Thermoacoustic measurement probe

Abstract

The thermoacoustic measurement probe may include an open hollow radio frequency (RF) waveguide; and a thermoacoustic transducer wherein the open hollow RF waveguide is in the form of a sleeve, surrounds and is mechanically connected to the thermoacoustic transducer.

Description

Technical Field

[0001] The present disclosure implements a thermoacoustic measurement probe. Specifically, the present disclosure discusses a structural configuration that enables a radio frequency (RF) waveguide portion of the probe to surround a thermoacoustic transducer portion.

[0002] background

[0003] In high frequency systems, waveguides are often used to guide electromagnetic waves or sound with minimal energy loss by limiting the expansion of electromagnetic waves propagating in the waveguide to one or two dimensions. Depending on the nature of the electromagnetic waves to be propagated, the waveguide can take different forms. In addition, in many cases, filters are used to allow electromagnetic waves at certain frequencies to pass and travel along the waveguide while rejecting electromagnetic waves at other frequencies. An example is a hollow, open conductive waveguide, which is often used to guide radio frequency (RF) waves. In some cases, in order to provide the desired filtering, these hollow metal waveguides are equipped with solid inserts formed of high dielectric constant materials.

[0004] Waveguides, such as those described above, have been employed in thermoacoustic imaging systems. Thermoacoustic imaging is a form of imaging that provides information related to the thermoelastic properties of tissue. Thermoacoustic imaging uses short pulses of electromagnetic energy, such as RF pulses, that are directed into a medium to rapidly heat heat absorbing features within the medium, which in turn cause acoustic pressure waves that are detected using an acoustic receiver, such as one or more thermoacoustic or ultrasonic transducer arrays. The detected acoustic pressure waves are analyzed by signal processing and processed to be presented as a thermoacoustic image that can be interpreted by an operator.

[0005] In order to guide the RF pulses into the medium during thermoacoustic imaging, an RF applicator using a waveguide is coupled to tissue adjacent to the region of interest (ROI) within the medium to be imaged. Suboptimal coupling of the RF applicator to the tissue may cause problems (e.g., inefficient energy transfer, reduced heating rate, reduced signal strength, uneven energy deposition, tissue hot spots, tissue overheating, RF power supply damage, and poor image quality). Factors that lead to suboptimal coupling of the RF applicator to the tissue include variability in the size of the medium, the size of the tissue within the medium, the geometry of the tissue within the medium, the composition of the tissue within the medium, etc.

[0006] In a thermoacoustic probe, an RF applicator or RF antenna is used to send RF energy into the medium of interest, and an acoustic receiver is used to pick up the resulting thermoacoustic waves. The RF applicator and acoustic receiver are usually configured side by side, integrated into a single handheld probe.

[0007] A side-by-side configuration may result in lower thermoacoustic signal strength, thus reducing the effectiveness of the thermoacoustic measurement. This is because the signal strength and range of the imageable area depends on the extent of overlap between the RF applicator beam and the directivity pattern of the acoustic receiver.

[0008] Another disadvantage of the side-by-side configuration for thermoacoustic probes is that RF interference from the RF applicator can also adversely affect signal quality.

[0009] A third disadvantage of a side-by-side configuration for thermoacoustic probes may be that stray acoustic signals (eg, RF applicator plane waves) are strong and detrimental to acoustic signal fidelity.

[0010] In a side-by-side configuration, one proposed solution is to tilt the acoustic receiver relative to the RF applicator. This approach may allow for better overlap, but only to a certain depth. Unfortunately, this does not improve RFI or reduce the large plane wave artifacts (unwanted signal noise) that appear.

[0011] Another proposed solution is to separate the receiver and applicator into two different devices, which can increase signal strength and reduce artifacts. Unfortunately, this approach introduces multiple complexities and higher variability because the operator now needs to manipulate two devices simultaneously, which presents a huge obstacle to the standard of care clinical workflow.

