Magnetic resonance venography of intracranial venous diseases.

289 Over the past decade, neurologists and neuroradiolo-gists have paid increasing attention to the role of the intracranial venous system in cerebrovascular diseases, such as dural sinus steno-occlusive diseases. The intra-cranial venous system has been evaluated traditionally during the venous phase of conventional catheter digital subtraction angiography (DSA). In fact, DSA is still the gold standard investigation of intracranial venous anatomy and the most definitive diagnostic technique for intracranial venous disease. The advantages of DSA include widespread availability, excellent spatial resolution , familiarity of the images to clinicians, and, most importantly, its inherent option of endovascular intervention and thrombolysis for cerebral venous thrombosis. However, DSA is an invasive procedure with well-known associated risks such as cerebral infarction, vascular wall injury and hematoma at the puncture site. 1 A short post-procedural hospital stay, radiation exposure, allergic or nephrotoxic effects of iodinated contrast medium, and the limitations of 2-dimensional (2D) planar imaging are additional disadvantages. 2 For these reasons, the use of noninvasive imaging techniques in the evaluation of the intracranial venous system is gradually increasing. Noninvasive imaging techniques include cerebral computed tomographic venography (CTV) and magnetic resonance venography (MRV). Widespread availability and a more rapid image acquisition which reduces the effect of patient-related motion artifacts are the advantages of CTV over MRV. However, CTV is similar to catheter DSA in requiring the use of iodin-ated contrast medium and radiation exposure. CTV also requires complex post-processing to remove the bony structures from the reconstructed images; thus, visualization of skull base structures is limited. 2,3 Therefore, CTV always provides a supportive role while there is increasing reliance on MRV. 2 In spite of the disadvantages of decreased spatial resolution, slightly lower sensitivity and specificity for vascular patency relative to DSA, contraindications to magnetic resonance (MR) imaging study such as pacemaker and ferromagnetic foreign bodies in critical locations (e.g. eye, brain and lung), MRV is still the current method of choice for imaging the intracranial venous system. Although individual MRV techniques have some artifacts and potential diagnostic pitfalls, 2–7 good correlation has been shown between MRV and DSA. 4 There are 3 magnetic resonance angiography (MRA) methods commonly available for evaluating the intracranial venous system: 2D time-of-flight (TOF), 3-dimensional (3D) phase-contrast (PC) and 3D gadolinium-enhanced (GE) pulse sequences. 2D TOF MRA is based on the principle of flow-related enhancement and highlights differences in magneti-zation between nuclei in flowing blood and those in stationary tissue. …