Ultrabroadband polarization analysis of terahertz pulses.

We describe the characteristics of a sensitive photoconductive detector that simultaneously measures orthogonal electric field components of electromagnetic transients with bandwidths up to 30 THz. The device consists of an As(+) implanted GaAs photoconducting region at the centre of a pair of perpendicular bow-tie antennas. The performance is illustrated by studies of optical rectification in GaSe, retardation in a birefringent polymer film and THz emission from impulsively excited optical phonons in GaN.

[A magnetic therapy apparatus with an adaptable electromagnetic spectrum for the treatment of prostatitis and gynecopathies].

Problems of engineering and algorithm development of magnetic therapy apparatuses with pseudo-random radiation spectrum within the audio range for treatment of prostatitis and gynecopathies are considered. A typical design based on a PIC 16F microcontroller is suggested. It includes a keyboard, LCD indicator, audio amplifier, inducer, and software units. The problem of pseudo-random signal generation within the audio range is considered. A series of rectangular pulses is generated on a random-length interval on the basis of a three-component random vector. This series provides the required spectral characteristics of the therapeutic magnetic field and their adaptation to the therapeutic conditions and individual features of the patient.

Hyperthermia system with thermoseed set in abdominal cavity and AC-magnetic-field.

We propose a hyperthermia system for cancer developed in abdominal cavity. Local/deep spot heating and its less invasion feature are expected to be realized by thermoseed. This thermoseed is made of ferromagnetic material and it changes AC magnetic field power from outside of body to heat. AC magnetic field frequency is set on the value not to be absorbed to organs or tissues. We made a heat model of thermoseed and in vivo environment. The amount of heat and heat conduction were calculated from the characteristic values of materials and AC magnetic field. Effective shape of thermoseed for hyperthermia can be designed easily from this calculation. Results showed possibility of effective hyperthermia using this system through evaluation experiments.

Electromagnetic head-and-neck hyperthermia applicator: experimental phantom verification and FDTD model.

PURPOSE: To experimentally verify the feasibility of focused heating in the neck region by an array of two rings of six electromagnetic antennas. We also measured the dynamic specific absorption rate (SAR) steering possibilities of this setup and compared these SAR patterns to simulations. METHODS AND MATERIALS: Using a specially constructed laboratory prototype head-and-neck applicator, including a neck-mimicking cylindrical muscle phantom, we performed SAR measurements by electric field, Schottky-diode sheet measurements and, using the power-pulse technique, by fiberoptic thermometry and infrared thermography. Using phase steering, we also steered the SAR distribution in radial and axial directions. All measured distributions were compared with the predictions by a finite-difference time-domain-based electromagnetic simulator. RESULTS: A central 50% iso-SAR focus of 35 +/- 3 mm in diameter and about 100 +/- 15 mm in length was obtained for all investigated settings. Furthermore, this SAR focus could be steered toward the desired location in the radial and axial directions with an accuracy of approximately 5 mm. The SAR distributions as measured by all three experimental methods were well predicted by the simulations. CONCLUSION: The results of our study have shown that focused heating in the neck is feasible and that this focus can be effectively steered in the radial and axial directions. For quality assurance measurements, we believe that the Schottky-diode sheet provides the best compromise among effort, speed, and accuracy, although a more specific and improved design is warranted.

Pulp ablation therapy by inductive heating: heat generation characteristics in the pulp cavity.

OBJECTIVE AND METHODS: This study was performed to clarify the usefulness of inductive heating system for the new endodontic therapy. Dextran magnetite complex (DM) suspensions were injected into the root canal of a permanent tooth, and the tooth was heated up to about 55.0 degrees C by alternating-current magnetic field. RESULTS AND CONCLUSION: The time until the temperature in the pulp cavity reached 55.0 degrees C was 328 +/- 26 s (mean +/- s.d., n = 8) in the 56 mg as Fe ml(-1) of DM concentration. The temperature in the pulp cavity could be maintained at 53.5-59.0 degrees C for 1200 s by changing the magnetic field intensity safely, while temperature elevations of the dental surface on the coronal and apical sides were 4.9 degrees and 3.7 degrees C, respectively. Thus, this inductive heating system, which has the possibility of selective heating, might be useful for eliminating residues of pulp as a new ablation therapy.

