Three-Dimensional Variable Slab-Selective Projection Acquisition Imaging

TL;DR

This paper introduces a variable slab-selective projection acquisition (VSS-PA) method for 3D imaging that reduces artifacts and improves image quality by selectively exciting spins within the desired field of view, especially beneficial for larger subjects.

Contribution

The paper presents a novel VSS-PA technique that suppresses aliasing artifacts and mitigates the Nyquist criterion in 3D projection acquisition imaging.

Findings

VSS-PA effectively suppresses aliasing streak artifacts.

The method reduces the effective size of the scanned object, improving image quality.

Experimental results confirm the theoretical advantages of VSS-PA.

Abstract

Three-dimensional (3D) projection acquisition (PA) imaging has recently gained attention because of its advantages, such as achievability of very short echo time, less sensitivity to motion, and undersampled acquisition of projections without sacrificing spatial resolution. However, larger subjects require a stronger Nyquist criterion and are more likely to be affected by outer-volume signals outside the field of view (FOV), which significantly degrades the image quality. Here, we proposed a variable slab-selective projection acquisition (VSS-PA) method to mitigate the Nyquist criterion and effectively suppress aliasing streak artifacts in 3D PA imaging. The proposed method involves maintaining the vertical orientation of the slab-selective gradient for frequency-selective spin excitation and the readout gradient for data acquisition. As VSS-PA can selectively excite spins only in the width of the desired FOV in the projection direction during data acquisition, the effective size of the scanned object that determines the Nyquist criterion can be reduced. Additionally, unwanted signals originating from outside the FOV (e.g., aliasing streak artifacts) can be effectively avoided. The mitigation of the Nyquist criterion owing to VSS-PA was theoretically described and confirmed through numerical simulations and phantom and human lung experiments. These experiments further showed that the aliasing streak artifacts were nearly suppressed.