Photoacoustic imaging device and converter mounting method

Abstract

The photoacoustic imaging device uses a number of acoustoelectronic transducers. The transducers have a sound receiving surface that forms part of the surface of the basin of the breast cup. The transducers each have a foil adhesively connected to its sound receiving surface and a reflective coating provided on the basin side of the foil. The reflective (e.g. gold) coating is used to minimize photoacoustic sound generation at the surface of the transducer, which can lead to image artifacts when this sound is reflected from within the basin. By providing a coating on a smooth foil of copper foil or polymer foil adhered to the transducer surface, a reduction in photoacoustic sound generation at the surface sufficient for a significant reduction in photoacoustic image artifacts can be achieved. The foil can be attached to the transducer in the form of a patch after the transducer is attached on the basin, and the patch can extend from the transducer to the periphery of the basin to reduce photoacoustic sound generation in the gap between the transducer and the surface of the basin.

Description

Technical Field

[0001] The present invention relates to a photoacoustic imaging device and, for example, a method of attaching an acoustic transducer within a photoacoustic imaging device when the photoacoustic imaging device is assembled.

Background Art

[0002] Photoacoustic imaging involves sending light pulses into tissue and forming an image (usually a 3D image) of the sound generation resulting from the absorption of light in the tissue (as used herein, "sound" covers "ultrasound"). The tissue is presented within a basin that also includes an acoustic coupling fluid such as water.

[0003] The pulses are preferably very short (nanosecond), intense (near) infrared pulses provided by a light source having an output or diffused light output on the wall of the basin.

[0004] In the tissue, the light pulse causes light absorption, which causes a temperature rise that results in thermal expansion, which in turn leads to a pressure transient that generates low-intensity sound waves (especially from blood). An array from the very high-sensitivity broadband acoustics through the wall of the basin to the transducer within the aperture detects these waves.

[0005] The detection results can be used to reconstruct an image with high spatial resolution, such as a complete 3D vascular system.

[0006] In particular, the intensity of the sound waves detected from photoacoustic conversion in deeper parts of the tissue that are further away from the surface position (skin) where the light is supplied is very small.

[0007] This requires the ability to distinguish between subtle photoacoustic responses from tissues like blood vessels lying deeper, and noise and artifacts in the 3D image reconstruction of these vessels. This necessitates the suppression of artifacts that interfere with small ultrasound signals. It is known that interfering artifacts can be caused by light reaching the sound-receiving surface of the acoustic-electron transducer and causing photoacoustic conversion at that surface.

[0008] These direct (ultrasonic) signals from photoacoustic conversion can be easily canceled out by time windowing because these direct signals precede the arrival of sound waves from the tissue that must travel from the location of the photoacoustic conversion within the tissue.

[0009] However, sound generated at the sound-receiving surface of the acoustic-electron transducer can also propagate into the tissue and potentially reflect back to the acoustic-electron transducer. Artifacts resulting from such reflections are known to be quite difficult to eliminate through signal processing. Instead, the inventors have attempted to reduce the photoacoustic autoresponder of the acoustic-electron transducer surface. A possible method for reducing this photoacoustic response from the surface is to coat the surface with a light-reflecting layer that reflects near-infrared light, thereby minimizing the amount of light reaching the coating and the surface beneath the coating where photoacoustics may occur, without significantly reducing sound transmission from the tissue to the acoustic-electron transducer surface.

[0010] For example, a gold coating may be used. Gold has the additional beneficial property of being particularly inert to oxygen, thereby protecting the reflective surface. Gold is known to be a very effective reflector for (near) infrared light. See Reference [1] BASS.M(eic.) Handbook of Optics, Volume II Devices, Measurements, and Properties, Chapter 35, pages 35.1-35.74, McGraw-Hill Professional, New York, second edition (1995); ISBN 0-07-047974-7, TABLE 3 Reflectance of Selected Metals at Normal Incidence (pages 35.33-34), Paquin, RE "Properties of Metals". See also Lynch, DW, "Mirror and Reflector Materials" in Reference [2] Weber, MJ (ed.), CRC Handbook of Laser Science and Technology, IV, Optical Materials, Part 2: Properties, CRC Press, Boca Raton, Florida (2003); ISBN 0-8493-3512-4, Section 1.3, Fig. 4.2.8.

