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PubMedDate not supplied

Cytogenetic consequences of microwave irradiation on mammalian cells incubated in vitro.

A 2450 MHz microwave oven was converted into a microwave incubator. Rat kangaroo RH5 and RH16 cells were incubated in the incubator and were subcultured every 5 to 7 days. The temperature of the cell cultures in the incubator was maintained at 37 degrees C. The cells were incubated with direct microwave irradiation continuously for 50 passages and then returned to a conventional incubator and allowed to grow for another 30 passages. Cell growth rate was significantly reduced after 7 or 15 subculture passages under irradiation. Chromosome aberrations emerged after the cells had been microwave-incubated for about 20 passages. The long-term irradiation caused 0.84 chromosome breaks per cell in RH5 cell cultures and 0.10 breaks per cell in RH16 cell cultures. After the cell cultures had been returned to the conventional incubator and maintained for 30 passages, the number of chromosomes breaks was greatly reduced in both cell cultures. The number of polyploid cells was increased to 35 percent and 31 percent during the irradiation, and was significantly reduced in the conventional incubator. Many RH5 cells lost one chromosome and became 10-chromosome cells. The number of 10-chromosome cells increased during irradiation and continued to increase after being returned to the conventional incubator.

Animals↗

PubMed1996

Microwave thermoradiotherapy for intraocular melanoma.

We evaluated the use of microwave hyperthermia as an adjuvant to ophthalmic plaque radiotherapy for patients with intraocular tumors. Forty-eight patients were offered combined microwave plaque thermoradiotherapy (TRT) as a primary treatment for their uveal melanomas. A dish-shaped microwave antenna was placed on the sclera beneath the tumor at the time of plaque brachytherapy. While temperatures were measured at the sclera, the tumor's apex was targeted to receive a minimum of 42 degrees C for a 45-min duration. Patients were also given full or reduced doses of plaque radiotherapy (125I or 103Pd). We reduced the minimum tumor radiation dose (apex dose) for 42 (88%) of our patients to <70 Gy (mean, 52.5 Gy). The 48 TRT patients were followed for < or =8 years (average, 45 months). To date, there has been one documented postoperative tumor enlargement, for a 97.2% local control rate. Two patients were lost to follow-up. Four eyes have been enucleated: two due to neovascular glaucoma, one to glaucoma secondary to intraocular inflammation, and one for progressive tumor enlargement. Although 13 patients have died, only four deaths were due to metastatic melanoma. Thirty-five patients (73%) have maintained within two lines or had better than their preoperative visual acuity. Side effects attributable to heating included chorioretinal scar formation within and around the targeted zone and decreased intraocular pressures without hypotony. Our experience with this heat delivery system suggests that adjuvant microwave thermotherapy can be used with plaque radiotherapy for the treatment of uveal melanoma.

Humans↗

PubMed2004

Ocular surface injury from a microwave superheated liquid.

PURPOSE: To describe the ocular surface injury resulting from a microwave superheated liquid. METHODS: Case report. RESULTS: A 40-year-old man sustained an ocular surface injury from a microwave superheated liquid. The injury resulted in limbal stem cell damage requiring an autograft limbal stem cell transplantation. CONCLUSIONS: We are unaware of previous reports of microwave superheated liquids resulting in ocular injury. Microwave superheating of liquids is a potential ocular danger that should be brought to the attention of both ophthalmologists and their patients.

Adult↗

PubMed1996

Three-year followup of patients treated with lower energy microwave thermotherapy.

PURPOSE: A retrospective study was done to investigate the long-term outcome of patients treated with lower energy transurethral microwave thermotherapy. MATERIALS AND METHODS: A total of 305 patients with lower urinary tract symptoms and benign prostatic hypertrophy underwent transurethral microwave thermotherapy according to a similar protocol at 2 centers. RESULTS: After 3 years of followup 133 patients who had undergone transurethral microwave thermotherapy alone were available for study. During this observation period significant symptomatic improvement from baseline and an improved maximum flow rate of 2.6 ml. per second were noted. Of the patients 125 underwent invasive or medical treatment. CONCLUSIONS: After 3 years of followup lower energy transurethral microwave thermotherapy showed significant and durable improvements in baseline parameters in 52% of the patients.

Aged↗

PubMed1998

Intraprostatic temperature monitoring during transurethral microwave thermotherapy for the treatment of benign prostatic hyperplasia.

