"This thesis presents an ultrasound technique for measuring the absolute integrated backscatter (IBS) of arterial wall structures through an intervening inhomogeneous soft tissue layer. The aberrating effect of this tissue layer is minimized by normalizing the measured IBS from the wall region of interest with the IBS from an adjacent range cell in blood. The technique may become a tool to differentiate between stable and vulnerable plaques in the carotid artery."

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Thesis (doctoral)--Universitetet i Lund.

The incidence of lumbar spinal stenosis (LSS) is steadily rising, mostly because of a noticeably older age structure. In Sweden, LSS surgery has increased continuously over the years and is presently the most common argument to undergo spine surgery. The purpose of the surgery is to decompress the neural elements in the stenotic spinal canal. To avoid instability, there has been a tradition to do the decompression with a complementary fusion, especially if degenerative spondylolisthesis is present preoperatively. The overall aims of this thesis were to evaluate which method of surgery that generally can be considered to give sufficiently good clinical results with least cost to society and risk of complications and to determine whether there is a difference in outcome between smokers and non-smokers. The Swespine Register was used to collect data on clinical outcome after LSS surgery. In two of the studies, large cohorts were observed prospectively with follow-up after 2 years. Data were analysed in a multivariate model and logistic regression. In a randomised controlled trial (RCT, the Swedish Spinal Stenosis Study), 233 patients were randomised to either decompression with fusion or decompression alone and then followed for 2 years. The consequence of preoperative degenerative spondylolisthesis on the results was analysed and a health economic evaluation performed. The three-dimensional CT technique was used in a radiologic biomechanical pilot study to evaluate the stabilising role of the segmental midline structures in LSS with preoperative degenerative spondylolisthesis by comparing laminectomy with bilateral laminotomies. Smokers, in comparison with non-smokers, showed less improvement after surgery for LSS. Decompression with fusion did not lead to better results compared with decompression alone, no matter if degenerative spondylolisthesis was present preoperatively or not; nor was decompression with fusion found to be more cost-effective than decomression alone. The instability caused by a decompression proved to be minimal and removal of the midline structures by laminectomy did not result in increased instability compared with the preservation of these structures by bilateral laminotomies. In LSS surgery, decompression without fusion should generally be the treatment of choice, regardless of whether preoperative degenerative spondylolisthesis is present or not. Special efforts should be targeted towards smoking cessation prior to surgery.

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In this research, pulsatile blood flow through a modeled arterial stenosis assuming Newtonian and non-Newtonian viscous behavior is simulated using direct numerical simulation (DNS). A serial FORTRAN code has been parallelized using OpenMP to perform DNS based on available high performance shared memory parallel computing facilities. Numerical simulations have been conducted in the context of a channel with varying the degree of stenosis ranging from 50% to 75%. For the pulsatile flow studied, the Womersley number is set to 10.5 and Reynolds number varies from 500 to 2000, which are characteristic of human arterial blood flows. In the region upstream of the stenosis, the flow pattern is primarily laminar. Immediately after the stenosis, the flow recirculates and an adverse streamwise pressure gradient exists near the walls and the flow becomes turbulent. In the region far downstream of the stenosis, the flow is re-laminarized for both Newtonian and non-Newtonian flows.

Afhandling--Copenhagen. / Summary also in Danish. Bibliography: p. 253-258.