Accelerated closure of biopsy-type wounds by mechanical stimulation.

OBJECTIVE: To determine whether a device designed to provide low-intensity, low-frequency mechanical stimulation improves healing time of acute wounds. DESIGN: Repeated measures using mechanical stimulation on one side of a rat and sham stimulation on the contralateral side. SETTING: Academic animal facility. PARTICIPANTS: Six male Sprague-Dawley rats, approximately 400 g. INTERVENTION: Mechanical stimulation of 4-mm biopsy wounds in rats was produced through the use of permanent magnets cyclically attracted and repelled by activation of an electromagnet by a square wave generator at a frequency of 1 Hz and a force equivalent to 64 mm Hg pressure. MAIN OUTCOME MEASURE: Days to complete closure of 4-mm biopsy punch wounds. MAIN RESULTS: This form of stimulation reduced time to close the biopsy wounds by nearly 50%. Mechanically stimulated wounds closed in 3.8 +/- 1.6 days (mean +/- SD) compared with 6.8 +/- 1.9 days for sham-stimulated wounds (P = .0002). CONCLUSION: Production of a mechanical stimulation device with a miniaturized controller and power source and trials on humans are needed to determine the efficacy and potential cost savings of such a device in the management of wounds.

Avoiding electromagnetic artifacts when recording auditory steady-state responses.

Electromagnetic artifacts can occur when recording multiple auditory steady-state responses evoked by sinusoidally amplitude modulated (SAM) stimuli. High-intensity air-conducted stimuli evoked responses even when hearing was prevented by masking. Additionally, high-intensity bone-conducted stimuli evoked responses that were completely different from those evoked by air-conducted stimuli of similar sensory level. These artifacts were caused by aliasing since they did not occur when recordings used high analog-digital (AD) conversion rates or when high frequencies in the electroencephalographic (EEG) signal were attenuated by steep-slope low-pass filtering. Two possible techniques can displace aliased energy away from the response frequencies: (1) using an AD rate that is not an integer submultiple of the carrier frequencies and (2) using stimuli with frequency spectra that do not alias back to the response frequencies, such as beats or "alternating SAM" tones. Alternating SAM tones evoke responses similar to conventional SAM tones, whereas beats produce significantly smaller responses.

Repetitive transcranial magnetic stimulation and electroconvulsive therapy: complementary or competitive therapeutic options in depression?

OBJECTIVE: To examine issues pertaining to the potential clinical roles of repetitive transcranial magnetic stimulation (rTMS) and the relationship of these to the use of electroconvulsive therapy (ECT). METHODS: A review of studies was carried out comparing the use of rTMS and ECT, with consideration of issues relating to the populations in which rTMS may be applied. RESULTS: There have been a number of randomized comparisons of rTMS and ECT. There are limitations with these studies, but in general they indicate that in non-psychotic patients rTMS appears to have a similar rate of response to ECT and certainly seems to have meaningful clinical effects. There are a number of clinical subpopulations in whom rTMS, but not ECT, is suitable, and assessment of the effectiveness of TMS in these populations is required. CONCLUSIONS: Repetitive TMS and ECT are likely to prove to be complementary clinical tools and the introduction of clinical programmes with rTMS will enhance patient options rather than replace the use of ECT.

[The appreciation of bone growth factor in women with osteoporosis exposing on freetransition magnetic field]. / Ocena markerów tworzenia kosci u kobiet z osteoporoza eksponowanych wolnozmiennymi polami magnetycznymi.

