Classification of breast lesions pre-contrast injection using water resonance lineshape analysis

Inhomogeneously broadened, non-Lorentzian water resonances have been observed in small image voxels of breast tissue. The non-Lorentzian components of the water resonance are likely produced by bulk magnetic susceptibility shifts caused by dense, deoxygenated tumor blood vessels (the ‘BOLD’ effect), but can also be produced by other characteristics of local anatomy and physiology, including calcifications and interfaces between different types of tissue. Here, we tested the hypothesis that detection of non-Lorentzian components of the water resonance with high spectral and spatial resolution (HiSS) MR imaging allows classification of breast lesions without the need to inject contrast agent. Eighteen malignant lesions and nine benign lesions were imaged with HiSS MRI at 1.5T. A new algorithm was developed to detect non-Lorentzian (or off-peak) components of the water resonance. After a Lorentzian fit was subtracted from the data, the largest peak in the residual spectrum in each voxel was identified as the major off-peak component of the water resonance. The difference in frequency between these off-peak components and the main water peaks, and their amplitudes were measured in malignant lesions, benign lesions, and breast fibroglandular tissue. Off-peak component frequencies were significantly different between malignant and benign lesions (p<0.001). Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of HiSS off-peak component analysis compared to dynamic contrast enhanced (DCE) MRI parameters. The areas under the ROC curves for ‘DCE rapid uptake fraction’, ‘DCE washout fraction’, ‘off-peak component amplitude’, and ‘off-peak component frequency’ were 0.75, 0.83, 0.50, and 0.86, respectively. These results suggest that water resonance lineshape analysis performs well in the classification of breast lesions without contrast injection and could improve diagnostic accuracy of clinical breast MR exams. In addition, this approach may provide an alternative to DCEMRI in women who are at risk for adverse reactions to contrast media