[0012] Therefore, there is a need to develop a novel structured thermoacoustic probe configuration that overcomes the limitations inherent in the side-by-side thermoacoustic probe configuration.

[0013] Overview

[0014] In one embodiment, the thermoacoustic measurement probe may include an open hollow RF waveguide and a thermoacoustic transducer, wherein the open hollow RF waveguide is in the form of a sleeve surrounding the thermoacoustic transducer and mechanically connected to the thermoacoustic transducer.

[0015] An open hollow RF waveguide in the form of a sleeve may surround and mechanically connect to the thermoacoustic transducer via an insulator that protects the thermoacoustic transducer from acoustic and electrical interference emanating from the open hollow RF waveguide.

[0016] The thermoacoustic transducer and the open hollow RF waveguide may form a circular cross-sectional shape.

[0017] The thermoacoustic transducer and the open hollow RF waveguide may form an elliptical cross-sectional shape.

[0018] The sensor of the thermoacoustic transducer may have a circular cross-sectional shape.

[0019] The sensor of the thermoacoustic transducer may have an elliptical cross-sectional shape.

[0020] The sensor of the thermoacoustic transducer may have a rectangular cross-sectional shape.

[0021] The end of the sensor of the thermoacoustic transducer may have a conical shape.

[0022] In another embodiment, a thermoacoustic measurement probe may include a radio frequency (RF) waveguide having a cavity and a thermoacoustic transducer positioned in the cavity of the RF waveguide.

[0023] The cavity of the RF waveguide may have a circular cross-sectional shape.

[0024] The cavity of the RF waveguide may have an elliptical cross-sectional shape.

[0025] The cavity of the RF waveguide may have a rectangular cross-sectional shape.

[0026] The sensor of the thermoacoustic transducer may have a circular cross-sectional shape.

[0027] The sensor of the thermoacoustic transducer may have an elliptical cross-sectional shape.

[0028] The sensor of the thermoacoustic transducer may have a rectangular cross-sectional shape.

[0029] The sensor of the thermoacoustic transducer may have a conical shape.

[0030] A ceramic may be positioned in the cavity.

[0031] Acoustic isolation may be positioned within the ceramic.

[0032] The thermoacoustic measurement probe may include an RF feed coupled to the RF waveguide, and a connector coupled to the thermoacoustic transducer via an opening in the RF waveguide.

[0033] In yet another embodiment, the thermoacoustic measurement probe may include a cylindrical radio frequency (RF) waveguide housing; a cylindrical ceramic located inside the cylindrical RF waveguide housing; a cylindrical acoustic isolation member inside the cylindrical ceramic; and a thermoacoustic sensor located at an end of the cylindrical acoustic isolation member.

[0034] It should be understood that this summary is provided to introduce a selection of concepts in simplified form that are further described below in the Detailed Description. This summary is not intended to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments will now be described more fully with reference to the accompanying drawings, in which:

[0037] Figure 1 is a block diagram of a thermoacoustic system according to an embodiment.

[0038] Figure 2 is a cross-sectional side view of an RF applicator and an acoustic receiver configured side by side according to an embodiment.

[0039] Figure 3 is a cross-sectional side view of an RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0040] Figure 4 is a signal divergence comparison between a standard RF applicator used in the prior art and the sleeve RF applicator of the present application.

[0041] Figure 5A is a front view of a first RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0042] Figure 5B is a perspective view of a first RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0043] Figure 5C is a side view of a first RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0044] Figure 5D is a top view of a first applicator and acoustic receiver sleeve configuration according to an embodiment.

[0045] Fig. 6A is a front view of a second RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0046] Figure 6B is a perspective view of a second RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0047] Figure 6C is a side view of a second RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0048] Fig.6D is a top view of a second applicator and acoustic receiver sleeve configuration according to an embodiment.

[0049] Fig. 7A is a front view of a third RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0050] Figure 7B is a perspective view of a third RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0051] Figure 7C is a side view of a third RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0052] Fig.7Dis a top view of a third applicator and acoustic receiver sleeve configuration according to an embodiment.

