An apparatus and method for detecting blood triglyceride concentration using photoacoustic microscopy

Abstract

This invention discloses a device and method for detecting triglyceride concentration using photoacoustic microscopy, relating to the field of blood lipid detection. The device splits a pulsed laser beam into two beams after passing through a beam splitter. One beam enters a photodetector, and its output electrical signal serves as the trigger signal for a digital converter. The other beam is coupled to a multimode fiber optic patch cord via a lens group, and its outgoing light is used to excite a photoacoustic signal. The detection module includes a focused ultrasound probe, an amplifier, and a digital converter. The focused ultrasound probe receives the photoacoustic signal and is constructed by connecting an acoustic lens to a planar ultrasound transducer. The imaging head scans the sample using a two-dimensional electrically controlled displacement platform. The concentration of triglycerides in the blood is obtained by analyzing the detected photoacoustic signal. This invention enables non-invasive, convenient, and rapid detection of triglyceride concentration in the blood.

Description

Technical Field

[0001] This invention relates to the field of blood lipid detection, and more particularly to an apparatus and method for detecting blood triglyceride concentration using photoacoustic microscopy. Background Technology

[0002] Blood lipids are mainly composed of triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), and their concentration has significant implications for human health. Hypertriglyceridemia (TG levels >150 mg / dL) increases the risk of cardiovascular disease. Furthermore, severe hypertriglyceridemia (TG levels >1000 mg / dL) increases the risk of cardiovascular events and acute pancreatitis, threatening human life.

[0003] Typically, triglyceride (TG) levels in the blood are measured and determined through a lipid panel blood test, which requires a blood draw and can be painful. Therefore, traditional lipid monitoring methods are inconvenient for routine monitoring and reduce the willingness of potential patients to undergo the test. Furthermore, after the blood draw, hospitals or specialized laboratories need at least several hours to report the results based on biochemical analysis, which may delay treatment. Therefore, there is an urgent need to develop a non-invasive, convenient, and rapid method for detecting TG concentrations in the blood.

[0004] Optical imaging technology is commonly used for non-invasive monitoring of health signs and disease diagnosis. Among these, photoacoustic imaging (PAI), combining the high optical contrast based on light absorption with the large penetration depth of ultrasound detection, has received increasing attention and extensive research in recent years. PAI can be divided into three categories: photoacoustic computed tomography (PACT), acoustic resolution photoacoustic microscopy (AR-PAM), and optical resolution photoacoustic microscopy (OR-PAM). PAI can be used for subcutaneous vascular imaging, breast tumor imaging, blood oxygen saturation mapping, and melanoma imaging. Some literature also reports that PAI can be used to detect lipid content based on laser irradiation at a wavelength of approximately 1210 nm; however, this is mostly limited to imaging subcutaneous tissue lipid content or lipid-rich plaques, and there are currently no studies on using PAI to measure blood lipid concentrations, especially triglyceride concentrations in the blood.

[0005] Therefore, those skilled in the art are dedicated to developing a device and method for detecting blood triglyceride concentration using photoacoustic microscopy. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to develop a non-invasive, convenient and rapid method for detecting TG concentration in blood.

[0007] To achieve the above objectives, this invention provides a photoacoustic microscopic imaging device for detecting blood triglyceride concentration, comprising an optical path module, a sample stage module, an imaging head, and a detection module. The optical path module includes a pulsed laser, a beam splitter, a lens group, and an optical fiber. The sample stage module includes a water tank, a sample, a three-dimensional platform, and a two-dimensional electrically controlled displacement platform. The pulsed laser is split into two beams by the beam splitter. One beam enters a photodetector, and its output electrical signal serves as the trigger signal for a digital converter. The other beam is coupled to a multimode fiber optic patch cord via the lens group, and its outgoing light is used to excite a photoacoustic signal. The detection module includes a focused ultrasound probe, an amplifier, and a digital converter. The focused ultrasound probe receives the photoacoustic signal and is constructed by connecting an acoustic lens to a planar ultrasound transducer. The imaging head consists of a laser illumination section and an acoustic detection section. During image acquisition, the imaging head scans via the two-dimensional electrically controlled displacement platform. The detected photoacoustic signal is amplified by a low-noise preamplifier, recorded by the digital converter, and then stored in a computer. The sample is placed in the water tank.

[0008] Preferably, the acoustic lens has a numerical aperture of 0.44 and a focal length of 6.7 mm.

