Early detection and characterization of colorectal cancer and metastatic disease to the liver affects treatment and therefore the long term survival of patients with that disease. However, previous work in abdominal and pelvic cancer imaging with Magnetic Resonance Imaging (MRI) has not fully used its potential to characterize and size liver lesions. Specifically diffusion-weighted 3D imaging of abdominal cancer in a single breathhold are not performed clinically due to the technical demands of high data rates and image distortions due to off-resonance effects. The goal of this work is to use the current knowledge of Echo Planar Imaging (EPI) to develop these advanced single breathhold abdominal cancer imaging techniques. There are three parts to this proposal: (l) Development of a method of image correction for off-resonance distortions in EPI. These distortions are generated by inadequate magnetic field homogeneity, extra """"""""Maxwell"""""""" gradients during readout, and eddy currents. A field map will be generated by separation of the data in an echo planar readout into even and odd echoes and taking the phase difference between these two images. Off-resonance distortions will be corrected by shifting the signal in each pixel by the amount determined by the phase in that pixel. This correction distortions will allow more accurate imaging with EPI as is necessary for the second and third parts of this proposal. (2) Development of single-breathhold diffusion-weighted imaging of the abdomen. This work will include correction for image distortions as in (l) and correction for motion using navigator echoes. (3) Development of single-breathhold volumetric imaging: this work will enable quantitative lesion sizing.
