Method and system for performing imaging using a low-frequency electromagnetic field

Abstract

This disclosure relates to a system and method for imaging an object of interest. The system includes a low-frequency radiation source for transmitting a set of low-frequency electromagnetic waves toward an object of interest, wherein the size of each of the set of low-frequency electromagnetic waves is greater than the volume of the object of interest; a metasurface for receiving the set of low-frequency electromagnetic waves after the set has passed through or around the object of interest and generating an impression signal, wherein the metasurface includes a set of unit cells; and a processor for generating at least one impression of the object of interest based on the impression signal.

Description

[Technical Field]

[0001] This disclosure claims priority from U.S. Provisional Application No. 63,577,998, filed on June 12, 2023, which is incorporated herein by reference.

[0002] This disclosure generally covers imaging techniques, and more particularly, methods and systems for performing imaging using low-frequency electromagnetic fields. [Background technology]

[0003] While many different solutions are used in the field of imaging, these solutions have various problems depending on the application. For example, in the medical field, it is desirable to reduce the harmful exposure patients receive from X-ray imaging due to the adverse effects of X-rays. This problem can be complicated by the fact that some degree of regular imaging may be necessary or beneficial for the early detection of cancer in patients.

[0004] Breast cancer is the second most common cancer diagnosed in women after skin cancer and significantly reduces the quality of life for many women. Current technology faces challenges related to at least one of the following: health-related issues, scanning time, and cost-effectiveness.

[0005] One of the current methods for detecting cancer or tumors is X-ray mammography. This technique is suitable for detecting malignant tissue in low-density breasts, but the ionizing radiation can have harmful effects on the patient. In the case of high-density breasts, the overlap between fatty tissue and malignant tissue is large, making it difficult to diagnose cancerous tumors using this technique. Magnetic resonance imaging (MRI) is also used as a complementary diagnostic tool and offers higher accuracy than X-ray mammography, especially in the case of high-density breasts, but the use of MRI technology is costly and therefore expensive when used for routine screening, especially in low-income areas. Ultrasound is also used to diagnose breast cancer, but the accuracy of detecting tumors depends on the expertise of the radiologist.

[0006] In recent years, microwave imaging (MWI)-based breast cancer detection techniques have been introduced as an alternative to testing or detection. MWI uses non-ionizing electromagnetic (EM) waves instead of potentially dangerous ionizing waves. In addition, low-frequency electromagnetic excitation allows for deeper penetration, thereby improving the ability to diagnose abnormalities embedded deep within dense breast tissue. Furthermore, MWI leverages low-cost system integration.

[0007] Therefore, a novel method and system for performing imaging using a low-frequency electromagnetic field is provided, which overcomes the shortcomings of current systems. [Overview of the project] [Problems that the invention aims to solve]

[0008] This disclosure relates to novel methods and systems for performing imaging using low-frequency electromagnetic fields. [Means for solving the problem]

[0009] One aspect of the present disclosure provides a system for imaging an object of interest, the system comprising: a low-frequency radiation source for transmitting a set of low-frequency electromagnetic waves toward the object of interest, wherein the size of each of the set of low-frequency electromagnetic waves is greater than the volume of the object of interest; a metasurface for receiving the set of low-frequency electromagnetic waves after the set has passed over or around the object of interest and generating an impression signal, wherein the metasurface comprises a set of unit cells; and a processor for generating at least one impression of the object of interest based on the impression signal.

[0010] In another embodiment, the disclosure further includes a signal generator for providing an input to a low-frequency radiation source. In yet another embodiment, the input is a continuous wave signal. In yet another embodiment, the input is a command for generating a set of low-frequency electromagnetic waves.

[0011] In yet another embodiment, the disclosure includes a display for displaying at least one impression of the object of interest. In yet another embodiment, each of a pair of unit cells is smaller than the size of each low-frequency electromagnetic wave. In yet another embodiment, the pair of unit cells are arranged in an array. In yet another embodiment, each of a pair of unit cells includes a reactive portion and a non-reactive portion. In yet another embodiment, the reactive portion includes an outer portion and an inner portion. In yet another embodiment, the reactive portion further includes a pair of vias connected to the outer portion.

[0012] In one embodiment, each of a set of unit cells includes a surface-mount component.

[0013] Another aspect of the present disclosure provides a method for imaging an object of interest, the method comprising: transmitting low-frequency electromagnetic waves to an object of interest, wherein the size of each pair of low-frequency electromagnetic waves is greater than the volume of the object of interest; capturing the low-frequency electromagnetic waves passing through or around the object of interest by a metasurface comprising a pair of unit cells; generating an impression signal based on the captured low-frequency electromagnetic waves; and generating an impression based on the impression signal.

[0014] In another embodiment, each of a set of unit cells is smaller than the size of each low-frequency electromagnetic wave. In yet another embodiment, the step of generating an impression signal includes processing the captured low-frequency electromagnetic wave. In yet another embodiment, the step of transmitting a low-frequency electromagnetic wave includes receiving an input at a low-frequency radiation source, generating a low-frequency electromagnetic wave based on the input, and transmitting the low-frequency electromagnetic wave to an object of interest.

