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Meaney P, Geimer S, Golnabi A, Paulsen K. Impact of Skin on Microwave Tomography in the Lossy Coupling Medium. SENSORS (BASEL, SWITZERLAND) 2022; 22:7353. [PMID: 36236453 PMCID: PMC9572048 DOI: 10.3390/s22197353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/20/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
In microwave imaging, the effects of skin on recovering property distributions of tissue underneath the surface may be significant because it has high dielectric contrast with subcutaneous fat, which inevitably causes significant signal reflections. While the thickness of skin, especially relative to the wavelengths in use, would presumably have minor effects, it can introduce practical difficulties, for instance, in reflection-based imaging techniques, where the impact of the skin is large-often as high as two orders of magnitude greater than that of signals from underlying tumors in the breast imaging setting. However, in tomography cases utilizing transmission-based measurement data and lossy coupling materials, the situation is considerably different. Accurately implementing a skin layer for numerical modeling purposes is challenging because of the need to discretize the size and shape of the skin without increasing computational overhead substantially. In this paper, we assess the effects of the skin on field solutions in a realistic 3D model of a human breast. We demonstrate that the small changes in transmission field values introduced by including the skin cause minor differences in reconstructed images.
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Affiliation(s)
- Paul Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA
| | - Shireen Geimer
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA
| | | | - Keith Paulsen
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA
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2
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Alqahtani A, Islam MT, Talukder MS, Samsuzzaman M, Bakouri M, Mansouri S, Almoneef T, Dokos S, Alharbi Y. Slotted Monopole Patch Antenna for Microwave-Based Head Imaging Applications. SENSORS (BASEL, SWITZERLAND) 2022; 22:7235. [PMID: 36236334 PMCID: PMC9573509 DOI: 10.3390/s22197235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 09/19/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
A modified monopole patch antenna for microwave-based hemorrhagic or ischemic stroke recognition is presented in this article. The designed antenna is fabricated on a cost-effective FR-4 lossy material with a 0.02 loss tangent and 4.4 dielectric constant. Its overall dimensions are 0.32 λ × 0.28 λ × 0.007 λ, where λ is the lower bandwidth 1.3 GHz frequency wavelength. An inset feeding approach is utilized to feed the antenna to reduce the input impedance (z = voltage/current). A total bandwidth (below -10 dB) of 2.4 GHz (1.3-3.7 GHz) is achieved with an effective peak gain of over 6 dBi and an efficiency of over 90%. A time-domain analysis confirms that the antenna produces minimal signal distortion. Simulated and experimental findings share a lot of similarities. Brain tissue is penetrated by the antenna to a satisfactory degree, while still exhibiting a safe specific absorption rate (SAR). The maximum SAR value measured for the head model is constrained to be equal to or below 0.1409 W/kg over the entire usable frequency band. Evaluation of theoretical and experimental evidence indicates the intended antenna is appropriate for Microwave Imaging (MWI) applications.
