Breast density assessment using a 3T MRI system: comparison among different sequences

Abstract

Purpose: To compare MRI sequences for breast density measurements on a 3T MRI system using IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least squares estimation) as possible physiology-like reference.

Materials and methods: MRI examination was performed in 48 consecutive patients (mean age 41, years; range, 35-67 years) on a 3.0T scanner and 46 were included. All (fertile) women, were examined between days 5 and 15 of their menstrual cycle. MRI protocol included: T1-turbo spin-echo (T1-tSE), T2-turbo spin-echo (T2-tSE), VIBRANT (Volume Imaging for Breast Assessment) before and after injection of contrast media and IDEAL. Breast density was calculated with semi-automated software. Statistical analysis was performed with non-parametric tests.

Results: Mean percentage of breast density calculated in each sequence was: T1-tSE = 56%; T2-tSE = 52%; IDEAL FatOnly = 55%; IDEAL WaterOnly = 53%, VIBRANT = 55%. Significant differences were observed between T2-tSE and both T1-tSE (p<0.001), VIBRANT sequences (p = 0.009), T1-tSE and both IDEAL WaterOnly (p = 0.007) and IDEAL FatOnly (p = 0.047). Breast density percentage showed a positive linear correlation among different sequences: r ≥ 0.93.

Conclusions: Differences exist between MRI sequences used to assess breast density percentage. T1-weighted sequences values were similar to IDEAL sequences.

Figure 1. Quantitative assessment of breast density using the thresholding method.

In this figure an example of the graphical computer interface is demonstrated. On the left, the edges of the breast are identified (edges are artificially thickened for visual purposes), then the radiologist adjusts the density threshold (semi-automated method) on the right, and finally the percentage of breast density is shown (black circle). In this example, the breast result was 41% dense.