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Papers by Brian Andrews

Neuromodulation: Technology at the Neural Interface

2022 44th Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)

Computational methods of determining the response of neural tissue to electrical stimulation have... more Computational methods of determining the response of neural tissue to electrical stimulation have demonstrated value for the development of novel devices and the programming of neuromodulation therapies. Detailed biophysical models are excessively computationally intensive for many applications; simple metrics to approximate activation can speed up progress in this area. The activating function provides such a useful metric. However, this measure, defined for a specific axon orientation, is not immediately applicable to computed electric fields to assess their effects. We demonstrate a method for computation of the activating function generalized to a field in order to allow rapid computation of the effects of stimulation on neural tissue while preserving information on axon orientation. Clinical Relevance-This demonstrates a useful method of approximating the effect of electrical stimulation on nervous tissue for the development of devices and the optimization of parameters for electrical neuromodulation.

Dynamic Systems and Control, 1998

To gain insight into the way paraplegic subjects voluntarily control their arms during the FES as... more To gain insight into the way paraplegic subjects voluntarily control their arms during the FES assisted standing-up, we developed a neural network model to predict the arm forces. The training data were collected from eight paraplegic subjects during the FES-assisted standing-up and divided into two categories for training and validation. In all the cases, it was possible to develop models that followed closely the observed behavior of the subjects. The test on validation data showed that the models could generalize well to the unseen situations. It also proved that each subject has developed a unique voluntary control strategy, which is consistent. The subjects with more experience in the use of FES were more consistent in the use of their arms from trial to trial when compared to older, heavier or high lesion subjects. Comparison of the models in different subjects showed that in addition to the unique features adopted by each subject, there are also general rules that are common ...

Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology

ABSTRACT

Converging Clinical and Engineering Research on Neurorehabilitation III, 2018

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Proceedings of 16th Annual International Conference of the IEEE Engineering in Medicine and Biology Society

An adaptive fuzzy logic controller (FLC), based on a trainable network structure, is designed for... more An adaptive fuzzy logic controller (FLC), based on a trainable network structure, is designed for functional electrical stimulation (FES) control. A prior expert knowledge can be incorporated as fuzzy IF-THEN rules. An online reinforcement learning algorithm is employed for learning optimal control rules or fine-tuning the existing control rules. This adaptive FLC is applied to a computer model of swing leg and demonstrates its on-line learning ability.<<ETX>>

Osteoporosis after spinal cord injury is associated with low-trauma fractures, and consequently w... more Osteoporosis after spinal cord injury is associated with low-trauma fractures, and consequently with increased risk of morbidity and mortality. The loss of bone mass density (BMD) due to paraplegia can be reduced through cyclical electrically-induced muscle contractions. Here we propose an FES control system based on posture switching, that induces transient loading of the lower limbs during a set of standing postures. This aims to produce an increased, evenly distributed BMD, whilst minimising FES-induced muscle fatigue. Here we describe the design and assessment of the FES exercising platform, comprising a controllable multi-channel electrical stimulator and an instrumented standing frame. The platform supports standing and postural shifting, provides real-time human-in-the-loop FES control with on-line feedback to the user. The platforms is used to investigate the effect of regular exercise on the distribution of BMD in people with paraplegia.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1988

A control methodology for functional electrical stimulation (FES) is introduced. It integrates as... more A control methodology for functional electrical stimulation (FES) is introduced. It integrates aspects of finite-state-machine theory and the artificial-intelligence techniques of decision-rule derivation by induction with an implementation based on the methods of firmware transitional logic (FTL). This system represents an advance over previous rule-based FES control systems, which used hand-crafted rules. The theory underlying the methodology is presented with an example demonstrating rule derivation from a large collection of examples. Possible implementation in FTL is discussed together with the benefits of this control system to FES, which include exhaustive predictability, high operating speed, and constructional compactness.<<ETX>>

Habituation of the withdrawal reflex can significantly limit the application of surface FES in ga... more Habituation of the withdrawal reflex can significantly limit the application of surface FES in gait restoration. Recent results of animal research indicate that C-fibre excitation can potentiate and dishabituate flexion reflexes for prolonged periods. We report preliminary results using high intensity stimuli applied to the common peroneal nerve in four spinal cord injured patients. Functionally useful potentiation and dishabituation of the flexion withdrawal reflex was observed in three cases. The dishabituating stimuli alone did not produced any leg movement. The dishabituation lasted for periods up to 30 seconds and flare responses were confined to areas of skin around the cathode. The effect could be repeated once the reflex was again habituated. We also report a one-step-ahead FES controller that utilised the dishabituating stimuli. In preliminary tests with two patients in which the reflex was elicited at 2s intervals peak hfp flexion was regularised about a constant level in ...

