Ulrich Bill

Electromagnetic tracking system for minimal invasive interventions using a C-arm system with CT option: First clinical results.

To ensure precise needle placement in soft tissue of a patient for e.g. biopsies, the intervention is normally carried out image-guided. Whereas there are several imaging modalities such as computed tomography, magnetic resonance tomography, ultrasound, or C-arm X-ray systems with CT-option, navigation systems for such minimally invasive interventions are still quite rare. However, prototypes and also first commercial products of optical and electromagnetic tracking systems demonstrated excellent clinical results. Such systems provide a reduction of control scans, a reduction of intervention time, and an improved needle positioning accuracy specially for deep and double oblique access. Our novel navigation system CAPPA IRAD EMT with electromagnetic tracking for minimally invasive needle applications is connected to a C-arm imaging system with CT-option. The navigation system was investigated in clinical interventions by different physicians and with different clinical applications. First clinical results demonstrated a high accuracy during needle placement and a reduction of control scans.

Hierarchical guidewire tracking in fluoroscopic sequences

In this paper, we present a novel hierarchical framework of guidewire tracking for image-guided interventions. Our method can automatically and robustly track a guidewire in fluoroscopy sequences during interventional procedures. The method consists of three main components: learning based guidewire segment detection, robust and fast rigid tracking, and nonrigid guidewire tracking. Each component aims to handle guidewire motion at a specific level. The learning based segment detection identifies small segments of a guidewire at the level of individual frames, and provides unique primitive features for subsequent tracking. Based on identified guidewire segments, the rigid tracking method robustly tracks the guidewire across successive frames, assuming that a major motion of guidewire is rigid, mainly caused by the breathing motion and table movement. Finally, a non-rigid tracking algorithm is applied to finely deform the guidewire to provide accurate shape. The presented guidewire tracking method has been evaluated on a test set of 47 sequences with more than 1000 frames. Quantitative evaluation demonstrates that the mean tracking error on the guidewire body is less than 2 pixels. Therefore the presented guidewire tracking method has a great potential for applications in image guided interventions.

Kyphoplasty interventions using a navigation system and C-arm CT data: first clinical results

This study evaluates new applications using a novel navigation system with electromagnetic (EM) tracking in clinical routine. The navigation system (iGuide CAPPA, CAS innovations, Erlangen, Germany) consists of a PC with dedicated navigation software, the AURORA tracking system (NDI, Waterloo Ontario, Canada) and needles equipped with small coils in their tips for EM navigation. After patient positioning a 3D C-arm data set of the spine region of interest is acquired. The images are reconstructed and the 3D data set is directly transferred to the navigation system. Image loading and image to patient registration are performed automatically by the navigation system. For image acquisition a C-arm system with DynaCT option (AXIOM Artis, Siemens Healthcare, Forchheim, Germany) was used. As new clinical applications we performed kyphoplasty for reconstruction of collapsed vertebrae. All interventions were carried out without any complication. After a single planning scan the radiologists were able to place the needle in the designated vertebra. During needle driving 2D imaging was performed just in a few cases for control reasons. The time between planning and final needle positioning was reduced in all cases compared to conventional methods. Moreover, the number of control scans could be markedly reduced. The deviation of the needle to the planned target was less than 2 mm. The use of DynaCT images in combination with electromagnetic tracking-based navigation systems allows a precise needle positioning for kyphoplasty.