OCT – Optical Coherence Tomography
Optical Coherence Tomography The Heidelberg spectralis OCT is one of the most advanced and precise equipment used to do the optical coherence tomograghy investigation giving high resolution images and precise information used in obtaining:
- MultiColor fundus photo
- Anterior Segment Scanning
- Nerve Fiber Layer Analysis
- Macula analysis
- OCT Angiography
With non comparable speed ,resolution and precision along with many other advantages as the scans are done without pupil dilatation and the advantages of follow up with exact scan location every time.
OCT delivers high resolution because it is based on light, rather than sound or radio frequency. An optical beam is directed at the tissue, and a small portion of this light that reflects from sub-surface features is collected.
Note that most light is not reflected but, rather, scatters off at large angles. In conventional imaging, this diffusely scattered light contributes background that obscures an image.
However, in OCT, a technique called interferometry is used to record the optical path length of received photons allowing rejection of most photons that scatter multiple times before detection.
Thus OCT can build up clear 3D images of thick samples by rejecting background signal while collecting light directly reflected from surfaces of interest.
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Within the range of noninvasive three-dimensional imaging techniques that have been introduced to the medical research community,
OCT as an echo technique is similar to ultrasound imaging. Other medical imaging techniques such as computerized axial tomography, magnetic resonance imaging, or positron emission tomography do not use the echo-location principle.
On the other hand, This technique is limited to imaging 1 to 2 mm below the surface in biological tissue, because at greater depths the proportion of light that escapes without scattering is too small to be detected.
No special preparation of a biological specimen is required, and images can be obtained ‘non-contact’ or through a transparent window or membrane.
It is also important to note that the laser output from the instruments used is low – eye-safe near-infrared or visible-light – and no damage to the sample is therefore likely.