脑磁共振静脉成像

目的：磁共振静脉成像(MRV)已被广泛应用于颅内静脉系统检查，特别是用来评价静脉窦血栓形成。本研究的目的是评价脑MRV描述正常颅内静脉系统解剖和变异的作用，评价它在诊断硬脑膜窦血栓形成过程中潜在的误诊因素。材料和方法：对79例常规磁共振表现正常的MRV图像进行分析，观察硬脑膜窦和主要静脉的表现和缺失情况。其中7例志愿者接受了MRV和3DPCMRA两种方法检查。结果：上矢状窦、直窦、Galen静脉和大脑内静脉显示率为100％，枕窦显示率为10％，基底静脉显示率为92％。横窦血流间隙显示率约为34％，均出现在非优势侧横窦，优势侧横窦没有出现流动间隙。结论：MRV是有效的评价颅内静脉系统方法。常规MR表现正常者中有34％可以发现横窦流动间隙，这些流动间隙不应被误诊为静脉窦血栓形成。     

Cerebral MR venography in children: comparison of 2D time-of-flight and gadolinium-enhanced 3D gradient-echo techniques

PURPOSE: To prospectively compare two-dimensional (2D) time-of-flight cerebral magnetic resonance (MR) venography with gadolinium-enhanced three-dimensional (3D) gradient-echo cerebral MR venography in children. MATERIALS AND METHODS: This investigation had investigational review board approval and was Health Insurance Portability and Accountability Act compliant; parental informed consent was obtained. Thirty-seven patients (20 boys, 17 girls) who ranged in age from 4 days to 15 years underwent 2D and 3D MR venography. Two pediatric neuroradiologists compared the visibility of the superior sagittal, straight, transverse, and sigmoid sinuses and the internal jugular veins on images obtained with the two sequences. RESULTS: In 17 (46%) of the 37 patients, the sequences were equivalent in terms of their depiction of venous anatomy. In 19 (51%) of the 37 patients, 3D MR venography was superior to 2D MR venography. Suboptimal enhancement of veins occurred in one (3%) patient at 3D MR venography. Venous anomalies suggested at 2D MR venography but not present at 3D MR venography included flow gaps in the nondominant transverse sinuses of four patients, unilateral transverse sinus atresia in eight, and a narrowed superior sagittal sinus in two. Two-dimensional MR venography results failed to reveal a persistent falcine sinus associated with straight sinus atresia in one patient and suggested transverse sinus thrombosis in two patients in whom 3D MR venography results were normal. Additionally, the extent of dural thrombosis was overestimated at 2D MR venography in one patient. As compared with 3D MR venography, 2D MR venography failed to reveal sigmoid sinus stenosis in one patient and poorly depicted posterior fossa dural sinus anatomy in two patients with dural arteriovenous fistula. CONCLUSION: Three-dimensional MR venography is often superior to 2D MR venography in the delineation of major cerebral venous structures in children. Most of the artifactual loss of vascular signal seen with the use of 2D MR venography occurred in nondominant transverse sinuses.     

Evaluation of the intracranial dural sinuses with a 3D contrast-enhanced MP-RAGE sequence: prospective comparison with 2D-TOF MR venography and digital subtraction angiography

BACKGROUND AND PURPOSE: The diagnosis of dural sinus thrombosis is often difficult because of its variable and nonspecific clinical presentation and the overlapping signal intensities of thrombosis and venous flow on conventional MR images and MR venograms. We compared 3D contrast-enhanced magnetization-prepared rapid gradient-echo (MP-RAGE) sequences with 2D time-of-flight (TOF) MR venography, digital subtraction angiography (DSA), and conventional spin-echo (SE) MR imaging for the assessment of normal and abnormal dural sinuses. METHODS: In a phantom study, a plastic tube with pulsating flow was used to simulate the intracranial dural sinus. With 3D MP-RAGE, a variety of flow velocities, contrast material concentrations, and angulations between the phantom flow tube and the plane of acquisition were tested to measure their relationship to signal-to-noise ratio (SNR). In a clinical study, 35 patients, including 18 with suspected dural sinus thrombosis, were studied with both MR imaging and DSA. Receiver operating characteristic (ROC) analysis was performed in a blinded fashion using DSA as the reference standard. RESULTS: With the phantom, the SNR of flow increased with increasing contrast concentration, but was not affected by the angle between the tube and scan slab. There was no relationship between SNR and velocity when the contrast concentration was 1.0 mmol/L or greater. In the clinical study, dural sinus thrombosis as well as the normal anatomy of the dural sinuses were seen better with 3D contrast-enhanced MP-RAGE than with 2D-TOF MR venography. Three-dimensional contrast-enhanced MP-RAGE showed the highest diagnostic confidence on ROC curves in the diagnosis of thrombosis. CONCLUSION: Three-dimensional contrast-enhanced MP-RAGE is superior to 2D-TOF MR venography and conventional SE MR imaging in the depiction of normal venous structures and the diagnosis of dural sinus thrombosis, and is a potential alternative to DSA.     

