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PubMed1994

Body temperatures of lambs and their mothers measured by radio-telemetry during parturition.

Using temperature-sensitive radio-telemeters chronically implanted in the abdomens of 8 fetal lambs and their mothers, we measured body temperature changes induced by parturition. Maternal body temperature rose at 0.70 +/- 0.06 degrees C/hour (mean +/- SEM) in the final stages of labour. Fetal body temperature also rose, but at a significantly lower rate, 0.45 +/- 0.06 degrees C/hour (p < 0.05). The fetus appears to be protected from excessive hyperthermia during the birth process.

Abdomen↗

PubMed1994

Radio-frequency ring applicator: energy distributions measured in the CDRH phantom.

SAR distributions were measured in the CDRH phantom, a 1 cm fat-equivalent shell filled with an abdomen-equivalent liquid (sigma = 0.4-1.0 S m-1; dimensions 22 x 32 x 57 cm) to demonstrate the feasibility of the ring applicator to obtain deep heating. The ring electrodes were fixed in a PVC tube; diameter 48 cm, ring width 20 cm and gap width between both rings 31.6 cm. Radio-frequency energy was fed to the electrodes at eight points. The medium between the electrodes and the phantom was deionised water. The SAR distribution in the liquid tissue volume was obtained by a scanning E-field probe measuring the E-field in all three directions. With equal amplitude and phase applied to all feeding points, a uniform SAR distribution was measured in the central cross-section at 30 MHz. With RF energy supplied to only four adjacent feeding points (others were connected to a 50 omega load), the feasibility to perform amplitude steering was demonstrated; SAR values above 50% of the maximum SAR were measured in one quadrant only. SAR distributions obtained at 70 MHz showed an improved focusing ability; a maximum at the centre exists for an electric conductivity of the abdomen-equivalent tissue of 0.6 and 0.4 S m-1.

Electromagnetic Fields↗

PubMed2006

Role of 99mTc-sestamibi SPECT in accurate selection of primary hyperparathyroid patients for minimally invasive radio-guided surgery.

PURPOSE: A prerequisite for optimum minimally invasive radio-guided surgery (MIRS) for primary hyperparathyroidism (PHPT) is the demonstration of significant uptake of (99m)Tc-sestamibi in a parathyroid adenoma (PA). The aim of this study was to evaluate the clinical role or (99m)Tc-sestamibi SPECT in selecting patients for this procedure. METHODS: Fifty-four consecutive PHPT patients were evaluated by single-session (99m)Tc-pertechnetate/(99m)Tc-sestamibi planar subtraction scintigraphy, followed by (99m)Tc-sestamibi SPECT acquisition to localise hyperfunctioning PAs and assist in planning the surgical approach. RESULTS: Scintigraphy showed the presence of a solitary PA in 47/54 patients (87%) and two or more PAs in four patients (7.4%); it was negative in the remaining three patients (5.6%). The overall sensitivity of (99m)Tc-sestamibi scintigraphy was 94.6%. In 7/54 patients, the PA was located deep in the para-oesophageal/paratracheal space. So far, 22 patients with scintigraphic evidence of a solitary PA (in four of whom the PA was located deep in the neck) have undergone successful MIRS using the low 37 MBq (1 mCi) (99m)Tc-sestamibi dose protocol. Intraoperative quick parathyroid hormone (QPTH) assay demonstrated a fall in all 22 patients, thus confirming successful removal of the hyperfunctioning PA. No major surgical complications were observed. After a period of follow-up ranging between 6 and 27 months (median 13 months), no case of persistent/recurrent PHPT was recorded. When comparing the parathyroid to background (P/B) ratio measured at planar and SPECT preoperative scintigraphy with that measured intraoperatively with the gamma probe, a good linear correlation was found between the SPECT and the intraoperative gamma probe measurements (r=0.89; p<0.01) but no correlation was found with planar scintigraphic data. CONCLUSION: Our preliminary data suggest that measurement of the P/B ratio by means of (99m)Tc-sestamibi SPECT is more accurate in predicting the intraoperative measurements with the gamma probe. In this respect, a preoperative (99m)Tc-sestamibi SPECT acquisition should be recommended for better selection of PHPT patients in whom a MIRS approach can be offered.

Adenoma↗

PubMed2005

Self-assembled three dimensional radio frequency (RF) shielded containers for cell encapsulation.

