Stochastic approach to error estimation for image-guided robotic systems.

Image-guided surgical systems and surgical robots are primarily developed to provide patient safety through increased precision and minimal invasiveness. Even more, robotic devices should allow for refined treatments that are not possible by other means. It is crucial to determine the accuracy of a system, to define the expected overall task execution error. A major step toward this aim is to quantitatively analyze the effect of registration and tracking-series of multiplication of erroneous homogeneous transformations. First, the currently used models and algorithms are introduced along with their limitations, and a new, probability distribution based method is described. The new approach has several advantages, as it was demonstrated in our simulations. Primarily, it determines the full 6 degree of freedom accuracy of the point of interest, allowing for the more accurate use of advanced application-oriented concepts, such as Virtual Fixtures. On the other hand, it becomes feasible to consider different surgical scenarios with varying weighting factors.

Histological evaluation of preoperative biopsies from ampulla vateri.

Frequency of the lesions of the papilla Vateri is increasing in Hungary because of epidemiological reasons. Over two years nearly 300 ampullary endoscopic biopsies were taken in our hospital. In 36 percent of the patients the papillary specimens demonstrated acute or chronic inflammation, in 44 percent adenoma, including 5 percent with severe dysplasia, in 5 percent adenomatous hyperplasia and in 7 percent adenomyosis or other benign tumors (2%) were found. Around 7 percent of the ampullary samples proved to be malignant, but only in 2.6 percent were the malignancy of intraampullary origin. Nearly 25 percent of biopsies were repeated once and 10 percent twice or more. Concordance of endoscopic and pathologic diagnoses was 69 percent on average but it increased to 83 percent after including repeated biopsies. In the adenoma-carcinoma group the concordance was 90 percent. The sensitivity of the pathological diagnosis with forceps biopsy was only 77 percent, but it became at least 86 percent following papillectomy. In order to improve diagnostic reliability more extensive use of papillectomy is proposed with close cooperation between the endoscopist and pathologist.