Black Dipole or White Dipole: Using Susceptibility Phase Imaging to Differentiate Cerebral Microbleeds from Intracranial Calcifications

BACKGROUND AND PURPOSE:

Phase imaging helps determine a lesion's susceptibility. However, various inhomogenous phase patterns could be observed in the serial phase images of a lesion and render image interpretation challenging. We evaluated the diagnostic accuracy of differentiating cerebral microbleeds and calcifications from phase patterns in axial locations.

MATERIALS AND METHODS:

This study retrospectively enrolled 31 consecutive patients undergoing both CT and MR imaging for acute infarction exhibiting dark spots in gradient-echo magnitude images. Six patients had additional quantitative susceptibility mapping images. To determine their susceptibility, 2 radiologists separately investigated the phase patterns in the border and central sections and quantitative susceptibility mapping of dark spots. Sensitivity and specificity were compared using the McNemar test. Interobserver reliability and correlation analysis were determined using the κ coefficient and Pearson correlation coefficient, respectively.

RESULTS:

Among 190 gradient-echo dark spots, 62 calcifications and 128 cerebral microbleeds were detected from CT. Interobserver reliability was higher for the border phase patterns (κ = 1) than for the central phase patterns (κ = 0.77, P < .05). The sensitivity and specificity of the border phase patterns in identifying calcifications were higher than those of the central phase patterns (98.4% and 100% versus 79% and 83.6%), particularly for lesions >2.5 mm in diameter (100% and 100% versus 66.7% and 61.1%). The same values were obtained using quantitative susceptibility mapping for identification (100% and 100%). A high correlation between the size and susceptibility of cerebral microbleeds and calcifications suggested that greater phase changes may be caused by larger lesions.

CONCLUSIONS:

The border phase patterns were more accurate than the central phase patterns in differentiating calcifications and cerebral microbleeds and was as accurate as quantitative susceptibility mapping.