Highly‐accelerated volumetric brain examination using optimized wave‐CAIPI encoding

Background

Rapid volumetric imaging protocols could better utilize limited scanner resources.

Purpose

To develop and validate an optimized 6‐minute high‐resolution volumetric brain MRI examination using Wave‐CAIPI encoding.

Study Type

Prospective.

Population/Subjects

Ten healthy subjects and 20 patients with a variety of intracranial pathologies.

Field Strength/Sequence

At 3 T, MPRAGE, T₂‐weighted SPACE, SPACE FLAIR, and SWI were acquired at 9‐fold acceleration using Wave‐CAIPI and for comparison at 2–4‐fold acceleration using conventional GRAPPA.

Assessment

Extensive simulations were performed to optimize the Wave‐CAIPI protocol and minimize both g‐factor noise amplification and potential T₁/T₂ blurring artifacts. Moreover, refinements in the autocalibrated reconstruction of Wave‐CAIPI were developed to ensure high‐quality reconstructions in the presence of gradient imperfections. In a randomized and blinded fashion, three neuroradiologists assessed the diagnostic quality of the optimized 6‐minute Wave‐CAIPI exam and compared it to the roughly 3× slower GRAPPA accelerated protocol using both an individual and head‐to‐head analysis.

Statistical Test

A noninferiority test was used to test whether the diagnostic quality of Wave‐CAIPI was noninferior to the GRAPPA acquisition, with a 15% noninferiority margin.

Results

Among all sequences, Wave‐CAIPI achieved negligible g‐factor noise amplification (g_avg ≤ 1.04) and burring artifacts from T₁/T₂ relaxation. Improvements of our autocalibration approach for gradient imperfections enabled increased robustness to gradient mixing imperfections in tilted‐field of view (FOV) prescriptions as well as variations in gradient and analog‐to‐digital converter (ADC) sampling rates. In the clinical evaluation, Wave‐CAIPI achieved similar mean scores when compared with GRAPPA (MPRAGE: Ø_W = 4.03, Ø_G = 3.97; T₂w SPACE: Ø_W = 4.00, Ø_G = 4.00; SPACE FLAIR: Ø_W = 3.97, Ø_G = 3.97; SWI: Ø_W = 3.93, Ø_G = 3.83) and was statistically noninferior (N = 30, P < 0.05 for all sequences).

Data Conclusion

The proposed volumetric brain exam retained comparable image quality when compared with the much longer conventional protocol.

Level of Evidence: 2

Technical Efficacy: Stage 1

J. MAGN. RESON. IMAGING 2019.

from #Head and Neck by Sfakianakis via simeraentaxei on Inoreader http://bit.ly/2MVcrLD