PURPOSE: We evaluated whether the results of transurethral microwave thermotherapy improve using high intraprostatic temperatures of 55C or greater. MATERIALS AND METHODS: We accrued 30 men 58 to 85 years old (mean age 69) from the waiting list for transurethral prostatic resection in whom maximum urinary flow was less than 13 ml. per second and Madsen score was greater than 8. According to the Abrams-Griffith nomogram all but 1 patient had obstruction. Before treatment 3 thin temperature probes, each containing 5 sensors in a row, were introduced into the prostate from the perineum and positioned using transurethral ultrasound guidance. The microwave power of the transurethral microwave thermotherapy equipment was set based on the actual temperature in the prostatic tissue. A temperature of at least 55C and often more than 60C was reached at the hottest spot. Treatment duration was 1 hour. Postoperatively an indwelling catheter remained in place for 2 weeks. Patients were followed for 6 months with the first followup after 3 months. RESULTS: At the 3-month followup mean maximum urinary flow had increased from 7.4 to 12.5 ml. per second and the mean Madsen score had decreased from 12.6 to 2.9. At the 6-month followup mean maximum urinary flow was 12.2 ml. per second and the mean Madsen score was 3.4. Using pressure-flow data we divided the patients into responders and nonresponders. In the 18 responders maximum urinary flow had increased from 7.2 to 14.6 ml. per second (103%), the Madsen score had decreased from 12.5 to 1.4 (89%) and detrusor pressure had decreased from 9.2 to 6 kPa. (35%). CONCLUSIONS: High energy transurethral microwave thermotherapy relieved bladder outlet obstruction in 60% of the patients and had a good effect on symptoms. Compared with a previous multicenter study with 40% responders, using the same criteria there were 60% responders in our series. Our results indicate that better control of intraprostatic temperature provides better results, approaching those after transurethral prostatic resection.

Aged↗

PubMed2001

Microwave decalcification of human temporal bones.

OBJECTIVES/HYPOTHESIS: Morphological and immunohistochemical studies of human temporal bones are challenging as a result of difficulties in obtaining reliably fixed specimens and the lengthy time required for decalcification, typically 4 to 7 months. A novel method of processing human temporal bones using a microwave oven to accelerate decalcification is described. This procedure provides a rapid means of decalcifying temporal bones with good preservation of tissue morphology and antigenicity. METHODS: Human temporal bone specimens obtained at autopsy (n = 12, from specimens aged 43-91 y) were fixed within 6.5 hours of death by transtympanic perilymphatic perfusion of the inner ear. Decalcification was carried out using ethylenediaminetetra-acetic acid (EDTA) in a microwave oven and required only 3 to 6 weeks. Specimens were then dehydrated, embedded in paraffin, sectioned, and mounted on slides for morphological and immunohistochemical evaluation. RESULTS: Microscopic examination revealed no obvious artifacts attributable to the microwave decalcification process. The quality of morphological preservation was largely dependent on the postmortem fixation interval and adequacy of perilymphatic perfusion. Immunohistochemical analysis demonstrated strong positive staining for the enzyme Na,K-ATPase, an integral membrane protein. CONCLUSIONS: This study demonstrates that microwave decalcification provides an efficient and reliable means of processing human temporal bones for histological and histochemical examination. Decalcification time is significantly reduced with no apparent adverse effects on structural preservation or antigenicity.

Adult↗

PubMed1993

A phantom system for microwave treatment of intraocular tumors.

A gel-block system was developed to illustrate heating patterns induced by ophthalmic microwave applicators. A heat-sensitive liquid crystal card was affixed as to bisect a Lucite box. The box was then filled with a clear tissue equivalent polyacrylamide gel. It was found that semicircular heating patterns were generated within the gel. These patterns were visualized by placing one of the dish-shaped ophthalmic microwave applicators on top of the polyacrylamide gel and the heat-sensitive liquid crystal card. An antenna was then placed in the gel and behind the card. Microwave energy was sent through the card and into the gel. This demonstrated the relatively homogeneous and roughly circular heating pattern produced at the applicator's surface. A combination of these profiles led to construction of a three-dimensional, dome-shaped model of heating, as provided by this microwave antenna design.

Acrylic Resins↗

PubMed2005

Ocular surface injury from a microwave superheated egg resulting in a pseudopterygium.

PURPOSE: To describe the first case of ocular surface injury resulting in a pseudopterygium from a microwave superheated egg. METHODS: Case report. RESULTS: A 12-year-old girl sustained an ocular surface injury resulting in a pseudopterygium from a microwave superheated egg. CONCLUSION: Microwave superheated eggs can result in ocular injury. This case illustrates the potential ocular danger involved with microwave ovens.

