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Introduction to Biophotonics for Medical Applications. Summarized by: Name: AGNES Purwidyantri Student ID No: D0228005. Biophotonics is the science of generating and harnessing light (photons) to image, detect and manipulate biological materials. What is Biophotonics ?.

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introduction to biophotonics for medical applications

Introduction to Biophotonics for Medical Applications

Summarized by:

Name: AGNES Purwidyantri

Student ID No: D0228005

slide2
Biophotonics is the science of generating and harnessing light (photons) to image, detect and manipulate biological materials

What is Biophotonics?

transfection
Transfection

The transfer of exogenous DNA into a cell

femtosecond laser mediated cell membrane poration
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

introduction to optical c oherence t omography oct

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

optical coherence tomography
Optical Coherence Tomography
  • Three-dimensional imaging technique with ultrahigh spatial resolution even in highly scattering media
  • Based on measurements of the reflected light from tissue discontinuities
    • e.g. the epidermis-dermis junction.
  • Based on interferometry
    • involves interference between the reflected light and the reference beam.
oct vs standard imaging

Resolution (log)

1 mm

Ultrasound

100 mm

10 mm

Confocalmicroscopy

1 mm

Penetration depth (log)

1 mm

1 cm

10 cm

OCT vs. standard imaging

Standardclinical

Highfrequency

OCT

oct in non invasive diagnostics
OCT in non-invasive diagnostics
  • Ophthalmology
    • diagnosing retinal diseases.
  • Dermatology
    • skin diseases,
    • early detection of skin cancers.
  • Cardio-vascular diseases
    • vulnerable plaque detection.
  • Endoscopy (fiber-optic devices)
    • gastrology,
  • Functional imaging
    • Doppler OCT,
    • spectroscopic OCT,
    • optical properties,
    • PS-OCT.
  • Guided surgery
    • delicate procedures
    • brain surgery,
      • knee surgery,
t he oct setup
The OCTsetup

Fiber-optic

beamsplitter

Broadband

source

Tissue

Scanning

reference mirror

Detector

Computer

Amplifier

Bandpass filter

interference
Interference

Coherent source

Michelson interferometer

light source

Detector

Partially coherent source

normal eye
Normal Eye

250 microns

Humphrey

Nominal width of scan: 2.8 mm

uhr oct versus commercial oct
UHR-OCT versus commercial OCT

W. Drexler et al., “Ultrahigh-resolution ophthalmic optical coherence

tomography”, Nature Medicine 7, 502-507 (2001)

system perspective
System perspective
  • Light sources
  • Superluminescent diodes
  • Semiconductor amplifiers
  • Femtosecond lasers
  • Beam delivery and probes
  • Hand-held probe
  • Catheter
  • Ophthalmoscope
  • Microscope
  • OCT imaging engine
  • Resolution
  • Reference delay scanning
  • Doppler/polarization/spectroscopy
  • Detection
  • Frequency domain
  • Computer control
  • Drive system
  • Real-time display
  • Data management
  • Image & signal processing
  • Motion reduction
  • Speckle reduction
  • Image enhancement
  • Rendering algorithms
choosing the light source
Choosing the light source
  • Four primary considerations
    • wavelength,
    • bandwidth,
    • power (in a single-transverse-mode),
    • stability;
      • portability, ease-of-use, etc.
choose light source wavelength
Choose light source – wavelength
  • Light propagation (Monte Carlo simulation)

Absorption

“Snake” component

Incident light

Ballistic component

Diffuse reflectance

Diffuse transmittance

ultra high resolution oct
Ultra-high resolution OCT
  • Broad 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 optics
    • aberrations can decrease resolution and SNR.
  • Broad bandwidth detectors and electronics
    • dual balance detection,
    • low noise circuitry necessary.
s canning devices
Scanning devices
  • Piezo or motorized scanning devices
    • ideal for both longitudinal and lateral scanning.
  • Galvanic mirrors
  • Resonance scanners
  • Helical mirrors
    • longitudinal scanning.
  • Fiber stretcher
    • longitudinal scanning.
rsod in the lab
RSOD in the lab

Peter E. Andersen, Optics and Plasma Research Department

bcc ii
BCC II
  • Layers
  • Thinning oflayers

L. K. Jensen, MSc thesis (in Danish), 2003 [data obtained atLund Medical Laser Centre, courtesy K. Svanberg].

oct figures of merit summary
OCT: Figures-of-merit – summary
  • Dynamic 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 decoupled
    • important for applications.
  • Pixel density is related to spatial resolution and image acquisition time
    • Nz=2*Lz/dz,
    • Nx=2*Lx/dx,
    • image acq. time: T=Nx*fs,
    • scan velocity: vs=Lz*fs.
  • Image acquisition
    • seconds or less,
    • real-time OCT.
  • Clinical adaptation
    • interfaced to standard equipment,
    • fiber-optic devices,
    • endoscopes.