[0015] Some embodiments of this disclosure are shown as examples and are not limited to the drawings in the accompanying drawings, where similar references may indicate similar elements. [Brief explanation of the drawing]

[0016] [Figure 1a] This is a schematic diagram of a system for imaging using low-frequency electromagnetic waves. [Figure 1b] This is a schematic diagram of a mammography system that uses low-frequency electromagnetic fields. [Figure 1c] This is a schematic diagram of another embodiment of a system for imaging pipes using low-frequency electromagnetic waves. [Figure 2a] Figure 1a is a perspective view of the metasurface used in the system. [Figure 2b] These are diagrams with different unit cells. [Figure 2c] These are diagrams with different unit cells. [Figure 2d] These are diagrams with different unit cells. [Figure 3]A table showing parameters related to an embodiment of a unit cell. [Figure 4a] A chart showing |S11| measurement values for different thickness values. [Figure 4b] A chart showing |S11| measurement values for different values of L. [Figure 4c] A chart showing |S11| measurement values when R1 = R2. [Figure 4d] A chart showing the values of |S11| and power of a unit cell. [Figure 5a] A top view of a metasurface. [Figure 5b] A bottom view of a metasurface. [Figure 5c] A schematic diagram showing a scanning technique using a metasurface. [Figure 5d] A schematic diagram of a breast model. [Figure 6a] A simulation model of a healthy breast. [Figure 6b] A simulation model of a breast with a tumor. [Figure 6c] A diagram of the impression of a healthy breast in Fig. 6a using the system of the present disclosure. [Figure 6d] A diagram of the impression of a breast with a tumor in Fig. 6b using the system of the present disclosure. [Figure 6e] A chart showing the position of a test tumor in a breast model. [Figure 7a] A diagram of a breast model showing a 10 mm tumor at different positions. [Figure 7b] A diagram of a breast model showing a 10 mm tumor at different positions. [Figure 7c] A diagram of a breast model showing a 10 mm tumor at different positions. [Figure 7d] A diagram of a breast model showing a 10 mm tumor at different positions. [Figure 8a] A diagram of a breast model showing a 7.5 mm tumor at different positions. [Figure 8b]This is a diagram of a breast model showing 7.5 mm tumors in different locations. [Figure 8c] This is a diagram of a breast model showing 7.5 mm tumors in different locations. [Figure 8d] This is a diagram of a breast model showing 7.5 mm tumors in different locations. [Figure 9a] This is a diagram of a breast model showing 5mm tumors in different locations. [Figure 9b] This is a diagram of a breast model showing 5mm tumors in different locations. [Figure 9c] This is a diagram of a breast model showing 5mm tumors in different locations. [Figure 9d] This is a diagram of a breast model showing 5mm tumors in different locations. [Figure 9e] Figure 9a shows an impression of the breast model. [Figure 9f] Figure 9b is an impression of the breast model. [Figure 9g] Figure 9c is an impression of a breast model. [Figure 9h] Figure 9d is an impression of a breast model. [Figure 10a] This is a perspective view of the simulation setup. [Figure 10b] This is a diagram showing the impression received from the simulation setup in Figure 10a. [Figure 11] These are a pair of schematic diagrams of breast models. [Figure 12] This flowchart outlines a method for imaging a body part for at least one anomaly. [Modes for carrying out the invention]

[0017] This disclosure relates to methods and systems for performing imaging of an object of interest using low-frequency electromagnetic waves or low-frequency electromagnetic fields. In one embodiment, the disclosure includes a transmitter that transmits and / or induces low-frequency electromagnetic waves toward an object of interest, and a metasurface that receives or senses the electromagnetic waves after they have passed through the object of interest and / or the vicinity of the object of interest. The electromagnetic waves are larger than the volume or size of the object of interest. In other embodiments, the size of the unit cells in the metasurface is smaller than the size of the electromagnetic waves. In some embodiments, the low-frequency electromagnetic waves are between approximately 100 MHz and approximately 200 MHz.

[0018] In some embodiments, the disclosure is used, for example, as a mammography apparatus to detect abnormalities in a body part of interest using a low-frequency electromagnetic field, and also as a method of using a mammography apparatus. In some embodiments, the disclosure can be considered as an apparatus for early breast cancer screening or tumor detection.

[0019] When the Disclosure is used as a mammography device, the Disclosure uses the System and Method of the Disclosure to obtain an impression of a body part, such as the breast, correlated with components of the body part. One advantage of the Disclosure is that it reduces or eliminates the patient's exposure to harmful radiation. Another advantage is that, because the Disclosure relies on low-frequency microwaves rather than harmful high-frequency radiation, patients can undergo examinations more frequently.

[0020] In other embodiments, the disclosure may be used to detect cracks or damage in other body parts of interest. In yet another embodiment, the disclosure may be used to detect cracks or damage in pipes, walls, etc. In yet another embodiment, the disclosure may be used to inspect the purity of rubber or plastic materials.

[0021] In one embodiment, the Disclosure uses a metasurface comprising a set of unit cells or electrically miniature resonators joined together to provide a surface having high or strong electromagnetic energy absorption to capture an impression or image of a body part or an area or item such as a set of pipes, but is not limited to this. One of the advantages of the Disclosure when used to image the breast is to provide a safe and inexpensive method and system for the early detection or screening of abnormalities in a body part, such as tumors in the breast of a patient that may lead to breast cancer, but is not limited to this.

