Showing papers in "The Journal of microwave power in 1979"
TL;DR: Detailed results of a study of breast cancer detection at 1.3 and 3.3 GHz are presented, including the dependence of detection rates on microwave frequency, time, tumor depth, and tumor size.
Abstract: We review the physical principles, method of operation, measurement limitations, and potential medical applications of microwave thermography. We present detailed results of a study of breast cancer detection at 1.3 and 3.3 GHz, including the dependence of detection rates on microwave frequency, time, tumor depth, and tumor size. At 1.3 GHz, microwave thermography detects breast cancer as well as infrared thermography (true-positive rate = 0.76 when true-negative rate = 0.63). When the two methods are combined, the true-positive rate increases by about 0.1 over that of either method alone.
71 citations
TL;DR: In this article, a microwave power source (3-10W) operating in the 500 MHz to 1.3 GHz frequency range, coaxial transmission line, and a monopole antenna was developed and characterized for delivering heat directly into tumors.
Abstract: A microwave system has been developed and characterized for delivering heat directly into tumors. This system employs a microwave power source (3-10W) operating in the 500 MHz to 1.3 GHz frequency range, coaxial transmission line, and a monopole antenna. Absorbed power was measured in saline, in tissue equivalent phantoms, and in tumors in live and dead mice. Antennas were designed to operate at 500 MHz and 1 GHz, and the critical design parameters have been identified for this system. Analytical and experimental results obtained in our laboratory suggest that this system is capable of providing controlled temperature distributions appropriate for hyperthermia in animal tumors. Theoretical results predict that 3 GHz may be an optimum choice for this system in animal tumors of approximately 1 cm diameter; the microwave antenna system provides a heat distribution superior to that obtained using a resistance heater of similar dimensions. We propose that further development of this approach may overcome some of the problems associated with other systems which use external radiation sources, and implications for clinical application of this system are discussed.
68 citations
TL;DR: Thermography at centimeter and millimeter wavelengths can measure subsurface temperatures of the human body and recent clinical results in treatment monitoring of arthritis, detection of tumors in the neck and brain area, and breast cancer are reviewed.
Abstract: Thermography at centimeter and millimeter wavelengths can measure subsurface temperatures of the human body. Radiative and bio-heat transfer influence the wavelength dependent subcutaneous temperature and spatial resolution. Recent clinical results in treatment monitoring of arthritis, detection of tumors in the neck and brain area, and breast cancer are reviewed.
44 citations
TL;DR: It is concluded that the safe value for continuous exposure to 10 mW/cm2, widely used in Western countries, appears to provide an adequate margin of safety for both occupational and environmental exposure for frequencies above about 1 GHz.
Abstract: This report examines the bases for developing radiofrequency exposure standards which can be related to the thermogenic properties of electromagnetic fields, A review of selected biological effects, including dosimetric data and simulation of human thermodynamic characteristics that are pertinent to standards development, is presented Based on the analogy of thermal-stress standards that have been developed for hot industrial environments, limits on increases of body temperature are proposed as criteria for limiting exposure to radiofrequency fields, ie, occupational exposures involving deep heating of the whole body should not increase core temperature in excess of 1°C Since energy deposition from exposure to some RF fields is likely to be non-uniform and may be high in tissues that are not adapted to high rates of absorption or dissipation of thermalizing energy, means are needed to adjust focal thermal loading against the whole-body averages A limit on core temperature is inadequate when f
43 citations
TL;DR: In this article, surface wave microwave excitation structures can be used to produce relatively long plasma columns at atmospheric pressure, which are used for trace gas analysis by optical emission spectroscopy, production of flames of various compositions, welding, and spectral lamps.
Abstract: Surface wave microwave excitation structures can be used to produce relatively long plasma columns at atmospheric pressure. Characteristics of this new versatile plasma are given. Applications such as trace gas analysis by optical emission spectroscopy, production of flames of various compositions, welding, and spectral lamps are presented.
39 citations
TL;DR: Long-Evans male adult rats were exposed for sixteen weeks to 2450-MHz CW microwaves at an average power density of mW/cm2, and measures of levels of 17-ketosteroids in urine, mass of adrenals, heart, and liver at the end of the sixteen-week period of exposure, revealed no indications of stress.
