Body MR venography

MRV offers unique diagnostic possibilities for detection and characterization of venous disease. It allows evaluation of perivascular and vascular anatomy, evolution of thromboembolic events, and assessment of vascular flow. MRI is a diagnostic tool that can be tailored for a variety of clinical dilemmas, not only DVTs. Continued improvements in hardware and software will expand the role of MRV.     

Cerebral MR venography

This paper illustrates the technique and clinical use of cerebral MR venography (MRV). Dural sinus thrombosis is detected by both two-dimensional time-of-flight (TOF) and three-dimensional phase-contrast (PC) techniques. Venous angiomas are demonstrated by the three-dimensional PC method. The arterial feeders, nidus and draining veins of cerebral arteriovenous malformation (AVM) can be visualized on contrast-enhanced TOF three-dimensional MR angiogram. The high-flow draining veins of cerebral and dural AVMs, vein of Galen malformation and carotid cavernous fistula are better seen on contrast-enhanced three-dimensional gradient-echo MRV.     

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.     

Gd-enhanced subtraction MR venography

We succeeded in distinctly imaging the calf veins using Gd-enhanced subtraction MR venography (Gd SMRV). Gd SMRV was performed in 15 normal legs, 33 varicose legs and 22 legs with suspected deep venous thrombosis. Conventional venography was performed in 46 legs in all. The deep veins of the calf, greater saphenous vein, and intramuscular veins had high rates of demonstration in normal legs and varicose legs (84, 100%, 87, 97%, 67, 73%). The varices were also well demonstrated (100%). When Gd SMRV was compared with conventional venography in terms of diagnosis of calf venous thrombosis, the sensitivity of this method was 100%, specificity was 92% and accuracy was 93%. We found high intensity thrombi on precontrast images in most cases, a finding that was important for the diagnosis of local thrombi. This method was non-invasive and was able to clearly visualize veins in the calf. We concluded that Gd SMRV was useful for calf venous disease, especially calf venous thrombosis.     

Cerebral venography with MR

The authors describe a two-dimensional time-of-flight magnetic resonance (MR) angiography technique to create projection venograms of the head. The technique was applied to 27 healthy volunteers and 39 patients. The superior sagittal and straight sinuses, the internal cerebral veins, and the Galen vein were visualized in all the volunteers. Other veins were seen in a high percentage of subjects. Systematic comparison of digital subtraction angiography (DSA) after intraarterial contrast medium injection and MR venography in patients showed good correlation between the two techniques. MR venography proved helpful in identifying thrombosis or patency of cerebral veins and sinuses and showed collateral venous drainage and venous drainage from arteriovenous malformations. There was good correlation between conventional contrast angiography and MR venography. In conclusion, MR venography is considered reliable for showing the cerebral venous system and provides information additional to that of conventional spin-echo imaging.     

MR venography of multiple sclerosis

BACKGROUND AND PURPOSE: The distribution of multiple sclerosis (MS) lesions in the brain follows a specific pattern, with most lesions in the periventricular regions and in the deep white matter; histopathologic studies have shown a perivenous distribution. The aim of this study was to illustrate these distribution patterns in vivo using high-resolution MR venography. METHODS: Seventeen MS patients underwent MR imaging at 1.5 T. Venographic studies were obtained with a 3D gradient-echo technique. MS lesions were identified on T2-weighted images, and their shape, orientation, and location were compared with the venous anatomy on the venograms. RESULTS: The use of contrast material facilitated the visualization of small veins and increased the number of veins seen. A total of 95 MS lesions could be identified on both the T2-weighted series and the venograms; a central vein was visible in all 43 periventricular lesions and in all but one of the 52 focal deep white matter lesions. The typical ovoid shape and orientation of the long axis of the MS lesions correlated well with the course of these veins. CONCLUSION: With MR venography, the perivenous distribution of MS lesions in the brain can be visualized in vivo. The venous anatomy defines the typical form and orientation of these lesions.     

