Development and validation of a hybrid simulator for ultrasound-guided laparoscopic common bile duct exploration.

BACKGROUND: Ultrasound-guided laparoscopic common bile duct exploration (LCBDE) is the surgical management of choledocholithiasis. The procedure presents significant benefits to patients but still fails to be generalised because of the complex set of skills it requires. A simulator for ultrasound-guided LCBDE would allow trainee surgeons as well as experienced surgeons who perform this surgery seldomly to practice and gain confidence. METHODS: This article presents the development and validation of an easily reproducible hybrid simulator for ultrasound-guided LCBDE which integrates real and virtual components of the task. We first developed a physical model made of silicone. The fabrication technique is replicable and allows quick and easy production of multiple models. We then applied virtual components onto the model to create training for laparoscopic ultrasound examination. Combined with a commercially available lap-trainer and surgical equipment, the model can be used for training the fundamental steps of the surgery through the trans-cystic or trans-choledochal approaches. The simulator was evaluated through face, content, and construct validation. RESULTS: Two novices, eight middle grades, and three experts were recruited to test the simulator. The results of the face validation showed that the surgeons found the model realistic visually and felt realistic when performing the different steps of the surgery. The content validation indicated the usefulness of having a training system to practice the choledochotomy, the choledochoscopy and stone retrieval, and the suturing. The construct validation highlighted the ability of the simulator to differentiate between surgeons with various levels of expertise. CONCLUSIONS: The hybrid simulator presented is a low-cost yet realistic model which allows the surgeons to practice the technical skills required for trans-cystic and trans-choledochal ultrasound-guided LCBDE.

Comparing terracotta and earthenware for multiple functionalities in microbial fuel cells.

The properties of earthenware and terracotta were investigated in terms of structural integrity and ion conductivity, in two microbial fuel cell (MFC) designs. Parameters such as wall thickness (4, 8, 18 mm), porosity and cathode hydration were analysed. During the early stages of operation (2 weeks), the more porous earthenware lost anolyte quickly and was unstable between feeding compared to terracotta. Three weeks later MFCs of all thicknesses were more stable and could sustain longer periods of power production without maintenance. In all cases, the denser terracotta produced higher open circuit voltage; however, earthenware the more porous and less iron-rich of the two, proved to be the better material for power production, to the extent that the thickest wall (18 mm) MFC produced 15 % higher power than the thinnest wall (4 mm) terracotta. After 6 weeks of operation, the influence of wall thickness was less exaggerated and power output was comparable between the 4 and 8 mm ceramic membranes. Cylindrical earthenware MFCs produced significantly higher current (75 %) and power (33 %) than terracotta MFCs. A continuous dripping mode of cathode hydration produced threefold higher power than when MFCs were submerged in water, perhaps because of a short-circuiting effect through the material. This shows a significant improvement in terms of biosystems engineering, since a previously high-maintenance half-cell, is now shown to be virtually self-sufficient.