Rationale and Objectives
To determine the sensitivity of susceptibility-weighted imaging (SWI) for depicting hemorrhagic hypointense foci of the brain in comparison with gradient-recalled echo (GRE)- and GRE-type single-shot echo-planar imaging (GREI, GRE-EPI), and to assess the basic characteristics of the susceptibility effect by using a phantom.
Materials and Methods
We prospectively examined 16 patients (9 males, 7 females, aged 10–74 years, mean 43 years) with hypointense foci using SWI, GREI, and GRE-EPI at a 1.5-T magnetic resonance (MR) unit. The contrast-to-noise ratio (CNR), sensitivity to small hypointese foci, and artifacts were evaluated. To assess the basic characteristics of SWI, we performed a phantom study using different concentrations of superparamagnetic iron oxide (SPIO).
Results
The CNR of lesions was significantly greater for SWI than the other images ( P < .0001). SWI detected the greatest number of small hypointense foci, even in the near-skull-base and infratentorial regions. Quantitative and qualitative analyses in our clinical and phantom studies demonstrated that the degree of artifacts was similar with SWI and GREI.
Conclusion
SWI was best for detecting small hemorrhagic hypointense foci. Artifacts of SWI were similar to GREI.
The detection of hemorrhage and its breakdown products is important for the diagnosis, management, and prognostic prediction for a variety of intracranial diseases ( ). Cerebral microhemorrhage may be a marker of cerebral small-vessel disease and cerebral amyloid angiopathy and might indicate a higher risk for future intracerebral hemorrhage after thrombolysis or the use of antithrombotic drugs ( ). The detection of hemorrhage on magnetic resonance (MR) images is useful for the grading of gliomas ( ). In patients with diffuse axonal injury, the presence of hemorrhage may result in a poor prognosis ( ).
Among various imaging techniques for depicting intracranial microhemorrhage, two-dimensional T2*-weighted gradient-recalled echo imaging (GREI) is considered a reliable technique ( ). In the detection of small hemorrhagic foci in the supratentorial white matter, however, GRE-type single-shot echo-planar imaging (GRE-EPI) may be more sensitive than GREI ( ).
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Materials and methods
Clinical Study
Patients
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MR Imaging
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Table 1
Imaging Parameters of GREI, GRE-EPI, and SWI
GRE GRE-EPI SWI TR/TE/excitations 500/15/1 1000/46/1 56/40/1 Flip angle 15° 90° 25° Matrix 192 × 256 148 × 256 192 × 256 Field of view (mm) 200 × 265 200 × 265 200 × 265 Section thickness (mm) 5 5 10 ⁎ Slice gap (mm) 1 1 0 Acquisition type 2D 2D 3D Acquisition time 3 min, 27 s 4 s 4 min, 20 s
Note. SWI: susceptibility-weighted imaging, GREI: gradient-recalled echo imaging, GRE-EPI: GRE-type single-shot echo-planar imaging
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Image Interpretation
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Quantitative Analysis
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Qualitative Analysis
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Phantom Study
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Quantitative Analysis
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Qualitative Analysis
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Results
Clinical Study
Quantitative Analysis
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Qualitative Analysis
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Table 2
Comparison of Number of Small Lesion (<5.0 mm) Detected by the Three Sequences
GREI GRE-EPI SWI Only by GREI Only by GRE-EPI Only by SWI Supratentorial 287 303 419 5 0 116 Near skull base 18 11 30 2 0 15 Infratentorial 28 25 51 2 0 28
Note. SWI: susceptibility-weighted imaging, GREI: gradient-recalled echo maging, GRE-EPI: GRE-type single-shot echo-planar imaging.
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Phantom Study
Quantitative Analysis
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Qualitative Analysis
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Discussion
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Conclusion
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