This paper describes the construction of three dimensional (3D) encapsulation devices in large numbers, using a novel self-assembling strategy characterized by high mechanical stability, controlled porosity, extreme miniaturization, high reproducibility and the possibility of integrating sensing and actuating electromechanical modules. We demonstrated encapsulation of microbeads and cells within the containers, thereby demonstrating one possible application in cell encapsulation therapy. Magnetic resonance (MR) images of the containers in fluidic media suggest radio frequency (RF) shielding and a susceptibility effect, providing characteristic hypointensity within the container, thereby allowing the containers to be easily detected. This demonstration is the first step toward the design of 3D, micropatterned, non-invasively trackable, encapsulation devices.

Animals↗

PubMed2006

Ethical considerations and proposed guidelines for the use of radio frequency identification: especially concerning its use for promoting public safety and national security.

Radio Frequency Identification (RFID) is quickly growing in its applications. A variety of uses for the technology are beginning to be developed, including chips which can be used in identification cards, in individual items, and for human applications, allowing a chip to be embedded under the skin. Such chips could provide numerous benefits ranging from day-to-day convenience to the increased ability of the federal government to adequately ensure the safety of its citizens. However, there are also valid concerns about the potential of this technology to infringe on privacy, creating fears of a surveillance society. These are concerns that must be addressed quickly, with sensitivity to individual interests and societal welfare, allowing humanity to reap the benefits of convenience and safety without paying an unacceptable price in the loss of privacy.

Federal Government↗

PubMed1989

Radio-frequency catheter ablation of cardiac arrhythmias: appraisal of an evolving therapeutic modality.

Since its introduction in 1985, there have been numerous reports of the use of radio-frequency (RF) current as an alternative energy source for catheter ablation. RF current (frequency range 150 kHz to 1 MHz), when delivered in bipolar mode, causes desiccation of tissue by creating a localized area of heat that results in discrete coagulation necrosis. An equivalent energy source such as direct current (DC) shock can be delivered at lower power (5 to 30 W) and lower voltage (30 to 80 V) for a longer pulse duration (10 to 60 seconds), thus eliminating barotraumatic effects. Because of its high frequency, RF current does not stimulate neuromuscular fibers, and general anesthesia during ablation is not needed. Studies in animals have shown that catheter-delivered RF energy can safely produce permanent complete or partial AV block, necrosis of atrial and ventricular myocardium adjacent to the mitral and tricuspid anuli potentially suitable for ablation of accessory pathways, and discrete lesions in the left and right ventricular myocardium. Recently, investigators from several centers have reported successful ablation of the AV junction (either complete or partial AV block) in patients with refractory supraventricular tachyarrhythmias, ablation of accessory pathways, and ablation of focal ventricular myocardium or a segment of a bundle branch in patients with drug-resistant ventricular tachycardia. Specific modification of AV conduction to cure AV nodal reentrant tachycardia has been successfully attempted. In all studies the application of RF current has not caused any serious complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1978

Self-initiated conversion of paroxysmal atrial flutter utilizing a radio-frequency pacemaker.

A patient is described with drug-resistant recurrent paroxysmal atrial flutter. Electrophysiologic studies demonstrated that flutter was inducible with rapid atrial stimulation (stimulation rates of 375 to 400/min) and convertible with rapid atrial stimulation (rates of 400 to 460/min). Because of the latter response, a radio-frequency atrial pacemaker was implanted, which allowed self-initiated conversion of flutter episodes with rapid stimulation.

Arrhythmias, Cardiac↗

PubMed1983

In vivo desensitization of a severe driving phobia through radio contact with telemonitoring of neurophysiological reactions.

A 34 year-old man with a severe driving phobia was treated by in vivo desensitization. A radio transceiver was used to provide the anxiety inhibiting effects of voice contact during exposure to phobic driving experiences. Transceivers were linked to a Telemonitor apparatus programmed to broadcast heartbeat and GSR readings automatically every 15 minutes or on demand, each of 10 seconds duration. The therapist was therefore in touch with the subjective and physiological arousal of the patient from distances up to 7 miles. This allowed him to conduct more efficiently a program of in vivo graduated exposure. Treatment effects were maintained at a 9-month follow-up.

Adult↗

PubMed1993

Effect of amplitude-modulated radio frequency radiation on cholinergic system of developing rats.

