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US-12616380-B2 - Electromagnetic tomography and tomographic angiography

US12616380B2US 12616380 B2US12616380 B2US 12616380B2US-12616380-B2

Abstract

A method for tomographic imaging a dielectric object includes irradiating an object with electromagnetic radiation during a first time interval, receiving electromagnetic radiation passed through dielectric object to generate a first dataset at a plurality of spatial locations, irradiating the object with electromagnetic radiation during a second time interval, receiving electromagnetic radiation passed through dielectric object to generate a second dataset at a plurality of spatial locations, generating a third dataset, wherein the third dataset is determined as a function of the first dataset, the second dataset, and a normalized difference between the first dataset and the second dataset, and reconstructing a dielectric image of the object based on the third dataset.

Inventors

  • Serguei Semenov

Assignees

  • Serguei Semenov

Dates

Publication Date
20260505
Application Date
20230426

Claims (14)

  1. 1 . A system for tomographic imaging of a dielectric object, comprising: an electromagnetic measurement system configured to acquire electromagnetic (EM) signals and digitize the EM signals, a cardiac activity recording system configured to acquire Electrocardiogram (ECG) signals and digitize the acquired ECG signals, and a computer system with a processor configured to synchronize the EM signals and the ECG signals, reconstruct images or movies of dielectric properties of the object or reconstruct images or movies of angio-dielectric properties of the object, process the reconstructed images or movies of the dielectric properties or the angio-dielectric properties, assess hypoxia and viability of biological tissues based on the post-processed images or movies, and for images for ε(r) d updated of dielectric properties or movies ε(r, time) d updated of dielectric properties, the processor is further configured to: establish parameters and geometric configuration of the EM measurement system including at least one of frequencies of the EM measurement system used, data acquisition time per acquisition frame, number of frames acquired, dielectric properties of media surrounding the object within an imaging domain, number and position of transmitting and receiving antennas of the EM measurement system, and number and position of receiving antennas of the EM measurement system, synchronize measurements of the EM signals and measurements of the ECG signals, employ raw data acquired from the EM measurement system to form a matrix EM fields from N transmitting antennas of the EM measurement system measured by M receivers of the EM measurement system according to (M*N matrix)−Sij EXP , i=1,N; j=1,M calibrate the M*N matrix based on calibrated Sij EXP experimental data, iteratively reconstruct an image by using an initial homogeneous distribution of dielectric properties ε 1 (r)=ε 0 within an imaging/study domain at the first iteration wherein ε 0 is a known homogeneous dielectric property of a media surrounding the object of the study or another known initial distribution of dielectric properties ε 1 (r) within the imaging/study domain, calculate EM field distribution from N (i=1,N) transmitters within the study domain E i (ε k (r)) on M (j=1,M) receivers Sij THR at k th iteration (k=1,K), calculate of alteration Δ(ε(r)) using gradient or/and Newton type of methods in form of: a) for gradient Δ(ε(r))˜Σ i,j N,M (E i *(ε k (r))×ε j *(ε k (r))×(Sij THR −Sij EXP ) b) for Newton Δ(ε(r))˜inversion of the matrix Dij=(E i *(ε k (r))×E j (ε k (r)), update the distribution of dielectric properties within the study domain at iteration k as ε(r) updated =ε k-1 (r)+Δ(ε(r)), determine if ε(r) updated satisfies a decision making criteria, and in response to determining the decision making criteria is satisfied, output reconstructed image ε(r) updated and further process the image and store reconstructed image in a memory of the computer system, in response to determining the criteria is not satisfied, take the reconstructed image ε(r) updated to a next iteration cycle, wherein the criteria is based on the satisfaction of the following inequation at iteration k: Σ i,j N,M |(Sij THR_iter=k −Sij EXP )|β*Σ i,j N,M |(Sij THR_iter=1 −Sij EXP )|, where |A| is a norm of complex A and β is a convergence accuracy parameter, provide multiple reconstructed images over time, provide input and control parameters and calculation flow control, and store electromagnetic measurements data, and cardiac activity data and the reconstructed images ε(r) updated in a memory of the computer system.
  2. 2 . The system of claim 1 , wherein the object comprises a biological object with vasculature.
  3. 3 . The system of claim 1 , wherein the processor is further configured to generate synchronization signals corresponding to different phases of a subject's cardiac activity.
  4. 4 . The system of claim 1 , wherein the processor is further configured to: use one or more radiation cycles required to compile matrices of raw tomographic data corresponding to two or more dielectric states of the object having different dielectric properties of a portion of the object, compile a first matrix of raw data, and compile a second matrix of raw data.
  5. 5 . The system of claim 4 , wherein the object is a blood vessel or lumen.
  6. 6 . The system of claim 4 , wherein the two or more dielectric states correspond to different flow volume of the fluid through said blood vessel or lumen.