[0022] Referring to Figure 1a, a schematic diagram is shown illustrating a first embodiment of a system for imaging using low-frequency electromagnetic waves according to the present disclosure. The system 10 includes a transmitter 12 or transmitting component that transmits low-frequency electromagnetic waves 14, and at least one metasurface 16 that receives the low frequencies transmitted by the transmitter 12 near or after the object of interest 18 has passed through the object of interest 18. In the embodiment, the size of the electromagnetic waves is greater than the volume of the object of interest.

[0023] The transmitter 12 is connected to a signal generating component 20 that provides signals or instructions to the transmitter 12. The signal generating component 20 may receive instructions regarding the frequency level or shape of low frequencies transmitted by the transmitter 12. The metasurface 16 is connected to a central processing unit (CPU) 22 that processes the signals received by the metasurface 16. As can be seen, in the present embodiment, the metasurface 16 is located on the opposite side of the object of interest 18 from the transmitter 12. The metasurface 16 contains a set of unit cells (as described below), each of which is smaller than the size of an electromagnetic wave.

[0024] As shown in Figure 1a, in operation, the transmitter 12 transmits low frequencies to the object of interest 18. Depending on the characteristics of the object of interest 18, such as its transparency or opacity, some of the low-frequency electromagnetic waves may pass through the object of interest 18, while in other test or operating environments, the low-frequency electromagnetic waves 14 may be blocked by the object of interest 18. Other low frequencies 14 may only pass near the object of interest 18. The perceived low-frequency electromagnetic waves, which can be seen as a set of received signals or impression signals, are then passed to the CPU 22, which processes the received signals to generate an image or impression of the object of interest 18. In other embodiments, the set of received signals may be processed before they are sent to the CPU 22.

[0025] Moving to Figure 1b, a side view of another embodiment of an imaging system using low-frequency electromagnetic waves is shown. The present embodiment can be seen as a system for imaging body parts using low-frequency electromagnetic waves, or as a mammography device using low-frequency electromagnetic waves. In some embodiments, the images generated by the system may be used to detect abnormalities in body parts. The environment in which the imaging system 30 may be used includes a platform 32 on which a patient 34 may be placed. The platform 32 includes an opening 36 for receiving a body part 38 or object of interest being examined or imaged by the device or system 30. In this example, the body part is the breast of the patient 34.

[0026] System 30 includes a low-frequency transmitter or radiation source 40 on one side of the aperture 36, which is, but not limited to, an electrically small (ES) dipole antenna acting as a near-field source. System 30 includes at least one metasurface 42 on the opposite side of the aperture 36. In operation, the radiation source 40 transmits low-frequency electromagnetic waves toward the body part 38 and at least one metasurface 42.

[0027] In the current embodiment, the ES antenna is inherently inefficient, and as a result, several percent of the power delivered from the signal generator is radiated to the outside; therefore, the radiated power (transmitted by the transmitter 40) can be increased by selecting a desired ES antenna or by using a high-power signal as an excitation source. In the current embodiment, the radiation source 40 may also include a power amplifier in series with an isolator connected to the ES antenna. The radiated low-frequency electromagnetic waves are directed towards and penetrate a body part 38, such as a woman's breast. In some embodiments, the low-frequency radiation source 40 may be a horn antenna used to irradiate the body part 38 with low-energy microwave radiation across a narrow frequency band.

[0028] In the present embodiment, at least one metasurface 42 may be considered analogous to an X-ray film used in X-ray mammography. The metasurface 42 includes a set of electrically miniature resonators that can be considered as unit cells arranged in an organized array. This will be described in more detail below with reference to Figures 2a to 2d.

[0029] In the present embodiment, the low-frequency radiation source 40 is connected to a signal generator 44. The signal generator 44 receives an input from the user and transmits a signal to the low-frequency radiation source 44 to generate a low-frequency electromagnetic wave based on the input and direct it towards the body part 38 of interest. In one embodiment, the low-frequency radiation source 40 is supplied with a continuous wave (CW) signal by the signal generator 44 at a desired frequency, such as but not limited to about 100 to about 400 MHz. However, in some embodiments, the frequency or wavelength of the electromagnetic wave is selected such that the size of the wavelength is greater than the volume or size of the object of interest. For example, when the present disclosure is used as a mammography device, the frequency of the wave is between about 20 MHz and about 400 MHz such that the wavelength of the wave is greater than the volume of the breast being imaged or impressed.

[0030] In the current embodiment, at least one metasurface 42 is connected to a processing and visualization station 46. The processing and visualization station 46 (which in some embodiments may be a desktop computer or other similar CPU) receives signals from the metasurface 42, processes the received signals, and generates an impression of a body part 38 based on the signals. In some embodiments, the signals are processed before being received by the processing and visualization station 46, which then generates an image or impression based on the processed received signals.

[0031] The signals transmitted by at least one metasurface 42 are low-frequency electromagnetic waves that have passed through the body part of interest 38 and / or around the body part of interest 38 and have been received and / or sensed by at least one metasurface.

