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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. 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

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  1. Introduction to Biophotonics for Medical Applications Summarized by: Name: AGNES Purwidyantri Student ID No: D0228005

  2. Biophotonics is the science of generating and harnessing light (photons) to image, detect and manipulate biological materials What is Biophotonics?

  3. Optical Manipulation

  4. Transfection The transfer of exogenous DNA into a cell

  5. 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

  6. Linear Fluorescence Microscopy

  7. 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

  8. 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.

  9. 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

  10. 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, • …

  11. The OCTsetup Fiber-optic beamsplitter Broadband source Tissue Scanning reference mirror Detector Computer Amplifier Bandpass filter

  12. Interference Coherent source Michelson interferometer light source Detector Partially coherent source

  13. Construction of image

  14. Normal Eye 250 microns Humphrey Nominal width of scan: 2.8 mm

  15. UHR-OCT versus commercial OCT W. Drexler et al., “Ultrahigh-resolution ophthalmic optical coherence tomography”, Nature Medicine 7, 502-507 (2001)

  16. 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 • …

  17. Choosing the light source • Four primary considerations • wavelength, • bandwidth, • power (in a single-transverse-mode), • stability; • portability, ease-of-use, etc.

  18. Choose light source – wavelength • Light propagation (Monte Carlo simulation) Absorption “Snake” component Incident light Ballistic component Diffuse reflectance Diffuse transmittance

  19. 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.

  20. 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.

  21. RSOD (Rapid Scanning Optical Delay line) setup

  22. RSOD in the lab Peter E. Andersen, Optics and Plasma Research Department

  23. Clinically adapted systems

  24. BCC II • Layers • Thinning oflayers L. K. Jensen, MSc thesis (in Danish), 2003 [data obtained atLund Medical Laser Centre, courtesy K. Svanberg].

  25. 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.

  26. Thank You

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