Bone density measurement device and method based on photoacoustic signal

Abstract

The present invention belongs to the technical field of bone density detection, and specifically is a bone density measurement device and method based on photoacoustic signals. The device of the present invention includes a computer, a laser, a transmission control circuit, a translation controller, an ultrasonic transducer, a signal amplifier and an analog-to-digital converter; the computer controls the laser to emit a pulsed laser and move in the horizontal direction through the transmission control circuit and the translation controller, so that the pulsed laser irradiates the bone tissue to be measured, and receives the ultrasonic signal generated by the photoacoustic effect through the ultrasonic transducer, and stores it in the computer through the signal amplifier and the analog-to-digital converter for analyzing and calculating the bone density information. The present invention obtains the bone density information between the two measurement areas by comparing and analyzing the photoacoustic signals at different positions of the bone tissue. The present invention has the advantages of being non-traumatic, non-radiative, and not being interfered by the skin and soft tissue, and can provide detailed information on bone density at different positions.

Description

Technical Field

[0001] The present invention belongs to the technical field of bone density detection, and in particular relates to a bone density measurement device and method based on photoacoustic signals. Background Art

[0002] Osteoporosis is a systemic bone metabolic disease, which is mainly manifested by bone loss and microstructural degeneration, leading to an increased risk of fractures. More than 200 million people worldwide suffer from osteoporosis. The increasing aging of modern society has made osteoporosis receive more and more attention. Osteoporosis seriously affects the quality of life of the public, and osteoporotic fractures have imposed a great economic burden on society. Therefore, early diagnosis and timely treatment of osteoporosis are of great significance.

[0003] At present, bone density evaluation is mainly based on X-ray bone density absorption measurement technology, such as X-rays, single and double photon absorption methods, quantitative CT and dual-energy X-ray method (DXA). X-ray bone density absorption measurement equipment is large and has radioactive damage. It can only provide bone mineral density (BMD) and cannot fully reflect bone density information. Ultrasonic bone densitometer is a device based on quantitative ultrasound technology (QUS) to evaluate bone density. It mainly uses ultrasound transmission method, ultrasound backscattering method and ultrasound axial transmission method, etc., and indirectly reflects bone density information by analyzing the characteristics of ultrasound propagation, attenuation and scattering in bone tissue. Ultrasonic bone densitometer has the advantages of safety, non-destructiveness, no ionizing radiation and portability. It mainly measures the calcaneus, tibia and phalanges. Patent 1 "Ultrasonic Bone Density Measurement and Analysis System" (CN101401732A) is based on the ultrasonic transmission method to measure the calcaneal thickness, ultrasonic propagation velocity and broadband ultrasonic attenuation of the subject, and calculate the bone strength index and bone density; Patent 2 "A Bone Density Analyzer and Its Control Circuit" (CN111265249A) uses an ultrasonic axial transmission method to measure the ultrasonic sound velocity of bone tissue and obtain the bone density of the bone to be tested; Patent 3 "Ultrasonic Probe for Quantitative Measurement of Bone Mineral Density" (CN1969762A) uses a measuring probe and two positioning probes to measure the propagation velocity of ultrasonic shear waves in the bone to reflect the bone mineral density information; Patent 4 "Method and Device for Non-Invasive Evaluation of Bone" (CN1596084A) uses ultrasonic guided wave method to measure cortical thickness, bone density, bone elastic constant and other information to evaluate bone condition; Patent 5 "A Backscattering Ultrasonic Bone Diagnostic System" (CN105796131A) uses ultrasonic backscattering method to analyze ultrasonic scattering characteristics to evaluate bone condition. Patents 1-5 are bone density diagnostic devices and methods based on quantitative ultrasound technology, which can only provide the average bone density of bone tissue in the ultrasound conduction path, and the measurement is easily interfered by soft tissues such as skin.

