Detection of acute small amount of subarachnoid hemorrhage: Comparison between fluid-attenuated inversion recovery MR imaging and CT

Purpose

To evaluate the possibility of detecting small amount of acute subarachnoid hemorrhage (ASH) diluted by CSF not revealed by CT but identified on fluid-attenuated inversion recovery (FLAIR) MRI.

Patients and methods

50 patients with acute neurological symptoms were referred from the neurosurgery department to the radiodiagnosis department for computed tomography CT and magnetic resonance imaging MRI examination.

Results

Lumbar puncture proved 41 positive cases, MRI (FLAIR) interpreted 43 positive cases (40 true positive and 3 false positive) and 7 negative cases (6 true negative and one false negative) while CT interpreted 39 positive cases (37 true positive and 2 false positive) and 11 negative cases (7 true negative and 4 false negative).

Conclusion

FLAIR MRI was more sensitive and more accurate in the diagnosis of acute SAH than CT scan, having a much higher negative predictive value to exclude acute SAH, however its positive predictive value was slightly lower than CT, but there was no statistically significant difference statistically between the two in diagnosis of SAH.     

Hyperintense signal abnormality in subarachnoid spaces and basal cisterns on MR images of children anesthetized with propofol: new fluid-attenuated inversion recovery finding

BACKGROUND AND PURPOSE: MR imaging is the method of choice for pediatric neuroimaging. Sedation is often needed to suppress patient motion and ensure diagnostic image quality, and propofol is rapidly becoming the preferred anesthetic. The purpose of this study was to document a new finding on fast fluid-attenuated inversion recovery (fast-FLAIR) MR images of children anesthetized with propofol that can be mistaken for subarachnoid space pathologic abnormality. METHODS: A retrospective analysis was conducted of 55 MR images of the brain for children who ranged in age from 1 week to 12 years. Forty-two patients received chloral hydrate, and 13 received propofol anesthetic. Multiplanar MR images were studied to detect the presence or absence of hyperintense signal (artifact) in the subarachnoid spaces and basal cisterns. The T1 values and null times of chloral hydrate, propofol, and CSF were determined in vitro at room temperature by using an inversion recovery pulse sequence at 1.5 T. RESULTS: The fast-FLAIR images of all 13 patients who received propofol had hyperintense signal abnormality. For 10 (77%) of 13 patients, this artifact was in the basal cisterns and subarachnoid spaces overlying the brain convexity. For three (23%) of 13 patients, this artifact was in the convexity region only. Two patients underwent follow-up MR imaging with a nonpropofol anesthetic agent, and the artifact resolved. None of the images of the children who received chloral hydrate had this artifact. The T1 value of chloral hydrate was 0.2 s, of propofol was 1.86 s, and of CSF was 2.32 s at room temperature. CONCLUSION: The fast-FLAIR images of children anesthetized with propofol have artifactual hyperintense signal in the basal cisterns and subarachnoid spaces, and this artifact mimics disease of the subarachnoid space. The T1 value of propofol approaches that of CSF. Depending on the chosen null time, there may be incomplete nulling of signal coming from propofol. To account for this observation, other possible causes include increased CSF pulsation in children creating motion artifact, changes in arterial oxygen concentration intrinsic to propofol or related to the supplemental oxygen normally administered, or changes in CSF protein levels related to propofol binding to proteins for uptake into CSF.     

High signal intensity of the infundibular stalk on fluid-attenuated inversion recovery MR.

PURPOSETo determine the MR imaging characteristics of the pituitary stalk with a fluid-attenuated inversion recovery (FLAIR) technique.METHODSWe retrospectively studied the prevalence of a high-signal infundibular stalk on FLAIR MR images of the brain in 133 patients and compared this finding with the patients'' ages. To understand the cause of the high signal intensity of the pituitary stalk on FLAIR images, we calculated the T1, T2, and proton-density values in regions of gray matter, white matter, and the pituitary stalk in nine cases.RESULTSFLAIR images showed the pituitary stalk as having high signal intensity in 97 (73%) of 133 cases; however, in 11 of 16 patients less than 10 years old, the infundibular stalk was not of high signal intensity. In patients with a high-signal pituitary stalk on FLAIR images, the T2 value of the pituitary stalk was longer than that of gray or white matter.CONCLUSIONHigh signal intensity of the infundibular stalk was frequently seen on FLAIR MR images of the brain at all ages. A prolonged T2 value of the pituitary stalk caused the high signal intensity, presumably reflecting the fluid component of the pituitary stalk.     

