Prof. Paul R. Stauffer Profile

Prof. Paul R. Stauffer

Professor at Jefferson

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Author

Publications (18)

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

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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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

Preclinical dosimetry of magnetic fluid hyperthermia for bladder cancer

Tiago Oliveira, Paul Stauffer, Chen-Ting Lee, Chelsea Landon, Wiguins Etienne, Paolo Maccarini, Brant Inman, Mark Dewhirst

Proceedings Volume 8584, 85840D (2013) https://doi.org/10.1117/12.2005623

KEYWORDS: Bladder, Magnetism, Nanoparticles, Magnetic resonance imaging, Tissues, Temperature metrology, Bladder cancer, In vivo imaging, Control systems, Iron

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Proceedings Article | 23 February 2011 Paper

Microwave radiometry for non-invasive detection of vesicoureteral reflux (VUR) following bladder warming

Paul Stauffer, Paolo Maccarini, Kavitha Arunachalam, Valeria De Luca, Sara Salahi, Alina Boico, Oystein Klemetsen, Yngve Birkelund, Svein Jacobsen, Fernando Bardati, Piero Tognolotti, Brent Snow

Proceedings Volume 7901, 79010V (2011) https://doi.org/10.1117/12.875636

KEYWORDS: Antennas, Bladder, Tissues, Kidney, Radiometry, Temperature metrology, Synthetic aperture radar, Skin, In vivo imaging, Modulation

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Proceedings Article | 25 February 2009 Paper

Clinical utility of magnetic resonance thermal imaging (MRTI) for realtime guidance of deep hyperthermia

P. Stauffer, Oana Craciunescu, P. Maccarini, Cory Wyatt, K. Arunachalam, O. Arabe, V. Stakhursky, B. Soher, J. MacFall, Z. Li, William Joines, S. Rangarao, K. Cheng, S. Das, Carlos Martins, Cecil Charles, Mark Dewhirst, T. Wong, E. Jones, Z. Vujaskovic

Proceedings Volume 7181, 71810I (2009) https://doi.org/10.1117/12.812188

KEYWORDS: Tumors, Magnetic resonance imaging, Tissues, Temperature metrology, Antennas, Magnetism, Phased arrays, Sensors, Fiber optics sensors, Breast

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Proceedings Article | 24 February 2009 Paper

Size reduction and radiation pattern shaping of multi-fed DCC slot antennas used in conformal microwave array hyperthermia applicators

Paolo Maccarini, Kavitha Arunachalam, Carlos Martins, Paul Stauffer

Proceedings Volume 7181, 718107 (2009) https://doi.org/10.1117/12.809952

KEYWORDS: Antennas, Microwave radiation, Synthetic aperture radar, Tissues, Amplifiers, Skin, Tumors, Near field, Chest, Neck

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The use of conformal antenna array in the treatment of superficial diseases can significantly increase patient comfort while enhancing the local control of large treatment area with irregular shapes. Originally a regular square multi-fed slot antenna (Dual Concentric Conductor - DCC) was proposed as basic unit cell of the array. The square DCC works well when the outline of the treatment area is rectangular such as in the main chest or back area but is not suitable to outline diseases spreading along the armpit and neck area. In addition as the area of the patch increases, the overall power density decreases affecting the efficiency and thus the ability to deliver the necessary thermal dose with medium power amplifier (<50W). A large number of small efficient antennas is preferable as the disease is more accurately contoured and the lower power requirement for the amplifiers correlates with system reliability, durability, linearity and overall reduced cost. For such reason we developed a set of design rules for multi-fed slot antennas with irregular contours and we implemented a design that reduce the area while increasing the perimeter of the slot, thus increasing the antenna efficiency and the power density. The simulation performed with several commercial packages (Ansoft HFSS, Imst Empire, SemcadX and CST Microwave Studio) show that the size reducing method can be applied to several shapes and for different frequencies. The SAR measurements of several DCCs are performed using an in-house high resolution scanning system with tumor equivalent liquid phantom both at 915 MHz for superficial hyperthermia systems in US) and 433 MHz (Europe). The experimental results are compared with the expected theoretical predictions and both simulated and measured patterns of single antennas of various size and shapes are then summed in various combinations using Matlab to show possible treatment irregular contours of complex diseases. The local control is expected to significantly improve while maintaining the patient comfort.

