Biomedical Engineering: Applications, Basis and Communications

This paper is concerned with an attempt to produce a system to control anaesthetic depth in an animal model. The problems of deciding which parameter to use as an index of anaesthetic depth and the peculiar pharmacology of anaesthetic drugs will be explored.

This paper presents the development of surgical navigation robot, which is designed based on the image servo tracking technique. The surgical navigation robot plays an important role to the computer aided surgery (CAS), since it provides the patient's space coordinate during surgical navigation stage in real-time. Especially, the proposed active image servo tracking based surgical navigation robot can track the surgical marker that is mounted on the patient's hard tissue of the surgical position, so that the navigation space can be automatically extended. The proposed surgical navigation robot system consists of the in-lab designed dual-axis eye-in-hand robot (EIHR), digital signal processor (DSP) based EIHR motion controller, image servo tracking and positioning software. The EIHR robot is composed of the dual-axis robot mechanics and two CCD cameras, which acts as the stereoscopic image capture platform. The DSP based EIHR motion controller is designed to control the EIHR robot in a desired velocity, so that the surgical marker can be dynamically tracked. The image servo tracking and positioning software is the kernel of this work, and it is composed of image capture and recognition module, fuzzy logic based surgical marker tracking module and surgical marker positioning module. The image capture and recognition module is developed to abstract the image features of the surgical marker. The intelligent fuzzy logic based surgical marker tracking module is capable of generating robot's control command so that the surgical marker can be tracked within the desired target window. In addition, the surgical marker positioning module is used to calculate the surgical marker's space coordinates in terms of the features of stereoscopic images and the robot's posture. Finally, the prototype had been finished, and the experiment results showed that proposed EIHR achieved 1.7 mm position error within 500 mm operation range.

Endoprosthetic reconstruction using a custom-made metallic megaendoprosthesis is one of the common modalities for the limb salvage operation. The new promising advance of material science, design and fabrication of the endoprosthesis enable an immediate rehabilitation program and provide a durable and functional limb. Thus a successful limb reconstruction is possible in the well-selected patients. In addition to the endoprosthesis-related increased stress, a limited soft tissue support and constraint after limb salvage procedure usually results in an increased incidence of complications, especially in the long term survivors. Some patients may even need revision of the endoprosthesis and, at times, amputation.

The complications after oncological endoprosthectic reconstructions usually occur more frequent than the conventional primary total joint arthroplasty. Considering the characteristics of the surgical procedure and the high demands on the implants, such a relatively high frequency of complications is not unexpected. The common complications include wound necrosis, aseptic loosening, fatigue fracture, local osteolysis, joint contracture, dislodgement/dislocation, nerve or vascular injury, rotational deformity, leg length discrepancy, infection, periprosthectic fracture, etc. Some complications are encountered with other modality of limb salvage procedure, whereas the other endoprosthesis-related complications are endoprosthetic-unique and not uncommon. The major causes of such a relatively high endoprosthesis-related complications include (1) extensive excision of soft tissue, leading to change of biomechanical ergonomics, little soft tissue constraints or support for a long replacement segments, and decreased local defense to infection, (2) increased stress on the implants due to higher activity level in the youthful active individuals, relatively narrower medullary canals with less cancellous bone for fixation, (3) special needs for the stability resulting an increased mechanical constraints placed directly within the endoprosthesis, thus raising the local stress transferred to the prosthesis, and to the prosthesis-bone interface, (4) poor immunological, hematological, or nutritional status resulting from chronic oncologic diseases or chemotherapy. It in turn accelerates the wear processes of the components, induces the wear particulate disease and local osteolysis, as well as to cause the aseptic loosening eventually. Early detection and early correction of minor complications has an important role of preventing the major complications, thus reduces the necessity of reoperation, and at times, amputation. We will review these complications in this article.

In this study, the formation of the shear stress on the three-dimensional realistic health and dissected aortic dissection models is investigated under the laminar Newtonian flow assumption with Reynolds numbers 100 to 600. Numerical simulation shows that strong oscillating positive-negative wall stress distributions are found along both the lower and upper aortic vessels during the whole pulsatile cycle. Especially, the location of maximum wall shear stress is always found around the beginning of dissected aortic vessel. However, due to three ascending branch effects, the location of the wall stress extreme on upper arch is moved upward from the dissected vessel surface to the location behind the third ascending branch.

There are many different kinds of biopotential signal. These signals are tiny in amplitude and the measurement is easily corrupted by external interference. For these reasons, the design of high-quality biopotential amplifier is usually an empirical task. To make the design of biopotential amplifier more efficient, this study proposes a simulation model for bioelectric signal measurement such that the design task can be achieved thoroughly by powerful computer-aided design (CAD) tool. The proposed model has two distinct features, one is the simulated biopotential signal is used for the genesis of biosignal, and the other one is the skin-electrode impedance is replaced by its corresponding equivalent circuit, which is a complex RC network. To verify the feasibility of the proposed model, an ECG amplifier is designed in Spice-related CAD tool and is implemented for ECG recording. From the results, the amplifier characteristics agree well between the simulated and the implemented circuit. Besides, the effect due to the commonly encountered power-line interference during biopotential measurement can be reasonably evaluated in the proposed model.

A better understanding of the kinematics and control strategies adopted during obstacle crossing is essential for the prevention of injuries associated with falls in the elderly. The effects of obstacle height on the foot clearance, foot-obstacle distance and joint kinematics have presented significant controversy. This may be related to the selection of obstacle height, whether the obstacles are normalized to the leg length, and to the calculation of the foot-obstacle clearance, as well as the extraction of representative joint angles for the analysis. In this study, fourteen young healthy adults wearing 28 infrared retroreflective markers walked and crossed obstacles of heights of 0%, 10%, 20% and 30% of their leg lengths in a gait laboratory equipped with a 3D motion analysis system. Three-dimensional joint kinematics of the lower limb were calculated. Foot clearances were calculated using the heel and toe markers. The results suggested that young subjects maintained a constant margin of leading foot clearance when crossing higher obstacles (higher than 79.4mm) and a constant trailing foot clearance for all obstacle heights. Both toe-obstacle and heel-obstacle horizontal distances were not affected by obstacle height. Apart from the peak values, kinematic variables for the leading limb should be considered both when the toe and heel cross the obstacle while only those when the toe crosses the obstacle for the trailing limb. Not only in the sagittal plane, motions of the lower limb in the other two planes were also important when investigating the kinematics of the leading limb during obstacle crossing. The present study clarified some of the controversies in the literature of obstacle-crossing through careful comparisons of kinematic variables obtained from different study aspects. The results will be helpful for future studies to gain insight into the kinematics and control strategies adopted during obstacle-crossing.