Benign and malignant breast lesions: efficacy of real time contrast-enhanced ultrasound vs. magnetic resonance imaging.

Purpose: To assess the efficacy of low mechanical index (MI) real time grey scale contrast-enhanced US (CEUS) in the differentiation of breast lesions in comparison to Magnetic Resonance Imaging (MRI).

Materials And Methods: 50 lesions previously detected at mammography or conventional US were evaluated by means of CEUS and MRI. Contrast-enhanced examinations were performed with a dedicated equipment (Esatune, Esaote, Genoa, Italy), before and after injection of 4.8 ml of Sonovue (Bracco, Milan, Italy). MRI was conducted with a 1.5 T equipment (Siemens Vision Plus, Erlangen, Germany) with bilateral dedicated superficial coil, on T2w STIR and 3D Flash T1w before and 1, 2, 3, 4, 5 minutes after the administration of contrast agent (Gd-DTPA, 1.5 ml/kg). Wash-in and wash-out curves were assessed for both procedures. A specific sonographic quantification software (Qontrast, Bracco, Milan, Italy), based on pixel by pixel signal intensity over time, was used to obtain contrast-enhanced sonographic perfusion maps for each lesion. Mc Nemar test was then calculated.

Results: 24 invasive ductal carcinomas, 18 fibroadenomas, 4 fibro-cystic dysplasias, 1 mucinous carcinoma, 1 invasive ducto-lobular carcinoma, 1 intraductal florid papillomatosis and 1 phylloides tumour were diagnosed. Contrast-enhanced sonographic patterns correlated well with those provided by MRI. Sensitivity, specificity, and accuracy of US were: 69.2 %, 66.7 %, and 68 %, respectively. According to the different contrast enhancement patterns and the resulting perfusion maps, all the malignant lesions and 9 out of 12 benign lesions were correctly diagnosed, thus resulting in 87.5 % of specificity and 100 % of sensitivity. Regarding the specificity, there is no difference between US and CEUS with McNemar (p = 0.18). Regarding sensitivity, the difference between contrast-enhanced US and US is significant as calculated with McNemar test (p = 0.013). The three lesions which were incorrectly classified as malignant were two hypervascularised fibroadenomas in young women and a phylloides tumour.

Conclusion: CEUS seems to be a reliable method to differentiate breast lesions, since it provides typical enhancement patterns. Contrast sonographic perfusion curves correlate well with MRI wash in--wash out curves.