Abstract: Long-Evans male adult were exposed for sixteen weeks to 2450-MHz CW microwaves at an average power density of 5 mW/cm2. The resulting dose rate was 1.23 (±0.025 SEM) mW/g. The animals were exposed eight hours a day, five days a week, for a total of 640 h in a monopole-above-ground radiation chamber while housed in plexiglas holding cages. Daily measures of body mass and of food and water intakes indicated no statistically significant effects of microwave irradiation. Biweekly stabilimetric tests immediately after exposure revealed a significant depression of behavioral activity by 15 microwave-exposed rats as compared with 15 sham-exposed animals. Measures of tocomotor activity based on revolutions of a running wheel, which were obtained during 12-h periods between each 8-h exposure, showed no significant effect of irradiation. Blood sampled after 2, 6, 10, and 14 weeks of exposure indicated slight alterations of sulfhydryl groups, and of red and white blood-cell counts. Measures of levels of 17-k...
36 citations
TL;DR: A system of miniature anechoic chambers for chronically exposing a sizeable number of animals to microwave radiation was developed in which each animal can be individually exposed to microwaves or sham-exposed under controlled environmental conditions.
Abstract: A system of miniature anechoic chambers for chronically exposing a sizeable number of animals to microwave radiation was developed in which each animal can be individually exposed to microwaves or sham-exposed under controlled environmental conditions. Each animal is supplied with food and water by means designed to eliminate undesirable perturbations of the field. Field patterns in each chamber correspond closely to those made in large anechoic chambers; measurements indicate that a power density of 169 μW/cm2 per watt of input power can be provided, which results in peak SAR levels of 0.37 W/kg in cadavers of exposed rats.
31 citations
TL;DR: The combined process may be used - in hyperthermia therapy, for measurement and control of the local temperature, - in some diagnoses using radiometry to detect diseased tissue.
Abstract: A basic experiment showing the possibility of combining microwave local heating of subcutaneous living tissue, and microwave radiometry by the same system was carried out. The combined process may be used— in hyperthermia therapy, for measurement and control of the local temperature,— in some diagnoses using radiometry to detect diseased tissue.
30 citations
TL;DR: A diploid strain of yeast that is sensitive to genetic insult was used to study the effects of temperature and of microwave irradiation on cell survival, induction of mitotic recombination, and induction of cytoplasmic "petite" mutations.
Abstract: Recent microwave experiments have shown frequency dependent influences on the growth rate of bacteria. To determine whether microwaves are able to affect growth (or to induce lesions in cellular DNA of yeast cells), experiments were performed with millimeter microwaves at frequencies between 70 and 75 GHz. Saccharomyces cerevisiae cells were irradiated on millipore filter discs placed on agar plates in open petri dishes. A diploid strain of yeast (D5 Zimmermann), that is sensitive to genetic insult was used to study the effects of temperature and of microwave irradiation on cell survival, induction of mitotic recombination, and induction of cytoplasmic “petite” mutations. No evidence of altered survival, impared function, or structural injury was seen at either frequency, even at power densities as high as 60 mW/cm2. Conventional heating had no deleterious effects until temperatures of specimens exceeded 50°C, In addition, two haploid strains of yeast of opposite mating type were compared with res...
28 citations
TL;DR: Decreased viability of cells was noted in all cultures tested after radiation at power densities of 30 mW/cm2 or more; however, no reliable changes in genetic events occurred.
Abstract: Strain D4 of the yeast Saccharomyces cerevisiae, and strains TA-1535, TA-100 and TA-98 of the bacterium Salmonella typhimurium, were exposed to 2.45-GHz continuous wave or 8.5- to 9.6-GHz pulsed electromagnetic radiation (EMR) at various powder densities from 1 to 45 mW/cm2. The temperature during radiation was maintained at 30°C for yeast cultures and at 37°C for bacterial cultures. The studies revealed no increase in mutations or of mitotic gene conversions when cells were radiated for two hours or less. Decreased viability of cells was noted in all cultures tested after radiation at power densities of 30 mW/cm2 or more; however, no reliable changes in genetic events occured.
25 citations
TL;DR: Results indicate that activity in the central auditory pathway as induced by pulsed microwaves only requires stimulation of the cochlea and Conduction of pressure waves through the bones of the calvarium appears to be the mechanism responsible in perception of pulsing microwaves.
