X-ray scintillator imaging system and method based on surface enhanced Raman scattering

Abstract

The invention relates to an X-ray scintillator imaging system based on surface enhanced Raman scattering, X-rays emitted by an X-ray source penetrate through a sample and then enter a scintillator, the scintillator converts the X-rays into visible fluorescence, small-angle fluorescence directly escapes, and large-angle fluorescence is totally reflected to form evanescent waves; the metal nano array on the surface of the scintillator acts with evanescent waves to excite localized surface plasmon resonance, the Raman scattering substance generates surface enhanced Raman scattering under the action of the metal nano array, and the intensity distribution of the localized surface plasmon resonance is converted into the light intensity distribution of Raman scattering light; raman scattering light is focused by a lens and filtered by a filter and then is received by a surface detector, and an image containing high-frequency information of a sample space is output. The invention also relates to an X-ray scintillator imaging method based on surface enhanced Raman scattering. The surface enhanced Raman scattering technology is overcome, effective utilization of high-frequency information is achieved, and new possibility is provided for development of the X-ray imaging technology.

Description

Technical Field

[0001] This invention relates to X-ray imaging, and more specifically to an X-ray scintillator imaging system and method based on surface-enhanced Raman scattering. Background Technology

[0002] X-ray imaging technology is widely used in clinical medicine, scientific research, non-destructive testing, and nuclear and radiation protection due to its numerous advantages. It boasts high spatial resolution, enabling the clear differentiation of minute internal structures of objects; simultaneously, its high penetrability allows X-rays to penetrate human tissue, metals, and other materials, achieving non-invasive imaging. Furthermore, X-ray imaging features short exposure times and fast imaging speeds, enabling rapid detection and making it suitable for dynamic observation. It can also perform imaging under various environmental conditions, and through different imaging techniques and processing methods, image contrast can be enhanced, making it easier to distinguish substances of different densities or compositions within the image.

[0003] Among numerous X-ray imaging methods, X-ray scintillator imaging has attracted considerable attention due to its unique advantages. This method converts X-rays into scintillator fluorescence, achieving low cost, stable performance, long detection lifetime, and fast response speed, thus gaining widespread application. However, this imaging method also has a significant technical bottleneck: due to the total internal reflection of fluorescence on the scintillator surface, X-ray scintillator imaging suffers from the loss of high-frequency spatial information.

[0004] Specifically, when X-rays excite a scintillator to produce fluorescence, the fluorescence propagates inside the scintillator. Due to the high refractive index of the scintillator, total internal reflection occurs when the fluorescence reaches the scintillator surface if the angle of incidence is greater than the critical angle. Total internal reflection prevents large-angle fluorescence beams from escaping from the scintillator surface, confining them inside the scintillator. These large-angle beams correspond to the spatial high-frequency components of the image (the detailed parts), i.e., the most detailed areas in the image. Due to total internal reflection, this high-frequency information cannot be captured by the detector, resulting in the loss of high-frequency details in the image. Although this high-frequency information still exists near the scintillator surface in the form of "evanescent waves," the amplitude of these evanescent waves decays exponentially with distance, making this information difficult to detect and utilize directly. Summary of the Invention

[0005] To address the problem of spatial high-frequency information loss caused by total internal reflection of fluorescence in existing X-ray scintillator imaging, this invention provides an X-ray scintillator imaging system and method based on surface-enhanced Raman scattering.

[0006] The X-ray scintillator imaging system based on surface-enhanced Raman scattering according to the present invention comprises: an X-ray source, wherein the emitted X-rays penetrate the sample and are incident on a scintillator; the scintillator converts the X-rays into visible fluorescence, the fluorescence propagating inside the scintillator, wherein small-angle fluorescence escapes directly, and large-angle fluorescence forms an evanescent wave at the interface between the scintillator and air due to total internal reflection; a metal nanoarray is fabricated on the light-emitting surface of the scintillator away from the X-ray incident side, and interacts with the evanescent wave to excite local surface plasmon resonance; a Raman scattering material is covered on the surface of the metal nanoarray, and surface-enhanced Raman scattering occurs under the electromagnetic field of local surface plasmon resonance, converting the intensity distribution of local surface plasmon resonance into the intensity distribution of Raman scattered light; a lens focuses the Raman scattered light onto a surface detector; a filter is disposed between the lens and the surface detector to filter out the original fluorescence that has not undergone Raman scattering; and the surface detector receives the intensity distribution of Raman scattered light and outputs a visualized image containing high-frequency spatial information of the sample.

