Contrast-enhanced time-resolved 3-D MRA: applications in neurosurgery and interventional neuroradiology

The decision-making process in the endovascular treatment of cranial dural AV fistulas and angiomas and their follow-up after treatment is usually based on conventional digital subtraction angiography (DSA). Likewise, acquiring the vascular and hemodynamic information needed for presurgical evaluation of meningiomas may necessitate DSA or different MR-based angiographic methods to assess the arterial displacement, the location of bridging veins and tumor feeders, and the degree of vascularization. New techniques of contrast-enhanced MR angiography (MRA) permit the acquisition of images with high temporal and spatial resolution. The purpose of this study was to evaluate the applicability and clinical use of a newly developed contrast-enhanced 3-D dynamic MRA protocol for neurointerventional and neurosurgical planning and decision making.

With a 3-T whole-body scanner (Philips Achieva), a 3-D dynamic contrast-enhanced (MultiHance, Bracco) MRA sequence with parallel imaging, and intelligent k-space readout (keyhole and "CENTRA" k-space filling) was added to structural MRI in patients with meningiomas, dural arteriovenous fistulas and pial arteriovenous malformations. The sequence had a temporal resolution of 1.3 s per 3-D volume with a spatial resolution of 0.566x0.566x1.5 mm per voxel in each 3-D volume and lasted 25.2 s. DSA was performed in selected patients following MRI.

In patients with arteriovenous fistulas and malformations, MRA allowed the vascular shunt to be identified and correctly classified. Hemodynamic characteristics and venous architecture were clearly demonstrated. Larger feeding arteries could be identified in all patients. In meningiomas, MRA enabled assessment of the displacement of the cerebral arteries, depiction of the tumor feeding vessels, and evaluation of the anatomy of the venous system. The extent of tumor vascularization could be assessed in all patients and correlated with the histopathological findings that indicated hypervascularization.

High temporal and spatial resolution 3-D MRA may allow correct identification and classification of fistulas and angiomas and help to reduce the number of pre-or postinterventional invasive diagnostic angiograms. This sequence is also helpful for characterizing the degree of vascularization in preoperative evaluation of meningiomas and to select meningiomas suitable for embolization. Displacement of normal arteries and depiction of the venous anatomy can be achieved cost-effectively in a short period of time. The high spatial resolution also permits improved demonstration of the major feeding arteries, which helps to reduce the number of conventional angiograms required for meningioma evaluation.