Blast Injuries↗

PubMed1996

Microwave tomography: two-dimensional system for biological imaging.

Microwave tomographic imaging is one of the new technologies which has the potential for important applications in medicine. Microwave tomographically reconstructed images may potentially provide information about the physiological state of tissue as well as the anatomical structure of an organ. A two-dimensional (2-D) prototype of a quasi real-time microwave tomographic system was constructed. It was utilized to reconstruct images of physiologically active biological tissues such as an explanted canine perfused heart. The tomographic system consisted of 64 special antennae, divided into 32 emitters and 32 receivers which were electronically scanned. The cylindrical microwave chamber had an internal diameter of 360 mm and was filled with various solutions, including deionized water. The system operated on a frequency of 2.45 GHz. The polarization of the incident electromagnetic field was linear in the vertical direction. Total acquisition time was less than 500 ms. Both accurate and approximation methods of image reconstruction were used. Images of 2-D phantoms, canine hearts, and beating canine hearts have been achieved. In the worst-case situation when the 2-D diffraction model was used for an attempt to "slice" three-dimensional (3-D) object reconstruction, we still achieved spatial resolution of 1 to 2 cm and contrast resolution of 5%.

Animals↗

PubMed2001

Computational modeling of three-dimensional microwave tomography of breast cancer.

Microwave tomographic approach is proposed to detect and image breast cancers. Taking into account the big difference in dielectrical properties between normal and malignant tissues, we have proposed using the microwave tomographic method to image a human breast. Because of the anatomical features of the objects, this case has to be referred to the tomography with a limited angle of observation. As a result of computer experiments we have established that multiview cylindrical configurations are able to provide microwave tomograms of the breast with a small size tumor inside. Using the gradient method, we have developed a computer code to create images of the three-dimensional objects in dielectrical properties on microwave frequencies.

Algorithms↗

PubMed2002

Three-dimensional microwave tomography: initial experimental imaging of animals.

The purpose of this study was to construct a microwave tomographic system capable of conducting experiments with whole scale biological objects and to demonstrate the feasibility of microwave tomography for imaging such objects using a canine model. Experiments were conducted using a three-dimensional (3-D) microwave tomographic system with working chamber dimensions of 120 cm in diameter and 135 cm in height. The operating frequency was 0.9 GHz. The object under study was located in the central area of the tomographic chamber filled with a salt solution. Experimentally measured attenuation of the electromagnetic field through the thorax was about -120 dB. To obtain images, we used various two-dimensional and 3-D reconstruction schemes. Images of the canine were obtained. In spite of imperfections, the images represent a significant milestone in the development of microwave tomography for whole body imaging and demonstrate its feasibility.

Animals↗

PubMed2004

Comparison of conventional and microwave-assisted processing of mouse retinas for transmission electron microscopy.

Conventional fixation and processing of mammalian retinal tissues for transmission electron microscopic (TEM) examination is slow and produces ultrastructural artefacts in the photoreceptor cell layer. Among these artefacts are gaps between photoreceptor outer segment disc membranes and between photoreceptor cells in the region of the retina where the cell nuclei are located. A study was undertaken to determine whether a much more rapid microwave-assisted fixation and processing protocol would have an effect on the quality of ultrastructural preservation of the retina, particularly on the photoreceptor cell artefacts. The overall ultrastructural preservation of the retina was similar for the conventional and microwave-assisted techniques. However, the magnitudes of the photoreceptor artefacts were significantly reduced when microwave irradiation was used during primary fixation and processing. It is clear that, at least for the retina, employing microwave irradiation during specimen preparation for TEM results in superior ultrastructural preservation with a substantial reduction in the time required for sample preparation.

Animals↗

PubMed1991

Thermal inactivation of Listeria monocytogenes during a process simulating temperatures achieved during microwave heating.

Conventional heating was used to expose cells of Listeria monocytogenes, either in broth or in situ on chicken skin, to the mean times and temperatures that are achieved during a 28 min period of microwave cooking of a whole chicken. Heating L. monocytogenes by this method in culture broth resulted in a reduction in viable cell numbers by a factor of greater than 10(6) upon reaching 70 degrees C. Simulated microwave cooking of L. monocytogenes in situ, on chicken skin, resulted in more variability in the numbers of survivors. Heating for the full cook time of 28 min, however, resulted in a mean measured temperature of 85 degrees C and no surviving listerias were detected. This indicated a reduction in viable numbers of greater than 10(6). To reduce temperature variation, cells were heated on skin in a submerged system in which exposure to 70 degrees C for 2 min resulted in a reduction in viable cell numbers of all strains of listerias tested of between 10(6) and 10(8). These results show that when a temperature of 70 degrees C is reached and maintained for at least 2 min throughout a food there is a substantial reduction in the numbers of L. monocytogenes. The survival of this organism during microwave heating when temperatures of over 70 degrees C are reported is probably due to uneven heating by microwave ovens resulting in the presence of cold spots in the product. The heat resistance of L. monocytogenes is comparable with that of many other non-sporing mesophilic bacteria.

