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At least 685 records · Page 38Linked to original sources
PubMed1995

Protocols for precise radio-anatomical positioning of the tibiofemoral and patellofemoral compartments of the knee.

Quantitative assessment of radiographic features, in particular joint space width, are important in the diagnosis and treatment of knee osteoarthritis (OA). Protocols defining radiographic procedures are essential to maintain quality control and hence reliable and reproducible measurement of these features. Criteria governing variability in radiographic procedures are discussed and include defining the precise radio-anatomical position of the joint, standard criteria for X-ray beam alignment, allowance for inherent radiographic magnification and precise definition of anatomical boundaries. Protocols incorporating these criteria are described for standard radiography of the anteroposterior view of the tibiofemoral compartment in the standing semi-flexed position, and for the standing lateral and axial views of the patellofemoral joint. In these views, the radio-anatomical position of the joint is based upon the principal that there is only one plane in which the central ray of the X-ray beam will pass between the margins of the joint space so that both margins and space are optimally defined, in a position consistent with the functional loading of that joint.

Humans↗
PubMed1995

Intracellular distribution of radio-labelled enterotoxigenic Escherichia coli heat-stable toxin (STa) in the intestine of suckling rat.

The chloramine T-procedure was employed to radio-iodinate Escherichia coli heat-stable toxin (STa). The percentage iodination yield was 53.14% with a specific activity of 25.9 microCi/micrograms. Intragastric injections of both labelled and unlabelled toxin administered to suckling rats produced significant increase of fluid accumulation indicating that the biological activity of STa was not lost during radio-iodination. The uptake of the labelled toxin by subcellular particles of the intestinal cells in the suckling rats indicated that the toxin uptake was maximum in mitochondrial-lysosomal fraction. This confirms our previous observation on lysosomal involvement in digestion of the toxin. Results of the study also seem to be consistent with the short-lived hyper-secretory action of the toxin.

Acid Phosphatase↗
PubMed1995

[Venous leakage impotence: anatomical and physiological considerations upon gravity cavernosometry and radio-fluorographic cavernosography].

We performed gravity cavernosometry and radio-fluoro-graphic cavernosography with pharmacological intracavernous injection in 15 patients with erectile dysfunction. On the basis of cavernosographyc findings, in the 15 patients leak sites visualized included deep dorsal vein in all 15 patients leak sites visualized included deep dorsal vein in all 15 patients (100%), cavernous veins in 7 (46,6%), glans in 4 (26,6%) and corpus spongiosum in 3 (20%). Aberrant veins documented in 4 patients (26,6%): communicating with the saphenous vein in 2 (13,3%), with scrotal veins and femoral vein in 1 (6,6%). Deep dorsal vein leakage as the only venous site was find in 2 patients (13.3%), 9 (60%) had leakage through 2 venous sites, 3 (20%) had leakage through 3 venous sites and 1 (6,6%) had leakage through 4 venous sites. Correlations among hemodynamic and radiographic observations allowed the identification of 2 types of cavernosometric findings. While type I developed an high intracavernous pressure during gravity infusion, an high intracavernous pressure was not observed in type 2. The FCG by the digital radio-fluoro-graphic digital system permit the possibility of sottraction and rielaboration of images and reduces examination and radiation time. The gravity FCM is simple, not expensive and respect the physiological intracavernous pressure.

Adult↗
PubMed1976

[Diagnostic traps and procedure to follow in radio-invisible biliary calculi].

Instead of the term biliary microlithiasis, the authors prefer the general concept of radio-invisible biliary lithiasis. The size, the homogeneity, the site and chemical composition of the gall stones, which are the usual criteria of biliary microlithiasis, also are valid for radio-invisibility; thus the diagnostic traps are the only original characteristics of a pathology with hazy outlines, defined as one which escapes well conducted a radiological exploration. Biliary micro-lithiasis therefore raises a triple problem. The indications for biliary surgical exploration, in spite of normal cholangiography, seem to us undoubted in acute relapsing pancreatitis, once the usual medical causes have been eliminated. It should be more relative in pure biliary pain which first requires, not only repeated cholangiography, but also constant clinical and laboratory signs which suggest that the symptoms are organic and that gall stones are in formation. After laparotomy, cholecystectomy is required, not only in perceptible lithiasis, but also when the gall bladder bile contains mud, débris, sand or cholesterol spheroids. In the other cases, the choice between abstention or cholecystectomy depends on the clinical and laboratory context. The surgical attitude with regard to the common bile duct is discussed in three possibilities depending on the case, e.g. routine exploration, abstention or exploration in certain cases.

