Nonenhanced ECG-gated time-resolved 4D steady-state free precession (SSFP) MR angiography (MRA) of cerebral arteries: comparison at 1.5T and 3T

Purpose

To compare image quality of nonenhanced time-resolved 4D steady-state free precession MR angiography (4D SSFP MRA) of cerebral arteries at 1.5 T and 3 T.

Materials and methods

12 healthy subjects (mean age 29.4 ± 6.9 years) were studied at both 1.5 T and 3 T. Two different positions of the acquisition slab were evaluated; in one acquisition the imaging slab included the carotid siphon (“S_low”), in the other acquisition the imaging slab was placed superior to the carotid siphon (“S_high”). Subjective image quality of cerebral arteries was assessed independently by two readers on a 4-point scale. Relative Signal-to-Noise-Ratio (SNR) was determined for the M1 segment of the middle cerebral artery.

Results

Subjective image quality of the anterior cerebral artery (segments A1, A2) was significantly higher at 1.5 T as compared to 3 T, while 3 T provided significantly higher image quality for segment P3 of the posterior cerebral artery. For the middle cerebral artery (segments M1–M3), image quality was significantly higher at 1.5 T than at 3 T when the carotid siphon was included in the acquisition slab (“S_low”), while no significant difference was found between 1.5 T and 3 T with “S_high”. Relative SNR was significantly higher at 1.5 T (23.1 ± 5.1) as compared to 3 T (12.1 ± 7.8) for “S_low” and significantly higher at 3 T (29.8 ± 5.9) than at 1.5 T (24.2 ± 3.6) for “S_high”.

Conclusion

Our results indicate that 4D SSFP MRA should preferably be performed at 1.5 T with inclusion of the carotid siphon in the acquisition slab, which might be required for the assessment of intracranial collateral flow.