Abstract: The contribution of the ossicles (middle-ear bones) to auditory perception of microwaves was evaluated by the brain-stem evoked response (BER). Amplitude and latency of BERs were recorded from guinea pigs that were stimulated at various intensities by acoustic pulses coupled to the auditory canal or via bone conduction, and by microwave pulses. Blocking of the external ear, middle-ear damping, and middle-ear destruction produced little change in the BERs that were elicited by microwave pulses. Results indicate that activity in the central auditory pathway as induced by pulsed microwaves only requires stimulation of the cochlea. Conduction of pressure waves through the bones of the calvarium appears to be the mechanism responsible in perception of pulsed microwaves.
TL;DR: In this article, it was shown that the overall energy conversion efficiency of a microwave oven can be raised from 40% to 65% with frequency-agile, broadband sources such as transistors and voltage tunable magnetrons.
Abstract: It is shown that the overall energy conversion efficiency of a microwave oven can be raised from 40% to 65% with frequency-agile, broadband sources such as transistors and voltage tunable magnetrons. An even greater improvement in efficiency is shown to be possible for very light loads.Heating uniformity is improved considerably when the source is dynamically and sequentially tuned to discrete frequencies at constant power over a 4% bandwidth, The minimum bandwidth for good heating uniformity is 40 MHz at 2450 MHz. An automatic tuning circuit is described which samples reflected power and holds the source at the optimum frequency. A method by which temperature patterns can be programmed is suggested. Results on efficiency are given for a voltage tunable magnetron and compared with values obtained from a conventional magnetron source.
TL;DR: In this article, a compact form of stripline sensor has been developed which is robust in construction and suitable for measuring moisture contents up to 100% (wet basis), which offers potential for further miniaturisation of microwave moisture meter circuitry.
Abstract: A compact form of stripline sensor has been developed which is robust in construction and suitable for measuring moisture contents up to 100% (wet basis). It offers potential for further miniaturisation of microwave moisture meter circuitry.
TL;DR: In this article, the current status of microwave effects on the blood-brain barrier is reviewed and twenty-five references are sited, including five references from the National Institute of Neurological Disorders and Stroke.
Abstract: Current status of microwave effects on the blood-brain barrier is reviewed. Twenty-five references are sited.
TL;DR: The results indicate that carbon-loaded Teflon electrodes can be implanted chronically to record the EEG in animals during the course of microwave radiation.
Abstract: Conventional metal electrodes can cause serious modification and intensification of the rate of energy absorption in tissues during exposure of animals to microwaves. Carbon-loaded Teflon with a conductivity close to that of tissue has been implanted and maintained for four to six months at cortical and subcortical locations in rabbits. The EEG and its spectrum as recorded from the carbon-loaded Teflon electrodes are comparable to those recorded from conventional metal electrodes. Histological examination showed good tissue compatibility. Recordings made during acute exposure of rabbits to microwave radiation (2450-MHz) at 100 mW/cm2 showed no electromagnetic interference. The results indicate that carbon-loaded Teflon electrodes can be implanted chronically to record the EEG in animals during the course of microwave radiation.
TL;DR: Therapeutic efficacy by hyperthermia was demonstrated by comparing MTG-B diameters in mice following control, sham orHyperthermia treatment, and it is proposed that this system could be employed clinically to provide very localhyperthermia in deep-seated tumors.
Abstract: A system has been developed for producing local hyperthermia in small animal tumors by means of an invasive needle microwave antenna. Thermal distributions produced by this system using 1 GHz microwaves have been characterized in mammary adenocarcinomas (MTG-B) implanted in thighs of C3H mice. Therapeutic efficacy by hyperthermia was demonstrated by-comparing MTG-B diameters in mice following control, sham or hyperthermia treatment. It is proposed that this system could be employed clinically to provide very local hyperthermia in deep-seated tumors.
TL;DR: It is shown that microwave-evoked auditory response of cats closely resembles that evoked by acoustic pulse.
Abstract: Rectangular pulse-modulated microwave radiation has been shown to produce auditory responses in mammals. It is therefore reasonable to explore the possibility of using microwave pulses to achieve an estimate of sensori-neural involvement in the objective evaluation of human hearing and to assess the presence of tumors or brainstem lesions in patients with neurological disorders. In this paper we shall show that microwave-evoked auditory response of cats closely resembles that evoked by acoustic pulse. We shall also give preliminary results obtained from electrodes fastened to the vertex of the skull after successive coagulative production of lesions in the inferior colliculus, lateral lemniscus, and superior olivary nucleus.