[0032] In Figure 1b, the patient is shown lying on platform 32, but in other embodiments, a horizontal platform or surface may be present, so that the patient may be standing and leaning against the horizontal platform, with the body part of interest positioned between the low-frequency radiation source 40 in an opening within the horizontal platform or surface and at least one metasurface 42. The platform may also be positioned at any angle between vertical and horizontal. In yet another embodiment, the opening may be moved within the platform so that different body parts can be screened using a single system 30. In some embodiments, as the opening is moved, the metasurface 42 and the low-frequency radiation source 40 also move with the opening 36.

[0033] In the operation of the embodiment shown in Figure 1b, after the patient 34 is placed on the platform 32 and the patient's body part 38 is placed within the opening 36, the low-frequency radiation source 40 transmits low-frequency electromagnetic waves toward the body part 38 and the metasurface 42, the electromagnetic waves being greater than the volume or size of the object of interest. The low-frequency electromagnetic waves are generated based on a signal or input from a signal generator 44, which receives commands or inputs directly from the individual or remotely from an electronic device (not shown) communicating with the signal generator 44. The metasurface 42 senses or receives low-frequency electromagnetic waves around and / or passing through the body part 38. In one embodiment, the metasurface 42 receives energy (or low-frequency electromagnetic waves) transmitted through the body part in a manner similar to X-ray mammography, but does not receive harmful radiation used by X-ray mammography equipment or apparatus. By placing the metasurface near the body part 38 and the low-frequency radiation source 40, the unit cells of the metasurface 42 become capable of capturing field information transmitted by the transmitted energy.

[0034] After interaction with body parts (low-frequency electromagnetic waves), the power map is absorbed by the metasurface. For testing purposes, the power radiated in each unit cell (which may be considered a pixel) can be recorded using a spectrum analyzer or power meter. To observe real-time changes in the power map, each unit cell may be connected to an individual power meter.

[0035] By generating low frequencies using the low-frequency radiation source 40, the low frequencies can penetrate more deeply into dense muscle and / or breast tissue (if the body part of interest is the breast). The low-frequency electromagnetic waves received by the metasurface 42 are then transferred to the processing and visualization station 46, which processes the received signals to generate impressions and / or images of the body part 38 for display to the user of the processing and visualization station 46. As seen in Figure 1b, the processing and visualization station 46 includes a display 48. In one embodiment, the processing and visualization station 46 processes the signals using AI, such as in the form of a convolutional neural network (CNN), to characterize the body part and any tumors or abnormalities within the body part. Other neural networks are also conceivable. The output of the system may be further processed for visualization. The processing and visualization station 46 may also perform post-processing on the generated impressions.

[0036] In one embodiment of the present disclosure, the present disclosure generates or creates an impression (or image) of a breast including components of the breast, and the impression (or image) can be used to determine whether the breast has an abnormality (benign or cancerous). The system in Figure 1b may be considered an alternative to X-ray-based mammography. In X-ray mammography, the breast is irradiated with an X-ray energy burst, and an impression is collected on the opposite side of the X-ray source via an X-ray-sensitive film that may be exposed to harmful electromagnetic waves.

[0037] In this disclosure, a low-frequency energy burst is generated and directed toward one side of the breast, and a metasurface (an assembly of small printed circuit cells) collects the signal passing through or around the breast to receive an impression signal. In some embodiments, the output from a transmitter, which may be considered a radio frequency energy source, may vary. In operation, the impression signal sensed or collected by the metasurface may be considered as the power incident on each unit cell. The impression signal is then transmitted to a display / computer for visualization or to a computer for processing to generate the displayed image. The resolution of the image or impression depends directly on the size of the unit cells that make up the metasurface.

[0038] Moving on to Figure 1c, a schematic diagram of yet another embodiment of a system for imaging using low-frequency electromagnetic waves is shown. The present embodiment may be considered a system for imaging pipes using low-frequency electromagnetic waves. In some embodiments, the images generated by the system may be used to detect anomalies such as damage or cracks in the pipes.

[0039] In the system 50 of Figure 1c, the system 50 includes a transmitter 52 that transmits low-frequency electromagnetic waves 54 toward an object of interest, such as a pipe 56, which are then sensed or received by a metasurface 58 located on the opposite side of the transmitter 52 relative to the pipe 56. The metasurface 58 includes a set of unit cells 59 that receive signals passing through the pipe 56 and / or around the pipe 56. After receiving the impression signals or electromagnetic waves, the metasurface transmits these readings or signals to a CPU 60, which processes the signals to generate an image or impression of the pipe 56. In the present embodiment, the pipe 56 includes a crack 62 shown in the generated image or impression. The system 50 may further include a signal generator 64 that provides a signal or waveform to the transmitter 52 for transmitting the electromagnetic waves 54.

[0040] Moving to Figure 2a, a perspective view of the metasurface is shown. As seen in Figure 2a, the metasurface 200 includes a set of unit cells 202 arranged within an array of unit cells. In the present embodiment, the metasurface is square, and the unit cells are arranged in a 5x5 array. If the metasurface is square, the array of unit cells may be 3x3, 10x10, or any square arrangement, depending on the intended use of the metasurface, but it is understood that the metasurface may be rectangular (i.e., 5x10) or any other shape (i.e., a circle with the unit cells appropriately shaped). In the present embodiment, the surface of each unit cell is square, but other shapes of surface for unit cells may be assumed. In the embodiment, the size of the unit cell is smaller than the wavelength of the electromagnetic wave. In some embodiments, for a square unit cell, the edge of the unit cell is between approximately 2 mm and approximately 5 mm. As long as the unit cell is smaller than the wavelength of the electromagnetic wave, the unit cell may have any theoretical size, but physical limitations affect the theoretical implementation of the current unit cell design.

