3T MR imaging: diffusion-weighted and dynamic contrast-enhanced - relationship of apparent diffusion coefficient value and maximum percentage enhancement in invasive lobular carcinoma of the breast

Introduction

In breast MR imaging, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) studies are being increasingly utilised in assessing malignancy. We investigated potential relationships between these two techniques in cases of proven invasive lobular carcinoma (ILC).

Methods

Thirty-two consecutive cases of ILC underwent 3T breast MR imaging as part of routine staging - retrospective analysis was undertaken. Diffusion-weighted imaging using three b values (0, 500 and 1,000 seconds/mm²) was performed prior to dynamic contrast-enhanced imaging in each case. Post processing included obtaining maximum intensity projections and multiplanar reconstruction. Regions of interest (ROI) were placed over the index (presenting) lesion. In cases of multifocality/multicentricity, the most conspicuous enhancing lesion was interrogated. Enhancement kinetics were evaluated from the dynamic contrast-enhanced images: the percentage of signal intensity increase within the first 2 minutes after administrating contrast agent relative to pre-contrast signal intensity was calculated and the morphology of the curve for 6 minutes after contrast administration was analysed. The same size of ROI was placed over the lesion site on the DWI and the apparent diffusion coefficient (ADC) map was calculated.

Results

Age range, 34 to 74 years; index lesion size, 4 to 78 mm. For type 2 and type 3 curves, signal increase was 128 to 306%; ADC mean 1.29 × 10^-3 mm²/second. In type 1 curves, signal increase was 82 to 93%; ADC mean 0.85 × 10^-3 mm²/second. In four cases (with type 1 or type 2 curves) no lesions with restricted diffusion were apparent.

Conclusion

The percentage signal intensity increase on DCE is higher in cases with measurable ADC values than without. ILC with type 1 or type 2 curves may not be visible on DWI.