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Auckland, New Zealand

Anderson A.J.,Auckland Bioengineering Institute
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference

A preliminary investigation was performed into the viability of using frequency domain image processing techniques to determine sarcomere length from bright-field images of isolated cardiac trabecula in real-time. Hardware based data processing was used to compute the average sarcomere length in a cardiac trabecula undergoing stretch. Our technique estimated the increase in mean sarcomere length with increasing muscle length as the trabecula was stretched to and beyond the normal physiological limit of 2.4 μm. The standard error in the mean sarcomere length extracted from each image was typically10 nm. Source

Kruger J.A.,Auckland Bioengineering Institute | Heap S.W.,University of Auckland | Murphy B.A.,University of Ontario Institute of Technology | Dietz H.P.,University of Sydney
Ultrasound in Obstetrics and Gynecology

Objective To clarify whether the 'plane of minimal dimensions' of the levator hiatus on three-dimensional (3D) ultrasound accurately represents the minimal anatomical transverse hiatal dimension during a Valsalva maneuver. Methods In this retrospective study of 3D transperineal ultrasound and magnetic resonance (MR) imaging, datasets from 19 female participants were used to measure the transverse diameter of the levator hiatus using the plane of minimal dimensions on maximum Valsalva maneuver. The term 'apparent minimal transverse diameter' (aMTD) was used to define the transverse diameter measured using axial ultrasound and comparable axial or coronal MR images. Coronal MR images, using the plane of the vagina as a reference, were also obtained on maximum Valsalva. The transverse diameter measured between the caudal margin of the pubococcygeus/puborectalis on the MR coronal image is denoted by the term 'true minimal transverse diameter' (tMTD). Statistical comparisons between the aMTD and tMTD were made using Student's t-test. Results No significant difference was demonstrated between the aMTD as measured by ultrasonography and MRI. However, there were significant differences found between the aMTD measured by both ultrasound and MRI and the tMTD measured on coronal MR images (both P < 0.01), with mean (± SD) values of 4.36 ± 0.85, 4.13 ± 1.09 and 3.23 ± 0.49 cm, respectively. Conclusion This study highlights the complexity and 3D nature of the levator hiatus and pelvic floor muscles. Investigators have previously assumed that the plane of minimal dimensions of the hiatus can be measured in a flat plane, however, the 3D nature of the hiatus means that the true levator hiatus occupies a warped (non-Euclidean) plane. Hiatal measurements on Valsalva may be subject to systematic error if performed in a single section, i.e. using a flat (Euclidean) plane. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd. Source

Dirven S.,University of Auckland | Xu W.,University of Auckland | Cheng L.K.,Auckland Bioengineering Institute
IEEE/ASME Transactions on Mechatronics

In order to understand fluid transport throughout esophageal swallowing in man, a biologically inspired soft-robotic peristaltic actuator has been designed and manufactured to perform biomimetic swallowing. To achieve congruence with current mathematical modeling techniques for esophageal peristalsis, this paper examines the capability of the device (empirical) towards achieving sinusoidal transport waves with variations of clinically significant parameters such as amplitude and wavelength. The performance of the device to fit the commanded trajectory, by minimization of mean squared error, is tested over the range of wavefront length 30 ≤λ/2 ≤ 60 mm and amplitude 6-8 mm in a two-dimensional capability analysis. It is found that the device is capable of achieving propagation of families of wave shapes with less than 5% full scale mean error, which improves for increasing wavefront length and reducing amplitude. The aim for the device in the future is to inspire a novel rheometric technique in the physical domain which characterizes fluid formulations based on intrabolus pressure signatures. This analysis expresses the trajectory generation technique and performance of the novel device to produce continuous peristaltic waves towards biomimetic swallowing. © 1996-2012 IEEE. Source

Steinke H.,University of Leipzig | Lingslebe U.,Leipzig University of Applied Sciences | Bohme J.,University of Leipzig | Slowik V.,Leipzig University of Applied Sciences | And 3 more authors.
Medical Engineering and Physics

Background and objective: The iliotibial tract (tract) is an important structure for the biomechanics of both the hip and knee joint. While a detailed characterization of its mechanical properties might help to better understand its specific role in the load transfer from the pelvis to femur and tibia, determination of those properties is complicated by its particular structure of thin fibers in the fresh state. Moreover, although the tracts mechanical properties are often derived from cadaveric material chemically fixed with either ethanol or formaldehyde, the influence of such fixation methods remains to be elucidated. Aim of this study was to determine Young's modulus (tensile modulus, YM) of the tract. We hypothesized that either ethanol or formaldehyde fixation would significantly increase the YM compared to the tracts condition in a fresh state. Material and methods: 13 specimens of tract were gained from donators. The ends of the probes were plastinated with resin creating a sharp interface between the clamp and the probe to prevent material slippage. The specimens were measured in their fresh state, under ethanol- and formaldehyde-fixed conditions and re-measured after rinsing with tap water. Results: The YM of the fresh probes averaged 397.3N/mm2 with a standard deviation (SD) of 151.5N/mm2. The YM of the ethanol-fixed specimens was significantly higher (673.2N/mm2, SD 328.5N/mm2, p<0.05). After rinsing with tap water, the YM decreased to 95% of the fresh condition value (377.4N/mm2, SD 144.5N/mm2, non-significant change from fresh). After formaldehyde fixation, the YM reached 490.3N/mm2 (SD 143.0N/mm2, p<0.05). When the formaldehyde-fixed specimens were rinsed, the YM was 114% of the value of the fresh condition (452.6N/mm2, SD 115.1N/mm2, non-significant change from fresh). Conclusions: This study found a significant influence of the chemical fixation method on the YM of the IT tract. If such fixation is required, our results suggest using a treatment with ethanol and subsequent rinsing that results in minimal changes to the tracts YM. Furthermore, plastination of the ends of the specimens could be crucial to allow in vitro determination of valid YM of ligaments data that can then be integrated with confidence in further finite element analyses. © 2011 IPEM. Source

Anderson I.A.,Auckland Bioengineering Institute | Anderson I.A.,University of Auckland | Ieropoulos I.A.,Bristol Robotics Laboratory | McKay T.,Auckland Bioengineering Institute | And 2 more authors.
IEEE/ASME Transactions on Mechatronics

Artificial muscles based on the dielectric elastomer actuator (DEA) are an attractive technology for autonomous robotic systems. We are currently exploring their use on EcoBot (Ecological roBot), an autonomous robot being developed by Bristol Robotics Lab that uses microbial fuel cells (MFCs). DEA will provide actuators for fuel cell maintenance and other goals and will increase active mission time through greater mechanical efficiency and reduced mass. Artificial muscles use high voltages and running them normally requires voltage converters to boost the voltage on delivered charge several hundred times. A dielectric elastomer generator (DEG) when used with a recently developed self-priming circuit (SPC) can supply the high-voltage power directly to artificial muscle systems. The SPC can also be started using an initial low-voltage charge from another energy harvester such as a bank of MFCs or a solar cell array. This combination could lead to a completely autonomous power source for robotic artificial muscles. We demonstrate a proof-of-concept portable self-primed DEG for harvesting wind energy from moving tree branches. © 2006 IEEE. Source

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