Titanium dental implants (screws) are commonly used to replace missing teeth by forming a biological union with bone (“osseointegration”). Micro-computerised tomography (µCT) may be useful for measuring bone mineral density around dental implants. Major issues arise because of various artefacts that occur with polychromatic X-rays associated bench type instruments that may compromise interpretation of the observations. In this study various approaches to minimise artefacts such as; beam hardening, filtering and edge effects are explored with a homogeneous polymeric material, Teflon, with and without an implant present. The implications of the limitations of using such polychromatic µCT systems to quantify bone mineral density adjacent to the implant are discussed.
Vascular diseases, such as ischemic heart disease, infarction, aneurysms, stroke and stenosis are a leading cause of serious long-term disability and their mortality rate is as high as that of cancers in many countries. Recently, neurovascular intervention using catheters is a minimally-invasive endovascular technique used to treat vascular disease of the brain, and a navigation system for catheters has been developed to facilitate surgical planning and to provide intra-operative assistance. Since the mechanical properties of a catheter play an important role in reaching the targeted disease, tracking of catheter movement during endovascular treatment may be useful to increase confirmation of the rate of successful operation. In this study, we developed an in vitro tracking system for catheter motion using poly (vinyl alcohol) hydrogel (PVA-H) to mimic an arterial wall. The employed models were made of PVA-H, which is sufficiently transparent to permit observation of catheter movement in the artery. This system is expected to contribute to validation of computer-based navigation systems for surgical assistance.
The purpose of this study was to reproduce the force in a voluntary contraction via surface electromyography (SEMG) using a systematic muscle model. We measured the isometric voluntary contractile force and SEMG of the human biceps. We examined the effect of the electrode size on SEMG. A pair of electrodes with a diameter of 1 mm was adopted, because they avoided signal interference from the action potentials of other motor units. We added a converter to the muscle model to obtain an artificial action potential that successively drives an excitation-contraction controller and a motor unit. When the force was less than 30% of the maximum force, EMG signals were obtained from a few motor units. The resultant force coincided well with the experimentally observed force with an accuracy of around 90% when an appropriate threshold level was set up in the converter. This method will increase in performance when we can separately detect the SEMG signals from multipoint measurements.
The success of total hip arthroplasty (THA) in improving joint function and reducing pain is regarded as one of the great achievements of modern medicine. Today, most femoral stems with cementless fixation are made of either cobalt-chrome-molybdenum (CoCrMb) or titanium-aluminum-vanadium (TiAlV) alloys. In order to obtain adequate initial stability of the cementless femoral stem, the implant must be placed in contact with bone of sufficient strength to support the prosthesis rigidly. This study introduces a unique approach in this research category, making use of shape memory alloys (SMA) for cementless stems to obtain adequate initial stability. Using SMA that exhibits a shape memory effect, better proximal fit and fill with smooth insertion will be accomplished. In this study, numerical evaluation is intended with initial stability of a cementless stem for which SMA is utilized. A result of the numerical analysis reveals that use of SMA is found to be effective enough to obtain rigid initial stability.
An auditory brain-computer interface (BCI) which detects event-related potentials (ERPs) elicited by selective attention to one of the tone streams was proposed. Two frequency oddball tone sequences with different tone frequency ranges were alternately presented to subjects, and were perceived by subjects as two kinds of segregated streams. Event-related potentials elicited by two kinds of deviant tones were classified by linear discriminant analysis (LDA) to find the stream subjects paid selective attention to. Experiments with six subjects have shown that this system could realize binary selection from two tone streams.
Biomimetic robots have received more and more attention, as people try to learn from nature in which exist amazing and uniquely evolved mechanisms shown by very species. Fleas, as such one example, are best jumper of all known animals in the world, considering their body size. It can jump about 150 to 200 times its own body length. This paper reports on modeling and simulation of jumping mechanism of a biomimetic robot and provides a guide line for designing and modeling the biomimetic robot that can mimic fleas to jump very high length with respect to its body length.
Finger Braille is one of the communication media of deafblind people. In one-handed Finger Braille, a sender dots the left part of the Braille code on the distal interphalangeal (DIP) joints of the index, middle and ring fingers of a receiver, and subsequently dots the right part of the Braille code on the proximal interphalangeal (PIP) joints of the same fingers. Because there is a small number of non-disabled people who are skilled in Finger Braille, deafblind people communicate in this medium only through an interpreter. In this study, we developed a Finger Braille recognition system using small piezoelectric accelerometers worn by the receiver. We first conducted a measurement experiment to derive algorithms for the recognition of the dotted fingers and positions. The results showed that the accuracy of the recognition of dotted fingers was 92.9%, and the recognition system was independent of the dotted strength, dotted position and receiver. The accuracy of the recognition of dotted positions was 81.9%, and the recognition system could recognize dotted positions if the receiver's hand formed a natural longitudinal arch on the desk. Next, an evaluation experiment was carried out. The results showed that the accuracy of the recognition of dotted fingers by dotting was 89.7%, and the accuracy of recognition of dotted positions by dotting was 92.3%. Therefore, the recognition system could recognize sentences accurately when the interpreter dotted clearly.
A variety of operation devices have been developed for severely disabled people such as those with cervical cord injuries and/or muscular dystrophies. Each device has its own merits and demerits respectively, but there is still a need to develop other types of operation devices. In this study, we have tried to develop a mouthpiece type remote controller to operate an electric powered wheelchair. This remote controller would be inserted into user's mouth and be operated by tongue. This remote controller has passive RFID transponders but no battery. To evaluate the performance of this system, the MCR (Maximum Communication Range) was measured. The results indicated that if users set the antenna beside their cheek, the remote controller would work well. For the preliminary study, the operativeness of this remote controller was suitable. With this system, we succeeded in an operating electric powered wheelchair on the market. These results suggested the possibility that this mouthpiece type remote controller system would be effective for severely disabled people.
This paper reports the first steps in determining the effects of fluid flow on the performance of the mitral valve of the heart that is relevant to surgical repair of the valve. In this paper, blood flow in idealised two-dimensional models of the mitral valve was studied using a numerical fluid-structure interaction (FSI) and experimental models and an experimental problem designed to validate the computational model. Both the experiments and simulation predicted a large vortex behind the anterior leaflet during inflow of blood into the left ventricle, in agreement with MRI scans available in the literature. Leaflet deformations agreed with results from experiments in the literature and with our previous experimental results.
In the present study, the characteristics of both flow and heat transfer in a pharyngeal cooling cuff for the treatment of brain hypothermia were investigated experimentally and numerically. The pharyngeal cooling cuff, which is a balloon-like structure placed in the pharynx, was developed for medical purposes. As a method for controlling the brain temperature, cooling water, which is physiological saline at 5°C, is injected into the cuff in order to cool the common carotid artery, which is adjacent to the pharynx. In this study, the heat transfer characteristics between the cuff wall and phantom body, which was considered to be equivalent to the human body, were experimentally determined, and the flow behaviour in the cuff was observed in detail. Furthermore, a three-dimensional numerical simulation was carried out to investigate both the flow velocity and temperature distribution in the cuff.