Even with advanced medicine, there is still so much we have yet to learn about the human brain. Hyperspectral imaging solutions are helping in a variety of medical applications, including brain surgery and brain research.
For example, Polytechnique Montréal has developed a system that can be used during epilepsy or brain cancer surgery. It is used to monitor hemodynamic changes occurring after brain activity. The technique relies on the fact that oxygenated and deoxygenated hemoglobin respond to white light very differently.
After neuronal activity, there is an increase in cerebral blood flow to provide oxygen to active neurons. The ratio between oxygenated and deoxygenated hemoglobin is then locally changed. The specific manner in which the oxygen is provided and consumed by the neurons can give a lot of information about brain’s health and connectivity. The oxygenated and deoxygenated blood can be separated to create 2D maps because they can be spectrally resolved using hyperspectral video cameras. Color cameras could not provide the specific light bands required to see the differences and monochrome cameras with different filters have been used in the past but are slow and restrictive. The accuracy and speed is greatly improved using 16 spectral bands as provided by a hyperspectral camera from Imec’s latest image sensors available with Adimec cameras by Imec.
Imec’s system implements spectral filters right on the sensor to create a compact, fast, and low cost solution by eliminating bulky and expensive optics. Imec also developed evaluation software to complete the image processing.
There are two different imaging sensor options currently available: snapshot and scanning (pushbroom applications).
The scanning solution has hyperspectral filters on a CMOSIS CMV2000, 2 Megapixels at 340 fps, sensor in a staircase type structure where each band is for a different wavelength. For the spectral range of 600 to 1000 nm, there are 100 spectral bands with 16 spectral lines/band and 2048 spatial pixels/line.
The number of filters and layout can be customized to fit the application. The sensor can be filled with only selected bands and is not restricted to a continuous wavelength range or line arrangement.
For applications where scanning is not desirable such as security with fast moving objects, the snapshot option is also available. This is implemented differently where either the image sensor is subdivided into 32 zones (filters for a specific wavelength) of 256 x 256 pixels, or a mosaic structure (4x4 or 5x5) pixels is used to cover respectively 16 or 25 bands. The snapshot sensor versions available today are also based on the CMOSIS CMV2000.
For more information about Adimec’s and Imec’s work together, click here.
Images of the system are shown below. The system is currently being tested during surgery and results will be published soon.
This system can also be used for discoveries of the brain. More details on this to come in later articles.
Images provided by the Laboratory for Radiological Optics, Polytechnique Montréal
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