2D-3D registration of cardiac images using catheter constraints

Abstract Introduction Cardiac catheterization procedures are routinely guided using X-ray fluoroscopy. This modality is suitable due to its high spatial and temporal resolutions, relative low-cost, ubiquitous availability and excellent catheter visibility. However, fluoroscopy has poor softtissue contrast and the cardiologists need to rely on their expertise to accurately position the catheters. Cardiac electrophysiology (EP) procedures are commonly carried out to treat electrical pathologies, such as arrhythmias, usually using radio-frequency (RF) ablation of endocardial tissue. These procedures are often prolonged due to the requirement of accurate positioning of catheters and therefore there is significant radiation exposure to the patient and staff, and often a suboptimal success rate. Recently, there has been much research to register pre-procedural three-dimensional (3D) anatomical information from computerized tomography (CT) or magnetic resonance (MR) imaging to help guide EP procedures by overlaying the 3D anatomical information onto the live two-dimensional (2D) X-ray fluoroscopy [1]. Rhode et al. previously reported a technique that uses a pre-calibrated hybrid X-ray/MR (XMR) imaging system Using the CS catheter for registration is attractive since no additional data acquisition is required and therefore there is no disturbance to the routine clinical workflow. Sra et al. first proposed using the CS catheter for 2D-3D registration We aim to develop a clinically robust method to perform 2D-3D registration of 3D cardiac data (CT or MR) to X-ray fluoroscopy using catheters that are reconstructed in 3D from sequential biplane X-ray images, and structures segmented from 3D data. We focus on the use of the CS and the aortic catheters. Our approach differs from that of Sra et al. because we perform the registration in 3D and then project to the Xray image using a pre-calibration of the X-ray system. Furthermore, the registration only needs to be performed at the beginning of the procedure and is then updated automatically by tracking the motion of the X-ray c-arm and table. Repeat registration is only required if the patient has moved on the X-ray table. We demonstrate the use of the approach on three clinical EP procedures

Determination of peak velocity in stenotic areas: echocardiography versus k-t SENSE accelerated MR Fourier velocity encoding

The study was approved by the local ethical committees, and informed consent from each participant was obtained. The purpose of the study was to compare accelerated magnetic resonance (MR) Fourier velocity encoding (FVE), MR phase-contrast velocity mapping, and echocardiography with respect to peak velocity determination in vascular or valvular stenoses. FVE data collection was accelerated by using the k-space and time sensitivity encoding, or k-t SENSE, technique. Peak velocities were evaluated in five healthy volunteers (one woman, four men; mean age, 28 years; range, 23-34 years), three patients with stenotic aortic valves (two women, one man; mean age, 67 years; range, 39-82 years), two patients with pulmonary valvular stenosis (a 14-year-old girl and a 36-year-old man), and two patients with aortic stenosis (two women aged 18 and 27 years). In volunteers, peak velocity determined by the different methods agreed well. In patients, similar peak velocities were obtained by using accelerated MR FVE and echocardiography, while phase-contrast MR imaging results tended to underestimate these values. RSNA, 200