Handling a High Relaxivity Contrast Material for Dynamic Breast MR Imaging Using Higher Thresholds for the Initial Enhancement

Abstract

To increase specificity of gadobenate dimeglumine-enhanced breast magnetic resonance (MR) imaging without losing sensitivity. IRB approval was obtained for this retrospective study and informed consent was waived. Sixty-eight patients with 73 breast lesions underwent dynamic breast 1.5-T MR imaging with 0.1 mmol/kg of gadobenate dimeglumine and 103 or 111-second temporal resolution. A score system based on shape (round/oval/lobular = 0, linear/dendritic/stellate = 1), margins (defined = 0, undefined = 1), pattern (homogeneous = 0, inhomogeneous = 1, rim = 2), kinetics (continuous = 0, plateau = 1, washout = 2), and initial enhancement was used. Initial enhancement was evaluated with standard (<50% = 0, 50%-100% = 1, >100% = 2) or adjusted (<180% = 0, 180%-240% = 1, >240% = 2) thresholds. Scores 0-2, 3, 4 or 5, and from 6 to 8 were considered as equivalent to Breast Imaging Reporting and Data System 2, 3, 4, and 5, respectively. Pathologic examination (core-, vacuum-assisted, or surgical biopsy) served as a reference standard. Nonparametric tests were used. At histopathology, 52 lesions were malignant, 21 were benign. The initial enhancement for benign lesions was 141% +/- 65% (mean +/- SD), whereas for malignant lesions it was 210% +/- 80% (P = 0.001). The median multifactorial score for benign lesions was 4 using the standard thresholds and 3 using the adjusted thresholds (P < 0.001) whereas for malignant lesions it was 7 and 6, respectively (P < 0.001). Specificity increased from 38% with standard thresholds to 71% with adjusted thresholds (gain of 33%; P = 0.016); positive predictive value 80% and 90%, negative predictive value 100% and 100%, and accuracy 82% and 92%, respectively. Sensitivity was 100% for both thresholds. Specificity of gadobenate dimeglumine-enhanced breast MR imaging can be increased without limiting its high sensitivity.