Questions & Answers
What is a measuring principle utilized in FluxEXPLORER imaging system?
FluxEXPLORER utilizes both laser Doppler and laser speckle effect for assessing blood microcirculation in superficial layer of biological tissue. The system uses laser light for illuminating the sample, and an array of photodetectors measuring backscattered light. Laser light scattered by moving particles obeys a slight frequency shift (Doppler-shift) proportional to the speed of moving objects. This light forms a speckle pattern on the detector. If light is Doppler-shifted the speckle pattern is fluctuating. Measuring the signal in a number of different points on the object allows obtaining two-dimensional maps of the flow distribution in the area.
Is FluxEXPLORER system invasive?
No, FluxEXPLORER system is non-invasive and non-contact. It utilizes a principle of remote sensing. From a distance, it uses laser light to illuminate the measured object and a special digital photocamera to make a picture of the flow distribution in the illuminated area.
What is a working distance of your instrument?
The working distance of the FluxEXPLORER system is fixed at 250 mm. It can slightly vary between 220 to 280 mm without serious influence on the measured result. Out of this working distance range, the obtained images will be unsharp due to the defocusing effect.
How deep FluxEXPLORER imaging system sees through the tissue?
FluxEXPLORER sees up to 2 mm deep into the tissue depending on the optical properties of the last.
What vascular beds FluxEXPLORER system can assess?
FluxEXPLORER imager is designed for measuring blood flow in the capillary vascular bed.
Can FluxEXPLORER measure blood flow in large vessels?
FluxEXPLORER imaging system can detect blood flow in larger vessels, like venuls, arterioles, arteries, and veins. Some time you can find them on the flow-image. However, the speed of the blood cells in such vessels is higher than FluxEXPLORER allows to measure. FluxEXPLORER can be utilized for detecting the blood flow in larger vessels but not for measuring the flow parameters in them.
What objects in the tissue FluxEXPLORER imaging system allows measuring?
FluxEXPLORER system measures flow of erythrocytes in the tissue. The lymphatic flow is not seen by the system.
Why do you use near-infrared light in your system?
FluxEXPLORER system uses near-infrared light source emitting at 808 nm. At this wavelength both oxygenated and deoxygenated blood have very similar optical absorption properties. So FluxEXPLORER system sees well the flow of both types of erythrocytes and the obtained signal does not depend on the oxygenated and deoxygenated blood shares.
How fast your system is?
In the FluxEXPLORER system you can chose between two acquisition modes: i) speed; or ii) accuracy. In the speed mode, the system generates flow images with a refresh rate of 1 image per second. The image quality is very comparable to that obtained with conventional laser Doppler scanners. This mode is recommended only if you need to measure fast changes in microcirculation signal. In the accuracy mode, the system generates high-quality flow-images every 6 seconds. This mode increases clinical confidence of the obtained data. This mode is much recommended for most of the applications.
Why FluxEXPLORER system is so fast?
FluxEXPLORER imager utilizes a plurality of photodetectors that allow measuring Doppler signal from thousands of points simultaneously. The use of parallel detection approach substantially reduces the imaging time. In contrast to Laser Doppler scanners that need 5-10 minutes to obtain one flow map, FluxEXPLORER takes only 1 second for the same task. Indeed the imaging time is reduced by a factor proportional to the number of photodetector channels measuring the signal in parallel.
Why the speed performance of your imaging system is a value for the user?
At first, high-speed imaging allows measuring changes of microcirculation having place in tissue in shorter time intervals. Secondly it reduces the patient discomfort while the measurement and additionally reduces the effect of movement artifacts caused by patient sudden displacement. Thirdly, fast imaging performance allows us utilizing Statistical Image Enchantment algorithm that increases measurement reliability of the instrument and adds clinical confidence for the obtained data. And the last but not least, high-speed performance adds convenience for utilizing the instrument. If the obtained image is doubtful or suddenly got some artifacts, it is only a matter of a few seconds to get the next high quality image for the analysis.
What is Statistical Image Enchantment algorithm?
Both Doppler and speckle signal measured from biological tissue has an essentially stochastic nature. This is caused by spread speed distributions of blood cells and random directions of their movement and other physical factors. So, measuring signal in one point, the signal value will be different at each period of time varying around the mean value. The longer the measurement time the better the measurement statistics is and the better the statistical confidence of the measurement. Statistical Image Enhancement algorithm allows obtaining highly detailed images of blood microcirculation in biological tissue. Measuring over longer period of time (less than 10 seconds) increases measurement reliability and increases clinical confidence for the obtained data. Visually it results in a highly detailed flow image. Indeed, the measurement accuracy increases as square-root of N, where N is number of sequentially obtained flow-images. So in about 6 seconds (10 images obtained) our apparatus generates an image which is more than 3 times statistically more accurate compared to single image acquisition mode.
Why do you use both Laser Speckle and laser Doppler approaches in one system?
Laser Doppler Flowmetry is a very well known medical technology for assessing microcirculation in biological tissue. It is an established technology used in fluxometers/flowmeters to assess perfusion in a single spot of tissue using direct-contact probe and light-guiding optical fibers. Laser Doppler scanners allow obtaining two-dimensional images of blood perfusion in tissue, but they are yet too slow (5-10 minutes per one flow image). Laser Speckle Imaging is an alternative technology for accessing microcirculation. They allow obtaining the flow images in real time, however they have narrow dynamic range and low measurement ratability if there no accurate calibration was performed before the measurement. It allows assessing the flow rather to measure it reliably. Laser Speckle Imaging technique was developed about 20 years ago. Already at that time, there were no serious technological obstacles to make a product based on this technology. Nevertheless, up to now, it was used only by physicists who were trying to improve the performance of such instruments. In our system we use a new appropriate patented technology that allowed us combining two imaging approaches for using the benefits of both and drawbacks of neither. Our device is fast and accurate. We offer you an imaging system synergizing benefits of well-known technologies with modern innovative performance and convenience to handle the instrument.
What are the limitations of FluxEXPLORER imaging system?
As any laser Doppler or laser speckle imaging system FluxEXPLORER is "afraid" of movement artifacts caused by movement of the object under measurement. E.g. if hand suddenly moved or if the fingers are shaking, it will be difficult to get high quality image. Also, the imager head should be fixed and stabilized else obtained images will get movement artifacts caused by the imager head oscillation. Very dark skin pigmentation or reach hair-covering increases light absorption that also can result in lower quality for the obtained images. Also, the FluxEXPLORER user should pay attention to the right working distance for the imager head (typically it is 250 mm), else the obtained images will be not sharp due to defocusing effect.