Generalized MRI reconstruction including elastic physiological motion and coil sensitivity encoding

Abstract

This article describes a general framework for multiple coil MRI reconstruction in the presence of elastic physiological motion. On the assumption that motion is known or can be predicted, it is shown that the reconstruction problem is equivalent to solving an integral equation-known in the literature as a Fredholm equation of the first kind-with a generalized kernel comprising Fourier and coil sensitivity encoding, modified by physiological motion information. Numerical solutions are found using an iterative linear system solver. The different steps in the numerical resolution are discussed, in particular it is shown how over-determination can be used to improve the conditioning of the generalized encoding operator. Practical implementation requires prior knowledge of displacement fields, so a model of patient motion is described which allows elastic displacements to be predicted from various input signals (e.g., respiratory belts, ECG, navigator echoes), after a free-breathing calibration scan. Practical implementation was demonstrated with a moving phantom setup and in two free-breathing healthy subjects, with images from the thoracic-abdominal region. Results show that the method effectively suppresses the motion blurring/ghosting artifacts, and that scan repetitions can be used as a source of over-determination to improve the reconstruction.

Evaluation of delineation of image details in semiconductor PET utilizing the normalized mutual information technique

“…NMI is a well-known concept that is often used to image coregistration for both intramodality and intermodality images [8][9][10]. Recently, Jiang and colleagues [11,12] introduced the use of NMI as a reference image with which to evaluate image quality. We assumed that the NMI-based technique would work successfully for three-dimensional (3D) volume images.…”

“…In addition, it was already demonstrated that NMI values calculated between the reference image and acquired images can be used to evaluate image quality [11,12,20].…”

Generalized Reconstruction by Inversion of Coupled Systems (GRICS) applied to free‐breathing MRI

“…This work can be extended to multiple coil acquisition (8), by combination with the general parallel imaging method proposed in (9). The resulting framework involves modeling the acquisition pipeline as shown in Fig.…”

“…This article starts by presenting a reconstruction framework also descibed in (8), generalizing methods in (7) and (9), in order to correct for artifacts caused by elastic motion (nonrigid or affine) in the context of multiple coil acquisition. Practical implementation requires knowledge of complete displacement fields at each acquisition time.…”

Motion compensated generalized reconstruction for free‐breathing dynamic contrast‐enhanced MRI

“…Then in (19), elastic spatial transformation operator T ti was incorporated in the equation of generalized SENSE:…”