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Affiliation(s)
- Abdulrahman Alqahtani
- Department of Medical Equipment Technology, College of Applied, Medical Science, Majmaah University, Majmaah City 11952, Saudi Arabia
- Department of Biomedical Technology, College of Applied Medical Sciences in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
| | - Mohammad Tariqul Islam
- Centre for Advanced Electronic and Communication Engineering, Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering & Built Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Malaysia
| | - Md Siam Talukder
- Department of Computer and Communication Engineering, Faculty of Computer Science and Engineering, Patuakhali Science and Technology, Patuakhali 8602, Bangladesh
| | - Md Samsuzzaman
- Department of Computer and Communication Engineering, Faculty of Computer Science and Engineering, Patuakhali Science and Technology, Patuakhali 8602, Bangladesh
| | - Mohsen Bakouri
- Department of Medical Equipment Technology, College of Applied, Medical Science, Majmaah University, Majmaah City 11952, Saudi Arabia
- Department of Physics, College of Arts, Fezzan University, Traghen City 71340, Libya
| | - Sofiene Mansouri
- Department of Biomedical Technology, College of Applied Medical Sciences in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
- Laboratory of Biophysics and Medical Technologies, Higher Institute of Medical Technologies of Tunis, University of Tunis El Manar, Tunis 1068, Tunisia
| | - Thamer Almoneef
- Electrical Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, Al-Kharj 16278, Saudi Arabia
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia
| | - Yousef Alharbi
- Department of Biomedical Technology, College of Applied Medical Sciences in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia
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3
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Three-Dimensional Microwave Head Imaging with GPU-Based FDTD and the DBIM Method. SENSORS 2022; 22:s22072691. [PMID: 35408305 PMCID: PMC9002921 DOI: 10.3390/s22072691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 03/22/2022] [Accepted: 03/29/2022] [Indexed: 11/16/2022]
Abstract
We present a preliminary study of microwave head imaging using a three-dimensional (3-D) implementation of the distorted Born iterative method (DBIM). Our aim is to examine the benefits of using the more computationally intensive 3-D implementation in scenarios where limited prior information is available, or when the target occupies an area that is not covered by the imaging array’s transverse planes. We show that, in some cases, the 3-D implementation outperforms its two-dimensional (2-D) counterpart despite the increased number of unknowns for the linear problem at each DBIM iteration. We also discuss how the 3-D algorithm can be implemented efficiently using graphic processing units (GPUs) and validate this implementation with experimental data from a simplified brain phantom. In this work, we have implemented a non-linear microwave imaging approach using DBIM with GPU-accelerated FDTD. Moreover, the paper offers a direct comparison of 2-D and 3-D microwave tomography implementations for head imaging and stroke detection in inhomogenous anatomically complex numerical head phantoms.
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Ahsan S, Guo Z, Miao Z, Sotiriou I, Koutsoupidou M, Kallos E, Palikaras G, Kosmas P. Design and Experimental Validation of a Multiple-Frequency Microwave Tomography System Employing the DBIM-TwIST Algorithm. SENSORS 2018; 18:s18103491. [PMID: 30332843 PMCID: PMC6209939 DOI: 10.3390/s18103491] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/08/2018] [Accepted: 10/12/2018] [Indexed: 11/16/2022]
Abstract
We present a first prototype of a wideband microwave tomography system with potential application to medical imaging. The system relies on a compact and robust printed monopole antenna which can operate in the 1.0–3.0 GHz range when fully immersed in commonly used coupling liquids, such as glycerine–water solutions. By simulating the proposed imaging setup in CST Microwave Studio, we study the signal transmission levels and array sensitivity for different target and coupling liquid media. We then present the experimental prototype design and data acquisition process, and show good agreement between experimentally measured data and results from the CST simulations. We assess imaging performance by applying our previously proposed two-dimensional (2-D) DBIM TwIST-algorithm to both simulated and experimental datasets, and demonstrate that the system can reconstruct simple cylindrical targets at multiple frequencies.
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Affiliation(s)
- Syed Ahsan
- Faculty of Natural and Mathematical Sciences, King's College London, Strand, London WC2B 4PH, UK.
| | - Ziwen Guo
- Faculty of Natural and Mathematical Sciences, King's College London, Strand, London WC2B 4PH, UK.
| | - Zhenzhuang Miao
- Faculty of Natural and Mathematical Sciences, King's College London, Strand, London WC2B 4PH, UK.
| | - Ioannis Sotiriou
- Faculty of Natural and Mathematical Sciences, King's College London, Strand, London WC2B 4PH, UK.
| | - Maria Koutsoupidou
- Faculty of Natural and Mathematical Sciences, King's College London, Strand, London WC2B 4PH, UK.
| | | | | | - Panagiotis Kosmas
- Faculty of Natural and Mathematical Sciences, King's College London, Strand, London WC2B 4PH, UK.
