Quantitative susceptibility mapping (QSM) as a means to monitor cerebral hematoma treatment

Abstract

Background: Quantitative susceptibility mapping (QSM) offers a consistent hemorrhage volume measurement independent of imaging parameters.

Purpose: To investigate the magnetic susceptibility of intracerebral hemorrhage (ICH) as a quantitative measurement for monitoring treatment in hematoma patients.

Study type: Prospective.

Population: Twenty-six patients with acute ICH were recruited and enrolled in treatment including surgery or medication (mannitol) for 1 week.

Field strength/sequence: A 3D gradient echo sequence at 3.0T.

Assessment: The hematoma volumes on computed tomography (CT) and QSM were calculated and used for correlation analysis. Magnetic susceptibility changes from pre- to posttreatment were calculated and compared to the National Institutes of Health stroke scale (NIHSS) measure of neurological deficit for each patient.

Statistical tests: Mean susceptibility values were calculated over each region of interest (ROI). A one-sample t-test was used to assess the changes of total volumes and mean magnetic susceptibility of ICH identified between pre- and posttreatment images (P < 0.05 was considered significant) and the Bland-Altman analysis with 95% limits of agreement (average difference, ±1.96 SD of the difference). Regression of volume measurements on QSM vs. CT and fitted linear regression of mean susceptibility vs. CT signal intensity for hematoma regions were conducted in all patients.

Results: Good correlation was found between hemorrhage volumes calculated from CT and QSM (CT volume = 0.94*QSM volume, r = 0.98). Comparison of QSM pre- and posttreatment showed that the mean ICH volume was reduced by a statistically insignificant amount from 5.74 cm³ to 5.45 cm³ (P = 0.21), while mean magnetic susceptibility was reduced significantly from 0.48 ppm to 0.38 ppm (P = 0.004). A significant positive association was found between changes in magnetic susceptibility values and NIHSS following hematoma treatment (P < 0.01).

Data conclusions: QSM in hematoma assessment, as compared with CT, offers a comparably accurate volume measurement; however, susceptibility measurements may enable improved monitoring of ICH treatment compared to volume measurements alone.

Level of evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:907-915.

Keywords: computed tomography; hematoma volume; intracerebral hemorrhage; magnetic resonance imaging; quantitative susceptibility mapping.