Proceedings Article | 12 February 2009 Paper

Progress on thermobrachytherapy surface applicator for superficial tissue disease

Kavitha Arunachalam, Oana Craciunescu, Paolo Maccarini, Jaime Schlorff, Edward Markowitz, Paul Stauffer

Proceedings Volume 7181, 71810C (2009) https://doi.org/10.1117/12.809493

KEYWORDS: Tissues, Antennas, High dynamic range imaging, Fluid dynamics, Natural surfaces, Chest, Water, Thermometry, Breast cancer, Infrared cameras

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Proceedings Article | 12 February 2009 Paper

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

Kung-Shan Cheng, Yu Yuan, Zhen Li, Paul Stauffer, William Joines, Mark Dewhirst, Shiva Das

Proceedings Volume 7181, 71810F (2009) https://doi.org/10.1117/12.808499

KEYWORDS: Tumors, Tissues, Blood, Antennas, Feedback control, Device simulation, Thermal modeling, Systems modeling, Bone, HVAC controls

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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. Methods: We impose a piecewise linear approximation to a set of heat pulses, each consisting of a 1-min heat-up, followed by a 2-min cool-down. The controller is designed for feedback from magnetic resonance temperature images (MRTI) obtained after each iteration of heat pulses to adjust the projected optimal setting of antenna phase and magnitude for selective tumor heating. Simulated temperature patterns with additive Gaussian noise with a standard deviation of 1.0°C and zero mean were used as a surrogate for MRTI. Robustness tests were conducted numerically for a patient's right leg placed at the middle of a water bolus surrounded by a 10-antenna applicator driven at 150 MHz. Robustness tests included added discrepancies in perfusion, electrical and thermal properties, and patient model simplifications. Results: The controller improved selective tumor heating after an average of 4-9 iterative adjustments of power and phase, and fulfilled satisfactory therapeutic outcomes with approximately 75% of tumor volumes heated to temperatures >43°C while maintaining about 93% of healthy tissue volume < 41°C. Adequate sarcoma heating was realized by using only 2 to 3 VSs rather than a much larger number of control signals for all 10 antennas, which reduced the convergence time to only 4 to 9% of the original value. Conclusions: Using a piecewise linear approximation to a set of heat pulses in a VS reduced-order controller, the proposed algorithm greatly improves the efficiency of hyperthermic treatment of leg sarcomas while accommodating practical nonlinear variation of tissue properties such as perfusion.

Proceedings Article | 9 February 2007 Paper

Progress on conformal microwave array applicators for heating chestwall disease

P. Stauffer, P. Maccarini, T. Juang, S. Jacobsen, C. Gaeta, J. Schlorff, A. Milligan

Proceedings Volume 6440, 64400E (2007) https://doi.org/10.1117/12.701389

KEYWORDS: Antennas, Microwave radiation, Sensors, Tissues, Temperature metrology, Computer aided design, Natural surfaces, Synthetic aperture radar, Dielectrics, Fiber optics sensors

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Previous studies have reported the computer modeling, CAD design, and theoretical performance of single and multiple antenna arrays of Dual Concentric Conductor (DCC) square slot radiators driven at 915 and 433 MHz. Subsequently, practical CAD designs of microstrip antenna arrays constructed on thin and flexible printed circuit board (PCB) material were reported which evolved into large Conformal Microwave Array (CMA) sheets that could wrap around the surface of the human torso for delivering microwave energy to large areas of superficial tissue. Although uniform and adjustable radiation patterns have been demonstrated from multiple element applicators radiating into simple homogeneous phantom loads, the contoured and heterogeneous tissue loads typical of chestwall recurrent breast cancer have required additional design efforts to achieve good coupling and efficient heating from the increasingly larger conformal array applicators used to treat large area contoured patient anatomy. Thus recent work has extended the theoretical optimization of DCC antennas to improve radiation efficiency of each individual aperture and reduce mismatch reflections, radiation losses, noise, and cross coupling of the feedline distribution network of large array configurations. Design improvements have also been incorporated into the supporting bolus structure to maintain effective coupling of DCC antennas into contoured anatomy and to monitor and control surface temperatures under the entire array. New approaches for non-invasive monitoring of surface and sub-surface tissue temperatures under each independent heat source are described that make use of microwave radiometry and flexible sheet grid arrays of thermal sensors. Efforts to optimize the clinical patient interface and move from planar rectangular shapes to contoured vest applicators that accommodate entire disease in a larger number of patients are summarized. By applying heat more uniformly to large areas of contoured anatomy, the CMA applicator resulting from these enhancements should expand the number of patients that can benefit from effective heating of superficial disease in combination with radiation or chemotherapy.

Proceedings Article | 14 April 2005 Paper

Progress on system for applying simultaneous heat and brachytherapy to large-area surface disease

Paul Stauffer, Jaime Schlorff, Titania Juang, Daniel Neuman, Jessi Johnson, Paolo Maccarini, Jean Pouliot

Proceedings Volume 5698, (2005) https://doi.org/10.1117/12.594937

KEYWORDS: Microwave radiation, Antennas, Skin, Tumors, Tissues, High dynamic range imaging, Natural surfaces, Temperature metrology, Radiotherapy, Fiber optics

