Centre for Medical Science &Technology Optical Developments in Medical Engineering Prof. P.J. Bryanston-Cross Presentation of research interests Belfast.

Centre for Medical Science Centre for Medical Science &Technology &Technology

Optical Developments in Medical Optical Developments in Medical EngineeringEngineering

Prof. P.J. Bryanston-CrossProf. P.J. Bryanston-Cross

Presentation of research interestsPresentation of research interests

Belfast 2001Belfast 2001 4:30pm, Friday 144:30pm, Friday 14thth September September

A series of Optical & Medical Engineering innovations have been developed through the interaction between Engineering, Computer and Medical Sciences.

In particular there are areas of exchange between medical instrumentation and aerospace science, which promise to create new types of intelligent optical diagnostic technology.

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Synthetic intelligence is gaining use in optical diagnostics.

• low cost processing power

• allowing for highly sophisticated signal processing software

• hardware programmed into embedded systems

Example: solving highly complex image connectivity problems.

Synthetic Intelligence

Application of Fuzzy Logic

in Fluid Dynamics

Raw PIV particle Image Processed Velocity Map of the Flow

Opera Singer

Holographic Interferometry

The movement in the face has been contoured using holographic interferometry.

The fringe spacing represents a movement of 30 m and was created by two pulses from a ruby laser.

Optical system:

Developed for delivering a high power ‘Q’ switched laser beam into a gas turbine engine at MIT to visualise airflows.

The probe exit beam diameter was 4 mm delivering a 200 mJ laser

pulse in 10 ns.

Similar construction has been developed for application to surgery.

Miniature Instrumentation

Medical Applications

•Fundus Camera Technology

•Tonometer

•Diabetes probe

•Vitrectomy

The resolution must be a minimum of 10 line pairs/mm.

The colour contrast must be calibrated.

The colour balance must be compared to a stored standard.

The pixel integrity/optical cleanliness of the system must be checked, on both the camera and the monitors used.

The camera test should be carried out under the same conditions weekly.

A flat resolution test chart can be used to evaluate the camera

Fundus Camera

Active Non-Contacting Diabetes Probe

• 1 Year of research and the subject of a DTI Smart Award.

• Design and implementation of a low cost, on-line, non-contact, spectral testing device to be used as a Diabetes Probe.

Diagnostic sensors for testing for diabetes

Power Supply

Spectrometer

Laptop Computer

Incubator Single test cell

LED light source

Fibre Optics

Laboratory demonstration system Normal eye illuminated with blue light

fluorescent green glow: glucose retention

Colour intensity plot: spectral variation through the lens

Optical Tonometer

• Active Non-Contacting Glaucoma Probe (AGP)

• 3 years of research, laboratory prototype tested on human subjects

• Design and implementation of an active Non-Contacting Glaucoma Probe which has the potential to be used as a low cost, on-line testing device.

• The objective is to provide a low cost probe which could be used by mobile medics, small practices and surgeons in the third world, eliminating in some cases the need for contact methods of testing methods

0 5 10 15 20 25 30 35 40 45290

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Intraocular pressure in mmHg

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in H

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Experiment data Fitted curve y=1.08x+293.50 Standard deviation of the residuals is 1.99

Warwick has recently been exploring the early detection of glaucoma. In this case the objective is to measure the intra-ocular pressure. This can be achieved using acoustic resonance.

Non-invasive, non-contact, intelligent tonometer for the detection of glaucoma

Test and prototyping a series of probes for application to ophthalmic surgery.

Criteria: external diameter < 0.8mm preferably disposable

debris suction optical fibre illumination

cutting capability

Further research: spectral analysis and proximity detection while retaining a disposable fibre optic construction.

Laser Eye Surgery Instrumentation

New Laser Cutting Tools for Vitrectomy

Suitability of IR (Infra Red) laser wavelengths has been investigated.

FTIR spectral plot shows 6.1 and 6.45 m to be particularly suited to soft tissue ablation.

FELIX Free Electron Laser facility in the Netherlands is being used to characterise the thermal, mechanical and molecular dynamics of the ablation process in swine vitreous.

A high resolution low cost Loupe system

• 1 year Smart Award, 2 years research as part of an EU grant.

• The loupe is for use in the third world as a low cost operating stereoscopic system.

• It uses low cost plastic aspheric lenses. The lens system has been designed with a magnification of 3 at an object distance of 300 mm. Its optical resolution is 20 lines/mm

• It has been designed to be viewed by the eye, which requires the exit pupil of the lens to be focused at infinity.

