Quantitative susceptibility mapping in patients with systemic lupus erythematosus: detection of abnormalities in normal-appearing basal ganglia.

OBJECTIVES: To evaluate whether quantitative susceptibility mapping (QSM) can be employed to detect abnormalities within normal-appearing basal ganglia on conventional MRI in patients with neuropsychiatric systemic lupus erythematosus (NPSLE).

METHODS: For 33 SLE patients (13 NPSLE and 20 non-NPSLE patients) and 23 age/sex-matched controls, two radiologists independently measured the mean QSM and R2* values in various brain structures that appeared to be normal on conventional MR images. These values in each brain structure were compared among the two SLE groups and controls.

RESULTS: Regarding the putamen, the NPSLE patients showed significantly higher QSM values than the non-NPSLE patients and controls (p < 0.05). For the lateral globus pallidus, both SLE groups showed significantly higher QSM values than the controls (p < 0.05). The R2* values were not significantly different between both SLE groups. The NPSLE patients showed a significant correlation between the mean QSM values in putamen and the disease duration (r = 0.63, p < 0.05). For the interobserver agreement, the QSM value was superior to the R2* value (0.690 vs. 0.446, Kendall W value).

CONCLUSIONS: QSM can be used to identify increased susceptibility of the basal ganglia appearing to be normal on conventional MR images in NPSLE patients.

KEY POINTS: • QSM values in the putamen are significantly higher in NPSLE than non-NPSLE. • NPSLE patients show correlation between QSM values in the putamen and disease duration. • QSM is more sensitive than R2* mapping for detecting subtle changes.