[0053] Fig. 8A is a front view of a fourth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0054] Figure 8B is a perspective view of a fourth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0055] Figure 8C is a side view of a fourth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0056] Fig.8D is a top view of a fourth applicator and acoustic receiver sleeve configuration according to an embodiment.

[0057] Fig.9A is a front view of a fifth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0058] Fig. 9B is a perspective view of a fifth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0059] Fig. 9C is a side view of a fifth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0060] Fig.9D is a top view of a fifth applicator and acoustic receiver sleeve configuration according to an embodiment.

[0061] Fig. 10A is an exploded isometric view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0062] Fig. 10B is an exploded side view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0063] Fig. 10C is an exploded top view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0064] Fig. 10D is an exploded side view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0065] Fig.11A is an alternative exploded isometric view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0066] Fig. 11B is an alternative exploded side view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0067] Fig. 11C is an alternative exploded top view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0068] Fig.11D is an alternative exploded side view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0069] Fig. 12A is an exploded isometric view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0070] Fig. 12B is an exploded side view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0071] Fig. 12C is an exploded top view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0072] Fig.12D is an exploded side view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0073] Fig.13A is an alternative exploded isometric view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0074] Fig. 13B is an alternative exploded side view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0075] Fig. 13C is an alternative exploded top view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0076] Fig.13D is an alternative exploded side view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0077] Fig.14 is a contour map showing the electric field strength (in decibels) of the RF applicator with respect to different tissue types.

[0078] Fig.15 The electric field in the RF applicator is shown in volts per meter.

[0079] Fig.16 The reflected power (in decibels) of the RF applicator at the target frequency is shown.

[0080] Detailed Description

[0081] Embodiments herein describe a thermoacoustic measurement probe having an RF waveguide surrounding a thermoacoustic transducer, and a housing of the thermoacoustic measurement probe accommodating both the RF waveguide and the thermoacoustic transducer.

[0082] The embodiments herein describe an improved method and system. Rather than utilizing an open RF waveguide and a separate acoustic receiver, the embodiments discussed herein may utilize an open hollow RF waveguide, wherein the hollow portion is a cavity that is constructed for the acoustic receiver and any additional electronics to be mounted within the cavity. This configuration may allow the acoustic receiver (thermoacoustic transducer) and any additional electronics to be mechanically mounted within the hollow cavity. The open RF waveguide may be configured in the form of a sleeve that may partially or completely surround the acoustic receiver. The RF waveguide may also be mechanically joined to the acoustic receiver.

[0083] The use of hollow RF waveguides is not typically used with components (such as thermoacoustic transducers) in the hollow portion, as the components may affect the field and operation of the RF waveguide. In the embodiments described herein, the RF waveguide may be configured to have a zero field (null) region in the hollow portion.

[0084] An unexpected result of placing the acoustic receiver within the hollow cavity of an open hollow RF waveguide is that it allows for maximum overlap between the RF beam and the directivity pattern of the acoustic receiver.

[0085] Another unexpected result of utilizing an open hollow RF waveguide is the very low electromagnetic fields inside the hollow cavity. Placing the acoustic receiver inside the cavity (inside the sleeve) significantly reduces RF interference.

[0086] Another unexpected result is that the hollow RF waveguide has a highly divergent beam pattern near the RF waveguide. This in turn produces a divergent applicator plane wave that quickly disperses.

[0087] An unexpected result is that the hollow RF waveguide allows for a smaller overall thermoacoustic measurement probe size, since the electronics and acoustic receivers can be placed inside the hollow cavity.

[0088] The cross-sectional shape of the hollow portion of the open hollow RF waveguide can be any shape, including circular, elliptical, non-concentric tubes or tapered tubes. The open portion can contain a ceramic filler. In one embodiment, metal fins can be included in the ceramic filler or mounted on the RF waveguide to increase the frequency bandwidth in which the RF applicator can effectively operate.