  7. 7 . A system for tomographic imaging of a dielectric object, comprising: an electromagnetic measurement system configured to acquire electromagnetic (EM) signals and digitize the EM signals, a cardiac activity recording system configured to acquire Electrocardiogram (ECG) signals and digitize the acquired ECG signals, and a computer system with a processor configured to synchronize the EM signals and the ECG signals, reconstruct images or movies of dielectric properties of the object or reconstruct images or movies of angio-dielectric properties of the object, process the reconstructed images or movies of the dielectric properties or the angio-dielectric properties, assess hypoxia and viability of biological tissues based on the post-processed images or movies, and for images ε(r) ad updated or movies ε(r, time) ad updated of angio-dielectric properties, the processor is further configured to: establish parameters and geometric configuration of the EM measurement system, including at least one of frequencies of the EM measurement system used, data acquisition time per acquisition frame, number of frames acquired, dielectric properties of media surrounding the object under the study within an imaging domain, number and position of transmitting antennas of the EM measurement system, and number and position of receiving antennas of the EM measurement system synchronize measurements of the EM signals and measurements of the ECG signals, choose a first and second phase of interest from a cardiac activity cycle, use raw data acquired from electromagnetic measurements system during the first phase, form a matrix of complex EM fields from N transceivers measured on M receivers according to (M*N matrix)−Sij EXP-1 , i=1,N; j=1,M; calibrate and form M*N matrix of calibrated Sij EXP-1 based on first measurement phase data, use raw data acquired from electromagnetic measurements system during the second phase, form a matrix of complex EM fields from N transceivers measured on M receivers according to (M*N matrix)−Sij EXP-2 , i=1,N; j=1,M; calibrate and form M*N matrix of calibrated Sij EXP-2 based on second measurement phase data, calculate perturbated M*N matrix of Sij EXP 1/2 =Sij EXP-1 +α(Sij EXP-1 −Sij EXP-2 )/|Sij EXP-1 |, wherein |Sij EXP-1 | is a norm of complex Sij EXP-1 and α—is a parameter chosen by a trial method, iteratively reconstruct an image by using an initial distribution of dielectric properties ε 1 (r) at first iteration, wherein ε 1 (r)=ε 0 , where ε 0 is known dielectric properties of outside of an object under the study and within the imaging domain, calculate EM field distribution from N (i=1,N) transceivers within the study domain E i (ε k (r)) and on M (j=1,M) receivers Sij THR at k th iteration (k=1,K), calculate of alteration Δ(ε(r)) using gradient or/and Newton type of methods in form of: a) for gradient Δ(ε(r))˜Σ i,j N,M (E i *(ε k (r))×E j *(ε k (r))×(Sij THR −Sij EXP 1/2 ) b) for Newton Δ(ε(r))˜inversion of the matrix Dij=(E i *(ε k (r))×E j (ε k (r)); update a distribution of dielectric properties within the study domain at iteration kas ε(r) updated =ε k-1 (r)+Δ(ε(r)), determine if ε(r) updated satisfies a decision making criteria, in response to determining the decision criteria is satisfied displaying the reconstructed angio-dielectric image ε(r) updated and further process the image and store the image in a memory of the computer system, in response to determining the decision criteria is not satisfied, take the reconstructed angio-dielectric image ε(r) updated to the next iteration cycle, wherein the criteria is based on the satisfaction of the following inequation at iteration k: Σ i,j N,M |(Sij THR_iter=k −Sij EXP 1/2 )|<β*Σ i,j N,M |(Sij THR_iter=1 −Sij EXP 1/2 )|, where |A| denotes a norm of complex A and β is a convergence accuracy parameter; provide multiple reconstructed images over time, provide input and control parameters and calculation flow control, and store electromagnetic measurements data, cardiac activity data and reconstructed angio-dielectric images ε(r) updated in a memory of the computer system.
  8. 8 . The system of claim 7 , wherein for images ε(r) ad updated or movies ε(r, time) ad updated of angio-dielectric properties, the processor is further configured to calculate a perturbated M*N matrix in the form of Sij EXP1/2 =Sij EXP-2 +β(Sij EXP-2 −Sij EXP-1 )/|Sij EXP-2 |, where |Sij EXP-2 | is a norm of complex Sij EXP-2 and β—is a parameter chosen by a trial method OR in another forms of linear combination of Sij EXP-1 , Sij EXP-2 , |Sij EXP-1 |, |Sij EXP-2 |, and weighting parameter α.
  9. 9 . The system of claim 7 , wherein for images ε(r) ad updated or movies ε(r, time) ad updated of angio-dielectric properties, the processor is further configured to calculate a perturbated M*N matrix in case when more than two datasets used (for example, K datasets), is calculated as a linear combination of all or portions of K elements Sij EXP-m their norms |Sij EXP-n | and weighting parameters α n (m=1,K; n=1,K−1).
  10. 10 . The system of claim 7 , wherein the object comprises a biological object with vasculature.
  11. 11 . The system of claim 7 , wherein the processor is further configured to generate synchronization signals corresponding to different phases of a subject's cardiac activity.
  12. 12 . The system of claim 7 , wherein the processor is further configured to: use one or more radiation cycles required to compile matrices of raw tomographic data corresponding to two or more dielectric states of the object having different dielectric properties of a portion of the object, compile a first matrix of raw data, and compile a second matrix of raw data.
  13. 13 . The system of claim 12 , wherein the object is a blood vessel or lumen.
  14. 14 . The system of claim 12 , wherein the two or more dielectric states correspond to different flow volume of the fluid through said blood vessel or lumen.

