Bronchoscopic implantation of a novel wireless electromagnetic transponder in the canine lung: a feasibility study.

PURPOSE: The success of targeted radiation therapy for lung cancer treatment is limited by tumor motion during breathing. A real-time, objective, nonionizing, electromagnetic localization system using implanted electromagnetic transponders has been developed (Beacon electromagnetic transponder, Calypso Medical Technologies, Inc., Seattle, WA). We evaluated the feasibility and fixation of electromagnetic transponders bronchoscopically implanted in small airways of canine lungs and compared to results using gold markers. METHODS AND MATERIALS: After approval of the Animal Studies Committee, five mongrel dogs were anesthetized, intubated, and ventilated. Three transponders were inserted into the tip of a plastic catheter, passed through the working channel of a flexible bronchoscope, and implanted into small airways of a single lobe using fluoroscopic guidance. This procedure was repeated for three spherical gold markers in the opposite lung. One, 7, 14, 28, and 60 days postimplantation imaging was used to assess implant fixation. RESULTS: Successful bronchoscopic implantation was possible for 15 of 15 transponders and 12 of 15 gold markers; 3 markers were deposited in the pleural space. Fixation at 1 day was 15 of 15 for transponders and 12 of 12 for gold markers. Fixation at 60 days was 6 of 15 for transponders and 7 of 12 for gold markers, p value = 0.45. CONCLUSIONS: Bronchoscopic implantation of both transponders and gold markers into the canine lung is feasible, but fixation rates are low. If fixation rates can be improved, implantable electromagnetic transponders may allow improved radiation therapy for lung cancer by providing real-time continuous target tracking. Developmental work is under way to improve the fixation rates and to reduce sensitivity to implantation technique.

Fiducial-based translational localization accuracy of electromagnetic tracking system and on-board kilovoltage imaging system.

PURPOSE: The Calypso medical four-dimensional localization system uses AC electromagnetics, which do not require ionizing radiation, for accurate, real-time tumor tracking. This investigation compared the static and dynamic tracking accuracy of this system to that of an on-board imaging kilovoltage X-ray system for concurrent use of the two systems. METHODS AND MATERIALS: The localization accuracies of a kilovoltage imaging system and a continuous electromagnetic tracking system were compared. Using an in-house developed four-dimensional stage, quality-assurance fixture containing three radiofrequency transponders was positioned at a series of static locations and then moved through the ellipsoidal and nonuniform continuous paths. The transponder positions were tracked concurrently by the Calypso system. For static localization, the transponders were localized using portal images and digitally reconstructed radiographs by commercial matching software. For dynamic localization, the transponders were fluoroscopically imaged, and their positions were determined retrospectively using custom-written image processing programs. The localization data sets were synchronized with and compared to the known quality assurance fixture positions. The experiment was repeated to retrospectively track three transponders implanted in a canine lung. RESULTS: The root mean square error of the on-board imaging and Calypso systems was 0.1 cm and 0.0 cm, respectively, for static localization, 0.22 mm and 0.33 mm for dynamic phantom positioning, and 0.42 mm for the canine study. CONCLUSION: The results showed that both localization systems provide submillimeter accuracy. The Calypso and on-board imaging tracking systems offer distinct sets of advantages and, given their compatibility, patients could benefit from the complementary nature of the two systems when used concurrently.

The effect of transponder motion on the accuracy of the Calypso Electromagnetic localization system.

PURPOSE: To determine position and velocity-dependent effects in the overall accuracy of the Calypso Electromagnetic localization system, under conditions that emulate transponder motion during normal free breathing. METHODS AND MATERIALS: Three localization transponders were mounted on a remote-controlled turntable that could move the transponders along a circular trajectory at speeds up to 3 cm/s. A stationary calibration established the coordinates of multiple points on each transponder's circular path. Position measurements taken while the transponders were in motion at a constant speed were then compared with the stationary coordinates. RESULTS: No statistically significant changes in the transponder positions in (x,y,z) were detected when the transponders were in motion. CONCLUSIONS: The accuracy of the localization system is unaffected by transponder motion.

Local electric field enhancement and polarization effects in a surface-enhanced Raman scattering fiber sensor with chessboard nanostructure.

A surface-enhanced Raman scattering fiber sensor with chessboard nanostructure on a cleaved fiber facet is studied by finite-difference time-domain method. Surface plasmons at the metal coated nanostructured fiber facet can be effectively excited and strong local electric field enhancement is obtained. Studies on the influence of light polarization demonstrate a large polarization dependence of the field enhancement factor while the polarization effects on the plasmon resonance wavelength are relatively small.

Photorefractive solitons of arbitrary and controllable linear polarization determined by the local bias field.