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5
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Mahmud MZ, Islam MT, Misran N, Almutairi AF, Cho M. Ultra-Wideband (UWB) Antenna Sensor Based Microwave Breast Imaging: A Review. SENSORS 2018; 18:s18092951. [PMID: 30189633 PMCID: PMC6165197 DOI: 10.3390/s18092951] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 06/28/2018] [Accepted: 06/29/2018] [Indexed: 11/16/2022]
Abstract
Globally, breast cancer is reported as a primary cause of death in women. More than 1.8 million new breast cancer cases are diagnosed every year. Because of the current limitations on clinical imaging, researchers are motivated to investigate complementary tools and alternatives to available techniques for detecting breast cancer in earlier stages. This article presents a review of concepts and electromagnetic techniques for microwave breast imaging. More specifically, this work reviews ultra-wideband (UWB) antenna sensors and their current applications in medical imaging, leading to breast imaging. We review the use of UWB sensor based microwave energy in various imaging applications for breast tumor related diseases, tumor detection, and breast tumor detection. In microwave imaging, the back-scattered signals radiating by sensors from a human body are analyzed for changes in the electrical properties of tissues. Tumorous cells exhibit higher dielectric constants because of their high water content. The goal of this article is to provide microwave researchers with in-depth information on electromagnetic techniques for microwave imaging sensors and describe recent developments in these techniques.
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Affiliation(s)
- Md Zulfiker Mahmud
- Department of AIS, Jagannath University, Dhaka 1100, Bangladesh.
- Centre of Advanced Electronic and Communication Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia.
| | - Mohammad Tariqul Islam
- Centre of Advanced Electronic and Communication Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia.
- Laboratory of Spacecraft Environment Interaction Engineering (LaSEINE), Kyushu Institute of Technology, Kitakyushu 804-8550, Japan.
| | - Norbahiah Misran
- Centre of Advanced Electronic and Communication Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia.
| | - Ali F Almutairi
- Electrical Engineering Department, Kuwait University, Kuwait City 13060, Kuwait.
| | - Mengu Cho
- Laboratory of Spacecraft Environment Interaction Engineering (LaSEINE), Kyushu Institute of Technology, Kitakyushu 804-8550, Japan.
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6
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Golnabi AH, Meaney PM, Paulsen KD. 3D microwave tomography of the breast using prior anatomical information. Med Phys 2016; 43:1933. [PMID: 27036589 DOI: 10.1118/1.4944592] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The authors have developed a new 3D breast image reconstruction technique that utilizes the soft tissue spatial resolution of magnetic resonance imaging (MRI) and integrates the dielectric property differentiation from microwave imaging to produce a dual modality approach with the goal of augmenting the specificity of MR imaging, possibly without the need for nonspecific contrast agents. The integration is performed through the application of a soft prior regularization which imports segmented geometric meshes generated from MR exams and uses it to constrain the microwave tomography algorithm to recover nearly uniform property distributions within segmented regions with sharp delineation between these internal subzones. METHODS Previous investigations have demonstrated that this approach is effective in 2D simulation and phantom experiments and also in clinical exams. The current study extends the algorithm to 3D and provides a thorough analysis of the sensitivity and robustness to misalignment errors in size and location between the spatial prior information and the actual data. RESULTS Image results in 3D were not strongly dependent on reconstruction mesh density, and the changes of less than 30% in recovered property values arose from variations of more than 125% in target region size-an outcome which was more robust than in 2D. Similarly, changes of less than 13% occurred in the 3D image results from variations in target location of nearly 90% of the inclusion size. Permittivity and conductivity errors were about 5 times and 2 times smaller, respectively, with the 3D spatial prior algorithm in actual phantom experiments than those which occurred without priors. CONCLUSIONS The presented study confirms that the incorporation of structural information in the form of a soft constraint can considerably improve the accuracy of the property estimates in predefined regions of interest. These findings are encouraging and establish a strong foundation for using the soft prior technique in clinical studies, where their microwave imaging system and MRI can simultaneously collect breast exam data in patients.
