Solitary pulmonary nodules: potential role of dynamic MR imaging in management initial experience

To evaluate the utility of dynamic magnetic resonance (MR) imaging in the management of solitary pulmonary nodules (SPNs).

Fifty-eight patients with 58 pathologic analysis-proved SPNs (diameter < 30 mm) underwent dynamic 1.5-T MR imaging. The 58 SPNs were classified into three groups at pathologic analysis: malignant SPNs (n = 38), active infections (n = 10), or benign SPNs (n = 10). From signal intensity-time curves generated after the bolus injection of contrast material, the maximum relative enhancement ratio and slope of enhancement were calculated and statistically compared among the three groups. Threshold values of these two dynamic MR indexes were determined on the basis of positive differentiations.

The mean relative enhancement ratio and mean slope of enhancement for the malignant SPN group were significantly higher than those for the benign SPN group and significantly lower than those for the active infection group (P <.05). With 0.15 as the threshold maximum relative enhancement ratio for distinguishing the malignant SPN and active infection groups from the benign SPN group, the sensitivity, specificity, and accuracy were 100%, 70%, and 95%, respectively. With 0.025/sec as the threshold slope of enhancement, all SPNs with malignancy and active infection were clearly distinguished from benign SPNs.

Dynamic MR indexes were useful in the differentiation between SPNs that necessitated further evaluation or treatment (malignancy and active infection) and SPNs that did not necessitate further evaluation or treatment (benign nodules).