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 Carr-Purcell-Gill-Meiboom pulse trains 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 1/T_2,i and α_i. The T_2,i values are represented in a T₂ histogram of the slice and then selected for generating images which relate to protons with specific T₂. The α_i values indicate the relative amounts of the T₂-selected protons. Imaging on the basis of α₂ 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 fast-relaxing proton classes.