[0009] Preferably, the laser illumination part of the imaging head is an optical fiber; the acoustic detection part is a focused ultrasound probe.

[0010] Preferably, the lateral and axial resolutions of the photoacoustic microscopy device for detecting blood triglyceride concentration are approximately 65 μm and 40 μm, respectively.

[0011] Preferably, the sample is a blood solution, and the spotting capillaries are fixed side by side on a coverslip.

[0012] Preferably, the capillary has an inner diameter of 500 μm and an outer diameter of 700 μm.

[0013] Preferably, the sample is positioned using the three-dimensional platform.

[0014] Preferably, the samples are tested in groups of seven.

[0015] Preferably, the sample stage module further includes a pump flow system.

[0016] This invention also provides a photoacoustic microscopy imaging method for detecting blood triglyceride concentration, comprising:

[0017] Step 1: Seven blood solutions were prepared, consisting of lyophilized hemoglobin (Hb) powder, triglycerides, and deionized water, to create final blood solutions with different triglyceride concentrations. Then, seven spotting capillaries filled with the seven blood solutions were sealed at both ends, fixed side by side on coverslips, and placed in a water tank for imaging experiments.

[0018] Step 2: Photoacoustic excitation is performed using a pulsed laser. After passing through a beam splitter, the laser beam is split into two beams. One beam enters a photodetector, and its output electrical signal serves as the trigger signal for the digital converter. The other beam is coupled to a multimode fiber optic patch cord via a lens group, and its outgoing light is used for photoacoustic signal excitation. A focused ultrasound probe receives the photoacoustic signal. The focused ultrasound probe is made by connecting an acoustic lens to a planar ultrasound transducer. Then, the signal and image acquisition process is performed.

[0019] Step 3: During image acquisition, the imaging head, consisting of a laser illumination section and an acoustic detection section, is scanned by a two-dimensional electronically controlled displacement platform; the detected photoacoustic signal is amplified by a low-noise preamplifier, recorded by a digital converter, and then stored in a computer; at the same time, the sample is placed in a water tank, and the sample can be positioned by a three-dimensional platform.

[0020] Technical effect

[0021] The photoacoustic microscopy method proposed in this invention can achieve non-invasive detection of triglyceride (TG) concentration in blood lipids and continuously monitor TG concentration, while also rapidly obtaining detection results. Attached Figure Description

[0022] Figure 1 It is a homemade AR-PAM system;

[0023] Figure 2 This is a representative photoacoustic micrograph of blood solutions (based on Hb lyophilized powder) at seven different TG concentrations (0 mg / dL, 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, 4500 mg / dL and 9000 mg / dL);

[0024] Figure 3 This describes the relationship between normalized photoacoustic amplitude and different triglyceride (TG) concentrations (0 mg / dL, 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, 4500 mg / dL, and 9000 mg / dL) in blood solutions (based on Hb lyophilized powder). Data are expressed as mean ± standard deviation.

[0025] Figure 4These are photoacoustic micrographs of a pure hemoglobin (Hb) solution (Hb concentration: 150 mg / mL) and seven different triglyceride (TG) concentrations (TG concentrations: 0 mg / dL, 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, 4500 mg / dL and 9000 mg / dL; belonging to pure triglycerides).

[0026] Figure 5 This describes the relationship between normalized photoacoustic amplitude and the differences in triglyceride (TG) concentrations in flowing sheep blood (0 mg / dL (sample #1), 300 mg / dL (sample #2), 850 mg / dL (sample #3), and 1850 mg / dL (sample #4). Note: The "triglyceride concentration difference" referred to here means the triglyceride concentration compared to sample #1. Data are expressed as mean ± standard deviation. Detailed Implementation

[0027] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0028] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0029] Two experiments were conducted using blood solutions based on Hb lyophilized powder and flowing sheep blood.

