Proton MR spectroscopy improves discrimination between tumor and pseudotumoral lesion in solid brain masses.
OBJECTIVE
Differentiating between tumors and pseudotumoral lesions by conventional MR imaging may be a challenging question. This study aims to evaluate the potential usefulness and the added value that single-voxel proton MR spectroscopy could provide on this discrimination.


METHODS
A total of 84 solid brain lesions were retrospectively included in the study (68 glial tumors and 16 pseudotumoral lesions). Single-voxel spectra at TE 30 ms (short TE) and 136 ms (long TE) were available in all cases. Two groups were defined: "training-set" (56 cases) and "test-set" (28 cases). Tumors and pseudotumors were compared in the training-set with the Mann-Whitney U test. Ratios between resonances were defined as classifiers for new cases, and thresholds were selected with receiver operating characteristic (ROC) curves. The added value of spectroscopy was evaluated by 5 neuroradiologists and assessed with the Wilcoxon signed-rank test.


RESULTS
Differences between tumors and pseudotumors were found in myo-inositol (mIns); P < .01) at short TE, and N-acetylaspartate (NAA; P < .001), glutamine (Glx; P < .01), and choline (CHO; P < .05) at long TE. Classifiers suggested tumor when mIns/NAA ratio was more than 0.9 at short TE and also when CHO/NAA ratio was more than 1.9 at long TE. Classifier accuracy was tested in the test-set with the following results: short TE, 82% (23/28); long TE, 79% (22/28). The neuroradiologists' confidence rating of the test-cases on a 5-point scale (0-4) improved between 5% (from 2.86-3) and 27% (from 2.25-2.86) with spectroscopy (mean, 17%; P < .01).


CONCLUSIONS
The proposed ratios of mIns/NAA at short TE and CHO/NAA at long TE provide valuable information to discriminate between brain tumor and pseudotumor by improving neuroradiologists' accuracy and confidence.
Majós
C
C
Institut de Diagnòstic per la Imatge, Centre Bellvitge, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Spain. cmajos@csub.scs.es
Aguilera
C
C
Alonso
J
J
Julià-Sapé
M
M
Castañer
S
S
Sánchez
J J
JJ
Samitier
A
A
León
A
A
Rovira
A
A
Arús
C
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001927:Brain Diseases / Q000175:diagnosis* / Q000378:metabolism*; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000592:standards; D008297:Male; D008875:Middle Aged; D011522:Protons; D015203:Reproducibility of Results; D012189:Retrospective Studies; D055815:Young Adult
D011522:Protons; D005973:Glutamine; D001224:Aspartic Acid; C000179:N-acetylaspartate; D002794:Choline