Increased signal intensity within glioblastoma resection cavities on fluid-attenuated inversion recovery imaging to detect early progressive disease in patients receiving radiotherapy with concomitant temozolomide therapy

Purpose

Our study tested the diagnostic accuracy of increased signal intensity (SI) within FLAIR MR images of resection cavities in differentiating early progressive disease (ePD) from pseudoprogression (PsP) in patients with glioblastoma treated with radiotherapy with concomitant temozolomide therapy.

Methods

In this retrospective study approved by our Institutional Review Board, we evaluated the records of 122 consecutive patients with partially or totally resected glioblastoma. Region of interest (ROI) analysis assessed 33 MR examinations from 11 subjects with histologically confirmed ePD and 37 MR examinations from 14 subjects with PsP (5 histologically confirmed, 9 clinically diagnosed). After applying an N4 bias correction algorithm to remove B0 field distortion and to standardize image intensities and then normalizing the intensities based on an ROI of uninvolved white matter from the contralateral hemisphere, the mean intensities of the ROI from within the resection cavities were calculated. Measures of diagnostic performance were calculated from the receiver operating characteristic (ROC) curve using the threshold intensity that maximized differentiation. Subgroup analysis explored differences between the patients with biopsy-confirmed disease.

Results

At an optimal threshold intensity of 2.9, the area under the ROC curve (AUROC) for FLAIR to differentiate ePD from PsP was 0.79 (95% confidence interval 0.686–0.873) with a sensitivity of 0.818 and specificity of 0.694. The AUROC increased to 0.86 when only the patients with biopsy-confirmed PsP were considered.

Conclusions

Increased SI within the resection cavity of FLAIR images is not a highly specific sign of ePD in glioblastoma patients treated with the Stupp protocol.

     

椎基底动脉延长扩张症的FLAIR影像分析

目的：探讨在椎基底动脉延长扩张症（VBD）患者 FLAIR 序列中血管高信号征（FVH）的特征及其意义。方法：2011年1月－2015年4月本院确诊的49例 VBD 患者,所有患者均行 MRI 常规检查及 TOF-MRA 检查,按照临床表现分为后循环缺血组（18例）及非后循环缺血组（31例）,比较两组临床资料及影像表现的差异,并分析 FVH 征的临床意义。结果：49例 VBD 患者中,36例（73．5％）血管 FVH 征阳性。其中,22例（44．9％）表现为1级,11例表现为2级（22．4％）,3例（6．1％）表现为3级,后循环缺血组 FVH 评分较高者（2或3级）的构成比显著高于非后循环缺血组（55．6％ vs 12．9％,χ2＝11．493,P ＝0．009）。VBD 患者的 FVH 分级与基底动脉（BA）直径、长度及 BA 横向偏移之间具有低度相关性（r＝0．473,P ＝0．001;r＝0．483,P ＜0．001;r＝0．542,P ＜0．001）。结论：VBD 患者 FVH 征阳性率高,其形成机制可能与 BA 血流缓慢有关,且高级别 FVH（2或3级）的出现可以提示 VBD 患者发生后循环缺血的可能性较大。     

Comparison of magnetic resonance imaging sequences with computed tomography to detect low-grade subarachnoid hemorrhage: Role of fluid-attenuated inversion recovery sequence

OBJECTIVES: To compare computed tomography (CT) with magnetic resonance imaging (MRI) for the presumptive diagnosis and localization of acute and subacute low-grade subarachnoid hemorrhage (SAH). METHODS: We consecutively enrolled 45 patients clinically suspected of low-grade SAH, comparing them with a control group. We obtained axial nonenhanced CT scans as well as fluid-attenuated inversion recovery (FLAIR) and T2-weighted gradient echo (T2*) MRI sequences at 1.0 T. Two neuroradiologists scrutinized the presence of blood at 26 different regions in the intracranial subarachnoid space (SAS). RESULTS: Three of 45 patients had normal CT and MRI scans, and SAH was excluded by lumbar puncture. We demonstrated SAH on CT scans in 28 of 42 (66.6%) patients, T2* sequences in 15 of 42 (35.7%) patients, and FLAIR sequences in 42 of 42 (100%) patients. Fluid-attenuated inversion recovery sequences were superior to CT in 16 of the 26 evaluated regions. CONCLUSIONS: The FLAIR sequence was superior for presumptive diagnosis and localization of acute and subacute low-grade SAH, representing a potential tool in this setting.     

