Combined volumetric T1, T2 and secular-T2 quantitative MRI of the brain: age-related global changes (preliminary results)

doi:10.1016/j.mri.2006.04.011

Magnetic Resonance Imaging

Volume 24, Issue 7, September 2006, Pages 877-887

https://doi.org/10.1016/j.mri.2006.04.011 Get rights and content

Abstract

The combined T₁, T₂ and secular-T₂ pixel frequency distributions of 24 adult human brains were studied in vivo using a technique based on the mixed-TSE pulse sequence, dual-space clustering segmentation and histogram gaussian decomposition. Pixel frequency histograms of whole brains and the four principal brain compartments were studied comparatively and as function of age. For white matter, the position of the T₁ peak correlates with age (R²=.7868) when data are fitted to a quadratic polynomial. For gray matter, a weaker age correlation is found (R²=.3687). T₂ and secular-T₂ results are indicative of a weaker correlation with age. The technique and preliminary results presented herein may be useful for characterizing normal as well as abnormal aging of the brain, and also for comparison with the results obtained with alternative quantitative MRI methodologies.

Introduction

As recently reviewed [1], [2], many groups have investigated ¹H-proton T₁ and T₂ quantitative MRI (Q-MRI) relaxometry as tools for measuring changes caused by diseases affecting the brain, including multiple sclerosis, cerebral neoplasia, epilepsy, stroke, dementia, schizophrenia, depression, human immunodeficiency virus infection, cerebral ischemia and other conditions. Age-related changes of the mean T₁ or mean T₂ of selected brain regions have also been investigated [3], [4], [5], [6]. With some exceptions [7], [8], [9], prior research has studied changes in T₁ or T₂, but not both relaxation times at the same time.

Very few Q-MRI pulse sequences [10], [11], [12], [13], [14], [15] that allow for simultaneous and, consequently, self-co-registered T₁ and T₂ mapping with one scan have been described. Generating self-co-registered T₁ and T₂ maps could be useful for medical purposes because these two tissue parameters represent different tissue information that is largely independent of each other. Nevertheless, T₁ information and T₂ information are not fully independent of each other because all spin–lattice interactions that cause T₁ recovery also contribute to T₂ decay. The difference between the T₁ and T₂ relaxation rates represents the pure spin–spin interactions [16] and is known as the secular relaxation rate. The associated secular-T₂ relaxation time is given by $T_{2}^{(sec)} = T_{2} / (1 - T_{2} / 2 T_{1})$

Secular-T₂ represents the pure spin–spin component of T₂ whereby the contribution of the spin–lattice component or nonsecular component has been removed.

Here we study the combined T₁, T₂ and secular-T₂ frequency distributions (spectra) of 24 adult human brains in vivo using a Q-MRI technique based on the mixed-TSE pulse sequence that allows for combined, self-co-registered and volumetric mapping of T₁, T₂ and, consequently, secular-T₂. Pixel frequency histograms of whole brains and the four principal brain compartments (left and right cerebral and cerebellar segments) are studied comparatively. Global T₁, T₂ and secular-T₂ age dependencies of whole-head intracranial tissues are investigated and results discussed in the context of existing literature.

Section snippets

Subjects

Over a 4-month period (May 2005 through August 2005), 24 subjects were enrolled for this study: 2 volunteers and 22 patients who were referred to MRI for various clinical reasons, including headache, TMJ pain, visual field defect, cerebral vascular accident, seizure, motor tics, localized paresthesia, seventh and twelfth nerve palsy, endocrinopathy and breast cancer. The average age was 47 years, and the gender composition was 14 females and 10 males. The patients were consented following NIH

Quantitative maps

Representative T₁, T₂ and secular-T₂ maps of two subjects (a 23-year-old female (top row) and a 77-year-old male) are shown in Fig. 2. Mapping image quality was comparable for all subjects at all locations (80 slices each). Noticeable are the enlarged intra- and extraventricular CSF spaces of the 77-year-old subject relative to the 23-year-old subject, as well as the relative loss of WM-to-GM contrast in the T₁ map of the 77-year-old relative to the 23-year-old subject. Such WM-to-GM contrast

Discussion and conclusion

The brains of 24 adult human subjects have been analyzed with combined T₁, T₂ and secular-T₂ Q-MRI using a previously described technique [20] that provides self-co-registered and volumetric Q-MRI data sets. The research subjects were not recruited according to any specific medical criterion other than their willingness to participate in this study. This is part of a broad-scope research program of our laboratory, which has the dual objectives of Q-MRI technique development and identification

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Original contributionCombined volumetric T1, T2 and secular-T2 quantitative MRI of the brain: age-related global changes (preliminary results)

Abstract

Introduction

Section snippets

Subjects

Quantitative maps

Discussion and conclusion

Magn Reson Imaging

Magn Reson Imaging

Magn Reson Imaging

J Neurol Sci

Magn Reson Imaging

Magn Reson Imaging

Magn Reson Imaging

Chapter 5, T1: the longitudinal relaxation time

Chapter 6, T2: the transverse relaxation time

Normal brain maturation characterized with age-related T2 relaxation times: an attempt to develop a quantitative imaging measure for clinical use

Invest Radiol

T1 and T2 in the brain of healthy subjects, patients with Parkinson disease, and patients with multiple system atrophy: relation to iron content

Radiology

Original contribution
Combined volumetric T₁, T₂ and secular-T₂ quantitative MRI of the brain: age-related global changes (preliminary results)