[0007] In a preferred embodiment, the size (e.g., diameter, length) and period of the metal nanoarray are on the order of hundreds of nanometers.

[0008] In a preferred embodiment, the metal nanoarray is fixed on the surface of the scintillator by a coating or photolithography process.

[0009] In a preferred embodiment, the Raman scattering material is anhydrous ethanol, with a Raman frequency shift of 3000 cm⁻¹.

[0010] In a preferred embodiment, the Raman scattering material is attached to the surface of the metal nanoarray by coating or adsorption.

[0011] In a preferred embodiment, the optical axis of the lens is coaxially aligned with the main propagation direction of the Raman scattered light, and the distance between the lens and the surface detector is equal to the focal length of the lens.

[0012] In a preferred embodiment, the filter is a narrowband filter whose center wavelength matches the wavelength of Raman scattered light.

[0013] In a preferred embodiment, the surface detector is a CCD camera or an sCMOS camera.

[0014] The X-ray scintillator imaging method based on surface-enhanced Raman scattering according to the above-described imaging system of the present invention includes the following steps: S1, an X-ray source emits X-rays, which penetrate the sample and carry the spatial distribution information of the sample to the scintillator; S2, the scintillator converts the X-rays into visible fluorescence, the fluorescence propagates inside the scintillator, small-angle fluorescence escapes directly, and large-angle fluorescence forms an evanescent wave at the interface between the scintillator and the air due to total internal reflection; S3, the metal nanoarray on the light-emitting surface of the scintillator interacts with the evanescent wave to excite local surface plasmon resonance (LSPR); S4, the Raman scattering material on the surface of the metal nanoarray undergoes surface-enhanced Raman scattering under the action of the electromagnetic field enhanced by the local surface plasmon resonance, converting the intensity distribution of the local surface plasmon into the intensity distribution of the Raman scattered light; S5, the Raman scattered light is focused by a lens and filtered by a filter to remove the original fluorescence that has not undergone Raman scattering, and then received by a surface detector; S6, the surface detector outputs a visualized image containing high-frequency spatial information of the sample.

[0015] The X-ray scintillator imaging system and method based on surface-enhanced Raman scattering (SERS) of this invention utilizes a metal nanoarray constructed on the surface of the scintillator. This allows evanescent waves generated by total internal reflection of large-angle beams in X-ray-excited fluorescence to excite localized surface plasmon resonance (LSPR). The SERS effect of a Raman-scattering material (such as anhydrous ethanol) covering the nanoarray surface is then used to convert the LSPR intensity distribution carrying high-frequency information into enhanced Raman scattered light. After filtering the original fluorescence with a filter and focusing with a lens, the Raman scattered light is received and imaged by a surface detector, thereby extracting more spatial high-frequency information and improving image quality. This imaging method effectively extracts more spatial high-frequency information, improving image quality and resolution. This method not only overcomes the problem of high-frequency information loss in traditional X-ray imaging but also achieves effective utilization of high-frequency information through surface-enhanced Raman scattering technology, providing new possibilities for the development of X-ray imaging technology. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an X-ray scintillator imaging system based on surface-enhanced Raman scattering according to the present invention. Detailed Implementation

[0017] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0018] like Figure 1 As shown, the X-ray scintillator imaging system based on surface-enhanced Raman scattering according to the present invention includes an X-ray source 1, a sample 2, a scintillator 3, a metal nanoarray 4, a Raman scattering material 5, a lens 6, a filter 7, and a surface detector 8 arranged sequentially along the optical path.

[0019] X-ray source 1, as the incident signal source, is located at the very front of the optical path. The X-rays emitted by it propagate in a straight line, directly irradiating sample 2, which is located in the X-ray propagation path and between X-ray source 1 and scintillator 3. Different internal structures of sample 2 (such as differences in density and composition) will absorb or scatter the X-rays, causing the passing X-rays to carry their own spatial distribution information, providing the original basis for subsequent imaging.

