inversion- recovery (FLAIR), T1-weighted spin-echo, and T1-weighted post-contrast spin-echo sequences. Results: Twenty-one of 60 patients (35%) developed diffuse white matter injury at a mean of 15.3 + 7.6 months from the completion of radiotherapy (range, 5–36 months). Radiation-related diffuse white matter changes were characterized as diffuse high signal intensity in the periventricular deep white matter on T2WI and FLAIR sequences. The MRI grading system of these periventricular hyperintensity (PVH) were as follow: 39 patients (65%) had no WMI (grade 0), four had grade 1 changes, three patients had grade 2 changes, nine patients had grade 3, and five patients had grade 4. They were symmetrical in 13 of 21 patients (61.9%), and asymmetrical in eight out of 21 patients (38.1%). The prevalence of diffuse matter injury found to be significantly related to the volume of irradiation (p = 0.02), fraction size (p = 0.008), and concomitant use of chemotherapy (p &gt; 0.02)Conclusions: Diffuse white matter injury is a known consequence of radiation therapy, and the capability of detecting and grading such damage is optimally provided by MRI. No significant financial relationships to disclose.

MR Imaging Findings in Hepatic Encephalopathy

The term hepatic encephalopathy (HE) includes a spectrum of neuropsychiatric abnormalities occurring in patients with liver dysfunction. Most cases are associated with cirrhosis and portal hypertension or portal-systemic shunts, but the condition can also be seen in patients with acute liver failure and, rarely, with portal-systemic bypass and no associated intrinsic hepatocellular disease. Although HE is a clinical condition, several neuroimaging techniques, particularly MR imaging, may eventually be useful for the diagnosis because they can identify and measure the consequences of central nervous system (CNS) increase in substances that under normal circumstances, are efficiently metabolized by the liver. Classic MR imaging abnormalities include high signal intensity in the globus pallidum on T1-weighted images, likely a reflection of increased tissue concentrations of manganese, and an elevated glutamine/glutamate peak coupled with decreased myo-inositol and choline signals on proton MR spectroscopy, representing disturbances in cell-volume homeostasis secondary to brain hyperammonemia. Recent data have shown that white matter abnormalities, also related to increased CNS ammonia concentration, can also be detected with several MR imaging techniques such as magnetization transfer ratio measurements, fast fluid-attenuated inversion recovery sequences, and diffusion-weighted images. All these MR imaging abnormalities, which return to normal with restoration of liver function, probably reflect the presence of mild diffuse brain edema, which seems to play an essential role in the pathogenesis of HE. It is likely that MR imaging will be increasingly used to evaluate the mechanisms involved in the pathogenesis of HE and to assess the effects of therapeutic measures focused on correcting brain edema in these patients.

Usefulness of contrast-enhanced FLAIR MRI in the diagnosis of intracranial tumors

目的 评价增强后液体衰减反转恢复序列(FLAIR)在颅内肿瘤诊断中的应用价值.方法 104例颅内肿瘤,经手术、病理证实共有病灶124个.分别行增强前、后T1WI和FLAIR扫描.由2名有经验的放射科医生对所有病例进行评价.评价内容包括:增强例数、增强病灶个数及强化病灶部位;对比度及增强率;病变大小和范围.结果行统计学分析.结果 104例中,增强后FLAIR(CE FLAIR)成像、增强SE T1WI(CE T1WI)均显示98例有强化.CE FLAIR成像检出了117个强化灶,CE T1WI检出了120个.4个病灶仅在CE FLAIR显示而CE T1WI未显示.另有7个病灶仅在CE T1WI显示而CE FLAIR未显示.两者之信噪比(SNR)差异无统计学意义(t=1.10,P=0.270),脑灰白质对比度(GMC)、对比噪声比(CNR)及强化率(CER)差异均有统计学意义(t值分别为2.46、7.10、9.67,P值分别为0.015、0.000、0.000).在显示病灶大小上,CE FLAIR成像明显大于CE T1WI(t=4.13,P=0.000),在病灶范围上,有62例 CE FLAIR成像较CE T1WI大.CE FLAIR成像对位于脑沟、凸面、侧脑室旁及侧脑室内病灶的检出优于CE T1WI,而对大脑半球及第四脑室内的病灶的显示不如CE T1WI.结论 CE FLAIR成像与CE T1WI比较,强化病灶数,两者无明显差别,强化程度CE T1WI明显高于CE FLAIR成像,但两者对不同部位病灶的显示有明显差异,CE FLAIR成像显示病灶大小和范围明显大于CE T1WI.两种序列相互补充,建议将CE FLAIR成像序列列为增强后常规序列。