We discuss and experimentally demonstrate a scheme to achieve photorefractive solitons of arbitrary linear polarization using the quadratic electro-optic effect and describe the observation of the self-trapping of a set of linear polarized beams in different positions of a paraelectric photorefractive crystal of potassium-lithium-tantalate-niobate (KLTN) biased by the inhomogeneous field produced by two miniaturized top electrodes. The polarization of the single solitons of the set is determined by the local electrostatic configuration and the underlying tunable anisotropy, which is detected through zero-field electro-activation.

Guided plasmonic modes in nanorod assemblies: strong electromagnetic coupling regime.

We demonstrate that the coupling between plasmonic modes of oriented metallic nanorods results in the formation of an extended (guided) plasmonic mode of the nanorod array. The electromagnetic field distribution associated to this mode is found to be concentrated between the nanorods within the assembly and propagates normally to the nanorod long axes, similar to a photonic mode waveguided by an anisotropic slab. This collective plasmonic mode determines the optical properties of nanorod assemblies and can be tuned in a wide spectral range by changing the nanorod array geometry. This geometry represents a unique opportunity for light guiding applications and manipulation at the nanoscale as well as sensing applications and development of molecular plasmonic devices.

Electromagnetic concentrators with reduced material parameters based on coordinate transformation.

Omni-directional electromagnetic field concentrators have been recently reported by Marco Rahm et al. [Photon. Nanostruct.: Fundam. Appl. 6, 87 (2008)] based on form-invariant coordinate transformations related to its Jacobi transformation matrix. Using transverse-electric wave illumination, we reduced the complex material parameters of the concentrator for future practical implementation. Concentrators with different set of permittivity and permeability tensors are proposed. The electromagnetic concentrating performance and the scattering properties at the inner and outer boundary of these concentrators are theoretically and numerically analyzed. Finally we obtain a set of material tensors for a concentrator that simultaneously has perfect matched interior and exterior interfaces.

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.

Resonator with reduced sample heating and increased homogeneity for solid-state NMR.

In the application of solid-state NMR to many systems, the presence of radiofrequency (rf) electric fields inside classical solenoidal coils causes heating of lossy samples. In particular, this is critical for proteins in ionic buffers. Rf sample heating increases proportional to frequency which may result in the need to reduce the rf pulse power to prevent partial or total sample deterioration. In the present paper, we propose a multifrequency-tunable NMR resonator where the sample is electrically shielded from the NMR coil by a conductive sheet that increases the magneto-electric ratio. Expressions for the B1 efficiency as function of magnetic and electric filling factors are derived that allow a direct comparison of different resonators. Rf efficiency, homogeneity, signal-to-noise, and rf sample heating are compared. NMR spectra at 700MHz on ethylene glycol, glycine, and a model protein were acquired to compare the resonators under realistic experimental conditions.

Noise performance of a precision pulsed electromagnet power supply for magnetic resonance imaging.

Prepolarized magnetic resonance imaging (PMRI) uses two pulsed electromagnets to achieve high-field image quality with the benefits of low-field data acquisition. The principal challenge with all resistive MRI systems is the implementation of a highly precise magnet current supply. The noise current through the magnet is fundamentally limited by the current transducer used to provide feedback and the voltage reference used to generate the demand signal. Field instability in the main field magnet can both corrupt the received data and degrade the robustness of Carr¿Purcell¿Meiboom¿Gill (CPMG) echo trains, which are paramount to efficient imaging in PMRI. In this work, we present the magnet control system that achieved sufficient field stability for PMRI at $0.5/0.13$ T, identify the dominant sources of noise in the control system, examine the imaging artifacts that can occur if the field stability is insufficient, and identify how the design can be improved for better field stability, should it be required for future implementations of PMRI.

Measuring tooth mobility with a no-contact vibration device.

BACKGROUND AND OBJECTIVE: Mechanical parameters obtained from the frequency response at tooth vibration informs of various periodontal tissue conditions. An electromagnetic vibration device was investigated for measuring tooth mobility using mechanical parameters obtained from the frequency response characteristics of an experimental tooth model. This electromagnetic vibration device was able to assess the overall condition of periodontal tissue associated with the alteration of each parameter. In this study, reliability and effects of bottom thicknesses of simulated periodontal ligament relative to mechanical parameters were analysed. MATERIAL AND METHODS: Measurement of tooth vibration was performed by an electromagnetic vibration device on experimental tooth models with different bottom thicknesses of simulated periodontal ligament. Using an electromagnetic vibration device, the mechanical parameters resonant frequency, elastic modulus and coefficient of viscosity were calculated from the frequency response characteristics derived from tooth vibration by an electromagnetic force. Variation of those parameters was investigated under four different experimental conditions and the implications of the results were discussed. RESULTS: An electromagnetic vibration device clearly detected three mechanical parameters in all experimental conditions. The resonant frequency and the elastic modulus decreased with increasing bottom thickness. However, no significant difference in the coefficient of viscosity was observed among the experimental conditions. CONCLUSION: Assessment of tooth mobility using mechanical parameters of an electromagnetic vibration device reproduced fine details of various simulated periodontal ligament conditions. Variation in the parameters resonant frequency, elastic modulus and coefficient of viscosity might be useful in evaluating changes of components in periodontal tissues.

