Preoperative MRI for Evaluation of Extent of Disease in IDC Compared to ILC.

OBJECTIVES: The purpose of this study was to assess the incremental value of preoperative breast MRI over mammography and US in depicting the accurate extent of disease in invasive duct carcinoma (IDC) compared to invasive lobular carcinoma (ILC). PATIENTS AND METHODS: Retrospective analysis of pre-operative mammography, US and MRI was performed in 239 patients with either IDC (n = 193) or ILC (n = 46). Images were evaluated for solitary, multifocal or multi centric disease and compared for concordance with postsurgical pathology. Discordance was documented as either overestimation or underestimation. Two tailed paired T and Fischer's exact tests were used for analysis. RESULTS: Multifocality was present on pathology in 35% and 61% of patients with IDC and ILC (P < .05) and multicentricity in 23% and 41% respectively (P = .84). In ILC, MRI demonstrated better concordance with pathology compared to mammography and US (89%, 44%, 49% for multifocality [P < .05] and 80.5%, 63%, 71% for multicentricity [P = .3]). For IDC, concordance with pathology for all modalities was similar (65%-76%). Among discordant cases, underestimation was significantly more common for mammography and US, while MRI more frequently overestimated disease extent. MRI very rarely overestimated multifocal disease in ILC (2%). CONCLUSION: MRI demonstrates an 80% to 90% concordance rate with pathology for ILC, superior to mammography and US. The addition of MRI in IDC patients may decrease underestimation of disease extent and potentially contribute to a reduction in post-operative residual disease.

Intravenous Line Phase-Wrap Artifact at Bilateral Axial 3-T Breast MRI: Identification, Analysis, and Solution.

Purpose: To understand and remove the source of a phase-wrap artifact produced by residual contrast agent in the intravenous line during acquisition of bilateral axial 3-T dynamic contrast material-enhanced (DCE) breast MRI. Materials and Methods: A two-part study involved a phantom experiment, followed by an institutional review board approved clinical intervention, to evaluate the phase-wrap artifact at MRI. A phantom model evaluated artifact production by using an intravenous line filled with fluids with varying concentrations of gadolinium-based contrast agent (0, 0.4, 0.8, 1.2, 1.6, and 2 mmol/mL) and by positioning the simulated intravenous line within several fields of view (FOV) at 3-T MRI in breast coils. Next, a clinical assessment was performed with a total of 400 patients (control group:interventional group, 200:200) to determine the effect of taping the intravenous line to the patients' backs. Breast MR images were assessed blindly for the presence of the artifact. Software was used for statistical analysis with a P value of less than .05 considered a significant difference. Results: In the phantom model, the artifact was produced only with a 0.4 mmol/mL gadolinium concentration and when the tubing was either close to the edge or within a FOV of 350-450 mm. In the clinical experiment, the artifact was more prevalent in the retrospective control group than in the prospective intervention group (52.5% [105 of 200] vs 22% [44 of 200]; P < .005). Conclusion: The presence of phase-wrap artifacts can be reduced by moving the contrast agent intravenous line out of the FOV during acquisition by taping it to a patient's back during bilateral axial 3-T DCE breast MRI.Keywords: Breast, MR-Imaging, Phantom Studies© RSNA, 2020.