Dynamic MR venography: an intrinsic benefit of time-resolved MR angiography

PURPOSE: To investigate the possibility of obtaining dynamic contrast-enhanced magnetic resonance venography (DCE-MRV) images of the lower extremities. MATERIALS AND METHODS: Peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) was performed on 20 patients using a time-resolved sequence that combined undersampled projection reconstruction (PR) in-plane and Cartesian slice encoding through-plane. The contrast dynamics of distal vessels were depicted. An automated segmentation algorithm based on a contrast arrival time (CAT) threshold was used to generate contrast dynamics in the venous system. The signal difference between the vein and artery was measured to evaluate the effectiveness of this technique in isolating the venous contrast dynamics. RESULTS: The automatically generated image series depicted the contrast dynamics of both the arterial and venous systems, including asymmetric venous enhancement and background tissue enhancement. Quantitative measurement showed a mean venous/arterial signal ratio increase from 1.58 to 4.82 for the peak venous frame after arterial signal suppression. CONCLUSION: DCE-MRV is a minimally invasive technique for evaluating the venous side of the systemic vascular anatomy. Time-resolved MRA has the potential clinical benefit of enabling both arterial and venous disease to be detected in patients undergoing CE-MRA.     

Fast contrast-enhanced MR whole-brain venography

Our aim was to assess the value of a new fast contrast-enhanced MR venography (CE-MRV) sequence in the investigation of normal and diseased cerebral veins. Conventional time-of-flight (TOF) MRV is time consuming, with imaging for a single sequence taking many minutes. MRI was performed with a clinical 1.5-T scanner; conventional TOF MRV followed by CE-MRV was performed using a modified 3D first-pass MR angiography sequence. Ten control subjects without cerebral pathology were studied as well as ten patients with cerebral venous thrombosis for a total of 20 studies with both sequences. CE-MRV was able to provide a set of complete MRV images in a significantly shorter time than conventional MRV sequencing could. The field of view also provided greater coverage of the vessels of the head and neck. CE-MRV also provided more extensive small vein detail and provided a better demonstration of intraluminal defects, despite a slightly lower resolution. Both methods were equally suited for the demonstration of venous thrombosis and demonstrated all cases equally well; however, CE-MRV provided more detailed information by showing partially obstructed sinuses and by showing better the presence of cortical collateral venous drainage.     

Effort-induced thrombosis: diagnosis with three-dimensional MR venography

A case of Paget-von Schr?tter syndrome diagnosed with gadolinium-enhanced magnetic resonance (MR) venography is described. MR enabled a comprehensive evaluation with identification of the thrombus within the left subclavian vein and a hypertrophied anterior scalene muscle as the probable cause of the patient's condition. We describe the MR venography technique used for evaluation of the subclavian vein and the imaging findings in this entity.     

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.     

Cerebral MR venography: normal anatomy and potential diagnostic pitfalls

BACKGROUND AND PURPOSE: MR venography is often used to examine the intracranial venous system, particularly in the evaluation of dural sinus thrombosis. The purpose of this study was to evaluate the use of MR venography in the depiction of the normal intracranial venous anatomy and its variants, to assess its potential pitfalls in the diagnosis of dural venous sinus thrombosis, and to compare the findings with those of conventional catheter angiography. METHODS: Cerebral MR venograms obtained in 100 persons with normal MR imaging studies were reviewed to determine the presence or absence of the dural sinuses and major intracranial veins. RESULTS: Systematic review of the 100 cases revealed transverse sinus flow gaps in 31% of the cases, with 90% of these occurring in the nondominant transverse sinus and 10% in the codominant transverse sinuses. No flow gaps occurred in the dominant transverse sinuses. The superior sagittal and straight sinuses were seen in every venogram; the occipital sinus was seen in only 10%. The vein of Galen and internal cerebral veins were also seen in every case; the basal veins of Rosenthal were present in 91%. CONCLUSIONS: Transverse sinus flow gaps can be observed in as many as 31% of patients with normal MR imaging findings; these gaps should not be mistaken for dural sinus thrombosis.     

