Quantitative susceptibility mapping improves cerebral microbleed detection relative to susceptibility-weighted images
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Published on: June 8, 2017
Kyuwon Lee1, Brian Ellison1, Magdy Selim2
1Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
Background And Purpose:
Cerebral microbleed (CMB) detection impacts disease diagnosis and management. Susceptibility-weighted imaging (SWI) MRI depictions of CMBs are used with phase images (SWIP) to distinguish blood from calcification, via qualitative intensity evaluation (bright/dark). However, the intensities depicted for a single lesion can vary within and across consecutive SWIP image planes, impairing the classification of findings as a CMB. We hypothesize that quantitative susceptibility mapping (QSM) MRI, which maps tissue susceptibility, demonstrates less in- and through-plane intensity variation, improving the clinician's ability to categorize a finding as a CMB.
Methods:
Forty-eight patients with acute intracranial hemorrhage who received multi-echo gradient echo MRI used to generate both SWI/SWIP and morphology-enabled dipole inversion QSM images were enrolled. Five hundred and sixty lesions were visually classified as having homogeneous or heterogeneous in-plane and through-plane intensity by a neuroradiologist and two diagnostic radiology residents using published rating criteria. When available, brain CT scans were analyzed for calcification or acute hemorrhage. Relative risk (RR) ratios and confidence intervals (CIs) were calculated using a generalized linear model with log link and binary error.
Results:
QSM showed unambiguous lesion signal intensity three times more frequently than SWIP (RR = 0.3235, 95% CI 0.2386-0.4386, p<.0001). The probability of QSM depicting homogeneous lesion intensity was three times greater than SWIP for small (RR = 0.3172, 95% CI 0.2382-0.4225, p<.0001), large (RR = 0.3431, 95% CI 0.2045-0.5758, p<.0001), lobar (RR = 0.3215, 95% CI 0.2151-0.4805, p<.0001), cerebellar (RR = 0.3215, 95% CI 0.2151-0.4805, p<.0001), brainstem (RR = 0.3100, 95% CI 0.1192-0.8061, p = .0163), and basal ganglia (RR = 0.3380, 95% CI 0.1980-0.5769, p<.0001) lesions.
Conclusions:
QSM more consistently demonstrates interpretable lesion intensity compared to SWIP as used for distinguishing CMBs from calcification.
Insights
Quantitative susceptibility mapping (QSM) MRI provides clearer imaging for cerebral microbleed (CMB) detection than susceptibility-weighted imaging phase images (SWIP). QSM MRI demonstrates more consistent lesion intensity, aiding in differentiating CMBs from calcifications.
Area of Science:
- Radiology and Medical Imaging
- Neuroimaging
- Biomedical Engineering
Background:
- Cerebral microbleed (CMB) detection is crucial for diagnosing and managing neurological diseases.
- Susceptibility-weighted imaging phase images (SWIP) are currently used for CMB detection, but intensity variations can hinder accurate classification.
- Distinguishing CMBs from calcifications is challenging due to variable lesion intensities in SWIP.
Purpose of the Study:
- To evaluate the effectiveness of quantitative susceptibility mapping (QSM) MRI in improving the clarity and consistency of CMB detection compared to SWIP.
- To assess whether QSM reduces in-plane and through-plane intensity variations for better lesion characterization.
- To determine if QSM enhances the ability to differentiate cerebral microbleeds from calcifications.
Main Methods:
- Forty-eight patients with acute intracranial hemorrhage underwent multi-echo gradient echo MRI.
- Both SWIP and morphology-enabled dipole inversion QSM images were generated.
- Five hundred and sixty lesions were analyzed for intensity homogeneity/heterogeneity, with comparison to CT scans when available. Statistical analysis used generalized linear models.
Main Results:
- QSM demonstrated unambiguous lesion signal intensity three times more frequently than SWIP (RR = 0.3235, p<.0001).
- QSM showed significantly greater probability of depicting homogeneous lesion intensity across various lesion sizes and locations (p<.0001 for most).
- The consistency of interpretable lesion intensity was markedly higher with QSM.
Conclusions:
- Quantitative susceptibility mapping (QSM) MRI offers more consistent and interpretable lesion intensity compared to SWIP for CMB detection.
- QSM MRI improves the differentiation of cerebral microbleeds from calcifications.
- QSM represents a valuable advancement in neuroimaging for CMB analysis.
