Dr. Dario B. Rodrigues Profile

Dr. Dario B. Rodrigues

Postdoctoral Research Fellow at Jefferson

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Publications (3)

Proceedings Article | 22 February 2017 Paper

Using a conformal water bolus to adjust heating patterns of microwave waveguide applicators

Paul Stauffer, Dario Rodrigues, Randolf Sinahon, Lyndsey Sbarro, Valeria Beckhoff, Mark Hurwitz

Proceedings Volume 10066, 100660N (2017) https://doi.org/10.1117/12.2252208

KEYWORDS: Waveguides, Microwave radiation, Tissues, Antennas, Cancer, Heat treatments, Electromagnetism, Synthetic aperture radar, Tumors, Device simulation, Skin, Dielectrics

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Background: Hyperthermia, i.e., raising tissue temperature to 40-45°C for 60 min, has been demonstrated to increase the effectiveness of radiation and chemotherapy for cancer. Although multi-element conformal heat applicators are under development to provide more adjustable heating of contoured anatomy, to date the most often used applicator to heat superficial disease is the simple microwave waveguide. With only a single power input, the operator must be resourceful to adjust heat treatment to accommodate variable size and shape tumors spreading across contoured anatomy. Methods: We used multiphysics simulation software that couples electromagnetic, thermal and fluid dynamics physics to simulate heating patterns in superficial tumors from commercially available microwave waveguide applicators. Temperature distributions were calculated inside homogenous muscle and layered skin-fat-muscle-tumor-bone tissue loads for a typical range of applicator coupling configurations and size of waterbolus. Variable thickness waterbolus was simulated as necessary to accommodate contoured anatomy. Physical models of several treatment configurations were constructed for comparison of simulation results with experimental specific absorption rate (SAR) measurements in homogenous muscle phantom. Results: Accuracy of the simulation model was confirmed with experimental SAR measurements of three unique applicator setups. Simulations demonstrated the ability to generate a wide range of power deposition patterns with commercially available waveguide antennas by controllably varying size and thickness of the waterbolus layer. Conclusion: Heating characteristics of 915 MHz waveguide antennas can be varied over a wide range by controlled adjustment of microwave power, coupling configuration, and waterbolus lateral size and thickness. The uniformity of thermal dose delivered to superficial tumors can be improved by cyclic switching of waterbolus thickness during treatment to proactively shift heat peaks and nulls around under the aperture, thereby reducing patient pain while increasing minimum thermal dose by end of treatment.

Proceedings Article | 26 February 2013 Paper

Stable microwave radiometry system for long term monitoring of deep tissue temperature

Paul Stauffer, Dario Rodriques, Sara Salahi, Erdem Topsakal, Tiago Oliveira, Aniruddh Prakash, Fabio D’Isidoro, Douglas Reudink, Brent Snow, Paolo Maccarini

Proceedings Volume 8584, 85840R (2013) https://doi.org/10.1117/12.2003976

KEYWORDS: Tissues, Antennas, Brain, Radiometry, Kidney, Sensors, Temperature metrology, Skull, Skin, Liquids

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Background: There are numerous clinical applications for non-invasive monitoring of deep tissue temperature. We present the design and experimental performance of a miniature radiometric thermometry system for measuring volume average temperature of tissue regions located up to 5cm deep in the body. Methods: We constructed a miniature sensor consisting of EMI-shielded log spiral microstrip antenna with high gain onaxis and integrated high-sensitivity 1.35GHz total power radiometer with 500 MHz bandwidth. We tested performance of the radiometry system in both simulated and experimental multilayer phantom models of several intended clinical measurement sites: i) brown adipose tissue (BAT) depots within 2cm of the skin surface, ii) 3-5cm deep kidney, and iii) human brain underlying intact scalp and skull. The physical models included layers of circulating tissue-mimicking liquids controlled at different temperatures to characterize our ability to quantify small changes in target temperature at depth under normothermic surface tissues. Results: We report SAR patterns that characterize the sense region of a 2.6cm diameter receive antenna, and radiometric power measurements as a function of deep tissue temperature that quantify radiometer sensitivity. The data demonstrate: i) our ability to accurately track temperature rise in realistic tissue targets such as urine refluxed from prewarmed bladder into kidney, and 10°C drop in brain temperature underlying normothermic scalp and skull, and ii) long term accuracy and stability of +0.4°C over 4.5 hours as needed for monitoring core body temperature over extended surgery or monitoring effects of brown fat metabolism over an extended sleep/wake cycle. Conclusions: A non-invasive sensor consisting of 2.6cm diameter receive antenna and integral 1.35GHz total power radiometer has demonstrated sufficient sensitivity to track clinically significant changes in temperature of deep tissue targets underlying normothermic surface tissues for clinical applications like the detection of vesicoureteral reflux, and long term monitoring of brown fat metabolism or brain core temperature during extended surgery.

Proceedings Article | 26 February 2013 Paper

Numerical 3D modeling of heat transfer in human tissues for microwave radiometry monitoring of brown fat metabolism

Dario Rodrigues, Paolo Maccarini, Sara Salahi, Erin Colebeck, Erdem Topsakal, Pedro Pereira, Paulo Limão-Vieira, Paul Stauffer

Proceedings Volume 8584, 85840S (2013) https://doi.org/10.1117/12.2004931

KEYWORDS: Antennas, Tissues, Mode conditioning cables, 3D modeling, Radiometry, Skin, Temperature metrology, Microwave radiation, Dielectrics, Microwave radiometry

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