Differential diagnosis between thymoma and non-thymoma by dynamic MR imaging.
OBJECTIVE
To evaluate the usefulness of dynamic MR imaging for differential diagnosis of anterior mediastinal tumors.


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%.


CONCLUSIONS
Dynamic MR imaging may improve the differential diagnosis between thymoma and non-thymoma and the staging of thymoma.
Sakai
S
S
Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Murayama
S
S
Soeda
H
H
Matsuo
Y
Y
Ono
M
M
Masuda
K
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008479:Mediastinal Neoplasms / Q000175:diagnosis; D008875:Middle Aged; D009367:Neoplasm Staging; D012680:Sensitivity and Specificity; D013945:Thymoma / Q000175:diagnosis*; D013953:Thymus Neoplasms / Q000175:diagnosis*
D003287:Contrast Media; D019786:Gadolinium DTPA