ULTRASOUND QUANTITATION OF RESPIRATORY ORGAN MOTION IN THE UPPER ABDOMEN

Organ motion can cause artefacts in abdominal imaging particularly wit h magnetic resonance imaging (MRI), and may often limit the diagnostic quality of an image. If spatial resolution and image quality are to i mprove in MRI and other imaging techniques, a more detailed understand ing of organ motion is required. Despite the importance of organ motio n little quantitative information is available to date. This study was the continuation of work instigated to investigate and quantify respi ratory movements of upper abdominal organs for a group of healthy volu nteers in order to provide the design criteria for a motion test objec t for use in MRI, A previous phase of the project allowed construction of a test object but refinements were needed to represent respiratory motion more closely as a consequence of the data presented in this pa per. Improvements in the scanning technique and the recording procedur e have revealed that, contrary to our initial findings, motion of the diaphragm and liver is predominantly in the superior-inferior (SI) dir ection with an average displacement (+/-SD) (quiet respiration) of 12 +/- 7 mm (range 7-28 mm) and 10 +/- 8 mm (range 5-17 mm), respectively . For some volunteers, motion of the kidneys can be complex, especiall y during deep inspiration, New data have been provided by this phase o f the motion study on the displacement, velocity and acceleration of a bdominal organs as a function of time, These data show that MRI motion artefact reduction techniques which assume that either organ displace ment, velocity or acceleration are constant are only applicable during certain phases of the respiratory cycle.