MR imaging with 3D fast spin echo using projection reconstruction: technique description and applications

Conventional Fourier transform MR imaging techniques are highly sensitive to motion artifacts, particularly for applications such as imaging the neck (breathing, swallowing, cardiovascular pulsatility), the abdomen and diffusion-weighted imaging. In this study, the authors describe a novel 3D imaging technique which combines a 3D fast spin echo with a projection reconstruction acquisition. Projection reconstruction techniques demonstrate less objectionable motion artifacts compared with conventional Fourier transform MRI techniques. In this implementation, the FSE readout gradients are modified to collect projection data in the x-y plane. The projection angle is fixed and the slice-encoding gradient in z is modulated during the echo train. The projection angle is incremented for each new echo train series. Since the acquisition is 3D, it will have improved signal-to-noise over comparable 2D acquisitions. The primary disadvantage to the technique is the increased blurring in the slice-encode direction that results from the T2-weighting of the slice-encoded echoes. The technique was demonstrated on both a phantom and the neck of a human volunteer. The acquisition technique may be useful for the applications of high-resolution carotid black-blood imaging as well as diffusion-weighted imaging of the human brain.