Non-invasive longitudinal assessment of facial growth in children and adolescents with hypohidrotic ectodermal dysplasia.

Facial growth patterns in 12 subjects (six boys and six girls) with hypohidrotic ectodermal dysplasia (HED) were analyzed and compared with facial growth patterns obtained in healthy reference peers. All subjects with HED were aged 7 yr (mean age +/- standard deviation: 7.08 +/- 0.41 yr) at the first examination and 14 yr (mean age +/- standard deviation: 14.56 +/- 0.34 yr) at the last examination. In each subject, the three-dimensional coordinates of facial landmarks were collected non-invasively at eight subsequent years. The volumes of forehead, nose, maxilla and mandible, upper lips, and lower lips were estimated. For each facial volume, differential values between different time points were calculated individually, separately for the 'childhood' (7-10 yr) and the 'adolescence' (11-14 yr) growth period in both HED and reference subjects. Children and adolescents with HED had a slightly reduced global facial growth in comparison with normal reference peers. The peak mandibular and maxillary development was delayed by approximately 2 yr towards later adolescence. The present non-invasive system seems to be useful for studying longitudinal changes of facial growth in healthy and syndromic subjects.

Performance characterization of a rotary centrifugal left ventricular assist device with magnetic suspension.

The MiTiHeart (MiTiHeart Corporation, Gaithersburg, MD, USA) left ventricular assist device (LVAD), a third-generation blood pump, is being developed for destination therapy for adult heart failure patients of small to medium frame that are not being served by present pulsatile devices. The pump design is based on a novel, patented, hybrid passive/active magnetic bearing system with backup hydrodynamic thrust bearing and exhibits low power loss, low vibration, and low hemolysis. Performance of the titanium alloy prototype was evaluated in a series of in vitro tests with blood analogue to map out the performance envelop of the pump. The LVAD prototype was implanted in a calf animal model, and the in vivo pump performance was evaluated. The animal's native heart imparted a strong pulsatility to the flow rate. These tests confirmed the efficacy of the MiTiHeart LVAD design and confirmed that the pulsatility does not adversely affect the pump performance.

Multimodality bronchoscopic diagnosis of peripheral lung lesions: a randomized controlled trial.

RATIONALE: Endobronchial ultrasound (EBUS) and electromagnetic navigation bronchoscopy (ENB) have increased the diagnostic yield of bronchoscopic diagnosis of peripheral lung lesions. However, the role of combining these modalities to overcome each individual technique's limitations and, consequently, to further increase the diagnostic yield remains untested. OBJECTIVES: A prospective randomized controlled trial involving three diagnostic arms: EBUS only, ENB only, and a combined procedure. METHODS: All procedures were performed via flexible bronchoscopy and transbronchial forceps biopsies were obtained without fluoroscopic guidance. In the combined group, after electromagnetic navigation, the ultrasound probe was passed through an extended working channel to visualize the lesion. Biopsies were taken if ultrasound visualization showed that the extended working channel was within the target. Primary outcome was diagnostic yield. The reference "gold standard" was a surgical biopsy if bronchoscopic biopsy did not reveal a definite histological diagnosis compatible with the clinical presentation. Secondary outcomes were yields by size, lobar distribution, and lesion pathology. Complication rates were also documented. MEASUREMENTS AND MAIN RESULTS: Of the 120 patients recruited, 118 had a definitive histological diagnosis and were included in the final analysis. The diagnostic yield of the combined procedure (88%) was greater than EBUS (69%) or ENB alone (59%; p = 0.02). The combined procedure's yield was independent of lesion size or lobar distribution. The pneumothorax rates ranged from 5 to 8%, with no significant differences between the groups. CONCLUSIONS: Combined EBUS and ENB improves the diagnostic yield of flexible bronchoscopy in peripheral lung lesions without compromising safety.

A doubly resonant cavity for detection of RF demodulation by living cells.

We describe the design, construction, and operating characteristics of a doubly resonant cylindrical microwave cavity. This cavity has been developed to allow a search for nonlinear RF energy conversion in biological cells. Cells with a diode-like nonlinearity could demodulate a modulated RF carrier wave and generate low frequency signals in an exposed biological preparation. The cavity is designed to be resonant on the TE(111) mode at about 890 MHz and on the TE(113) mode at about 1780 MHz. The cavity performs exactly as designed and has proved capable of detecting the nonlinearity in a microscopic Schottky diode test structure. The sensitivity is sufficient to detect any nonlinearity in a collection of biological cells that could have any potential biological significance.