Protoneus-sequence: extended fluid-attenuated inversion recovery MR imaging without and with contrast enhancement

Fluid-attenuated inversion recovery imaging (=flair imaging) is widely used as primary screening sequence in various investigation protocols, due to its high lesion contrast and sensitivity in detection of parenchymatous and leptomeningeal disease. An additional increase of sensitivity for detection of lesions may be achieved by contrast-enhanced flair imaging. Based on flair imaging a dual-echo inversion recovery imaging sequence (=proton echo usage [=protoneus] - sequence) was developed, which could significantly extend the possibilities of conventional flair imaging.     

液体衰减反转恢复序列在腹部及盆腔疾病应用价值的探讨

目的：探讨液体衰减反转恢复（fluid—attenuated inversion recovery，FLAIR）序列与其他序列搭配在腹部疾患应用的临床价值，并初步评价其适用范围。方法：对90例患者共226个病灶进行定性，按常规扫描方法加上FLAIR序列进行检查，之后根据需要按照下列步骤进行扫描：①行质子像（PDW）；②多回波成像；③仅有46例患者行静脉注射Gd-DTPA增强扫描。结果：所有病灶应用FLAIR后T2W均有变化；85例为降低，仅5例升高，经FLAIR后病灶依信号强度分为高、等、低3种。分别为23个（10．2％）；65个（28．8％）；138个（61．1％）。有175个病灶FLAIR明确诊断．占77．4％．22个行质子像，多回波成像定性。46例经增强扫描确定性质。低信号病灶均为囊性病变或液体，等信号病灶均为良性病变，增强前后应用FLAIR测量的T2值具有统计学意义。结论：在结果判定上以低信号组病例最具有诊断意义。等信号组均为良性病变。高信号组解释较为复杂。     

Postoperative fluid-attenuated inversion recovery MR imaging of cerebral gliomas: initial results

Fluid-attenuated inversion-recovery (FLAIR) imaging has shown to be a valuable imaging modality in the assessment of intra-axial brain tumors; however, no data are available about the role of this technique in the clinically important postoperative stage. The purpose of this study was to evaluate the diagnostic potential of FLAIR MR imaging in residual tumor after surgical resection of cerebral gliomas. Fifteen patients with residual cerebral gliomas were examined within the first 18 days after partial surgical resection of cerebral gliomas. The imaging protocol included T1-weighted spin echo, T2- and proton-density-weighted fast spin echo, and FLAIR imaging with identical slice parameters. T1 and FLAIR were repeated after contrast media application. Detection and delineation of residual tumor were the primary parameters of the image analysis. Additionally, the influence of image artifacts on the image interpretation was assessed. On FLAIR images residual signal abnormalities at the border of the resection cavities were observed in all patients, whereas T2- and T1-weighted images present residual abnormalities in 13 of 15 and 10 of 15 patients, respectively. The FLAIR imaging was found to be superior to conventional imaging sequences in the delineation of these changes and comparable to contrast enhanced T1-weighted imaging in the delineation of residual enhancing lesions. Because of protein cell components and blood byproducts within the resection cavity, FLAIR imaging was unable to suppress the cerebrospinal fluid (CSF) in 4 patients. After the decomposition of proteins and blood, CSF could again be completely suppressed and residual or recurrent tumors were clearly identified. Our preliminary study has shown that FLAIR may be a valuable diagnostic modality in the early postoperative MR imaging after resection of cerebral gliomas due to its better delineation of residual pathologic signal at the border of the resection cavity. It should therefore be integrated into the early and/or intraoperative MR imaging protocol.     