Acute Disease↗
PubMed1976

[Experience with radio isotope myelography from neurosurgical aspects (author's transl)].

Experience with Radio Isotope Myelography is reported here. 169Yb-DTPA as a tracer was intrathecally injected at lumbar region in twenty three patients with various spinal cord lesions. The first scanning is perfomed after comfirming by gamma-camera that the tracer reaches to the lesion, the second and the third scannings are done according to the ascending rate of the tracer. (I) Normal scintimyelogram (A) In normal case, the shape of the Radio Isotope Myelogram well corresponds the shape of anatomical subarachnoid space. (B) In normal adult cases, the tracer comes up to the cisterna magna in 20-25 minutes after the lumbar injection. Therefore, the scintimyelographic diagnosis should be made not only by the shape but also by the ascending rapidity of the tracer. (II) Abnormal scintimyelogram Abnormal scintimyelograms could be summarized as following three categories. (A) "Delay": It means delay of the ascending of the tracer. Besides, "Transient delay" found in a case of Arnord-Chiari's malformation was proposed. (B) "Partial block": It meas a defect at the level of the lesion. This "Partial block" were observed in cases of spinal cord angioma, cervical spondylosis and spinal cord tumor etc. (C) "Complete block": It means the stagnation of the tracer below the lesion. To sum up, Rario Isotope Myelography, especially in partial block, can more easily and more sensitively represent the maximum extent of the spinal cord lesion than other myelographic study or angiographic one. On the other hand, we can not qualitatively diagnose about the lesions by its indistinct border.

Adolescent↗
PubMed2006

DNA strand breaks are not induced in human cells exposed to 2.1425 GHz band CW and W-CDMA modulated radiofrequency fields allocated to mobile radio base stations.

We conducted a large-scale in vitro study focused on the effects of low level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system in order to test the hypothesis that modulated RF fields may act as a DNA damaging agent. First, we evaluated the responses of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole body SAR for general public exposure defined as a basic restriction in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced different levels of DNA damage. Human glioblastoma A172 cells and normal human IMR-90 fibroblasts from fetal lungs were exposed to mobile communication frequency radiation to investigate whether such exposure produced DNA strand breaks in cell culture. A172 cells were exposed to W-CDMA radiation at SARs of 80, 250, and 800 mW/kg and CW radiation at 80 mW/kg for 2 and 24 h, while IMR-90 cells were exposed to both W-CDMA and CW radiations at a SAR of 80 mW/kg for the same time periods. Under the same RF field exposure conditions, no significant differences in the DNA strand breaks were observed between the test groups exposed to W-CDMA or CW radiation and the sham exposed negative controls, as evaluated immediately after the exposure periods by alkaline comet assays. Our results confirm that low level exposures do not act as a genotoxicant up to a SAR of 800 mW/kg.

Cell Line↗
PubMed1997

Absence of chronic effect of exposure to short-wave radio broadcast signal on salivary melatonin concentrations in dairy cattle.

A pilot study was conducted to investigate the influence of electromagnetic fields in the short-wave range (3-30 MHz) radio transmitter signals on salivary melatonin concentration in dairy cattle. The hypothesis to be tested was whether EMF exposure would lower salivary melatonin concentrations, and whether removal of the EMF source would be followed by higher concentration levels. For this pilot study, a controlled intervention trial was designed. Two commercial dairy herds at two farms were compared, one located at a distance of 500 m (exposed), the other at a distance of 4,000 m (unexposed) from the transmitter. At each farm, five cows were monitored with respect to their salivary melatonin concentrations over a period of ten consecutive days. Saliva samples were collected at two-hour intervals during the dark phase of the night. As an additional intervention, the short-wave transmitter was switched off during three of the ten days (off phase). The samples were analyzed using a radioimmunoassay. The average nightly field strength readings were 21-fold greater on the exposed farm (1.59 mA/m) than on the control farm (0.076 mA/m). The mean values of the two initial nights did not show a statistically significant difference between exposed and unexposed cows. Therefore, a chronic melatonin reduction effect seemed unlikely. However, on the first night of re-exposure after the transmitter had been off for three days, the difference in salivary melatonin concentration between the two farms (3.89 pg/ml, CI: 2.04, 7.41) was statistically significant, indicating a two- to seven-fold increase of melatonin concentration. Thus, a delayed acute effect of EMF on melatonin concentration cannot completely be excluded. However, results should be interpreted with caution and further trials are required in order to confirm the results.

