Design of Adjustable Magnetic Field Generating Device in the Capsule Endoscope Tracking System / 生物医学工程学杂志

The capsule endoscope swallowed from the mouth into the digestive system can capture the images of important gastrointestinal tract regions. It can compensate for the blind spot of traditional endoscopic techniques. It enables inspection of the digestive system without discomfort or need for sedation. However, currently available clinical capsule endoscope has some limitations such as the diagnostic information being not able to correspond to the orientation in the body, since the doctor is unable to control the capsule motion and orientation. To solve the problem, it is significant to track the position and orientation of the capsule in the human body. This study presents an AC excitation wireless tracking method in the capsule endoscope, and the sensor embedded in the capsule can measure the magnetic field generated by excitation coil. And then the position and orientation of the capsule can be obtained by solving a magnetic field inverse problem. Since the magnetic field decays with distance dramatically, the dynamic range of the received signal spans three orders of magnitude, we designed an adjustable alternating magnetic field generating device. The device can adjust the strength of the alternating magnetic field automatically through the feedback signal from the sensor. The prototype experiment showed that the adjustable magnetic field generating device was feasible. It could realize the automatic adjustment of the magnetic field strength successfully, and improve the tracking accuracy.

Clinical evaluation of wedge-shaped defect restored by gingival retraction technique / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the periodontal conditions after the wedge-shaped defect was restored by gingival retraction technique.</p><p><b>METHODS</b>A total of 138 mandibular premolars with wedge-shaped defect were selected and divided into A, B groups. Group A was restored with Dyract after using retraction cord. Group B was directly restored with Dyract. Clinical parameters including plaque index (PLI), gingival index (GI), sulcus bleeding index (SBI), probing depth (PD), volumes of gingival crevicular fluid (GCF) and levels of aspartate aminotransferases (AST) of gingival crevicular fluid were measured at baseline, 1 week, 1 month, 3 months and 6 months after operation.</p><p><b>RESULTS</b>There was no difference in PLI, GI, SBI, PD between group A and B during 6 months after operation, while the difference of GCF and AST was significant between group A and B at 3 months and 6 months after operation (P < 0.05, P < 0.01).</p><p><b>CONCLUSIONS</b>Gingival retraction technique applied in wedge-shaped defect restoration can reduce the damage to the periodontal tissue.</p>