Feasibility of focused microwave array system for tumour irradiation

Radiofrequency hyperthermia has been used for treatment of cancer and relies on reduced blood flow through the tumour. Microwave-induced hyperthermia is proposed by means of an orthogonal-array system which produces a focal region for spatially selective internal heating within an attenuating medium.     

Three-dimensional microwave tomography: experimental prototype ofthe system and vector Born reconstruction method

A method of image reconstruction in three-dimensional (3-D) microwave tomography in a weak dielectric contrast case has been developed. By utilizing only one component of the vector electromagnetic field this method allows successful reconstruction of images of 3-D mathematical phantoms. A prototype of the 3-D microwave tomographic system capable of imaging 3-D objects has been constructed. The system operates at a frequency of 2.36 GHz and utilizes a code-division technique. With dimensions of the cylindrical working chamber z = 40 cm and d = 60 cm, the system allows measurement of an attenuation up to 120 dB having signal-to-noise ratio about 30 dB. The direct problem solutions for different mathematical approaches were compared with an experimentally measured field distribution inside the working chamber. The tomographic system and the reconstruction method were tested in simple experimental imaging.     

Frequency optimization of focused microwave hyperthermia applicators

We study the design optimization of focused microwave hyperthermia applicators. For a fixed aperture size and a given penetration depth, an optimal frequency is determined by considering the tradeoff between heat localization and medium loss. At this optimal frequency, the deficiencies of conventional applicators; namely, large spillover, shallow penetration, and excessive surface heating, can be significantly compensated by focused applicators.     

A confocal microwave imaging algorithm for breast cancer detection

We present a computationally efficient and robust image reconstruction algorithm for breast cancer detection using an ultrawideband confocal microwave imaging system. To test the efficacy of this approach, we have developed a two-dimensional (2-D) anatomically realistic MRI-derived FDTD model of the cancerous breast. The image reconstruction algorithm is applied to FDTD-computed backscatter signals, resulting in a microwave image that clearly identifies the presence and location of the malignant lesion. These simulations demonstrate the feasibility of detecting and imaging small breast tumors using this novel approach     

A self-steered array system for microwave communications

The paper presents a self-steered algorithm that can be used to correct pointing errors in microwave communications. The algorithm is based on the fact that the output power of an optimized beamformer achieves a local maximum if the steering vector coincides with that of the desired signal, as long as the interferences are outside the mainbeam. By approximating the steering vector by its first-order Taylor series expansion in terms of the steering angles, the maximization process reduces to a two-dimensional optimization problem. Numerical results are presented to illustrate the performance achievable     

Numerical and experimental assessments of focused microwave thermotherapy system at 925 MHz

This work investigated three‐dimensional (3D) focused microwave thermotherapy (FMT) at 925 MHz for a human tissue mimicking phantom using the time reversal (TR) principle for musculoskeletal disorders. We verified the proposed TR algorithm by evaluating the possibility of 3D beam focusing through simulations and experiments. The simulation, along with the electromagnetic and thermal analyses of the human tissue mimicking phantom model, was conducted by employing the Sim4Life commercial tool. Experimental validation was conducted on the developed FMT system using a fabricated human tissue mimicking phantom. A truncated threshold method was proposed to reduce the unwanted hot spots in a normal tissue region, wherein a beam was appropriately focused on a target position. The validation results of the simulation and experiments obtained by utilizing the proposed TR algorithm were shown to be acceptable. Effective beam focusing at the desired position of the phantom could be achieved.     

A TSVD analysis of microwave inverse scattering for breast imaging

A variety of methods have been applied to the inverse scattering problem for breast imaging at microwave frequencies. While many techniques have been leveraged toward a microwave imaging solution, they are all fundamentally dependent on the quality of the scattering data. Evaluating and optimizing the information contained in the data are, therefore, instrumental in understanding and achieving optimal performance from any particular imaging method. In this paper, a method of analysis is employed for the evaluation of the information contained in simulated scattering data from a known dielectric profile. The method estimates optimal imaging performance by mapping the data through the inverse of the scattering system. The inverse is computed by truncated singular-value decomposition of a system of scattering equations. The equations are made linear by use of the exact total fields in the imaging volume, which are available in the computational domain. The analysis is applied to anatomically realistic numerical breast phantoms. The utility of the method is demonstrated for a given imaging system through the analysis of various considerations in system design and problem formulation. The method offers an avenue for decoupling the problem of data selection from the problem of image formation from that data.     

A new microwave device for rapid thermal fixation of the murine brain.

