Ian David Underhill

Design of a high-sensor count fibre optic manometry catheter for in-vivo colonic diagnostics

The design of a fibre Bragg grating based manometry catheter for in-vivo diagnostics in the human colon is presented. The design is based on a device initially developed for use in the oesophagus, but in this instance, longer sensing lengths and increased flexibility were required to facilitate colonoscopic placement of the device and to allow access to the convoluted regions of this complex organ. The catheter design adopted allows the number of sensing regions to be increased to cover extended lengths of the colon whilst maintaining high flexibility and the close axial spacing necessary to accurately record pertinent features of peristalsis. Catheters with 72 sensing regions with an axial spacing of 1 cm have been assembled and used in-vivo to record peristaltic contractions in the human colon over a 24hr period. The close axial spacing of the pressure sensors has, for the first time, identified the complex nature of propagating sequences in both antegrade (towards the anus) and retrograde (away from the anus) directions in the colon. The potential to miss propagating sequences at wider sensor spacings is discussed and the resultant need for close axial spacing of sensors is proposed.

In-vivo demonstration of a high resolution optical fiber manometry catheter for diagnosis of gastrointestinal motility disorders

Fiber optic catheters for the diagnosis of gastrointestinal motility disorders are demonstrated in-vitro and in-vivo. Single element catheters have been verified against existing solid state catheters and a multi-element catheter has been demonstrated for localized and full esophageal monitoring. The multi-element catheter consists of a series of closely spaced pressure sensors that pick up the peristaltic wave traveling along the gastrointestinal (GI) tract. The sensors are spaced on a 10 mm pitch allowing a full interpolated image of intraluminal pressure to be generated. Details are given of in-vivo trials of a 32-element catheter in the human oesophagus and the suitability of similar catheters for clinical evaluation in other regions of the human digestive tract is discussed. The fiber optic catheter is significantly smaller and more flexible than similar commercially available devices making intubation easier and improving patient tolerance during diagnostic procedures.

Deterministic control of thin film thickness in physical vapor deposition systems using a multi-aperture mask

A technique for controlling the thickness profile of a thin film in physical vapor deposition systems is reported. The technique uses a novel mask design with apertures of varying dimension to selectively deposit the required film thickness at predetermined locations across the aperture of the substrate. The technique has been used to correct the thickness uniformity of a 55 mm diameter, 280 microm thick, lithium niobate wafer to less than 0.5 nm rms, and also to improve the uniformity of deposited films in an Ion Beam Sputtering system to better than 0.5% over a 50 mm aperture.

A fibre optic catheter for simultaneous measurement of longitudinal and circumferential muscular activity in the gastrointestinal tract

Diagnostic catheters based on fibre Bragg gratings (FBGs) are proving to be highly effective for measurement of the muscular activity associated with motility in the human gut. While the primary muscular contractions that generate peristalsis are circumferential in nature, it has long been known that there is also a component of longitudinal contractility present, acting in harmony with the circumferential component to improve the overall efficiency of material movement. We report the detection of longitudinal motion in mammalian intestine using an FBG technique that should be viable for similar detection in humans. The longitudinal sensors have been combined with our previously reported FBG pressure sensing elements to form a composite catheter that allows the relative phase between the two components to be detected. The catheter output has been validated using video mapping in an ex-vivo rabbit ileum preparation.

Measurement of Muscular Activity Associated With Peristalsis in the Human Gut Using Fiber Bragg Grating Arrays

Diagnostic catheters based on fiber Bragg gratings (FBGs) are proving to be highly effective for measurement of the muscular activity associated with peristalsis in the human gut. The primary muscular contractions that generate peristalsis are circumferential in nature; however, it has long been known that there is also a component of longitudinal contractility present, acting in harmony with the circumferential component to improve the overall efficiency of material movement. While detection of the circumferential contractions has been possible using solid state, hydraulic, and pneumatic sensor arrays in the oesophagus and anorectum, there have been relatively few reports on the measurement or inference of longitudinal contractions in humans. This is partly due to the lack of a viable recording technique suitable for real-time in-vivo measurement of this type of activity over extended lengths of the gut. We report on the development of, and latest results from, catheter based sensors capable of detecting both forms of muscular activity. Results from validation trials of both circumferential and longitudinal FBG catheters during simultaneous recording and video analysis in lengths of excised mammalian colon are given. Preliminary data from human clinical trials in patients with functional gastrointestinal disorders of the colon are also presented demonstrating the ability of the fiber optic catheter technology to provide high resolution data from the complex and convoluted regions of the human gut below the stomach.

