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Speckle Imaging
Laser Speckle Techniques for Blood Flow Imaging
What is Laser Speckle?
Laser speckle is an optical interference effect that can be observed when objects are illuminated with laser light. This effect is grainy in appearance, with light and dark "speckles" caused by constructive and destructive interference, respectively, of scattered laser light.
If the illuminated area contains individual moving scatterers, such as blood cells, the grainy "speckle" effect fluctuates. By analyzing these fluctuations, it is possible to obtain velocity distribution information about the scatterers; hence, a non-invasive method of monitoring blood flow can be developed.
Laser Speckle functional schematic
How Does Laser Speckle Imaging Work?
A laser speckle imaging system basically consists of a laser light source, a high-resolution CCD Camera, and a computer equipped with a "frame grabber" and imaging software. It is important to select a laser wavelength suitable to the tissue under observation, as it is necessary to achieve some tissue surface penetration with the laser light for blood flow mapping.
The sample, or area of interest, is illuminated with laser light while the computer acquires a series of images at high speed with the frame grabber and CCD camera. Each acquired image will display a slightly different speckle pattern, caused by the change of position of moving scatterers in the area of interest. If the time lapse between images is known, it is possible to examine the intensity variation of individual speckles at the same position in each image and calculate the velocity of the scatterers responsible for the variation.
How Can Laser Speckle be Used?
Scanning laser Doppler acquisition of the forearm
Laser speckle offers the possibility of developing a full-field technique for velocity map imaging which produces an instantaneous map of velocities in real time.
The NRC-IBD Spectroscopy Group is using laser Doppler and speckle techniques to measure blood flow non-invasively in assessing conditions such as bowel obstruction and skin flap failure.
Related Information
Read more about Speckle Imaging:
- Diffuse Reflectance Spectroscopy
- Non-linear Optical Microscopic Imaging
- Fluorescence Imaging
- Frequency Modulated Spectroscopy
- MRI Studies
- Bioluminescence Imaging
- Molecular Imaging - Spectroscopy
- Optical Coherence Tomography
- Raman Spectroscopy
- Thermal Imaging
- High Throughput Diagnostics
- Diagnostic Technologies