A microwave applicator was developed to provide rapid thermal fixation of enzymes in the murine brain. Although the power output of the device is only 1.3 kW, whole-brain levels of acetyicholine after microwave fixation are comparable to those observed at a power output of 5 kW, and are markedly higher than those obtained by a conventional method (freezing) of fixation.     

Computer-aided prototype system for nose surgery

Rhinoplasty, or surgery to reshape the nose, is one of the most common of all plastic-surgery procedures. Rhinoplasty can enhance a patient's appearance and self-confidence, may also correct a birth defect or injury, or help relieve some breathing problem. In this paper, we present a three-dimensional (3D) surgical simulation system, which can assist surgeons in planning rhinoplasty procedures. This system employs computer graphics and image-processing techniques for the simulation of a rhinoplasty. Although the presented algorithms themselves are not new, the proposed system exploits the new idea to apply 3D morphing for rhinoplasty, and simulation results are useful for the physicians. According to patients' expectation of what they would like their noses to look like, our system simulates expected results. Our tools provide quantitative measurements of a nose structure. Using these quantitative results, surgeons can arrange appropriate preoperative plans for patients. Finally, experimental results and experiences are reported to evaluate the usefulness of the proposed system     

A multiview microwave imaging system for two-dimensional penetrableobjects

A microwave imaging system is based on a multiview numerical solution to the integral equation of 2D transverse magnetic (TM) scattering is proposed. This solution is achieved by the moment method, and a pseudoinversion transformation is used to face ill-conditioning problems. All experimental setup is described that uses a scanning subsystem for measuring the values of the scattered electric field inside an observation domain located outside the investigation one (i.e., the area containing the cross sections of cylindrical dielectric scatters). Rotations of the investigation domain with respect to the scanning subsystem and the transmitting antenna allow a multiview imaging process. The imaging system does not require plane-wave illumination and does not use any first-order approximations; hence, it may be used even in the case of strong scatterers. The offline and once-and-for-all computation of the pseudoinverse matrix allows an inexpensive reconstruction in terms of computer resources. Some tests of the system were carried out, and the results are reported     

A prototype expert system in OPS5 for data error detection

A prototype expert system has been developed in the OPS5 language to perform error checking on data which spacecraft builders/users supply to the NASA Goddard Space Flight Center for processing on the Communications Link Analysis and Simulation System (CLASS) computer. This prototype expert system, called Trajectory Preprocessing System (TRAPS), contains 49 rules and at present runs on an IBM PC in the OPS5+ software package from Artelligence, Inc. In its operational phase, TRAPS will run in the Oak Ridge Production Language (ORPL) on the CLASS computer (a Perkin-Elmer 3244 supermini). ORPL, an implementation of OPS5 by the Oak Ridge National Laboratory in MULTIFORTH on a Hewlett-Packard 9836 desktop computer, is now being ported to SS-FORTH on the CLASS computer. This paper discusses the expert system problem domain, development approach, tools, results and future plans stemming from the TRAPS project.     

A matched-filter FDTD-based time reversal approach for microwave breast cancer detection

Based on the finite-difference time-domain (FDTD) method, a numerical time-reversal (TR) algorithm for microwave breast cancer detection, already presented in previous work , , is further examined. In , we assumed that the exact field scattered from the tumor-like anomaly is available for backpropagation, and it was shown that the time reversal process is robust to breast inhomogeneities and uncertainties of the skin thickness or electric properties. In this paper, we use the same time reversal mirror (TRM) and two-dimensional (2-D) breast model based on magnetic resonance imaging (MRI) data, but examine the realistic situation where the target response is not known and can only be estimated from the total signal, which is dominated by clutter. A matched-filter approach to solve this signal processing problem is proposed and applied to the TRM data. Detection and localization is achieved for different target locations, and the ability of the time reversal algorithm to avoid false alarms is demonstrated.     

A novel design of thermal anomaly for mammary gland tumor phantom for microwave radiometer

Microwave radiometry is the spectral measurement technique of resolving electromagnetic radiation of all matters which temperature is above absolute zero. This technique utilizes the electromagnetic noise field generated by a thermal volume similar to a mechanism existing in biological tissues. One particular application of microwave radiometry is for analyzing temperature differentials of inside of human body to detect and diagnose some crucial pathological conditions. For the general evaluation of a microwave radiometer, we propose a new type of phantom containing a mammary gland tumor imitator by considering biological heat diffusion effects propagated by a real tumor. Theoretical researches of human tumor revealed the fact that temperature distribution of tissues around a tumor formed a Gaussian statistics. To comply with the physiological property of the real tumor, we built a mammary gland tumor imitator composed of two parts (pseudotumor and thermal anomaly) and observed its temperature distribution when it was placed inside a phantom. Our results showed that the thermal properties of tumor imitator well agreed with heat-transfer properties of a real tumor and the proportional linear relationship existed between the location of tumor imitator and the intensity of radiometer measurements. From this relationship, we could also estimate several parameters related with our phantom, such as the minimum detectable size and maximum detectable depth of a tumor imitator.     