[0089] Now turn to Figure 1, an imaging system is shown and generally identified by reference numeral 100. As can be seen, the imaging system 100 includes a programmed computing device 102 communicatively coupled to an ultrasound imaging system 104 and a thermoacoustic imaging system 106. The ultrasound imaging system 104 and the thermoacoustic imaging system 106 are configured to obtain ultrasound image data and thermoacoustic image data of a region of interest (ROI) 116, respectively.

[0090] The programmed computing device 102 in this embodiment can be a personal computer, a server, or other suitable processing device, including, for example, a processing unit, which includes one or more processors, a computer-readable system memory (volatile and / or non-volatile memory), other non-removable or removable computer-readable memory (e.g., a hard drive, RAM, ROM, EEPROM, CD-ROM, DVD, flash memory, etc.), and a system bus that couples various computer components to the processing unit. The computing device 102 can also include networking capabilities using Ethernet, Wi-Fi, and / or another suitable network format to be able to connect to a shared or remote drive, one or more networked computers, or other networked devices. One or more input devices, such as a mouse and keyboard (not shown), are coupled to the computing device 102 for receiving operator input. A display device (not shown), such as one or more computer screens or monitors, can be coupled to the computing device 102 for displaying one or more generated images, which are based on the ultrasound image data received from the ultrasound imaging system 104 and / or the thermoacoustic image data received from the thermoacoustic imaging system 106. The programmed computing device 102 executes program code stored on the computer-readable system memory and / or other non-removable or removable computer-readable memory and performs methods according to the program code, as further described below.

[0091] The ultrasound imaging system 104 includes an acoustic receiver in the form of an ultrasound transducer 108, which houses one or more ultrasound transducer arrays configured to transmit sound waves into the region of interest 116. The sound waves directed into the region of interest 116 echo from the materials in the region of interest, where different materials reflect sound to different degrees. The echoes received by one or more ultrasound transducer arrays of the ultrasound transducer 108 are processed by the ultrasound imaging system 104. The ultrasound imaging system 104 transmits ultrasound image data to the computing device 102 for further processing and for presentation on a display device as an ultrasound image that can be interpreted by an operator. In one embodiment, the ultrasound imaging system 104 utilizes B-mode ultrasound imaging technology assuming a nominal sound speed of 1540 m / s. Since ultrasound imaging systems are known in the art, additional details of the ultrasound imaging system 104 will not be further described herein.

[0092] Thermoacoustic imaging system 106 includes an acoustic receiver in the form of a thermoacoustic transducer 110. Thermoacoustic transducer 110 houses one or more thermoacoustic transducer arrays. Figure 1 10 is shown as a separate component, but a radio frequency (RF) applicator (or waveguide) 112 can be housed, combined or integrated with the thermoacoustic transducer 110. The RF applicator 112 is configured to emit short RF energy pulses directed into the region of interest 116. In one embodiment, the RF applicator 112 has a frequency between about 10 MHz and 100 GHz and has a pulse duration between about 0.1 nanoseconds and 10 microseconds. The RF applicator 112 emits RF energy pulses to the material or tissue within the region of interest 116 to induce acoustic pressure waves (thermoacoustic multipole signals) within the region of interest 116, which are detected by the thermoacoustic transducer 110. The acoustic pressure waves detected by the thermoacoustic transducer 110 are processed and transmitted to the computing device 102 as thermoacoustic image data for further processing and presentation on a display device as a thermoacoustic image that can be interpreted by an operator.

[0093] The coordinate system of the one or more ultrasonic transducer arrays of the ultrasonic transducer 108 and the coordinate system of the one or more thermoacoustic transducer arrays of the thermoacoustic transducer 110 are mapped by the computing device 102 so that the acquired ultrasound image and the thermoacoustic image can be registered. Alternatively, the thermoacoustic imaging system 106 can utilize the one or more ultrasonic transducer arrays of the ultrasonic transducer 108 by disconnecting the one or more ultrasonic transducer arrays from the ultrasonic transducer 108 and connecting the one or more ultrasonic transducer arrays to the thermoacoustic transducer 110. As will be appreciated, by doing so, coordinate mapping between the one or more ultrasonic transducer arrays and the one or more thermoacoustic transducer arrays is not required.