[0011] In principle, a very thin (submicrometer (e.g., several hundred nanometers)) reflective gold coating may be sufficient to prevent significant light transmission to the surface beneath the acoustic-electron transducer. This is advantageous because the gold layer can be used to ensure that it is thin enough to avoid loss of transmitted ultrasonic intensity, for example, due to reflection.

[0012] However, while a gold layer has a sufficiently reflective minimum thickness, it has been found that similar artifacts originating from the surface beneath the acoustic-electron converter still occur. Without a gold coating significantly thicker than what is required for reflection, a gold coating on the surface of the acoustic-electron converter has been found to only slightly reduce artifacts similar to those of photoacoustic conversion on the surface of the acoustic-electron converter.

[0013] Sufficient thickness of this coating is necessary to obtain a coating that overcomes the roughness of the transducer's receiving surface and to cover the entire area with a sufficiently thick layer of gold. When vapor deposition or sputtering is used to deposit such a layer of gold, the layer is affected by shadows, and if the treated surface is not perfectly smooth, the result is that gaps and indentations within the surface do not have a sufficient thickness of gold anywhere, which can lead to a situation where light is still absorbed on the surface in areas that are not (sufficiently) covered. As a result, undesirable photoacoustic signals may still occur, which will negatively affect the system's signal-to-noise ratio (SNR).

[0014] To overcome this, the sound-receiving surface may be pre-treated to obtain a sufficiently smooth surface and therefore a uniform reflective layer, or a relatively thick layer of reflective material may be applied, while this layer may be thin enough to completely transmit ultrasonic waves.

[0015] US2019 / 275562 discloses an ultrasonic transducer with a ground electrode on a film on the receiving surface of the transducer, the ground electrode connected to the metal housing of the transducer. This is used, for example, to prevent electromagnetic interference from an RF field used to create an acoustic signal from a sample by heating the sample. Metal rubber sheets have been found to be capable of functioning as conductive films. In principle, films with a conductive layer can also be used in ultrasonic transducers in photoacoustic imaging systems, in which case the ground electrode on the film can reflect some of the light that can reach the surface of the acoustic-electronic transducer. However, such film structures do not guarantee a combination of high transmittance of weak photoacoustic signals from a sample and high reflectivity of light from optical pulses. [Overview of the project]

[0016] The objective is to reduce artifacts caused by photoacoustic conversion in transducers used within photoacoustic imaging devices (for example, for mammography applications).

[0017] According to one embodiment, the reduction of artifacts caused by the photoacoustic response of the transducer is achieved by a photoacoustic imaging device comprising the following: Basin for receiving tissue to be imaged A light source configured to supply light to the interior of the basin. Multiple acoustic-electronic transducers, each of which has a sound-receiving surface that forms part of the surface of the basin at a different position within the surface of the basin, and each having a foil adhesively attached to the receiving surface and a reflective coating provided on the basin side of the foil. The use of foil such as metal foil, or more specifically, copper foil with a reflective coating such as gold coating, and adhesive facilitates the installation and repair of the photoacoustic imaging system in a manner that achieves the high demand for artifact suppression in the context of photoacoustic imaging devices. Such foils can be installed even after the transducers have been mounted in the basin during initial assembly or repair.

[0018] Preferably, a rigid, highly reflective material such as gold is used for the reflective coating.

