Breast dynamic contrast-enhanced examinations with fat suppression: Are contrast-agent uptake curves affected by magnetic field inhomogeneity?

摘要

Objectives: To investigate the effect of magnetic field heterogeneity in breast dynamic contrast-enhanced examinations with fat saturation (DCE-FS). Methods: The magnetic field was mapped over the breasts in ten patients. DCE-FS was undertaken at 1.5 T with fast spoiled gradient echoes and spectrally selective fat saturation. Signal intensity was calculated for T1 values 25-1,200 ms both on and off resonance, and results were verified with a test object. Clinical examinations were evaluated for the predicted effects of field heterogeneity. Results: Magnetic field was found to vary by 3.6 ± 1.2 ppm over the central transaxial slice and 5.1 ± 1.5 over the whole breast volume (mean ± standard deviation). Computer simulations predict a reduction in the dynamic range if field heterogeneity leads to unintended water suppression, and distortion to CA uptake curves due to fat suppression failure (for fat containing pixels). A compromise between dynamic range and fat saturation performance is required. Both water suppression and fat suppression failure are apparent in clinical examinations. Conclusion: Magnetic field heterogeneity is likely to reduce the sensitivity of DCE-FS by distorting the CA uptake curves because of fat suppression failure (for fat containing pixels) and by reducing the dynamic range because of unintended water suppression. Key Points: ? Magnetic field heterogeneity is significant in breast magnetic resonance. ? Contrast-agent uptake curves are distorted by a non-uniform magnetic field. ? Radiologist must be aware of possibility of distortion to interpret uptake curves correctly. ? Compromise between fat suppression and dynamic range is required.