Usefulness of subtraction of 3D T2WI-DRIVE from contrast-enhanced 3D T1WI: preoperative evaluations of the neurovascular anatomy of patients with neurovascular compression syndrome.

BACKGROUND AND PURPOSE High-resolution 3D MR cisternography techniques such as 3D T2WI-driven equilibrium radiofrequency reset pulse (DRIVE) are used preoperatively to assess neurovascular anatomy in patients with neurovascular compression syndrome, but contrast between vessels and cranial nerves at the point of neurovascular contact is limited. The postprocessing technique subtraction of 3D T2WI-driven equilibrium radiofrequency reset pulse from contrast-enhanced 3D T1WI (sDRICE) provides both high spatial resolution and excellent contrast in depicting the neurovascular contact. We evaluated the usefulness of sDRICE compared with 3D T2WI-DRIVE. MATERIALS AND METHODS Twelve patients who underwent microvascular decompression for hemifacial spasm or trigeminal neuralgia were examined preoperatively with 3D T2WI-DRIVE and sDRICE. Two neuroradiologists retrospectively analyzed and scored lesion conspicuity, defined as the ease of discrimination between offending vessels and compressed nerves or the brain stem at the neurovascular contact. They also quantitatively analyzed the contrast and contrast-to-noise ratio at the neurovascular contact. RESULTS The lesion conspicuity scores of sDRICE images were significantly higher than those of 3D T2WI-DRIVE for all 12 patients (P = .006) and the 6 cases of hemifacial spasm (P = .023) but were not significantly higher in the 6 trigeminal neuralgia cases alone (P = .102). For all 12 patients, the contrast-to-noise ratio between the offending vessels and the brain stem and between the vessels and nerves on sDRICE images was significantly higher than that on 3D T2WI-DRIVE (P = .003 and P = .007, respectively). Among these structures, the contrast values were also significantly higher on the sDRICE than on the 3D T2WI-DRIVE (P < .001) images. CONCLUSIONS The postprocessing technique sDRICE is useful to evaluate neurovascular anatomy and to improve contrast and the contrast-to-noise ratio in patients with neurovascular compression syndrome.