[0020] The scintillator 3, which receives X-rays passing through sample 2, has its receiving surface facing the exiting surface of sample 2. It can effectively convert X-rays (high-energy photons) into visible light fluorescence (low-energy photons), transforming invisible X-ray information into fluorescence signals that can be detected by the optical system, thus completing the energy form conversion.

[0021] The metal nanoarray 4 is fabricated on the light-emitting surface of the scintillator 3 (away from the X-ray incident side), forming an integrated structure with the scintillator 3. It is directly fixed to the scintillator surface through coating or photolithography, forming a tight physical connection. The size and period of its surface nano-periodic structure are both on the order of hundreds of nanometers, and the specific parameters need to be optimized based on the absorption of the metal nanostructure on the corresponding wavelength band of the scintillator fluorescence in FDTD simulation. This ensures that: on the one hand, it can precisely interact with the evanescent waves formed at the scintillator-air interface by large-angle beams (beams that cannot escape the scintillator due to total internal reflection) in the scintillator fluorescence, exciting local surface plasmon resonance (LSPR) and converting the energy of the evanescent waves carrying high-frequency spatial information into local electromagnetic field enhancement; on the other hand, since the period of the nanodots and array is much smaller than the propagation wavelength of the small-angle beam, the relative intensity distribution of the small-angle beam is not affected by the metal nanoarray, ensuring the normal transmission of low-frequency information.

[0022] Raman scattering material 5 is coated and directly contacts the surface of the metal nanoarray 4 through coating, adsorption, or other methods. Under the influence of the LSPR-enhanced electromagnetic field of the metal nanoarray 4, Raman scattering material 5 undergoes surface-enhanced Raman scattering (SERS), converting the LSPR intensity distribution (containing spatial high-frequency information) into a Raman scattered light signal. Because the fluorescence generated by the scintillator excited by X-rays is not a single wavelength but has a certain spectral width (different scintillators have different fluorescence spectral widths, typically covering tens of nanometers), if the frequency shift of the Raman scattering material is too small, the Raman scattered light wavelength will overlap with the spectral range of the original fluorescence, causing the filter to be unable to accurately distinguish between the two. The original fluorescence noise will be mixed with the Raman signal, severely reducing the imaging signal-to-noise ratio. Therefore, it is necessary to select a material with a sufficiently large Raman frequency shift to "distance" the Raman scattered light from the original fluorescence spectrally. In a preferred embodiment, anhydrous ethanol is used as the Raman scattering material. Its large Raman frequency shift peak of 3000 cm⁻¹ allows the Raman scattered light to jump out of the spectral coverage range of the scintillator fluorescence, ensuring that the filter effectively filters the original fluorescence and only allows the Raman scattered light carrying high-frequency information to pass through, thus laying the foundation for high-quality imaging.

[0023] Lens 6 is fixed in the optical path by an optical support, positioned on the Raman scattered light propagation path between Raman scattering material 5 and filter 7. Its optical axis is coaxially aligned with the principal axis of the scattered light originating from the surface of the Raman scattering material, ensuring that the Raman scattered light enters the lens to the maximum extent. Simultaneously, the distance between lens 6 and surface detector 8 is equal to its own focal length, enabling the Raman scattered light focused by the lens to propagate accurately to the subsequent filter and surface detector, reducing signal loss during propagation. Appropriate selection of the numerical aperture of lens 6 can reduce the impact of diffraction on high-frequency information, ensuring that the spatial high-frequency information carried by the Raman scattered light is not lost during focusing, thus preserving imaging details.

[0024] The filter 7 is positioned between the lens 6 and the surface detector 8, and is located in the propagation path of the Raman scattered light. Its center wavelength matches the wavelength of the Raman scattered light. The function of this filter is to filter out the original scintillator fluorescence that has not undergone Raman scattering (i.e., the light before the frequency shift), allowing only the Raman scattered light (the light after the frequency shift) to pass through, thereby reducing the interference of background noise on the subsequent detection process and improving the signal-to-noise ratio of the imaging.

