Effect of endothelial injury and increased blood pressure on albumin accumulation in the arterial wall: a numerical study.

The present study investigates the influence of endothelial damage and of blood pressure on albumin accumulation in the arterial wall. For this purpose a numerical model for the coupled mass transport processes in the arterial lumen and in the various layers of the arterial wall is developed. The model considers the transport in the endothelium, intima, internal elastic lamina (IEL) and media of a straight axisymmetric arterial segment. In the arterial lumen fully developed stationary blood flow is assumed, the filtration velocity in the wall layers is calculated applying Darcy's law. The description of the luminal mass transport uses the stationary convection-diffusion equation, the transport in the porous intima and media is modelled applying the volume-averaged stationary convection-diffusion-reaction equation. The transport processes in the lumen, intima and media are coupled by the flux across the endothelium and IEL, which is mathematically described using the Kedem-Katchalsky equations. The numerical solution of the transport equations applies the finite element method. The results demonstrate a high resistance of the healthy endothelium to macromolecule exchange between blood and the artery wall. The reduced resistance of an injured endothelium causes an increased mass flux into the wall which results in higher concentration levels within the wall. The effect of the blood pressure on the wall concentration level is different for a helathy and an injured endothelium. In the case of a healthy endothelium a blood pressure increase causes a decrease of the intimal concentration and an increase of the medial concentration, whereas in the case of an injured endothelium an increased blood pressure results in higher concentration levels within the intima and media.

Blood flow in distal end-to-side anastomoses with PTFE and a venous patch: results of an in vitro flow visualisation study.

OBJECTIVES: non-physiological flow behaviour plays a significant role in the development of distal anastomotic intimal hyperplasia. To investigate flow patterns in four anastomotic types of femoral end-to-side distal bypass graft anastomoses, a flow visualisation study was performed. METHODS: transparent 1:1 casted replicas of distal vascular graft anastomoses created by conventional technique, Miller-cuff, Taylor- and Linton-patch were fabricated. A pulsatile mock circulation with a high-speed video system was constructed. Flow pattern was determined at mean Reynolds numbers 100-500. Migrations of the stagnation points on the bottom of the anastomoses at mean Reynolds numbers 100, 230, and 350 were measured. RESULTS: a vortex forms during early systole and increases to maximum systole in all anastomoses. During the diastolic phase the vortex moves in the Miller-cuff distally to the toe of the anastomosis and remains standing, while in the other anastomotic types the vortex moves proximally to the heal of the junction and breaks down. The shift of the stagnation point in the Miller-cuff was considerably smaller than in the other anastomoses. CONCLUSION: conventional, Linton and Taylor anastomoses show similar flow patterns. The Miller-cuff with its wider cavity shows lower shift of the bottom stagnation point, but a persistent washout of the anastomotic cavity, which may contribute to its reported good clinical performance.

Results and experience with four years of development work on a filmless department in Mjölby health care centre.

Since the end of 1994, the radiology department in Mjölby has been running their activity without X-ray films. When the film developing machine at the department was discarded in April 1995, after six months of test-running of the new system, the film epoch was definitely abandoned. The practical experiences from working with digital images are all good. The background to this change lays in a four years development work, which has been supported financially by the Ostergötland County Council, Swedish National Board for Industrial and Technical Development (NUTEK), and a regional foundation for development of new ways to organise and perform work (Arbetslivsfonden).

Spatial resolution requirements in digital radiography of scaphoid fractures. An ROC analysis.

PURPOSE: To investigate the spatial resolution requirements in digital radiography of scaphoid fractures. MATERIAL AND METHODS: Included in the study were 60 scaphoid radiographs with and 60 without fractures of the scaphoid bone. The film-screen images were digitized using pixel sizes of 115, 170, and 340 microns along with 170 microns with a 10:1 wavelet compression. The digital images were displayed on a 1280 x 1024 x 8 bits monitor, and 5 observers evaluated the images in 5 randomized sessions. The results for each pixel size were then compared to the film-screen images by ROC analysis. RESULTS: The mean area under the ROC curves was larger for the film-screen images than for the digital images at all resolutions. However, this difference was not significant when the areas under the ROC curves for the film-screen images were compared to the digital images of 115, 170, and 170 microns with 10:1 compression. There was a significant difference for the 340-microns pixel size in favour of the film-screen images. The mean ROC curves for the digital images were very similar for the 115 and 170 microns pixel sizes, although slightly better for 115 microns. At 170 microns, the compression seemed to have a relatively small negative effect on the diagnostic performance; the deterioration was greater when the pixel size was increased to 340 microns. There was no obvious correlation between diagnostic performance and the experience of the observers in using work-stations. CONCLUSIONS: The pixel size of 170 microns is adequate for the detection of subtle fractures, even after wavelet compression by a ratio of 10:1.

PACS-RIS interconnection: results of a feasibility study.

In a study on behalf of the Swedish National Board of Development we have attempted to figure out what a complete information system for the small and medium sized radiology department should contain. Some of the results will be presented in this article. One of the main questions was whether a natural interface between what usually is referred to as PACS (picture archiving and communications system) and RIS (radiology information system) exists. Our answer to that question is, simply, no. We mean that an information system that handles all information on the radiology department has to be designed as one system and not be divided into a PACS and an RIS.

Digital subtraction angiography versus standard contrast arteriography in evaluation of peripheral vascular disease.

Fifteen patients with lower limb ischemic disease were preoperatively assessed with both intravenous or intra-arterial digital subtraction angiography (DSA), and standard contrast angiography (SCA). The images were reviewed and the operative strategies, based on the clinical data and each of SCA and DSA, were compared. SCA provided more information than DSA in two patients, one of which had an incomplete DSA investigation. DSA provided more information than SCA in three patients. The distal crural vessels were better visualized with DSA in one patient, and popliteal lesions were demonstrated as being more severe using DSA than with SCA in two patients. The level of the distal anastomosis of the proposed bypass was lowered to below the knee as a result of DSA in these two patients. We conclude that comparable information is obtained using SCA or DSA, and that DSA, in particular the intraarterial technique, is a satisfactory alternative to SCA in preoperative evaluation of patients with lower limb ischemic disease.