In spite of many news bulletin of favorable influence of freetransition magnetic field on regeneration bone tissue, there is lack of information of function mechanism on bone metabolism. The aim of this work was to evaluate the concentrations of bone growth factors (osteokalcin, prokolagen, estrogens) and mineral density of cervical bone in women expose on freetransition magnetic field. 40 women were treatment age 50-55 in postmenopause period divided in two groups: I--control group, age 51.3+/-2.6 seemingly exposed on freetransition magnetic field 12 minutes a day 30 days, and then 24 minutes of expose per week 150 days; II--group age 53.4+/-1.9, exposed on freetransition magnetic field generationed by Viofor JPS (Med. and Life) with the time of exposition like in group I. Before and after the concentrations of estron, estradiol, osteokalcyn, prokolagen, total and ionize calcium, phosphor ion in plasma in both groups were examined. Mineral density of cervical bone was examined before treatment and after 12 month DEXA method (Lunar DPX). There was insignificant increase of concentration osteokalcyn, prokolagen, insignificant decrease total and ionize calcium, significant increase of concentration of estron, estradiol (p<0.05) and mineral density of cervical bones (0.001) in group exposed on freetransition magnetic field. There are no differences between concentration of calcium and phosphor in women from two groups.

Information for assistants of repeated transcranial magnetic stimulation.

Repeated transcranial magnetic stimulation (rTMS) is an exciting new technology being used in psychiatric and neurological research in many centres around the world. rTMS has been accepted as a routine treatment of depression in Canada and Israel. To this point, it has been exclusively conducted by medical officers. As knowledge and experience grows, it is probable that professionals with other backgrounds will have the opportunity to play a role. The aim of this paper is to provide information that will be valuable to assistants. Electromagnetic principles are harnessed to deliver electric currents to localized regions of the cortex. rTMS does not involve anaesthesia or seizure. Side-effects appear to be few. Much remains uncertain, however, even including the most appropriate treatment parameters.

The application of transcranial magnetic stimulation in psychiatry and neurosciences research.

OBJECTIVE: Over recent years transcranial magnetic stimulation (TMS) has become widely applied in the study of neuropsychiatric disorders. The aim of this article is to review the application of TMS as an investigative tool and as a potential therapeutic modality in psychiatric disorders. METHOD: A comprehensive literature review. RESULTS: When applied as an investigative tool, TMS provides innovative ways to directly study the excitability of the cortex, cortical regional connectivity, the plasticity of brain responses and cognitive functioning in illness and disease states. A number of studies suggest the potential of treatment with TMS in disease states, especially in patients with depression, although difficulties exist with the interpretation of the published literature. CONCLUSION: TMS has a considerable role in neuropsychiatric research. It appears to have considerable potential as a therapeutic tool in depression, and perhaps a role in several other disorders, although widespread application requires larger trials and establishment of sustained response.

Physiological effects of an 8-week mechanically aided resistance facial exercise program.

This paper describes a study that for the first time addresses the physiological effects of an 8-week mechanically aided facial exercise program, using the Facial-Flex device (Facial Concepts, Inc., Blue Bell, PA) with four healthy individuals with no motor, speech, language, or hearing problems. For a variety of non-speech and speech tasks, upper and lower lip muscle activity (EMG) and upper and lower lip movements were recorded at two baseline sessions (separated by 1 week) and immediately after an 8-week training period. The results indicate that after the training period, all four subjects showed an increase in the number of task repetitions and the duration of isometric contraction using the Facial-Flex device with a fixed resistance (Linebaugh tests). However, with respect to physiological changes as related to the exercise program, the results were mixed. Only one subject showed the expected significant increase in normalized EMG activity. This response was mirrored in a significant overall increase in movement range and peak velocity after the 8-week training period. Regarding the other three subjects, one subject showed no systematic training effect at all, whereas the remaining two subjects showed a significant increase in movement duration. Non-speech and speech tasks were found to be clearly different in their overall physiological characteristics; speech related movements were found to be more clearly defined in terms of larger amplitudes, shorter durations, higher peak velocities, and less variable movement cycles. The apparent discrepancy between the results of the Linebaugh tests and the physiological measures on specific oro-motor tasks warrants some caution in drawing conclusions on changes in the oro-motor system based on general performance measures. Further studies with well-defined clinical populations are needed to assess the usefulness of this device as an aid in the treatment of speech disorders based on motor system impairments.