[0019] When a reflective coating, such as a gold coating, that is reflective to light from a light source (e.g., in the near-infrared), is used on the basin-side surface of a smooth, flexible metal foil, such as copper foil, the reflective coating has been found to be sufficient to reduce artifacts in a manner that allows for better sensitive photoacoustic imaging compared to when the reflective surface is used directly on the surface of an acoustic-electron transducer. This is because the metal foil allows for improved smoothness of the reflective coating compared to when the coating is applied directly to the transducer surface, and it is assumed that this reduces the photoacoustic conversion due to light absorption by the reflective coating as a result of multiple reflections by the reflective coating. Preferably, a patch is used where the coating surface is smooth such that its RMS gradient value is less than 0.42, and more preferably at most 0.1. Preferably, the foil surface beneath the coating also has an RMS gradient value of less than 0.42, and more preferably at most 0.1. For example, the smoothness of a metal foil manufactured using cold rolling may be sufficient to improve the smoothness of the reflective coating. Alternatively, a polymer foil with equivalent smoothness may be used.

[0020] Preferably, a gold coating is used on the copper layer. Gold is a good reflector of infrared and near-infrared light. Furthermore, the gold and copper layers hardly reduce ultrasonic transmission to the ultrasonic transducer, and these layers can be made thin to minimize the reduction in sound transmission. In addition, gold is resistant to degradation of light reflection, and copper makes the smoothness more robust.

[0021] In one embodiment, a smooth foil may be attached to the receiving surface of the transducer using an adhesive layer that may be provided on the transducer-side surface of the foil before the foil is attached to the receiving surface of the transducer. The adhesive is selected to facilitate attachment and to allow for easy removal of the coated foil from the transducer when either the foil or the transducer needs to be replaced. The smooth foil may be supplied in the form of an adhesive tape.

[0022] Each acoustic-electronic transducer has a conductive housing around an axis perpendicular to the receiving surface. In one embodiment, the conductive housing is electrically connected to a metal foil. Thus, the metal foil can perform two functions: reducing the generation of photoacoustic signals and shielding the electromagnetic field in the transducer.

[0023] In addition to the functional benefits, applying reflective material to the foil is less expensive than applying it to the transducer, thus significantly reducing the cost of applying the reflective material. Positioning the foil within the deposition chamber is considerably easier and more efficient compared to a complete transducer element.

[0024] In embodiments where the transducer extends through an opening in the basin's basic structure, the copper foil is provided within patches on each of the multiple acoustic transducers, extending from the receiving surface of the acoustic transducer to the surface of the basic structure around the opening through which the acoustic transducer extends. The gap between the transducer and the basic structure may include an O-ring to prevent water leakage from the basin or other materials. However, it has been found that the gap or the material within the gap can contribute to photoacoustic noise generation. The use of gold-coated copper patches extending from the receiving surface of the transducer through the gap to the surface of the basic structure around the transducer can prevent, or at least reduce, photoacoustic noise generation within the gap.

[0025] Patch edges may also generate some photoacoustic noise, but the intensity of this noise has been found to be less than that from gaps.

[0026] Preferably, different ones of the plurality of acoustic electro - transducers each have their own foil with a reflective coating in the form of mutually separated patches. For example, after disinfecting the wall of the measurement basin to which the transducer is attached, when the surface of the transducer is slightly damaged, or when worn from such cleaning, the patch can be easily removed and replaced with another patch, without the need to remove and replace the complete transducer element, which would be much more costly and require significant labor time.

[0027] These and other objects and advantageous aspects will become apparent from the description of the exemplary embodiments with reference to the following drawings.

Brief Description of the Drawings

[0028] [Figure 1] It is a diagram showing the basin of a photoacoustic imaging device. [Figure 2] It is a diagram schematically showing a part of the basin of a photoacoustic imaging device. [Figure 3] It is a top view schematically showing an acoustic electro - transducer. [Figure 4] It is a diagram showing a cross - section of a patch. [Figure 5] It is a diagram exemplarily showing a normalized RMS ultrasonic signal amplitude. [Figure 6] It is a diagram showing an embodiment of a conductive layer.

