Necrotic tumor versus brain abscess: importance of amino acids detected at 1H MR spectroscopy--initial results.
OBJECTIVE
To assess the usefulness of the 0.9-ppm peak from amino acids (-CH3 moieties from valine, leucine, and isoleucine) for the differentiation of brain abscesses and tumors at in vivo hydrogen 1 magnetic resonance (MR) spectroscopy.


METHODS
Amino acid concentrations were determined in vitro in 13 purulent samples from brain and nonbrain tissues and in nine aseptic fluids from necrotic brain tumors at two-dimensional (2D) 1H MR spectroscopy and liquid chromatography. Thirty-four patients with cystic intracerebral mass lesions (28 tumors, six abscesses) were examined at 1H MR spectroscopy in vivo.


RESULTS
Amino acids were identified in vitro in both purulent and aseptic samples. Amino acid concentrations measured in the aseptic fluids at both liquid chromatography and 2D MR spectroscopy were far below the detection threshold of in vivo 1H MR spectroscopy. Quantitative results obtained at 2D MR spectroscopy showed no overlap in the ranges of amino acid concentrations in purulent and aseptic samples. In vivo, the proton spectra obtained with a 136-msec echo time (TE) revealed amino acids (inverted peak at 0.9 ppm) in only the abscesses.


CONCLUSIONS
The detection of amino acid resonance at 0.9 ppm at in vivo 1H MR spectroscopy (136-msec TE) is a promising tool for distinguishing bacterial abscesses and cystic brain tumors.
Grand
S
S
Magnetic Resonance Imaging Unit, INSERM U438, Université Joseph Fourier, France.
Passaro
G
G
Ziegler
A
A
Estève
F
F
Boujet
C
C
Hoffmann
D
D
Rubin
C
C
Segebarth
C
C
Décorps
M
M
Le Bas
J F
JF
Rémy
C
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D001424:Bacterial Infections / Q000175:diagnosis*; D001921:Brain / Q000473:pathology; D001922:Brain Abscess / Q000175:diagnosis*; D001932:Brain Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007532:Isoleucine / Q000032:analysis*; D007930:Leucine / Q000032:analysis*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D014633:Valine / Q000032:analysis*
D007532:Isoleucine; D007930:Leucine; D014633:Valine