INTRODUCTION Musculoskeletal simulation software packages and model repositories have broadened t... more INTRODUCTION Musculoskeletal simulation software packages and model repositories have broadened the user base able to perform musculoskeletal analysis and have facilitated in the sharing and distribution of musculoskeletal models. As musculoskeletal modeling continues to become more utilized as an engineering tool, the consistency in results derived from different models and simulation software is becoming more critical. Understanding the absolute and potential trend differences that may result as a function of model selection is essential, especially considering users rarely have the opportunity to duplicate a particular analysis with different generic models or software. The purpose of this study was to compare eight musculoskeletal models, from three modeling packages, and evaluate differences in muscle moment arm lengths.

It is well recognised that long-term indwelling Foley catheters are associated with significant m... more It is well recognised that long-term indwelling Foley catheters are associated with significant morbidity. External collection devices have a poor cosmetic appearance and negatively impact on patients’ self-image and dignity. The use of catheterisable gastrostomy devices, sometimes referred to as ‘buttons’ have been reported for bladder drainage in children as well as adults with areflexic bladders (1)(2). We propose the use of a ‘Bladder Button’ based on the design of this device in combination with neuromodulation or pharmacotherapy for the long-term management of neurogenic detrusor overactivity (3). The aim of this study is to determine if the gastrostomy button can be used for intermittent bladder drainage in adult participants with neurogenic detrusor overactivity.

Functional electrical stimulation (FES) assisted indoor rowing provides exercise for adults with ... more Functional electrical stimulation (FES) assisted indoor rowing provides exercise for adults with spinal cord injury, promoting cardiovascular fitness and the development of muscle mass in all extremities. Modifications to a standard rowing machine provide mechanical stabilisation for the trunk while constraining the legs to move in a sagittal plane over the correct range of motion. Bi-phasic pulses applied through surface electrodes stimulate the quadriceps muscles during the drive phase of rowing. The hamstrings, gastrocnemius and pretibial muscles are stimulated during the recovery phase. Stimulation is controlled so as to maximise power output without causing excessive fatigue. The technique may be acquired in a few sessions and has been demonstrated competitively.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society Volume 13: 1991, 1991

Computer Methods in Biomechanics and Biomedical Engineering, 2020

The purpose of this study is to determine the tibiofemoral forces during functional electrical st... more The purpose of this study is to determine the tibiofemoral forces during functional electrical stimulation (FES) rowing in individuals with spinal cord injury (SCI). We analysed the motion of five participants with SCI during FES rowing, with simultaneous measurements of (i) three-dimensional marker trajectories, (ii) foot reaction forces (FRFs), (iii) ergometer handle forces, and (iv) timestamps for electrical stimulation of the quadriceps and hamstrings muscles. We created full-body musculoskeletal models in OpenSim to determine subject-specific tibiofemoral forces during FES rowing. The peak magnitudes of tibiofemoral forces averaged over five participants with SCI were 2.43 ± 0.39 BW and 2.25 ± 0.71 BW for the left and right legs, respectively. The peak magnitudes of FRFs were 0.19 ± 0.04 BW in each leg. The peak magnitude of handle forces was 0.47 ± 0.19 BW. Peak tibiofemoral force was associated with peak FRF (magnitudes, R 2 ¼ 0.56, p ¼ 0.013) and peak handle force (magnitudes, R 2 ¼ 0.54, p ¼ 0.016). The ratios of peak magnitude of tibiofemoral force to peak magnitude of FRF were 12.9 ± 1.9 (left) and 11.6 ± 2.4 (right), and to peak magnitude of handle force were 5.7 ± 2.3 (left) and 4.9 ± 0.9 (right). This work lays the foundation for developing a direct exercise intensity metric for bone mechanical stimulus at the knee during rehabilitation exercises. Clinical Significance: Knowledge of tibiofemoral forces from exercises such as FES rowing may provide clinicians the ability to personalize rehabilitation protocols to ensure that an SCI patient is receiving the minimum dose of mechanical stimulus necessary to maintain bone health.