[0004] Photoacoustic technology is an emerging bone density assessment technology that is safe and radiation-free. Photoacoustic technology uses the thermal elastic expansion of biological tissues such as bones under the irradiation of pulsed lasers to generate ultrasonic signals to reflect the bone condition. Photoacoustic technology is more sensitive to the chemical composition of bone tissue (such as collagen, etc.), and mainly analyzes the spectrum and energy of the photoacoustic signal of bone tissue to reflect the bone density condition. Patent 6 "A photoacoustic and ultrasonic dual-mode osteoporosis detection method and device" (CN106037818A) proposes to use photoacoustic technology to measure bone collagen and ultrasound technology to measure bone density, so as to improve the ability to evaluate bone quality; Patent 7 "A method for evaluating bone elastic modulus using photoacoustic time domain signals" (CN111110190A) evaluates the bone elastic modulus information of cancellous bone based on the theoretical relationship between photoacoustic time domain signals and cancellous bone elastic modulus; U.S. Patent 8 "Detection, diagnosis and monitoring of osteoporosis by a photo-acoustic method" (US9833187B2) generates ultrasonic signals through photoacoustic technology, and analyzes the characteristics of ultrasonic signals conducted in long bones to reflect bone density and bone quality. The photoacoustic technology described in Patents 6-8 is a single-position measurement and analysis, which is easily affected by the coupling of bone tissue and soft tissues such as skin in the photoacoustic signal transmission path, resulting in inaccurate bone density measurement and other problems. Summary of the invention

[0005] The purpose of the present invention is to provide a non-invasive, non-radiation bone density measurement device and method based on photoacoustic signals, aiming to 1) realize bone density measurement at any bone position of interest and provide detailed information of bone density; 2) eliminate the coupling influence and interference of bones and soft tissues in the photoacoustic signal transmission path and improve the accuracy of bone density measurement.

[0006] The bone density measuring device based on photoacoustic signals provided by the present invention comprises a computer, a laser, a transmission control circuit, a translation controller, an ultrasonic transducer, a signal amplifier and an analog-to-digital converter; wherein:

[0007] The laser is used to emit pulsed laser;

[0008] The emission control circuit is used to control the laser to emit pulsed laser;

[0009] The translation controller is used to control the laser to translate in the horizontal direction so that the pulsed laser irradiates different positions of the bone tissue in the horizontal direction;

[0010] The ultrasonic transducer is used to receive the ultrasonic signal generated by the photoacoustic effect; the ultrasonic transducer is located at a horizontal position on the side of the bone tissue to be measured, and the measuring direction of the ultrasonic transducer is consistent with the translation direction of the laser;

[0011] The computer controls the laser to emit pulsed laser and move in the horizontal direction through the emission control circuit and the translation controller, so that the pulsed laser irradiates the bone tissue to be measured, receives the ultrasonic signal generated by the photoacoustic effect through the ultrasonic transducer, and stores it in the computer through the signal amplifier and the analog-to-digital converter for analyzing and calculating the bone density information.

[0012] The present invention provides a method for measuring bone density based on photoacoustic signals. The device first measures an ultrasonic signal (denoted as S) at a certain position A of the bone tissue. A ), and then the pulse laser is moved horizontally by the translation controller to measure the ultrasonic signal at position B near the bone tissue (denoted as S B ), and the bone density information of the AB measurement area is obtained by comparing and analyzing the ultrasonic signals at the two measurement positions.

[0013] In the above method, the normalized broadband ultrasound attenuation (nBUA) of the bone tissue in the AB measurement area is calculated according to the following formula:

[0014]

[0015] Among them, S A (f) and S B (f) The amplitude spectrum of the ultrasonic signal at the two measurement positions A and B, respectively. AB is the distance between the two measurement positions AB, and [f1, f2] is the effective frequency range of the ultrasonic transducer.

[0016] In the above method, the ultrasonic sound velocity (SOS) of the bone tissue in the AB measurement area is calculated according to the following formula:

[0017]

[0018] Among them, d AB is the distance between points AB, T A and T B are the arrival times of the ultrasonic signals at the two measurement positions A and B respectively.

