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Pyogenic Brain Abscess: Findings from In Vivo 1.5-T and 11.7-T In Vitro Proton MR Spectroscopy

Ping H. Laia, Kun T. Lic, Shu S. Hsub, Chia C. Hsiaoa, Chi W. Yipb, S. Dingc, Lee R. Yeha and Huay B. Pana

a Department of Radiology, Veterans General Hospital-Kaohsiung, National Yang-Ming University, Taiwan
b Department of Neurosurgery, Veterans General Hospital-Kaohsiung, National Yang-Ming University, Taiwan
c the Department of Chemistry, National Sun Yat-Sen University, Taiwan, Republic of China



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  		FIG 1. Patient 6. A 43-year-old man with surgically proved pyogenic brain abscess in the right basal ganglion secondary to Eubacterium lentum (obligate anaerobe) infection.

A, Axial contrast-enhanced T1-weighted MR image (500/30) shows a ring-shaped cystic lesion and surrounding edema. The 2 x 2 x 2-cm voxel (box) in the center of the lesion represents the 1H MR spectroscopic volume of interest.

B and C, In vivo 1H MR spectra (TR/TE 1600/270 [B] and 1600/135 [C]) from the abscess cavity show spectral pattern A, which represents succinate (Succ), acetate (Ac), alanine (Ala), lactate (Lac), and amino acids (AA). At a TE of 135 ms (C), the phase reversal resonances are well depicted at 1.5, 1.3, and 0.9 ppm, which confirms the assignment to alanine, lactate, and amino acids, respectively.

D and E, One-dimensional, in vitro, single-pulse (D) and spin-echo (TE = 135 ms; E) spectra of the pus removed from the abscess cavity show the prominent resonance for acetate (Ac), as well as signals for succinate (Succ), alanine (Ala), lactate (Lac), amino acids (AA) at 0.9 and 3.75 ppm, leucine (leu), lysine (lys) at 1.73 and 3.0 ppm, glutamate/glutamine (Glx) at 2.09–2.36 ppm, glycine (gly) at 3.55 ppm, and taurine (Tau) at 3.24 and 3.42 ppm. Alanine is equally prominent as lactate in vitro, compared with the in vivo study. Note the phase reversal at 1.5, 1.3, and 0.9 ppm, suggesting alanine, lactate, and amino acids, respectively, in the spin-echo (135 ms) spectrum (E).

F, In vitro 2D COSY spectrum of the pus obtained from the abscess cavity assigns leucine (L), isoleucine (I), valine (V), lipids (Lip), and lysine (Lys) unambiguously. COSY spectrum shows the J-couplings between amino acids and other metabolites, as well as the difference between the coupling values of amino acids and other metabolites. The individual amino acids (e.g., leucine, isoleucine, and valine) can be identified only through 2D COSY. Ala indicates alanine; Glx, glutamate/glutamine; Lac, lactate; Tau, Taurine.



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  		FIG 2. Patient 14. A 78-year-old woman with surgically proved pyogenic brain abscess and ventriculitis in the right temporal region secondary to Pseudomonas aeruginosa (aerobe) infection.

A, Axial contrast-enhanced T1-weighted MR image (500/30) shows a regular thin-walled ring-enhanced cystic lesion and adjacent temporal horn ventricular enhancement and surrounding edema. The 2 x 2 x 2-cm voxel (box) in the center of the lesion represents the 1H MR spectroscopic volume of interest.

B and C, In vivo 1H spectra (TR/TE 1600/270 [B] and 1600/135 [C]) from the abscess cavity show spectral pattern B with only two resonance peaks identified; however, the phase reversal of the amino acid (AA) signal at 0.9 ppm is depicted on the MR spectrum obtained with a 135-msec TE (C), which is indicative of a pyogenic brain abscess. Lac inidcates lactate.

D and E, One-dimensional, in vitro, single-pulse (D) and spin-echo (TE = 135 ms; E) spectra of the pus removed from the abscess cavity show the signals for lactate (Lac), amino acids (AA), alanine (Ala), glutamate/glutamine (Glx), leucine (leu), and lysine (lys). Alanine is present and more prominent in vitro, compared with the in vivo study. Note the phase reversal at 1.5, 1.3, and 0.9 ppm, suggesting alanine, lactate, and amino acids, respectively, in the spin-echo (135 ms) spectrum.

F, In vitro 2D COSY spectrum of the pus obtained from the abscess cavity assigns leucine (L), isoleucine (I), valine (V), lipids (Lip), and lysine (Lys) unambiguously. The individual amino acids (e.g., leucine, isoleucine, and valine) can be identified only through 2D COSY. Ala indicates alanine; Glx, glutamate/glutamine; Lip, lipid; Lys, lysine; Tau, Taurine.



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  		FIG 3. Patient 15. A 72-year-old man with Streptococcus mitis (aerobe) bacteremia, infective endocarditis, and multiple miliary pyogenic brain abscesses.

A, Axial contrast-enhanced T1-weighted MR image shows numerous miliary nodules with ring enhancement. The 2 x 2 x 2-cm voxel (box) in the lesion and adjacent brain tissue represents the 1H MR spectroscopic volume of interest.

B and C, In vivo 1H spectra (TR/TE 1600/270 [B] and 1600/135 [C]) show spectral pattern C with a lactate (Lac) peak (1.3 ppm) that is inverted at a TE of 135. The resonances of choline (Cho), creatine (Cr), and N-acetylaspartate (NAA) were interpreted to be caused by partial volume effects of the adjacent brain tissue. The phase reversal does not follow the classic pattern in this case because of the presence of some phase distortion, which presumably originated from the eddy current effect. Multiple small peaks at various frequencies are present; these peaks may represent noise or unassigned metabolites.

D, Axial contrast-enhanced T1-weighted MR image obtained 3 months later shows almost complete remission of the formation of diffuse abscesses after antibiotics.





Copyright © 2009 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X