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Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging
Ping H Lai1, Jih T Ho, Wei L Chen
1Department of Radiology, Veterans General Hospital-Kaohsiung, National Yang-Ming University, National Sun Yat-Sen University, Kaohsiung, Taiwan.
Background And Purpose:
Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or MR imaging. We compared findings of proton MR spectroscopy ((1)H-MRS) with those of diffusion-weighted imaging to determine which technique was more effective for this differential diagnosis.
Methods:
Fourteen patients (necrotic or cystic tumor [n = 7]; pyogenic abscess [n = 7]) who underwent 1.5-T (1)H-MRS and diffusion-weighted imaging and had findings of ring-shaped enhancement after contrast agent administration were enrolled in this study. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 1000 s/mm(2)). The apparent diffusion coefficient and ratio were also measured.
Results:
Spectra for two patients were unacceptable because of either poor shimming conditions or contamination from neighboring fat. Spectra in three of five patients with abscess had lactate, amino acids (including valine, alanine, and leucine), and acetate peaks; one of the three spectra had an additional peak of succinate. In one patient with abscess treated by antibiotics, only lactate and lipid peaks were detected. Spectra for four of seven patients with cystic or necrotic tumors showed only lactate peaks. Lactate and lipids were found in three patients with tumors. Hyperintensity was seen in all the pyogenic abscess cavities and hypointensity in all the cystic and necrotic tumors on diffusion-weighted images.
Conclusion:
(1)H-MRS and diffusion-weighted imaging are useful for differentiating brain abscess from brain tumor, but the latter requires less time and is more accurate than is (1)H-MRS. (1)H-MRS is probably more limited in cases of smaller peripheral lesions, skull base lesions, and treated abscesses.
Insights
Proton MR spectroscopy and diffusion-weighted imaging aid in differentiating brain abscesses from tumors. Diffusion-weighted imaging is faster and more accurate than proton MR spectroscopy for this diagnosis.
Area of Science:
- Neuroradiology
- Medical imaging
- Neuro-oncology
Background:
- Differentiating pyogenic brain abscesses from cystic or necrotic tumors can be challenging using conventional CT or MR imaging.
- Proton MR spectroscopy ((1)H-MRS) and diffusion-weighted imaging (DWI) offer advanced techniques for improved diagnostic accuracy.
Purpose of the Study:
- To compare the effectiveness of (1)H-MRS and DWI in distinguishing between pyogenic brain abscesses and cystic or necrotic tumors.
- To evaluate which imaging technique provides more accurate differential diagnostic information.
Main Methods:
- A study involving 14 patients (7 with abscess, 7 with tumor) who underwent 1.5-T (1)H-MRS and DWI.
- Diffusion-weighted imaging utilized a single-shot spin-echo echo-planar pulse sequence with b = 1000 s/mm(2).
- Apparent diffusion coefficient (ADC) and ADC ratio were measured for quantitative analysis.
Main Results:
- (1)H-MRS revealed characteristic peaks (lactate, amino acids, acetate) in some abscesses, but results were variable, especially in treated cases.
- Diffusion-weighted imaging showed hyperintensity in all abscess cavities and hypointensity in all tumors.
- DWI demonstrated higher accuracy and was faster than (1)H-MRS for differential diagnosis.
Conclusions:
- Both (1)H-MRS and DWI are valuable tools for differentiating brain abscess from brain tumor.
- Diffusion-weighted imaging is superior to (1)H-MRS in terms of speed and accuracy.
- (1)H-MRS may have limitations with smaller lesions, skull base lesions, and treated abscesses.