Structural Veneer Based Composite Products from Hardwood Thinning – Part I: Background and Manufacturing

In Australia, plantation forests have increased in area by around 50% in the last 10 years. While this expansion has seen a modest 8% increase for softwoods, hardwood plantations have dramatically increased by over 150%. Hardwood plantations grown for high quality sawn timber are slow to mature, with a crop rotation time potentially reaching 35 years. With this long lead-time, each year the risk from fire, pests and adverse weather events dramatically increases, while not translating into substantially higher financial returns to the grower. To justify continued expansion of Australia’s current hardwood plantation estate, it is becoming necessary to develop higher value end-uses for both pulpwood and smaller ‘sawlog’ resources. The use of the low commercial value stems currently culled during thinning appears to be a necessary option to improve the industry profitability and win new markets. This paper provides background information on Australian forests and plantations and gives an overview of potential uses of Australian hardwood plantation thinning logs, as their mechanical properties. More specifically, this paper reports on the development of structural Veneer Based Composite (VBC) products from hardwood plantation thinning logs, taking advantage of a recent technology developed to optimise the processing of this resource. The process used to manufacture a range of hollow-form veneer laminated structural products is presented and the mechanical characteristics of these products are investigated in the companion paper. The market applications and future opportunities for the proposed products are also discussed, as potential benefits to the timber industry.

The use of wavelength division multiplexed fiber Bragg grating sensors for distributed sensing of pressure in the gastrointestinal tract

The design and clinical performance of fiber Bragg grating based pressure sensing catheters for the diagnosis of gastrointestinal motility disorders are presented. The fiber optic design allows catheters with multiple sensing regions but small overall diameters to be fabricated, which is advantageous for nasal intubation into patients. The fiber optic catheters have been compared to a commercially available solid-state device both in-vitro and in-vivo, and results demonstrate that they are suitable for diagnosis of gastrointestinal motility disorders.

Fiber Optic Pressure Sensing Arrays for Monitoring Horizontal and Vertical Pressures Generated by Traveling Water Waves

Distributed pressure sensing arrays fabricated from fiber Bragg gratings have been demonstrated for real-time monitoring of the dynamic subsurface pressures beneath water waves in a wave tank. Two sensing arrays were used to monitor horizontal and vertical pressures in the tank as periodic wave trains passed overhead. The horizontal and vertical arrays contained 90 and 35 sensing elements, respectively, spaced at 1-cm intervals allowing highly accurate spatial resolution to be achieved in both orientations. The wave tank paddle was programmed to generate wave-trains varying from ~5 to 30-cm peak-to-trough and the pressures measured using the fiber optic array were validated using commercial piezo-electric pressure sensors and video image analysis. The length and sensor separation of the fiber optic sensing array can be varied to suit the location under test, and the fiber optic elements make the devices inherently resistant to corrosion and electromagnetic interference.

A fibre Bragg grating manometry catheter for in-vivo diagnostics of swallowing disorders

Fibre Bragg grating based pressure sensing catheters for the diagnosis of gastrointestinal motility disorders are presented. These catheters have been successfully trialled under controlled clinical conditions and results from in-vivo trials are given.

Structural Veneer Based Composite Products from Hardwood Thinning - Part II: Testing of Hollow Utility Poles

Australian utility pole network is aging and reaching its end of life, with 70% of the 5 million poles currently in-service nationally installed within the 20 years following the end of World War II. The estimated investment required for the replacement or remedial maintenance of the aging 3.5 millions poles is as high as 1.75 billion dollars. Additionally, an estimated 21,700 high-durability new poles are required each year, representing further investment of 13.5 million dollars per year. Yet, agreements which progressively phase out logging of native forests around Australia have been signed, giving the industry about 25 years to make the transition from Crown native forests to plantations and private forests. As utility poles were traditionally cut from native forest hardwood species, finding solutions to source new poles currently presents a challenge. This paper presents tests on Veneer Based Composite hardwood hollow utility poles manufactured from Gympie messmate (Eucalyptus cloeziana) plantation thinning. Small diameter poles of nominal 115 mm internal diameter and 15 mm wall-thickness were manufactured in two half-poles butt jointed together, using 9 veneers per halfpole. The poles were tested in bending and shear, and experimental test results are presented. The mechanical performance of the hollow poles is discussed and compared to hardwood poles cut from mature trees and of similar size. Future research and different options for improving the current concept are proposed in order to provide a more reliable and cost effective technical solution to the current shortage of utility poles.