[0041] After low-frequency electromagnetic waves pass over or around an object of interest, a set of unit cells 202 receive the low-frequency energy. In one particular embodiment, the metasurface 202 includes a 10 × 10 array of unit cells 202 to provide a metasurface of a size comparable to that of a normal woman's breast, with a radius of approximately 10 cm. In another embodiment, the metasurface 202 may include a predetermined number of unit cells (pixels) to sense the smallest anomalies within a body part of interest.

[0042] Moving from Figure 2b to Figure 2d, perspective, top, and bottom views of a unit cell are shown. Within the metasurface 200, unit cells 202 are arranged in close proximity to each other, creating a dense array, thereby the input impedance of each unit cell 202 may be modified or affected by adjacent unit cells in the array. The unit cells 202 may be designed using various topologies using known techniques, but the unit cells of this disclosure include an electric-inductive-capacitive (ELC) resonator that provides high sensitivity to the incident electric field. Components within each unit cell 202 include capacitors and inductors realized by gaps and conductive ring patterns. In some embodiments, the components are integrated within the unit cell, and in other embodiments, the components are surface-mounted on the unit cell. One of the design features of the metasurface of this disclosure is that the low loss of the unit cells maximizes or increases the energy absorption at its termination in the metasurface 200.

[0043] In operation, the unit cell 202 of the metasurface 200 acts as an ES antenna. When the breast is the body part to be examined, impressed, or imaged, changes in dielectric constant and conductivity between healthy breast tissue and cancerous breast tissue can affect the electromagnetic energy (or waves) propagating through the breast, and more importantly, the energy or waves scattered from the breast tissue are received by the metasurface, and thus the energy received by the metasurface is affected by the presence of a tumor in the breast. The received electromagnetic energy or waves are then processed (by a processing station 22, for example) to form an image (impression), which may be processed or examined to reveal or determine the presence or absence of abnormalities in the breast.

[0044] Furthermore, when an incident electromagnetic field strikes the tissue of a body part, the field excites all molecules, and secondary scattering occurs from these molecules. This secondary scattering depends on the permittivity (related to the polarization of the molecules) and the permeability (related to the magnetization of the molecules). Therefore, each molecule or cluster of molecules reacts to the striking electromagnetic field depending on the constitutive permeability and permittivity parameters of the cluster, and thus the resulting impression of the body part can indicate the presence or absence of at least one anomaly.

[0045] As shown in Figures 2b to 2d, a unit cell 202, which can be considered a miniaturized ELC resonator, includes a top surface 204 that receives electromagnetic waves or energy generated as a result of low-frequency radiation directed towards a body part of interest. The surface 204 includes a reactive portion 206 for receiving waves, along with a non-reactive portion 208. In one embodiment, the reactive portion 20 includes a pair of inductors and resistors for receiving energy. In one embodiment, the reactive and non-reactive portions are etched onto a printed circuit board.

[0046] The non-reactive portion 208 includes an outer ring 260, a central portion 261, and a pair of intermediate portions 262. The outer ring 260 is connected to the pair of intermediate portions 262 via a first pair of interconnectors 264, and the pair of intermediate portions 262 are connected to the central portion 261 via a second pair of interconnectors 266. The pairs of interconnectors 264 and 266 may be considered gaps separating the reactive portion 206. The reactive portion 206 includes a first section 206a and a second section 206b. Each reactive portion 206a and 206b includes an outer portion 268 and an inner portion 270, which are connected by a reactive interconnector 272.

[0047] In the present embodiment, the width of the outer ring 260 is denoted as S1, the width of each outer portion 268 is W1, the width of each inner portion 270 is W2, the width of each of the first pair of interconnectors 264 is G2, the width of each of the second pair of interconnectors 266 is G1, and the width of each intermediate portion 262 is S2. The unit cell 202 further includes a pair of vias 274 connected to each of the outer portions 268. As shown in Figure 2d, the diameter of one via is denoted as D1 and the diameter of the other via is denoted as D2.

[0048] To maintain the x- and y-direction symmetry of the unit cell, a second pair of interconnectors 264 or gaps are placed between the two outer portions 268 to achieve symmetry between the two outer portions. The inductor and resistor values ​​of the two different reactive portions 206a and 206b are selected to be the same. In addition, by including two vias 274, the unit cell 202 is made able to maintain a certain degree of symmetry with respect to collisional electromagnetic fields or received low-frequency electromagnetic waves. To minimize or reduce losses, the relative permittivity is ε r A low-loss Rogers substrate (TMM10i) with a loss tangent of 9.8 and tan(δ)=0.002 was used. In other words, it is necessary to reduce or minimize the energy wasted in the metasurface substrate itself and maximize or increase the energy absorbed by the sensor (located on the back of the metasurface).

