A pulse sequence with magnetization transfer contrast and fat suppression was used in three-dimensional magnetic resonance imaging of the breast. Two healthy volunteers, one person with silicone implants, and 12 patients with clinical and/or mammographic findings suspicious for malignancy were evaluated prior to and following infusion of gadopentetate dimeglumine. Imaging time was approximately 7 minutes for each set of data (128 sections). Final voxel dimensions ranged from 1.4 x 0.8 x 0.8 mm to 1.6 x 0.9 x 0.9 mm. All carcinomas, including ductal and lobular types, were enhanced before and after infusion of contrast medium. Multifocal carcinoma and inflammatory carcinoma could be clearly visualized. Enhancement was not evident in patients with fat necrosis (n = 1) or scar (n = 1). Fibrocystic changes in one patient were visible as areas of increased signal intensity on preinfusion images. Resolution and contrast of MR images obtained with this pulse sequence appeared to be improved over that achieved with conventional breast MR imaging techniques. This method has the potential to supplement conventional diagnostic methods in the evaluation of breast disease.
We demonstrate that magnetization transfer contrast can be used to improve the diagnostic utility of fat-suppressed steady-state three-dimensional gradient-recalled images. Fat suppression is achieved using a "jump-return" pair of contiguous shaped pulses. No time interval exists between the pulses, and no RF echo is generated. The sequence normally produces images with "density" weighting. Preparation of the spin magnetization with off-resonance frequency-selective excitation creates magnetization transfer contrast which attenuates signal intensity in proportion to the exchange rate of magnetization from free water with magnetization from water bound to macromolecules or protons that have restricted mobility. The resulting images have excellent fat suppression with low sensitivity to motion since no subtraction is used. In addition, the mechanism of signal attenuation is independent of paramagnetic effects, and addition of Gd-DTPA produces signal enhancement from vascularized regions of tissue. Examples are presented for the knee and breast, where the observation of pathology with signal enhancement from Gd-DTPA is improved over conventional 3D fat-suppressed images.
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