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Affiliation(s)
- Amir H Golnabi
- Department of Mathematical Sciences, Montclair State University, Montclair, New Jersey 07043
| | - Paul M Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755
| | - Keith D Paulsen
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755; Department of Radiology, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire 03755; Norris Cotton Cancer Center, Dartmouth Hitchcock Medical Center, Lebanon, New Hampshire 03756; and Advanced Surgical Center, Dartmouth Hitchcock Medical Center, Lebanon, New Hampshire 03756
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7
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Tselev A, Velmurugan J, Ievlev AV, Kalinin SV, Kolmakov A. Seeing through Walls at the Nanoscale: Microwave Microscopy of Enclosed Objects and Processes in Liquids. ACS NANO 2016; 10:3562-3570. [PMID: 26866377 PMCID: PMC5424529 DOI: 10.1021/acsnano.5b07919] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Noninvasive in situ nanoscale imaging in liquid environments is a current imperative in the analysis of delicate biomedical objects and electrochemical processes at reactive liquid-solid interfaces. Microwaves of a few gigahertz frequencies offer photons with energies of ≈10 μeV, which can affect neither electronic states nor chemical bonds in condensed matter. Here, we describe an implementation of scanning near-field microwave microscopy for imaging in liquids using ultrathin molecular impermeable membranes separating scanning probes from samples enclosed in environmental cells. We imaged a model electroplating reaction as well as individual live cells. Through a side-by-side comparison of the microwave imaging with scanning electron microscopy, we demonstrate the advantage of microwaves for artifact-free imaging.
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Affiliation(s)
- Alexander Tselev
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jeyavel Velmurugan
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899
- Maryland NanoCenter, University of Maryland, College Park, MD 20742
| | - Anton V. Ievlev
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Sergei V. Kalinin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Andrei Kolmakov
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899
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8
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Chandra R, Zhou H, Balasingham I, Narayanan RM. On the Opportunities and Challenges in Microwave Medical Sensing and Imaging. IEEE Trans Biomed Eng 2015; 62:1667-82. [DOI: 10.1109/tbme.2015.2432137] [Citation(s) in RCA: 185] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Epstein NR, Meaney PM, Paulsen KD. 3D parallel-detection microwave tomography for clinical breast imaging. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:124704. [PMID: 25554311 PMCID: PMC4272387 DOI: 10.1063/1.4901936] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A biomedical microwave tomography system with 3D-imaging capabilities has been constructed and translated to the clinic. Updates to the hardware and reconfiguration of the electronic-network layouts in a more compartmentalized construct have streamlined system packaging. Upgrades to the data acquisition and microwave components have increased data-acquisition speeds and improved system performance. By incorporating analog-to-digital boards that accommodate the linear amplification and dynamic-range coverage our system requires, a complete set of data (for a fixed array position at a single frequency) is now acquired in 5.8 s. Replacement of key components (e.g., switches and power dividers) by devices with improved operational bandwidths has enhanced system response over a wider frequency range. High-integrity, low-power signals are routinely measured down to -130 dBm for frequencies ranging from 500 to 2300 MHz. Adequate inter-channel isolation has been maintained, and a dynamic range >110 dB has been achieved for the full operating frequency range (500-2900 MHz). For our primary band of interest, the associated measurement deviations are less than 0.33% and 0.5° for signal amplitude and phase values, respectively. A modified monopole antenna array (composed of two interwoven eight-element sub-arrays), in conjunction with an updated motion-control system capable of independently moving the sub-arrays to various in-plane and cross-plane positions within the illumination chamber, has been configured in the new design for full volumetric data acquisition. Signal-to-noise ratios (SNRs) are more than adequate for all transmit/receive antenna pairs over the full frequency range and for the variety of in-plane and cross-plane configurations. For proximal receivers, in-plane SNRs greater than 80 dB are observed up to 2900 MHz, while cross-plane SNRs greater than 80 dB are seen for 6 cm sub-array spacing (for frequencies up to 1500 MHz). We demonstrate accurate recovery of 3D dielectric property distributions for breast-like phantoms with tumor inclusions utilizing both the in-plane and new cross-plane data.
