Introduction to Biophotonics for Medical Applications
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Introduction to Biophotonics for Medical Applications
Summarized by:Name: AGNES Purwidyantri
Student ID No: D0228005
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Biophotonics is the science of generating and harnessing light (photons) to image,
detect and manipulate biological materials
What is Biophotonics?
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Optical Manipulation
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TransfectionThe transfer of exogenous DNA into a cell
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Femtosecond Laser Mediated Cell
Membrane Poration
Photoporation: the use of light to permeabilise cells. First inspired
from a Tirlapur and Konig, Nature 2002:
Used a near-infrared, femtosecond-pulsed laser beam (λ
800 nm) from an 80-MHz titanium–sapphire laser, with a mean power of 50–100 mW and
tightly focused using a high-numerical-aperture objective
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Linear Fluorescence Microscopy
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Introduction to Optical Coherence Tomography (OCT)
OPTICAL BIOPSY: The in situ imaging of tissue microstructure with a
resolution approaching that of histology, but without the need for tissue excision and processing
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Optical Coherence TomographyThree-dimensional imaging technique with
ultrahigh spatial resolution even in highly scattering media
Based on measurements of the reflected light from tissue discontinuitiese.g. the epidermis-dermis junction.
Based on interferometryinvolves interference between the reflected
light and the reference beam.
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OCT vs. standard imaging
1 mm 1 cm 10 cm
Penetration depth (log)
1 mm
10 mm
100 mm
1 mm
Resolution (log)
OCTConfocalmicroscopy
Ultrasound
Standardclinical
Highfrequency
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OCT in non-invasive diagnosticsOphthalmology
diagnosing retinal diseases.
Dermatologyskin diseases,early detection of skin
cancers.Cardio-vascular diseases
vulnerable plaque detection.
Endoscopy (fiber-optic devices)gastrology,…
Functional imagingDoppler OCT,spectroscopic OCT,optical properties,PS-OCT.
• Guided surgery– delicate procedures– brain surgery,
knee surgery, …
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The OCT setup
Broadbandsource
Detector
Fiber-opticbeamsplitte
r
TissueScanningreference mirror
Computer
Amplifier Bandpass filter
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Interference
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1.5
2
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Michelson interferometer
light source
Detector
Coherent source
Partially coherent source
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Construction of image
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Normal Eye
Nominal width of scan: 2.8 mm
250 micronsHumphrey
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UHR-OCT versus commercial OCT
mm
mm
W. Drexler et al., “Ultrahigh-resolution ophthalmic optical coherencetomography”, Nature Medicine 7, 502-507 (2001)
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System perspective
OCT imaging engine• Resolution• Reference delay scanning• Doppler/polarization/spectroscopy• Detection• Frequency domain
Light sources• Superluminescent diodes• Semiconductor amplifiers• Femtosecond lasers• …
Beam delivery and probes• Hand-held probe• Catheter• Ophthalmoscope• Microscope
Image & signal processing• Motion reduction• Speckle reduction• Image enhancement• Rendering algorithms• …
Computer control• Drive system• Real-time display• Data management
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Choosing the light sourceFour primary considerations
wavelength,bandwidth,power (in a single-transverse-mode),stability;
portability, ease-of-use, etc.
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Choose light source – wavelength
Light propagation (Monte Carlo simulation)
Incident light
Ballistic component
“Snake” component
Diffuse reflectance
Absorption
Diffuse transmittance
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Ultra-high resolution OCTBroad bandwidth sources
solid-state lasers,sub-5 fs pulse;
Ti:Al2O3 (Spectral bandwidth: 350 nm demonstrated),other lasers/wavelengths available or needed.Special interferometers and fiber optics
support for broad spectral range,dispersion balanced,
current system used for OCT: 260 nm bandwidth, ~1.5µm resolution.
Chromatically corrected opticsaberrations can decrease resolution and SNR.Broad bandwidth detectors and electronics
dual balance detection, low noise circuitry necessary.
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Scanning devicesPiezo or motorized scanning devices
ideal for both longitudinal and lateral scanning.Galvanic mirrorsResonance scannersHelical mirrors
longitudinal scanning.Fiber stretcher
longitudinal scanning.
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RSOD (Rapid Scanning Optical Delay line) setup
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RSOD in the lab
Peter E. Andersen, Optics and Plasma Research Department
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Clinically adapted systems
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BCC II
LayersThinning of
layers
L. K. Jensen, MSc thesis (in Danish), 2003 [data obtained atLund Medical Laser Centre, courtesy K. Svanberg].
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OCT: Figures-of-merit – summaryDynamic range
100 dB (or better).Resolution (typical)
1-10 micrometers.Penetration depth
depending on wavelength/tissue,1-2 mm (typically) for
1300 nm in skin tissue.
Axial and lateral resolutions are decoupledimportant for
applications.
Pixel density is related to spatial resolution and image acquisition timeNz=2*Lz/dz,Nx=2*Lx/dx,image acq. time:
T=Nx*fs,scan velocity: vs=Lz*fs.
Image acquisitionseconds or less,real-time OCT.
Clinical adaptationinterfaced to standard
equipment,fiber-optic devices,endoscopes.
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Thank You