Animals↗
PubMed1964

DEEP BODY TEMPERATURE OF UNTETHERED DOLPHIN RECORDED BY INGESTED RADIO TRANSMITTER.

Information concerning body temperature was recorded by radio transmission from within a dolphin, Tursiops truncatus, swimming freely in a pool. The temperature varied according to the activity of the animal and appeared to oscillate when the dolphin was returned to the pool after a brief period outside it. The transmitter was passed approximately 17 hours after it had been swallowed. A new type of antenna was used with the circuit. The transmitter can be adapted for telemetering heart beat, movement, aquatic animals.

Animals↗
PubMedDate not supplied

[Use of absorbing tongs to measure the output of radio interferences].

Information on the absorbing tongs consisting of two sets of ferrite rings and a wide-band current collector, which are designed to measure the emissive power of radio interferences in the supply circuit and interblock conducting wires at frequencies greater than 30 MHz.

Calibration↗
PubMed2005

FCC to begin issuing licenses for use of mobile radios in the 460 to 470 MHz band.

The U.S. Federal Communications Commission (FCC) has stated that after December 31, 2005, it will begin issuing licenses for use of private land mobile radios (PLMRs) in the 460 to 470 MHz frequency band. Medical telemetry systems operating in this band after December 31 will therefore be at increased risk for interference, which could compromise patient safety. Any medical facility in the vicinity of a PLMR could be affected.

Federal Government↗
PubMed1996

Radio frequency electromagnetic exposure: tutorial review on experimental dosimetry.

Radio frequency (RF) dosimetry is the quantification of the magnitude and distribution of absorbed electromagnetic energy within biological objects that are exposed to RF fields. At RF, the dosimetric quantity, which is called the specific absorption rate (SAR), is defined as the rate at which energy is absorbed per unit mass. The SAR is determined not only by the incident electromagnetic waves but also by the electrical and geometric characteristics of the irradiated subject and nearby objects. It is related to the internal electric field strength (E) as well as to the electric conductivity and the density of tissues; therefore, it is a suitable dosimetric parameter, even when a mechanism is determined to be "athermal." SAR distributions are usually determined from measurements in human models, in animal tissues, or from calculations. This tutorial describes experimental techniques that are used commonly to determine SAR distributions along with the SAR limitations and unresolved problems. The methods discussed to obtain point, planar, or whole-body averaged SARs include the use of small E-field probes or measurement of initial rate of temperature rise in an irradiated object.

Animals↗
PubMed1998

Thermophysiological responses of human volunteers during controlled whole-body radio frequency exposure at 450 MHz.

Thermoregulatory responses of heat production and heat loss were measured in seven adult volunteers (four women and three men, aged 21-57 yr) during 45-min dorsal exposures of the whole body to 450 MHz continuous wave radio frequency (RF) fields. Two power densities (PD) (local peak PD = 18 and 24 mW/cm2; local peak specific absorption rate = 0.320 [W/kg]/[mW/cm2]) were tested in each of three ambient temperatures (Ta = 24, 28, and 31 degrees C) plus Ta controls (no RF). No changes in metabolic heat production occurred under any exposure conditions. Vigorous increases in sweating rate on back and chest, directly related to both Ta and PD, cooled the skin and ensured efficient regulation of the deep body (esophageal) temperature to within 0.1 degrees C of the normal level. Category judgments of thermal sensation, comfort, sweating, and thermal preference usually matched the measured changes in physiological responses. Some subtle effects related to gender were noted that confirm classic physiological data. Our results indicate that dorsal exposures of humans to a supraresonant frequency of 450 MHz at local peak specific absorption rates up to 7.68 W/kg are mildly thermogenic and are counteracted efficiently by normal thermophysiologic heat loss mechanisms, principally sweating.

