title: Image-guided transapical aortic valve implantation: sensorless tracking of stenotic valve landmarks in live fluoroscopic images.
abstract: OBJECTIVE
  Aortic valve stenosis is one of the most frequently acquired valvular heart diseases, accounting for almost 70% of valvular cardiac surgery. Transapical transcatheter aortic valve implantation has recently become a suitable minimally invasive technique for high-risk and elderly patients with severe aortic stenosis. In this article, we aim to automatically define a target area of valve implantation, namely, the area between the coronary ostia and the lowest points of two aortic valve cusps. Therefore, we present a new image-based tracking method of these aortic landmarks to assist in the placement of aortic valve prosthesis under live 2D fluoroscopy guidance.
  
  
  METHODS
  We propose a rigid intensity-based image registration technique for tracking valve landmarks in 2D fluoroscopic image sequences, based on a real-time alignment of a contrast image including the initialized manual valve landmarks to each image of sequence. The contrast image is automatically detected to visualize aortic valve features when the aortic root is filled with a contrast agent.
  
  
  RESULTS
  Our registration-based tracking method has been retrospectively applied to 10 fluoroscopic image sequences from routine transapical aortic valve implantation procedures. Most of all tested fluoroscopic images showed a successful tracking of valve landmarks, especially for the images without contrast agent injections.
  
  
  CONCLUSIONS
  A new intraoperative image-based method has been developed for tracking aortic valve landmarks in live 2D fluoroscopic images to assist transapical aortic valve implantations and to increase the overall safety of surgery as well.
authors.affiliation: Department of Cardiothoracic Surgery, School of Medicine, Stanford University, Stanford, CA, USA.
authors.forename: Denis R
authors.initials: DR
authors.lastname: Merk
authors.forename: Mohamed Esmail
authors.initials: ME
authors.lastname: Karar
authors.forename: Claire
authors.initials: C
authors.lastname: Chalopin
authors.forename: David
authors.initials: D
authors.lastname: Holzhey
authors.forename: Volkmar
authors.initials: V
authors.lastname: Falk
authors.forename: Friedrich W
authors.initials: FW
authors.lastname: Mohr
authors.forename: Oliver
authors.initials: O
authors.lastname: Burgert