The effect of respiratory motion on CSI localized MRS. Cooperative Group on MR Applications to Cancer

A theoretical model to assess the effect of respiratory motion on chemical shift imaging (CSI) data of an extended sample is described. Data from the model are shown to agree with those acquired experimentally from phantoms. In CSI, Fourier bleed and ghost artefacts are of particular significance when the tissue of interest is adjacent to other tissue with much higher concentrations of metabolites, such as chest wall muscle adjacent to breast tumour tissue. We have evaluated contamination due to Fourier bleed and ghosting due to subject motion separately. The results demonstrate that the amount of signal contamination due to motion is relatively independent of the ratio of sample width to voxel width and of the period of motion, but has a strong dependence on the number of phase-encoding steps and the amplitude of the motion.