Modes for Carrying Out the Invention

[0029] FIG. 1 shows the basin of a photoacoustic imaging device in the form of a hemispherical bowl 1 having an interior for receiving the chest (not shown) in vivo. The surface of the bowl 1 is defined by a basic structure 10 with one or more outputs 12 of a light source for supplying light into the bowl 1 and an aperture for an acoustic electro - transducer 14. By way of example, a hemispherical bowl 1 for receiving the chest is shown, but it should be understood that other types of tissue can be imaged and different shaped basins can be used.

[0030] Figure 2 schematically shows a portion of the basin of a photoacoustic imaging device, including a basic structure 10 (shown flat for simplification of the figure) with an acoustic-electron transducer extending through an aperture.

[0031] Figure 3 schematically shows a top view of the acoustic-electronic transducer 14. A patch 16 of gold-coated copper foil is provided at least above the acoustic-electronic transducer 14. The patch 16 covers the sound-receiving surface of the acoustic-electronic transducer 14. Preferably, the patch 16 extends over the basic structure 10 around the opening containing the acoustic-electronic transducer 14, as shown in the figure.

[0032] A cross-section of patch 16 is shown (not to a constant scale), comprising a copper foil 40, a gold coating 42 on the basin-side surface of the copper foil 40, and an adhesive layer 44 on the transducer-side surface of patch 16. In the exemplary embodiment, an 18-micrometer thick copper foil with a 0.5-micrometer thick gold coating was used. Preferably, a nickel diffusion barrier layer may be used between the copper layer and the gold layer, or a NiCr, Cr layer may be used instead of the nickel diffusion barrier. Other examples include cobalt, palladium, copper-tin alloys, and alloys of these materials. The bottom of the copper foil was attached to the surface of the acoustic-electronic transducer 14 with a 32-micrometer thick acrylic adhesive. However, copper foil thicknesses between 1 and 100 micrometers, and gold coating thicknesses between 0.1 and 2 micrometers, more preferably between 0.2 and 2 micrometers, may be used. The coating layer may be applied, for example, by electroplating, or by other deposition methods such as sputtering or vapor deposition. A polymer foil with similar smoothness may be used instead of a metal foil. In one example, a 25-micrometer thick polyimide foil was used with a 0.4-micrometer thick gold coating. Optionally, a thin Ti layer may be used as an adhesion promoter between the polyimide and the gold on top of the polyimide foil, and the surface of the acoustic-electronic transducer 14 is attached to the underside of the foil with a 45-micrometer thick silicone adhesive.

[0033] The thickness of the adhesive layer is not critical and may vary slightly between different locations, but the adhesive layer can be optimized for ultrasonic matching, for example, by combining the adhesive layer with a layer on the transducer surface (see Callens et al., "Matching ultrasonic transducer using two matching layers where one of them is glue" in NDT&E International 37 (2004) 591-597).

[0034] The thickness of the combination of coating, metal layer, and adhesive layer is preferably kept low so that the absorption and reflection of ultrasound by the combination does not significantly reduce the ultrasonic signal intensity in the transducer. For example, the thickness of the combination may be less than 100 micrometers, such as a layer of about 50 micrometers consisting of about 1 micrometer of gold, 2 micrometers of nickel, 18 micrometers of copper, and 32 micrometers of acrylic adhesive.

[0035] While embodiments are described in which each acoustic-electronic transducer 14 has its own isolation patch, it should be understood that alternative patches may be used to cover two or more acoustic-electronic transducers 14 within the basin wall, or even all of these acoustic-electronic transducers 14.

[0036] However, regarding the gap, the surface of the basic structure 10 of the bowl and the upper surface of the acoustic transducer 14 form a semi-continuous surface with virtually no step difference between the basic structure 10 and the upper surface of the acoustic transducer 14 (e.g., with a step difference of less than 0.1 mm in height). At most, a small gap (e.g., less than 0.1 mm in width) exists between the acoustic transducer 14 and the basic structure 10. To prevent water leakage from the basin, an O-ring or other means may be provided in the gap. The upper surface of the acoustic transducer 14 acts as a sound-receiving surface.

