LAUSR

BACKGROUND Normal background parenchymal enhancement (BPE) is a dynamic parameter affected by multiple factors. PURPOSE To determine whether contrast agent injection rate affects the degree of BPE in women undergoing breast magnetic resonance imaging (MRI). MATERIAL AND METHODS A total of 85 patients included in our prospective study randomly received 0.1 mmol/kg gadoteridol at a rate of 3 mL/s (group A; n = 46) or 2 mL/s (group B; n = 39). Breast MRI was performed at 3T using a standard protocol including postcontrast axial 3D GRE T1-weighted sequences. Two expert breast radiologists, blinded to clinical and radiological information, independently quantified BPE on early postcontrast subtracted images, assigning a score of 1-4. Mean comparison and regression analysis were performed to assess the influence of injection rate on BPE. RESULTS Groups were homogeneous in terms of age and final BI-RADS score. The mean BPE score was significantly lower among patients in group A (mean of two readers: 1.36 vs. 1.90; P < 0.01) with 70%-72% of patients assigned a BPE score of 1, compared with 36%-38% of patients in group B. Lower BPE scores were noted with the higher flow rate in subgroup analyses of both pre- and postmenopausal women, although the effect was more evident in premenopausal women. Regression analysis confirmed that the likelihood of a BPE 1 score was significantly increased with a higher flow rate (P < 0.01). The inter-reader agreement was excellent (0.83). CONCLUSION A higher contrast agent injection flow rate (3 mL/s) during breast MRI significantly reduces the degree of BPE, potentially allowing improved diagnostic accuracy by reducing false-positive and false-negative findings.