Degenerative disc disease of the lumbar spine: a prospective comparison of fast T1-weighted fluid-attenuated inversion recovery and T1-weighted turbo spin echo MR imaging

Objective: To compare fast T1-weighted fluid-attenuated inversion recovery (FLAIR) and T1-weighted turbo spin-echo (TSE) imaging of the degenerative disc disease of the lumbar spine. Materials and methods: Thirty-five consecutive patients (19 females, 16 males; mean age 41 years, range 31–67 years) with suspected degenerative disc disease of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted TSE and fast T1-weighted FLAIR sequences. Two radiologists compared these sequences both qualitatively and quantitatively. Results: On qualitative evaluation, CSF nulling, contrast at the disc–CSF interface, the disc–spinal cord (cauda equina) interface, and the spinal cord (cauda equina)–CSF interface of fast T1-weighted FLAIR images were significantly higher than those for T1-weighted TSE images ( P < 0.001). On quantitative evaluation of the first 15 patients, signal-to-noise ratios of cerebrospinal fluid of fast T1-weighted FLAIR imaging were significantly lower than those for T1-weighted TSE images ( P < 0.05). Contrast-to-noise ratios of spinal cord/CSF and normal bone marrow/disc for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted TSE images ( P < 0.05). Conclusion: Results in our study have shown that fast T1-weighted FLAIR imaging may be a valuable imaging modality in the armamentarium of lumbar spinal T1-weighted MR imaging, because the former technique has definite superior advantages such as CSF nulling, conspicuousness of the normal anatomic structures and changes in the lumbar spinal discogenic disease and image contrast and also almost equally acquisition times.

A serial MRI study following optic nerve mean area in acute optic neuritis.

This study assessed optic nerve mean area on serial MRI in a cohort of patients with a first episode of acute unilateral optic neuritis to assess the effects of a single acute inflammatory demyelinating lesion. Twenty-nine patients with a median delay from onset of visual symptoms of 13 days (range 7-24 days) were recruited. After a clinical examination and visual evoked potential (VEP) measurement, each patient had their optic nerves imaged with a coronal fat-saturated short echo fast fluid-attenuated inversion recovery sequence. Twenty-one patients had serial examinations after 2, 4, 8, 12, 26 and 52 weeks. In addition, 32 control subjects had their optic nerves imaged up to three times. The mean cross-sectional area of the intra-orbital portion of each optic nerve was calculated by a blinded observer using a computer-assisted contouring technique. At baseline, the mean area of diseased optic nerves was 16.1 mm2 compared with 13.4 mm2 for healthy contralateral optic nerves (20.1% higher, P < 0.0001) and 13.6 mm2 for controls (18.4% higher, P = 0.0003). The diseased optic nerve mean area declined over time, from initial swelling to later atrophy. The mean decline at 52 weeks was -0.0018 mm2/day (95% confidence interval -0.0038 to -0.00051). At 52 weeks, the mean area of diseased optic nerves was 11.3 mm2 compared with 12.8 mm2 for healthy contralateral optic nerves (11.7% lower, P = 0.032) and 13.1 mm2 for controls (13.7% lower, P = 0.008). The 52 week diseased optic nerve mean area was not significantly affected by the baseline mean area. There was an association between baseline optic nerve mean area and logMAR visual acuity (rS = 0.46, P = 0.012) and visual field mean deviation (rS = -0.55, P = 0.002), but there was no evidence of an association between 1 year mean area and visual outcome. There was no evidence of association between baseline, rates of decline or 1 year diseased optic nerve mean areas and any of the baseline, 1 year or time-averaged VEP variables. The present study shows a consistent pattern of changes associated with individual inflammatory demyelinating lesions in the optic nerve. Acutely, there was swelling, consistent with the presence of acute inflammation, which was related to visual impairment. Over the longer term, there was loss of tissue. The lack of association between 1 year optic nerve mean area and visual outcome may reflect a mild loss of tissue, redundancy or remodelling of function.

