University of Erlangen-Nuremberg

About: University of Erlangen-Nuremberg is a education organization based out in Erlangen, Bayern, Germany. It is known for research contribution in the topics: Population & Immune system. The organization has 42405 authors who have published 85600 publications receiving 2663922 citations.

Generalized multi-dimensional adaptive filtering for conventional and spiral single-slice, multi-slice, and cone-beam CT.

Abstract: In modern computed tomography (CT) there is a strong desire to reduce patient dose and/or to improve image quality by increasing spatial resolution and decreasing image noise. These are conflicting demands since increasing resolution at a constant noise level or decreasing noise at a constant resolution level implies a higher demand on x-ray power and an increase of patient dose. X-ray tube power is limited due to technical reasons. We therefore developed a generalized multi-dimensional adaptive filtering approach that applies nonlinear filters in up to three dimensions in the raw data domain. This new method differs from approaches in the literature since our nonlinear filters are applied not only in the detector row direction but also in the view and in the z-direction. This true three-dimensional filtering improves the quantum statistics of a measured projection value proportional to the third power of the filter size. Resolution tradeoffs are shared among these three dimensions and thus are considerably smaller as compared to one-dimensional smoothing approaches. Patient data of spiral and sequential single- and multi-slice CT scans as well as simulated spiral cone-beam data were processed to evaluate these new approaches. Image quality was assessed by evaluation of difference images, by measuring the image noise and the noise reduction, and by calculating the image resolution using point spread functions. The use of generalized adaptive filters helps to reduce image noise or, alternatively, patient dose. Image noise structures, typically along the direction of the highest attenuation, are effectively reduced. Noise reduction values of typically 30%-60% can be achieved in noncylindrical body regions like the shoulder. The loss in image resolution remains below 5% for all cases. In addition, the new method has a great potential to reduce metal artifacts, e.g., in the hip region.

Media Calcification and Intima Calcification Are Distinct Entities in Chronic Kidney Disease

Abstract: Calcification of the vascular tree is common in physiologic and pathologic conditions, i.e., aging, diabetes, dyslipidemia, genetic diseases, and diseases with disturbances of calcium metabolism. In chronic kidney disease, vascular calcification is even more common, develops early, and contributes to the markedly increased cardiovascular risk in this particular population. Pathomorphologically, atherosclerosis (i.e., plaque-forming degenerative changes of the aorta and of large elastic arteries) and arteriosclerosis (i.e., concentric media thickening of muscular arteries) can be distinguished. Increasing knowledge about calcification together with improved imaging techniques provided evidence that also vascular calcification has to be divided into two distinct entities according to the specific sites of calcification within the vascular wall: Patchy calcification of the intima in the vicinity of lipid or cholesterol deposits as present in plaque calcification and calcification of the media in the absence of such lipid or cholesterol deposits, known as Monckeberg-type atherosclerosis. The two types of calcification may vary according to the type of vessel (large elastic versus smaller muscular type artery) and proximal versus distal sites of the arterial tree. Furthermore, clinical studies showed that it is not purely academic to distinguish between intimal and medial calcification but rather relevant for the clinical presentation, treatment, and prognosis because each type leads to different clinical consequences. In vivo studies in animal models provided evidence in favor of common pathomechanisms between vascular calcification and atherosclerosis; however, there is other, strong experimental and clinical evidence that pleads for the continued distinction between intimal and medial calcification.