Sensors, 2020

The transcutaneous stimulation of lower limb muscles during indoor rowing (FES Rowing) has led to... more The transcutaneous stimulation of lower limb muscles during indoor rowing (FES Rowing) has led to a new sport and recreation and significantly increased health benefits in paraplegia. Stimulation is often delivered to quadriceps and hamstrings; this muscle selection seems based on intuition and not biomechanics and is likely suboptimal. Here, we sample surface EMGs from 20 elite rowers to assess which, when, and how muscles are activated during indoor rowing. From EMG amplitude we specifically quantified the onset of activation and silencing, the duration of activity and how similarly soleus, gastrocnemius medialis, tibialis anterior, rectus femoris, vastus lateralis and medialis, semitendinosus, and biceps femoris muscles were activated between limbs. Current results revealed that the eight muscles tested were recruited during rowing, at different instants and for different durations. Rectus and biceps femoris were respectively active for the longest and briefest periods. Tibialis ...

The Journal of Spinal Cord Medicine, 2018

Objective: To determine the effect of a functional electrical stimulation (FES) rowing program on... more Objective: To determine the effect of a functional electrical stimulation (FES) rowing program on bone mineral density (BMD) when implemented within two years after SCI. Design: Prospective. Setting: Health Care Facility. Participants: Convenience sample; four adults with recent (<2 years) traumatic, motor complete SCI (C7-T12 AIS A-B). Intervention: A 90-session FES rowing exercise program; participants attended 30-minute FES training sessions approximately three times each week for the duration of their participation. Outcome Measures: BMD in the distal femur and tibia were measured using peripheral Quantitative Computed Tomography (pQCT) at enrollment (T 0) and after 30 (T 1), 60 (T 2), and 90 (T 3) sessions. Bone stimulus was calculated for each rower at each time point using the average number of weekly loading cycles, peak foot reaction force, and bone mineral content from the previous time point. A regression analysis was used to determine the relationship between calculated bone stimulus and change in femoral trabecular BMD between time points. Results: Trabecular BMD in the femur and tibia decreased for all participants in T 0-1 , but the rate of loss slowed or reversed between T 1-2 , with little-to-no bone loss for most participants during T 2-3. The calculated bone stimulus was significantly correlated with change in femoral trabecular BMD (P = 0.016; R 2 = 0.458). Conclusion: Consistent participation in an FES rowing program provides sufficient forces and loading cycles to reduce or reverse expected bone loss at the distal femur and tibia, at least temporarily, in some individuals within two years after SCI. Trial Registration: NCT02008149.

IEEE Transactions on Rehabilitation Engineering, 2000

Rule based detectors were used with a single cluster of accelerometers attached to the shank for ... more Rule based detectors were used with a single cluster of accelerometers attached to the shank for the real time detection of the main phases of normal gait during walking. The gait phase detectors were synthesized from two rule induction algorithms, Rough Sets (RS) and Adaptive Logic Networks (ALNs), and compared with to a previously reported stance/swing detector based on a hand crafted, rule based algorithm. Data was sampled at 100 Hz and the detection errors determined at each sample for 50 steps. For three able bodied subjects, the sample by sample accuracy of stance/swing detection ranged within 94-97%, 87-94%, and 87-95% for the RS, ALN, and the handcrafted methods, respectively. A heuristically formulated postdetector filter improved the RS and ALN detectors' accuracy to 98%. RS and ALN also detected five gait phases to an overall accuracy of 82-89% and 86-91%, respectively. The postdetector filter localized the errors to the phase transitions, but did not change the detection accuracy. The average duration of the error at each transition was 40 ms and 23 ms for RS and ALN, respectively. When implemented on a microcontroller, the RS-based detector executed ten times faster and required one tenth of the memory than the ALN-based detector.

Journal of the Society of Biomechanisms, 1990