Quantitative investigation of solitary pulmonary nodules: dynamic contrast-enhanced MRI and histopathologic analysis.

Abstract

The purposes of this study were to analyze the relation between enhancement patterns on dynamic enhanced MRI and histologic microvessel patterns of solitary pulmonary nodules (SPNs) and to address the topic of false-positive findings in differentiating SPNs with dynamic MRI. Sixty-eight patients with 68 pathologically proven SPNs (diameter <or= 30 mm) underwent dynamic 1.5-T MRI. On time-signal intensity curves generated after bolus injection of contrast material, steepest slope, peak height, and enhancement ratios of signal intensity at the first, second, and fourth minutes were calculated. The relation between dynamic MRI values and microvessel density was analyzed. The morphologic differences between malignant SPNs and active inflammatory SPNs also were analyzed. Threshold dynamic MRI values for differential diagnosis were determined. The dynamic MRI values of benign SPNs were significantly lower than those of the other SPNs (p < 0.01). The enhancement ratio at the fourth minute for active inflammatory SPNs was significantly higher than that of malignant SPNs (p < 0.01). A high correlation coefficient (r = 0.87, p < 0.001) was found between steepest slope and microvessel density. With steepest slope 1.5%/s or less, benign SPNs were clearly differentiated from other SPNs. With enhancement ratio at the fourth minute 65% or less, malignant SPNs were differentiated from active inflammatory SPNs with high sensitivity (93%) and high specificity (100%). Dynamic MRI values reflect the quantitative and morphologic characteristics of microvessels in SPNs and are a useful tool for differentiating SPNs with little overlap.