Projection arteriography and venography: initial clinical results with MR

Motion currently limits the applications of magnetic resonance (MR) angiography in certain regions of the body. To overcome this problem, a series of breath-hold, two-dimensional, flow-compensated gradient-echo images were acquired. These images were then processed by means of the maximum intensity projection algorithm to produce projection angiograms. The method was evaluated in 10 healthy subjects and in 12 patients and validated by comparing conventional angiograms, contrast material-enhanced computed tomographic scans, and duplex sonograms with MR projection arteriograms and venograms of the chest, abdomen, and pelvis. The aorta and pulmonary arteries and their branches were demonstrated, as was detailed anatomy of the hepatic and portal venous systems and inferior vena cava. Renal arteries and veins could be studied in both native and transplanted kidneys. The method permits determination of flow direction and differentiation of arteries and veins and is superior to three-dimensional acquisition techniques for imaging slow blood flow. Initial results suggest that the method may have clinical applications for a variety of vascular disorders.     

Direct contrast-enhanced 3D MR venography

Non-enhanced two-dimensional (2D) time-of-flight (TOF) MRA is well established for imaging of the deep venous system. However, based on the acquisition of multiple axial images, it can be time-consuming and often fails to delineate small superficial and perforating veins. The presented low-dose, direct-contrast-injection 3D MR venography technique allows rapid acquisition of high-quality MR venograms and can be employed for the display of the deep and superficial venous system of upper and lower extremity including pelvic and central thoracic veins. This article describes the employed technique and provides a comprehensive image-based overview of the various indications for direct-infusion 3D MR venography such as post-/thrombotic changes, varicosities, and assessment of the greater saphenous vein prior to bypass surgery. Received: 17 March 2000 Revised: 16 June 2000 Accepted: 19 June 2000     

High-resolution MR venography at 3.0 Tesla

PURPOSE: The aim of this study was to investigate the visualization of small venous vessels in the normal human brain at a field strength of 3 Tesla. METHODS: T2*-weighted, three-dimensional gradient-echo images were acquired by exploiting the magnetic susceptibility difference between oxygenated and deoxygenated hemoglobin in the vasculature and microvasculature. The spatial resolution was 0.5 x 0.5 x 1 mm3, and sequence parameters were varied to obtain good vessel delineation. Improved visibility of venous vessels was obtained by creating phase mask images from the magnetic resonance phase images and multiplying these by the magnitude images. Venograms were created by performing a minimum intensity projection over targeted volumes. RESULTS: Highly detailed visualization of venous structures deep in the brain and in the superficial cortical areas were obtained without administration of an exogenous contrast agent; compared with similar studies performed at 1.5 T, the echo time could be reduced from typically 40-50 ms to 17-28 ms. CONCLUSION: Imaging at high-field strength offers the possibility of improved resolution and the delineation of smaller vessels compared with lower field strengths.     

MR venography in the pediatric patient

BACKGROUND AND PURPOSE: Little is known about age-related changes in posterior fossa venous anatomy on 2D time-of-flight MR venography (MRV) or about artifacts that limit its accuracy in diagnosing venous occlusive disease. We evaluated pediatric appearances of posterior fossa venous drainage. METHODS: One hundred and eight children with normal MR imaging or minimal congenital anomalies underwent 2D MRV. Transverse sinus dominance and absence and the presence of an occipital sinus were correlated with age. Venous structure conspicuity was compared on source and maximum intensity projection images. RESULTS: Right, left, and codominance of the transverse sinus, respectively, was as follows: at < 25 months, 37%, 21%, and 42%; 25 months to 5 years, 35%, 30%, 35%; and > or =6 years, 50%, 16%, 34%. Transverse sinus dominance was not related to age between the three groups (P=.58, chi-square contingency), but some relationship was observed when patients <6 years were compared to those > or =6 years (P=.032). Chi-square trends showed a mildly positive correlation between age and an absent transverse sinus (P=.026) and a decreasing trend in the presence of an occipital sinus with age (P=.038). Saturation effects due to in-plane/slow flow were worse in patients <25 months; effects in the transverse sinuses or internal jugular veins were miminized with coronal or axial imaging, respectively. CONCLUSION: 2D TOF MRV shows age-related changes in venous anatomy. Caution should be used before posterior fossa venous occlusive disease is diagnosed on the basis of signal intensity loss, especially in neonates and young infants.     

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.