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Der Radiologe

, Volume 43, Issue 7, pp 566–575 | Cite as

Diffusion tensor imaging zur Erfassung axonaler Degeneration bei Morbus Alzheimer

  • R. Stahl
  • O. Dietrich
  • S. Teipel
  • H. Hampel
  • M. F. Reiser
  • S. O. Schoenberg
Demenzerkrankungen

Zusammenfassung

Fragestellung

Bei der Alzheimer-Erkrankung (AD) kommt es zur kortikalen Degeneration und sekundär zu degenerativen Veränderungen der weißen Substanz. Es soll untersucht werden, inwieweit die hierdurch resultierende erhöhte Beweglichkeit von Wassermolekülen in verschiedenen Regionen mittels diffusion tensor imaging (DTI) erfasst und eingestuft werden kann. Dabei soll überprüft werden, ob die parallele Bildgebung (iPAT-Technik) zu verzerrungsfreieren Bildern führt.

Methodik

Wir untersuchten 9 AD-Patienten mit milder Form der AD-Demenz und 10 gesunde Kontrollprobanden. DTI-Messungen wurden an einem 1,5-Tesla-System (Siemens Magnetom Sonata) mit iPAT-Technik und einer EPI-Diffusionssequenz mit TE/TR 71 ms/6000 ms durchgeführt. Wir verwendeten eine 8-Kanal-Phased-array-Kopfspule und einen GRAPPA-Rekonstruktionsalgorithmus mit einem iPAT-Beschleunigungsfaktor von 2. Aus dem Tensor wurden der effektive Diffusionskoeffizient (ADC), die fraktionelle (FA) und die relative (RA) Anisotropie in verschiedenen Arealen der weißen Substanz berechnet.

Ergebnisse

Die AD-Patienten wiesen im Genu des Corpus callosum signifikant kleinere (p <0,05) FA- sowie tendenziell größere (p=0,06) ADC-Werte als die Kontrollen auf. Innerhalb des Spleniums, perikallosal, in der Capsula interna, im Frontal-, Okzipital-, Temporal- und Parietallappen zeigten sich keine signifikanten Unterschiede. Durch die iPAT-Technik ergaben sich deutlich weniger suszeptibilitätsinduzierte Verzerrungen.

Schlussfolgerungen

Mit DTI können bereits in Stadien der milden AD Veränderungen der weißen Substanz erfasst werden. Die veränderten FA- und ADC-Werte bei AD-Patienten sind mutmaßlich Ausdruck mikroskopisch kleiner axonaler Degenerationen in der weißen Substanz. Durch die verbesserte Bildqualität mit iPAT-Technik kann der Tensor präziser berechnet werden.

Schlüsselwörter

Magnetresonanztomographie Diffusion tensor imaging Morbus Alzheimer Parallele Bildgebung Axonale Degeneration 

Abstract

Purpose

Alzheimer disease (AD) causes cortical degeneration with subsequent degenerative changes of the white matter. The aim of this study was to investigate the extent of white matter tissue damage of patients with Alzheimer's disease in comparison with healthy subjects using diffusion tensor MRI (DTI). The value of integrated parallel imaging techniques (iPAT) for reduction of image distortion was assessed.

Material and methods

We studied 9 patients with mild AD and 10 age and gender matched healthy controls. DTI brain scans were obtained on a 1.5 tesla system (Siemens Magnetom Sonata) using parallel imaging (iPAT) and an EPI diffusion sequence with TE/TR 71 ms/6000 ms. We used an 8-element head coil and a GRAPPA reconstruction algorithm with an acceleration factor of 2. From the tensor, the mean diffusivity (D), the fractional anisotropy (FA), and the relative anisotropy (RA) of several white matter regions were determined.

Results

FA was significantly lower (p <0,05) in the white matter of the genu of corpus callosum from patients with AD than in the corresponding regions from healthy controls. There was a trend observed for slightly higher ADC values in the AD group (p=0,06). No significant changes were observed in the regions of the splenium, internal capsule, pericallosal areas, frontal, temporal, parietal, and occipital lobe. The images obtained with iPAT contained substantially less susceptibility artefacts and were less distorted than images acquired with non-parallel imaging technique.

Conclusions

DTI is a method with potential to assess early stages of white matter damage in vivo. The altered FA and ADC values in the genu of corpus callosum of patients with AD presumably reflect the microscopic white matter degeneration. Acquisition time can be reduced by iPAT methods with less image distortion from susceptibility artefacts resulting in a more accurate calculation of the diffusion tensor.

Keywords

Magnetic resonance imaging Diffusion tensor imaging Alzheimer's disease Parallel imaging technique White matter damage 

Notes

Danksagung

Die Autoren danken Herrn Dr. Berthold Kiefer und Herrn Dr. Rolf Sauter, Siemens Medical Solutions, Erlangen, sowie Herrn Felician Jancu, Psychiatrische Klinik der Ludwig-Maximilians-Universität München, für die technische Unterstützung.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • R. Stahl
    • 1
    • 3
  • O. Dietrich
    • 1
  • S. Teipel
    • 2
  • H. Hampel
    • 2
  • M. F. Reiser
    • 1
  • S. O. Schoenberg
    • 1
  1. 1.Institut für Klinische Radiologie - GroßhadernKlinikum der Universität München
  2. 2.Klinik für Psychiatrie und PsychotherapieKlinikum der Universität München
  3. 3.Institut für Klinische Radiologie - GroßhadernKlinikum der Universität MünchenMünchen

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