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Affiliation(s)
- N R Epstein
- Schulich School of Engineering, University of Calgary, 2500 University Dr. NW, Calgary, Alberta T2N 1N4, Canada
| | - P M Meaney
- Thayer School of Engineering, Dartmouth College, 14 Engineering Dr., Hanover, New Hampshire 03755, USA
| | - K D Paulsen
- Thayer School of Engineering, Dartmouth College, 14 Engineering Dr., Hanover, New Hampshire 03755, USA
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10
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Chandra R, Johansson AJ, Gustafsson M, Tufvesson F. A microwave imaging-based technique to localize an in-body RF source for biomedical applications. IEEE Trans Biomed Eng 2014; 62:1231-41. [PMID: 25376034 DOI: 10.1109/tbme.2014.2367117] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In some biomedical applications such as wireless capsule endoscopy, the localization of an in-body radio-frequency (RF) source is important for the positioning of any abnormality inside the gastrointestinal tract. With knowledge of the location, therapeutic operations can be performed precisely at the position of the abnormality. Electrical properties (relative permittivity and conductivity) of the tissues and their distribution are utilized to estimate the position. This paper presents a method for the localization of an in-body RF source based on microwave imaging. The electrical properties of the tissues and their distribution at 403.5 MHz are found from microwave imaging and the position of an RF source is then estimated based on the image. The method is applied on synthetic noisy data, obtained after the addition of white Gaussian noise to simulated data of a simple circular phantom, and a realistic phantom in a 2-D case. The root-mean-square of the error distance between the actual and the estimated position is found to be within 10 and 4 mm for the circular and the realistic phantom, respectively, showing the capability of the proposed algorithm to work with a good accuracy even in the presence of noise for the localization of the in-body RF source.
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11
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Meaney PM, Golnabi AH, Epstein NR, Geimer SD, Fanning MW, Weaver JB, Paulsen KD. Integration of microwave tomography with magnetic resonance for improved breast imaging. Med Phys 2014; 40:103101. [PMID: 24089930 DOI: 10.1118/1.4820361] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Breast magnetic resonance imaging is highly sensitive but not very specific for the detection of breast cancer. Opportunities exist to supplement the image acquisition with a more specific modality provided the technical challenges of meeting space limitations inside the bore, restricted breast access, and electromagnetic compatibility requirements can be overcome. Magnetic resonance (MR) and microwave tomography (MT) are complementary and synergistic because the high resolution of MR is used to encode spatial priors on breast geometry and internal parenchymal features that have distinct electrical properties (i.e., fat vs fibroglandular tissue) for microwave tomography. METHODS The authors have overcome integration challenges associated with combining MT with MR to produce a new coregistered, multimodality breast imaging platform--magnetic resonance microwave tomography, including: substantial illumination tank size reduction specific to the confined MR bore diameter, minimization of metal content and composition, reduction of metal artifacts in the MR images, and suppression of unwanted MT multipath signals. RESULTS MR SNR exceeding 40 dB can be obtained. Proper filtering of MR signals reduces MT data degradation allowing MT SNR of 20 dB to be obtained, which is sufficient for image reconstruction. When MR spatial priors are incorporated into the recovery of MT property estimates, the errors between the recovered versus actual dielectric properties approach 5%. CONCLUSIONS The phantom and human subject exams presented here are the first demonstration of combining MT with MR to improve the accuracy of the reconstructed MT images.