MR Imaging of Epidermoids at the Cerebellopontine Angle

The most common location of intracranial epidermoid is the cerebellopontine angle (CPA). The present study compared the visibility of epidermoid at the CPA in various pulse sequences. Seven patients with epidermoid at the CPA underwent conventional MR imaging (T(1)-, T(2)- and proton density-weighted imaging) as well as diffusion-weighted echo-planar imaging. Fast fluid-attenuated inversion recovery (FLAIR) sequences, magnetization transfer contrast (MTC) sequences, and MR cisternography were employed for selected patients. The signal intensity of the lesions relative to cerebrospinal fluid (CSF), the degree of lesion demarcation and the displacement of surrounding structures were evaluated. Proton density-weighted imaging depicted the lesions as hyper-intense to CSF with clearer delineation than T(1)- and T(2)-weighted imaging. Diffusion-weighted imaging depicted all lesions as strongly hyper-intense relative to CSF and brain tissue. FLAIR sequences depicted the lesions with mixed signal intensities but with poor-to-medium demarcation. MTC imaging increased delineation of the lesions to some degree. MR cisternography depicted the lesions as hypo-intense to CSF and clearly showed the anatomical relation to neighboring nerves and vessels. We concluded that diffusion-weighted imaging could specifically reveal an epidermoid at the CPA as a strongly hyper-intense lesion, and that MR cisternography is mandatory for preoperative planning.

Isotropic 3D fast FLAIR imaging of the brain in multiple sclerosis patients: initial experience

The application of image registration and subtraction to detect change in multiple sclerosis (MS) disease burden on serial MR scans benefits from the use of isotropic voxels. An optimised 3D fast fluid-attenuated inversion recovery (FLAIR) sequence with 1.2- and 1.8-mm cubic voxels was compared with a 2D T2 SE sequence using standard 3-mm slices. Three-dimensional fast FLAIR and T2 SE series were obtained in 20 MS patients and 15 controls. Whole brain acquisition times for the 1.2- and 1.8-mm FLAIR were 21 and 10.5 min, respectively, for the interleaved T2 SE 16 min. Brain lesions were marked in consensus by two radiologists and the CNR was calculated in ten lesions. The mean number of lesions detected with the 1.2-mm FLAIR sequence was 115 +/- 76, compared with 85 +/- 59 for the T2 SE series ( p<0.001). The 1.8-mm FLAIR detected only 73 +/- 46 lesions. The CNR of the 1.2-mm FLAIR was significantly better than the T2 SE ( p<0.01), but not as good as the 1.8-mm FLAIR. In conclusion, isotropic 3D fast FLAIR using 1.2-mm cubic voxels is superior to the 2D T2 SE in the detection of brain lesions in MS patients. The isotropic 1.8-mm FLAIR is faster and has better contrast characteristics but lacks sensitivity.

Variations in T1 and T2 relaxation times of normal appearing white matter and lesions in multiple sclerosis

Objective: To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain. Background: The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions. Method: Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times. Results: Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times. Conclusion: Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection.

Assessment of cerebral gliomas by a new dark fluid sequence, high intensity REduction (HIRE): a preliminary study.

The purpose of this study was to assess the diagnostic potential of a new dark fluid sequence, high intensity reduction (HIRE) in the diagnostic workup of patients with cerebral gliomas. The HIRE sequence utilizes a very long T(2) value of the cerebrospinal fluid (CSF) to suppress its high signal contribution in T(2)-weighted imaging by a image subtraction technique. Fifteen patients with histologically confirmed cerebral gliomas were examined with T(2)-weighted fast spin-echo (FSE), T(1)-weighted SE, fast fluid-attenuated inversion recovery (FLAIR), and HIRE imaging using identical scan parameters. In patients with enhancing lesions, fast FLAIR and HIRE were added to the contrast-enhanced T(1)-weighted SE images. Images were analyzed in a qualitative and quantitative evaluation. In the qualitative analysis, lesion detection, lesion delineation, and differentiation between enhancing and non-enhancing tumor tissue were assessed in a two-reader study. For the quantitative analysis, lesion-to-background and lesion-to-CSF contrast and contrast-to-noise ratios were determined in a region of interest analysis. HIRE achieved a significant reduction of the CSF signal without losing the high gray-to-white matter contrast of T(2)-weighted sequences. In the quantitative analysis, the contrast ratios of the HIRE images were lower compared with the FLAIR images due to a relatively high background and CSF signal. After administration of contrast media, HIRE images presented a significant signal increase in enhancing lesions, which subsequently increased the contrast and contrast-to-noise ratios. In the qualitative analysis, both readers found all tumors clearly delineated on HIRE imaging. Compared with T(2)-weighted FSE, the tumor delineation with HIRE was better in nine patients, equal in four patients, and less in one patient. Compared with the FLAIR images, HIRE was rated superior in three patients, equal in nine patients, and inferior in another three patients. Delineation of the enhancing tumor parts was possible with HIRE in all patients. HIRE images had significantly fewer image artifacts than FLAIR images due to reduced inflow effects. The T(2)-based HIRE sequence presented is an alternative to the T(1)-based FLAIR sequence, with the advantage of better gray-to-white matter contrast and shorter measurement time. Due to the subtraction technique, signal intensities from tissues with relaxation times in the range T(2 WM) < < T(2) < T(2 CSF) are also gradually affected, corresponding to their T(2) values. With respect to this unwanted effect, an improvement in HIRE imaging will be possible by using a self-weighted subtraction algorithm. In a forthcoming study this concept will first be tested on appropriate phantom fluids.