[0030] For the first experiment, we prepared seven blood solutions, each composed of hemoglobin (Hb), triglycerides (TG), and deionized (DI) water, for in vitro imaging. Specifically, Hb lyophilized powder (R010156, Rhawn) was first dissolved in deionized water, and then seven different amounts of TG (Structural Fat Emulsion Injection, Fresenius Kabi Ltd) were added to prepare final blood solutions with different TG concentrations. In all seven blood solutions, the Hb concentration was maintained at 150 mg / mL (the normal Hb concentration in blood), while the TG concentrations were set to 0 mg / dL, 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, 4500 mg / dL, and 9000 mg / dL. Seven spotting capillaries (inner diameter: 500 μm; outer diameter: 700 μm), filled with the seven blood solutions, were then fixed side-by-side on coverslips and placed in a water bath for imaging experiments. Note that both ends of the capillary tube are sealed, and the sealed capillary tube is immersed in water to facilitate acoustic coupling. A total of 8 replicate experiments were performed. That is, 8 × 7 tubes of blood solution were prepared, and then photoacoustic imaging was performed 8 times to ensure reliable results. Please note that 150 mg / dL is the upper limit of normal TG levels in blood. When the blood TG level is greater than 150 mg / dL, hypertriglyceridemia can be diagnosed, and when the blood TG level is greater than 1000 mg / dL, severe hypertriglyceridemia can be diagnosed.

[0031] For the second experiment, defibrinated sheep blood samples (Shanghai Yuanye Biotechnology Co., Ltd., China) were used. Specifically, four samples with different TG concentrations were prepared, hereinafter referred to as samples #1-#4. For sample #1, a purchased sheep blood sample was used. Then, the TG levels of samples #2-#4 were 300 mg / dL, 850 mg / dL, and 1850 mg / dL higher than those of sample #1, respectively.

[0032] like Figure 1 As shown, a homemade AR-PAM system was used to acquire photoacoustic signals and images. In the AR-PAM system, the first experiment used a 6ns pulsed laser (Qsmart 450, Quantel) with a pulse repetition frequency of 20Hz and a wavelength of 532nm for photoacoustic excitation; another pulsed laser (Spitlight EVO200 OPO Midband, InnoLas, Germany) provided an excitation wavelength of 797nm for the second experiment.

[0033] like Figure 1As shown, the laser beam is split into two beams after passing through a beam splitter. One beam enters a photodetector, and its output electrical signal serves as the trigger signal for a digital converter (CSE1422, Gage). The other beam passes through lenses 1 and 2 and a pinhole for beam expansion, and then is focused by a coupling lens, coupling the light into a multimode fiber optic patch cord (MHP910L02, Thorlabs). Its outgoing light is used to excite a photoacoustic signal. A focusing ultrasound probe is used to receive the photoacoustic signal. The focusing ultrasound probe is made by connecting an acoustic lens (45006, Edmund Optics, NJ) to a 50MHz planar ultrasonic transducer (V214-BC-RM, 77% bandwidth, Panametrics NDT, MA), with a numerical aperture of 0.44 and a focal length of 6.7 mm. The AR-PAM imaging head consists of a laser illumination section (i.e., fiber optic) and an acoustic detection section (i.e., the focusing ultrasound probe), which are fixed together to form the AR-PAM imaging head. During image acquisition, the imaging head can be scanned via a two-dimensional electrically controlled displacement platform. The detected photoacoustic signal is amplified by a low-noise preamplifier (ZFL-500LN+, Mini-Circuits), recorded by a digital converter (CSE1422, Gage), and then stored in a computer.

[0034] The sample was placed in a water tank, and its position could be adjusted using a three-dimensional platform. The lateral and axial resolutions of the AR-PAM system were approximately 65 μm and 40 μm, respectively. Figure 1 The illustration shows the pump flow system used to achieve the flow of sheep blood in the sheep blood experiment.

[0035] For experiments using blood solutions based on Hb lyophilized powder, photoacoustic microscopy images are as follows: Figure 2As shown, the figure contains seven samples with different TG concentrations (0 mg / dL, 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, 4500 mg / dL, and 9000 mg / dL). The photoacoustic amplitude increases with increasing TG concentration. For quantitative analysis, the maximum pixel value per row for each sample was recorded in the photoacoustic micrograph, and the mean and standard deviation for each sample were calculated based on these maximum pixel values. As mentioned earlier, we conducted eight experiments, and the results of these eight experiments were also considered in the analysis. We set the average photoacoustic amplitude of the blood solution with a TG concentration of 0 mg / dL to 1 for normalization. That is, the average photoacoustic amplitude of blood solutions with different TG concentrations was divided by the average photoacoustic amplitude of the blood solution with a TG concentration of 0 mg / dL. The normalized mean photoacoustic amplitudes of blood solutions with TG concentrations of 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, and 4500 mg were 1.0049, 1.0630, 1.1105, 1.2012, 1.3074, and 1.4186 / dL, respectively, and those of 9000 mg / dL were also [not specified]. Figure 3 As shown in the figure. In the statistical analysis, t-tests were used to analyze every two adjacent TG concentrations. Except for the p-value comparing TG concentrations of 0 mg / dL and 150 mg / dL, the p-values ​​for all other groups were less than 0.0001, indicating that photoacoustic analysis can be used to detect TG levels >450 mg / dL (diagnosed as hypertriglyceridemia) and TG levels >1000 mg / dL (diagnosed as severe hypertriglyceridemia). Furthermore, the p-value for comparing TG concentrations of 0 mg / dL and 450 mg / dL was also calculated, and this value was less than 0.0001. The p-value for comparing TG concentrations of 0 mg / dL and 150 mg / dL was 0.444, indicating that they could not be distinguished.