Report on the ECR2003 (European Congress of Radiology): non-contrast intracranial MR venography with 3D-phase contrast imaging: optimization of presaturation pulse and velocity encoding

BACKGROUND: Intracranial MR venography is useful for the diagnosis of dural sinus thrombosis and the preoperative assessment of sinus patency encased by tumors. Recently, contrast-enhanced MR venography has been applied for suspected dural sinus occlusion in a shorter time. However, it has some disadvantage for the evaluation of hypervascularized enhancing thrombus mimicking flow in chronic sinus thrombosis. So far, we have evaluated optimal imaging technique and slice orientation and have shown that sagittal three-dimensional (3D) -phase contrast (PC) imaging is the most suitable for the non-contrast intracranial MR venography. PURPOSE:To assess the optimal presaturation pulse (SAT) and velocity encoding (VENC) for the non-contrast intracranial 3D-PC MR venography. METHODS AND MATERIALS: Firstly, we performed phantom experiment to assess the best SAT thickness using arterial presaturation. Second, MR imaging was performed in 7 healthy volunteers to measure the dural sinus flow velocity using a 1.5 T MR. Third, 3D-PC MR venography was performed with a VENC settings at 10, 15, 20 and 30 cm/sec for healthy volunteers. All data were displayed as maximum intensity projection images and three neuroradiologists assessed the visibility of the dural sinuses and the cortical vein. RESULTS: The mean flow velocity of the dural sinuses was 6.3 cm/sec. The thickness of the best SAT was 100 mm. In the assessment of the visibility of the 3D-PC images, dural sinuses were adequately visualized at a VENC of 15 cm/sec. CONCLUSIONS: Non-contrast intracranial 3D-PC MR venography was optimized at 100mm thickness of SAT and a VENC of 15 cm/sec.     

颅内静脉窦血栓形成的早期MRI诊断及病理基础

目的:研究颅内静脉窦血栓形成(CVST)的MR表现及其病理基础,旨在提高早期诊断水平.方法:回顾分析经临床和影像学方法确诊的11例CVST患者.MR检查技术包括平扫、增强扫描及MRV;其中4例行CT平扫检查;3例行DSA检查.结果:11例CVST累及上矢状窦5例,横窦1例,乙状窦1例,直窦1例,上矢状窦及横窦及乙状窦联合受累2例,横窦及乙状窦联合受累1例.CVST的直接征象:急性期血栓3例,T1 WI呈等信号或等高混杂信号,T2 WI呈低信号,周围可见稍高信号的环,为增厚的硬膜;亚急性期血栓8例,T1 WI及T2 WI均以高信号为主.增强扫描受累静脉窦可见空"三角"征或"充盈缺损"征.MRV可显示受累静脉窦不显影或者充盈缺损形成.CVST的继发脑损害包括脑肿胀、出血及梗死等.结论:磁共振检查对CVST的早期诊断具有重要价值.对于T2 WI呈低信号的急性期血栓,应仔细观察围是否有较高信号的环形改变,进一步行增强扫描结合MRV检查可作出早期准确的诊断.     