TL;DR: In this article, the authors examined factors that affect the dielectric properties of frozen meats at low temperatures and established a predictive modeling basis for these properties and to obtain a more basic understanding of low temperature Dielectric behavior in biological materials.
Abstract: Factors that affect the dielectric properties of frozen meats at low temperatures are examined in an attempt to establish a predictive modelling basis for these properties and to obtain a more basic understanding of low temperature dielectric behavior in biological materials. Dielectric constant and loss measurements were made for frozen samples of beef, chicken breast, chicken thigh, pork and turkey roll using a short-circuited coaxial line technique at temperatures of -20° and -40°C and frequencies of 300, 915 and 2450 MHz, These measurements suggest the presence of significant amounts of free water and dissolved ions at low temperatures. Dielectric properties of the frozen meats were generally predicted by a physical-chemical model involving pockets of saturated aqueous sodium chloride suspended in a field of solids and ice at thermodynamic equilibrium.
TL;DR: Unfettered monkeys (Macaca mulatta) have been trained to expose the face and eyes to pulsed microwave radiation at a frequency of 9.31 GHz and an average power density of 150 mW/cm2 and no deleterious effects such as cataracts have been observed.
Abstract: Unfettered monkeys (Macaca mulatta) have been trained to expose the face and eyes to pulsed microwave radiation at a frequency of 9.31 GHz and an average power density of 150 mW/cm2. Performance of an operant response required the monkeys to maintain the head within the field of the radiation source. Twelve monkeys were individually irradiated during 30 to 40 sessions and then were observed for a period of one year. No deleterious effects such as cataracts have been observed.
TL;DR: An improved radiometer is developed, which simultaneously measures temperature and emissivity, independent by of a possible mismatch, and demonstrates the superiority of the new system as compared to conventional ones.
Abstract: In the past, biomedical temperature measurements by microwave radiometry suffered from variable mismatch (emissivity <1) between the specimen under test and the receiving antenna. We have developed an improved radiometer, which simultaneously measures temperature and emissivity, independent by of a possible mismatch. Comparative measurements demonstrate the superiority of the new system as compared to conventional ones.
TL;DR: In this paper, the authors proposed to use directional receiving elements to reduce rectenna costs in free-space microwave power transmission systems, particularly in applications like solar power satellites where the power bea...
Abstract: Directional receiving elements are proposed to reduce rectenna costs in free-space microwave power transmission systems, particularly in applications like solar power satellites where the power bea...
TL;DR: Preliminary results of temperature distribution in volumes of tissue placed between two conformal applicators energized at 2.45 GHz are presented.
Abstract: One of the basic requirements for effective use of hyperthermia in treatment of cancer is the delivery of uniform heat to specific volumes of tissues and maintenance of the optimal temperat...
TL;DR: There is a need for a statistically more significant number of cases, extension towards lower sensing frequencies and experiments on postoperative specimens and phantom models, indicating the depth sensing capabilities of millimeter waves.
Abstract: Thermographic studies of 14 patients with breast carcinoma were performed using two millimeter wave scanners for 30 and 68 GHz. Small correlation with infrared thermograms was observed indicating the depth sensing capabilities of millimeter waves. Correlation with mammographic and other clinical findings was good for tumors with medium subcutaneous depth. These preliminary results indicate a need for a statistically more significant number of cases, extension towards lower sensing frequencies and experiments on postoperative specimens and phantom models.
TL;DR: In this article, the effect of microwave energy on Acacia longifolia seed coat cracks was investigated and a brief comparison was made between seed treatment by microwave and boiling water techniques.
Abstract: Germination of Acacia longifolia was enhanced by microwave energy. Cracks produced on the seed coat are discussed. Special attention is focused on the effect of microwave energy on the strophiole. Possible reasons for strophiolar breakdown are given. A brief comparison is made between seed treatment by microwave and boiling water techniques. The microwave method offers advantages for use with direct seeding.
TL;DR: The results are interpreted as the transient debilitation of behavior produced by the interaction of a mild elevation of ambient temperature and microwave irradiation.