Adult↗
PubMed1999

Human exposure at two radio frequencies (450 and 2450 MHz): similarities and differences in physiological response.

Thermoregulatory responses of heat production and heat loss were measured in two different groups of seven adult volunteers (males and females) during 45-min dorsal exposures of the whole body to 450 or 2450 MHz continuous-wave radio frequency (RF) fields. At each frequency, two power densities (PD) were tested at each of three ambient temperatures (T(a) = 24, 28, and 31 degrees C) plus T(a) controls (no RF). The normalized peak surface specific absorption rate (SAR), measured at the location of the subject's center back, was the same for comparable PD at both frequencies, i.e., peak surface SAR = 6.0 and 7.7 W/kg. No change in metabolic heat production occurred under any exposure conditions at either frequency. The magnitude of increase in those skin temperatures under direct irradiation was directly related to frequency, but local sweating rates on back and chest were related more to T(a) and SAR. Both efficient sweating and increased local skin blood flow contributed to the regulation of the deep body (esophageal) temperature to within 0.1 degrees C of the baseline level. At both frequencies, normalized peak SARs in excess of ANSI/IEEE C95.1 guidelines were easily counteracted by normal thermophysiological mechanisms. The observed frequency-related response differences agree with classical data concerning the control of heat loss mechanisms in human beings. However, more practical dosimetry than is currently available will be necessary to evaluate realistic human exposures to RF energy in the natural environment.

Absorption↗
PubMed1999

Luminescent radio frequency radiation dosimetry.

Thermoluminescent dosimetry has been the industry standard for ionizing radiation dosimetry because it is inexpensive, sensitive, and accurate. No such system exists for radio frequency radiation. This paper describes the state of the art of efforts toward developing such a system. Thermochemiluminescent (TCL) dosimetry, first reported in 1991, is a first step toward achieving this goal. However, it has had problems in the production of TCL materials and in conversion of the luminescent signal into specific absorption rate (SAR). The former problem has been solved by the development of a genetically engineered Escherichia coli bacterium (JM 109/plC20RNR1.1), described herein, that produces the TCL material in a fermentation process. The latter problem stems from the difficulty in determining the structure of the currently best TCL material diazoluminomelanin. A theoretical approach for the solution of this problem has been achieved by combining equations for delayed fluorescence, temperature determination by TCL, and the free energy equation for equilibrium reactions. It has led to an explanation for the stable display of steady-state energy disposition, illustrated by TCL, in phantoms without the expected disruption by thermal conduction or convection, at frequencies ranging from 2.06 GHz to 35 GHz.

Absorption↗
PubMed1999

Membrane potential and currents of isolated heart muscle cells exposed to pulsed radio frequency fields.

The influence of radio frequency (RF) fields of 180, 900, and 1800 MHz on the membrane potential, action potential, L-type Ca(2+) current and potassium currents of isolated ventricular myocytes was tested. The study is based on 90 guinea-pig myocytes and 20 rat myocytes. The fields were applied in rectangular waveguides (1800 MHz at 80, 480, 600, 720, or 880 mW/kg and 900 MHz, 250 mW/kg) or in a TEM-cell (180 MHz, 80 mW/kg and 900 MHz, 15 mW/kg). Fields of 1800 and 900 MHz were pulsed according to the GSM-standard of cellular phones. The specific absorption rates were determined from computer simulations of the electromagnetic fields inside the exposure devices by considering the structure of the physiological test arrangement. The electrical membrane parameters were measured by whole cell patch-clamp. None of the tested electrophysiological parameters was changed significantly by exposure to RF fields. Another physical stimulus, lowering the temperature from 36 degrees C to 24 degrees C, decreased the current amplitude almost 50% and shifted the voltage dependence of the steady state activation parameter d(infinity) and inactivation parameter f(infinity) of L-type Ca(2+) current by about 5 mV. However, at this lower temperature RF effects (900 MHz, 250 mW/kg; 1800 MHz, 480 mW/kg) on L-type Ca(2+) current were also not detected.

