RESUMO
A 78-year-old patient who underwent an aortic valve replacement presented 6 months later with clinical symptoms suspicious for prosthetic valve endocarditis. Echocardiography showed no features suggestive of endocarditis, but a positron emission tomography/computed tomography with fluorine-18-fluorodeoxyglucose (18F-FDG PET/CT) scan showed an area of hyper-uptake around the ascending aorta. We realized that the sheet of Surgicel (Ethicon, Bridgewater, NJ) hemostat had been placed over the aortotomy suture line at the time of surgery. Another follow-up PET/CT scan performed 22 months later showed that the hyper-uptake focus remained persistent. False-positive hyper-uptake on an 18F-FDG PET/CT scan owing to local hemostatics should be considered when interpreting the findings of this technique.
Assuntos
Valva Aórtica/cirurgia , Celulose Oxidada/efeitos adversos , Endocardite/diagnóstico por imagem , Fluordesoxiglucose F18 , Próteses Valvulares Cardíacas , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Complicações Pós-Operatórias/diagnóstico por imagem , Compostos Radiofarmacêuticos , Idoso , Diagnóstico Diferencial , Humanos , MasculinoRESUMO
The topological derivative tool is applied here in structural health monitoring (SHM) problems to locate small defects in a material plate with complex geometry that is subject to permanent multifrequency guided waves excitation. Compared to more standard SHM methods, based in measuring the time-lag between emitted and received propagative pulses plus some postprocessing, the topological derivative somehow compares the measured and computed (solving the full elasto-dynamic equations) response of the damaged plate, instead of relying on only the time of flight of the wave. Thus, the method profits the knowledge behind the physics of the problem and can cope with scenarios in which classical methods give poor results. The authors of this paper have already used the topological derivative in rectangular plates with constant thickness, but with defects consisting simply in both through slits and inclusions of a different material, and actuators/sensors located near the boundary, which makes very difficult to use standard SHM methods. This is an extension of the method, also considering the much more difficult to analyze case of plates with variable thickness and complex (non-rectangular) planform.