[0025] A surface detector 8 (such as a CCD or sCMOS camera) is located behind the filter 7, with its photosensitive surface coinciding with the focal plane of the lens 6. It is used to receive the intensity distribution of Raman scattered light after being filtered by the filter. The surface detector converts the received light signal into an electrical signal and records it as a digital image, ultimately outputting a visualized image containing high-frequency information about the sample space.

[0026] The X-ray scintillator imaging method based on surface-enhanced Raman scattering according to the present invention specifically includes: X-ray source 1 emits X-rays that penetrate sample 2 and carry information, and are incident on scintillator 3 and converted into visible fluorescence; the fluorescence propagates inside scintillator 3, small-angle fluorescence escapes directly, and large-angle fluorescence forms evanescent waves due to total internal reflection, which excites metal nanoarray 4 to generate LSPR enhanced local electromagnetic field; the Raman scattering material 5 on the surface of metal nanoarray 4 undergoes SERS in the enhanced electromagnetic field, converting high-frequency information into Raman scattered light; the Raman scattered light passes through filter 7 to filter out noise, and is focused by lens 6 to surface detector 8, and surface detector 8 records the light intensity distribution and outputs the imaging result.

[0027] This high-frequency information extraction process relies on deterministic physical interactions such as the plasmonic resonance between the metal nanoarray 4 and the evanescent wave, and the SERS effect of the Raman scattering material 5. The high-frequency information carried by the evanescent wave is directly converted into a local electromagnetic field distribution via LSPR, and then directly converted into a detectable optical signal via Raman scattering. No additional encoding (such as artificial signal modulation) or decoding (such as algorithm demodulation) is required throughout the process. This direct conversion based on physical laws, compared to encoding-decoding techniques, avoids uncertainties introduced during decoding due to algorithm errors and noise amplification, making high-frequency information extraction more stable and reliable.

[0028] Surface-enhanced Raman scattering (SERS) is key to enhancing high-frequency information in X-ray scintillator imaging, involving a combination of localized surface plasmon resonance (LSPR) excitation and SERS techniques. When an X-ray excites a scintillator to produce fluorescence, the fluorescence beam undergoes total internal reflection at the scintillator surface, forming an evanescent wave (an electromagnetic wave generated on the surface of a high-refractive-index medium, whose amplitude decays exponentially with distance from the surface). Metal nanostructures (nanometer-scale in size, such as nanoparticles or nanorods) constructed on the scintillator surface interact with the evanescent wave, and when their size and shape are similar to the wavelength of the fluorescence beam, they excite LSPR (a strong electromagnetic field formed on the surface of the metal nanostructure, which enhances the interaction between light and matter; its resonant frequency can be adjusted by changing the size, shape, and material of the metal nanostructure, selectively enhancing the frequency of the fluorescence beam and preserving high-frequency information). Surface-enhanced Raman scattering (LSPR) technology utilizes metal nanostructures to enhance Raman scattering signals. When a fluorescent beam carrying high-frequency information interacts with a metal nanostructure, and the frequencies of the incident and scattered light are within the resonant frequency range of the metal nanostructure, Raman scattering is significantly enhanced. This allows the high-frequency image information stored in the LSPR distribution to be read out. The enhanced Raman scattered light carries the original fluorescence frequency information and can penetrate the scintillator surface to be captured by the detector. By analyzing its intensity and frequency distribution, the original high-frequency image information can be reconstructed.

[0029] During Raman scattering on the surface of a metallic nanostructure, the presence of the photon resonator (LSPR) leads to two enhancements: during absorption, the absorption of incident light by the metallic nanostructure under resonant conditions is significantly enhanced by the electric field of the LSPR, resulting in the absorption of more photon energy; during scattering, if the frequency of the Raman scattered light is within the resonant frequency range of the metallic nanostructure, the intensity of the scattered light also increases due to the enhanced electric field. To achieve maximum enhancement, both the incident light (X-ray excited fluorescence) and the scattered light frequencies must be within the resonant frequency range of the metallic nanostructure, allowing them to effectively interact with the LSPR. The enhanced Raman scattering signal is then captured by the detector and converted into an electrical signal, achieving high-quality X-ray imaging.