[0049] In one embodiment, the system may operate at a frequency of approximately 200 MHz, which requires miniaturization of each unit cell 202 so that the metasurface 200 can achieve high-resolution impressions. To address this, the equivalent capacitance and / or inductance of each unit cell is increased, thereby allowing the frequency to be reduced according to equation (1).

number

[0050] For the miniaturization of electrically smaller resonators or unit cells, the resonant frequency of each unit cell can be tuned to optimize or obtain the desired S-parameters for maximum or improved absorption by manipulating the resonant frequencies of concentrated elements such as inductors, capacitors, and resistors, but not limited to these.

[0051] Moving to Figure 12, a flowchart outlines a method for imaging a subject of interest for at least one anomaly using low-frequency electromagnetic waves. First, the subject of interest being screened is placed between a transmitter, such as a low-frequency radiation source, and a metasurface (1200). Then, low-frequency electromagnetic waves are transmitted towards the subject of interest (1202). In one embodiment, the low-frequency electromagnetic waves are transmitted via a low-frequency radiation source via an input such as a CW wave from a signal generator. Alternatively, the low-frequency radiation source may receive a signal or command from an external communication device and generate low-frequency electromagnetic waves based on the command signal.

[0052] The metasurface then receives transmitted low-frequency electromagnetic waves that have passed through the object of interest and / or around the object of interest (1204). These received signals may be considered impression signals or measurements. The impression signals are then transmitted to a processor (1206). In one embodiment, the impression signals are transmitted to a processing station 22.

[0053] Next, an impression or image is generated based on the impression signal (1208). If necessary or desirable, the impression and / or impression signal may be further processed (considered post-processing) to generate or determine other information or data from the impression signal (1210).

[0054] In one particular manner, when this disclosure is used for mammography, it is assumed that the upper and lower sides of the breast being examined or imaged are compressed and flattened. Therefore, while there is no problem in adjusting the breast position in the Z coordinate or Z direction, it is important that the left and right breasts are symmetrically positioned with respect to the corresponding coordinate system reference in the X coordinate or X direction and the Y coordinate or Y direction. By doing so, the system can remove or reduce undesirable background images from the acquired impression by applying post-processing techniques.

[0055] In the experiment, individual unit cells were modeled using electromagnetic field simulation software. Since the unit cells were intended to be arranged in a structure that infinitely self-repeats in both the x and y directions, perfect or desired magnetic conductor (PMC) boundary conditions were set in the x direction and perfect or desired electric conductor (PEC) boundary conditions were set in the y direction to model the periodicity of the unit cells. The performance of the unit cells was then tested by irradiating them and recording the |S11| (reflection coefficient), which represents how much power is reflected or received by the unit cell.

[0056] In one embodiment, the parameters of the unit cell may be designed or selected based on two factors: a minimum or low |S11| and a maximum or high Q coefficient. Examples of calculated parameters for various unit cells are given in the table in Figure 3. The parameters in Figure 3 correspond to the symbols in Figures 2b to 2d. In a particular embodiment based on the parameters in the table in Figure 3, the unit cell has an area of ​​10.5 mm × 10.5 mm and a thickness of 4.0 cm, allowing for an increase in inductance due to the length of the vias 274. The graphs in Figures 4a to 4d show the results of experiments performed using the unit cell with the parameters listed in the table in Figure 3, where three control parameters were investigated. These control parameters were the substrate thickness t, the inductance values ​​L1=L2=L3=L4=L, and the termination resistance values ​​R1=R2.

[0057] Figure 4a shows |S11| on the y axis and frequency on the x axis when t is varied, Figure 4b shows |S11| on the y axis and frequency on the x axis when L is varied, and Figure 4c shows |S11| on the y axis and frequency on the x axis when R1=R2. The non-variable parameters are set to L=100nH, R1=R2=470Ω, and t=40mm. Figure 4d shows |S11| and power delivered to the termination resistance of a unit cell, with an incident power of 0.5 watts.

[0058] Figure 4a shows that as vias add inductance to a unit cell, the longer the via (i.e., the higher t), the lower the resonant frequency. Figure 4b shows that the resonant frequency can be adjusted by changing the inductance of the concentrated inductor. Figure 4c shows that the smallest or lowest |S11| occurs at the resonant frequency of the unit cell for a value of R1,2 = 470Ω, which indicates perfect impedance matching between free space and the cell.

[0059] Figures 4a to 4c also show that impedance matching is affected by the via length (t), the inductance L of the inductor, and the terminating resistors R1=R2, respectively. When t=40mm, L=100nH, and R1=R2=470Ω, |S11| has a value of less than -30dB at 200MHz, corresponding to very strong impedance matching, and the Q coefficient is 16.

[0060] Figure 4d shows the response of a unit cell using the parameters listed in the table in Figure 3. It can be seen that of the 0.5 watts of incident power, 0.46 watts (92%) is delivered to the terminating resistors (at the end of each via) (0.23 watts at each resistor), and 0.04 watts (8%) is lost due to dielectric and ohmic losses.

[0061] Moving on to Figures 5a and 5b, top and bottom views of another embodiment of the metasurface are provided. In the present embodiment, the metasurface is a 10 × 10 array of unit cells, such as the one described above, with each unit cell containing two termination resistors. As outlined above, the metasurface can contain any number of unit cells in any configuration, but the metasurfaces in Figures 5a and 5b were created to perform the tests of this disclosure. As seen in Figure 5b, each unit cell is electrically connected to each of the other unit cells, thereby affecting the reading of signals received by adjacent unit cells.