Action Potentials↗
PubMed2000

Radio frequency transmyocardial revascularization enhances angiogenesis and causes myocardial denervation in canine model.

BACKGROUND AND OBJECTIVE: Transmyocardial revascularization (TMR) relieves angina and improves exercise tolerance in patients. Angiogenesis and myocardial denervation have been proposed as factors contributing to these benefits. To test whether radio frequency transmyocardial revascularization (RF-TMR) enhances angiogenesis and causes myocardial denervation. STUDY DESIGN/MATERIALS AND METHODS: RF-TMR channels were created in 12 dogs which survived up to 4 weeks. Bromodeoxyuridine was administered subcutaneously to mark proliferating cells as an assay of angiogenesis. Western blot analysis of tyrosine hydroxylase and blood pressure response to topical bradykinin were used as indices of myocardial denervation. RESULTS: RF-TMR increased local vascularity by an average of 50%, whereas the rate of vascular cell proliferation was tripled over that of the untreated region. Changes in mean arterial pressure with bradykinin and tyrosine hydroxylase content were significantly decreased in RF-TMR regions as compared with normal myocardium in the same hearts. CONCLUSION: RF-TMR enhances angiogenesis and causes myocardial denervation in canine myocardium as with laser TMR.

Animals↗
PubMed2000

Radial stratification of ions as a function of mass to charge ratio in collisional cooling radio frequency multipoles used as ion guides or ion traps.

Collisional cooling in radio frequency (RF) ion guides has been used in mass spectrometry as an intermediate step during the transport of ions from high pressure regions of an ion source into high vacuum regions of a mass analyzer. Such collisional cooling devices are also increasingly used as 'linear', two-dimensional (2D) ion traps for ion storage and accumulation to achieve improved sensitivity and dynamic range. We have used the effective potential approach to study m/z dependent distribution of ions in the devices. Relationships obtained for the ideal 2D multipole demonstrate that after cooling the ion cloud forms concentric cylindrical layers, each of them composed of ions having the same m/z ratio; the higher the m/z, the larger is the radial position occupied by the ions. This behavior results from the fact that the effective RF focusing is stronger for ions of lower m/z, pushing these ions closer to the axis. Radial boundaries of the layers are more distinct for multiply charged ions, compared to singly charged ions having the same m/z and charge density. In the case of sufficiently high ion density and low ion kinetic energy, we show that each m/z layer is separated from its nearest neighbor by a radial gap of low ion density. The radial gaps of low ion population between the layers are formed due to the space charge repulsion. Conditions for establishing the m/z stratified structure include sufficiently high charge density and adequate collisional relaxation. These conditions are likely to occur in collisional RF multipoles operated as ion guides or 2D ion traps for external ion accumulation. When linear ion density increases, the maximum ion cloud radius also increases, and outer layers of high m/z ions approach the multipole rods and may be ejected. This 'overfilling' of the multipole capacity results in a strong discrimination against high m/z ions. A relationship is reported for the maximum linear ion density of a multipole that is not overfilled.

Algorithms↗
PubMed2006

Interaction of radio frequency electromagnetic fields and passive metallic implants--a brief review.

During the last decade, use of radio frequency (RF) applications like mobile phones and other wireless devices, has increased remarkably. This has triggered numerous studies related to possible health risks due to the exposure of RF electromagnetic (EM) fields. One safety aspect is the coupling of EM fields with active and passive implants in the human body. While interactions with active implants have been quite extensively researched, only a few studies have focused on passive implants. The present article reviews interaction mechanisms and studies of passive metallic, that is, conductive, implants in common external RF EM fields. It is found that implants have been mostly studied numerically, and experimental studies are rare. Furthermore, the studies cover mostly far-field conditions and only a few have studied implants in near fields. A summary of results indicates that a conductive object in tissues may cause notable local enhancement of the EM field and thus enhanced power absorption. The degree of enhancement depends, for example, on the orientation, the dimensions, the shape, and the location of the implant. However, in most of the cases, the field enhancement has not been strong enough to cause remarkable excess heating (more than 1 degrees C) of tissues.

Absorption↗