[0019] In the above method, the bone density information (BD) of the AB measurement area can be evaluated by the linear combination parameter of the normalized broadband ultrasound attenuation nBUA and the ultrasound sound speed SOS, that is:

[0020] BD=k1·nBUA+k2·SOS+k3

[0021] Among them, BD is the bone density value measured in bone tissue, k1, k2, k3 are unknown coefficients, and the specific values ​​can be obtained by multiple linear regression analysis (bone density is the dependent variable, nBUA and / or SOS are the independent variables).

[0022] Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) Non-invasive and non-ionizing radiation, the present invention is safer than traditional X-ray bone density absorption measurement;

[0024] (2) Providing detailed information on bone density. Compared with quantitative ultrasound technology, the present invention can measure bone density at any bone location of interest;

[0025] (3) High accuracy of bone density measurement. Compared with the photoacoustic technology of single-position measurement, the present invention eliminates the coupling effect of bone tissue and soft tissue in the ultrasonic conduction path by comparing the photoacoustic signals of two adjacent positions, thereby significantly improving the accuracy of bone density measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural block diagram of the bone density measuring device based on photoacoustic signals of the present invention.

[0027] The numbers in the figure are: 1 is a computer, 2 is a transmission control circuit, 3 is a translation controller, 4 is a laser, 5 is a bone tissue to be measured, 6 is an ultrasonic transducer, 7 is a signal amplifier, and 8 is an analog-to-digital converter. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0029] like Figure 1 As shown, the present invention provides a bone density measuring device based on photoacoustic signals, comprising a computer (1), an emission control circuit (2), a translation controller (3), a laser (4), bone tissue to be measured (5), an ultrasonic transducer (6), a signal amplifier (7), and an analog-to-digital converter (8).

[0030] The device of the present invention requires that the translation controller (3) can control the laser (4) to translate in the horizontal direction, so that the pulsed laser irradiates different positions of the bone tissue (5) in the horizontal direction.

[0031] The device of the present invention requires that the ultrasonic transducer (6) is located at a horizontal position on the side of the bone tissue (5) to be measured, and the measuring direction of the ultrasonic transducer (6) is consistent with the translation direction of the laser (4).

[0032] The measurement method of the bone density measurement device based on photoacoustic signals of the present invention is specifically as follows:

[0033] The computer (1) controls the laser (4) to emit pulsed laser through the emission control circuit (2) and the translation controller (3). The laser is in the near-infrared region, with a wavelength of 800nm, a pulse width of 5ns, a pulse repetition frequency of 20Hz, and a spot diameter of 2mm. The pulsed laser is irradiated to the measurement position A of the bone tissue (5) to be measured. The bone tissue absorbs the laser to generate thermal elastic expansion and mechanical vibration (ultrasound is a mechanical vibration wave), and generates ultrasound through the photoacoustic effect. An ultrasonic transducer (6) with a center frequency of 5MHz is used to receive the ultrasonic signal, which is amplified by 20dB through the signal amplifier (7). The analog-to-digital converter (8) collects the data and stores it in the computer (1). The ultrasonic signal at position A is recorded as S A .

[0034] Then, the laser (4) is moved horizontally by a translation controller (3) for a short distance to measure the ultrasonic signal at position B near the bone tissue, which is recorded as S B , the bone density information of the AB measurement area is obtained by comparing and analyzing the ultrasonic signals at the two measurement positions.

[0035] Photoacoustic signal of bone tissue (S A or S B ) mainly depends on: the characteristics of the emitted laser (spectrum, energy, etc.), the bone properties (bone structure and composition) of the laser irradiation area (position A or position B), the ultrasonic propagation coupling effects such as reflection, scattering and absorption of bone tissue and soft tissue on the ultrasonic conduction path, and the signal receiving characteristics of the ultrasonic transducer.

[0036] Considering that A and B are two adjacent measurement points, the bone density in the small area is continuous, that is, assuming that the bone properties of the two measurement positions A and B are consistent, and because the characteristics of the emitting laser and receiving ultrasonic transducers are the same, then the signals S of the two measurement positions A and B are A and S B The difference mainly comes from the different attenuation coupling effects on the ultrasonic conduction path (mainly reflected in the distance difference of the coupling path, that is, the distance d between points AB AB ).

