OPTICAL COHERENCE TOMOGRAPHY (SKIN OCT).... Optical coherence tomography (OCT) is an established medical imaging technique that uses light to capture micrometer-resolution, three dimensional images from within optical scattering media (e.g., biological tissue). Optical coherence media (e.g., biological tissue). Optical coherence tomography is based on low coherence interferometry, typically employing near-infrared light. The use of relative long wavelength light allows it to penetrate into the scattering medium. Confocal microscopy, another optical technique, typically penetrates less deeply into the sample but with higher resolution.

1. HALDIA INSTITUTE OF TECHNOLOGY
SKIN OCT
Presented By KALLOL BALA
Electronics & Instrumentation Engineeing
Roll No- 12/EIE/33

2. WHAT IS OCT ?
 Optical coherence tomography (OCT) is an
established medical imaging technique that uses
light to capture micrometer-resolution, three
dimensional images from within optical scattering
media (e.g., biological tissue). Optical coherencemedia (e.g., biological tissue). Optical coherence
tomography is based on low coherence interferometry,
typically employing near-infrared light. The use of relative
long wavelength light allows it to penetrate into the scattering
medium. Confocal microscopy, another optical technique, typically
penetrates less deeply into the sample but with higher resolution.

3. BASIC PRINCIPLE OF OCT.
 Three-dimensional imaging technique with high spatial resolution and
large penetration depth even in highly scattering media.
 Based on measurements of the reflected light from tissue
discontinuities
 e.g. the epidermis-dermis junction.
 Based on interferometry Based on interferometry
 interference between the reflected light and the reference beam
is used as a coherence gate to isolate light from specific depth.

4. THEORY OF OCT
 The principle of OCT is white light or low coherence interferometry. The
optical setup typically consists of an interferometer with a low coherence,
broad bandwidth light source. Light is split into and recombined from
reference and sample arm, respectively.

5. USE OF OCT IN MEDICAL SCIENCE
• Ophthalmology
– diagnosing retinal diseases.
• Dermatology
– skin diseases,
– early detection of skin
cancers.
• Functional imaging
– Doppler OCT (blood flow)
– spectroscopic OCT
(absorption, high speed)
– optical properties
– Polarization Sensitive-OCTcancers.
• Cardio-vascular diseases
– vulnerable plaque detection.
• Endoscopy (fiber-optic devices)
– gastroenterology
– gynecology
• Embryology/Developmental
biology
– Polarization Sensitive-OCT
(birefringence).
• Guided surgery
– delicate procedures
• brain surgery,
• knee surgery

6. WHERE OCT IS USED BY
DERMATOLOGIST
 Skin tumors, primarily non-melanoma skin cancers
 Inflammatory skin diseases
 Fungal elements in nail infections (onychomycosis)
 OCT has been particularly useful in delineating excision
margins prior to Mohs surgery for BCC.
 OCT imaging can improve diagnostic accuracy for BCC
 OCT can potentially reduce the size of the surgical defect

7. EQUIPMENT

8. HOW DISEASES DETECTED BY OCT
Based on the principle of low-coherence interferometry, cross-
sectional images of the human skin can be obtained in vivo with
a high spatial resolution of about 15 microns. Within a
penetration depth of 0.5 to 1.5 mm, structures of the stratum
corneum, the living epidermis, and the papillary dermis can be
distinguished.

9. RESULTS
 Different layers could be det-
ected that were differentiated
by induction experimental
blisters and by comparison
with corresponding histologic
sections. Furthermore, OCT
images of several skin diseases and tumors were
obtained.

10. SKIN OCT: TECHNIQUE
 Fringe amplitude is proportional to amount of
reflected light from a specific depth
 Longitudinal (depth) resolution by coherence gate of the reference
arm, determined by the
coherence length Lc (~2-10 μm)
 Penetration depth determined by the scattering coefficient of tissue;
Signal decays exponential with depth

11. FEATURES/ADVANTAGE
 Live sub-surface images at near-microscopic
resolution
 Enable instant, direct imaging of tissues
morphology
 No preparation of the sample or subject is required No preparation of the sample or subject is required
 No ionizing radiation
 2-3 mm penetration in tissue
 Based on optics rather than radio waves

12. OCT VS USG

13. LIMITATION OF SKIN OCT
 Penetration: 2-3mm Ideal: 4mm
 Resolution :
catheter/endoscope based image: 10μm,
noncatheter: 4 μm,
1. femtosecond laser is expensive (1 μm)1. femtosecond laser is expensive (1 μm)
2. transverse resolution needs to be similar to axial
resolution, below 10 μm need short confocal
parameter which results in the focus falling off
rapidly.
 Acquisition rate: <10franes/second
 Lack of large-scale clinical trials

14. CONCLUSION
 Oct is able to characterize normal and pathologic
variation by providing high-resolution skin
images.
 Oct image help in integrated evaluation in
research.research.
 Advances in skin OCT technology and further
research on clinical applications have the
potential to contribute to the trend toward non-
surgical evaluation.

15. END
THANK YOUTHANK YOU