Characterization of intracranial mass lesions with in vivo proton MR spectroscopy.
OBJECTIVE
To assess the use of in vivo proton MR spectroscopy for characterization of intracranial mass lesions and to ascertain its reliability in grading of gliomas.


METHODS
One hundred twenty patients with intracranial masses were subjected to volume selective spectroscopy using stimulated echo acquisition mode (echo time, 20 and 270 milliseconds) and spin echo (echo time, 135 milliseconds) sequences. The intracranial lesions were grouped into intraaxial and extraaxial, as judged with MR imaging. Assignment of resonances was confirmed in two samples each of brain abscess, epidermoid cyst, and tuberculoma using ex vivo high-resolution MR spectroscopy.


RESULTS
The in vivo spectra appeared distinct compared with normal brain in all the cases. All high-grade gliomas (n = 37) showed high choline and low or absent N-acetyl-L-aspartate and creatine along with lipid and/or lactate, whereas low-grade gliomas (n = 23) were characterized by low N-acetyl-aspartate and creatine and high choline and presence of only lactate. N-acetyl-aspartate/choline ratio was significantly lower and choline/creatine ratio was significantly higher in high-grade gliomas than in low-grade gliomas. Presence of lipids suggested a higher grade of malignancy. All metastases (n = 7) showed lipid and lactate, whereas choline was visible in only four cases. Epidermoids showed resonances from lactate and an unassigned resonance at 1.8 ppm. Meningiomas could be differentiated from schwannomas by the presence of alanine in the former. Among the infective masses, pyogenic abscesses (n = 6) showed resonances only from cytosolic amino acids, lactate, alanine, and acetate; and tuberculomas (n = 11) showed only lipid resonances.


CONCLUSIONS
In vivo proton MR spectroscopy, helps in tissue characterization of intracranial mass lesions. Spectroscopy is a reliable technique for grading of gliomas when N-acetyl-aspartate/choline and choline/creatine ratios and presence of lipids are used in combination.
Poptani
H
H
Department of Radiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India.
Gupta
R K
RK
Roy
R
R
Pandey
R
R
Jain
V K
VK
Chhabra
D K
DK
D000293:Adolescent; D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D001927:Brain Diseases / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D002648:Child; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D003937:Diagnosis, Differential; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005910:Glioma / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D050356:Lipid Metabolism; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D008579:Meningioma / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D009367:Neoplasm Staging; D009442:Neurilemmoma / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D011522:Protons; D012815:Signal Processing, Computer-Assisted
D007773:Lactates; D011522:Protons; D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline