A new Monte Carlo program for simulating light transport through Port Wine Stain skin.

A new Monte Carlo program is presented for simulating light transport through clinically normal skin and skin containing Port Wine Stain (PWS) vessels. The program consists of an eight-layer mathematical skin model constructed from optical coefficients described previously. A simulation including diffuse illumination at the surface and subsequent light transport through the model is carried out using a radiative transfer theory ray-tracing technique. Total reflectance values over 39 wavelengths are scored by the addition of simulated light returning to the surface within a specified region and surface reflections (calculated using Fresnel's equations). These reflectance values are compared to measurements from individual participants, and characteristics of the model are adjusted until adequate agreement is produced between simulated and measured skin reflectance curves. The absorption and scattering coefficients of the epidermis are adjusted through changes in the simulated concentrations and mean diameters of epidermal melanosomes to reproduce non-lesional skin colour. Pseudo-cylindrical horizontal vessels are added to the skin model, and their simulated mean depths, diameters and number densities are adjusted to reproduce measured PWS skin colour. Accurate reproductions of colour measurement data are produced by the program, resulting in realistic predictions of melanin and PWS blood vessel parameters. Using a modest personal computer, the simulation currently requires an average of five and a half days to complete.

Feasibility of iterative learning control mediated by functional electrical stimulation for reaching after stroke.

BACKGROUND: An inability to perform tasks involving reaching is a common problem following stroke. Evidence supports the use of robotic therapy and functional electrical stimulation (FES) to reduce upper limb impairments, but current systems may not encourage maximal voluntary contribution from the participant because assistance is not responsive to performance. OBJECTIVE: This study aimed to investigate whether iterative learning control (ILC) mediated by FES is a feasible intervention in upper limb stroke rehabilitation. METHODS: Five hemiparetic participants with reduced upper limb function who were at least 6 months poststroke were recruited from the community. No participants withdrew. INTERVENTION: Participants undertook supported tracking tasks using 27 different trajectories augmented by responsive FES to their triceps brachii muscle, with their hand movement constrained in a 2-dimensional plane by a robot. Eighteen 1-hour treatment sessions were used with 2 participants receiving an additional 7 treatment sessions. OUTCOME MEASURES: The primary functional outcome measure was the Action Research Arm Test (ARAT). Impairment measures included the upper limb Fugl-Meyer Assessment (FMA), tests of motor control (tracking accuracy), and isometric force. RESULTS: Compliance was excellent and there were no adverse events. Statistically significant improvements were measured (P

A robotic workstation for stroke rehabilitation of the upper extremity using FES.

An experimental test facility is developed for use by stroke patients in order to improve sensory-motor function of their upper limb. Subjects are seated at the workstation and their task is to repeatedly follow reaching trajectories that are projected onto a target above their arm. To do this they use voluntary control with the addition of electrical stimulation mediated by advanced control schemes applied to muscles in their impaired shoulder and arm. Full details of the design of the workstation and its periphery systems are given, together with a description of its use during the treatment of stroke patients.

A microcontroller system for investigating the catch effect: functional electrical stimulation of the common peroneal nerve.

Correction of drop foot in hemiplegic gait is achieved by electrical stimulation of the common peroneal nerve with a series of pulses at a fixed frequency. However, during normal gait, the electromyographic signals from the tibialis anterior muscle indicate that muscle force is not constant but varies during the swing phase. The application of double pulses for the correction of drop foot may enhance the gait by generating greater torque at the ankle and thereby increase the efficiency of the stimulation with reduced fatigue. A flexible controller has been designed around the Odstock Drop Foot Stimulator to deliver different profiles of pulses implementing doublets and optimum series. A peripheral interface controller (PIC) microcontroller with some external circuits has been designed and tested to accommodate six profiles. Preliminary results of the measurements from a normal subject seated in a multi-moment chair (an isometric torque measurement device) indicate that profiles containing doublets and optimum spaced pulses look favourable for clinical use.

The functional form of the lognormal distribution as a sum of decaying exponential and sinusoidal terms applied to the isometric pinch force of human fingers.

The transient data of the pinch force produced between the human forefinger and thumb have been shown to fit the functional form of the well-known lognormal density function. Isometeric force generation is achieved by the stochastic recruitment of individual motor units, which sum together. Evidence from animal and human experiments demonstrates that the force generation can be modelled by underdamped terms. It is shown that a lognormal time series (distribution) can be fitted to a sum of exponential decaying sinusoidal terms.

Development of a lightweight and adaptable multiple-axis hand prosthesis.

The last few decades have produced significant improvements in the design of upper limb prostheses through the increasing use of technology. However the limited function exhibited by these devices remains rooted in their single degree of freedom format. Commercial myoelectric hand prostheses warrant high grip forces to ensure stable prehension due to a planar pincer movement. Hence precise and conscious effort is required on the part of the user to ensure optimum grip. Consumers have shown dissatisfaction with the status quo due to the excessive weight and poor function of existing artificial hands. Increasing the number of grasping patterns and improving the visual feedback from an object in the hand are cited as key objectives. This paper outlines the development of the six-axis Southampton-Remedi hand prosthesis that addresses these design issues by maintaining stable prehension with minimal grip force. Constraints such as modularity, anthropomorphism, and low weight and power consumption are factors that have been adhered to throughout the design process.

A new approach in artificial neuron theory for use in computer aided diagnosis.

An artificial neuron, which has an original training process, has been developed as part of a project in the field of computer aided diagnosis. The aim of this work is to analyse medical images to recognise an abnormal region of an organ. In contrast to other methods, generating information of the abnormality's level is part of the recognition stage. Moreover, the whole process is independent of the particular disease. The neuron was tested using lung images taken by a gamma camera.

Real time microcontroller implementation of an adaptive myoelectric filter.

This paper describes a real time digital adaptive filter for processing myoelectric signals. The filter time constant is automatically selected by the adaptation algorithm, giving a significant improvement over linear filters for estimating the muscle force and controlling a prosthetic device. Interference from mains sources often produces problems for myoelectric processing, and so 50 Hz and all harmonic frequencies are reduced by an averaging filter and differential process. This makes practical electrode placement and contact less critical and time consuming. An economic real time implementation is essential for a prosthetic controller, and this is achieved using an Intel 80C196KC microcontroller.

A portable system for closed loop control of the paralysed hand using functional electrical stimulation.

A portable and closed-loop system is described for the paralysed hand using transcutaneous electrical stimulation. It is implemented using a modest microprocessor which receives data from force sensors mounted in a glove on the users hand. A display shows parameter values and a menu for the user to sequentially select controller states. For the grip state, the control loop is basically proportional plus a two stage integral response (gain adaptation). Eight channels can be accommodated in the stimulator. The system was evaluated with the help of a tetraplegic who managed to hold everyday objects in a stable grip.

A method for the extraction of an object from a noisy background.

The removal of the background from a noisy image to leave the object of interest, with well defined edges, is a difficult task. Images obtained using radioisotopes have low signal-to-noise ratios due to scattered photons, as well as emitted radiation from the background. Moreover, noise is, also, a consequence of the low number of detected photons. A scan of a row or column of such an image demonstrates that the pixels do not change value rapidly near the edge of the object. In addition, clusters of pixels, which can be found outside the edges of the object and in the background, can have higher values than those in the object. This effect is worse in abnormal images, where the abnormal clusters may have values as low as those of the noisy clusters. An image processing technique has been developed to determine the object edges. It is part of a research project in the field of the computer aided diagnosis, which involves artificial neural networks. It makes use of the so-called 'moving window operations' which are very common in digital image processing. The technique was tested using male lung images that were taken by a gamma camera.

The Southampton Hand: an intelligent myoelectric prosthesis.

The form of the control and structure of the mechanism of an artificial hand are important factors which tend to dictate the prosthesis' level of use. Conventional prostheses are simple devices with limited functional range and a control format that requires high levels of user concentration for successful operation. The Southampton Adaptive Manipulation Scheme (SAMS) is a hierarchical control format that allows a larger number of independent motions to be controlled while requiring a smaller degree of user input. The SAMS control has been applied to different hand mechanisms, both custom-made and modified commercial systems. Their application with users shows them to have a performance on a par with, or superior to, other conventional devices. The form of prosthesis control is reviewed and the development of, and clinical experiments with, the Southampton Hand are outlined.

Intelligent multifunction myoelectric control of hand prostheses.

Intuitive myoelectric prosthesis control is difficult to achieve due to the absence of proprioceptive feedback, which forces the user to monitor grip pressure by visual information. Existing myoelectric hand prostheses form a single degree of freedom pincer motion that inhibits the stable prehension of a range of objects. Multi-axis hands may address this lack of functionality, but as with multifunction devices in general, serve to increase the cognitive burden on the user. Intelligent hierarchical control of multiple degree-of-freedom hand prostheses has been used to reduce the need for visual feedback by automating the grasping process. This paper presents a hybrid controller that has been developed to enable different prehensile functions to be initiated directly from the user's myoelectric signal. A digital signal processor (DSP) regulates the grip pressure of a new six-degree-of-freedom hand prosthesis thereby ensuring secure prehension without continuous visual feedback.

A clinical experience with a hierarchically controlled myoelectric hand prosthesis with vibro-tactile feedback.

UNLABELLED: Improved performance of externally powered myoelectric hands is possible when the direct control of the digit flexion and grip force are given over to an electronic controller which frees the operator to concentrate on other demands. DESIGN: A commercial myoelectric hand was modified to take the new touch and slip sensors and novel control method. SUBJECT: An adult male with a traumatic mid-forearm amputation. OUTCOME MEASURE: The range and ease of use of the prosthetics system. RESULT: The hand was easily and usefully operated in the home and work environment. CONCLUSION: Hierarchical control of a hand is possible using sensory feedback to a sophisticated electronic controller. Such a control method reduces the demands on the user's concentration and enhances the hand's range.

Measuring scapular kinematics during arm lowering using the acromion marker cluster.

The aim of the present study was to examine the acromion marker cluster (AMC) method of measuring scapular kinematics during the arm lowering, eccentric, phase. Twenty six participants completed arm elevation and lowering in the sagittal, frontal and scapular plane. The participants held their arm at 30° increments while the orientation of the scapula was recorded using an AMC and a scapular locator (SL). There were no significant differences between the AMC and SL during the lowering phase for sagittal and scapular plane arm movements. The AMC significantly underestimated upward rotation (max RMSE = 6.0°), and significantly overestimated posterior tilt (max RMSE = 7.2°) during arm lowering in the frontal plane. The reported root mean square errors, however, were within the ranges observed during the elevation phase and reported in previous literature. The AMC therefore provides a reasonable description of scapular kinematics during the arm lowering phase.

Making sense of artificial hands.

A review of sensors for artificial hands is presented in terms of their range, specifications and characteristics. There is a growing need for sensors due to the development of prosthetic hands that have multiple degrees of freedom requiring finger coordination into different postures. The sensing of force, position (angle), object-slip and temperature allows for the control of these hands automatically and frees the user from cognitive burden. To make the best possible use of individual sensing elements, future controllers will need to combine data from different types of sensor. They may also have an integral power supply using a small battery or harvest energy from their environment and transmit data wirelessly.

Constant angular velocity of the wrist during the lifting of a sphere.