We examined the effect of long-term exposure to radio frequency radiation 147 MHz and its sub-harmonics 73.5 and 36.75 MHz amplitude modulated at 16 and 76 Hz (30-35 days, 3 h per day) on cholinergic systems in developing rat brain. A significant decrease in acetylcholine esterase activity was found in exposed rats as compared to the control. Decrease in acetylcholine esterase (AChE) activity was independent of carrier wave frequencies. A short-term exposure did not have any significant effect on AChE activity.

Acetylcholinesterase↗

PubMed1983

Stimulation of bone union by externally applied radio-frequency energy.

Pulsed radio-frequency electrical energy has been used for many years in the treatment of various soft tissue lesions, and this paper describes its use in stimulating repair in delayed and non-union, with a success rate in 16 cases equal to that of the other electrical stimulation techniques. The equipment is described and a theory proposed that the cell membrane has a diode effect in allowing the absorption of electrical charge, which, by its influence on the calcium ion, stimulates the cell into activity.

Adolescent↗

PubMed1984

Radio frequency glow discharge and solid-phase lactoperoxidase-glucose oxidase beads as methods for etching ultra-thin plastic sections for immunoelectron microscopy.

Etching techniques to prepare ultra-thin sections for immunoelectron microscopy have incorporated a variety of reagents to expose antigenic sites. In this paper involving 2 techniques for surface etching prior to immunoelectron microscopy, radio frequency glow discharge ( RFGD ) and solid-phase lactoperoxidase-glucose oxidase beads ( Enzymobeads ) are compared to conventional peroxide etching techniques. Measuring such parameters as intensity of granule disposition and titers of antibody resulting in detectable staining. RFGD and Enzymobeads were both superior to the conventional peroxide methodology. Non-specific absorption by ferritin under the conditions utilized was not a problem with Enzymobeads or RFGD method. In addition, RFGD may be useful in situations where peroxide susceptible antigens are under study.

Adsorption↗

PubMed1988

Spontaneous bodily rotations and direction of locomotion at different times after radio frequency lesions at sites in and near the substantia nigra.

Rats were prepared with radio frequency lesions of the dorsolateral or ventromedial regions of the substantia nigra. Other rats were prepared as operated and unoperated controls for each type of lesion. Their behavior was evaluated in an open field at postoperative days 2, 7, 10, and 15. Three types of behavioral changes were observed over time: those noticeable for a brief period, i.e., a few days, after the lesion (rotational behavior), those lasting 7-10 days after the lesion (turning preferences) and those lasting through the end of the experiment that may be permanent (enhanced locomotion). The early effect of the medioventral lesions was pronounced contralateral rotation while the early effect of the dorsolateral lesion was ipsilateral rotation. This effect of the dorsal lateral lesions was reversed on test days 7 and 10. Lesion-induced turning changes associated with forward locomotion were observed on these two test days as well. By 15 days after surgery the only demonstrable effect of either lesion was enhanced locomotion. The results are discussed in terms of various theories of substantia nigra regulation of motor activities.

Animals↗

PubMed1994

Circadian rhythms of blood pressure, heart rate, and locomotor activity in spontaneously hypertensive rats as measured with radio-telemetry.

Circadian rhythms of blood pressure, heart rate, and locomotor activity were measured with implanted radio-telemetry transmitters in conscious, unrestrained spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). During the light period (0600 to 1800 h) systolic, diastolic, and mean blood pressure, heart rate, and locomotor activity were lower than during the dark period (1800 to 0600 h). During the first and the last hour of the dark period, all parameters showed a relative peak when compared to values during the rest of the night. The pattern of circadian changes in blood pressure, heart rate, or behavior was essentially similar in SHR and WKY. Blood pressure values were always higher in SHR than in WKY, but there was no general strain difference in heart rate or locomotor activity values. The administration of hydralazine in the drinking water resulted in a significant decrease in blood pressure in SHR and WKY, and a suppression of the difference between light-phase values and dark-phase values. By contrast, heart rate showed an overall increase in both strains, whereas locomotor activity was largely unaffected. These data show the validity of telemetry as a means of measuring circadian rhythms of blood pressure, heart rate, and behavior in freely moving rats. Apart from their characteristic hypertension, SHR show few differences with WKY with respect to other parameters, such as circadian rhythmicity, baseline heart rate values, or behavior. Some of the previously published differences between SHR and WKY may have been influenced by the stress of the experimental procedures used.

