Diagnostic accuracy of perfusion CT in differentiating brain abscess from necrotic tumor.

Objective: To evaluate the diagnostic accuracy of perfusion computed tomography (CTP) in differentiating between brain abscess and necrotic tumor.

Material And Method: Prospective study was performed in patients suspected of a space taking lesion in the brain. CTP was done at the suspected levels and post-processing measurement of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and permeability surface index (PS) were evaluated at ring enhanced area, central non-enhanced area, edema and contralateral normal brain.

Results: Seventeen patients with 21 lesions were studied. Of the 21 lesions, 12 were abscess and nine were tumors. By comparing means, only MTT at the ring enhanced area showed statistically significant difference between brain abscess and tumor (p = 0.009, 95% CI = 1.403 to 4.900). When ratio of CBV, CBF and MTT of the ring enhanced area and contralateral normal brain were analyzed (CBVr, CBFr, MTTr respectively), there were significant differences of CBVr and CBFr between the two groups (p = 0.003, 95% CI = -4.266 to -1.051 and p = 0.006, 95% CI = -9.934 to -1.969 respectively). With the threshold of CBVr more than or equal to 1.5 and CBFr more than or equal to 1, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for diagnosis of tumor were 100%, 75%, 75%, 100%, and 85.7% respectively.

Conclusion: The CTP was shown to be useful in differentiating brain abscess from tumor. With CBVr less than 1.5, tumor can be excluded.