一种用于靶场监控的小微波电视传输系统

采用ＭＣ１４５１５２／ＭＣ１２０２２大规模集成电路数字频率合成器件直接调制的微波电视传输系统，应用于靶场监控系统，灵活适用、稳定可靠、成本低，在监控系统的远场靶点图像传输中发挥重要作用。     

聚焦Tm激光与眼角膜热作用的研究

随着全世界老龄化的加重,老年人的生活质量越来越受到重视,而老花眼（老视）是每个人步人中年都要面对的视觉问题。激光热成型术（LTK）在矫正老视的临床中占有重要的应用前景。为了研究新型Tm激光与角膜热作用的生物学效果,采用有限元方法模拟了聚焦Tm激光各参数作用下角膜组织内温度场的分布。模拟结果表明激光有效穿透深度与激光功率密度和时间都是正向相关,而与能量密度的正向相关性较差：激光作用时间越长,角膜组织中的温度梯度越小。实验上,采用猪眼角膜为实验对象,在不同激光功率密度作用下,利用病理切片观察角膜的变化,发现功率密度在86W／cm^2至98W／cm^2,能量密度在172J／cm^2至294J／cm^2范围内,角膜组织有合适的穿透深度：350μm至425μm和明显的力学变化,能较好实现角膜中胶原的热收缩。     

A system for controlled microwave heating of small samples.

A system for the controlled thawing and heating of small samples in a waveguide is described. A means of maintaining constant absorbed power within the sample over a wide range of sample parameters is a major feature of the system. Provision for sensing the melting point of immersed samples is include. Samples are continuously rotated to improve heating uniformity.     

高灵敏度的微波取样系统

本文描述一个新的微波取样系统,使用测量数据的数字处理而提高了灵敏度.由于取样示波器中电子电路的时间漂移,给信号处理带来了更大的麻烦.本系统开发了一个适当的方法可以补偿时间漂移.本文讨论了噪声的影响,给随机的多余时间信号以信噪比的函数.最后举例说明,如何将此法应用到自动取样系统中去.     

A GaAs phase digitizing and summing system for microwave signalstorage

The analysis, design, and development of a microwave signal storage prototype system using phase-quantization sampling are described. A GaAs 4-bit D/A converter has been demonstrated in a 3-bit DRFM (digital RF memory) prototype system with digital Si emitter-coupled logic (ECL) and RF microwave components at a sample rate of 200 MHz and exhibiting typically a -17-dBc harmonic suppression. A monolithic GaAs A/D and D/A converter has been demonstrated within an RF signal acquisition system. Performance data on the monolithic sampler reveal that the 3-bit quantization system exhibits signal reconstruction with harmonic suppression exceeding 25 dB across an IF bandwidth of greater than 900 MHz     

A fieldbus prototype for educational purposes

One of the problems with instrumentation systems is the interconnection between the multiple devices with different communication protocols. Exacerbating this problem are two typical requirements of interconnection: minimize cabling cost and avoid degradation of the signal during transmission. Cabling cost can be reduced through several multidrop communication systems: industrial local area networks or wireless communication. Reduction of signal to noise can restrict system performance and the quality of manufactured products, even if high-accuracy devices are used. Another problem in the field of manufacturing instrumentation networks is that industry uses multiple solutions to interconnect instrumentation with different communication protocols. This article presents the development of a prototype for an instrumentation network with the goal to study and analyze the characteristics of the different communication solutions. The overall system contains a large number of instrumentation devices, which is a great advantage for educational purposes and laboratory experiments. The students can configure, calibrate, and operate a large number of instruments connected to different segments of the DCS. We also connected some current-loop devices to the FF system to evaluate their performance when connected to a fully digital network. Results from the prototype DCS show that networking between different instrumentation devices and protocols can be successful and that a hybrid solution using conventional 4-20 mA current loop and fully digital instrumentation can work to leverage existing analogue systems. Future work will include the development of a fieldbus network analyzer to trace messages in the network and study the quality of FF service parameters, such as packet loss and delay measurement, as a function of network load.