[0037] Based on the above, the normalized broadband ultrasound attenuation (nBUA) of bone tissue in the AB measurement area is:

[0038]

[0039] Among them, S A (f) and S B (f) The amplitude spectrum of the ultrasonic signal at the two measurement positions A and B, respectively. AB is the distance between the two measurement positions AB, and [f1, f2] is the effective frequency range of the ultrasonic transducer.

[0040] Based on the above, the ultrasonic sound velocity (SOS) of the bone tissue in the AB measurement area is:

[0041]

[0042] Among them, d AB is the distance between points AB, T A and T B are the arrival times of the ultrasonic signals at the two measurement positions A and B respectively.

[0043] Within a certain range, normalized broadband ultrasound attenuation nBUA and ultrasound sound velocity SOS are positively correlated with bone density: that is, the greater the bone density, the greater the nBUA and SOS. Therefore, the bone density information of the measurement area can be reflected by the nBUA and / or SOS parameter values.

[0044] The present invention proposes nBUA and / or SOS combined parameters to evaluate the bone density information (BD) of the AB measurement area.

[0045] BD=k1·nBUA+k2·SOS+k3

[0046] Wherein, BD is the bone density measured by bone tissue, k1, k2, k3 are unknown coefficients, and their specific values ​​can be obtained by multiple linear regression analysis (bone density is the dependent variable, nBUA and / or SOS are independent variables), k1 and k2 cannot be 0 at the same time, and k3 is a constant term and can be 0.

[0047] The present invention discloses a bone density measurement device and method based on photoacoustic signals. By comparing the photoacoustic signals of two adjacent measurement positions, the bone density information of the measured bone area is reflected, which not only realizes the detailed measurement of bone density at any bone position of interest, but also eliminates the coupling influence of bone tissue and soft tissue in the ultrasonic conduction path, thereby significantly improving the accuracy of bone density measurement.

[0048] The above description is a specific implementation example of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical scope and technical solutions disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. A bone density measurement device based on photoacoustic signals, characterized in that: It includes a computer, a laser, a launch control circuit, a translation controller, an ultrasonic transducer, a signal amplifier and an analog-to-digital converter; wherein: The laser is used to emit pulsed laser; The emission control circuit is used to control the laser to emit pulsed laser; The translation controller is used to control the laser to translate in the horizontal direction so that the pulsed laser irradiates different positions of the bone tissue in the horizontal direction; The ultrasonic transducer is used to receive the ultrasonic signal generated by the photoacoustic effect; the ultrasonic transducer is located at a horizontal position on the side of the bone tissue to be measured, and the measuring direction of the ultrasonic transducer is consistent with the translation direction of the laser; The computer controls the laser to emit pulsed laser and move in the horizontal direction through the emission control circuit and the translation controller, so that the pulsed laser irradiates the bone tissue to be measured, receives the ultrasonic signal generated by the photoacoustic effect through the ultrasonic transducer, and stores it in the computer through the signal amplifier and the analog-to-digital converter for analyzing and calculating the bone density information; The specific steps of the device measurement are as follows: First, the ultrasonic signal at a certain position A of the bone tissue is measured, denoted as S A ; Then, the pulse laser is moved horizontally by the translation controller to position B adjacent to position A, and the ultrasonic signal of the bone tissue at position B is measured, which is recorded as S B ; Compare and analyze the ultrasonic signals at the two measurement positions to obtain the bone density information of the AB measurement area; The calculation method of the bone density information of the AB measurement area is as follows: Calculate the normalized broadband ultrasound attenuation nBUA of bone tissue in the AB measurement area: ； in, and are the amplitude spectra of the ultrasonic signals at the two measurement positions A and B, respectively, AB is the distance between the two measurement positions AB, is the effective frequency range of the ultrasonic transducer; Calculate the ultrasonic sound velocity SOS of the bone tissue in the AB measurement area: ； Among them, d AB is the distance between points AB, T A and T B are the arrival times of the ultrasonic signals at the two measurement positions A and B respectively; Calculate the bone density information BD of the AB measurement area: ； Among them, k1, k2, k3 are unknown coefficients, and BD is the bone density value measured in bone tissue.

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