Tierärztliche Hochschule Hannover

Manuskript I
4.1 Abstract
Magnetic resonance spectroscopy (MRS) is a noninvasive method to reveal
pathological changes that might not be visible in routine magnet resonance imaging.
In the current study a 3 Tesla Philips Achieva MRI scanner (Philips Medical Systems
Nederland, PC Best, the Netherlands) was used to prove the hypothesis that
measurement of metabolites in the canine spinal cord in vivo is feasible. Fortyseven
dogs were examined under general anesthesia to measure the concentrations of N-
acetyl-aspartat (NAA), choline (Cho), myo-inositol (mI), creatine (Cr), lactate (Lac)
and glutamate, and glutamine (Glx) using a PRESS-pulse sequence. Spectroscopic
examination was performed with the voxel placed in the brain in 23 dogs and in the
spinal cord in 24 animals, respectively. For comparison, defined concentrations of the
metabolites were evaluated in a round bottom flask phantom. In the central nervous
system and the phantom two different voxel sizes were used and compared.
Peaks of NAA, Cho, Cr, Lac, mI as well as Glx were measurable in well resolved
spectra in both voxel sizes. Small voxel showed an increased amount of unreliable
measurements due to decreased signal to noise ratios (SNR) resulting in low spectral
resolution. Enlargement of the voxel size in the spinal cord lead to loss of
visualization of small focal lesions but permit a verified assignment of metabolites.
Metabolite concentrations were higher in the canine spinal cord than in the brain. In
conclusion, MRS measurements are feasible in the canine spinal cord but subject to
many restrictions.
4.2 Introduction
Magnetic resonance spectroscopy (MRS) enables the noninvasive acquisition and
quantitative measurement of special metabolites, which, with correct positioning of
the voxel, may indicate changes in the central nervous system (CNS) in vivo. Thus it
is more sensitive in determining the underlying pathology of diseases than
conventional magnetic resonance imaging (MRI). 1-3 The localized single voxel ¹H
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