Mutual information based respiration detection

Percutaneous Transluminal Coronary Angioplasty (PTCA) is currently the preferred method for the treatment of coronary artery disease in vivo. During the intervention, images of the coronary arteries filled with a radiopaque contrast agent are acquired (angiography) in order to localize the lesion. One of these images is then displayed on a monitor. It serves as a roadmap that is afterwards utilised to navigate the interventional instruments to the lesion under constant low-dose X-ray surveillance (fluoroscopy). The fluoroscopic live images are displayed in real-time on a second monitor next to the roadmap monitor. It is desirable to provide for each fluoroscopic image an angiographic roadmap that exhibits a similar position and shape of the coronary vessels. To accomplish this goal, the respiration status in every (pre-recorded) angiographic and (live) fluoroscopic image has to be quantified in order to display angiographic roadmaps matching to the live fluoroscopic image. We present a method that estimates the respiration status of a patient from grey-level X-ray fluoroscopic images based on their similarity to a reference frame applying a mutual information (MI) similarity measure. (C) 2003 Elsevier Science B.V. and CARS. All rights reserved.