Three-dimensional, T1-weighted gradient-echo imaging of the brain with a volumetric interpolated examination

Abstract

Background and purpose: T1-weighted, 3D gradient-echo MR sequences can be optimized for rapid acquisition and improved resolution through asymmetric k-space sampling and interpolation. We compared a volumetric interpolated brain examination (VIBE) sequence with a magnetization-prepared rapid acquisition gradient echo (MP RAGE) sequence and a 2D T1-weighted spin-echo (SE) sequence.

Methods: Thirty consecutive patients known or suspected to have focal brain lesions underwent postcontrast studies (20 mL of gadopentetate dimeglumine) with VIBE, MP RAGE, and 2D T1-weighted SE imaging. Source and 5-mm VIBE and MP RAGE reformations, and 5-mm T1-weighted SE images were compared qualitatively and by using signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). SNRs in a gadolinium-doped water phantom were also measured for all three sequences.

Results: On the source images, SNRs for gray matter (GM) and white matter (WM), and CNRs for WM-to-GM and contrast-enhancing lesion-to-GM were slightly, but significantly higher for the VIBE sequence than for the MP RAGE sequence (P <.05). On 5-mm reformations, WM-to-GM CNR was significantly higher on VIBE and MP RAGE images than on T1-weighted SE images (P <.001), but contrast-enhancing lesion-to-GM CNRs were higher on SE images compared with both gradient-echo sequences (P <.001). Qualitatively, VIBE images showed fewer flow artifacts than did SE and MP RAGE images (P <.05). In the phantom, VIBE SNR was higher than MP RAGE SNR for short T1 relaxation times.

Conclusion: VIBE provides an effective, alternative approach to MP RAGE for fast 3D T1-weighted imaging of the brain.

Fig 1.

SNR measurements obtained on a phantom for T1 values between 5 and 1000 ms for the 5-mm VIBE and MP RAGE reformations and the T1-weighted SE images.

Fig 2.

Images of the posterior fossa in a patient with suspected metastatic disease. A, Two-dimensional T1-weighted SE image shows marked pulsation artifacts. Superimposition of the choroidal plexus in the fourth ventricle and the artifacts mimic a possible contrast-enhancing lesion (arrow). B, MP RAGE 5-mm reformation shows considerable ghost artifacts (arrows) impairing visualization of the pons and the cerebellum. C, VIBE 5-mm reformation shows no artifact.

Fig 3.

Primary cerebral lymphoma. A–C, Interhemispheric contrast-enhancing lesion (arrow in A) is well visualized on both the 2D T1-weighted SE image (A) and the VIBE 5-mm reformation (B), but is less obvious on the MP RAGE 5-mm reformation (C).