The successful suppression of clutter arising from stationary or slowly moving tissue is one of the key issues in medical ultrasound color blood imaging. Remaining clutter may cause bias in the mean blood frequency estimation and results in a potentially misleading description of blood-flow. In this paper, based on the principle of general wall-filter, the design process of three classes of filters, infinitely impulse response with projection initialization (Prj-ⅡR), polynomials regression (Pol-Reg), and eigen-based filters are previewed and analyzed. The performance of the filters was assessed by calculating the bias and variance of a mean blood velocity using a standard autocorrelation estimator. Simulation results show that the performance of Pol-Reg filter is similar to Prj-ⅡR filters. Both of them can offer accurate estimation of mean blood flow speed under steady clutter conditions, and the clutter rejection ability can be enhanced by increasing the ensemble size of Doppler vector. Eigen-based filters can effectively remove the non-stationary clutter component, and further improve the estimation accuracy for low speed blood flow signals. There is also no significant increase in computation complexity for eigen-based filters when the ensemble size is less than 10.
ObjectiveTo investigate surgical indications and techniques of video-assisted thoracoscopic surgery (VATS) for mediastinal lymph node tuberculosis. MethodsClinical data of 27 patients who underwent VATS for mediastinal lymph node tuberculosis between January 2010 and March 2013 in Wuhan Medical Treatment Center were retrospectively analyzed. There were 16 male and 11 female patients with their age of 18-67 (30.23±10.72) years. ResultsThere was no in-hospital death. Postoperative complications included recurrent laryngeal nerve injury in 1 patient, delayed wound healing in 1 patient and pneumothorax in 1 patient. Postoperatively, all the patients received intensified anti-tubercular treatment, and were engaged in normal physical activities during follow-up of 6 months. ConclusionVATS is safe and reliable for the treatment of mediastinal lymph node tuberculosis, and anti-tubercular treatment is needed before and after the operation.