Tunable and Anisotropic Dual-Band Metamaterial Absorber Using Elliptical Graphene-Black Phosphorus Pairs.

We numerically propose a dual-band absorber in the infrared region based on periodic elliptical graphene-black phosphorus (BP) pairs. The proposed absorber exhibits near-unity anisotropic absorption for both resonances due to the combination of graphene and BP. Each of the resonances is independently tunable via adjusting the geometric parameters.

Improved hyperthermia treatment control using SAR/temperature simulation and PRFS magnetic resonance thermal imaging.

Purpose: This article explores the feasibility of using coupled electromagnetic and thermodynamic simulations to improve planning and control of hyperthermia treatments for cancer. The study investigates the usefulness of preplanning to improve heat localisation in tumour targets in treatments monitored with PRFS-based magnetic resonance thermal imaging (MRTI).

Methods: Heating capabilities of a cylindrical radiofrequency (RF) mini-annular phased array (MAPA) applicator were investigated with electromagnetic and thermal simulations of SAR in homogeneous phantom models and two human leg sarcomas.

The performance of a reduced-order adaptive controller when used in multi-antenna hyperthermia treatments with nonlinear temperature-dependent perfusion.

In large multi-antenna systems, adaptive controllers can aid in steering the heat focus toward the tumor. However, the large number of sources can greatly increase the steering time. Additionally, controller performance can be degraded due to changes in tissue perfusion which vary non-linearly with temperature, as well as with time and spatial position.

Control time reduction using virtual source projection for treating a leg sarcoma with nonlinear perfusion.

Purpose: Blood perfusion is a well-known factor that complicates accurate control of heating during hyperthermia treatments of cancer. Since blood perfusion varies as a function of time, temperature and location, determination of appropriate power deposition pattern from multiple antenna array Hyperthermia systems and heterogeneous tissues is a difficult control problem. Therefore, we investigate the applicability of a real-time eigenvalue model reduction (virtual source - VS) reduced-order controller for hyperthermic treatments of tissue with nonlinearly varying perfusion.

Towards the Validation of a Commercial Hyperthermia Treatment Planning System.

Recent developments have reinvigorated clinical investigations of hyperthermia (HT) as a viable adjuvant treatment in the fight against cancer. Researchers are placing a greater emphasis on multi-modal approaches that include mild temperatures (40°C - 43°C) and standard therapies like radiation and chemotherapy than on achieving higher temperature treatments (43°C-45°C) which were pursued in the past. The emergence of robust computer simulation tools for accurate hyperthermia treatment planning has aided this resurgence by helping improve the quality of heating.

Design and analysis of annular antenna arrays with different reflectors.

The design and performance of annular antenna arrays with reflectors is presented. Arrays with three shapes of reflectors are analysed and simulated. These include the corner reflector, the circular reflector and the elliptical reflector.

Microwave breast imaging: 3-D forward scattering simulation.

Active microwave imaging (MWI) is emerging as a promising technique for the detection of biomedical anomalies such as breast cancer because of the high electrical contrasts between malignant tumors and normal tissue. Previously, we have developed fast two-dimensional forward and inverse scattering algorithms for MWI systems. In this paper, we report the full three-dimensional (3-D) forward scattering simulation in order to account for 3-D effects and to provide a fast solver in future 3-D nonlinear inverse scattering methods.

Variations of focal regions versus numbers and positions of sources in two-dimensional media.

This paper explores the behaviour of the primary and secondary hot spots in homogeneous and two-dimensional inhomogeneous medium. Circular arrays are considered with a radius of up to five wavelengths. The number of sources and their positions in the array are varied, and the influence of these variations on the primary and secondary hot spots is observed.

The measured electrical properties of normal and malignant human tissues from 50 to 900 MHz.

The electrical conductivity and relative permittivity of malignant and normal human tissues were measured at frequencies from 50 to 900 MHz. The measurements were made between 23 and 25 degrees C using a network analyzer connected to a flat-ended coaxial probe that was pressed against the freshly excised tissue samples. The malignant tissues were of the following normal tissue origin: bladder, colon, kidney, liver, lung, lymph nodes, mammary gland, spleen, and testes.

Theoretical and measured electric field distributions within an annular phased array: consideration of source antennas.

The magnitude of E-field patterns generated by an annular array prototype device has been calculated and measured. Two models were used to describe the radiating sources: a simple linear dipole and a stripline antenna model. The stripline model includes detailed geometry of the actual antennas used in the prototype and an estimate of the antenna current based on microstrip transmission line theory.

Modelling aperture antennas in the near- and far-field regions using subarrays of equivalent uniformly illuminated apertures.

This paper develops and presents an application of Huygen's principle herein referred to as the equivalent uniformly illuminated aperture method (EUAM). This method is used to predict the E-field patterns of aperture antennas in both the near- and far-field regions. In applying this method the radiating aperture is mathematically replaced by an array of smaller, uniformly illuminated aperture sources.

On the accuracy of noninvasive thermometry using molecular diffusion magnetic resonance imaging.

Temperature measurement using magnetic resonance imaging (MRI) of water self-diffusion is investigated. Diffusion images and derived temperatures are obtained in polyacrylamide gel phantom. The temperatures measured from MRI are compared with those from temperature probes to verify their accuracy.