Intracranial MR venography in children: normal anatomy and variations

BACKGROUND AND PURPOSE: Little information is available regarding the anatomy of the intracranial veins and sinuses that can be shown on MR venograms of children. The aim of this study was to determine the normal venous anatomy and anatomic variants. METHODS: Fifty children who were referred for investigation of developmental delay and who had normal results of MR imaging of the brain were recruited into the study. The cerebral veins and sinuses, including the occipital sinuses, were assessed by using 2D time-of-flight venography. Particular attention was paid to the anatomy of the venous confluence. RESULTS: Twenty-seven cases had dominant right transverse sinuses, 18 had dominant left transverse sinuses, four had co-dominant transverse sinuses, and one had absence of both transverse sinuses. In 21 (51%) of 41 cases without occipital sinuses, absent or hypoplastic transverse sinuses were found. Nine patients had occipital sinuses. Five (56%) of nine patients with occipital sinuses were younger than 2 years, and patients younger than 2 years accounted for 24% of all patients (12 of 50 patients) in the study. In six (67%) of nine patients with occipital sinuses, absent or hypoplastic transverse sinuses were shown. Two patients had bulbous prominence of the vein of Galen. One had foreshortened superior sagittal sinus, which in turn is drained by two paramedian cortical veins. CONCLUSION: Understanding the normal anatomy of the cerebral venous system and its variants by using MR venography in children provided the background to future studies on anomalous venous structure in malformations of the brain.     

Physiologic variations in dural venous sinus flow on phase-contrast MR imaging

OBJECTIVE: Our study quantifies normal physiologic variations of dural sinus flow using phase-contrast MR imaging. SUBJECTS AND METHODS: Fifteen volunteers were imaged using nontriggered and triggered phase-contrast MR venography of the superior sagittal and transverse sinuses. Triggered scans were obtained during regular breathing; nontriggered scans were obtained during regular breathing, breath-holding, deep inspiratory breath-holding, and deep expiratory breath-holding. Analysis of variance, Bonferroni method, and Dunn post hoc analysis were used to determine any significant differences in the mean flow and velocity between the different breathing maneuvers. A paired t test was used to compare flow between sinuses during regular breathing. RESULTS: Deep inspiratory breath-holding and deep expiratory breath-holding resulted in a significant decrease in blood flow and velocity in all dural sinuses compared with regular breathing. During deep inspiratory breath-holding, blood flow decreased 30.8% in the superior sagittal sinus, 19.7% in the left transverse sinus, and 19.1% in the right transverse sinus. Similarly, during deep expiratory breath-holding, blood flow decreased 30.2% in the superior sagittal sinus, 20.8% in the left transverse sinus, and 20.3% in the right transverse sinus. The sum of the flow in the transverse sinuses was significantly greater than in the sagittal sinus. Normal pulsatility of dural sinus blood velocity was also characterized for all measured sinuses. CONCLUSION: Characterization of variations in dural sinus velocity and flow as a function of the cardiac cycle and breathing maneuvers, using phase-contrast MR imaging, may help separate physiologic from pathologic changes of flow resulting from conditions that influence the cerebrovascular circulation.     

2D time-of-flight MR venography in neonates: anatomy and pitfalls

BACKGROUND AND PURPOSE: The dural venous sinuses in neonates differ from those in adults or older children in that the caliber of venous sinuses is smaller and there is skull molding. The aim of this retrospective study is to evaluate the presence of flow gaps in venous sinuses in neonates on 2D time-of-flight (TOF) MR venography (MRV). METHODS: Fifty-one neonates underwent coronal 2D TOF MRV. Nine also had CT venography (CTV) for comparison. In 1 neonate, a further 2D TOF MRV was performed in the sagittal plane; in another neonate, images were captured in the axial plane; and in another, a further coronal TOF MRV with shorter echo time was performed. RESULTS: Flow gap was seen in the posterior aspect of the superior sagittal sinus in 35 of 51 (69%). Focal narrowing of the superior sagittal sinus, in the region of convergence of lambdoid sutures, was detected in 7 of 51 (14%). The right and left transverse sinuses demonstrated flow gap in 13 of 51 (25%) and 32 of 51 (63%) respectively. There was normal filling of contrast on CTV in the superior sagittal sinus, transverse sinus and sigmoid sinus in those cases with flow gap detected on coronal 2D TOF MRV. Right, left, and codominance of the transverse sinuses are as follows: 32 of 51 (63%), 5 of 51 (10%), and 14 of 51 (27%), respectively. The right and left sigmoid sinuses demonstrated flow gap in 7 of 51 (14%) and 8 of 51 (16%), respectively, and the left sigmoid sinus was absent in 1 of 51 (2%). CONCLUSION: The high proportion of flow gap in the venous sinuses of neonates, particularly of the superior sagittal sinus, could be attributed to the smaller caliber venous sinuses, slower venous flow, and skull molding.     

