MRvenografi

MR venography (MRV) is a magnetic resonance imaging technique used to visualize the venous system. It is commonly performed as part of MR angiography protocols or as a standalone study to assess venous anatomy and pathology, particularly in the brain and neck. MRV can be performed without contrast using time-of-flight (TOF) or phase-contrast (PC) methods, or with gadolinium-based contrast in contrast-enhanced MRV (CE-MRV). Time-resolved CE-MRV provides dynamic information about venous filling.

Indications for MRV include suspected cerebral venous sinus thrombosis (CVST), evaluation of congenital or acquired venous anomalies, assessment of venous drainage prior to neurosurgical or radiosurgical planning, evaluation of venous involvement in tumors or vascular malformations, and investigation of unexplained intracranial hypertension.

Technique and interpretation emphasize suppressing arterial signals and highlighting venous blood. Non-contrast TOF MRV relies on flow-related enhancement, while PC MRV encodes velocity to visualize veins. CE-MRV uses gadolinium to shorten T1 relaxation of blood and produce high-resolution venous imaging, with 3D acquisitions offering detailed views of the dural sinuses and cerebral veins. Limitations include signal loss or pseudo-stenosis from slow or disturbed flow, susceptibility and motion artifacts, and reduced ability to quantify flow. Contraindications to gadolinium-based contrast apply in cases of severe renal impairment, and there are ongoing considerations regarding gadolinium retention in some patients.

Compared with CT venography, MRV avoids ionizing radiation and iodinated contrast but may require longer imaging times and be more sensitive to motion. MRV findings are interpreted in the clinical context and often complement other imaging studies to diagnose venous disorders or guide treatment.