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Affiliation(s)
- Paul M Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755
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12
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Semenov S, Kellam J, Sizov Y, Nazarov A, Williams T, Nair B, Pavlovsky A, Posukh V, Quinn M. Microwave tomography of extremities: 1. Dedicated 2D system and physiological signatures. Phys Med Biol 2011; 56:2005-17. [PMID: 21364265 DOI: 10.1088/0031-9155/56/7/006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microwave tomography (MWT) is a novel imaging modality which might be applicable for non-invasive assessment of functional and pathological conditions of biological tissues. Imaging of the soft tissue of extremities is one of its potential applications. The feasibility of this technology for such applications was demonstrated earlier. This is the first of two companion papers focused on an application of MWT for imaging of the extremity's soft tissues. The goal of this study is to assess the technical performance of the developed 2D MWT system dedicated for imaging of functional and pathological conditions of the extremity's soft tissues. Specifically, the system's performance was tested by its ability to detect signals associated with physiological activity and soft tissue interventions (circulatory related changes, blood flow reduction and a simulated compartmental syndrome)--the so-called physiological signatures. The developed 2D MWT system dedicated to the imaging of animal extremities demonstrates good technical performance allowing for stable and predictable data acquisition with reasonable agreement between the experimentally measured electromagnetic (EM) field and the simulated EM field within a measurement domain. Using the system, we were able to obtain physiological signatures associated with systolic versus diastolic phases of circulation in an animal extremity, reperfusion versus occlusion phases of the blood supply to the animal's extremity and a compartment syndrome. The imaging results are presented and discussed in the second companion paper.
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Affiliation(s)
- Serguei Semenov
- School of Medicine, Keele University, ISTM, Stoke-on-Trent ST4 7QB, UK.
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13
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Ashtari A, Noghanian S, Sabouni A, Aronsson J, Thomas G, Pistorius S. Using a priori information for regularization in breast microwave image reconstruction. IEEE Trans Biomed Eng 2010; 57:2197-208. [PMID: 20562033 DOI: 10.1109/tbme.2010.2051439] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Regularization methods are used in microwave image reconstruction problems, which are ill-posed. Traditional regularization methods are usually problem-independent and do not take advantage of a priori information specific to any particular imaging application. In this paper, a novel problem-dependent regularization approach is introduced for the application of breast imaging. A real genetic algorithm (RGA) minimizes a cost function that is the error between the recorded and the simulated data. At each iteration of the RGA, a priori information about the shape of the breast profiles is used by a neural network classifier to reject the solutions that cannot be a map of the dielectric properties of a breast profile. The algorithm was tested against four realistic numerical breast phantoms including a mostly fatty, a scattered fibroglandular, a heterogeneously dense, and a very dense sample. The tests were also repeated where a 4 mm x 4 mm tumor was inserted in the fibroglandular tissue in each of the four breast types. The results show the effectiveness of the proposed approach, which to the best of our knowledge has the highest resolution amongst the evolutionary algorithms used for the inversion of realistic numerical breast phantoms.
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Affiliation(s)
- Ali Ashtari
- Manitoba Hydro, Winnipeg, MB R3C0G8, Canada.
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14
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Fang Q, Meaney PM, Paulsen KD. Viable Three-Dimensional Medical Microwave Tomography: Theory and Numerical Experiments. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2010; 58:449-458. [PMID: 20352084 PMCID: PMC2844097 DOI: 10.1109/tap.2009.2037691] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Three-dimensional microwave tomography represents a potentially very important advance over 2D techniques because it eliminates associated approximations which may lead to more accurate images. However, with the significant increase in problem size, computational efficiency is critical to making 3D microwave imaging viable in practice. In this paper, we present two 3D image reconstruction methods utilizing 3D scalar and vector field modeling strategies, respectively. Finite element (FE) and finite-difference time-domain (FDTD) algorithms are used to model the electromagnetic field interactions in human tissue in 3D. Image reconstruction techniques previously developed for the 2D problem, such as the dual-mesh scheme, iterative block solver, and adjoint Jacobian method are extended directly to 3D reconstructions. Speed improvements achieved by setting an initial field distribution and utilizing an alternating-direction implicit (ADI) FDTD are explored for 3D vector field modeling. The proposed algorithms are tested with simulated data and correctly recovered the position, size and electrical properties of the target. The adjoint formulation and the FDTD method utilizing initial field estimates are found to be significantly more effective in reducing the computation time. Finally, these results also demonstrate that cross-plane measurements are critical for reconstructing 3D profiles of the target.