• The operation of the lens is to minimise spherical and chromatic aberrations. This is achieved by a complex surface curvature and a specially designed spectral spatial filter.

Surgical Loupe

If the innovations discussed are applied, then:

Cameras provide a visual history and library for surgeons and a map for operations where vision is restricted.

Intelligent cameras will assist in aiding the pre-diagnostics.

Images of the eye placed into a 3-D drawing model would allow the surgeon to evaluate the complexity of the operation.

Self-illuminating probes make surgery simpler and easier; they also free the surgeon, in that he no longer needs to control the position of the light source.

Active probes make training in surgery safer and can provide direct feedback, e.g. power delivery during laser ablation.

Disposable surgical instrumentation and non-contact diagnostics considerably lower risk of infection.

Intelligent non-contacting low cost intelligent diagnostics make the early detection of potentially sight threatening diseases possible.

Cumulative Effect of Technological Advances

The probes are still at an early research stage; but with the falling costs of computer technology and innovations in optical design and laser technology, the prospect of lower cost, synthetically intelligent, accurate optical diagnostics are starting to emerge.

Industrial Applications

Tomographic array

Spectral probe

Small Engine

Tomographic measurement of

heat release

• Part of a 3 year Faraday Intersect project with Rolls-Royce, CORUS and DERA as the industrial partners.

• The Aim here is to find a SME partner interested to develop the approach as a testing instrument for Rolls Royce.

• The probe is constructed from a ring of fibre optics which record the light emitted from the within the combustor. A tomographic reconstruction is used to capture the emitted light and a 40 fibre optics placed in a ring around the combustor. The objective of the work is to measure the heat release from the combustor to a spatial resolution of 10mm and a temporal resolution of 600Hz.

Tomographic array:

Modified Burner Array Result Colour Intensity photograph

Thermocouple Result

Fibres

Tomographic array

Spectral Measurements in a Gas Turbine Engine

• A spectrometer on a chip has been fibre optic linked to a diagnostic probe. The probe has been used in the fuel injector within the combustion chamber of a gas turbine engine. Tests have been made at RAe Farnborough to show how a engine can be run at a minimal running condition with switching off the engine.

• This work is part of the INTErSECT faraday Centre project: The Application of Data Fusion to a Multi Sensored Intelligent Engine.

• Its industrial partners are: Rolls-Royce, CORUS and DERA.

• The project represents 2 years of research work in the area.

Spectroscopic Measurements on a DERA Reverse Flow Combustor

Spectroscopic Measurements on a DERA Reverse Flow Combustor

Optical Access Through Injector

Fuel Injector

Fibreoptic

OUTLET

INLET

Primary Holes

Combustor Wall

Spectroscopic Measurements on a DERA Reverse Flow Combustor

Three-way Beam Splitter

25m UV Fibre Optic

25m VIS-IR Fibre Optic

Twin Channel Spectrometer

Combustor Rig

Spectroscopic Measurements on a DERA Reverse Flow Combustor

UV Fibre Idle Condition

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Wavelength (nm)

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308nm OH

394nm S2

430nm CH

470nmCHO

516nm C2

559nm C2

590nm H2O

The Small Engine project

• The operating pressure and temperature of a I.C. engine is very similar to those of a gas turbine engine. As a result of this a small low cost test bed engine has been develop on which a series of novel instruments are in the process of development. In particular the engine is optically instrumented and has heat transfer gauges mounted on its head and piston. It is possible to also investigate the fundamental aspects of, for example direct injection.

• This work is part of the INTErSECT faraday Centre project: The Application of Data Fusion to a Multi Sensored Intelligent Engine.

• It represents 2 years of research.

Heat Transfer

• Thin film, constant current, Platinum resistance, thermometers.

• 90 kHz response• Measure Heat Flux (Not

capacity)

Heat Transfer - Results

• Fired(note noise)

• Wall temp increases

• Interpretation

Firing Probe

Spark tip

ElectrodeFibreoptic

Coupling

GRIN lens

Plano-concave lens

Quartz Protection Window

• Spectroscopy

• Conveys light to Spectrometer

• 3mm lenses

• Overall optics diameter 4mm

Spectral Results

Wavelength (nm)

Intensity(counts)

Emission Spectra. 15 ATDC.

Wavelength (nm)

Emission Spectra. TDC.

Intensity(counts)