Animals↗

PubMed1986

The application of a microwave technique for the preparation of cell blocks from sputum.

Microwaves stimulate diffusion in tissue and affect the proteins and membrane of the cell. These actions can be used to shorten the time required to fix and prepare cell blocks from sputum. The fixative containing ethyl alcohol and polyethylene glycol is particularly suitable for microwave enhanced fixation. Applying a commercially available domestic microwave oven, in which the temperature and power level can be set, cell blocks can be prepared from fresh sputum in 35 min. The microscopical results are of a superior quality because of the microwave-induced homogeneous distribution of the effects of the applied immersion fluids on the cells. The method is very successful for all specimens containing a large amount of mucous. Health hazards for laboratory personnel are nil in this cell blocking method; in contrast to when fresh sputum containing infectious agents is used for smear preparation.

Carcinoma, Squamous Cell↗

PubMed1990

Microwaves for microscopy.

Sample preparation for microscopy is based on physical and chemical processes. These processes can be influenced by microwave irradiation. The prerequisite for the development of good microwave procedures is knowledge of histochemistry combined with understanding of the physics of microwave irradiation. Examples of superior results of fixation, processing, and (immuno) staining performed in the microwave oven are presented, both for light- and electron microscopy.

Animals↗

PubMed1994

Processing dentures using a microwave technique.

In this research the technique of curing denture base acrylic resins by microwave energy was investigated with respect to polymerization method, hardness, mechanical and physical properties. Twenty-one different polymerization methods were used by varying radiation power and curing time. The Vickers hardness test was applied to the samples which were polymerized. The average value was found to be 22.46 VHN (Vicker hardness number), that is, almost the same as conventionally cured acrylic. The recommended polymerization method of curing acrylic was 3 min at 550 W in a microwave oven. Mechanical and physical tests were applied to the samples which were cured by the recommended polymerization method. The average transverse load to fracture value was found to be 7.6 kg, and the transverse deflection value was 1.5 mm at 3500 g, and 2.9 mm at 5000 g. Water sorption of acrylic resin cured by microwave energy was 0.72 mg cm-2 and the solubility rate in water was 0.038 mg cm-2. Results conformed with the ADA specification. The findings showed that acrylic resin cured by microwave energy is more resistant to mechanical failure than conventionally cured acrylic and this technique can safely be applied to the production of denture bases.

Acrylic Resins↗

PubMed1995

Detection with the polymerase chain reaction of human papillomavirus DNA in condylomata acuminata treated with CO2 laser and microwave.

BACKGROUND: The recurrence rates of condyloma acuminata are high. The reasons for the relatively high relapse rates with different treatments are unknown. METHODS: Twelve specimens of condylomata acuminata of the vulva were excised from 12 patients and divided into three parts. One part was untreated, the second and the third parts were treated with CO2 laser and microwave, respectively. DNA was then extracted from tissue by proteolytic digestion and amplified by the polymerase chain reaction. Dot blots were performed with the use of radiolabeled consensus and human papilloma virus (HPV) type-specific probes. RESULTS: HPV DNA was amplified in 100% of untreated specimens (6-HPV 6; 6-HPV 11), and in 83.3% and 50% of specimens treated with CO2 laser and microwave, respectively. There was a significant difference in detection between untreated and microwave-treated specimens (chi 2 = 4.18, P < 0.05). CONCLUSION: Microwave damages HPV DNA more effectively than CO2 laser.

Carbon Dioxide↗

PubMed1994

Experimental study of microwave coagulation of a VX-2 carcinoma implanted in rabbit kidney.

This paper describes the results of an experimental study of the microwave coagulation of VX-2 renal tumors implanted in rabbits. The rabbits undergoing microwave treatment exhibited a satisfactory survival rate and a complete response to treatment, as verified by histological examination. All the rabbits receiving no treatment died within 6 weeks of implantation of the VX-2 carcinoma. These results indicate that microwave coagulation may be a curative method of treatment for a relatively small renal tumor. Intraoperative real-time ultrasonic scanning permits the percutaneous microwave coagulation of renal cancer in a clinical situation.

Animals↗