[0094] In one embodiment (such as Figure 1 ), the region of interest 116 contains blood vessels 102 and is located within a liver 130 of a human or animal body (patient) 114. The patient 114 includes a subcutaneous fat layer 118 and a muscle layer 120 adjacent to the liver 130. The distance shown is: d f is the patient's subcutaneous fat thickness 122, d m is the patient's muscle thickness 124, d b is the distance from the boundary between the muscle and the liver to the center of the blood vessel 126.

[0095] Figure 22 is a cross-sectional side view of an embodiment of a side-by-side configuration of an RF applicator and an acoustic receiver. A thermoacoustic transducer 210 including a thermoacoustic sensor 202 and a thermoacoustic electronics 204 is shown, as well as an RF applicator 212 including an RF waveguide 206, an RF matching layer 208, and an RF applicator filler 214. Figure 2 In a side-by-side configuration, the area / volume of electric field of sufficient size to generate the thermoacoustic signal and the area / volume of receiver sensitivity for detecting and utilizing the thermoacoustic signal have a small overlap region. Therefore, the thermoacoustic analysis occurs within this small overlap region.

[0096] The thermoacoustic transducer can be configured to be housed within a cavity formed by the RF applicator. In one example, Figure 3 3 is a cross-sectional side view of an RF applicator and acoustic receiver configuration. An open hollow RF applicator 312, an open hollow waveguide body 316, an open hollow waveguide matching layer 306, an open hollow waveguide filler 308, a thermoacoustic transducer 310, a thermoacoustic sensor 302, thermoacoustic electronics 304, and an insulator 314 (providing both acoustic and electromagnetic insulation) are shown. In this embodiment, the thermoacoustic transducer 310 is positioned within the interior region of the open hollow RF applicator 312. Figure 3 In this configuration, the area / volume of the electric field having a sufficient size to generate the thermoacoustic signal and the area / volume of the receiver sensitivity for detecting and utilizing the thermoacoustic signal have the same Figure 2 Compared to the larger overlap area.

[0097] Figure 4 Shows Figure 2 The conventional RF applicator shown in Figure 3 . RF applicator 212 is shown as a solid RF applicator with a large aperture and slow RF energy divergence. Open hollow RF applicator 312 is shown as having a small aperture for transmitting RF energy and fast divergence of RF energy. The divergence of RF energy is inversely proportional to the antenna aperture: the smaller the aperture, the larger the divergence angle, and vice versa. Figure 4 As shown in , the open hollow RF applicator 312 has a smaller aperture and this produces a larger divergence of the RF energy from the applicator radiating surface.

[0098] FIG. 5A to FIG. 5D An RF applicator according to an embodiment is shown. Figure 5A is a front view of an embodiment of an RF applicator and acoustic receiver sleeve configuration. Figure 5B is a perspective view of an embodiment of an RF applicator and acoustic receiver sleeve configuration. A hollow cavity 502, an open hollow waveguide matching layer 506, an open hollow waveguide body 508, and an RF energy feed 504 are shown. Figure 5C is a side view of an embodiment of an RF applicator and acoustic receiver sleeve configuration. Figure 5D is a top view of an embodiment of an applicator and acoustic receiver sleeve configuration. FIG. 5A to FIG. 5D In the illustration of , the hollow cavity 502 is configured to receive an acoustic receiver (thermoacoustic transducer). The RF applicator can be considered an acoustic receiver sleeve because it is at least partially hollow and is configured to accommodate an acoustic receiver (not shown) in the opening. The acoustic receiver can fill all or a portion of the hollow cavity 502, and any portion of the hollow cavity 502 not filled by the acoustic receiver can be at least partially filled with another material (e.g., an insulator).