[0062] As instructed above, each unit cell may be considered to represent a pixel, and its value is assigned by measuring the power dissipation at the corresponding terminating resistor. Due to the symmetry in the unit cell as described above with respect to Figures 2b to 2d, the received power is evenly distributed between the resistors. It is understood that asymmetric unit cells may also be assumed. By measuring the power dissipated at one of the two terminating resistors of each unit cell, a two-dimensional power map (representing the received energy) can be generated by a processing station 26, etc. This two-dimensional power map may be considered an impression image of the body part of interest. In other words, the position (x) of each unit celln ,y n ) and its terminal power dissipation are used to construct an impression image that reflects the power absorbed by each unit cell (pixel).

[0063] In experiments using a 10x10 array of metasurfaces, this embodiment was used to generate or record 30x30 impressions, resulting in a larger impression compared to the number of unit cells used. Considering that the length of a unit cell is Δx, impressions were recorded by shifting the entire metasurface in both the x and y directions by values ​​of Δx / 3 and 2Δx / 3, in addition to the reference position. In this way, nine different combinations of metasurface positions provided nine pixels for each unit cell. Therefore, using the entire array on the same metasurface, impressions with 900 pixels were created instead of 100. An example of unit cell subdivision is schematically shown in Figure 5c.

[0064] In near-field fields, resolution can far exceed the Abbe diffraction limit. Therefore, when a low-frequency radiation source is very close to a body part of interest, such as a breast, the electromagnetic field generated by the source impacting the breast contains all polarizations. Thus, under such excitation conditions, the interaction between the impacting electromagnetic field and the breast provides a scattering or secondary field with higher information content.

[0065] By recalling the spring and mass models of molecules interacting with electromagnetic waves, molecular polarization occurs due to the formation of dipole moments within the breast (or a breast model for experimental purposes). Depending on the polarization of the incident field, molecules within the breast are affected differently. Thus, the generation of different polarizations by low-frequency radiation sources excites molecules in healthy and cancerous tissue, and therefore generates independent information leading to unique impressions that can be produced by the metasurface. As described above, an electrically small dipole with a length of 2 / 10 and a diameter of 2 / 1000, placed very close to the breast, can be used as a radiation source (and has been used in some experiments).

[0066] In experiments using numerical simulations, various types of breast models were considered to test and cover the diversity of human female breasts. Typically, human breasts are composed primarily of fibrous tissue and adipose tissue. The density of breast models can be classified based on the density of fibrous tissue. Figure 5d shows a breast model used by electromagnetic field simulation software, and the breast model includes skin, adipose tissue, fibrous tissue, and tumor. Four different classifications of breast models were considered: (1) very dense breasts (fibrous tissue over 75%), (2) heterogeneously dense breasts (fibrous tissue between 50% and 75%), (3) areas with scattered fibrous tissue (fibrous tissue between 25% and 50%), and (4) entirely fatty breasts (fibrous tissue less than 25%).

[0067] For the purpose of testing and validating this disclosure, the breast is assumed to be a hemisphere with a radius of 50 mm, covered by a 2 mm thick skin layer, and its internal structure is assumed to consist of fibrous tissue and adipose tissue. At an operating frequency of 200 MHz, the relative permittivity and electrical conductivity of the fibrous tissue are close to 64 S / m and 0.8 S / m, respectively, while for the adipose tissue, these measurements are close to 5.6 S / m and 0.03 S / m, respectively. The central Ct of the spherical tumor, modeled as a perfect conductor (PEC), is (x) relative to the origin of the Cartesian coordinate system shown in Figure 5b. t ,y t ,z t It was placed in [location]. This breast model was selected because it provides contrast between tumor and healthy tissue.

[0068] Figures 6a and 6b provide simulation models of a healthy breast (Figure 6a) and a breast with a 10 mm tumor in the upper left corner (Figure 6b). The table in Figure 6e lists the different tumor locations used to test this disclosure. Figures 6c and 6d are impressions of Figures 6a and 6b generated by this disclosure. Thus, Figures 6a through 6d are C of the breast model. tiShows the results from tumors at the location. As shown from FIG. 6a to FIG. 6b, it can be seen that the difference between the two impressions is negligible to the naked eye. To increase the resolution and as a result, increase the possibility of distinguishing within the impression between the breast with a tumor and the breast without a tumor, as shown in FIGS. 6c and 6d, each impression of the breast with a tumor is subtracted from the impression of the same breast but without a tumor. In other words, in this embodiment, images of both the left and right breasts are acquired, and then one image is subtracted from the other to obtain an impression that emphasizes the tumor (if present).

[0069] Experiments were further carried out by adding or placing tumor samples at different positions and with different dimensions. First, spherical tumor samples made of PEC with a radius of 10 mm were placed at four different positions (as shown in the simulation models of FIGS. 7a to 7d), namely the upper left corner (Ct1), upper right corner (Ct2), lower left corner (Ct3), and lower right corner (Ct4) of the breast. These positions were selected to show the quality of the impression and their ability to detect the position of the tumor, and also to better observe the subtle differences between different impressions.

