Analysis of Multiple T2 Proton Relaxation Processes in Human Head and Imaging on the Basis of Selective and Assigned T2 Values

Abstract

Two-dimensional T2-selective proton imaging of human head has been performed at 10 MHz employing Cam-Purcell-Gill-Meiboom pulse lrains with echo separation of 6 and 12 msec. Using the information of 36 spin echoes and applying a recovery time of 2 sec the magnetization decay has been traced. The multi-exponential T2 relaxation curve of each pixel of the image has been deconvoluted into up to three monoexponential functions which are defined by l/T2., and a, The T2., values are represented in a T2 histogram of the slice and then selected for generating images which relate to protons with specific T2. The a, values indicate the relative amounts of the Tz-selected protons. Imaging on the basis of a, values increases the contrast of the image. The multiple T2-selective imaging technique leads to head images which show selectively cerebrospinal fluid, gray matter, different types of white: matter, and nonassigned fastrelaxing proton classes.

In vivo 1H2O T measurement in the human occipital lobe at 4T and 7T by Carr‐Purcell MRI: Detection of microscopic susceptibility contrast

“…Similarly at 7T, images with τ cp = 6 ms and τ cp ≥ 10 ms were used as separate datasets. Although the decay of water is known to be multiexponential (30, 31), the characterization of T time constants was assumed to be monoexponential because decay measurements were made over a narrow range of TE values (37–155 ms). To minimize partial volume contamination, gray matter, white matter, and CSF regions were selected applying the following criteria to the T 1 ‐weighted anatomical images and the T relative susceptibility images.…”

Texture Analysis in Quantitative MR Imaging

“…Tissue characterisation by MR imaging, solely based on determination of Tl and T2 relaxation times, has proved rather disappointing with respect to specificity and clinical applicability (l, 8,15,16,18,27). Evidence indicates that tissue heterogeneity is a principal cause of the variation in the reported relaxation times, while imperfections in hardware and shortcomings in the experimental strategy seem to be of minor importance in this connection (1, 15,16,18,27).…”

A modified signal intensity equation of carr-purcell-meiboom-gill pulse sequence for MR imaging.

“…Carr-PurcellMeiboom-Gill (CPMG) pulse sequence, which is a multiple Spin-Echo (MSE) pulse sequence, has produced the accurate T2 value in clinical magnetic resonance imaging (MRI) (Gersonde et al 1984; Rinck et al 1985). The CPMG signal intensity equation for T2 calculation has been reported (Schneiders et al 1983; Bucciolini et al 1986), but nobody found that T1 could be measured in CPMG pulse sequence.…”