A collaborative robotic platform for sensor-aware fibula osteotomies in mandibular reconstruction surgery.

Precision and safety are crucial in performing fibula osteotomy during mandibular reconstruction with free fibula flap (FFF). However, current clinical methods, such as template-guided osteotomy, have the potential to cause damage to fibular vessels. To address the challenge, this paper introduces the development of the surgical robot for fibula osteotomies in mandibular reconstruction surgery and propose an algorithm for sensor-aware hybrid force-motion control for safe osteotomy, which includes three parts: osteotomy motion modeling from surgeons' demonstrations, Dynamic-system-based admittance control and osteotomy sawed-through detection. As a result, the average linear variation of the osteotomized segments was 1.08±0.41mm, and the average angular variation was 1.32±0.65∘. The threshold of osteotomy sawed-through detection is 0.5 at which the average offset is 0.5mm. In conclusion, with the assistance of surgical robot for mandibular reconstruction, surgeons can perform fibula osteotomy precisely and safely.

The Relationship between Cuff Pressure and Air Injection Volume of Endotracheal Tube: A Study with Sheep Trachea Ex Vivo.

Background: Endotracheal intubation is a widely used treatment. Excessive pressure of the endotracheal tube cuff leads to a series of complications. Here, we used tracheae of sheep to analyze the relationship between the air injection volume and endotracheal tube cuff pressure so as to guide the doctors and nurses in controlling the pressure of the endotracheal tube cuff during clinical work and minimise the risk of complications. Materials and Methods: Forty sheep tracheae were utilised and were divided into five groups according to their diameters. Different sizes of endotracheal tubes were inserted into each trachea, and the cuff pressure with the increase of air injection volume was recorded. The formulas that reflect the relationship between air injection volume and cuff pressure were obtained. Then, sheep tracheae were randomly selected; different types of tubes were inserted, and the stipulated volume of air was injected. The actual pressure was measured and compared with the pressure predicted from the formulas. Statistical analysis was conducted to verify whether the formulas obtained from the first part of the experiment were in accordance with the expert evaluation table, which consists of opinions of several experts. Results: After obtaining 15 formulas, we collected the differences between the theoretical cuff pressure and the actual cuff pressure that satisfied the expert evaluation. Relying on the formulas, the medical turntable was obtained, which is a tool that consists of two round cards with data on them. The top card has a notch. The two cards are stacked together, and as the top card rotates, the data on the bottom card can be easily seen in a one-to-one relationship. Conclusion: The formulas are capable of showing the relationship between the cuff air injection volume and pressure of endotracheal tube cuff. The medical turntable can estimate the air injection volume to ensure that the pressure stays in an acceptable range.

Pilot study of a surgical robot system for zygomatic implant placement.

Zygomatic implant technology has been regarded as an alternative treatment to massive grafting surgery in the severe atrophic maxillary. Nowadays, the assistant method with a real-time surgical navigation has been applied to reduce the risks of zygomatic implant placement. However, the accuracy of the complex operation is highly dependent on the experience of the surgeon. In order to avoid disadvantages of traditional surgical navigation systems, a novel surgical robot system for the zygomatic implant placement has been designed and developed. Firstly, the drilling trajectory of the zygomatic implant placement is designed through the pre-operative planning system. Secondly, the real-time positions of the surgical instruments are constantly updated with the guidance of the optical tracker. Finally, through a coordinate transformation algorithm, the drilling performance can be conducted with the control of a six degree of freedom robot. In order to evaluate the accuracy of the robot, phantom experiments had been carried out. The angle, entry point and exit point deviation of the robotic system are 1.52 ±â€¯0.58°, 0.79 ±â€¯0.19 mm, and 1.49 ±â€¯0.48 mm, respectively. Meanwhile, a comparison between the robotic and manual operation demonstrates that the use of the surgical robot system for the zygomatic implant placement can improve the accuracy of the operation.

An oral and maxillofacial navigation system for implant placement with automatic identification of fiducial points.

PURPOSE: Surgical navigation system (SNS) has been an important tool in surgery. However, the complicated and tedious manual selection of fiducial points on preoperative images for registration affects operational efficiency to large extent. In this study, an oral and maxillofacial navigation system named BeiDou-SNS with automatic identification of fiducial points was developed and demonstrated. METHODS: To solve the fiducial selection problem, a novel method of automatic localization for titanium screw markers in preoperative images is proposed on the basis of a sequence of two local mean-shift segmentation including removal of metal artifacts. The operation of the BeiDou-SNS consists of the following key steps: The selection of fiducial points, the calibration of surgical instruments, and the registration of patient space and image space. Eight cases of patients with titanium screws as fiducial markers were carried out to analyze the accuracy of the automatic fiducial point localization algorithm. Finally, a complete phantom experiment of zygomatic implant placement surgery was performed to evaluate the whole performance of BeiDou-SNS. RESULTS AND CONCLUSION: The coverage of Euclidean distances between fiducial marker positions selected automatically and those selected manually by an experienced dentist for all eight cases ranged from 0.373 to 0.847 mm. Four implants were inserted into the 3D-printed model under the guide of BeiDou-SNS. And the maximal deviations between the actual and planned implant were 1.328 mm and 2.326 mm, respectively, for the entry and end point while the angular deviation ranged from 1.094° to 2.395°. The results demonstrate that the oral surgical navigation system with automatic identification of fiducial points can meet the requirements of the clinical surgeries.

Surface profiling of an aspherical liquid lens with a varied thickness membrane.

Inspired by crystalline lenses in human eyes, liquid lenses have a simple yet elegant working principle, and result in compact optical systems. Recent numerical studies showed that membranes with variable thicknesses could affect the lens profile. However, fabrication and assembly of a liquid lens with an inhomogeneous membrane is difficult. There is also a lack of experimental studies about the changes of a lens profile during deformation. In this paper, we provided a new experimental approach for characterizing the performance of a liquid lens with an inhomogeneous membrane. A 2D axisymmetric lens model was built in finite element analysis software to theoretically study the non-linear deformation behavior of the inhomogeneous membrane. Then we provided a new approach to fabricate inhomogeneous membranes using a pre-machined aluminum mold. An optical coherence tomography (OCT) system was used to dynamically measure the changes of a lens profile without contact. Both simulation and the experiments indicated that the variation of the thickness of the membrane could affect the lens profile in a predictable manner. A negative conic constant was achieved when a plano-concave membrane was adopted in a liquid lens. Larger increments of the thickness of the membrane in the radial direction resulted in a larger contribution of a conic constant to the lens profile. The presented study offers guidance for image-quality analysis and optimization of a liquid-lens-based optical system.