[0037] Acoustic-electron transducers can be installed within a photoacoustic imaging device by mounting each transducer in a position where it extends through an opening, so that the receiving surface of the acoustic-electron transducer forms part of the surface of the basin. Subsequently, foil can be attached to the receiving surface. This can be done for all acoustic-electron transducers. The foil (or patch of foil) may be provided with an adhesive layer on the surface opposite to the surface with a gold coating in order to attach the foil to the acoustic-electron transducer.

[0038] A transducer with an acoustic matching layer on the receiving layer may be used. While efficient gold deposition on any acoustic matching layer is not possible, this can be overcome by attaching a gold coating to foil. When foil is attached to the receiving surface with the acoustic matching layer, this avoids the need for the entire transducer, or at least its active element, to undergo a process that directly applies reflective material to the entire receiving surface of the transducer.

[0039] If necessary, foil with gold coating across one or more acoustic transducers may be later removed and replaced with new foil. When foil is attached to the receiving surface (initially or as replacement), the foil may preferably be attached so as to extend from the receiving surface of one or more acoustic transducers to the surface of the basic structure around the opening through which one or more acoustic transducers 14 extend.

[0040] During operation, the light source transmits light pulses into the bowl 1 via its output 12, and the acoustic-electronic transducer 14 receives the generated sound inside the bowl 1. The generated sound includes sound generated due to the absorption of the light pulses. The acoustic-electronic transducer 14 receives the sound via its sound-receiving surface and converts the received sound into an electronic signal. The acoustic-electronic transducer 14 may use a piezoelectric material for this purpose. The photoacoustic imaging device comprises a data processing system (not shown, but e.g., a computer) coupled to the electronic output of the acoustic-electronic transducer 14 and configured (e.g., programmed) to calculate the amplitude of the generated sound as a function of position inside the bowl 1. Methods for performing such calculations are known themselves. The resulting amplitude of the generated sound as a function of position can be represented in the form of a 3D or 2D image.

[0041] Figure 5 shows the results of experiments on the surface of a transducer with different exemplary surface configurations. The ultrasonic signal levels resulting from photoacoustic conversion on the transducer surface are shown. The transducer was mounted in a holder similar to a basin. A fluctuating near-infrared wavelength light pulse was supplied to the transducer in the holder. A 3D photoacoustic imager was used to measure the ultrasonic signal induced by irradiating the transducer.

[0042] The signal levels were determined within the 3D photoacoustic reconstruction image by calculating the root mean square (RMS) of the reconstructed initial pressure levels across thin (2.4 mm) cylindrical deposits extending radially (7.2 mm) over patch radii (e.g., 6 mm) larger than the 5 mm radius of the transducer surface, to capture all signals generated from the patch, centered on the transducer surface. The signal levels were normalized for each wavelength to the average signal level (b) of the directly deposited surface.

[0043] Different curves are obtained using an acoustic-electron converter 14(c) covered with a copper foil patch with gold coating, an acoustic-electron converter 14(b) with gold coating directly on the surface of the acoustic-electron converter 14, and an acoustic-electron converter 14(a) without gold coating.

[0044] As can be seen in the figure, the gold-coated copper foil patch 16(c) results in a significant reduction in photoacoustic amplitude. A transducer without a reflective layer (i.e., the receiving layer is directly exposed to the irradiating light) generates a signal level 2.6 times higher than a transducer with a surface where a 1-micrometer gold layer is directly deposited via sputter deposition. The transducer with the gold-coated copper patch generates a signal level that is further reduced by an average of 2.8 times.

