Dealing with Respiratory Motion

Abstract

MR images acquired using conventional spin echo or gradient echo methods over several minutes are degraded by respiratory motion artefacts. The effects of respiratory motion can be limited by respiratory compensation or respiratory gating. Respiratory gating only accepts image data that is acquired at one phase of the respiratory cycle (usually end expiration). The respiratory position is monitored either by a pneumatic bellows device, or by the acquisition of navigator echoes. The navigator echo is produced during each cardiac cycle immediately prior to data acquisition. An RF pulse scheme excites a column of tissue that cuts through the patient’s diaphragm, producing an echo which can be used to produce a trace showing the diaphragm position. This allows more accurate monitoring of the diaphragm, position for high resolution applications such as coronary artery imaging.