Intracranial stenoocclusive disease: MR angiography with magnetization transfer and variable flip angle

To assess time-of-flight MR angiography that uses magnetization transfer contrast (MTC) pulses, tilted optimized nonsaturating excitation (TONE), and a 256 x 512 image matrix for the detection of small intracranial arteries and for the detection and quantification of intracranial arterial stenoocclusive disease.

To assess anatomic sensitivity, six interpreters, in a blinded fashion, reviewed the MTC/TONE MR angiograms and selective intraarterial angiograms obtained in 70 patients within a mean interval of 5.5 days (SD, 1.5). In addition, all intracranial angiograms were evaluated with regard to presence and degree of arterial stenosis and anatomic variants.

Interobserver correlations for determining vessel length were comparably high for both methods. A strong correlation was found between measurements obtained on MR angiograms and those obtained on intraarterial angiograms. The mean vascular length averaged across all arteries was 34.8 mm (SD, 28.1) on MR angiograms and 53.2 mm (SD, 36.8) on intraarterial angiograms. Forty-one stenoses and occlusions and 30 anatomic variants were identified with intraarterial angiography. All arterial variants and 100% of occluded vessels were graded correctly. Moreover, 80% of stenoses greater than 70% and 88% of stenoses less than 70% were quantified correctly at MR angiography. Specificity for identifying stenotic disease was 99%.

Despite inferior display of vessel length, MTC/TONE MR angiography with increased spatial resolution was able to show the vast majority of high grade lesions visible at selective intraarterial angiography and may suffice for clinical decision making in many patients.