title: Registration and tracking to integrate X-ray and MR images in an XMR facility.
abstract: We describe a registration and tracking technique to integrate cardiac X-ray images and cardiac magnetic resonance (MR) images acquired from a combined X-ray and MR interventional suite (XMR). Optical tracking is used to determine the transformation matrices relating MR image coordinates and X-ray image coordinates. Calibration of X-ray projection geometry and tracking of the X-ray C-arm and table enable three-dimensional (3-D) reconstruction of vessel centerlines and catheters from bi-plane X-ray views. We can, therefore, combine single X-ray projection images with registered projection MR images from a volume acquisition, and we can also display 3-D reconstructions of catheters within a 3-D or multi-slice MR volume. Registration errors were assessed using phantom experiments. Errors in the combined projection images (two-dimensional target registration error--TRE) were found to be 2.4 to 4.2 mm, and the errors in the integrated volume representation (3-D TRE) were found to be 4.6 to 5.1 mm. These errors are clinically acceptable for alignment of images of the great vessels and the chambers of the heart. Results are shown for two patients. The first involves overlay of a catheter used for invasive pressure measurements on an MR volume that provides anatomical context. The second involves overlay of invasive electrode catheters (including a basket catheter) on a tagged MR volume in order to relate electrophysiology to myocardial motion in a patient with an arrhythmia. Visual assessment of these results suggests the errors were of a similar magnitude to those obtained in the phantom measurements.
authors: Division of Imaging Sciences, Guy's, King's & St Thomas' School of Medicine, King's College London, Guy's Hospital, London SE1 9RT, UK.
authors: Kawal S
authors: KS
authors: Rhode
authors: Derek L G
authors: DL
authors: Hill
authors: Philip J
authors: PJ
authors: Edwards
authors: John
authors: J
authors: Hipwell
authors: Daniel
authors: D
authors: Rueckert
authors: Gerardo
authors: G
authors: Sanchez-Ortiz
authors: Sanjeet
authors: S
authors: Hegde
authors: Vithuran
authors: V
authors: Rahunathan
authors: Reza
authors: R
authors: Razavi
mesh_terms: D000293:Adolescent; D000465:Algorithms; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000000981:diagnostic imaging; D002138:Calibration; D013504:Cardiovascular Surgical Procedures / Q000379:methods; D019544:Equipment Failure Analysis; D006321:Heart / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D011859:Radiography / Q000295:instrumentation / Q000379:methods; D011872:Radiology Department, Hospital / Q000458:organization & administration; D013382:Subtraction Technique / Q000295:instrumentation*; D025321:Surgery, Computer-Assisted / Q000379:methods; D018511:Systems Integration