[0099] like FIG. 5A to FIG. 9D As shown in the examples of , the RF applicator and the acoustic receiver can have different shapes and configurations. The RF applicator can be circular, elliptical, or other configurations with an open portion (e.g., a cavity) for receiving the acoustic receiver. The acoustic receiver can have a rectangular, circular, elliptical, or other shaped cross-section, and can have a rectangular, spherical, conical, or other shaped end. FIG. 5A to FIG. 9D These are intended to be examples of configurations, and potential configurations are not limited to these specific examples. The shape may be selected based on the desired application or manufacturing process.

[0100] In one configuration, the acoustic receiver may have a rectangular shape and be positioned within the RF applicator, such as FIG. 6A to FIG. 6D as shown in . Fig. 6A is a front view of a second RF applicator and acoustic receiver sleeve configuration embodiment. Figure 6B is a perspective view of a second RF applicator and acoustic receiver sleeve configuration embodiment. An open hollow waveguide matching layer 606, an open hollow waveguide body 608, an RF energy feed 604, an insulator 610, and a rectangular acoustic receiver 602 (having a rectangular cross-section) are shown. Figure 6C is a side view of a second RF applicator and acoustic receiver sleeve configuration embodiment. Fig.6D is a top view of a second applicator and acoustic receiver sleeve configuration embodiment.

[0101] In another configuration, the acoustic receiver may have a conical shape and be positioned in the RF applicator, such as FIG. 7A to FIG. 7D as shown in . Fig. 7A is a front view of a third RF applicator and acoustic receiver sleeve configuration embodiment. Figure 7B is a perspective view of a third RF applicator and acoustic receiver sleeve configuration embodiment. An open hollow waveguide matching layer 706, an open hollow waveguide body 708, an RF energy feed 704, an insulator 710, and a conical acoustic receiver 702 (with a circular cross-section) are shown. Figure 7C is a side view of a third RF applicator and acoustic receiver sleeve configuration embodiment. Fig.7D is a top view of a third applicator and acoustic receiver sleeve configuration embodiment.

[0102] In another configuration, the acoustic receiver may have a rectangular shape and be positioned within an oval shaped RF applicator, such as FIG. 8A to FIG. 8D as shown in . Fig. 8A is a front view of a fourth RF applicator and acoustic receiver sleeve configuration embodiment. Figure 8B 804, is a perspective view of a fourth RF applicator and acoustic receiver sleeve configuration embodiment. An open hollow elliptical waveguide matching layer 806, an open hollow elliptical waveguide body 808, an RF energy feed 804, an insulator 810, and a rectangular acoustic receiver 802 (having a rectangular cross-section) are shown. Figure 8C is a side view of a fourth RF applicator and acoustic receiver sleeve configuration embodiment. Fig.8D is a top view of a fourth applicator and acoustic receiver sleeve configuration embodiment.

[0103] In another configuration, the acoustic receiver may have a conical shape and be positioned within an elliptical shaped RF applicator, such as 9A to 9D as shown in . Fig.9A is a front view of a fifth RF applicator and acoustic receiver sleeve configuration embodiment. Fig. 9B 906, an open hollow elliptical waveguide matching layer 906, an open hollow elliptical waveguide body 908, an RF energy feed 904, an insulator 910, and a conical acoustic receiver 902 (with a circular cross-section) are shown. Fig. 9C is a side view of a fifth RF applicator and acoustic receiver sleeve configuration embodiment. Fig.9D is a top view of a fifth applicator and acoustic receiver sleeve configuration embodiment.