Intracranial venous system: gadolinium-enhanced three-dimensional MR venography with auto-triggered elliptic centric-ordered sequence--initial experience

PURPOSE: To evaluate gadolinium-enhanced three-dimensional auto-triggered elliptic centric-ordered (ATECO) magnetic resonance (MR) venography for imaging of the intracranial venous system. MATERIALS AND METHODS: ATECO MR venography was performed in 23 patients, eight of whom also underwent two-dimensional time-of-flight (TOF) MR venography for imaging of the intracranial venous system. Seventeen predefined venous structures were evaluated on all venograms by two neuroradiologists. Visualization of venous structures was defined as completely visible (including clearly pathologic), partially visible, or not visible. Readers were also asked to compare the visibility of these predefined structures on ATECO and TOF MR venograms, where available. RESULTS: Of the 23 patients, six had dural venous sinus disease. Of the remaining 17 healthy patients, five underwent both ATECO and TOF MR venography and 12 underwent ATECO MR venography alone. On ATECO MR venograms obtained in the healthy patients, visibility of the 17 predefined venous structures was complete in 92% (531 of 578) of evaluations. For the five normal TOF MR venograms, the rate of complete visibility of the same venous structures was 61% (104 of 170). The rate of complete visibility of the large dural venous sinuses was 99% for ATECO MR venograms and 75% for TOF MR venograms. CONCLUSION: ATECO MR venography provides high-quality images of the intracranial venous anatomy and was superior to TOF MR venography for consistent complete visibility of venous structures.     

Partially recanalized chronic dural sinus thrombosis: findings on MR imaging, time-of-flight MR venography, and contrast-enhanced MR venography

BACKGROUND AND PURPOSE: The imaging appearance of chronic, partially recanalized dural sinus thrombosis has been incompletely described. We sought to more fully characterize the imaging findings of this entity on MR imaging, time-of-flight MR venography (TOF-MRV), and elliptic centric-ordered contrast-enhanced MR venography (CE-MRV). Materials and METHODS: From a data base of patients with cerebral venous thrombosis, 10 patients were identified with imaging and clinical findings consistent with the diagnosis of chronic, partially recanalized, dural sinus thrombosis. All patients had MR imaging of the brain without and with contrast. Nine patients underwent MRV, and 6 had both CE-MRV and TOF-MRV. Thirty-four venous segments were thrombosed and were assessed in detail for multiple imaging features. RESULTS: Most thrombosed segments were isointense to gray matter on T1-weighted images (85%), and hyperintense to gray matter on T2-weighted images (97%). Visible serpiginous intrathrombus flow voids were visible in 23 segments (8/10 patients) corresponding with areas of flow signal intensity on TOF-MRV and enhancing channels on contrast MRV. Eighty-four percent of thrombosed segments enhanced equal to or greater than venographically normal venous sinuses. TOF-MRV and CE-MRV were abnormal in all patients, and CE-MRV more completely characterized the thrombosed segments. The imaging appearance did not change in those patients with follow-up imaging (average 13.6 months). CONCLUSION: Chronic, partially recanalized, venous thrombosis has a characteristic appearance on MR and MRV. CE-MRV was abnormal in all cases, despite the intense enhancement of the thrombosed segments. Because of the highly selected nature of the cases reported, further study is required to determine whether these findings are present in all cases of this condition.     

硬脑膜窦血栓形成磁共振成像诊断

目的　总结硬脑膜窦血栓形成 (DST)头颅MRI及MRV表现特点。方法　回顾分析 2 0例DST患者的MRI及MRV表现。结果　MRI典型表现为硬脑膜窦内正常流空效应消失 ,代之以异常等信号或高信号影。病变好发部位依次为横窦 -乙状窦、上矢状窦、直窦 ,部分患者伴有皮质引流静脉及脑深部大静脉受累。MRV示受累静脉窦全程或节段性闭塞 ,病变部位和范围与MRI所见基本一致。结论　MRI及MRV可直接识别血栓 ,是目前无创性诊断DST的最可靠方法。     

颅内静脉血栓形成的磁共振诊断

目的:探讨磁共振成像(MRI)及磁共振静脉成像(MRV)对颅内静脉窦血栓形成(CVST)的诊断价值。方法:回顾性分析经临床和影像学方法确诊的14例CVST患者。MR检查技术包括平扫,增强扫描及MRV,14例均行CT平扫,其中1例行DSA检查。结果:14例CVST累及上矢状窦血栓形成4例,横窦血栓形成6例、乙状窦5例,MRI可清晰显示颅内静脉窦血栓形成的直接征象和间接征象,MRV可显示受累静脉窦不显影或者充盈缺损形成。结论:常规MRI结合MRV对颅内静脉窦血栓形成的早期诊断具有重要价值。     

