Bioengineering
　　Bioengineering is concerned with the application of engineering to the biological sciences and medicine. Research in this field at MEL aims to improve our basic knowledge of living beings and apply that knowledge to the development of health care systems. An advanced understanding of biomechanics is a prerequisite for successful research in bioengineering. Mel's research includes the following topics:
　
　1) The biomechanics of bone and muscle
　2) Biocompatibility evaluation techniques
　3) Development and standardisation of advanced biomaterials
　4) Artificial heart development
　5) Optical tomography
　6) Non-invasive measurement of brain function
　7) Novel MRI/S techniques
　8) Development of laser ablation techniques
　9) Computer aided surgery
　Some of these are described below.
　
Development and standardisation of advanced biomaterials
　Several different materials are currently used for body implants. The use of Ti-6% A1-4%V ELI alloy is currently increasing. The biological effects of various metallic ions on the cell growth ratio of fibroplasts L929 and osteoblast-like MC3T3-EI cells were investigated using various different metallic powders (Fig.1).
　
Fig.1 Relative cell growth ratio for various metallic concentration in the medium.

It was found that tough Ti, Zr, Sn, Nb, and Ta appear to have no effect, but Al and V ions exhibit cytotoxicity at high concentrations. A newly developed Ti-15%Zr-4%Nb-4% Ta-0.2%Pd alloy was found to have improved corrosion resistance in physiological saline solution. By adding 0.2%O and 0.05%N and applying heat treatment, the ultimate tensile strength was improved to 1000MPa, the total elongation improved to more than 10%, and the fatigue strength was found to be 950MPa after 1.0E+08 cycles. Cell growth ratios were found to be almost normal up to 105 cycles, but a sharp decrease was observed when V ions were released into Eagle's MEM solution.[26,28,31,32,36,44] Work has also been done on the transport properties of biomembranes, and the structures of films of polymers such as polyvinyl alcohol gel, and the interactions between the film and transporting material in a hydrophobic environment have been investigated.
　
　
Artificial heart development
　A centrifugal blood pump incorporating a permanent magnet and ceramic mono-pivot bearing is under development for application as an implantable artificial heart. Satisfactory pump performance was obtained from a recently developed model (Fig.2) with an impeller 50mm in diameter and a drive unit 8mm thick. By improving the impeller geometry, the required pressure (100mmHg) and flow rate (5L/min) were obtained at reasonable speed (1,900 rpm) and total efficiency (13%). The secondary and boundary layer flows - which are important in thrombus formation and haemolysis - are currently under investigation using flow visualisation techniques with a high speed video camera and laser light sheet. Haemolysis tests using animal blood and equivalent slurries showed that mechanical cell damage was at a similar level to that found in commercial centrifugal blood pumps. [33.34,35,43]
　
Fig.2 A newly developed monopivot magnetic suspension blood pump for an implantable artificial heart.
　
Optical tomography
　Optical tomographic imaging using near infrared light has potential as a non-invasive measurement technique for determining the oxygenation state of living tissue. Unfortunately, light is strongly scattered by tissue and an understanding of photon migration in living organisms is necessary. Computer codes have been developed to simulate photon migration, and a new algorithm based on inversion techniques has been devised for optical tomography. Solid phantoms simulating the human head have been designed and fabricated using an optical rapid prototyping technique. These will be used to validate the photon migration model and the new algorithm. [27,38,39,40,41,47,48]
　
Fig.3 Optical human head phantom (white matter of a brain taken from MRl head image) for validation of photon migration model and new algorithm.
　
Fig.4 Metabolic Measurements by MRl (a) with Microdialysis (b).
　
Novel MRI/S techniques
　Magnetic Resonance Imaging and Spectroscopy (MRI/S) techniques can be used to measure the concentration of nuclei such as hydrogen and phosphoric acid in biological tissue, and give images of their concentration distribution in two- or three-dimensions. We have developed several novel MRI/S techniques including: Fast three-dimensional T2 weighted imaging with high S/N ratio, and two-dimensional per fusion imaging with chemical selection. These techniques are useful as diagnostic techniques in medicine and biology. [49.50]
　
Computer aided surgery
　Computer Aided Surgery (CAS) uses techniques from both clinical medicine and engineering, for example, mechatronics, optics, and information technology. Demand for intra-operative simulation, registration, and navigation is driving the development of techniques for handling soft organs such as: non-rigid registration, interventional imaging, and surgical robots. This work requires mechanical models of the soft organs such as the brain and the liver. We have proposed new equations for modelling the properties of brain tissue which use a single-phase non-linear visco-elastic model derived from in-vitro examination. The model has been validated by comparison with in-vivo indentation tests on pig brain tissue.
　
The combination of interventional MRI and surgical robots is a promising but challenging project. We are developing MRI-compatible machines for biomechanical studies, and one of these, a MRI-compatible surgical manipulator which uses no ferromagnetic materials, is shown in the Fig.5 below. [51]
　
Fig.5 MR compatible stress/extension machine, which can locate inside the imagine region.

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