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Laboratory experiments have shown that thermal enhancement of radiation response increases substantially for higher thermal dose (approaching 100 CEM43) and when hyperthermia and radiation are delivered simultaneously. Unfortunately, equipment capable of delivering uniform doses of heat and radiation simultaneously has not been available to test the clinical potential of this approach. We present recent progress on the clinical implementation of a system that combines the uniform heating capabilities of flexible printed circuit board microwave array applicators with an array of brachytherapy catheters held a fixed distance from the skin for uniform radiation of tissue <1.5 cm deep with a scanning high dose rate (HDR) brachytherapy source. The system is based on the Combination Applicator which consists of an array of up to 32 Dual Concentric Conductor (DCC) apertures driven at 915 MHz for heating tissue, coupled with an array of 1 cm spaced catheters for HDR therapy. Efforts to optimize the clinical interface and move from rectangular to more complex shape applicators that accommodate the entire disease in a larger number of patients are described. Improvements to the system for powering and controlling the applicator are also described. Radiation dosimetry and experimental performance results of a prototype 15 x 15 cm dual-purpose applicator demonstrate dose distributions with good homogeneity under large contoured surfaces typical of diffuse chestwall recurrence of breast carcinoma. Investigations of potential interaction between heat and brachytherapy components of a Combination Applicator demonstrate no perceptible perturbation of the heating field from an HDR source or leadwire, no perceptible effect of a scanning HDR source on fiberoptic thermometry, and <0.5% variation of radiation dose delivered through the CMA applicator. By applying heat and radiation simultaneously for maximum synergism of modalities, this dual therapy system should expand the number of patients that can benefit from effective thermoradiotherapy treatments.

Proceedings Article | 14 April 2005 Paper

Electromagnetic optimization of dual-mode antennas for radiometry-controlled heating of superficial tissue

Paolo Maccarini, Hans Rolfsnes, Daniel Neuman, Jessi Johnson, Titania Juang, Svein Jacobsen, Paul Stauffer

Proceedings Volume 5698, (2005) https://doi.org/10.1117/12.592507

KEYWORDS: Antennas, Tissues, Synthetic aperture radar, Microwave radiation, Metals, Tumors, Dielectrics, Electromagnetism, Radiometry, Temperature metrology

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The large variance of survival in the treatment of large superficial tumors indicates that the efficacy of current therapies can be dramatically improved. Hyperthermia has shown significant enhancement of response when used in combination with chemotherapy and/or radiation. Control of temperature is a critical factor for treatment quality (and thus effectiveness), since the response of tumor and normal cells is significantly different over a range of just a few degrees (41-45°). For diffuse spreading tumors, microwave conformal arrays have been shown to be a sound solution to deposit the power necessary to reach the goal temperature throughout the targeted tissue. Continuous temperature monitoring is required for feedback control of power to compensate for physiologic (e.g. blood perfusion and dielectric properties) changes. Microwave radiometric thermometry has been proposed to complement individual fluoroptic probes to non-invasively map superficial and sub-surface temperatures. The challenge is to integrate the broadband antenna used for radiometric sensing with the high power antenna used for power deposition. A modified version of the dual concentric conductor antenna presented previously is optimized for such use. Several design challenges are presented including preventing unwanted radiating modes and thermal and electromagnetic coupling between the two antennas, and accommodating dielectric changes of the target tissue. Advanced 3D and planar 2D simulation software are used to achieve an initial optimized design, focused on maintaining appropriate radiation efficiency and pattern for both heating and radiometry antennas. A cutting edge automated measurement system has been realized to characterize the antennas in a tissue equivalent material and to confirm the simulation results. Finally, the guidelines for further development and improvement of this initial design are presented together with a preliminary implementation of the feedback program to be used to control the temperature distribution in variable, inhomogeneous tissue.

Proceedings Article | 1 June 2001 Paper

Microwave array applicator for radiometry-controlled superficial hyperthermia

Paul Stauffer, Svein Jacobsen, Daniel Neuman

Proceedings Volume 4247, (2001) https://doi.org/10.1117/12.427866

KEYWORDS: Antennas, Temperature metrology, Radiometry, Synthetic aperture radar, Tissues, Microwave radiation, Copper, Connectors, Natural surfaces, Skin

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Proceedings Article | 24 January 2000 Open Access

Thermal therapy techniques for skin and superficial tissue disease

Paul Stauffer

Proceedings Volume 10297, 102970E (2000) https://doi.org/10.1117/12.375215

KEYWORDS: Skin, Tissues, Laser therapeutics, Cancer, Melanoma, Surgery, Radiotherapy

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Proceedings Article | 19 May 1999 Paper

Dual-mode antenna array for microwave heating and noninvasive thermometry of superficial tissue disease

Paul Stauffer, Svein Jacobsen, Francesca Rossetto, Chris Diederich, Daniel Neuman

Proceedings Volume 3594, (1999) https://doi.org/10.1117/12.348732

KEYWORDS: Antennas, Tissues, Synthetic aperture radar, Microwave radiation, Copper, Connectors, Temperature metrology, Thermometry, Radiometry, Natural surfaces

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Proceedings Article | 2 April 1998 Paper

Implantable microwave antennas for thermal therapy

Paul Stauffer

Proceedings Volume 3249, (1998) https://doi.org/10.1117/12.304359

KEYWORDS: Antennas, Tissues, Microwave radiation, Tumors, Synthetic aperture radar, Brain, Natural surfaces, Dielectrics, Silicon, Temperature metrology

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