CN202078295U

CN202078295U - Near-infrared laser system for inspecting deep vein thrombosis

Info

Publication number: CN202078295U
Application number: CN2010202135477U
Authority: CN
Inventors: 谭伟
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-06-01
Filing date: 2010-06-01
Publication date: 2011-12-21
Anticipated expiration: 2020-06-01

Abstract

The utility model relates to a piece of near infrared laser inspection equipment for improving a signal to noise ratio by utilizing a spread spectrum technique so as to increase a laser penetration depth, wherein the equipment is used for early-period inspection of deep vein thrombosis on human body. The equipment comprises a digital signal generator, a pseudorandom sequence generation circuit, a programmable analog signal generation chip, a laser diode stabilizing drive circuit, a multi-wavelength laser diode component, a high voltage biasing circuit, a photomultiplier, a low noise amplifier, a matched filter, a quadrature demodulator and the like. The equipment which is in contact with the human body by a probe transmits modulated multi-wavelength laser signals to human tissues, and receives the signals scattered and reflected through the human tissues by the photomultiplier in the probe. The equipment increases the signal to noise ratio by employing the spread spectrum technique, so that the infrared laser technique can greatly increase the depth achieved by the laser signals in a safe laser power range, and a more significant clinical inspecting effect is obtained.

Description

Be used to check the near-infrared laser system of deep venous thrombosis

Technical field

This utility model belongs to technical field of medical instruments, is specifically related to be used for the optical check technology of deep venous thrombosis.

Background technology

Deep venous thrombosis is meant that blood condenses at dark intravenous improperly, belongs to veins of lower extremity backflow obstacle disease.After the thrombosis, except that minority can melt or be confined to the happening part voluntarily, major part can diffuse to the dark vein trunk of whole limbs, if can not in time diagnose and handle, majority can develop into the thrombosis sequela, influences patient's quality of life for a long time; Also have the concurrent pulmonary infarction of some patients' possibilities, cause very serious consequence.

The basic dependent imaging technology of detection of present deep venous thrombosis is X-ray contrast imaging and ultrasonic for example.But the former is influential to patient health, complication is many, is not suitable for early stage inspection, latter's poor specificity is difficult to diagnose in early days.Noctovision shooting thermograph diagnosis thrombophlebitis and phlebothrombosis are very sensitive but do not have specificity, and cost an arm and a leg complicated operation.

Near infrared light learns a skill because its Noninvasive can be used to judge simultaneously that the shank venous blood is detained situation, to the good specificity and the sensitivity of blood characteristics.Yet because scattering and the absorption of near infrared light in tissue, penetration capacity is very limited.Simultaneously since body surface, penetrates the body inscattering to the restriction of light intensity and generally be difficult to reach 2 centimetres by the near infrared light that pick off received, can do efficient diagnosis beyond tissues.Therefore this technology is often powerless than the blood vessel of depths to shank.The conditional main cause of the depth of penetration is because increase the amplitude of optical signal decays with the trend near 10dB/ centimetre with the degree of depth, and optical noise and electronic noise and unattenuated finally cause signal to noise ratio to reduce.

The utility model content

This utility model comprises that a multi-wavelength near-infrared laser transmits and receives system, can transmit and receive the near-infrared laser of multi-wavelength to the leg tissue timesharing, and by adopting the passage spread spectrum technique to suppress influence of noise transmitting and receiving of signal, thereby make laser signal under the prerequisite of power limited, can still keep signal to noise ratio preferably, detect the technology for eliminating obstacle for this technology can be applied to dark vein in the darker zone of human body.

The technical scheme that its technical problem that solves this utility model adopts is to utilize spread spectrum technique by pseudo random code the near-infrared laser of being launched to be carried out high frequency modulated, transmitting of certain energy expanded to very wideband section on frequency domain, thereby the power density on certain frequency reduces significantly.When the receiving terminal of getting back to instrument through the optical signal and the noise of tissue, can be once more the signal of spread-spectrum be returned to signal significantly on the single-frequency by spectrum recovery.Laser signal has passed through twice modulation and noise signal is only once modulated in receive path in this process, so signal is restored and noise is inhibited.

