A Method for Evaluating the T<sub>2</sub><sup>∗</sup>-weighting Effect in MRI

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  • Yagi Yuta
    Division of Radiology, Niigata University Medical and Dental Hospital
  • Ohkubo Masaki
    Graduate School of Health Sciences, Niigata University
  • Saito Hiroaki
    Division of Radiology, Niigata University Medical and Dental Hospital
  • Kanazawa Tsutomu
    Division of Radiology, Niigata University Medical and Dental Hospital

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Other Title
  • MRIにおけるT<sub>2</sub><sup>∗</sup>強調効果の定量的評価法
  • MRIにおけるT₂強調効果の定量的評価法
  • MRI ニ オケル T₂キョウチョウ コウカ ノ テイリョウテキ ヒョウカホウ

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Abstract

<p>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.</p>

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