Setup and dosimetry for exposure of human skin in vivo to RF-EMF at 900 MHz.

The aim of this study was a dosimetrical analysis of an experimental setup used in the exposure of 10 female volunteers to GSM 900 radiation. The exposure was carried out by irradiating a small region of the right forearms of the volunteers for 1 h, after which biopsies were taken from the exposed skin for protein analysis. The source of irradiation was a half-wave dipole fed with a computer controlled GSM phone. The specific absorption rate (SAR) induced in the skin biopsy was assessed by computer simulations. The numerical model of the arm consisted of a muscle tissue simulating cylinder covered with thin skin (1 mm) and fat (3 mm) layers. The simulation models were validated by measurements with a homogeneous cylindrical liquid phantom. The average SAR value in the biopsy was 1.3 W/kg and the estimated uncertainty +/-20% (K = 2). The main source of error was found to be variations in the distance of the forearm from the dipole (10 +/- 1 mm). Other significant sources of uncertainty are individual variations of the fat layer and arm thicknesses, and the uncertainty of radio frequency (RF) power measurement.

A method for quantifying condylar motion in patients with osteoarthritis using an electromagnetic tracking device and computed tomography imaging.

PURPOSE: The purpose of this study was to develop a method to accurately study the kinematic changes of the temporomandibular joint (TMJ) in patients treated with hemijoint implant reconstruction for dysfunction of advanced degenerative osteoarthritis. MATERIALS AND METHODS: Mandibular kinematic motion data and patient-specific computed tomography (CT) data were acquired. Patients were fitted with custom dental stents that were embedded with metal markers to link the mandibular kinematics data with the 3-dimensional TMJ CT images. An electromagnetic tracking device was used to collect kinematic motion data during maximal mouth opening and closing. The coordinate systems of the kinematic data and CT data were registered to calculate the motion of the mandibular condyle. RESULTS: This technique was successfully used to study patients with motion aberration of the TMJ due to osteoarthritis. A typical case is illustrated in which the motion of both mandibular condyles was simulated preoperatively and postoperatively. CONCLUSIONS: The results of this study suggest that it is possible to use the proposed methodology to accurately quantify the motion of the mandibular condyle in 3 dimensions. The developed technique is user-friendly and noninvasive to the patient. The proposed methodology is a potential clinical tool that may be used in the management of patients with TMJ dysfunction.

Development of gas pulsing system for electron cyclotron resonance ion source.

A gas-pulsing system for an electron cyclotron resonance ion source with all permanent magnets (Kei2 source) at NIRS has been developed and tested. The system consists of a small vessel (30 ml) to reserve CH(4) gas and two fast solenoid valves that are installed at both sides of the vessel. They are connected to each other and to the Kei2 source by using a stainless-steel pipe (4 mm inner diameter), where the length of the pipe from the valve to the source is 60 cm and the conductance is 1.2 l/s. From the results of the test, almost 300 e microA for a pulsed (12)C(4+) beam was obtained at a Faraday cup in an extraction-beam channel with a pressure range of 4000 Pa in the vessel. At this time, the valve has an open time of 10 ms and the delay time between the valve open time and the application of microwave power is 100 ms. In experiments, the conversion efficiency for input CH(4) molecules to the quantity of extracted (12)C(4+) ions in one beam pulse was found to be around 3% and the ratio of the total amount of the gas requirement was only 10% compared with the case of continuous gas provided in 3.3 s of repetition in HIMAC.

The negative hydrogen Penning ion gauge ion source for KIRAMS-13 cyclotron.

The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of KIRAMS-13 cyclotron has been used for generation of negative hydrogen ions. The dc H-beam current of 650 microA from the PIG ion source with the Dee voltage of 40 kV and arc current of 1.0 A is extrapolated from the measured dc extraction beam currents at the low extraction dc voltages. The output optimization of PIG ion source in the cyclotron has been carried out by using various chimneys with different sizes of the expansion gap between the plasma boundary and the chimney wall. This paper presents the results of the dc H-extraction measurement and the expansion gap experiment.

Performance optimization of H(-) multicusp ion source for KIRAMS-30 cyclotron.

KIRAMS-30 cyclotron has been developed and implemented for radio isotope production. For the purpose of producing negative hydrogen ions and low energy beam injection to the central region of KIRAMS-30, 10 mA H(-) multicusp ion source with beam kinetic energies in the 20-30 keV range and the normalized 4 rms emittance less than 1 mm mrad was installed. The optimized ion source operating condition is presented and the correlation between the extracted beam current and ion source parameters is described for the performance enhancement of the ion source.