[Magnetic resonance spectroscopy of brain tumors].
BACKGROUND
Conventional magnetic resonance imaging (MRI) under consideration of clinical information enables the correct diagnosis and therapy for the majority of cerebral space-occupying lesions. Some important differential diagnoses, e. g. low vs. high-grade tumors, require additional MRI methods.


OBJECTIVE
This article critically discusses the importance of magnetic resonance spectroscopy (1H-MRS) in brain tumors.


METHODS
The concentration of normal and pathological brain metabolites can be non-invasively measured by1H-MRS. It is based on the principle that chemical proton compounds of certain brain metabolites focally attenuate the external magnetic field and change the proton resonance frequency according to typical patterns. In addition, parameter maps of MRS imaging (MRSI) can show the tumor heterogeneity as well as changes in the surrounding brain tissue. In this context, the patterns of N‑acetylaspartate, total choline (tCho) and creatine are relatively robust, whereas the patterns of other metabolites, such as myoinositol, glutamate, lactate or lipids greatly depend on the external field strength and echo time.


RESULTS
The signal intensity of tCho in vital tumor tissue increases with the WHO grade of the brain tumor, i.e. increases with the level of malignancy. The use of MRSI facilitates the WHO grading of gliomas by determining target points in biopsies. Different distribution patterns and specific metabolite signals enable a better differentiation between abscesses, metastases, central nervous system (CNS) lymphomas and gliomas.


CONCLUSIONS
The use of1H-MRS provides valuable information on the differential diagnosis and graduation of brain tumors; however, so far artefacts, signal strength, parameter selection and a lack of standardization impede the establishment of1H-MRS for use in clinical routine diagnostics.
FE Neuroradiologie, Radiologische Klinik, Universitätsklinikum Bonn, Sigmund-Freud-Str. 25, 53127, Bonn, Deutschland.
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Ditter
FE Neuroradiologie, Radiologische Klinik, Universitätsklinikum Bonn, Sigmund-Freud-Str. 25, 53127, Bonn, Deutschland. elke.hattingen@ukb.uni-bonn.de.
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Hattingen
D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism; D001932:Brain Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005910:Glioma / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy
D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline
Brain metabolites; Choline; Differential diagnosis; Grading; Lipids