Normal structures in the intracranial dural sinuses: delineation with 3D contrast-enhanced magnetization prepared rapid acquisition gradient-echo imaging sequence

BACKGROUND AND PURPOSE: The potential pitfalls in the diagnosis of dural sinus thrombosis include the presence of arachnoid granulations, intrasinus fibrotic bands (so-called septa), and hypoplasia or aplasia of the dural sinuses. The purpose of this study was to assess the appearance, distribution, and prevalence of arachnoid granulations and septa in the dural sinuses by using a high resolution 3D contrast-enhanced magnetization prepared rapid acquisition gradient-echo (MPRAGE) imaging sequence. METHODS: Conventional MR images and contrast-enhanced MPRAGE images of 100 consecutive patients who had no abnormalities of the dural sinuses were retrospectively reviewed. The incidence, site, number, size, signal intensity, and shape of arachnoid granulations and septa within the sinuses and their relationship with adjacent veins were recorded. RESULTS: With 3D contrast-enhanced MPRAGE imaging, 433 round, oval, or lobulated focal filling defects were found in a total of 90 patients. Curvilinear septa were observed in 92 patients. Sixty-nine patients had round, oval, or lobulated defects in the transverse sinus, 59 had such defects in the superior sagittal sinus, and 47 had such defects in the straight sinus. All except two of the above defects were isointense relative to CSF on all images. These structures were presumed to be arachnoid granulations. Of 431 arachnoid granulations, 233 (53.8%) were located in the superior sagittal sinus, 122 (28.1%) in the transverse sinus, and 76 (17.6%) in the straight sinus. One or more veins were seen to enter arachnoid granulations in 414 (96%) instances. CONCLUSION: The contrast-enhanced 3D MPRAGE imaging sequence showed a much higher prevalence and a different distribution of arachnoid granulations and septa within dural sinuses than have been observed in previous radiologic studies. Arachnoid granulations were closely related spatially to veins.     

Normal appearance of arachnoid granulations on contrast-enhanced CT and MR of the brain: differentiation from dural sinus disease.

PURPOSETo determine the imaging appearance and frequency with which arachnoid granulations are seen on contrast-enhanced CT and MR studies of the brain.METHODSWe retrospectively reviewed 573 contrast-enhanced CT scans and 100 contrast-enhanced MR studies of the brain for the presence of discrete filling defects within the venous sinuses. An anatomic study of the dural sinuses of 29 cadavers was performed, and the location, appearance, and histologic findings of focal protrusions into the dural sinus lumen (arachnoid granulations) were assessed and compared with the imaging findings.RESULTSDiscrete filling defects within the dural sinuses were found on 138 (24%) of the contrast-enhanced CT examinations. A total of 168 defects were found, the majority (92%) within the transverse sinuses. One third were isodense and two thirds were hypodense relative to brain parenchyma. Patients with filling defects were older than patients without filling defects (mean age, 46 years versus 40 years). Discrete intrasinus signal foci were noted on 13 (13%) of the contrast-enhanced MR studies. The foci followed the same distribution as the filling defects seen on CT scans and were isointense to hypointense on T1-weighted images, variable in signal on balanced images, and hyperintense on T2-weighted images. Transverse sinus arachnoid granulations were noted adjacent to venous entrance sites in 62% and 85% of the CT and MR examinations, respectively. Arachnoid granulations were found in 19 (66%) of the cadaveric specimens, in a similar distribution as that seen on the imaging studies.CONCLUSIONDiscrete filling defects, consistent with arachnoid granulations, may be seen in the dural sinuses on 24% of contrast-enhanced CT scans and on 13% of MR studies. They are focal, well-defined, and typically located within the lateral transverse sinuses adjacent to venous entrance sites. They should not be mistaken for sinus thrombosis or intrasinus tumor, but recognized as normal structures.     

