Overview of bladder heating technology: matching capabilities with clinical requirements.

Moderate temperature hyperthermia (40-45°C for 1 h) is emerging as an effective treatment to enhance best available chemotherapy strategies for bladder cancer. A rapidly increasing number of clinical trials have investigated the feasibility and efficacy of treating bladder cancer with combined intravesical chemotherapy and moderate temperature hyperthermia. To date, most studies have concerned treatment of non-muscle-invasive bladder cancer (NMIBC) limited to the interior wall of the bladder. Following the promising results of initial clinical trials, investigators are now considering protocols for treatment of muscle-invasive bladder cancer (MIBC). This paper provides a brief overview of the devices and techniques used for heating bladder cancer. Systems are described for thermal conduction heating of the bladder wall via circulation of hot fluid, intravesical microwave antenna heating, capacitively coupled radio-frequency current heating, and radiofrequency phased array deep regional heating of the pelvis. Relative heating characteristics of the available technologies are compared based on published feasibility studies, and the systems correlated with clinical requirements for effective treatment of MIBC and NMIBC

Numerical investigation of novel microwave applicators based on zero-order mode resonance for hyperthermia treatment of cancer

This paper characterizes three novel microwave applicators based on zero-order mode resonators for use in hyperthermia treatment of cancer. The radiation patterns are studied with numerical simulations in muscle tissue-equivalent model at 434 MHz. The relative performance of the applicators is compared in terms of reflection coefficient, current distribution, power deposition (SAR) pattern, effective field size in 2D and 3D tissue volumes, and penetration depth. One particular configuration generated the most uniform SAR pattern, with 25% SAR covering 84 % of the treatment volume extending to 1 cm depth under the aperture, while remaining above 58% coverage as deep as 3 cm under the aperture. Recommendations are made to further optimize this structure

Novel Microwave Applicators Based on Zero-Order Mode Resonance for Hyperthermia Treatment of Cancer

In this paper, three novel microwave applicator prototypes based on zero-order mode resonators are proposed for use in hyperthermia treatment of cancer. The ability of all three applicators to homogenously irradiate muscle tissue-equivalent phantoms is demonstrated with results of numerical simulations, and relative performance of the applicators is compared

Utility of Microwave Radiometry for Diagnostic and Therapeutic Applications of Non-Invasive Temperature Monitoring

This paper describes the use of microwave radiometry for several diagnostic and therapeutic applications that can benefit from accurate non-invasive measurement of volume average temperature of tissue regions extending 4cm or more into the body. Design features are summarized for an appropriate high sensitivity long term stable system with 2.5 and 7 cm diameter receive antennas and integral 1.35 GHz total power radiometer electronics. Radiometer performance is characterized with electromagnetic and thermal simulations and experimental measurements in realistic models of two typical clinical applications. Results demonstrate sufficient sensitivity to track clinically significant changes in temperature of deep tissue targets for applications like the non-invasive detection of vesicoureteral reflux and monitoring brain “core” temperature during extended hypothermic surgery

Twin Ice Cores from Greenland Reveal History of Climate Change, More

Two projects conducted from 1989 to 1993 collected parallel ice cores—just 30 km apart— from the central part of the Greenland ice sheet. Each core is more than 3 km deep and extends back 110,000 years. In short, the ice cores tell a clear story: humans came of age agriculturally and industrially during the most stable climatic regime recorded in the cores. Change—large, rapid, and global—is more characteristic of the Earth\u27s climate than is stasis

Dielectric properties measurements of brown and white adipose tissue in rats from 0.5 to 10 GHz

Brown adipose tissue (BAT) plays an important role in whole body metabolism and with appropriate stimulus could potentially mediate weight gain and insulin sensitivity. Although imaging techniques are available to detect subsurface BAT, there are currently no viable methods for continuous acquisition of BAT energy expenditure. Microwave (MW) radiometry is an emerging technology that allows the quantification of tissue temperature variations at depths of several centimeters. Such temperature differentials may be correlated with variations in metabolic rate, thus providing a quantitative approach to monitor BAT metabolism. In order to optimize MW radiometry, numerical and experimental phantoms with accurate dielectric properties are required to develop and calibrate radiometric sensors. Thus, we present for the first time, the characterization of relative permittivity and electrical conductivity of brown (BAT) and white (WAT) adipose tissues in rats across the MW range 0.5-10GHz. Measurements were carried out in situ and post mortem in six female rats of approximately 200g. A Cole-Cole model was used to fit the experimental data into a parametric model that describes the variation of dielectric properties as a function of frequency. Measurements confirm that the dielectric properties of BAT (εr = 14.0-19.4, σ = 0.3-3.3S/m) are significantly higher than those of WAT (εr = 9.1-11.9, σ = 0.1-1.9S/m), in accordance with the higher water content of BAT

