Success of any needle-based medical procedures depends on accurate placement of the needle at the target location. However, accurate targeting and control of flexible self-actuating (active) needle are challenging. We have developed a shape memory alloy-actuated flexible needle steered by a 3D Cartesian robot and performed a comparative study of four, non-model-based, coordinated control methodologies for the combined robot steering and flexible-needle insertion process for surgical interventions. Investigated four controllers are: proportional–integral–derivative (PID), PID with the cubic of positional error term (PID-P3), static PID sliding mode controller, and robust adaptive PID sliding mode controller (RAPID-SMC). Relative efficacies of these controllers are demonstrated by performing experiements using a tissue-mimicking soft material phantom. Results from experiments have reavealed that RAPID-SMC is superior to other three controllers.

Background: In recent years, the diagnosis of infective endocarditis has been enhanced by the use of echocardiography. We sought, therefore, to review its effect on the management of endocarditis in children. Methods: We reviewed all the patients presenting to our institution for evaluation for infective endocarditis from May 1994 to January 2002. The patients were stratified according to whether or not they had congenitally malformed hearts. Results: Of the 90 referred patients identified, 46 (51%) had positive ultrasonic findings. Of these, we excluded 26 patients because of the presence of indwelling lines. The remaining 20 patients with features of endocarditis had a median age of 6.5 years, and a range from 0.14 to 8.5 years. There were 4 patients with normal hearts, and 16 with congenital cardiac malformations. We identified rupture of a sinus of Valsalva in four patients, with rupture into the left ventricle in two, and into the right ventricle and right atrium in one each. The mitral valve was involved in six patients, the aortic valve in another six, including all four with rupture of the sinus of Valsalva, both mitral and aortic valves in three, the pulmonary trunk in three patients, and the tricuspid valve and a Blalock-Taussig shunt in one patient each. Organisms isolated included Streptococcus mitis in 4 patients, Streptococcus pneumoniae in 2 patients, Streptococcus sanguis in 1, Staphylococcus aureus in 3, Staphylococcus epidermidis in 1, and Enteroccocus in 2. Cultures proved negative in 7 patients. Surgical intervention was needed in 12 patients, and one died (5%). Only the left-sided chambers were involved in those with normal hearts. Both patients infected with Streptococcus pneumoniae had rupture of a sinus of Valsalva. Conclusion: Involvement of the left-sided chambers is more likely in structurally normal hearts, and in cases with rupture of a sinus of Valsalva, in which case infection with Streptococcus pneumonia should be suspected.