Optimal Configuration for Relaxation Times Estimation in Complex Spin Echo Imaging

Fabio Baselice,Vito Pascazio,Alessandro Grassia,Giampaolo Ferraioli

doi:10.3390/s140202182

Fabio Baselice, Vito Pascazio + Show 2 more

Open Access

https://doi.org/10.3390/s140202182

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Journal: Sensors	Publication Date: Jan 28, 2014
Citations: 40	License type: CC BY 4.0

Affiliation: Parthenope University of Naples

Abstract

Many pathologies can be identified by evaluating differences raised in the physical parameters of involved tissues. In a Magnetic Resonance Imaging (MRI) framework, spin-lattice T1 and spin-spin T2 relaxation time parameters play a major role in such an identification. In this manuscript, a theoretical study related to the evaluation of the achievable performances in the estimation of relaxation times in MRI is proposed. After a discussion about the considered acquisition model, an analysis on the ideal imaging acquisition parameters in the case of spin echo sequences, i.e., echo and repetition times, is conducted. In particular, the aim of the manuscript consists in providing an empirical rule for optimal imaging parameter identification with respect to the tissues under investigation. Theoretical results are validated on different datasets in order to show the effectiveness of the presented study and of the proposed methodology.

Highlights

Relaxation times define the rate of spin magnetic equilibrium recovery in nuclear magnetic resonance (NMR) [1,2]
Several Cramer–Rao lower bounds (CRLBs)-based evaluations have been presented in order to investigate the possibility of finding the optimal, in terms of reconstruction accuracy, imaging parameter configuration for the estimation of T1 and T2 maps
The optimal acquisition parameters for several tissues have been computed for both 1.5 T and 3 T acquisitions

Summary

Introduction

Relaxation times define the rate of spin magnetic equilibrium recovery in nuclear magnetic resonance (NMR) [1,2]. Following the approach proposed by [15], within this paper we investigate the possibility of finding the optimal imaging parameter configuration for relaxation time estimation. Since CRLBs provide the best achievable performances in the unbiased estimation of one or more parameters, by minimizing them with respect to the MR scanner imaging parameters, it is possible to find the optimal acquisition configuration for the relaxation time estimation. The result of the study is the introduction of a general empirical rule for determining the optimal (with respect to CRLBs) MRI scanner parameter configuration. The manuscript is organized as follows: in Section 2, the acquisition model for an MRI spin echo sequence is presented, and, the achievable performances of the estimation are analyzed via the CRLBs. In Section 4, the CRLB-based empirical rule for the optimal acquisition parameter configuration is presented.

The Model

Cramer–Rao Lower Bounds Evaluations

Optimal Parameter Configuration

Numerical Experiments

Conclusions