Application of MFBD Algorithms to Image Reconstruction Under Anisoplanatic Conditions

All optical systems that operate in or through the atmosphere suffer from turbulence induced image blur. Both military and civilian surveillance, gun-sighting, and target identification systems are interested in terrestrial imaging over very long horizontal paths, but atmospheric turbulence can blur the resulting images beyond usefulness. My dissertation explores the performance of a multi-frame-blind-deconvolution technique applied under anisoplanatic conditions for both Gaussian and Poisson noise model assumptions. The technique is evaluated for use in reconstructing images of scenes corrupted by turbulence in long horizontal-path imaging scenarios and compared to other speckle imaging techniques. Performance is evaluated via the reconstruction of a common object from three sets of simulated turbulence degraded imagery representing low, moderate and severe turbulence conditions. Each set consisted of 1000 simulated, turbulence degraded images. The MSE performance of the estimator is evaluated as a function of the number of images, and the number of Zernike polynomial terms used to characterize the point spread function. I will compare the mean-square-error (MSE) performance of speckle imaging methods and a maximum-likelihood, multi-frame blind deconvolution (MFBD) method applied to long-path horizontal imaging scenarios. Both methods are used to reconstruct a scene from simulated imagery featuring anisoplanatic turbulence induced aberrations. This comparison is performed over three sets of 1000 simulated images each for low, moderate and severe turbulence-induced image degradation. The comparison shows that speckle-imaging techniques reduce the MSE 46 percent, 42 percent and 47 percent on average for low, moderate, and severe cases, respectively using 15 input frames under daytime conditions and moderate frame rates. Similarly, the MFBD method provides, 40 percent, 29 percent, and 36 percent improvements in MSE on average under the same conditions. The comparison is repeated under low light conditions (less than 100 photons per pixel) where improvements of 39 percent, 29 percent and 27 percent are available using speckle imaging methods and 25 input frames and 38 percent, 34 percent and 33 percent respectively for the MFBD method and 150 input frames. The MFBD estimator is applied to three sets of field data and the results presented. Finally, a combined Bispectrum-MFBD Hybrid estimator is proposed and investigated. This technique consistently provides a lower MSE and smaller variance in the estimate under all three simulated turbulence conditions.

A COMPARATIVE STUDY OF HEURISTIC OPTIMIZATION ALGORITHMS

Heuristic optimization algorithms are of great importance for reaching solutions to various real world problems. These algorithms have a wide range of applications such as cost reduction, artificial intelligence, and medicine. By the term cost, one could imply that that cost is associated with, for instance, the value of a function of several independent variables. Often, when dealing with engineering problems, we want to minimize the value of a function in order to achieve an optimum, or to maximize another parameter which increases with a decrease in the cost (the value of this function). The heuristic cost reduction algorithms work by finding the optimum values of the independent variables for which the value of the function (the “cost”) is the minimum. There is an abundance of heuristic cost reduction algorithms to choose from. We will start with a discussion of various optimization algorithms such as Memetic algorithms, force-directed placement, and evolution-based algorithms. Following this initial discussion, we will take up the working of three algorithms and implement the same in MATLAB. The focus of this report is to provide detailed information on the working of three different heuristic optimization algorithms, and conclude with a comparative study on the performance of these algorithms when implemented in MATLAB. In this report, the three algorithms we will take in to consideration will be the non-adaptive simulated annealing algorithm, the adaptive simulated annealing algorithm, and random restart hill climbing algorithm. The algorithms are heuristic in nature, that is, the solution these achieve may not be the best of all the solutions but provide a means to reach a quick solution that may be a reasonably good solution without taking an indefinite time to implement.

Osteosynthesis and hemiarthroplasty of fractures of the proximal humerus: outcomes in a consecutive case series

HYPOTHESIS: This study addresses the outcome after osteosynthesis or hemiarthroplasty, using a cohort of patients that was enrolled in a previous prospective study on humeral head perfusion and was consequently treated using a common conceptual approach. MATERIALS AND METHODS: Between 1998 and 2001, 98 patients with 100 fractures of the proximal humerus were treated surgically by a single surgeon with open reduction and internal fixation (ORIF) (51/100, group A, median age 54 years; range, 21-88) or with hemiarthroplasty (49/100, group B, median age 66 years; range, 38-87). Seventy-six of 98 patients were available for re-evaluation at a mean follow-up of five years (3.3-7.3) using the Constant-Murley score (CMS), the Subjective Shoulder Value (SSV), and conventional radiographs. RESULTS: The median total CMS was 77 (range, 37-98) for group A and 70 (range, 39-84) for group B. The median SSV was 92 (range, 40-100) for group A and 90 (range, 40-100) for group B. Avascular necrosis occured in 6/40 fractures treated with ORIF. CONCLUSION: Osteosynthesis and hemiarthroplasty yield similar functional results and comparable patient satisfaction following the applied decision making process in this selected patient cohort. Osteosynthesis with preservation of the humeral head is worth considering when adequate reduction and stable conditions for revascularization can be obtained. In patients with osteopenic bone and/or comminuted fractures, hemiarthroplasty is a viable alternative. LEVEL OF EVIDENCE: Level 2; Prospective non-randomized comparison study.

Massive intraoperative thrombus of the aortic arch and proximal descending aorta

A 49-year-old male patient presented with a paravalvular leakage 18 years after aortic valve replacement. The patient received a mechanical valve and was weaned uneventfully from cardiopulmonary bypass. After a drop in the pressure curve of the left radial artery an additional line was placed in the proximal ascending aorta showing normal systemic pressure. Transesophageal echocardiography showed a massive circular thrombosis of the distal aortic arch. The patient received a covered stent to expand the residual aortic lumen and left the hospital in good health.