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Differential diagnosis between thymoma and non-thymoma by dynamic MR imaging
1Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Purpose:
To evaluate the usefulness of dynamic MR imaging for differential diagnosis of anterior mediastinal tumors.
Material And Methods:
Fifty-nine patients with anterior mediastinal tumors were examined. According to histological diagnosis confirmed by surgery or biopsy, 31 had thymomas and 28 had non-thymoma lesions. The patients underwent dynamic MR imaging with gadopentetate dimeglumine administered as a bolus injection. Sequential images were obtained at 30-s intervals for 5 min. Significant differences in the mean peak times of time intensity curves (TICs) were found by histological type, using the Mann-Whitney test.
Results:
The mean peak time of the TIC was 1.5 min in thymoma and 3.2 min in non-thymoma cases. The difference was statistically significant. Stages I and II of thymoma showed a mean value of 1.3 min, which was significantly shorter than that of 2.5 min in stage III. Differentiation of thymoma/non-thymoma based on the peak time of dynamic MR imaging showed optimal sensitivity (79%) and specificity (84%) when defining thymomas as lesions having peak time appearing earlier than 2 min and non-thymomas later than 2.5 min, with an accuracy of 81%.
Conclusion:
Dynamic MR imaging may improve the differential diagnosis between thymoma and non-thymoma and the staging of thymoma.