Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA)

TLDR

CAIPIRINHA is a parallel imaging technique that alters aliasing artifacts during acquisition to enhance reconstruction. The study aims to extend CAIPIRINHA to 3D imaging, enabling simultaneous data reduction in two spatial dimensions. The method achieves 2D aliasing control by modifying the phase‑encoding sampling strategy, shifting sampling positions from their normal locations, rather than using special RF pulses. The modified sampling strategy improves exploitation of coil sensitivity variations across dimensions, yielding more robust parallel imaging reconstruction, and has already been applied successfully to simultaneous multi‑slice imaging. © 2006 Wiley‑Liss, Inc.; published in Magn Reson Med.

Abstract

Abstract The CAIPIRINHA (Controlled Aliasing In Parallel Imaging Results IN Higher Acceleration) concept in parallel imaging has recently been introduced, which modifies the appearance of aliasing artifacts during data acquisition in order to improve the subsequent parallel imaging reconstruction procedure. This concept has been successfully applied to simultaneous multi‐slice imaging (MS CAIPIRINHA). In this work, we demonstrate that the concept of CAIPIRINHA can also be transferred to 3D imaging, where data reduction can be performed in two spatial dimensions simultaneously. In MS CAIPIRINHA, aliasing is controlled by providing individual slices with different phase cycles by means of alternating multi‐band radio frequency (RF) pulses. In contrast to MS CAIPIRINHA, 2D CAIPIRINHA does not require special RF pulses. Instead, aliasing in 2D parallel imaging can be controlled by modifying the phase encoding sampling strategy. This is done by shifting sampling positions from their normal positions in the undersampled 2D phase encoding scheme. Using this modified sampling strategy, coil sensitivity variations can be exploited more efficiently in multiple dimensions, resulting in a more robust parallel imaging reconstruction. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.