Parametric MR Dynamic Imaging for Breast Lesions Characterization and Prediction of Lymph Nodes Involvement

The main purpose of this study was to evaluate Gd-DTPA kinetics for the differential diagnosis between malignant and benign breast lesions. As a secondary aim, Gd-DTPA kinetics in malignant lesions was tested for predicting axillary lymph nodes involvement. Eighty-eight patients who underwent MRI for suspected breast tumor were selected from our database. All patients underwent the same acquisition protocol consisting of pre-contrast and dynamic contrastenhanced MRI. For all of them clinical and histopathological data were available. MR studies were performed on the same 1.5T scanner with a standard dedicated breast coil. Pre- and post-contrast dynamic images were used to calculate R1, R2 relaxation rates and proton density maps. The maximum influx rate (MIR) as well as the corresponding time (TMIR) were derived using R1 relaxation rate maps and relative changes as a function of time. Histopatological analysis led to the diagnosis of 46 breast carcinomas and 42 benign lesions. All breast carcinomas and 24 out of 42 benign lesions showed contrast-enhancement. The mean MIR was 0.75±0.14 (SD) sec-2 in malignant tumors and 0.53±0.14 (SD) sec-2 in contrast-enhancing benign breast lesions (p<0.0001). The TMIR was 1.40±0.43 min and 3.01±1.92 min (mean±SD) in enhancing malignant and benign lesions, respectively (p<0.0001). In malignant tumors, TMIR was not significantly different in node negative and node positive carcinomas whereas MIR was significantly lower in node negative carcinomas (0.67±0.11 versus 0.83±0.12 respectively, p<0.0001). Our findings suggest that quantitative assessment of Gd-DTPA kinetics may be an additional tool characterized for enhancing breast lesions and for predicting axillary lymph nodes involvement in malignant breast carcinoma.