The primary objective of the experiments was to investigate the wrist motion of a person while they were carrying out a prehensile task from a clinical hand function test. A six-camera movement system was used to observe the wrist motion of 10 participants. A very light sphere and a heavy sphere were used in the experiments to study any mass effects. While seated at a table, a participant moved a sphere over a small obstacle using their dominant hand. The participants were observed to move their wrist at a constant angular velocity. This phenomenon has not been reported previously. Theoretically, the muscles of the wrist provide an impulse of force at the start of the rotation while the forearm maintains a constant vertical force on a sphere. Light-heavy mean differences for the velocities, absolute velocities, angles and times taken showed no significant differences (p = 0.05).

Shoulder and elbow muscle activity during fully supported trajectory tracking in people who have had a stroke.

An inability to perform tasks involving reaching is a common problem for stroke patients. This paper provides an insight into mechanisms associated with recovery of upper limb function by examining how stroke participants' upper limb muscle activation patterns differ from those of neurologically intact participants, and how they change in response to an intervention. In this study, five chronic stroke participants undertook nine tracking tasks in which trajectory (orientation and length), speed and resistance to movement were varied. During these tasks, EMG signals were recorded from triceps, biceps, anterior deltoid, upper, middle and lower trapezius and pectoralis major. Data collection was performed in sessions both before, and after, an intervention in which participants performed a similar range of tracking tasks with the addition of responsive electrical stimulation applied to their triceps muscle. The intervention consisted of eighteen one hour treatment sessions, with two participants attending an additional seven sessions. During all sessions, each participant's arm was supported by a hinged arm-holder which constrained their hand to move in a two dimensional plane. Analysis of the pre intervention EMG data showed that timing and amplitude of peak EMG activity for all stroke participants differed from neurologically intact participants. Analysis of post intervention EMG data revealed that statistically significant changes in these quantities had occurred towards those of neurologically intact participants.

Surface EMG pattern analysis of the wrist muscles at different speeds of contraction.

The aim of this study is to investigate the characteristics of surface electromyographic signals, particularly in pattern analysis. The data were collected from the wrist muscles (flexor carpi ulnaris and extensor carpi radialis) of 20 healthy participants. The study focuses on the movement of the wrist muscles at different frequencies. Participants were asked to contract their muscles at four different speeds (60, 90 and 120 cycles a minute and maximum speed) during wrist flexion and extension, co-contraction and isometric contraction. In this work, moving approximate entropy, mean absolute value and kurtosis are evaluated from the surface electromyographic signals at the four speeds. Moving approximate entropy and kurtosis analysis show that there are significant differences at three states of contraction; start, middle and end. It is shown that there are more regular data in a surface electromyographic signal at the beginning and end of a muscle contraction with low regularity during the middle part.

Shoulder and elbow muscle activity during fully supported trajectory tracking in neurologically intact older people.

An inability to perform tasks involving reaching is a common problem for stroke patients. Knowledge of normal muscle activation patterns during these tasks is essential to the identification of abnormal patterns in post-stroke hemiplegia. Findings will provide insight into changes in muscle activation patterns associated with recovery of upper limb function. In this study with neurologically intact participants the co-ordination of shoulder and elbow muscle activity during two dimensional reaching tasks is explored. Eight participants undertook nine tracking tasks in which trajectory (orientation and length), duration, speed and resistance to movement were varied. The participants' forearm was supported using a hinged arm-holder, which constrained their hand to move in a two dimensional plane. EMG signals were recorded from triceps, biceps, anterior deltoid, upper, middle and lower trapezius and pectoralis major. A wide variation in muscle activation patterns, in terms of timing and amplitude, was observed between participants performing the same task. EMG amplitude increased significantly with length, duration and resistance of the task for all muscles except anterior deltoid. Co-activation between biceps and triceps was significantly dependent on both task and trajectory orientation. Activation pattern of pectoralis major was dependent on trajectory. Neither trajectory orientation nor task condition affected the activation pattern of anterior deltoid. Normal ranges of timing of muscle activity during the tasks were identified.