[0045] While a logical explanation is not necessarily required to implement these reductions, tentatively, the reduction in photoacoustic amplitude can be assumed to be due to a reduction in multiple reflections (and their associated absorptions) from the gold coating as a result of improved smoothness of the gold coating when the gold coating is provided on the copper foil rather than directly on the acoustic-electron converter 14. Next, the improved smoothness of the gold coating is due to the fact that the copper foil facilitates the provision of a smoother substrate for the gold coating than the acoustic-electron converter 14.

[0046] Bergstrom's Journal of Applied Physics 103, 103515 (2008): "The absorption of light by rough metal surfaces_a three-dimensional ray-tracing analysis" presents simulation results of the relationship between reflection and surface smoothness (expressed using surface roughness). To represent this relationship, surface roughness can be characterized using the root mean square (RMS) gradient of the surface (the square root of the spatial mean of the sum of the squares of dh / dx and dh / dy, where h is the surface height and dh / dx and dh / dy are the derivatives of the height along different directions on the surface). Assuming a Gaussian height distribution, the RMS gradient is equal to the following: Sqrt(2) * sigma / L

[0047] In the above equation, sigma is the root mean square of the height h, and L is the correlation length of the height (see Bergstrom). The RMS gradient can be determined by a profilometer, for example, optical profilometer observation via a microscope. For example, the RMS gradient can be determined via RΔq measured using a profilometer according to the definition and method in [ISO 3287:1997]. Note that the RΔq value is a multiple of the square root that is twice as large as the RMS gradient definition used by Bergstrom.

[0048] Simulations involving perpendicular or near-perpendicular (less than 30 degrees from perpendicular) incident light in the following cases have shown that multiple reflections associated with generating photoacoustic signals on the surface are largely prevented or at least significantly reduced. RMS gradient < 0.42 (approximately 0.3) * sqrt(2))

[0049] Light absorption exceeding this value due to multiple reflections increases significantly. An RMS gradient of 0.42 can be estimated to produce a normalized RMS photoacoustic signal of approximately 0.35 in a configuration using gold coating. As can be seen in Figure 5, a gold layer deposited on a converter without copper foil results in a considerably higher photoacoustic signal due to light absorption.

[0050] More preferably, this RMS gradient is at most 0.1. For a thin coating layer on an underlying foil, this maximum value formally applies to the surface of the coating layer. However, if the underlying foil has at most this maximum RMS gradient value, this usually ensures that the RMS gradient of the coating is also smaller than this maximum value. The RMS gradient of a thin coating layer is substantially the same as or slightly lower than the RMS gradient of the underlying foil, and becomes even smaller as the thickness of the coating increases. The RMS gradient of cold-rolled copper foil (and other metal foils) satisfies this requirement. Copper foil usable on printed circuit boards can be used to achieve RMS gradient values ​​below 0.42 and 0.1. Even smoother copper foil is usable for printed circuit boards in the GHz range.

[0051] Experiments revealed that the RMS gradient with gold directly deposited on the transducer surface was 2.1, considerably higher than the value required to prevent or at least significantly reduce multiple reflections. In contrast, the gold coating on copper foil produced a sufficiently low RMS gradient of at most 0.1, which is sufficient to prevent or at least significantly reduce multiple reflections.

[0052] In one experiment, the photoacoustic amplitude as a function of position on and around the acoustic transducer was measured using an acoustic transducer in an aperture via a segment of the wall structure, by suspending a segment of the wall structure within bowl 1. The photoacoustic amplitude as a function of position was reconstructed using measurements with an acoustic transducer 14 within the basic structure of the bowl. The resulting image shows a ring of photoacoustic amplitude around the acoustic transducer in the aperture via the segment of the wall structure. The root mean square (rms) amplitude of this ring decreased by approximately twofold when a gold-coated copper foil patch extended through the gap between the acoustic transducer in the aperture and the segment of the wall structure. This decrease can be attributed to preventing light from reaching the gap between the acoustic transducer and the wall structure. The remaining lower rms amplitude ring of photoacoustic amplitude appears to be associated with the edge of the patch. This rms amplitude can be reduced by rounding the edge of the patch.