[0036] The initial photoacoustic pressure can be expressed as P0 = Fμ a Γ is used to describe this, where F is the luminous flux incident on the object, and μ is the luminous flux incident on the object. a Γ is the light absorption coefficient of the absorber, and Γ is the Grüneisen coefficient of the object. In our experiment, the luminous flux remains constant. That is... Figure 2 and 3 The changes in photoacoustic amplitude measured in the blood solution are likely due to variations in light absorption and Grüneisen coefficient. For light absorption, the Hb concentration was the same in all seven blood solutions, and under 532 nm laser irradiation, Hb's light absorption was four orders of magnitude greater than that of TG. Therefore, the light absorption of the seven blood solutions was considered to be the same, and the photoacoustic amplitude increased with increasing TG concentration in the blood solution (e.g., [missing information]). Figure 2 and Figure 3The phenomenon observed should not be attributed to light absorption factors. Figure 4 The experimental results verified that TG itself does not generate photoacoustic signals at an excitation wavelength of 532nm.

[0037] The Grüneisen coefficient of the blood solution is the key factor causing the photoacoustic amplitude to increase with increasing TG concentration. First, as mentioned above, luminous flux and light absorption have been ruled out; therefore, only the Grüneisen coefficient remains as a factor that could cause this. Figure 2 and 3 The results were as follows. Secondly, Laufer et al. (IEEE Journal of Selected Topics in Quantum Electronics 16, 600–607 (2010).; Applied Optics 49, 1219-1233 (2010).) reported a linear relationship between the Grüneisen coefficient of the solution and the solute concentration. Therefore, the Grüneisen coefficient of blood solutions increases with increasing TG concentration, which can explain... Figure 3 The photoacoustic amplitude increases with increasing TG concentration. That is, compared to pure Hb solution, the increase in the Grüneisen coefficient can be estimated by the increase in photoacoustic amplitude. For blood solutions with TG concentrations of 150 mg / dL, 450 mg / dL, 1000 mg / dL, 2000 mg / dL, 4500 mg / dL, and 9000 mg / dL, the increases in the Grüneisen coefficient can be estimated as 4.9%, 6.3%, 11.05%, 20.12%, 30.74%, and 41.86%, respectively. Third, the Grüneisen coefficient can be expressed as Γ = βv s 2 / C p C p It is the specific heat related to the light absorber Hb, v s β is the speed of sound, and β is the coefficient of volume expansion. s β is related to TG and water; TG and water are the surrounding environment of the light absorber Hb. The speed of sound v of TG and water... s The speeds of sound are very close (TG is 1462.5 m / s, water is 1482 m / s), so an increase in TG concentration (compared to a decrease in water concentration) will hardly cause a significant change in the surrounding sound speed. For extreme cases, a rough estimate is <0.13% change. On the other hand, the volume expansion coefficient β of TG is 7 × 10⁻⁶. -4 / ℃, approximately the volumetric expansion coefficient of water (~2.14×10). -4 The concentration of TG is approximately 3.3 times that of Hb (at / ℃). Therefore, increasing the TG concentration increases the volume expansion coefficient of the environment surrounding the light absorber Hb, thereby increasing the Grüneisen coefficient of the blood solution and thus increasing the photoacoustic amplitude. Furthermore, in Figure 3 In addition, we also observed that the increase in the normalized photoacoustic amplitude (or Grüneisen coefficient) saturated at high TG concentrations.

