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Brain Abscess and Necrotic Brain Tumor: Discrimination with Proton MR Spectroscopy and Diffusion-Weighted Imaging

Ping H. Laia, Jih T. Hob, Wei L. Chena, Shu S. Hsub, Jyh S. Wangc, Huay B. Pana and Chien F. Yanga

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



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  		FIG 1. Images obtained in a 69-year-old man with Klebsiella pneumoniae bacteremia, renal abscess, brain abscess, and endophthalmitis of the left eye.

A, Axial T1-weighted image (500/30[TR/TE]) before administration of contrast material.

B, Axial T2-weighted image (4000/100). The 2 x 2 x 2 cm voxel (box) in the lesion, adjacent brain tissue, and neighboring fat represents the 1H-MRS volume of interest.

C, Axial contrast-enhanced T1-weighted MR image (500/30) shows a regular thin-walled ring-enhanced abscess approximately 9 mm in diameter in the superficial brain surface of right parietal region. Endophthalmitis in the left eye shows enhancement after contrast agent administration.

D, Axial diffusion-weighted (10,000/93; b = 1000 s/mm2) image shows marked hyperintensity in the abscess cavity and the left eye.

E, ADC map reveals slight hypointensity, representing restricted diffusion in the corresponding region.

F, In vivo 1H-MR spectrum (2000/270) was unacceptable because of contamination from neighboring fat and a very small lesion. 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. A hump resonance (1–1.5 ppm) was identified, and lactate (Lac) peak contaminated by neighboring fat with a lipid (Lip) peak were suggested. Multiple small peaks at various frequencies are present; these peaks may represent noise or unassigned metabolites.



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  		FIG 2. Images obtained in a 50-year-old man with surgically proven pyogenic brain abscess in the right basal ganglion.

A, Axial T1-weighted image (500/30) before administration of contrast material.

B, Axial T2-weighted image (4000/100). The 2 x 2 x 2 cm voxel (box) in the center of the lesion represents the 1H-MRS volume of interest.

C, Axial contrast-enhanced T1-weighted (500/30) MR image shows a ring-shaped cystic lesion and surrounding edema.

D, Axial diffusion-weighted (10,000/93; b = 1000 s/mm2) image shows marked hyperintensity in the abscess cavity and slight iso- to hypointensity surrounding the edema.

E, ADC map reveals hypointensity in the abscess cavity, representing restricted diffusion, and hyperintense areas surrounding the edema.

F and G, In vivo 1H spectra (2000/270 and 135) from the abscess cavity show resonances representing acetate (Ac), alanine (Ala), lactate (Lac), and amino acids (AA). At a TE of 135 (G), 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.



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  		FIG 3. Images obtained 35 days after the start of initial antibiotic treatment in a 45-year-old man with multiple pyogenic brain abscesses.

A, Axial T1-weighted image (500/30) before administration of contrast material.

B, Axial T2-weighted image (4000/100). The 2 x 2 x 2 cm voxel (box) represents 1H-MRS volume of interest.

C, Axial contrast-enhanced T1-weighted (500/30) MR image shows two ring-shaped enhanced lesions in the right basal ganglion and left frontal lobe.

D, Axial diffusion-weighted (10,000/93; b = 1000 s/mm2) image shows markedly high signal intensity in the abscess cavity and slightly iso- to hypointense surrounding edema.

E, ADC map reveals low signal intensity in the abscess cavity, representing restricted diffusion, and hyperintense areas surrounding the edema.

F and G, In vivo 1H spectra (2000/270 and 135) from the abscess cavity show a lactate (Lac) peak (1.3 ppm) that is inverted at a TE of 135 and a lipid (Lip) peak (0.8–1.2 ppm). Note the similarity of this spectral pattern to that of a necrotic brain tumor.



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  		FIG 4. Images obtained in a 67-year-old man with a pathologically proven right cerebellar metastasis from primary lung adenocarcinoma.

A, Axial T1-weighted image (500/30) before administration of contrast material.

B, Axial T2-weighted image (4000/100). The 2 x 2 x 2 cm voxel (box) in the center of the lesion represents the 1H-MRS volume of interest.

C, Axial contrast-enhanced T1-weighted (500/30) MR image shows a ring-enhanced lesion in the right cerebellum.

D, Axial diffusion-weighted (10,000/93; b = 1000 s/mm2) image shows markedly low signal intensity in the necrotic part of the tumor.

E, ADC map reveals high signal intensity in the necrotic part of the tumor that is similar to that of CSF, reflecting marked diffusion.

F and G, In vivo 1H spectra (2000/270 and 135) from the necrotic center of the tumor show a lactate (Lac) peak at 1.3 ppm that is inverted at a TE of 135.





Copyright © 2008 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X