[0053] Figure 6 shows an embodiment in which a conductive layer 50 is provided between the adhesive of patch 16 and the surface of the acoustic-electronic transducer 14. Alternatively, the conductive layer 50 can be a copper layer of the patch, where the adhesive layer of patch 16 is conductive. The conductive layer 50 or the adhesive layer of patch 16 is electrically connected to the bowl base structure 10, which is also conductive. This allows for the use of a conductive layer 50 and / or copper foil to isolate the transducer 14 from external electromagnetic interference.

[0054] The acoustic-electronic transducer 14 may have a conductive housing 54 around the vertical axis of the receiving surface. Conductive housing 54. In an embodiment, the housing 54 is electrically connected to the conductive layer 50.

Claims

1. A basin to receive the tissue to be imaged, A light source configured to supply light into the basin, A plurality of acoustic-electronic transducers, each of the plurality of transducers having a sound-receiving surface that forms a portion of the surface of the basin at different positions within the surface of the basin, each having a foil bonded to the receiving surface and a reflective coating provided on the basin side of the foil, A photoacoustic imaging device comprising, The surface of the basin is formed by a basic structure having an opening, The acoustic electronic converter extends through the opening of the basic structure, The photoacoustic imaging device comprises patches of the foil, each patch passing through one of the plurality of acoustic-electron converters.

2. The foil is a metal foil, The photoacoustic imaging device according to claim 1, wherein the reflective coating is made of a material that is more reflective than the material of the metal foil with respect to the light from the light source.

3. The photoacoustic imaging device according to claim 1, wherein each of the patches extends from the receiving surface of the acoustic-electron transducer to the surface of the basic structure around the opening through which the acoustic-electron transducer extends.

4. The photoacoustic imaging device according to any one of claims 1 to 3, wherein the reflective coating is a gold coating.

5. The photoacoustic imaging device according to claim 4, wherein the gold coating has a thickness between 0.1 and 2 micrometers.

6. The photoacoustic imaging device according to claim 4, wherein the foil is a copper foil.

7. The photoacoustic imaging device according to claim 6, further comprising a nickel layer between the gold coating and the copper foil.

8. The photoacoustic imaging device according to claim 7, wherein the nickel layer has a thickness of at least 2 micrometers.

9. The photoacoustic imaging device according to claim 6, wherein the copper foil has a thickness between 1 and 100 micrometers.

10. The photoacoustic imaging device according to any one of claims 1 to 3, wherein the foil is bonded to the receiving surface by an acrylic adhesive or a silicone-based adhesive.

11. The acoustic electronic converter has a conductive housing around the vertical axis of the receiving surface, The foil is a metal foil, The photoacoustic imaging device according to any one of claims 1 to 3, wherein the conductive housing is electrically connected to the metal foil.

12. A method for installing an acoustic-electron transducer within a photoacoustic imaging device, wherein the photoacoustic imaging device comprises a basic structure that defines a surface of a basin for receiving tissue to be imaged, and the basic structure defines an opening within the surface of the basin. The aforementioned method, The acoustic electronic converter is mounted in a position where it extends through the opening such that the sound-receiving surface of the acoustic electronic converter forms a part of the surface of the basin, and subsequently, This includes adhering a foil to the sound-receiving surface, wherein the foil has a reflective coating on the surface facing the interior of the basin, The method wherein the foil is a patch of foil extending from the receiving surface of the acoustic-electron transducer to the surface of the basic structure around the opening through which the first of the acoustic-electron transducers extends.

13. The method according to claim 12, wherein the foil has a layer of adhesive on a further side surface facing the sound-receiving surface.

14. Each foil patch is attached to the sound-receiving surface of each acoustic electron transducer extending through all of the openings. The method according to claim 12 or 13, wherein each of the foil patches has a reflective coating on the surface facing the interior of the basin.

Images