The sensitivity of thin-slice fast spin echo, fast FLAIR and gadolinium-enhanced T1-weighted MRI sequences in detecting new lesion activity in multiple sclerosis.

Fast fluid-attenuated inversion-recovery (FLAIR) and proton density/T2-weighted fast spin echo (FSE) brain images with 3-mm slices were acquired monthly for 7 months in 37 multiple sclerosis patients. New and enlarging lesions were counted and compared according to the site of lesions seen with each sequence. In addition, the number of new enhancing lesions seen on gadolinium-enhanced T1-weighted brain magnetic resonance imaging at the same time points was counted. All sequences used 3-mm contiguous axial slices. Overall, 126 new or enlarging lesions were seen on FSE and 135 on fast FLAIR (P = 0.25, Wilcoxon signed ranks test). Regional comparisons revealed significantly more fast FLAIR lesions only in the cortical/subcortical areas. There was a total of 295 new enhancing lesions over the same period -- a gain in the number of 'active lesions' of 234% seen with FSE and 218% with FLAIR. It is concluded that serial thin slice fast FLAIR is only slightly superior to FSE in detecting new and enlarging multiple sclerosis lesions but the difference is not sufficient to recommend that FLAIR should replace FSE in short-term, exploratory trials in MS using monthly scanning. Gadolinium-enhanced imaging is more then twice as sensitive as either FSE or fast FLAIR to new multiple sclerosis lesion activity, and enhancing lesions should provide the primary outcome measure in such studies.

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.

Fast flair imaging of the brain using the fast spin-echo and gradient spin-echo technique

The purpose of this study was to compare the gradient spin-echo (GRASE) to the fast spin-echo (FSE) implementation of fast fluid-attenuated inversion recovery (FLAIR) sequences for brain imaging. Thirty patients with high signal intensity lesions on T 2-weighted images were examined on a 1.5 T MR system. Scan time-minimized thin-section FLAIR-FSE and FLAIR-GRASE sequences were obtained and compared side by side. Image assessment criteria were lesion conspicuity, contrast between different types of normal tissue, image quality, and artifacts. In addition, contrast ratios and contrast-to-noise ratios were determined. Compared to FSE, the GRASE technique allowed a 17% reduction in scan time but conspicuity of small lesions in particular was significantly lower on FLAIR-GRASE images because of higher image noise and increased artifacts. Gray-white differentiation was slightly worse on FLAIR-GRASE. Physiological ferritin deposition appeared slightly darker on FLAIR-GRASE images and susceptibility artifacts were stronger. Fatty tissue was less bright with FLAIR-GRASE. With current standard hardware equipment, the GRASE technique is not an adequate alternative to FSE for the implementation of fast FLAIR sequences in routine clinical MR brain imaging.

Initial clinical experience in MR imaging of the brain with a fast fluid-attenuated inversion-recovery pulse sequence.

To evaluate fast fluid-attenuated inversion-recovery (FLAIR) technique for imaging brain abnormalities. A fast FLAIR sequence was developed that provided 36 5-mm contiguous sections in 5 minutes 8 seconds. Resulting images were compared with dual-echo T2-weighted spin-echo images of 41 consecutive patients with brain abnormalities. Contrast and contrast-to-noise ratios (C/Ns) (for contrast between the lesion and background and between the lesion and cerebrospinal fluid) for fast FLAIR exceeded the corresponding values for T2-weighted spin-echo images for all but the second-echo lesion-to-background C/N. Fast FLAIR provided equivalent or greater overall lesion conspicuity and enabled greater lesion detection in 98% and 100%, respectively, of the evaluations. Fast FLAIR images more often had image artifact, but this did not interfere with image interpretation in a significantly (P < or = .05) greater number of evaluations. Fast FLAIR provides images that are superior to proton-density- and T2-weighted images for many image quality criteria.