Analysis of multiple T2 proton relaxation processes in human head and imaging on the basis of selective and assigned T2 values

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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/T2,i and αi. The T2,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 αi 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.