T2* mapping at 3.0T MRI for differentiation of papillary thyroid carcinoma from benign thyroid nodules.

Purpose: To study the quantitative T2* mapping for thyroid nodules and to explore the use of T2* values to differentiate papillary thyroid carcinoma (PTC) from benign thyroid nodules, with histopathological examination as a reference standard.

Materials And Methods: Twenty-eight consecutive patients with thyroid nodules were subjected to a 3.0T magnetic resonance imaging (MRI) examination. T2 * mapping was acquired using six echo times with a multiecho fast field echo (mFFE) sequence and constructed by exponentially fitting the multiecho T2* images pixel-by-pixel. The quality of the native T2* image was evaluated. An independent sample t-test was used to evaluate the statistical difference of the mean T2* value and the mean ratio of lesion to contralateral normal tissue between PTC and benign thyroid nodules. A receiver operating characteristic (ROC) curve was used to calculate the sensitivity and specificity.

Results: The T2* value (mean: 21.73 ± 2.09 msec) and the ratio (mean: 1.61 ± 0.11) of PTC group were both significantly lower (P < 0.001) than those of the benign group (mean T2* value: 28.78 ± 5.02 msec, mean ratio: 2.18 ± 0.43). Applying a threshold value of 25.00 msec for T2* values and 1.795 for the ratio of lesion regions to normal tissue regions to identify PTC yielded a sensitivity of 84.2% and 89.5%, respectively, and a specificity of 100% for both.

Conclusion: T2* mapping can potentially provide quantitative information to separate PTC from benign thyroid nodules.