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Affiliation(s)
- Qianqian Fang
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital (MGH), Charlestown, MA 02129 USA and also with Harvard Medical School, Boston, MA 02115 USA ()
| | - Paul M. Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA ()
| | - Keith D. Paulsen
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA and also with the Radiobiology and Bioengineering Research Program, Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA ()
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15
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Lavarello RJ, Oelze ML. Tomographic reconstruction of three-dimensional volumes using the distorted born iterative method. IEEE TRANSACTIONS ON MEDICAL IMAGING 2009; 28:1643-53. [PMID: 19574162 DOI: 10.1109/tmi.2009.2026274] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Although real imaging problems involve objects that have variations in three dimensions, a majority of work examining inverse scattering methods for ultrasonic tomography considers 2-D imaging problems. Therefore, the study of 3-D inverse scattering methods is necessary for future applications of ultrasonic tomography. In this work, 3-D reconstructions using different arrays of rectangular elements focused on elevation were studied when reconstructing spherical imaging targets by producing a series of 2-D image slices using the 2-D distorted Born iterative method (DBIM). The effects of focal number f/#, speed of sound contrast c, and scatterer size were considered. For comparison, the 3-D wave equation was also inverted using point-like transducers to produce fully 3-D DBIM image reconstructions. In 2-D slicing, blurring in the vertical direction was highly correlated with the transmit/receive elevation point-spread function of the transducers for low c. The eventual appearance of overshoot artifacts in the vertical direction were observed with increasing c. These diffraction-related artifacts were less severe for smaller focal number values and larger spherical target sizes. When using 3-D DBIM, the overshoot artifacts were not observed and spatial resolution was improved. However, results indicate that array configuration in 3-D reconstructions is important for good image reconstruction. Practical arrays were designed and assessed for image reconstruction using 3-D DBIM.
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Affiliation(s)
- Roberto J Lavarello
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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Semenov S, Kellam J, Althausen P, Williams T, Abubakar A, Bulyshev A, Sizov Y. Microwave tomography for functional imaging of extremity soft tissues: feasibility assessment. Phys Med Biol 2007; 52:5705-19. [PMID: 17804890 DOI: 10.1088/0031-9155/52/18/015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It is important to assess the viability of extremity soft tissues, as this component is often the determinant of the final outcome of fracture treatment. Microwave tomography (MWT) and sensing might be able to provide a fast and mobile assessment of such properties. MWT imaging of extremities possesses a complicated, nonlinear, high dielectric contrast inverse problem of diffraction tomography. There is a high dielectric contrast between bone and soft tissue in the extremities. A contrast between soft tissue abnormalities is less pronounced when compared with the high bone-soft tissue contrast. The goal of this study was to assess the feasibility of MWT for functional imaging of extremity soft tissues, i.e. to detect a relatively small contrast within soft tissues in closer proximity to high contrast boney areas. Both experimental studies and computer simulation were performed. Experiments were conducted using live pigs with compromised blood flow and compartment syndrome within an extremity. A whole 2D tomographic imaging cycle at 1 GHz was computer simulated and images were reconstructed using the Newton, MR-CSI and modified Born methods. Results of experimental studies demonstrate that microwave technology is sensitive to changes in the soft tissue blood content and elevated compartment pressure. It was demonstrated that MWT is feasible for functional imaging of extremity soft tissues, circulatory-related changes, blood flow and elevated compartment pressure.
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Affiliation(s)
- Serguei Semenov
- Keele University, School of Medicine, ISTM, Stoke-on-Trent, ST4 7QB, UK.