This utility model provides a kind of near-infrared laser system that is used to check deep venous thrombosis, comprises digital signal processor, pseudo-random sequence generator, programmable analog signal generation chip, laser diode driver circuit, laser diode module, radio frequency low-noise amplifier, photomultiplier tube and matched filter; Described digital signal processor produces a high frequency clock signal; Described pseudo-random sequence generator produces and the synchronous pseudo-random sequence of this high frequency clock signal; Described programmable analog signal generation chip receives by digital signal processor and the high frequency clock signal of pseudo-random sequence generator generation and synchronous pseudo-random sequence, and the synthetic spread spectrum signal that produces; Described laser diode driver circuit receives this spread spectrum signal, and the driving laser diode assembly; Laser signal of scattering and reflection from tested tissue is gathered by described photomultiplier tube, this signal is sent to radio frequency low-noise amplifier amplify; Last signal is handled and is modulated once more with restoring signal with pseudorandom code sequence through matched filter, extracts the phase place and the amplitude of signal.

Described laser diode driver circuit adopts temperature and light intensity two-fold feedback and hardware PID control circuit to obtain the high stability laser output of intensity.

Described system further comprises quadrature demodulator, and it will carry out demodulation through the radio frequency low-noise amplifier amplifying signal, obtains orthogonal IQ signal and offers digital signal processor calculating amplitude and phase place.

Described laser diode module is made up of the laser diode of a plurality of wavelength, is driven by the timesharing of DSP CONTROL switch.

The beneficial effects of the utility model are, utilize the laser sending/receiving system of spread spectrum technique to improve the signal to noise ratio that surpasses 40dB than general near-infrared system, thereby can reliably but perceived depth be expanded to more than 4.5 centimetres, thereby detect most of deep venous thrombosis focus effectively.

Description of drawings

Below in conjunction with drawings and Examples this utility model is further specified.

Fig. 1 is the system structure of multi-wavelength spread-spectrum near-infrared laser detecting instrument.

Fig. 2 is the signal of signal processing flow

Fig. 3 is the signal of signal extension frequency spectrum

Fig. 4 is the signal of multi-wavelength spread-spectrum near-infrared laser detection system in clinical use

The specific embodiment

Fig. 1 is an instrument system structure chart of the present utility model.It makes master control unit and signal processing by a digital signal processor 1, and it at first produces a high frequency clock signal, as 70MHz, and synchronous pseudo-random sequence.Pseudo-random sequence generator 2 can be the part of digital signal processor 1, or external chip such as CPLD produce.Pseudo-random sequence and clock signal synchronous are sent to programmable analog signal generation chip 3, by its synthetic spread spectrum signal that produces, pass to laser diode driver circuit 4.Laser diode driver circuit 4 drives near-infrared laser diode assembly 5, and adopts temperature and light intensity two-fold feedback and hardware PID control circuit to obtain the high stability laser output of intensity.Driving laser diode assembly 5 is made up of the laser diode of a plurality of wavelength, is driven by digital signal processor 1 gauge tap timesharing.Laser signal of scattering and reflection from tested tissue is had the high sensitivity photomultiplier tube 6 of HVB high voltage bias to be gathered, and it is big to send to 7 of multi-level radio-frequency low-noise amplifiers, to obtain the gain more than the 60dB.Signal after the amplification further passes through quadrature demodulator 8 demodulation, obtains orthogonal IQ signal, with the phase place and the amplitude of while reflected signal.The Phase synchronization information reference by programmable analog signal generation chip 3 that provide with pseudo-random sequence and original clock signal clock signal synchronous and clock signal that 90 degree phase shift are arranged.Last signal process matched filter, the correlation function of acquisition and former pseudo-random sequence, but according to time-delay value and the amplitude fading value of its peak value adjustment picked up signal with respect to emission.Because the effect of correlation function, the signal that is expanded on frequency domain are concentrated again.This Direct swquence spread spectrum technology is on ultimate principle, because signal is restored through twice modulation of pseudo noise code, and the noise that midway enters is because to be extended to energy density by primary modulation lower, thereby can significantly improve signal to noise ratio.

