Preprocessing of Magnetization Decays to Improve Multiexponential T2 Analysis

  • H. Handels
  • T. Tolxdorff
  • K. Bohndorf

Abstract

Multiexponential T2 analysis based on CPMG spin-echo sequences with 32 echoes allows recognition of up to three superimposed transverse relaxation processes in one volume element. In the multiexponential model the measured signal decay is described by
$$\text{M(t)}\,{\kern 1pt} \text{ = }\sum\limits_{\text{i = 1}}^\text{n} {\text{M}_\text{i} (0)\;\text{e}^{ - \frac{\text{t}} {{\text{T2}_\text{i} }}} } \begin{array}{*{20}c} \text{n} \\ \end{array} \underline \leqslant 3$$
(1)
whereby M(t) represents the magnetization at time t, Mj(0) describes the intrinsic magnetization of the i-th relaxation process, and T2i represents its corresponding transverse relaxation time. The signals measured with a multiecho sequence in a commonly used MR imaging system are superimposed by noise, which generates a positive baseline in the two-dimensional Fourier-transformed echo images. While in the multiexponential model the sum of the exponential functions decays to the value zero, the measured signals decay in average to a baseline greater than zero. This leads to errors in the MR parameters determined by T2 analysis. Especially in multiexponential T2 analysis artificial relaxation components may be generated additionally. To reduce the influence of noise on the MR parameter estimations in MR imaging the presented method for preprocessing of magnetization decays has been developed. All magnetization decays and the (256 × 256) echo images shown in this paper were generated with the standard multiecho sequence in a Siemens Magnetom at 1.5 T.

Keywords

Stein 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Bellon E, Haacke EM, Coleman P, Sacco DC, Steiger D, Gangarosa R (1986) MR artifacts: a review. AJR 147:1271–1281PubMedGoogle Scholar
  2. Brosnan T, Graham W, Nishimura D, Cao Q, Macovski A, Sommer FG (1988) Noise reduction in magnetic resonance imaging. Magn Reson Med 8:384–409CrossRefGoogle Scholar
  3. Edelstein W, Glover G, Hardy C, Redington R (1986) The intrinsic signal-to-noise ratio in NMR imaging. Magn Reson Med 3:604–618PubMedCrossRefGoogle Scholar
  4. Graumann R, Oppelt A, Stetter E (1986) Multiple-spin-echo imaging with a 2D Fourier - method. Magn Reson Med 3:707–721PubMedCrossRefGoogle Scholar
  5. Haacke EM, Patrick JL (1986) Reducing motion artifacts in two dimensional Fourier transform imaging. Magn Reson Imaging 4:359–376PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1990

Authors and Affiliations

  • H. Handels
    • 1
  • T. Tolxdorff
  • K. Bohndorf
  1. 1.Institut für Medizinische Statistik und DokumentationKlinikum der Rheinisch-Westfälischen Technischen Hochschule AachenAachenGermany

Personalised recommendations