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[A Method for Evaluating the T2∗-weighting Effect in MRI]
Yuta Yagi1, Masaki Ohkubo2, Hiroaki Saito1
1Division of Radiology, Niigata University Medical and Dental Hospital.
Purpose:
To propose a method for evaluating the T2*-weighting effect in MRI.
Methods:
Multiple solutions with different concentrations of a superparamagnetic iron oxide contrast agent were made and their signal intensities on T2*-weighted images were measured. The relationship between iron concentration and signal intensity was determined, and we simulated an iron concentration map representing a simplified model of a brain microbleed and converted the pixel values in the map to signal intensity based on the determined relationship, generating a simulated T2*-weighted image. An 'S-value' parameter was defined to evaluate the low-intensity regions in the simulated image. S-values were obtained using T2*-weighted sequences acquired with different echo time (TE) values on three MRI scanners (Philips 1.5 T, GE 3.0 T, and Siemens 3.0 T). Another parameter (A-value) defined by the American Society for Testing and Materials (ASTM-F2119) for assessing artifacts was applied to evaluate the weighting effect in the T2*-weighted image of a laboratory-made susceptibility-effect phantom.
Results:
With all three scanners, the S-values increased as the TE increased, indicating enhancement of the T2*-weighting effect. For every TE, the S-values obtained for the Philips scanner were the largest, followed by those for the GE and Siemens scanners. The results of this comparative evaluation were similar to those obtained using A-values.
Conclusion:
Comparisons with the established A-value parameter showed our proposed method for the quantitative evaluation of the T2*-weighting effect using S-values to be valid. The proposed method has the advantage that the S-values do not depend on a specific susceptibility-effect phantom.
Insights
A new S-value method quantifies MRI T2*-weighting effects. Higher S-values indicate stronger T2*-weighting, consistent across scanners and validated against A-values.
Area of Science:
- Medical Imaging
- Magnetic Resonance Imaging (MRI)
Background:
- T2*-weighting is crucial for detecting microhemorrhages in MRI.
- Accurate evaluation of T2*-weighting is essential for consistent image interpretation.
Purpose of the Study:
- To propose and validate a novel method for quantitatively evaluating the T2*-weighting effect in MRI.
- To introduce an 'S-value' parameter for assessing T2*-weighted image characteristics.
Main Methods:
- Simulated T2*-weighted images of microbleeds were generated using varying iron concentrations.
- Signal intensities were measured, and an 'S-value' was defined to quantify low-intensity regions.
- S-values were acquired on 1.5T and 3.0T MRI scanners with different echo times (TE).
- The proposed S-value method was compared with the ASTM-F2119 A-value for artifact assessment.
Main Results:
- S-values increased with increasing echo time (TE), confirming enhanced T2*-weighting.
- Scanner-specific S-values were observed, with Philips showing the highest values, followed by GE and Siemens.
- Results from the S-value method correlated well with those obtained using A-values.
Conclusions:
- The proposed S-value method provides a valid and quantitative assessment of T2*-weighting in MRI.
- This method offers an advantage as S-values are independent of specific susceptibility-effect phantoms.
- The S-value parameter facilitates consistent evaluation of T2*-weighting across different MRI systems and sequences.
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