Differentiating calcifications from cerebral microbleeds using quantitative susceptibility mapping.

OBJECTIVES

To differentiate cerebral microbleeds (CMBs) and calcifications using quantitative susceptibility mapping (QSM).

METHODS

CMBs were visualized and located using QSM from susceptibility-weighted imaging data collected on a 3-T MR scanner. Calcifications of the pineal gland and the choroid plexus were localized first using CT. All calcifications and CMBs were assessed using QSM to evaluate their magnetic susceptibility. The distribution of the magnetic susceptibility for the CMBs was determined and the CT attenuation was correlated with the mean magnetic susceptibility for the calcifications.

RESULTS

A total of 232 hypointense foci were selected from the QSM data: 121 were CMBs and 111 were calcifications. The mean magnetic susceptibility was -214 ± 112 ppb for the calcifications and 392 ± 204 ppb for the CMBs. The minimum value of magnetic susceptibility was 75 ppb for all the CMBs and the maximum value was -52 ppb for all the calcifications. The calcifications were clearly differentiable from the CMBs from the sign alone (p < 0.001). The magnetic susceptibility for the CMBs was 299 ± 133 ppb in the lobar subcortical white matter and 499 ± 220 ppb for deep CMBs in the basal ganglia, thalamus, and brainstem. There was a significant difference in the susceptibility between these two regions (p < 0.001).

CONCLUSION

The sign of the magnetic susceptibility was sufficient to differentiate calcifications and CMBs. The concentration of calcium or iron can be determined from the susceptibility value itself. The deep CMBs had higher susceptibility on average than lobar bleeds.

CLINICAL RELEVANCE STATEMENT

This study's ability to differentiate between CMBs and calcifications using QSM could enhance diagnostic accuracy, guiding more precise treatment decisions for stroke or tumor patients.

KEY POINTS

The sign of magnetic susceptibility is sufficient to differentiate calcifications and CMBs. QSM can successfully differentiate calcifications from microbleeds. The concentration of calcium or iron can be determined from the susceptibility value itself.