Imaging of acute subarachnoid hemorrhage with a fluid-attenuated inversion recovery sequence in an animal model: comparison with non-contrast-enhanced CT.

BACKGROUND AND PURPOSE: Fluid-attenuated inversion recovery (FLAIR) MR imaging sequences have been previously described in the evaluation of acute subarachnoid hemorrhage (SAH) in human subjects and have demonstrated good sensitivity. The purpose of this study was to evaluate a FLAIR sequence in an animal model of SAH and to compare the results with those obtained with non-contrast-enhanced CT. METHODS: SAH was experimentally induced in 18 New Zealand rabbits by injecting autologous arterial blood into the subarachnoid space of the foramen magnum. Nine animals had high-volume (1-2 mL) injections, and nine animals had low-volume (0.2-0.5 mL) injections. Four control animals were injected with 0.5 mL of saline. The animals were imaged with a FLAIR sequence and standard CT 2-5 hours after injection. Gross pathologic evaluation of seven of the animals was performed. Four blinded readers independently evaluated the CT and FLAIR images for SAH and graded the probability of SAH on a scale of 1 to 5 (1 = no hemorrhage, 5 = definite hemorrhage). RESULTS: Overall, the sensitivity of FLAIR was 89%, and the sensitivity of CT was 39% (P <.01). In animals with a high volume of SAH, the sensitivity of FLAIR was 100%, and the sensitivity of CT was 56%. In animals with a low volume of SAH, the sensitivity of FLAIR was 78%, and the sensitivity of CT was 22%. The specificity of FLAIR in animals without SAH was 100%, and the specificity of CT was 100%. The average reader score for FLAIR was 3.8, and that for CT was 2.2 (P <.001). Reader scores for FLAIR were higher than those for CT in 94% (P <.01) of animals with SAH and in 25% of animals without SAH (P >.05). Seven animals underwent gross pathologic examination, and all had blood in the subarachnoid space around the brain stem. CONCLUSION: FLAIR was more sensitive than CT in the evaluation of acute SAH in this model, especially when a high volume of SAH was present. This study provides a model for further experimentation with MR imaging in the evaluation of SAH. These findings are consistent with those of current clinical literature, which show FLAIR to be an accurate MR sequence in the diagnosis of SAH.     

Analysis of cystic intracranial lesions performed with fluid-attenuated inversion recovery MR imaging.

BACKGROUND AND PURPOSE: T1-, T2-, and proton density (PD)-weighted sequences are used to characterize the content of cystic intracranial lesions. Fluid-attenuated inversion recovery (FLAIR) MR sequences produce T2-weighted images with water signal saturation. Therefore, we attempted to verify whether FLAIR, as compared with conventional techniques, improves the distinction between intracranial cysts with a free water-like content versus those filled with a non-free water-like substance and, consequently, aids in the identification of these lesions as either neoplastic/inflammatory or maldevelopmental/porencephalic. METHODS: Forty-five cystic intracranial lesions were studied using T1-weighted, T2-weighted, FLAIR, and PD-weighted sequences. By means of clustering analysis of the ratio in signal intensity between the cystic intracranial lesions and CSF, the intracranial lesions were classified as filled with a free water-like content or with a non-free water-like substance. The results were compared with their true content as evaluated either histologically or on the basis of clinical, neuroradiologic, and follow-up features (necrotic material, 13 cases; accumulation of intercellular proteinaceous/myxoid material, eight cases; keratin, five cases; CSF, 19 cases). Cystic intracranial lesions were divided into two clinical groups, neoplastic/inflammatory and maldevelopmental/porencephalic, to evaluate the level of accuracy of each MR technique. The difference in absolute value signal intensity between CSF and cystic intracranial lesion content was calculated on FLAIR and PD-weighted images. RESULTS: PD-weighted and FLAIR sequences, unlike T1- and T2-weighted sequences, accurately depicted all cystic intracranial lesions containing necrotic or myxoid/proteinaceous intercellular material (non-free water-like) and most CSF-containing cystic intracranial lesions (free water-like). All imaging techniques inaccurately showed some of the keratin-containing cystic intracranial lesions and pineal cysts. The overall error rate was 22% for T1-weighted, 27% for T2-weighted, 9% for FLAIR, and 13% for PD-weighted sequences. The signal intensity difference between CSF and cystic intracranial lesion content was higher with FLAIR imaging. CONCLUSIONS: FLAIR imaging depicts far more accurately the content of cystic intracranial lesions and better reveals the distinction between maldevelopmental/porencephalic and neoplastic/inflammatory lesions than do conventional sequences. FLAIR has the added advantage of a higher signal intensity difference between cystic intracranial lesions and CSF.     

