A detailed investigation of left ventricle (LV) flow patterns could improve our understanding of the function of the heart and provide further insight into the mechanisms of heart failure. This study presents patient-specific modelling with magnetic resonance imaging (MRI) to investigate LV blood flow patterns in normal subjects. In the study, the prescribed LV wall movements based on the MRI measurements drove the blood flow in and out of the LV in computational fluid dynamics simulation. For the six subjects studied, the simulated LV flow swirls towards the aortic valve and is ejected into the ascending aorta with a vertical flow pattern that follows the left-hand rule. In diastole, the inflow adopts a reasonably straight route (with no significant secondary flow) towards the apex in the rapid filling phase with slight variations in the jet direction between different cases. When the jet reaches about two thirds of the distance from the inflow plane to the apex, the blood flow starts to change direction and swirls towards the apex. In the more slowly filling phase, a centrally located jet is evident with vortices located on both sides of the jet on an anterior-posterior plane that passes through the mitral and aortic valves. In the inferior-superior plane, a main vortex appears for most of the cases in which an anticlockwise vortex appears for three cases and a clockwise vortex occurs for one case. The simulated flow patterns agree well qualitatively with MRI-measured flow fields.
The combination of computational fluid dynamics (CFD) and magnetic resonance imaging (MRI) offers a promising tool that enables the prediction of blood flow patterns in subject-specific cardiovascular models. The influence of the model geometry on the accuracy of the simulation is well recognized. This paper addresses the impact of different boundary conditions on subject-specific simulations of left ventricular (LV) flow. A novel hybrid method for prescribing effective inflow boundary conditions in the mitral valve plane has been developed. The detailed quantitative results highlight the strengths as well as the potential pitfalls of the approach.
The introduction of surgical robotics to the field of surgical oncology brings with it an expectation not only of improved vision, instrumentation, and precision but also as a result, a potential for improved oncological outcomes. The current interest in the field of oesophagogastric oncology is explored in this review together with the benefits, real and potential, that robotic assistance offers surgical cancer resection as well as some of the limiting factors which may be hampering its uptake into current surgical practice. A systematic review of all the published literature up until April 2010 was examined across the field of esophageal and gastric cancer resection. A quantitative assessment of the oncological, operative, and functional outcomes was determined from each procedure. The level of evidence behind the results was determined using the Oxford Centre for Evidence-based Medicine Levels of Evidence; Therapy and Prevention. Three hundred and five cases from 19 independent studies were included for review. Nine studies explored the outcomes from robotic-assisted esophagectomy and eight, the robotic-assisted gastrectomy. Two articles included small case series of both procedures. The level of evidence was predominantly based on case series or expert opinion (Level 4 or 5) with only three unmatched or poorly matched comparative trials (Level 4) with no randomized trials evident. Improved operative outcomes and hospital stays were demonstrated with a reduction of 2 days when the robotic-assisted gastrectomy technique was employed compared with the open. No improvement in oncological outcomes could be identified with the use of the robot for either oesophageal or gastric cancer resection; however, in terms of short-term oncological outcomes, these were at least equivalent to the open approach for oesophageal cancer and early stage gastric cancer. Robotic-assisted laparoscopic surgery is a feasible technique to use to perform a safe and oncologically sound resection for oesophageal and early gastric cancer. Operative benefits appear to be encouragingly similar to the laparoscopic approach with some demonstration of improvement over the open technique despite a prolonged operative time. However, the level of evidence is suboptimal and more randomized controlled trials and long-term survival studies within a framework of measured and comparable outcomes is required.
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