The Effect of Respiration on the Contrast and Sharpness of Liver Lesions in MRI

This work demonstrates the effects of through-plane motion due to respiration on contrast and sharpness of liver lesions in MRI. The effects of slice coverage with and without such respiratory motion is also reported. This work is comprised of two parts: a theoretical prediction of liver-lesion contrast and blur with and without respiration and an experimental validation using gel phantoms of the predicted results. Both theory and experiment show a loss of contrast, increasing with amplitude of the peak-to-peak motion. The loss of contrast for a 5-mm lesion at normal respiration of 15 mm peak-to-peak superior-inferior motion is approximately 10% with a low order sorted respiratory ordered phase encoding acquisition and approximately 50% for an unsorted acquisition. Lesion blur is greatest for the low order sorted acquisition while the unsorted and high sort acquisitions maintain edge definition. Breath-hold imaging is potentially superior to nonbreath-hold imaging in liver lesion contrast and edge definition, but is more sensitive to inadequate slice coverage.