[0070] Although other calculation techniques are also envisioned, the effectiveness of the subtraction technique is based on the assumption that the left and right breasts are identical for the majority of patients. Statistically, the degree of asymmetry of the relative breast volume (BV: breast volume) between the two breasts has a median of 2.71%, and the degree of asymmetry of the relative dense volume (DV: dense volume) has a median of 3.28%.

[0071] The simulation results for four different positions of tumors with a radius of 7.5 mm were analyzed. The tumors are at four positions C t1 、C t2 、C t3 、and C t4It was placed in one of the locations. Figures 8e to 8h show the impressions of the tumor-containing breast model described above after applying the subtraction technique to the impression of a healthy breast. The most significant difference was observed closer to the location of the tumor.

[0072] Simulations using the apparatus of this disclosure were also performed for four different locations of tumors with a radius of 5 mm. The tumors were placed in the same locations (see the simulation models in Figures 9a to 9d). Figures 9e to 9h show impressions of the breast models with the corresponding tumors after applying subtraction.

[0073] In further experiments to test this disclosure, a case study was conducted on a realistic numerical phantom model. The model used was an ACR class 2-scattered fibroglandular breast phantom, whose components were converted from MRI sagittal sections to electromagnetic field simulation software. The model included different fibroglandular voxel configurations, each representing specific electromagnetic properties. The numerical phantom was theoretically effective at operating frequencies from 0 GHz to 20 GHz. As shown in Figures 10a and 10b, the method and system of this disclosure allowed for the acquisition of desired contrast (above DV asymmetry) within the obtained impression, regardless of the breast model under investigation. As shown in Figure 10b, the observed contrast was approximately 14%, which is above the minimum DV asymmetry of 3.28%.

[0074] As explained above, this disclosure is intended to detect the location and size (not the shape or number) of possible tumors, so simulations were performed for spherical tumors and at different radii. The 12 breast models used in the dataset differed in the fat content of the breast models, ranging from very dense breasts (breast model 1) to entirely fatty breasts (breast model 12). Fatty tissue was added to the models as experiments were performed between breast model 1 and breast model 12 to make it. Figure 11 provides schematic diagrams of breast model 1 and breast model 12.

[0075] In other embodiments, the disclosure may be used to generate an impression of any configuration of an abnormality having any shape. Furthermore, the disclosure is effective for any breast shape having a variety of fibrous and adipose tissue, insofar as minimal contrast (DV asymmetry) is provided between the abnormal and healthy components.

[0076] While various embodiments have been described above, it should be understood that these are presented only as examples and illustrations of the present disclosure and are not limiting. It will be apparent to those skilled in the art that various modifications can be made to the form and details without departing from the spirit and scope of the present disclosure. Therefore, the breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined solely in accordance with the appended claims and their equivalents. It should also be understood that each feature of each embodiment described herein and each reference cited herein may be used in combination with any other feature of embodiments. All patents and publications described herein are incorporated herein by reference in their entirety.

Claims

1. A system for imaging objects of interest, A low-frequency radiation source for transmitting a set of low-frequency electromagnetic waves toward the object of interest, wherein the size of each of the set of low-frequency electromagnetic waves is larger than the volume of the object of interest, A metasurface for receiving the set of low-frequency electromagnetic waves after they have passed over or around the object of interest and generating an impression signal, wherein the metasurface includes a set of unit cells, A processor for generating at least one impression of the object of interest based on the impression signal. A system that includes this.

2. The system according to claim 1, further comprising a signal generator for providing input to the low-frequency radiation source.

3. The system according to claim 2, wherein the input is a continuous wave signal.

4. The system according to claim 2, wherein the input is a command for generating the set of low-frequency electromagnetic waves.

5. The system according to claim 1, further comprising a display for displaying the at least one impression of the object of interest.

6. The system according to claim 1, wherein each of the set of unit cells is smaller than the size of each of the low-frequency electromagnetic waves.

7. The system according to claim 1, wherein the set of unit cells is arranged within the array.

8. Each of the aforementioned set of unit cells is The reactive part, non-reactive part and The system according to claim 7, including the system described in claim 7.

9. The reactive portion The outer part, inner part and The system according to claim 8, including the above.

10. The reactive portion The system according to claim 9, comprising a set of vias connected to the outer portion.

11. Each of the aforementioned set of unit cells is The system according to claim 1, comprising a surface mount component.

12. A method for visualizing an object of interest, A step of transmitting low-frequency electromagnetic waves to an object of interest, wherein the size of each of the set of low-frequency electromagnetic waves is greater than the volume of the object of interest. The steps include capturing the low-frequency electromagnetic waves passing through the object of interest or the vicinity of the object of interest by a metasurface comprising a set of unit cells, The steps include generating an impression signal based on the captured low-frequency electromagnetic wave, A step of generating an impression based on the aforementioned impression signal. Methods that include...

13. The method according to claim 12, wherein each of the set of unit cells is smaller than the size of each of the low-frequency electromagnetic waves.

14. The step of generating an impression signal is The method according to claim 12, comprising processing the captured low-frequency electromagnetic waves.

15. The step of transmitting low-frequency electromagnetic waves is Receiving input at a low-frequency radiation source, To generate the low-frequency electromagnetic wave based on the input, and Transmitting the aforementioned low-frequency electromagnetic waves to the object of interest. The method according to claim 12, including the method described in claim 12.

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