[0104] FIG. 10A to FIG. 11D A configuration with a circular acoustic receiver and a rectangular waveguide is shown, as FIG. 6A to FIG. 6D as shown in . Fig. 10A is a perspective exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 10B is a side exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 10C is a top exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 10D is a side exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0105] The waveguide housing 1008 holds a ceramic 1016. The waveguide matching layer 1006 abuts the ceramic 1016 at a first end of the waveguide housing 1008. An acoustic isolator 1010 is positioned inside the waveguide housing 1008. An inner Faraday cage 1012 is positioned inside the acoustic isolator 1010. The acoustic isolator 1010 may include cork, foam, or the like, and it may be secured to the ceramic 1016. In some configurations (not shown), an air gap may be used. The inner Faraday cage 1012 is aligned with the thermoacoustic sensor 1002 having a seal 1014. Although the sensor 1002 is shown as having a rectangular shape and a seal 1014 constructed for a rectangular shaped sensor 1002, it is intended that the configuration may be applicable to sensors of other shapes. The waveguide housing 1008 is coupled to an RF energy feed 1004. A shield connector 1018 for the internal Faraday cage 1012 is positioned at the second end of the waveguide housing 1008 .

[0106] FIG. 11A to FIG. 11D From the alternative perspective FIG. 10A to FIG. 10D parts. Fig.11A is an alternative perspective exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 11B is an alternative exploded side view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 11C is an alternative top exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig.11D is an alternative side exploded view of a sixth RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0107] FIG. 12A to FIG. 13D A configuration with a circular acoustic receiver and a rectangular waveguide is shown, as FIG. 6A to FIG. 6D as shown in . Fig. 12A is a perspective exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 12B is a side exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 12C is a top exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig.12D is a side exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0108] The waveguide housing 1208 holds the ceramic 1216. An acoustic isolator 1210 is positioned inside the waveguide housing 1208. At one end of the acoustic isolator 1210 is a thermoacoustic sensor (without a lens) 1202. Although the sensor 1202 is shown as having a rectangular shape, it is intended that the configuration can be adapted for sensors of other shapes. Positioned on the sensor 1202 is a front non-conductive seal 1214, a thin conductive layer 1220, an electromagnetic matching layer 1222, and an acoustic lens 1224. The waveguide housing 1208 is coupled to the RF energy feed 1204. A shielded connector 1218 and a rear conductive seal 1226 are positioned at the second end of the waveguide housing 1208.

[0109] FIG. 13A to FIG. 13D From the alternative perspective FIG. 12A to FIG. 12D parts. Fig.13A is an alternative perspective exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 13B is an alternative side exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig. 13C is an alternative top exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment. Fig.13D is an alternative side exploded view of a seventh RF applicator and acoustic receiver sleeve configuration according to an embodiment.

[0110] Fig.14 14 is a contour plot showing the electric field strength (in decibels) of the open hollow RF applicator 312 in terms of different tissue types. The electric field is shown as leaving the open hollow RF applicator 312 and traveling through the skin layer 1402, the fat layer 1404, the muscle layer 1406, and the liver layer 1408. Contour 1410 is 61 decibels, contour 1412 is 53 decibels, contour 1414 is 46 decibels, contour 1416 is 23 decibels, contour 1418 is 15 decibels, and contour 1420 is 7 decibels. The peak electric field is shown near the exit of the open hollow RF applicator 312. As the electric field diverges through the tissue, the electric field becomes strongest near the central axis 1422 of the thermoacoustic probe. Both contour lines 1418 and 1420 are located in the liver layer 1408 and are strongest near the central axis 1422 of the thermoacoustic probe.

[0111] Fig.15 The electric field in the RF applicator is shown in volts / meter. The hollow cavity 502 has a very low electric field, less than 400 volts / meter. In contrast, the open hollow RF applicator 312 has an electric field greater than 1600 volts / meter. The electric field generated in the open hollow RF applicator 312 cancels itself out in the hollow cavity 502 due to the symmetrical nature (sleeve shape) of the open hollow RF applicator 312 surrounding the hollow cavity 502.

