Alluvial substrate mapping by automated texture segmentation of recreational-grade side scan sonar imagery.

Side scan sonar in low-cost 'fishfinder' systems has become popular in aquatic ecology and sedimentology for imaging submerged riverbed sediment at coverages and resolutions sufficient to relate bed texture to grain-size. Traditional methods to map bed texture (i.e. physical samples) are relatively high-cost and low spatial coverage compared to sonar, which can continuously image several kilometers of channel in a few hours. Towards a goal of automating the classification of bed habitat features, we investigate relationships between substrates and statistical descriptors of bed textures in side scan sonar echograms of alluvial deposits. We develop a method for automated segmentation of bed textures into between two to five grain-size classes. Second-order texture statistics are used in conjunction with a Gaussian Mixture Model to classify the heterogeneous bed into small homogeneous patches of sand, gravel, and boulders with an average accuracy of 80%, 49%, and 61%, respectively. Reach-averaged proportions of these sediment types were within 3% compared to similar maps derived from multibeam sonar.

Outcome of three common bariatric procedures in the public sector.

BACKGROUND: In Australia, over 90% of bariatric surgery is performed in the private sector by paying patients with health insurance. The demand for government funded services is overwhelming and data are needed on the efficiency, safety and effectiveness of the current range of bariatric procedures in a public hospital setting. The aim of this study was to document medium term outcomes of gastric banding (laparoscopic adjustable gastric banding (LAGB)), gastric bypass (Roux-en-Y gastric bypass (RYGB)) and sleeve gastrectomy (SG) in a publicly funded programme. METHODS: Primary cases with minimum 18 months' follow up were included. Hospital usage, complications, weight loss and co-morbidity outcomes were compared. RESULTS: A total of 229 patients (125 LAGB, 42 RYGB, 62 SG) were included. Mean weight (body mass index) for LAGB, RYGB and SG was 130.6 (46.3), 137.2 (50.5) and 162.7 (55.2) kg (kg/m2 ), respectively (P < 0.001). Operative time and hospital stay were longest for RYGB and intensive care stay was longest for SG. Major complications occurred at 0.0%, 11.9% and 12.9% (P < 0.001) and major reoperations occurred over 5 years 11.2%, 21.4% and 6.5% (P = 0.064). Mean (standard deviation) excess weight loss was 29.9% (33.1), 75.7% (31.8) and 52.7% (19.7) with mean follow up of 3.6 years and 79.0% complete data. CONCLUSIONS: In our public bariatric programme, LAGB patients perform relatively poorly. An increased focus on SG may be appropriate as weight loss is more reliable, major reoperation rates are low and follow up less important. Our experience should be useful for those considering how best to structure and fund a public bariatric programme.