Search

This paper describes a preclinical investigation of the feasibility of thermotherapy treatment of bladder cancer with magnetic fluid hyperthermia (MFH), performed by analysing the thermal dosimetry of nanoparticle heating in a rat bladder model.The bladders of 25 female rats were instilled with magnetite-based nanoparticles, and hyperthermia was induced using a novel small animal magnetic field applicator (Actium Biosystems, Boulder, CO). We aimed to increase the bladder lumen temperature to 42 °C in10 min and maintain that temperature for 60 min. Temperatures were measured within the bladder lumen and throughout the rat with seven fibre-optic probes (OpSens Technologies, Quebec, Canada). An MRI analysis was used to confirm the effectiveness of the catheterisation method to deliver and maintain various nanoparticle volumes within the bladder. Thermal dosimetry measurements recorded the temperature rise of rat tissues for a variety of nanoparticle exposure conditions.Thermal dosimetry data demonstrated our ability to raise and control the temperature of rat bladder lumen ≥1 °C/min to a steady state of 42 °C with minimal heating of surrounding normal tissues. MRI scans confirmed the homogenous nanoparticle distribution throughout the bladder.These data demonstrate that our MFH system with magnetite-based nanoparticles provides well-localised heating of rat bladder lumen with effective control of temperature in the bladder and minimal heating of surrounding tissues.

The aim of this study was to determine the kinematic viscosity of human urine and factors associated with its variability. This value is necessary for accurate modelling of fluid mechanics and heat transfer during hyperthermia treatments of bladder cancer.Urine samples from 64 patients undergoing routine clinical testing were subject to dipstick urinalysis and measurement of viscosity with a Cannon-Fenske viscometer. Viscosity measurements were taken at relevant temperatures for hyperthermia studies: 20 °C (room temperature), 37 °C (body temperature), and 42 °C (clinical hyperthermia temperature). Factors that might affect viscosity were assessed, including glucosuria, haematuria, urinary tract infection status, ketonuria and proteinuria status. The correlation of urine specific gravity and viscosity was measured with Spearman's rho.Urine kinematic viscosity at 20 °C was 1.0700 cSt (standard deviation (SD) = 0.1076), at 37 °C 0.8293 cSt (SD = 0.0851), and at 42 °C 0.6928 cSt (SD = 0.0247). Proteinuria appeared to increase urine viscosity, whereas age, gender, urinary tract infection, glucosuria, ketonuria, and haematuria did not affect it. Urine specific gravity was only modestly correlated with urine viscosity at 20 °C (rho = 0.259), 37 °C (rho = 0.266), and 42 °C (rho = 0.255).The kinematic viscosity of human urine is temperature dependent and higher than water. Urine specific gravity was not a good predictor of viscosity. Of factors that might affect urine viscosity, only proteinuria appeared to be clinically relevant. Estimates of urine viscosity provided in this manuscript may be useful for temperature modelling of bladder hyperthermia treatments with regard to correct prediction of the thermal conduction effects.

We present a technique for fabricating realistic breast phantoms for microwave imaging experiments. Using oil-in-gelatin dispersions that mimic breast tissue dielectric properties at microwave frequencies, we constructed four heterogeneous phantoms spanning the full range of volumetric breast densities. We performed CT scans and dielectric properties measurements to characterize each phantom.

The experimental results reported in this letter suggest that single-walled carbon nanotubes (SWCNTs) have the potential to enhance dielectric contrast between malignant and normal tissue for microwave detection of breast cancer and facilitate selective heating of malignant tissue for microwave hyperthermia treatment of breast cancer. In this study, we constructed tissue-mimicking materials with varying concentrations of SWCNTs and characterized their dielectric properties and heating response. At SWCNT concentrations of less than 0.5% by weight, we observed significant increases in the relative permittivity and effective conductivity. In microwave heating experiments, we observed significantly greater temperature increases in mixtures containing SWCNTs. These temperature increases scaled linearly with the effective conductivity of the mixtures. This work is a first step towards the development of functionalized, tumor-targeting SWCNTs as theranostic (integrated therapeutic and diagnostic) agents for microwave breast cancer detection and treatment.

We are investigating the feasibility of single-walled carbon nanotubes (SWCNTs) as contrast agents for microwave breast cancer detection. We hypothesize that the accumulation of SWCNTs in a tumor will enhance the dielectric contrast between normal and malignant tissue and potentially improve the efficacy of microwave imaging techniques. As an initial step, we constructed tissue-mimicking phantom materials with varying concentrations of SWCNTs. We characterized their dielectric properties and estimated the pressure wave induced in the phantom materials under microwave illumination. At SWCNT concentrations of less than 0.5% by weight, we observed significant changes in both the relative permittivity and effective conductivity of these SWCNT/tissue-mimicking material mixtures. Our estimates suggest a similarly significant change in the thermoacoustic response relative to the phantom material mixtures without carbon nanotubes.

Microwave-induced thermoacoustic tomography (MI-TAT) is an imaging technique that exploits dielectric contrast at microwave frequencies while creating images with ultrasound resolution. We propose the use of microbubbles as a dielectric contrast agent for enhancing the sensitivity of MI-TAT for breast cancer detection. As an initial investigation of this concept, we experimentally studied the extent to which the microwave-induced thermoacoustic response of a dielectric target is modified by the presence of air-filled glass microbubbles. We created mixtures of ethylene glycol with varying weight percentages of microbubbles and characterized both their microwave properties (0.5-6 GHz) and thermoacoustic response when irradiated with microwave energy at 3 GHz. Our data shows that the microbubbles considerably lowered the relative permittivity, electrical conductivity, and thermoacoustic response of the ethylene glycol mixtures. We hypothesize that the interstitial infusion of microbubbles to a tumor site will similarly create a smaller thermoacoustic response compared to the pre-contrast-agent response, thereby enhancing sensitivity through the use of differential imaging techniques.

Summary form only given. Microfabrication techniques used for MEMS offer promising advantages for fabrication of mm-wave and THz vacuum electronic devices (/spl mu/VEDs). This paper describes results of an exploratory investigation of several microfabrication methods considered candidates for production of circuits or circuit components for mm-wave and THz TWTs. The processes investigated have included LIGA, hot embossing (polymer micromolding), and deep reactive ion etching (DRIE). The circuits and circuit components investigated have included folded waveguides (FWGs), gratings, resistive wall amplifiers, and novel attenuators for FWG TWTs. We present and discuss the results of the microfabrication experiments, the design analyses, and their implications for advanced mm-wave and THz /spl mu/VEDs.