[Evaluation of an electromagnetic virtual target system (CT-guide) for CT-guided interventions]. / Evaluation eines elektromagnetischen virtuellen Zielsystems (CT-Guide) für die Durchführung von CT-Interventionen.

PURPOSE: Evaluation of the accuracy of a new electromagnetic target system for interventional CT-guided procedures with virtual navigation in a previously acquired helical CT. MATERIAL AND METHODS: The new target system CT-Guide 1010 (Ultraguide, Tirat Hacarmel, Israel) for CT-guided interventions was adapted to the video signal of the Somatom Plus 4 and Volume Zoom (Siemens, Erlangen, Germany). A helical CT-dataset including skin-based sensor cubes was transferred to the integrated navigation system inside the scanner room. 50 image-guided interventions and biopsies were performed outside the gantry using virtual navigation to reach the lesion. The accuracy of the procedures was evaluated using documentation of the needle tip with CT-fluoroscopy, results of histology, and follow-up. RESULTS: The deviation between planned and documented needle tip was 2.2 +/- 2.1 mm in 50 procedures. Time between the end of planning-CT and needle positioning using the system was 13 minutes. There were no complications due to the use of the system. CONCLUSION: The CT-Guide allows for virtual real-time navigation with high accuracy. Advantages are the free needle angulation without gantry tilt, use of optimal CT perfusion phase for virtual navigation, and reduction of radiation exposure to the patient and interventionalist.

Detailed endocardial mapping accurately predicts the transmural extent of myocardial infarction.

OBJECTIVES: This study delineates between infarcts varying in transmurality by using endocardial electrophysiologic information obtained during catheter-based mapping. BACKGROUND: The degree of infarct transmurality extent has previously been linked to patient prognosis and may have significant impact on therapeutic strategies. Catheter-based endocardial mapping may accurately delineate between infarcts differing in the transmural extent of necrotic tissue. METHODS: Electromechanical mapping was performed in 13 dogs four weeks after left anterior descending coronary artery ligation, enabling three-dimensional reconstruction of the left ventricular chamber. A concomitant reduction in bipolar electrogram amplitude (BEA) and local shortening indicated the infarcted region. In addition, impedance, unipolar electrogram amplitude (UEA) and slew rate (SR) were quantified. Subsequently, the hearts were excised, stained with 2,3,5-triphenyltetrazolium chloride and sliced transversely. The mean transmurality of the necrotic tissue in each slice was determined, and infarcts were divided into <30%, 31% to 60% and 61% to 100% transmurality subtypes to be correlated with the corresponding electrical data. RESULTS: From the three-dimensional reconstructions, a total of 263 endocardial points were entered for correlation with the degree of transmurality (4.6 +/- 2.4 points from each section). All four indices delineated infarcted tissue. However, BEA (1.9 +/- 0.7 mV, 1.4 +/- 0.7 mV, 0.8 +/- 0.4 mV in the three groups respectively, p < 0.05 between each group) proved superior to SR, which could not differentiate between the second (31% to 60%) and third (61% to 100%) transmurality subgroups, and to UEA and impedance, which could not differentiate between the first (<30%) and second transmurality subgroups. CONCLUSIONS: The degree of infarct transmurality extent can be derived from the electrical properties of the endocardium obtained via detailed catheter-based mapping in this animal model.

Directed and enhanced neurite growth with pulsed magnetic field stimulation.