[0038] In another embodiment of the invention, compared to experiments based on Hb lyophilized powder, the flowing sheep blood experiment has greater practical clinical significance and can further verify the reliability of the photoacoustic method for measuring blood lipids described in this patent. For the sheep blood experiment, 100 B-scans are collected for each sample. Similar to... Figure 2 and Figure 3 In the processing steps, we record the maximum pixel value of each B-mode image, and then calculate the mean and standard deviation of each sample based on the maximum pixel value. Next, using the average photoacoustic amplitude of sample #1 as a reference (i.e., set to 1), we normalize the average photoacoustic amplitude of the four sheep blood samples. The normalized average photoacoustic amplitudes of samples #1-#4 are 1, 1.0516, 1.1080, and 1.2492, respectively. Figure 5 As shown. It can be seen that similar phenomena can still be observed. Figure 3 The experiment confirmed that the method described in this invention can be used to detect the concentration of blood lipids in flowing animal blood.

[0039] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A photoacoustic microscopic imaging device for detecting blood triglyceride concentration, characterized in that: The system includes an optical path module, a sample stage module, an imaging head, and a detection module. The optical path module comprises a pulsed laser, a beam splitter, a lens group, and an optical fiber. The sample stage module includes a water tank, a sample, a three-dimensional platform, and a two-dimensional electrically controlled displacement platform. The pulsed laser beam is split into two beams by the beam splitter. One beam enters a photodetector, and its output electrical signal serves as the trigger signal for a digital converter. The other beam is coupled to a multimode fiber optic patch cord via the lens group, and its output light is used to excite a photoacoustic signal. The detection module includes a focused ultrasonic probe, an amplifier, and a digital converter. The focused ultrasonic probe receives the photoacoustic signal and is constructed by connecting an acoustic lens to a planar ultrasonic transducer. The imaging head consists of a laser illumination section and an acoustic detection section. During image acquisition, the imaging head scans via the two-dimensional electrically controlled displacement platform. The detected photoacoustic signal is amplified by a low-noise preamplifier, recorded by the digital converter, and then stored in a computer. The sample is placed in the water tank.

2. The apparatus as claimed in claim 1, characterized in that, The acoustic lens has a numerical aperture of 0.44 and a focal length of 6.7 mm.

3. The apparatus as described in claim 1, characterized in that, The laser illumination part of the imaging head is an optical fiber; the acoustic detection part is a focused ultrasound probe.

4. The apparatus as claimed in claim 1, characterized in that, The device for detecting blood triglyceride concentration using photoacoustic microscopy has a lateral and axial resolution of approximately 65 μm and 40 μm, respectively.

5. The apparatus as claimed in claim 1, characterized in that, The sample, a blood solution, is sampled by capillary tubes fixed side-by-side on a coverslip.

6. The apparatus as claimed in claim 5, characterized in that, The capillary has an inner diameter of 500 μm and an outer diameter of 700 μm.

7. The apparatus as claimed in claim 1, characterized in that, The sample is positioned using the three-dimensional platform.

8. The apparatus as claimed in claim 5, characterized in that, The samples were tested in groups of seven.

9. The apparatus as claimed in claim 1, characterized in that, The sample stage module also includes a pump flow system.

10. A photoacoustic microscopy method for detecting blood triglyceride concentration, characterized in that, include: Step 1: Seven blood solutions were prepared, consisting of lyophilized hemoglobin powder, triglycerides, and deionized water, to create final blood solutions with different triglyceride concentrations. Then, seven spotting capillary tubes filled with seven different blood solutions were sealed at both ends, fixed side by side on a coverslip, and then placed in a water tank for imaging experiments. Step 2: Photoacoustic excitation is performed using a pulsed laser. After passing through a beam splitter, the laser beam is split into two beams. One beam enters a photodetector, and its output electrical signal serves as the trigger signal for the digital converter. The other beam is coupled to a multimode fiber optic patch cord via a lens group, and its outgoing light is used for photoacoustic signal excitation. A focused ultrasonic probe receives the photoacoustic signal. The focused ultrasonic probe is constructed by connecting an acoustic lens to a planar ultrasonic transducer. Then, signal and image acquisition is performed. Step 3: During image acquisition, the imaging head, consisting of a laser illumination section and an acoustic detection section, is scanned by a two-dimensional electronically controlled displacement platform; the detected photoacoustic signal is amplified by a low-noise preamplifier, recorded by a digital converter, and then stored in a computer; at the same time, the sample is placed in a water tank, and the sample can be positioned by a three-dimensional platform.

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