C-arm fluoroscopy is used for guidance during several clinical exams, e.g. in bronchoscopy to locate the bronchoscope inside the airways. Unfortunately, these images provide only 2D information. However, if the C-arm pose is known, it can be used to overlay the intrainterventional fluoroscopy images with 3D visualizations of airways, acquired from preinterventional CT images. Thus, the physician's view is enhanced and localization of the instrument at the correct position inside the bronchial tree is facilitated. We present a novel method for C-arm pose estimation introducing a marker-based pattern, which is placed on the patient table. The steel markers form a pattern, allowing to deduce the C-arm pose by use of the projective invariant cross-ratio. Simulations show that the C-arm pose estimation is reliable and accurate for translations inside an imaging area of 30 cm x 50 cm and rotations up to 30°. Mean error values are 0:33 mm in 3D space and 0:48 px in the 2D imag ing plane. First tests on C-arm images resulted in similarly compelling accuracy values and high reliability in an imaging area of 30 cm x 42:5 cm. Even in the presence of interfering structures, tested both with anatomy phantoms and a turkey cadaver, high success rates over 90% and fully satisfying execution times below 4 sec for 1024 px x 1024 px images could be achieved
Bronchoscopic biopsies for diagnosis of lung cancer are usually done with the help of intraoperative fluoroscopy. But fluoroscopy images lack 3D information and do not provide a clear view of the bronchi or lesions. Our goal is to enhance the physician's view by overlaying the intraoperative fluoroscopy images with both 2D and 3D airway visualizations from preoperatively taken CT scans. The presented system provides automatic airway segmentation and skeletonization as well as automatic 2D/3D alignment of fluoroscopy to CT. The results are used for correctly overlaying the airways and visualizing bronchoscopic paths. The only additional equipment needed is a specifically designed pattern of steel spheres and sticks on acrylic glass, which is fixed on the patient table. It is used for estimating the C-arm pose during image acquisition and allows 2D/3D image alignment in clinically feasible time (<6 s) and accuracy (mTRE<0.33mm on simulated data). No interference with the physician's standard bronchoscopy procedure is introduced and no additional radiation exposure is required. On the contrary, by improving the physician's view and orientation inside the bronchial tree, a faster and more target-oriented guidance to the site of interest is possible
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