Description

RELATED APPLICATIONS The present application claims priority to a provisional application entitled Electromagnetic Tomography and Tomographic Angiography having application No. 63/473,061 filed on Apr. 27, 2022, which is incorporated by reference herein in its entirety. TECHNICAL FIELD The following relates to systems and methods for electromagnetic tomographic imaging of dielectric objects, including biological objects and their functional components, such as electromagnetic tomographic angiography of blood vessels of biological objects. BACKGROUND The present disclosure relates generally to tomographic imaging systems and angiography systems (both semi-static and movable), individually wearable systems, and related image reconstruction methods. Electromagnetic tomography is a medical imaging technique which utilizes an electromagnetic radiation from non-ionizing portion of the electromagnetic spectrum (for example, in a frequency range of about 0.01 GHz to about 10 GHz) for interrogation of an object under study. In this portion of electromagnetic spectrum, tissues can be imaged based on their dielectric properties. For example, radiation in this frequency range can be employed to reconstruct a three-dimensional (3D) tomographic image of a biological object as, e.g., a 3D distribution of the dielectric properties of that object (e.g., a particular tissue portion). Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Such imaging is traditionally done by injecting a radio-opaque contrast agent into the blood vessel and imaging using X-ray based techniques such as fluoroscopy. Standard-of-Care methods of angiography, such as X-Ray or CT- or MRI-angiography methods, are bulky, expensive and energy in-efficient. X-Ray and CT-angiography methods can be potentially hazardous as such techniques require the use of ionizing radiation. Above mentioned standard-of-care methods of angiography are unable to provide on-line, safe, cost and energy efficient assessment of both tissue viability and status of vessels especially in mobile or wearable settings. This data might be of critical importance for example, during medical emergencies, at high-load physical conditions (athletes, pilots, etc.), at nursing homes, during anesthesia, surgery or childbirth, to name a few. Therefore, there is a need for a technology that is capable of addressing such issues of critical importance. Electromagnetic tomography is applicable to functional imaging of biological objects in mobile and even wearable settings but suffers from a limited spatial resolution because of relatively large wavelength of radiation as compared to sizes of biological targets of particular interest, such as, for example blood vessels. For example, a wavelength of electromagnetic radiation at a typical frequency of 1 GHz, used for cerebral imaging is about 4.7 cm within a brain tissue, which is significantly larger than the dimensions of cerebral vessels. SUMMARY According to one or more aspects, the present disclosure relates to systems and methods for electromagnetic tomography (EMT) including electromagnetic tomographic Angiography (EMTA). In various embodiments, such systems and methods allow for i) EMT of any non-metal-covered dielectric objects, including but not limited to a) imaging of biological objects or parts of biological objects, such as human head or human torso or human extremity; b) imaging of crude oil in oil pipes or an assessment of a composition of oil-water-salt suspensions in desalters of oil refineries or an assessment of oil-refined products in refinery columns; ii) cerebral, cardiac and musculoskeletal EMT Angiography and iii) non-invasive assessment of tissue hypoxia and viability status of biological tissues, including but not limited to brain tissue, cardiac tissue and musculoskeletal tissue. In one aspect, the present disclosure is directed to systems and methods for electromagnetic tomography including its applications in electromagnetic tomographic angiography as discussed in more detail below. In some embodiments, such methods and systems for performing electromagnetic tomography and electromagnetic tomographic angiography can include: i) computational means, comprising at least the following; processor, memory storage, RAM, I/O interface and network adapter; ii) analog-to-digital converter (ADC) for digitizing acquired EM signals from electromagnetic (for example, but not limited to, RF or MW) measurement systems; iii) cardiac activity recording system, for example, but not limited to, ECG recording system with ADC for digitizing acquired ECG signals (typically in biomedical applications); iv) synchronization means for synchronization of acquisition of EM signals and cardiac activity signals, for example ECG signals (typically in biomedical applications); v) processing m