[0030] By constructing a metallic nanostructure on the surface of a scintillator, evanescent wave excitation of LSPR is used to preserve high-frequency image information, which is then read out using SERS technology. This effectively overcomes the problem of high-frequency information loss in traditional X-ray imaging, improves imaging resolution and quality, and provides new possibilities for the development of X-ray imaging technology. This imaging method can extract more spatial high-frequency information and optimize imaging quality and resolution.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.

Claims

1. An X-ray scintillator imaging system based on surface-enhanced Raman scattering, characterized in that, The imaging system includes: The X-ray source (1) emits X-rays that penetrate the sample (2) and then enter the scintillator (3). The scintillator (3) converts X-rays into visible fluorescence. The fluorescence propagates inside the scintillator (3). Small-angle fluorescence escapes directly, while large-angle fluorescence forms evanescent waves at the interface between the scintillator (3) and the air due to total internal reflection. Metal nanoarrays (4) are fabricated on the light-emitting surface of scintillator (3) away from the X-ray incident side, and interact with evanescent waves to excite local surface plasmon resonance (LSPR). Raman scattering material (5) is covered on the surface of metal nanoarray (4). Under the electromagnetic field of local surface plasmon resonance (LSPR), surface enhanced Raman scattering (SERS) occurs, converting the intensity distribution of local surface plasmon resonance (LSPR) into the intensity distribution of Raman scattered light. The lens (6) focuses the Raman scattered light onto the surface detector (8); The filter (7) is placed between the lens (6) and the surface detector (8) to filter out the original fluorescence that has not undergone Raman scattering; The surface detector (8) receives the Raman scattered light intensity distribution and outputs a visualized image containing high-frequency information of the sample space.

2. The imaging system according to claim 1, characterized in that, The size and period of the metal nanoarray (4) are in the hundreds of nanometers.

3. The imaging system according to claim 1, characterized in that, Metal nanoarrays (4) are fixed on the surface of scintillator (3) by coating or photolithography.

4. The imaging system according to claim 1, characterized in that, The Raman scattering substance (5) is anhydrous ethanol, and its Raman frequency shift is 3000 cm⁻¹.

5. The imaging system according to claim 1, characterized in that, Raman scattering material (5) is attached to the surface of metal nanoarray (4) by coating or adsorption.

6. The imaging system according to claim 1, characterized in that, The optical axis of the lens (6) is coaxially aligned with the main propagation direction of the Raman scattered light, and the distance between the lens (6) and the surface detector (8) is equal to the focal length of the lens (6).

7. The imaging system according to claim 1, characterized in that, The filter (7) is a narrowband filter whose center wavelength matches the wavelength of Raman scattering light.

8. The imaging system according to claim 1, characterized in that, The surface detector (8) is a CCD camera or an sCMOS camera.

9. A method for X-ray scintillator imaging based on surface-enhanced Raman scattering according to any one of claims 1-8, characterized in that, Includes the following steps: S1, X-ray source (1) emits X-rays, which penetrate the sample (2) and carry the spatial distribution information of the sample (2) into the scintillator (3). S2, the scintillator (3) converts X-rays into visible fluorescence. The fluorescence propagates inside the scintillator (3). Small-angle fluorescence escapes directly, while large-angle fluorescence forms evanescent waves at the interface between the scintillator (3) and the air due to total internal reflection. S3, the metal nanoarray (4) on the light-emitting surface of the scintillator (3) interacts with the evanescent wave to excite local surface plasmon resonance (LSPR). S4, Raman scattering material (5) on the surface of the metal nanoarray (4) undergoes surface-enhanced Raman scattering under the action of electromagnetic field enhanced by local surface plasmon resonance, converting the intensity distribution of local surface plasmon into the intensity distribution of Raman scattered light. S5, the Raman scattered light is focused by the lens (6), filtered by the filter (7) to remove the original fluorescence that has not undergone Raman scattering, and then received by the surface detector (8); S6, the surface detector (8) outputs a visualized image containing high-frequency information of the sample space.

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