PeriCam PSI System Design Principle

The  PeriCam PSI System is a real-time microcirculation imager based on the laser speckle technology. The PeriCam PSI System consists of four major parts:

Measurement laser

The PeriCam PSI System uses a 70 mW  laser diode for blood perfusion measurements. The beam is spread over an area by a diffuser. The size of the illuminated area depends on the distance between the laser aperture in the head and the measurement object.

Indicator laser 

A visible near infra red (NIR) indicator laser is used to indicate the maximum measurement area since the wavelength of the measurement laser is invisible to the human eye. To avoid interference with measurements the pattern laser is switched off during recording. 

Detector camera 

The blood perfusion in the scanned area is monitored using a 1388 x 1038 pixel CCD camera that can take images at a speed of up to ~100 per second. 

Documentation camera

A color camera is used for documentation. The capture rate can be set at different speeds. The color photos provide an extra help when placing regions of interest (ROIs), assuring that the object has not moved during the recording and for understanding the obtained blood perfusion and intensity images. 

To assure high quality data, the following properties have been implemented:

Measurement accuracy

The PeriCam PSI System will show an accuracy of ±10% (Motility Standard).To achieve this level of accuracy, the PeriCam PSI System has been implemented with a fixed focal length rather than a variable zoom. Varying the zoom will result in changes in the size of the speckles in the speckle pattern. The size of the speckles in the speckle pattern influences the blood perfusion values monitored. To control this non physiological factor, zooming is not possible with the PeriCam PSI System ensuring that all measurements are carried out with the same sized speckles. It also avoids the need for additional compensations in the algorithms.

Automatic background compensation

To compensate for changes in the background light during measurements, an automatic background compensation is carried out once every second. This ensures comparable results between identical experiments, regardless of environmental lighting variations.