Learning objectives
The aim of this poster is to:
present examples of typical magnetic resonance spectroscopy (MRS) patterns of low and high-grade gliomas,
metastatic lesions and tumor mimickers on sequences with short and long echo
illustrate the imaging features that can help distinguish between brain tumors and mimickers
emphasize the patterns causing controversies in MRS interpretation.
Background
Magnetic resonance spectroscopy (MRS) is a diagnostic tool that provides information on brain metabolism [1].
The two main techniques used are:
single voxel spectroscopy with short and long echo,
which samples a single region of interest.
Two commonly used techniques are stimulated echo acquisition mode (STEAM) [2] and proton resolved spectroscopy (PRESS) [3].
multivoxel MRS or chemical shift imaging (CSI) [4],
which obtains samples from multiple adjacent regions,
and measures larger volumes of brain tissue.
The main metabolites which are detected are:
choline (Cho),
a...
Findings and procedure details
When performing MRS,
the most prominent peak is that of water.
In order to evaluate the aforementioned metabolites,
water suppression must be performed,
usually by using "Chemical Shift Selective Imaging",
or CHESS [5].
Magnetic resonance spectroscopy is usually evaluated by determining absolute metabolic ratios [6].
Normal metabolite ratios are (Fig.
1):
Cho/Cr up to 1.2,
while values above 1.5 are considered abnormal,
NAA/Cr up to 2.0,
while values below 1.6 are considered abnormal,
NAA/Cho up to 1.6.
Increased cell membrane synthesis and accelerated cell proliferation...
Conclusion
Typical neurometabolic features may help differentiate between non-neoplastic and neoplastic lesions,
which is often difficult on conventional MRI.
Its use with other sequences and novel imaging modalities provides valuable insight into lesion architectonics and evaluation of treatment response.
Personal information
I.
Nosek,
MD
Oncology Institute of Vojvodina,
Center for Diagnostic Imaging,
Sremska Kamenica,
Serbia.
Put doktora Goldmana 4
21204 Sremska Kamenica,Serbia
Phone: +381214805604
e-mail:
[email protected]
References
Kozić D et al.
(2012) The role of MR spectroscopy in neurooncology.Prilozi 33(1):425–433.
Bottomley PA (1987) Spatial localization in NMR spectroscopy in vivo.Ann N Y Acad Sci.508:333–348.
Frahm J (1987) Localized Proton Spectroscopy using stimulated echoes.J Magn Reson.72(3):502–508.
Brown TR et al.
(1982) NMR chemical shift imaging in three dimensions.Proc Natl Acad Sci U S A.79(11):3523–3526.
Haase A (1986) Localization of unaffected spins in NMR imaging and spectroscopy (LOCUS spectroscopy).
Magn Reson Med 3(6):963–9.
Ostojic J et al.
(2009) Brain white matter 1H MRS in...