Signal hint everywhere such as Fig. 2 in the time of instrument work.Can be used as the reference phase signal of system with the synchronous sinusoidal signal 10 of signal processor original clock.The pseudo-random signal sequence 11 that pseudo-random signal sequencer 2 produces is with synchronous with sinusoidal signal 10.Each pseudo-random signal sequence bit is corresponding to the cycle of one or several sinusoidal signal 10.Every cycle in Fig. 2 corresponding to 2 sinusoidal signals 10.There is longer recovery time in the long more system that then allows of corresponding periodicity when modulation, still just long more corresponding to the time of a pseudo-random sequence.Need be compromise during realization according to practical situation.Programmable analog signal chip 3 is done the phase code modulation with signal 10 usefulness pseudo-random sequences 11, produces spread-spectrum signal 12.Because the broader bandwidth of pseudo-random sequence 11, therefore the spread-spectrum signal 12 after the modulation also no longer is the single-frequency signals as sinusoidal signal 10, but frequency distribution is near the broadband signal of pseudo-random sequence 11.Spread-spectrum signal 12 is very faint on amplitude through the signal 13 after being accepted by photomultiplier tube after the tissue by laser diode emission, simultaneously because the effect of tissue produces hysteresis in time, causes and 12 the phase contrast θ of transmitting.There have been at present scientific discovery and mature technology to realize diagnosing deep venous thrombosis with being included in the signal 13 variation of amplitude and phase contrast θ.In order accurately to record phase contrast θ and amplitude of variation, system seeks optimum phase difference by matched filter according to correlation function after amplifying with 7 pairs of signals 13 of low-noise amplifier.With spread spectrum with any single frequency signal energy spread on wideband section very, the correlation function signal energy on the section for a long time is gathered in a bit, thereby obtains very high signal to noise ratio at this point.The length of pseudo noise code 11 is long more, and this effect is just big more, but each time of detecting is just long more, and corresponding detection signal is just slow more.Therefore need design the length of pseudo noise code 11 according to the trade-off of speed that clinical signal changes.System produces clock 14 and the corresponding orthogonal clock of being with phase contrast θ by programmable analog signal generation chip 3 again after obtaining phase contrast θ.They are by signal 13 quadrature demodulations after 9 pairs of amplifications of IQ quadrature demodulator, picked up signal 15.System once more with the pseudo-random sequence of Tape movement phase contrast θ to signal 15 demodulation and carry out low-pass filtering, obtain IQ level at last corresponding to received signal.Digital signal processor is by the amplitude and the phase place of IQ level signal calculated.

Fig. 3 has shown that initial simple signal 10 becomes the signal 19 of wideband low energy densities after the state 18 of frequency domain is by pseudo-random sequence 11 spread spectrums.In the relevant treatment of receiving terminal matched filter signal being reverted to again with pseudo noise code length is the high peak signal in cycle.Noise is low-level owing to there not being dependency still to keep after relevant treatment.But the signal to noise ratio increasing degree 22 thus.

Fig. 4 has illustrated the state that instrument 25 is waited in use.Band emission laser diode assembly 24 and reception photomultiplier tube 28 probe and the shank 23 of human body closely contact.The intermediary direct path between luminescent material will transmit and receive of popping one's head in separates.And shield member 26 separates and transmits and receives crosstalking between circuit.The multiwavelength laser of laser diode module 24 emissions produces phase shift and decay through dark vein 29, is received by photomultiplier tube 28 at last.Signal obtains the pathological information of dark vein 29 after above the processing.

Claims

1. near-infrared laser system that is used to check deep venous thrombosis, it is characterized in that, comprise digital signal processor, pseudo-random sequence generator, programmable analog signal generation chip, laser diode driver circuit, laser diode module, radio frequency low-noise amplifier, photomultiplier tube and matched filter; Described digital signal processor produces a high frequency clock signal; Described pseudo-random sequence generator produces and the synchronous pseudo-random sequence of this high frequency clock signal; Described programmable analog signal generation chip receives by digital signal processor and the high frequency clock signal of pseudo-random sequence generator generation and synchronous pseudo-random sequence, and the synthetic spread spectrum signal that produces; Described laser diode driver circuit receives this spread spectrum signal, and the driving laser diode assembly; Laser signal of scattering and reflection from tested tissue is gathered by described photomultiplier tube, this signal is sent to radio frequency low-noise amplifier amplify; Last signal is handled and is modulated once more with restoring signal with pseudorandom code sequence through matched filter, extracts the phase place and the amplitude of signal.

2. the system as claimed in claim 1 is characterized in that, described laser diode driver circuit adopts temperature and light intensity two-fold feedback and hardware PID control circuit to obtain the high stability laser output of intensity.

3. the system as claimed in claim 1 is characterized in that, further comprises quadrature demodulator, and it will carry out demodulation through the radio frequency low-noise amplifier amplifying signal, obtains orthogonal IQ signal and offers digital signal processor calculating amplitude and phase place.

4. the system as claimed in claim 1 is characterized in that, described laser diode module is made up of the laser diode of a plurality of wavelength, is driven by the timesharing of DSP CONTROL switch.