JPS60199430A - Laser speckle blood flow meter - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser speckle blood flow meter for measuring the state of blood flow in living tissue using the laser speckle phenomenon.

Generally, when a laser beam is irradiated toward a scattering object, the wavefront is disturbed by diffused reflection, resulting in a so-called speckle pattern.

When the scattering object moves over time, this speckle pattern changes from moment to moment, and when the speckle pattern is measured at a fixed position on the receiving side, the light intensity of the speckle changes over time. 6 The present invention applies this to the measurement of blood cells in living tissues.

By the way, conventionally, the blood flow meter and the 17th patent were
A device described in Publication No. 4 is known. This is because a photodetector receives laser scattered light from moving blood cells, and a high-pass filter selects among the many beat frequency components included in the frequency range of 0 to 20KHz of the output of the photodetector. The basic principle is to remove the direct current component, amplify the remaining alternating current component, and divide that component by the total output signal of the photodetector, thereby creating a correlation with the state of blood flow.

An object of the present invention is to provide a laser speckle blood flow meter with a simple configuration, which is different from the conventional example described above.

The gist of the present invention is to provide a laser light source, a light emitting fiber for irradiating light from the laser light source to blood cells in a living tissue, and a laser beam that changes over time from the blood cells in the living tissue. an optical receiving fiber that transmits the optical signal, a photodetector that detects the speckle light intensity transmitted by the optical receiving fiber, and a speckle optical intensity detected by the optical detector that is compared with a predetermined level to ensure that both match. Laser specifications include a frequency-to-voltage converter that generates a pulse train that decays with a constant time constant every time the pulse is turned on, and then passes through a low-pass filter to convert it into an averaged voltage output. [Signal pronunciation]
It is.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 1 shows blood flow A according to the present invention! FIG. H
The +l F wafer laser beam from the e-Ne laser light source B irradiates the skin surface S through one light-emitting optical fiber F+, enters the tissue to a depth of about 1 mm, and enters the blood cells in the capillary tube. The speckle light that is scattered and shaped is detected by the photoelectron amplifier PM via the optical fiber F2 for receiving light.Then, the output of the photoelectron amplifier PM changes depending on the movement of the blood cells. This light changes over time71
The output of the J amplifier tube PM is amplified by an amplifier A.

As a signal frequency analysis method, in this example, the simplest method is frequency-electronic n: 4! A converter is used. That is, the output from amplifier A is passed through a high-pass filter FL, and then the DC component is input to the frequency contrast-voltage converter F/V.
Enter.

In the present invention, the high-pass filter FL is used merely to obtain the evening wave component of the signal, so it is not necessary to be a Takakurahe bandpass filter as in the conventional example.

As shown in Figures 2 onwards, the frequency-voltage converter F/V compares the intensity of the speckle with the zero level, and generates a pulse train that rises every time the two match and attenuates with a constant time constant. It has the function of converting into an averaged voltage output through a low-pass filter.

In Fig. 1, the output of amplifier A is connected to an analog-to-digital converter A/D, a microcomputer, and a COH.
The output of amplifier A is input to the spectrum analysis and correlator SPC/COH, which is used to check the statistical distribution as necessary. This is used to plot and confirm that the value has decreased.

Now, the output of the photoelectron amplifier tube PM or amplifier A is shown in FIG. FIG. 2(a) shows a case where the change in the received light intensity I with respect to time changes is large, and FIG. 2(b) shows a case where the change in the received light intensity I with respect to time changes is small. Figure 3 (a
) and (b) respectively compare the received light outputs in FIGS. 2(a) and 2(b) with the zero level, and show a state in which a pulse is generated when the fluorescence output and the zero level match.

Since this pulse attenuates with a predetermined time constant, the fourth
As shown in Figures (a) and (b), a high voltage (di V) is output when the pulse repetition frequency is high. Therefore, by integrating this output between The integral E1 will display the repetition frequency of the pulse for a predetermined time.In this way, if the blood flow state of the area to be measured is fast, the integral value will be displayed high, and conversely, if the blood flow state is slow, the integral value will be displayed low. will be done.

In FIG. 1, when the core diameters of the optical fibers F1 and F2 become thicker, spatial integration of speckles is performed, the direct current component increases, and mortal noise comes into play. Therefore, the optical fiber F1. The core diameter of F2 is 100
gm or less is appropriate.

As described above, according to the present invention, since the zero-crossing method processing is performed, a highly accurate high-pass filter, a divider, etc. are not required, and the blood flow state of a living tissue can be measured with a simple configuration.

The present invention can be used in the medical and surgical fields to diagnose peripheral circulatory insufficiency and evaluate pathological conditions5, and in the field of plastic surgery to measure the countercurrent state after skin and tributary transplants, and to improve transplant surgery. The progress can be easily judged.

[Brief explanation of the drawing]

Figure 1 is an overall schematic diagram of the laser speckle blood flow λ1 according to the present invention, Figures 2 (a) and (b) are temporal changes in the received light output, and Figures 3 (a) and (b) are the received light. Figure 4 (a), (b) is an explanatory diagram of the state in which the output and zero level are compared and a pulse is generated when the received light output and zero level match.
is a voltage distribution diagram obtained by performing time integration using a frequency-voltage converter. In the figure, Fl is a light emitting fiber and F2 is a light receiving fiber.
1LB is a laser light source, PM is a photoelectron amplifier tube, A is an amplifier, FL is a high-pass filter, and F/V is a frequency-voltage converter.

Claims (1)

[Claims] 1. A laser light source, a light-emitting fiber that irradiates light from the laser light source to blood cells in a living tissue, and a light-receiving fiber that transmits a laser speckle signal that changes over time from the blood cells in the living tissue. and a photodetector that detects the speckle light intensity transmitted by the light receiving fiber.
The speckle light intensity detected by the photodetector is compared with a predetermined level, and each time the two match, a pulse train is generated that rises and decays with a certain time constant, and is further passed through a low-pass filter to generate an averaged voltage output. Frequency to convert to -
A laser speckle blood flow meter characterized by having a voltage converter. 2. Claim t! where the predetermined level for comparing the speckle light intensity is zero level! The laser speckle blood flow meter described in Section JJ1.