Published ahead of print on December 18, 2008
doi: 10.3174/ajnr.A1392
Proton MR Spectroscopy Improves Discrimination between Tumor and Pseudotumoral Lesion in Solid Brain Masses
C. Majósa,c,
C. Aguileraa,c,
J. Alonsob,
M. Julià-Sapéc,d,
S. Castañera,
J.J. Sáncheza,
Á. Samitiera,
A. Leónb,
Á. Rovirac and
C. Arúsc,d
a Institut de Diagnòstic per la Imatge (IDI), Centre Bellvitge, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Spain
b Unitat de Ressonància Magnètica (IDI), Servei de Radiologia, Hospital Universitari Vall d'Hebron, Barcelona, Spain
c Centro de Investigaciónen Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Cerdanyola del Vallès, Spain
d Department de Bioquímica i Biologia Molecular, Unitat de Bioquímica de Biociències, Edifici Cs, Universitat Autònoma de Barcelona, Cerdanyola del Vallés, Spain
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Fig 1. Average spectra of tumors and pseudotumors calculated with the cases included in the training-set. Arrows depict the points that showed significant differences between the 2 groups in the statistical analysis. A, Short TE (TE, 30 ms) spectra showed significant differences at 3.55 ppm (MI). Although differences in the mean spectra can also be seen at 2.02 ppm (NAA) and 3.22 ppm (CHO), no statistical significance was reached. B, Long TE (TE, 136 ms) spectra showed significant differences at 2.02 ppm (NAA), 2.36 and 2.48 ppm (GLX), and 3.22 ppm (CHO).
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Fig 2. Case 81. Anaplastic oligoastrocytoma. A, FLAIR-weighted images show a hyperintense subcortical lesion on the right frontal lobe. B, The lesion shows slight enhancement on T1-weighted images obtained after contrast administration. C, Decrease in the apparent diffusion coefficient (ADC) is seen on the ADC map. The possibility of a cortical infarct was considered. D, 1H-MR spectroscopy at short TE shows slight increase of the mIns/NAA ratio, high CHO, and low NAA. E, 1H-MR spectroscopy at long TE shows high CHO and low NAA levels. F, Graph constructed with the mIns/NAA ratio at short TE (x axis) and CHO/NAA at long TE (y axis) of the universe (latent space) of cases of the training-set projects the case (cross) in the tumoral area. The straight line in the graph depicts the cutting point between tumor and pseudotumor on the basis of the combined ratio value (formula, x + y = 3.33). Values obtained for the classifiers were mIns/NAA ratio at short TE, 1.04 (>0.90, suggesting tumor); CHO/NAA ratio at long TE, 7.52 (>1.90, suggesting tumor), and combined ratio, 8.56 (>3.3, suggesting tumor). The lesion was an anaplastic oligoastrocytoma on the pathologic assessment.
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Fig 3. Case 68. Unspecific benign pseudotumoral mass. A, FLAIR-weighted images show enlargement and hyperintensity of the head of the right caudate nucleus and left thalamus. B, T1-weighted images after contrast administration show slight discontinuous contrast enhancement. C, 1H-MR spectroscopy at short TE. Ratios between CHO, Cr, and NAA are within the normal range. D, 1H-MR spectroscopy at long TE shows no significant anomalies in the ratios between CHO, Cr, and NAA. E, Graph constructed with the mIns/NAA ratio at short TE (x axis) and CHO/NAA ratio at long TE (y axis) of the universe (latent space) of cases of the training-set projects the case (cross) in the nontumoral area. The straight line in the graph depicts the cutting point between tumor and pseudotumor on the basis of the combined ratio value (formula, x + y = 3.33). The arrow highlights the position of the case. Values obtained for the classifiers were mIns/NAA ratio at short TE, 0.48 (<0.90, suggesting nontumor); CHO/NAA ratio at long TE, 0.55 (<1.90, suggesting nontumor); and combined ratio, 1.03 (<3.3, suggesting nontumor). The pathologic assessment of a stereotactic biopsy was "inflammatory changes." F, Follow-up with axial FLAIR images obtained in 8 months shows complete resolution of previous abnormalities in the images. Note a small hypointense area on the head of the caudate nucleus (arrow) corresponding to the biopsy area.
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