Tumor bed brachytherapy for locally advanced laryngeal cancer: a feasibility assessment of combination with ferromagnetic hyperthermia

Purpose. To assess the feasibility of adding hyperthermia to an original method of organ-preserving brachytherapy treatment for locally advanced head and neck tumors. Methods and materials. The method involves organ-preserving tumor resection and adjunctive high-dose-rate (HDR) brachytherapy delivered via afterloading catheters. These catheters are embedded in a polymeric implant prepared intraoperatively to fill the resection cavity, allowing precise computer planning of dose distribution in the surrounding at-risk tumor bed tissue. Theoretical and experimental analyzes address the feasibility of heating the tumor bed implant by coupling energy from a 100 kHz magnetic field applied externally into ferromagnetic particles, which are uniformly distributed within the implant. The goal is to combine adjuvant hyperthermia (40 °C–45 °C) to at-risk tissue within 5 mm of the resection cavity for thermal enhancement of radiation and chemotherapy response. Results. A five-year relapse free survival rate of 95.8% was obtained for a select group of 48 male patients with T3N0M0 larynx tumors, when combining organ-preserving surgery with HDR brachytherapy from a tumor bed implant. Anticipating the need for additional treatment in patients with more advanced disease, a theoretical analysis demonstrates the ability to heat at-risk tissue up to 10 mm from the surface of an implant filled with magnetically coupled ferromagnetic balls. Using a laboratory induction heating system, it takes just over 2 min to increase the target tissue temperature by 10 °C using a 19% volume fraction of ferromagnetic spheres in a 2 cm diameter silicone implant. Conclusion. The promising clinical results of a 48 patient pilot study demonstrate the feasibility of a new organ sparing treatment for laryngeal cancer. Anticipating the need for additional therapy, theoretical estimations of potential implant heating are confirmed with laboratory experiments, preparing the way for future implementation of a thermobrachytherapy implant approach for organ-sparing treatment of locally advanced laryngeal cancer

Focused ultrasound for treatment of bone tumours.

PURPOSE: Focused ultrasound (FUS) is a modality with rapidly expanding applications across the field of medicine. Treatment of bone lesions with FUS including both benign and malignant tumours has been an active area of investigation. Recently, as a result of a successful phase III trial, magnetic resonance-guided FUS is now a standardised option for treatment of painful bone metastases. This report reviews the clinical applications amenable to treatment with FUS and provides background on FUS and image guidance techniques, results of clinical studies, and future directions. METHODS: A comprehensive literature search and review of abstracts presented at the recently completed fourth International Focused Ultrasound Symposium was performed. Case reports and older publications revisited in more recent studies were excluded. For clinical studies that extend beyond bone tumours, only the data regarding bone tumours are presented. RESULTS: Fifteen studies assessing the use of focused ultrasound in treatment of primary benign bone tumours, primary malignant tumours, and metastatic tumours meeting the search criteria were identified. For these clinical studies the responders group varied within 91-100%, 85-87% and 64-94%, respectively. Major complications were reported in the ranges 0%, 0-28% and 0-4% for primary benign, malignant and metastatic tumours, respectively. CONCLUSIONS: Image-guided FUS is both safe and effective in the treatment of primary and secondary tumours. Additional phase III trials are warranted to more fully define the role of FUS in treatment of both benign and malignant bone tumours

Optimization of Chest Wall Hyperthermia Treatment Using a Virtual Human Chest Model

This work explores different coupling configurations (direct contact, air and water coupling) between a single 915 MHz waveguide applicator and human tissue in the setting of chest wall recurrence (CWR) of breast cancer. The objective is to treat chest wall tumours with microwave hyperthermia, while avoiding hot spots in critical areas such as scars and ribs. The best coupling configuration was a customized 24×29 cm water bolus developed by our team. It helps the applicator deliver an effective field size of 268 cm2 at 1 cm depth and a penetration depth of 2-3 cm. Water bolus thickness can be adjusted during treatment (0.5-4 cm) to shift hot spot locations and thus homogenize thermal dose delivered over a 60 min hyperthermia treatment. The virtual human chest model is easily customized so it can be used as a tool for treatment planning and quality assurance testing of microwave applicator configurations

The Approximate Invariance of the Average Number of Connections for the Continuum Percolation of Squares at Criticality

We perform Monte Carlo simulations to determine the average excluded area $$of randomly oriented squares, randomly oriented widthless sticks and aligned squares in two dimensions. We find significant differences between our results for randomly oriented squares and previous analytical results for the same. The sources of these differences are explained. Using our results for$$ and Monte Carlo simulation results for the percolation threshold, we estimate the mean number of connections per object $B_c$ at the percolation threshold for squares in 2-D. We study systems of squares that are allowed random orientations within a specified angular interval. Our simulations show that the variation in $B_c$ is within 1.6% when the angular interval is varied from 0 to $\pi/2$