Animals↗

PubMed1996

Assessment of radio-frequency electromagnetic radiation by the micronucleus test in bovine peripheral erythrocytes.

Previous bioindicative studies in the Skrunda Radio Location Station area have focused on the somatic influence of electromagnetic radiation on plants, but it is also important to study genetic effects. We have chosen cows as test animals for cytogenetical evaluation because they live in the same general exposure area as humans, are confined to specific locations and are chronically exposed to radiation. Blood samples were obtained from female Latvian Brown cows from a farm close to and in front of the Skrunda Radar and from cows in a control area. A simplified alternative to the Schiff method of DNA staining for identification of micronuclei in peripheral erythrocytes was applied. Microscopically, micronuclei in peripheral blood erythrocytes were round in shape and exhibited a strong red colour. They are easily detectable as the only coloured bodies in the uncoloured erythrocytes. From each individual animal 2000 erythrocytes were examined at a magnification of x 1000 for the presence of micronuclei. The counting of micronuclei in peripheral erythrocytes gave low average incidences, 0.6 per 1000 in the exposed group and 0.1 per 1000 in the control, but statistically significant (P < 0.01) differences were found in the frequency distribution between the control and exposed groups.

Animals↗

PubMed1986

Radio-frequency analysis of the effect of haloperidol and cyclo (leucyl-glycyl) on apomorphine-induced stereotypy.

Our previous studies indicated that the peptide cyclo(leucyl-glycyl) (cLG) prevents the development of supersensitivity to dopamine in several animal models at both biochemical and behavioral levels. We therefore tested cLG in a paradigm more commonly used to model tardive dyskinesia, namely chronic haloperidol administration to rats. We found that cLG administered subcutaneously at a dose of 8 mg/kg, blocked about 50% of the supersensitizing effects of of haloperidol on apomorphine-induced stereotypic behaviors. Further, we used a novel method, radio-frequency analysis, that quantifies sniffing and other stereotypic movements. Unlike methods that rely on visual observation of stereotypy and utilize an ordinal scale, these measurements are rated by an automatic motility monitor and utilize a ratio scale. Unlike other automated motility monitors, this device can distinguish between various forms of stereotypic behaviors. Since parametric statistics can be used, there is a significant improvement in the efficiency of the task of rating and comparing stereotypy scores.

Animals↗

PubMed1983

Monitoring of movement with radio frequency transducers.

Two approaches to the problem of monitoring human movement using radio frequency transducers are described. A simple two dimensional solution can monitor movement restricted to one plane, whilst a three dimensional transducer (linked to a computer), can follow movement in any plane. In both cases, by measuring the magnetic field produced by a set of small coils powered with high frequency current it is possible to calculate their relative displacement. If the coils are attached to the surface of the human body they can thus be used as a monitor of human movement.

Computers↗

PubMed1983

Receiving, decoding and noise limiting systems for a new pressure-sensitive ingestible radio telemetric capsule.

A new pressure-sensitive radiotelemetric capsule for recording intraluminal pressures within the human gastrointestinal tract has been developed; this capsule employs a pulsed mode of operation. Data recording as a pulse train greatly simplifies problems encountered hitherto in this field, but has produced the requirement for a decoding system which, on tape replay, will reproduce the original pressure change. A system is described here which, in addition to producing an analogue signal from the recorded pulse train, will also eliminate artefacts due to either spurious radio signals or variations in magnetic tape transport speed; it also provides a sensitive and accurate indication of transient signal loss.

Capsules↗

PubMed1990

Characterization of hydrophobicity gradients prepared by means of radio frequency plasma discharge.

A hydrophobicity gradient was created by gradually exposing a polydimethylsiloxane film to a radio frequency glow discharge in an oxygen atmosphere. A change in contact angle from 100 to 0 degrees was measured along the gradient surface by means of the Wilhelmy balance technique. The gradient surface was characterized by studying the adsorption from single protein solutions of human albumin, IgG and fibrinogen using total internal reflectance fluorescence (TIRF). Generally, adsorption values similar to monolayer capacities were measured on the hydrophobic side. The adsorption decreased towards the hydrophilic end in correspondence with the change in contact angle. The displacement of proteins with a ethylene oxide-propylene oxide copolymer (EO70PO100EO70) was higher on the hydrophobic side than on the hydrophilic side. Albumin showed an adsorption peak in the wetting transition region, indicating a very strong affinity.

Adsorption↗