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Three‐dimensional tracking of cardiac catheters using an inverse geometry x‐ray fluoroscopy system
Author(s) -
Speidel Michael A.,
Tomkowiak Michael T.,
Raval Amish N.,
Van Lysel Michael S.
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3515463
Subject(s) - isocenter , imaging phantom , fluoroscopy , tomosynthesis , tracking (education) , physics , nuclear medicine , computer vision , geometry , computer science , mathematics , optics , medicine , mammography , psychology , pedagogy , cancer , breast cancer , nuclear physics
Purpose: Scanning beam digital x‐ray (SBDX) is an inverse geometry fluoroscopic system with high dose efficiency and the ability to perform continuous real‐time tomosynthesis at multiple planes. This study describes a tomosynthesis‐based method for 3D tracking of high‐contrast objects and present the first experimental investigation of cardiac catheter tracking using a prototype SBDX system. Methods: The 3D tracking algorithm utilizes the stack of regularly spaced tomosynthetic planes that are generated by SBDX after each frame period (15 frames/s). Gradient‐filtered versions of the image planes are generated, the filtered images are segmented into object regions, and then a 3D coordinate is calculated for each object region. Two phantom studies of tracking performance were conducted. In the first study, an ablation catheter in a chest phantom was imaged as it was pulled along a 3D trajectory defined by a catheter sheath (10, 25, and 50 mm/s pullback speeds). SBDX tip tracking coordinates were compared to the 3D trajectory of the sheath as determined from a CT scan of the phantom after the registration of the SBDX and CT coordinate systems. In the second study, frame‐to‐frame tracking precision was measured for six different catheter configurations as a function of image noise level ( 662 – 7625 photons / mm 2mean detected x‐ray fluence at isocenter). Results: During catheter pullbacks, the 3D distance between the tracked catheter tip and the sheath centerline was 1.0 ± 0.8 mm (mean ± one standard deviation). The electrode to centerline distances were comparable to the diameter of the catheter tip (2.3 mm), the confining sheath (4 mm outside diameter), and the estimated SBDX‐to‐CT registration error( ± 0.7 mm ) . The tip position was localized for all 332 image frames analyzed and 83% of tracked positions were inside the 3D sheath volume derived from CT. The pullback speeds derived from the catheter trajectories were within 5% of the programed pullback speeds. The tracking precision of ablation and diagnostic catheter tips ranged from ± 0.2 mm at the highest image fluence to ± 0.9 mm at the lowest fluence. Tracking precision depended on image fluence, the size of the tracked catheter electrode, and the contrast of the electrode. Conclusions: High speed multiplanar tomosynthesis with an inverse geometry x‐ray fluoroscopy system enables 3D tracking of multiple high‐contrast objects at the rate of fluoroscopic imaging. The SBDX system is capable of tracking electrodes in standard cardiac catheters with approximately 1 mm accuracy and precision.