Discriminating pyogenic brain abscesses, necrotic glioblastomas, and necrotic metastatic brain tumors by means of susceptibility-weighted imaging.

OBJECTIVES

To investigate the feasibility of using susceptibility-weighted imaging (SWI) to discriminate abscesses and necrotic tumours.

METHODS

Twenty-one patients with pyogenic abscesses, 21 patients with rim-enhancing glioblastomas and 23 patients with rim-enhancing metastases underwent SWI. Intralesional susceptibility signal (ILSS) was analyzed employing both qualitative (QL) and semi-quantitative (SQ) methods. Logistic regression models and receiver operating characteristic analysis were used to demonstrate the discriminating power.

RESULTS

In QL analysis, ILSSs were seen in 12 of 21 abscesses, in 20 of 21 glioblastomas, and in 16 of 23 metastases. In SQ analysis, a low degree of ILSS (85.8 %) was in the majority of abscesses and a high degree of ILSS (76.2 %) was in the majority of glioblastomas. SQ model was significantly better than QL model in distinguishing abscesses from glioblastomas (P < .001). A derived ILSS cutoff grade of 1 or less was quantified as having a sensitivity of 85.7 %, specificity of 90.5 %, accuracy of 88.1 %, PPV of 90.0 %, and NPV of 86.4 % in distinguishing abscesses from glioblastomas.

CONCLUSIONS

A high-grade ILSS may help distinguish glioblastomas from abscesses and necrotic metastatic brain tumours. The lack of ILSS or low-grade ILSS can be a more specific sign in the imaging diagnosis of abscesses.

KEY POINTS

• ILSS of SWI can contribute to differential diagnosis of rim-enhanced mass. • Low-grade ILSS can be a more specific sign in abscesses. • High-grade ILSS may help distinguish necrotic glioblastomas from abscesses. • ILSS spreads across the four ILSS categories in metastases.