[0112] Fig.16 The reflected power (in decibels) of the open hollow RF applicator 312 at the target frequency is shown. Fig.16 The reflection coefficient of the open hollow RF applicator 312 at a reference impedance of 50 ohms is shown versus frequency. The reflection coefficient represents the amount of power (i.e., reflected power) transmitted from a 50 ohm source into the open hollow RF applicator 312. At 434 MHz (the design frequency of the open hollow RF applicator 312), the reflection coefficient is -26 dB, which corresponds to 99.75% of the power from the 50 ohm source being transmitted to the open hollow RF applicator 312.

[0113] Although the embodiments have been described above with reference to the accompanying drawings, those skilled in the art will appreciate that changes and modifications may be made without departing from the scope defined by the appended claims.

Claims

1. A thermoacoustic measurement probe, comprising: an open hollow radio frequency (RF) waveguide; and Thermoacoustic transducers; Wherein, the open hollow RF waveguide is in the form of a sleeve, surrounding the thermoacoustic transducer and mechanically connected to the thermoacoustic transducer.

2. The thermoacoustic measurement probe according to claim 1, wherein: The thermoacoustic transducer and the open hollow RF waveguide form a circular cross-sectional shape.

3. The thermoacoustic measurement probe according to claim 1, wherein: The thermoacoustic transducer and the open hollow RF waveguide form an elliptical cross-sectional shape.

4. The thermoacoustic measurement probe according to claim 1, wherein: The thermoacoustic transducer and the open hollow RF waveguide form a rectangular cross-sectional shape.

5. The thermoacoustic measurement probe according to claim 1, wherein: The sensor of the thermoacoustic transducer has a circular cross-sectional shape.

6. The thermoacoustic measurement probe according to claim 1, wherein: The sensor of the thermoacoustic transducer has an elliptical cross-sectional shape.

7. The thermoacoustic measurement probe according to claim 1, wherein: The sensor of the thermoacoustic transducer has a rectangular cross-sectional shape.

8. The thermoacoustic measurement probe according to claim 1, wherein: The end of the sensor of the thermoacoustic transducer has a conical shape.

9. A thermoacoustic measurement probe, comprising: A radio frequency (RF) waveguide having a cavity; and A thermoacoustic transducer is positioned in the cavity of the RF waveguide.

10. The thermoacoustic measurement probe according to claim 9, wherein: The cavity of the RF waveguide has a circular cross-sectional shape.

11. The thermoacoustic measurement probe according to claim 9, wherein: The cavity of the RF waveguide has an elliptical cross-sectional shape.

12. The thermoacoustic measurement probe according to claim 9, wherein: The cavity of the RF waveguide has a rectangular cross-sectional shape.

13. The thermoacoustic measurement probe according to claim 9, wherein: The sensor of the thermoacoustic transducer has a circular cross-sectional shape.

14. The thermoacoustic measurement probe according to claim 9, wherein: The sensor of the thermoacoustic transducer has an elliptical cross-sectional shape.

15. The thermoacoustic measurement probe according to claim 9, wherein: The sensor of the thermoacoustic transducer has a rectangular cross-sectional shape.

16. The thermoacoustic measurement probe according to claim 9, wherein: The end of the sensor of the thermoacoustic transducer has a conical shape.

17. The thermoacoustic measurement probe according to claim 9, wherein: A ceramic is positioned in the cavity.

18. The thermoacoustic measurement probe according to claim 17, wherein: Acoustic insulation is positioned in the ceramic.

19. The thermoacoustic measurement probe of claim 9, further comprising an RF feed coupled to the RF waveguide, and a connector coupled to the thermoacoustic transducer via an opening in the RF waveguide.

20. A thermoacoustic measurement probe, comprising: A cylindrical radio frequency (RF) waveguide housing; a cylindrical ceramic located inside the cylindrical RF waveguide housing; a cylindrical acoustic isolation member inside the cylindrical ceramic; and A thermoacoustic sensor is located at an end of the cylindrical acoustic isolation member.

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