Imaging in difficult environments: The digital
Ophthalmoscope and the potential creation of a
low cost capillary imaging system
Prof Peter Bryanston-Cross
School of Engineering
Rolls-Royce Trent 800 engine with serrated nozzle to reduce engine noise
Time & Cost
Method:
Measurement:
Data Resolution
Processing:
Deliverables:
Processing:
Each engine test costs £200k and is completed in 10days
Inject 0.8 micron particles in to the 1500oC 300Km/hr flow
Imaging of the particles
100 microns over 48 ‘stitched 200mmx200mm frames
Stereo PIV (Particle Image Velocimetry)
Complete velocity mapping of the exhaust in 3D in 3 hrs
3 months to process 10 Tbytes of data
Optical Medical
instrumentation
As part of a feasibility project a survey was made as to the diagnostics
medical practitioners use in the process of a typical consultation.
Typical consultation
 5-10 minutes reading patients notes
 Assess facial colouring, signs of a flush for example
 Discuss with the patient their symptoms
 Measure blood pressure
 Measure pulse
Lack of Diagnostic Information
No previous diagnostic history other than text
No self monitoring information
Some instruments considered too difficult to use
70% likely outcome : If thing do not change come back next week.
5% likely out come: referred to hospital or specialist.
Existing Devices: ECG & Digital Stethoscope
 Electro Cardio Graph
 Cardio24
Existing Devices: Pulse Oximeter
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Pulse oximetry provides
estimates of arterial
oxyhemoglobin saturation
(SaO2) by utilizing selected
wavelengths of light to
noninvasively determine the
saturation of oxyhemoglobin
(SpO2)
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Nonin OEM II module
– RS232-connection
– Bluetooth connection
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http://www.adinstruments.com/products/list.php?group=Transducers*and*Accessories&sectionurl=Pulse*Oximetry&testgroup=N
Existing Devices: Pulse Oximeter
75 measurements per second
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HR MSB
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SpO2 Slew
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Combining Diagnostics
 ECG
 Stethoscope
 Pulse oximeter
Will give real-time feedback on
 Heart condition
Valve operation
Chamber contraction
 Blood oxygenation
Prof. Singer Contacted the Mathematics Group to Initiate a
Research Programme in Vascular Mechanisms.
From an instrumentation basis the questions was asked
What type of measurements are being made
What is required
What type of instrument is used
Do we have the relevant expertise
Could a low cost portable diagnostic instrument with suitable resolution be developed and
Would it have value
.
Microcirculation Capillaroscopy
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Microcirculation
Microcirculation plays a key role in tissue oxygenation
Red blood cell (RBC) is the indicator of the oxygen delivery. It is widely
used in clinical studies
Capillaroscopy
for analysing images of the microcirculation using spectrophotometry in
order to compute a complete blood count (CBC) without removing
blood from the body[1]
Orthogonal polarization spectral (OPS) imaging
Sidestream dark-field (SDF) imaging
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
OPS imaging
Orthogonal
Polarization
Spectral (OPS) imaging [2]
Cytocan-II by Cytometrics
(1) Polarized light
(548nm)
(2) Depolarized
scattered light
(3) CCD camera
(4) Reflected
polarized light is
eliminated
CytocanII
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
OPS imaging
Advantages
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Better clarity (than conventional reflectance imaging)
Light wavelength (600–1100 nm) reduces scattering
and absorption for tissues
Clinical validated
Disadvantages
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Illumination scattering, blurring
Contrast from reflected light
Resolution
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
SDF imaging
LEDs: 540±50 nm
Vessels can be seen only
if they contain RBCs,
which appear dark
Sidestream
Dark-field (SDF)
imaging[3]
MicroScan Video
Microscope by
MicroVision Medical
14
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
Advantages
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SDF imaging
Better clarity, sensitivity and resolution (than OPS)
Fine-tune the depth of focus without moving
the probe, thus without blurring
portable operation
Clinical validated
Disadvantages
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Video frame rates at 750 pixels/sec
(25 fps (PAL) or 30 fps (NTSC))
Resolution
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
Video output was visualized on a monitor and
connected to a computer via a signal converter
(Canopus, ADVC110) to directly and digitally
record images onto a hard drive as DV-AVI files to
enable off-line analysis of the images.[4]
majority capillaries size (10 to 35 μm)
10 microns = 50lp/mm (line pairs per
millimetre) resolution
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
RBC Velocity Determination
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image registration and pre-processing
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skeleton extraction
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sketch the skeleton to estimate
horizontal and vertical displacements
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velocity of all the pixels
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
RBC Velocity Determination
•A 45-second video of capillary blood flow
•1350 continuous frames (30 fps)
•The RBC velocity of 12 vessels (at 3 sites)
Microcirculatory Analysis
Software (MAS 2.0)
•microcirculatory blood vessel
diameters
•RBC kinetics
(Academic Medical Centre, University of Amsterdam).
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
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Conclusion
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Available instrumentation exists which has adequate resolution
However,
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There is the potential to create a low cost portable instrument.
There is the potential to create a high resolution portable system
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The resolution and design closely matches that developed for the digital
ophthalmoscope.
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The processing applied closely matches that used for processing
aerodynamic research currently in progress
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The Resolution and frame rate could be improved significantly
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Advanced computer-aided image processing tools are avaiable
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CMOS cameras to improve power consumption and resolution
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation
References
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[1] NADEAU RG, GRONER W: Orthogonal polarization spectral imaging: State of the Art. In: Orthogonal
Polarization Spectral Imaging. MESSMER K (ed). Karger, Basel, Vol 24, pp 9-20. (2000)
[2] Černý, V. TUREK, Z. PAŘÍZKOVÁ, R. Orthogonal Polarization Spectral Imaging. Physiological
Research. Minireview. 56: p141-147, (2007).
[3] Ince C. Sidestream dark field imaging: an improved technique to observe sublingual microcirculation.
Critical Care 9 (Suppl 1): P72, (2005).
[4]Goedhart PT, Khalilzada M, Bezemer R, Merza J, Ince C. Sidestream Dark Field (SDF) imaging: a novel
stroboscopic LED ring– based imaging modality for clinical assessment of the microcirculation. Optics
Express;15:15101-14. (2007).
[5]Leahy, M, J. et al. Biophotonic methods in microcirculation imaging. Medical Laser Application, 22-2, p
105-126. (2007).
2009-2010 ES9P5 Remote Sensing and Data Processing Presentation