Instrument and method for high-speed perfusion imaging

An instrument for high-speed laser perfusion imaging comprises a laser source, a detector, a signal-processing unit, data memory, and a screen to display the results. A section of the sample surface is illuminated with laser light; the reemitted light from the irradiated surface is collected by the focusing optics on a 2D array of integrating photo detectors. The elements of the 2D array can be accessed individually or in a pre-defined selection of pixels at high speed. This 2D array of random-pixel- access integrating photo detectors (for example an integrating CMOS image senor) is utilized to measure the intensity variations at each individual pixel. The average amplitude and the mean frequency of the measured signal contain information about concentration and speed of moving blood cells. For real-time imaging, the exposure time is used as a parameter to measure relative perfusion changes. These data are stored in a memory and processed with a signal-processing unit. The instrument delivers 2D flow maps of the illuminated sample section. In parallel a conventional image of the sample can be obtained with the same 2D array of photo detectors allowing a simple overlay between a conventional image and processed flow maps. The instrument enables objective high-speed tissue perfusion imaging and real-time perfusion monitoring.

Laser perfusion imaging system for acquiring flow-related images of object for medical diagnosis comprises coherent light source and image sensor(s) made by randomly addressed two-dimensional array of integrating photodetectors

Theo Lasser

An instrument for high-speed laser perfusion imaging comprises a laser source, a detector, a signal-processing unit, data memory, and a screen to display the results. A section of the sample surface is illuminated with laser light; the reemitted light from the irradiated surface is collected by the focusing optics on a 2D array of integrating photo detectors. The elements of the 2D array can be accessed individually or in a pre-defined selection of pixels at high speed. This 2D array of random-pixel-access integrating photo detectors (for example an integrating CMOS image senor) is utilized to measure the intensity variations at each individual pixel. The average amplitude and the mean frequency of the measured signal contain information about concentration and speed of moving blood cells. For real-time imaging, the exposure time is used as a parameter to measure relative perfusion changes. These data are stored in a memory and processed with a signal-processing unit. The instrument delivers 2D flow maps of the illuminated sample section. In parallel a conventional image of the sample can be obtained with the same 2D array of photo detectors allowing a simple overlay between a conventional image and processed flow maps. The instrument enables objective high-speed tissue perfusion imaging and real-time perfusion monitoring.

2006

High speed laser Doppler perfusion imaging system e.g. blood flow imaging system, detects laser Doppler signal and/or laser speckle signal from light reflected from selected blood vessel area, to obtain flow data

Theo Lasser

An instrument for high-speed laser perfusion imaging comprises a laser source, a detector, a signal-processing unit, data memory, and a screen to display the results. A section of the sample surface is illuminated with laser light; the reemitted light from the irradiated surface is collected by the focusing optics on a 2D array of integrating photo detectors. The elements of the 2D array can be accessed individually or in a pre-defined selection of pixels at high speed. This 2D array of random-pixel-access integrating photo detectors (for example an integrating CMOS image senor) is utilized to measure the intensity variations at each individual pixel. The average amplitude and the mean frequency of the measured signal contain information about concentration and speed of moving blood cells. For real-time imaging, the exposure time is used as a parameter to measure relative perfusion changes. These data are stored in a memory and processed with a signal-processing unit. The instrument delivers 2D flow maps of the illuminated sample section. In parallel a conventional image of the sample can be obtained with the same 2D array of photo detectors allowing a simple overlay between a conventional image and processed flow maps. The instrument enables objective high-speed tissue perfusion imaging and real-time perfusion monitoring.

2006

Endoscopic low coherence interferometry applied to tri-dimensional contouring of upper airways

Yves Delacrétaz

This thesis presents a novel approach for optical tri-dimensional contouring, requiring only one acquisition to extract a contour depth. It is based on an interferometric setup, using a reduced coherence light source, and is fully adaptable to endoscopic procedure commonly in used in ear-nose-throat (ENT) medicine. It has been demonstrated that the method can be successfully applied to imaging of porcine upper airways. Although this method uses interferometry to obtain depth range measurement, the phase signal is not directly evaluated, rather the location of the coherent superposition of two waves is extracted, and thus provides a robust technique even in harsh environment. The key feature is to extract the coherent area on the image by locating intentionally induced fringes created by off-axis superposition of a smooth reference wave and an object wave coming from a rough or diffusing sample through an optical system with limited aperture. A model for the propagation of the light through the optical system has been developed. It takes into account the broadened emission spectrum of the light source, as well as the statistical speckle effect induced by the illumination of a rough surface with partially coherent light. Simulated results have been carefully compared with measurements, both in the spatial domain and in the Fourier domain (spatial frequencies response), which has permitted to better understand the processes involved in the creation of the interference fringes, and improve the design of the device. Different filters have been investigated in order to extract the depth information from acquired interferograms. By using Gabor filterbanks, which do not need any a priori knowledge of the signal, selectivity of the extracted signal has been enhanced by a factor of 1.3 compared to a simple local Fourier spectrum evaluation, and time of the extraction procedure divided by 6, even when compared to fast iterative calculation in the Fourier spectrum. Moreover, by imposing the frequency and/or orientation of the signal to detect, which can be known by a simple calibration procedure, it has been proved that the selectivity can be further enhanced by a factor of 2.5, keeping the calculation time as short or even shorter. A compact prototype has been designed and built, with a specific multiple fibers arrangement for illumination. The system is separated in two parts: the first one is directly attached to the rigid endoscope, and contains imaging as well as recombining object/reference wave optics, and the detector. It fits into a box with overall dimensions of 115 × 83 × 94 mm. The second part contains the laser source, the scanning arm and the injection optics for the fibered system. It is designed to be left on a small cart. This device can potentially be brought to the bedside, and used during routine endoscopic check-up. Associated with the device, a complete framework has been elaborated in order to simplify the acquisition procedure as well as the signal processing. This results in a fully automated environment taking in charge hardware control, data storage and signal processing, up to the tri-dimensional scene rendering.

EPFL2009

Endoscopic low coherence interferometry applied to tri-dimensional contouring of upper airways

Yves Delacrétaz

EPFL2009