Quantitative Susceptibility Mapping in Cerebral Cavernous Malformations: Clinical Correlations

Abstract

Background and purpose: Quantitative susceptibility mapping has been shown to assess iron content in cerebral cavernous malformations. In this study, our aim was to correlate lesional iron deposition assessed by quantitative susceptibility mapping with clinical and disease features in patients with cerebral cavernous malformations.

Materials and methods: Patients underwent routine clinical scans in addition to quantitative susceptibility mapping on 3T systems. Data from 105 patients met the inclusion criteria. Cerebral cavernous malformation lesions identified on susceptibility maps were cross-verified by T2-weighted images and differentiated on the basis of prior overt hemorrhage. Mean susceptibility per cerebral cavernous malformation lesion (χ̄lesion) was measured to correlate with lesion volume, age at scanning, and hemorrhagic history. Temporal rates of change in χ̄lesion were evaluated in 33 patients.

Results: Average χ̄lesion per patient was positively correlated with patient age at scanning (P < .05, 4.1% change with each decade of life). Cerebral cavernous malformation lesions with prior overt hemorrhages exhibited higher χ̄lesion than those without (P < .05). Changes in χ̄lesion during 3- to 15-month follow-up were small in patients without new hemorrhage between the 2 scans (bias = -0.0003; 95% CI, -0.06-0.06).

Conclusions: The study revealed a positive correlation between mean quantitative susceptibility mapping signal and patient age in cerebral cavernous malformation lesions, higher mean quantitative susceptibility mapping signal in hemorrhagic lesions, and minimum longitudinal quantitative susceptibility mapping signal change in clinically stable lesions. Quantitative susceptibility mapping has the potential to be a novel imaging biomarker supplementing conventional imaging in cerebral cavernous malformations. The clinical significance of such measures merits further study.

Fig 1.

Lesional mean susceptibility per patient (parts per million) is positively correlated with patient age at scanning.

Fig 2.

A, Mean susceptibility comparison between lesions with and without prior hemorrhages in all patients. B, Mean susceptibility comparison between lesions with and without prior hemorrhages only in patients with familial CCM. C, Receiver operating characteristics analysis indicates that QSM is a good differentiator of lesions with and without prior hemorrhage in cases with familial CCM. D, A Bland-Altman plot of the repeat QSM measurements. Changes in susceptibility were small in clinically stable patients within a short follow-up.

Fig 3.

Each subfigure exhibits a separate CCM case. A, QSM map depicts the appearance of a CCM lesion before and after the operation. B, A colorized QSM map depicting a big increase in iron deposition in the same CCM lesion in a short time, after 2 recent overt hemorrhages. C, 3D rendering of a CCM lesion in repeat scans after a known hemorrhage, depicting the shrinkage in overall lesion volume during the short-term recovery period in a patient following a hemorrhage, but with increased mean susceptibility.

Fig 4.

Spatial comparison results between QSM and conventional MR imaging. A, Susceptibility distribution of different blood breakdown by-products within CCM lesions. B, Illustration of blood breakdown by-product identification and correlation with the corresponding QSM measurements. ROIs for different blood by-products are shown in the T2-weighted image with color (blue, intracellular methemoglobin; brown, intracellular methemoglobin and hemosiderin; cyan, hemosiderin).