Abstract: Each of twelve male hooded rats was trained to insert its head into a food cup for food pellets on a random-interval schedule of reinforcement. After performance stabilized, the rats were assorted into 3 groups of 4 animals. Groups were matched for response rates. Animals were exposed in groups of 4 for 15.5 h to CW 2450-MHz microwaves once every 6 nights. Animals of each group were exposed to microwaves at only one power density, either 5, 10, or 15 mW/cm2; they were exposed three times at an ambient temperature of 22°C, then three times at 28°C, and then once more at 22°C. The relative humidity was 50% during all exposures. Rats were sham irradiated (at 0 mW/cm2) the night before each microwave exposure. Behavior was tested daily after termination of microwave irradiation of after sham exposures. None of the exposures to microwaves at 22°C altered rates or durations of responding. Exposures at 28°C reduced response rates and increased response durations in direct relation to the power density. T...
TL;DR: A microwave heating system, designed to improve temperature uniformity in heated tissue, is described, which employs parallel-opposed waveguide applicators and improves the microwave coupling and avoids shape and size dependent absorption characteristics of the irregularly shaped tissue.
Abstract: A microwave heating system, designed to improve temperature uniformity in heated tissue, is described. The system employs parallel-opposed waveguide applicators, operating in the TE10 mode at 2450MHz with the tissue to be heated (i.e. mouse intestine) immersed in a liquid which is both biologically compatible with and dielectrically similar to the tissue. The liquid improves the microwave coupling and avoids shape and size dependent absorption characteristics of the irregularly shaped tissue. Also, by maintaining this liquid at a suitable temperature with respect to that required in the tissue, the thermal losses and hence temperature gradients in the tissue are reduced compared with heating in hot liquid alone.
TL;DR: In this paper, a simple method for measurement of the dielectric properties of plant leaves at microwave frequencies is described, and theoretical analysis of the frequency dependence of the reflection coefficient of a sample holder with a sample located at the end of the coaxial line which opens into a circular wave guide operating below cut-off.
Abstract: A simple method for measurement of the dielectric properties of plant leaves at microwave frequencies is described. Theoretical analysis is given of the frequency dependence of the reflection coefficient of a sample holder with a sample located at the end of the coaxial line which opens into a circular wave guide operating below cut-off. Analysis and calculations of the uncertainty in permittivity measurements, as well as experimental results for rape leaves, are presented and the limitation of the method are discussed.
TL;DR: Millimeter wave thermographic studies of neck and head diseases are reported; they yield more diagnostic information about subcutaneous and even intracranial thermal abnormalities than conventional infrared thermography which is limited to cutaneous temperature measurements.
Abstract: Millimeter wave thermographic studies of neck and head diseases are reported; they yield more diagnostic information about subcutaneous and even intracranial thermal abnormalities than conventional infrared thermography which is limited to cutaneous temperature measurements.
TL;DR: In this article, a twin cavity microwave applicator is described for the final drying of foam backed tufted carpets, and the performance of the applicator as part of a conventional system is fully studied in terms of drying foam backed carpets from moisture content values of about 20% down to equilibrium values.
Abstract: A twin cavity microwave applicator is described for the final drying of foam backed tufted carpets. The performance of the twin cavity applicator as part of a conventional system, comprising of a conventional hot air chamber followed by the twin cavity dryer, is fully studied in terms of drying foam backed carpets from moisture content values of about 20% down to equilibrium values. The efficiency of coupling the microwave energy into the cavities, the-applicator efficiency and the ability of moisture levelling are quantitatively established. The economics of incorporating such a microwave resonant dryer, in multiple twin cavity units, as a final dryer in an industrial carpet printing line are considered in terms of increased throughput.
TL;DR: In this paper, a full-size, upright human model was placed in the far-zone of a standard-gain horn inside an absorber-lined chamber to measure microwave heating at a frequency of 1.29 GHz.
Abstract: Measurements of microwave heating were made in a full-size, upright human model. The 75-Kg model, composed of electrically simulated muscle, was placed in the far-zone of a standard-gain horn inside an absorber-lined chamber. Pulsed energy at 1.29 GHz was obtained from a military radar transmitter (AN/TPS-1G) and produced radiation at 6-14 mW/cm2 average power density at the location of the model. Microwave heating at the front surface was measured at nine locations on the phantom. Measurements at several depths within the phantom were also made at a central location to gain information on the depth-of-penetration of the microwave energy. Results of the frontal surface measurements and of the penetration study permitted a calculation of the approximate whole-body average specific absorption rate (SAR) when the model's long axis was parallel to the E-field vector. For a normalized power density of 1 mW/cm2 at a frequency of 1.29 GHz, the whole-body average SAR approximated 0.03 W/Kg. This result agrees well with theoretical predictions based on absorption in prolate spheroidal models of man.