Relationship between the concentration of supplemental oxygen and signal intensity of CSF depicted by fluid-attenuated inversion recovery imaging

BACKGROUND AND PURPOSE: Prior reports have described increased signal intensity (SI) of CSF on fluid-attenuated inversion recovery (FLAIR) images of anesthetized patients receiving 100% O(2). This appearance can simulate that of diseases. We evaluated the relationship between the concentration of inhaled O(2) and the development of increased SI of CSF on FLAIR images. METHODS: FLAIR was performed in 25 healthy volunteers breathing room air and 100% O(2) through a face mask for 5, 10, and 15 minutes. MR imaging, including FLAIR imaging, was performed in 52 patients with no potential meningeal abnormalities under general anesthesia: 21 received an equal mixture of N(2)O and O(2), and 31 received 100% O(2). The SI of CSF in volunteers and patients was graded in several locations by using a three-point scale. RESULTS: SI of CSF significantly increased (P <.05) in various locations, in both volunteers and patients breathing 100% O(2), when compared with SI in the same volunteers breathing room air. Hyperintensity of CSF was not significantly different in volunteers receiving 100% O(2) through a face mask compared with anesthetized patients receiving 100% O(2) through a laryngeal airway or an endotracheal tube. No significant increase in SI occurred in patients receiving 50% O(2), when compared with the SI of volunteers breathing room air. CONCLUSION: Supplemental oxygen at 100% is a main cause of artifactual CSF hyperintensity on FLAIR images, regardless of the anesthetic drug used. This artifact does not develop when 50% O(2) is administered.     

Role of fluid-attenuated inversion recovery in the diagnosis of meningitis: comparison with contrast-enhanced magnetic resonance imaging

OBJECTIVE: Fluid-attenuated inversion recovery (FLAIR) has shown promise in the detection of subarachnoid space disease. The exact role of FLAIR in the diagnosis of meningitis has not been established. The purpose of this study was to evaluate FLAIR in the detection of meningitis in comparison with contrast-enhanced T1-weighted images (T1WI) in a blinded-reader study. We describe hyperintense sulci (HS) on FLAIR sequence in meningitis in relation to cerebrospinal fluid (CSF) protein and effective echo time (TE). METHODS: Two observers blinded to clinical information reviewed magnetic resonance (MR) images of patients with the diagnosis of meningitis and those of age-matched controls. The diagnosis was confirmed from chart review and CSF results. FLAIR images were obtained with 2 different TE values of 120 milliseconds and 150 milliseconds. FLAIR changes were correlated with CSF protein concentration and contrast-enhanced T1WI. RESULTS: Twenty-eight MR images of meningitis patients were reviewed. There were 23 abnormal MR images including 16 abnormal FLAIR scans with hyperintense sulci and 23 with leptomeningeal enhancement on contrast-enhanced T1WI. HS on FLAIR correlated with leptomeningeal enhancement on contrast-enhanced T1WI. Four viral and 1 bacterial meningitis had normal MR images (FLAIR and postcontrast TIWI). Two different TE values were used: 120 milliseconds (n = 15) and 150 milliseconds (n = 13). All patients with effective TE of 150 milliseconds. and CSF protein of more than 132 mg/dL had hyperintense sulci whereas patients with effective TE of 120 milliseconds and CSF protein of 257 mg/dL or more had HS. CONCLUSIONS: The sensitivity of contrast-enhanced T1WI was higher than FLAIR. HS on FLAIR correlated with contrast enhancement on T1WI. However, the sensitivity of FLAIR depends on CSF protein concentration threshold for (CSF hyperintensity) for a given effective TE. FLAIR cannot replace contrast-enhanced T1WI in diagnosing meningitis.