Comparison of human brain metabolite levels using 1H MRS at 1.5T and 3.0T.

Fernando Fernandes Paiva,Andrea Silveira De Souza,Jorge Moll,Ricardo De Oliveira-Souza,Ivanei Edson Bramati,Fernanda Tovar-Moll,Maria Concepcion Garcia Otaduy,Luciane Oliveira

doi:10.1590/s1980-57642013dn70200013

Abstract

Proton magnetic resonance spectroscopy (MRS) of the human brain has proven to be a useful technique in several neurological and psychiatric disorders and benefits from higher field scanners as signal intensity and spectral resolution are proportional to the magnetic field strength.OBJECTIVETo investigate the effects of the magnetic field on the measurement of brain metabolites in a typical routine clinical setting.METHODSSingle voxel spectra were acquired from the posterior cingulate cortex in 26 healthy subjects. Each subject was scanned consecutively at 1.5T and 3.0T in a randomly distributed order.RESULTSSNR and peak width improvements were observed at higher fields. However, SNR improvement was lower than the theoretical two-fold improvement. Other than the values obtained for creatine (Cre) and myo-Inositol (mI), which were both higher at 3.0T, all metabolite concentrations obtained were roughly the same at both field strengths. All the metabolite concentrations were estimated with a Cramer Rao lower bounds (CRLB) lower than 15% of the calculated concentrations.CONCLUSIONSEven though the present study supports the expected benefits of higher field strength for MRS, there are several factors that can lead to different quantitative results when comparing 1.5T to 3.0T MRS. Future comparative studies are necessary to refine the metabolite thresholds for early detection and quantification of distinct neurological and psychiatric disorders using 3.0T MRS.

Highlights

Proton magnetic resonance spectroscopy (MRS) has proven to be a useful non-invasive technique to obtain information regarding the normal and abnormal neurochemistry of the human brain.[1,2] In some clinical settings, MRS may show early metabolic changes in apparently anatomically-normal tissue.[3]
An accurate clinical interpretation of individual spectra requires the knowledge of the normal range of relative metabolite levels, as well as an understanding of how the measured values depend on different aspects, such as patient age, region of interest, metabolic conditions, specific MRS technique and field strength
Metabolite levels at 1.5T and 3.0T were assessed in healthy volunteers and the influence of field strength on the measured values, and on calculated metabolite ratios used for diagnostic purposes, were evaluated

Summary

INTRODUCTION

Proton magnetic resonance spectroscopy (MRS) has proven to be a useful non-invasive technique to obtain information regarding the normal and abnormal neurochemistry of the human brain.[1,2] In some clinical settings, MRS may show early metabolic changes in apparently anatomically-normal tissue.[3]. Transverse relaxation times (T2) tend to decrease at higher fields, resulting in lower metabolite signals for a given echo time (TE) when compared to lower field strengths. These higher-field effects may have some clinical implications insofar altered levels of mI are associated with prevalent neurological disorders, such as Alzheimer’s disease. An accurate clinical interpretation of individual spectra requires the knowledge of the normal range of relative metabolite levels (or absolute concentrations), as well as an understanding of how the measured values depend on different aspects, such as patient age, region of interest, metabolic conditions, specific MRS technique and field strength. Metabolite levels at 1.5T and 3.0T were assessed in healthy volunteers and the influence of field strength on the measured values, and on calculated metabolite ratios used for diagnostic purposes, were evaluated

METHODS

RESULTS

DISCUSSION