Intracranial Calcifications and Hemorrhages: Characterization with Quantitative Susceptibility Mapping

To compare gradient-echo (GRE) phase magnetic resonance (MR) imaging and quantitative susceptibility mapping (QSM) in the detection of intracranial calcifications and hemorrhages. This retrospective study was approved by the institutional review board. Thirty-eight patients (24 male, 14 female; mean age, 33 years +/- 16 [standard deviation]) with intracranial calcifications and/ or hemorrhages diagnosed on the basis of computed tomography (CT), MR imaging (interval between examinations, 1.78 days +/- 1.31), and clinical information were selected. GRE and QSM images were reconstructed from the same GRE data. Two experienced neuroradiologists independently identified the calcifications and hemorrhages on the QSM and GRE phase images in two randomized sessions. Sensitivity, specificity, and interobserver agreement were computed and compared with the McNemar test and kappa coefficients. Calcification loads and volumes were measured to gauge intermodality correlations with CT. A total of 156 lesions were detected: 62 hemorrhages, 89 calcifications, and five mixed lesions containing both hemorrhage and calcification. Most of these lesions (146 of 151 lesions, 96.7%) had a dominant sign on QSM images suggestive of a specific diagnosis of hemorrhage or calcium, whereas half of these lesions (76 of 151, 50.3%) were heterogeneous on GRE phase images and thus were difficult to characterize. Averaged over the two independent observers for detecting hemorrhages, QSM achieved a sensitivity of 89.5% and a specificity of 94.5%, which were significantly higher than those at GRE phase imaging (71% and 80%, respectively; P < .05 for both readers). In the identification of calcifications, QSM achieved a sensitivity of 80.5%, which was marginally higher than that with GRE phase imaging (71%; P = .08 and .10 for the two readers), and a specificity of 93.5%, which was significantly higher than that with GRE phase imaging (76.5%; P < .05 for both readers). QSM achieved significantly better interobserver agreements than GRE phase imaging in the differentiation of hemorrhage from calcification (kappa: 0.91 vs 0.55, respectively; P < .05). QSM is superior to GRE phase imaging in the differentiation of intracranial calcifications from hemorrhages and with regard to the sensitivity and specificity of detecting hemorrhages and the specificity of detecting calcifications.