Immunomagnetic purging of breast cancer from bone marrow for autologous transplantation.

Intensive chemotherapy with autologous bone marrow transplantation is a promising approach for the treatment of breast cancer, provided that clonogenic tumor cells do not contaminate the patient's bone marrow. We have previously demonstrated that a combination of 4-hydroperoxycyclophosphamide (4-HC) and immunomagnetic purging (IMP) with monoclonal antibodies and microspheres could remove 4-5 logs of clonogenic breast cancer cells from a 10-fold excess of human bone marrow cells. In the present report we have evaluated an apparatus for separating tumor cells from a large volume of human marrow.

Prediction of heating patterns of a microwave interstitial antenna array at various insertion depths.

Measurements made on the interstitial microwave antennas used for hyperthermia cancer therapy indicate that the heating patterns vary with the insertion depths (defined as the distance from the antenna tip to air-tissue interface). The antennas are made of thin coaxial cables with a radiation gap or gaps on the outer conductor. The antennas are inserted into small polypropylene catheters implanted in the tumour volume.

Heating patterns generated by phase modulation of a hexagonal array of interstitial antennas.

In this paper, we investigate an array of six interstitial microwave antennas used for hyperthermia cancer treatment. The purpose is to generate both uniform and controlled nonuniform heating patterns in biological tissue by phase modulating the signals applied to each antenna. The array consists of six antennas positioned on the corners of a hexagon.

A comparison using tissue electrical properties and temperature rise to determine relative absorption of microwave power in malignant tissue.

This paper compares two methods for determining the radio frequency absorbed power in tissue: from the measured electrical properties of the tissue, and from the induced temperature rise per unit time. In previous research, we measured the ratio frequency electrical properties of muscle, mammary gland, and malignant mammary tissue (SMT-2A mammary adenocarcinoma) in female W/Fu isogeneic rats. From those measurements we calculated for each tissue the power absorption versus frequency, and formed the ratio of malignant-to-normal power absorption.

Multiple power-density windows and their possible origin.

We have previously reported that in vitro exposure of chick forebrain tissue to 50-MHz radiofrequency (RF) electromagnetic radiation, amplitude modulated (AM) at 16 Hz, would enhance the efflux of calcium ions within only two power-density ranges: one from 1.44 to 1.67 mW/cm2, and the other including 3.

Lack of effects from 2000-Hz magnetic fields on mammary adenocarcinoma and reproductive hormones in rats.

Female rats were implanted with mammary adenocarcinoma tissue and 25 days later exposed to 2,000-Hz magnetic fields 1 h a day for 9 days. Analysis showed that tumor weights and the levels of several reproductive hormones were not significantly different between treated and control animals. Other studies with a similar design have also reported no significant effects from magnetic field exposure.

Effect of ambient levels of power-line-frequency electric fields on a developing vertebrate.

Fertilized eggs of Gallus domesticus were exposed continuously during their 21-day incubation period to either 50- or 60-Hz sinusoidal electric fields at an average intensity of 10 Vrms/m. The exposure apparatus was housed in an environmental room maintained at 37 degrees C and 55-60% relative humidity (RH). Within 1.

Experimental method for the hyperthermic treatment of cells in tissue culture: initial application to pancreatic cancer cells.

Hyperthermia is attractive as a potential adjunctive modality in the treatment of cancer, especially those cancers that are more resistant to conventional modalities. In the present study, we characterized the response of two pancreatic cancer cell lines to hyperthermia alone. In so doing, we utilized and characterized a novel exposure system that heats by 915-MHz continuous wave microwave (MW) radiation, with microprocessor control of the power input via temperature monitoring of the sample and simultaneous visualization and recording of temperature parameters.

Characteristics of transverse electric and magnetic field transmission cells at extremely low frequencies.

Transverse electric and magnetic field (TEM) cells are often designed to subject samples to electromagnetic radiation of intrinsic impedance (E/H) that is the same as in free space, 377 omega. Earlier work has shown this value to be correct for the RF region above about 2 kHz. In this study, measurements of magnetic fields in the extremely low frequency regions and at DC indicate the E/H ratio to be around 300 omega for frequencies less than 2 kHz in cells of a particular design.

Measurement of small mechanical vibrations of brain tissue exposed to extremely-low-frequency electric fields.

Electromagnetic fields can interact with biological tissue both electrically and mechanically. This study investigated the mechanical interaction between brain tissue and an extremely-low-frequency (ELF) electric field by measuring the resultant vibrational amplitude. The exposure cell is a section of X-band waveguide that was modified by the addition of a center conductor to form a small TEM cell within the waveguide structure.

Off-center spherical model for dosimetry calculations in chick brain tissue.

This paper presents calculations for the electric field and absorbed power density distribution in chick brain tissue inside a test tube, using an off-center spherical model. It is shown that the off-center spherical model overcomes many of the limitations of the concentric spherical model, and permits a more realistic modeling of the brain tissue as it sits in the bottom of the test tube surrounded by buffer solution. The effect of the unequal amount of buffer solution above the upper and below the lower surfaces of the brain is analyzed.