Pulsed magnetic field (PMF) stimulation was applied to mammalian neurons in vitro to influence axonal growth and to determine whether induced current would direct and enhance neurite growth in the direction of the current. Two coils were constructed from individual sheets of copper folded into a square coil. Each coil was placed in a separate water-jacketed incubator. One was energized by a waveform generator driving a power amplifier, the other was not energized. Whole dorsal root ganglia (DRG) explant cultures from 15-day Sprague-Dawley rat embryos were established in supplemented media plus nerve growth factor (NGF) at concentrations of 0-100 ng/mL on a collagen-laminin substrate. Dishes were placed at the center of the top and bottom of both coils, so that the DRG were adjacent to the current flowing in the coil. After an initial 12 h allowing DRG attachment to the substrate floor, one coil was energized for 18 h, followed by a postexposure period of 18 h. Total incubation time was 48 h for all DRG cultures. At termination, DRG were histochemically stained for visualization and quantitative analysis of neurite outgrowth. Direction and length of neurite outgrowth were recorded with respect to direction of the current. PMF exposed DRG exhibited asymmetrical growth parallel to the current direction with concomitant enhancement of neurite length. DRG cultures not PMF exposed had a characteristic radial pattern of neurite outgrowth. These results suggest that PMF may offer a noninvasive mechanism to direct and promote nerve regeneration.

High resolution MRI of the deep brain vascular anatomy at 8 Tesla: susceptibility-based enhancement of the venous structures.

PURPOSE: The purpose of this work was to describe the deep vascular anatomy of the human brain using high resolution MR gradient echo imaging at 8 T. METHOD: Gradient echo images were acquired from the human head using a transverse electromagnetic resonator operating in quadrature and tuned to 340 MHz. Typical acquisition parameters were as follows: matrix = 1,024 x 1,024, flip angle = 45 degrees, TR = 750 ms, TE = 17 ms, FOV = 20 cm, slice thickness = 2 mm. This resulted in an in-plane resolution of approximately 200 microm. Images were analyzed, and vascular structures were identified on the basis of location and course. RESULTS: High resolution ultra high field magnetic resonance imaging (UHFMRI) enabled the visualization of many small vessels deep within the brain. These vessels were typically detected as signal voids, and the majority represented veins. The prevalence of the venous vasculature was attributed largely to the magnetic susceptibility of deoxyhemoglobin. It was possible to identify venous structures expected to measure below 100 microm in size. Perforating venous drainage within the deep gray structures was identified along with their parent vessels. The course of arterial perforators was more difficult to follow and not as readily identified as their venous counterparts. CONCLUSION: The application of high resolution gradient echo methods in UHFMRI provides a unique detailed view of particularly the deep venous vasculature of the human brain.

A HF EM installation allowing simultaneous whole body and deep local EM hyperthermia.

The structure and main features of a HF EM installation based upon a new approach for creating electromagnetic fields destined for whole body (WBH) and deep local (DLH) hyperthermia are discussed. The HF EM field, at a frequency of 13.56 MHz, is created by a coplanar capacity type applicator positioned under a distilled water filled bolus that the patient is lying on. The EM energy being released directly in the deep tissues ensures effective whole body heating to required therapeutic temperatures of up to 43.5 degrees C, whereas the skin temperature can be maintained as low as 39-40.5 degrees C. For DLH, the installation is equipped with additional applicators and a generator operating at a frequency of 40.68 MHz. High efficiency of the WBH applicator makes it possible to carry out the WBH procedure without any air-conditioning cabin. Due to this, a free access to the patient's body during the WBH treatment is provided and a simultaneous WBH/DLH or WBH/LH procedure by means of additional applicators is possible. Controllable power output in the range of 100-800 W at a frequency of 13.56 MHz and 50-350 W at a frequency of 40.68 MHz allows accurate temperature control during WBH, DLH and WBH/DLH procedures. SAR patterns created by the WBH and DLH applicators in a liquid muscle phantom and measured by means of a non-perturbing E-dipole are investigated. The scattered EM field strength measured in the vicinity of the operating installation during the WBH, DLH and WBH/DLH procedures does not exceed security standards. Examples of temperature versus time graphs in the course of WBH, DLH and WBH/DLH procedures in clinics are presented. The installation is successfully used in leading oncological institutions of Russia and Belarus, though combined WBH/DLH procedures are evidently more complicated and demand thorough planning and temperature measurements to avoid overheating.