The anterior medullary–anterior pontomesencephalic venous system and its bridging veins communicating to the dural sinuses: normal anatomy and drainage routes from dural arteriovenous fistulas

Introduction  We evaluated the normal venous anatomy of the anterior medullary/anterior pontomesencephalic venous (AMV/APMV) system and bridging veins connected to the dural sinuses using magnetic resonance (MR) imaging and demonstrated cases of dural arteriovenous fistulas (DAVFs) with bridging venous drainage. Materials and methods  MR images obtained using a 3D gradient echo sequence in 70 patients without lesions affecting the deep or posterior venous channels were reviewed to evaluate the normal anatomy of the AMV/APMV system and bridging veins. MR images and digital subtraction angiography in 80 cases with intracranial or craniocervical junction DAVFs were reviewed to evaluate the bridging venous drainage from DAVFs. Results  MR images clearly revealed AMV/APMV in 35 cases. Fifteen cases showed a direct connection between AMV and APMV, while 15 cases showed an indirect communication via the transverse pontine vein or the bridging vein. In the five remaining cases, the AMV and APMV end separately to the bridging vein or the transverse pontine vein. Bridging veins were identified in 34 cases, connecting to the cavernous sinus in 33, to the suboccipital cavernous sinus in 11, and the inferior petrosal sinus in five cases. In 80 DAVF cases, seven of 40 cavernous sinus DAVFs, two craniocervical junction DAVFs, and one inferior petrosal sinus DAVF drained via bridging veins to the brain stem. Conclusion  The AMV/APMV and bridging veins showed various anatomies and frequently showed a connection to the cavernous sinus. Knowledge of the venous anatomy is helpful for the diagnosis and intravascular treatment of DAVFs.     

Follow-up MRI in dural arteriovenous malformations involving the cavernous sinus: emphasis on detection of venous thrombosis

Summary Six patients with a dural arteriovenous malformation (dural AVM) involving the cavernous sinus were followed up with magnetic resonance imaging in order to assess change in the lesions. Spin-echo (SE) imaging of three patients in whom the AVM appeared to have closed at least 1 month earlier (two of them spontaneously, and one after external carotid artery embolization) showed neither apparent flow void in the involved cavernous sinus nor evidence of venous thrombosis. SE images of the other three patients who had not been cured by external carotid artery embolization (two of whom were examined within a week of treatment), detected persisting arteriovenous shunts, including high-flow cortical venous drainage, seen as flow void. Two-dimensional time-of-flight MR angiography (2D TOF MRA) was performed simultaneously in three patients. Whereas shunting blood and the normal cavernous sinus were of high intensity, presumed thrombosed cavernous sinuses were isointense with stationary brain tissue. SE imaging can confirm the resolution of arteriovenous shunts, but poorly delineates ver acute and chronic thrombosis of the draining veins. In contrast, 2D TOF MRA directly demonstrates flowing blood, permitting the diagnosis of venous thrombosis; it should be included in follow-up of a dural AVM involving the cavernous sinus when venous thrombosis is suspected.     

Hypointense thrombus on T2-weighted MR imaging: a potential pitfall in the diagnosis of dural sinus thrombosis.

Purpose: To determine the frequency of hypointense appearance of dural sinus thrombosis on T2-weighted images, which may mimic a normal flow void, and when possible correlate with appearance on T1-weighted images. Methods and Materials: Retrospective review of radiology files showed 51 patients with a discharge diagnosis of dural sinus thrombosis who underwent MR imaging during the period 1986-1998. These images were reviewed by an experienced neuroradiologist for appearance on T2-weighted images. This process yielded five cases in which a hypointense appearance on this pulse sequence simulated a normal flow void. An additional two cases were added from the teaching files of two other institutions giving a total of seven cases (13% of studies). The resulting study population consisted of five women and two men (mean age 27.1 years). T1 weighted images were available in five patients. In two patients MR venography was available, but not T1-weighted images. The diagnosis of dural sinus thrombosis was based solely on absence of flow void on T1-weighted images in one case, solely on absence of flow void on MR venography in two cases and absence of flow void on T1-weighted images in conjunction with MR venography or gradient echo findings in 4 patients. All images were obtained on a 1.5 T magnet (GE Medical Systems; Milwaukee, Wisconsin). Results: In all patients hypointense signal of thrombus was isointense with normal flow voids in other dural sinuses on T2-weighted images. In all cases in which T1-weighted images were available, the signal intensity of thrombus was isointense to gray matter. Conclusion: Hypointense appearance of thrombus on T2-weighted images is a potential pitfall in the MR diagnosis of dural sinus thrombosis. Because thrombus in this stage of evolution appears isointense to gray matter on T1-weighted images, careful attention must be paid to other sequences to avoid this pitfall.     