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17
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Jacobsen S, Rolfsnes HO, Stauffer PR. Characteristics of Microstrip Muscle-Loaded Single-Arm Archimedean Spiral Antennas as Investigated by FDTD Numerical Computations. IEEE Trans Biomed Eng 2005; 52:321-30. [PMID: 15709670 DOI: 10.1109/tbme.2004.840502] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The radiation characteristics and mode of operation of single-arm, groundplane backed, Archimedean spiral antennas are investigated by means of conformal finite difference time domain numerical analysis. It is shown that this antenna type may be categorized as a well-matched, broadband, circularly polarized traveling wave structure that can be fed directly by nonbalanced coaxial networks. The study further concentrates on relevant design and description features parameterized in terms of measures like radiation efficiency, sensing depth, directivity, and axial ratio of complementary polarizations. We document that an antenna of only 30-mm transverse size produces circularly polarized waves in a two-octave frequency span (2-8 GHz) with acceptable radiation efficiency (76%-94%) when loaded by muscle-like tissue.
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Affiliation(s)
- Svein Jacobsen
- Electrical Engineering Group, Institute of Physics, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway.
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18
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Meaney PM, Fanning MW, Paulsen KD, Lit D, Pendergrass SA, Fang Q, Moodie KL. Microwave thermal imaging: initial in vivo experience with a single heating zone. Int J Hyperthermia 2004; 19:617-41. [PMID: 14756452 DOI: 10.1080/0265673031000140822] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The deployment of hyperthermia as a routine adjuvant to radiation or chemotherapy is limited largely by the inability to devise treatment plans which can be monitored through temperature distribution feedback during therapy. A non-invasive microwave tomographic thermal imaging system is currently being developed which has previously exhibited excellent correlation between the recovered electrical conductivity of a heated zone and its actual temperature change during phantom studies. To extend the validation of this approach in vivo, the imaging system has been re-configured for small animal experiments to operate within the bore of a CT scanner for anatomical and thermometry registration. A series of 5-7 day old pigs have been imaged during hyperthermia with a monopole antenna array submerged in a saline tank where a small plastic tube surgically inserted the length of the abdomen has been used to create a zone of heated saline at pre-selected temperatures. Tomographic microwave data over the frequency range of 300-1000 MHz of the pig abdomen in the plane perpendicular to the torso is collected at regular intervals after the tube saline temperatures have settled to the desired settings. Images are reconstructed over a range of operating frequencies. The tube location is clearly visible and the recovered saline conductivity varies linearly with the controlled temperature values. Difference images utilizing the baseline state prior to heating reinforces the linear relationship between temperature and imaged saline conductivity. Demonstration of in vivo temperature recovery and correlation with an independent monitoring device is an important milestone prior to clinical integration of this non-invasive imaging system with a thermal therapy device.
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Affiliation(s)
- P M Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.
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19
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Fang Q, Meaney PM, Geimer SD, Streltsov AV, Paulsen KD. Microwave image reconstruction from 3-D fields coupled to 2-D parameter estimation. IEEE TRANSACTIONS ON MEDICAL IMAGING 2004; 23:475-484. [PMID: 15084072 DOI: 10.1109/tmi.2004.824152] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
An efficient Gauss-Newton iterative imaging technique utilizing a three-dimensional (3-D) field solution coupled to a two-dimensional (2-D) parameter estimation scheme (3-D/2-D) is presented for microwave tomographic imaging in medical applications. While electromagnetic wave propagation is described fully by a 3-D vector field, a 3-D scalar model has been applied to improve the efficiency of the iterative reconstruction process with apparently limited reduction in accuracy. In addition, the image recovery has been restricted to 2-D but is generalizable to three dimensions. Image artifacts related primarily to 3-D effects are reduced when compared with results from an entirely two-dimensional inversion (2-D/2-D). Important advances in terms of improving algorithmic efficiency include use of a block solver for computing the field solutions and application of the dual mesh scheme and adjoint approach for Jacobian construction. Methods which enhance the image quality such as the log-magnitude/unwrapped phase minimization were also applied. Results obtained from synthetic measurement data show that the new 3-D/2-D algorithm consistently outperforms its 2-D/2-D counterpart in terms of reducing the effective imaging slice thickness in both permittivity and conductivity images over a range of inclusion sizes and background medium contrasts.
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Affiliation(s)
- Qianqian Fang
- Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755, USA.
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