Utility of contrast-enhanced 3D turbo-flash MR angiography in evaluating the intracranial venous system

The objective of this study was to compare the effectiveness of contrast-enhanced 3D turbo-flash and 2D time-of-flight (TOF) magnetic resonance angiography (MRA) sequences in the visualization and evaluation of the intracranial venous system. A prospective study was carried out on 41 patients referred to our Magnetic Resonance Imaging (MRI) unit with clinical findings suggestive of dural sinus thrombosis. Contrast-enhanced 3D turbo-flash and 2D TOF MRA sequences were performed, and the dural sinuses and cerebral veins were classified into five grades according to the quality of visualization and presence of thrombosis. We found the dural sinuses and cerebral veins to be normal in all sequences in 31 patients. Thrombosis of dural sinuses was detected in ten patients, with four of these ten cases found only in the contrast-enhanced 3D turbo-flash sequence. In general, complete visualization of cerebral veins and dural sinuses was significantly better accomplished with contrast-enhanced 3D turbo-flash MRA than with 2D TOF in either coronal or sagittal/oblique planes. Although 2D TOF MRA may be superior in detecting chronic dural sinus thrombosis, contrast-enhanced 3D turbo-flash MRA sequences may offer advantages for the early diagnosis and management of acute and subacute dural sinus thrombosis.     

Vascular hydraulics associated with idiopathic and secondary intracranial hypertension

BACKGROUND AND PURPOSE: The radiologic diagnosis of idiopathic intracranial hypertension (IIH) is one of exclusion, with no reproducible positive features described in the imaging literature. Because MR venography is prone to flow artifacts, diagnosis of secondary intracranial hypertension (SIH) can also be problematic. Vascular hydraulics can be useful for diagnosis of these conditions when measured by invasive or sonographic means. The purpose of this study was to measure vascular flow and pulsatility characteristics with a noninvasive MR imaging method. METHODS: Twelve patients with clinical and lumbar puncture findings of IIH or SIH and 12 control subjects were examined with MR venography and MR flow quantification studies of the cerebral arteries and veins. Total cerebral, superior sagittal sinus (SSS), and straight sinus blood flows were measured. Pulsatility indices from the arterial and venous flow for all patients were compared using the Student t test. RESULTS: MR venography confirmed that seven of the 12 patients had venous outflow obstruction, and thus, SIH. The remaining five patients had IIH. All patients showed reduced sinus pulsatility compared with that of the control group; reductions of 42% in the SSS and 32% in the straight sinus were noted (P =.0001 and.005, respectively). In the IIH group, total blood flow was 46% higher than that in the control group (P =.0002), and SSS flow was normal. In the SIH group, total blood flow was normal; however, SSS flow was reduced by 25% (P =.003). CONCLUSION: Reduced venous sinus pulsatility is a marker of intracranial hypertension secondary to raised venous sinus pressure. When suspicion of IIH or SIH exists and the MR venogram is difficult to interpret, raised total blood flow indicates IIH, whereas reduced SSS flow indicates SIH.     

Relation between intraocular pressure and size of transverse sinuses

There are asymmetries in the sizes of transverse sinus and intraocular pressure. The purpose of this study was to investigate possible relationships between the asymmetry of transverse sinuses in TOF MR venography and intraocular pressures of right and left eyes. In this study, subjects were 63 male and 42 female medical school students, aged 18–21 years (mean±SD; 19.72±0.67 years). Subjects with neurological and ophthalmologic disease, particularly dural sinus thrombosis, myopia, trauma and glaucoma, were excluded the study. Subjects were divided into five groups according to the magnitudes of the right- and left-transverse sinuses in MR venography results. There is a functional relation between intraocular pressures of the right and left eyes and asymmetry of the transverse sinus. If the transverse sinus on one side is larger and its venous drainage is greater, the intraocular pressure of the eye on this side is lower. It can be speculated that the transverse sinus size may be associated with pathogenesis of diseases with increased intraocular pressure such as glaucoma. We aim to determine the relation between the size and drainage of transverse sinuses in TOF MR venography and intraocular pressure in patients with open-angle glaucoma in our next study.