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User Conference Title Design and Analysis of Improved Hyperthermia Therapy Systems Zhen

2 Historical Background of Hyperthermia Hyperthermia: Induced heat for cancer therapy. Hyperthermia is a therapy in which tissue temperature is raised to 41 0 C or higher (approximately 42 0 C C) by external methods B.C, ancient Egypt, India, and Greece started to use heat to treat patients. Egypt: breast cancer patients were treated with immersion in hot water, or with a fire drill. India: a month-long program of heating by steam baths, feeding with oils and rice, and the administration of purgatives. Greek: physicians recommended the use of heat when surgery was not possible. Greek HYPER ("to raise") and THERME ("to heat") ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

4 Electromagnetic Heating Microwave-Induced Heating Principles Specific Absorption Rate (SAR) in W/kg: E SAR = σ 2ρ 2 Induced Temperature Rise ρc dt dt SAR Depth of Penetration: δ = = α ' 1 λ0 ε '' πε 2007 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary

5 Rationale and Technical Aspects of Clinical Hyperthermia Why high temperatures (hyperthermia) can be used to treat cancer. Differences in the blood supply and vasculature in tumors and normal tissues Differences in electrical properties of tumors and normal tissues Used with radiation therapy and chemotherapy. What type of tumors can be treated using hyperthermia? Sarcoma, melanoma, and cancers of the head and neck, brain, lung, esophagus, breast, bladder, rectum, liver, appendix, cervix, and peritoneal lining (mesothelioma). The different methods of hyperthermia Local hyperthermia: external (superficial), intraluminal or endocavitary, and interstitial Regional hyperthermia: deep tissue Whole body hyperthermia Side effects Higher temperatures may occur in various spots Burns, blisters, discomfort, or pain Most of these side effects are temporary 2007 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary

Power is turned on Relative temperature: Proton Resonance Frequency Shift (PRFS) MRI Real

6 A Leg Sarcoma Treatment & a Limb Applicator A typical course of clinical hyperthermia treatments 4-8 heating sessions spread over a period of several weeks 2 hours session Patient preparation Power is turned on Relative temperature: Proton Resonance Frequency Shift (PRFS) MRI Real temperature: optic fiber probes in invasive catheters 2007 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary

7 Motivation for Using Computer-aided Models Solving engineering problems: Design filters to prevent cross-talk between the limb applicator and the MRI machine. Design wide-band input impedance matching circuits to maximize the transmitted power. Solving clinical problems Provide better heating through treatment preplanning. Optimize setups for treatment cases ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary

8 Band Pass Filter Design Design an n = 3 half-wavelength tapped-stub filter which has Butterworth response with Q T = 10 and centered at f 0 = 200MHz. θ11 = θ13 = o θ21 = θ23 = o θ 12 = o θ 22 = o f0 = 200MHz BW = = 20MHz If this filter is constructed as microstrip on 1/16 inch epoxy-glass substrate which has 4.8 dielectric constant using 50-Ohm lines, and the filter is X = square inches ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary

9 Band Pass Filter Design: Size Reduction Replacing the open stubs with capacitors Replacing λ/4 transmission line by a series inductance and capacitors to ground 2007 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary

Band Pass Filter Design: Size Reduction Derive the new Q f 0 = 210.6 MHz, BW=14.43, Q T =14.6 f0 = 202.4MHz BW = 19.9MHz Q T = 10.

10 Band Pass Filter Design: Size Reduction Derive the new Q f 0 = MHz, BW=14.43, Q T =14.6 f0 = 202.4MHz BW = 19.9MHz Q T = Replace the remaining λ/4 transmission lines by a series inductance and capacitors to ground ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary

Size Reduction: 243.67 5.99 square inches Replacing the lumped inductors with the shortest possible length of transmission line. Z = 150Ω ot w = 0.152mm = 0.

11 Size Reduction: square inches Replacing the lumped inductors with the shortest possible length of transmission line. Z = 150Ω ot w = 0.152mm = 0.006inch ot v 1 ω0l0 lt = tan = 4.38cm = 1.73inches ω Z0t f0 = MHz BW = = 20MHz 2007 ANSYS, Inc. All rights reserved. 11 ANSYS, Inc. Proprietary

connected with a n=3 high pass filter 2007 ANSYS,

13 Filter Design for a MRI Compatible RF Hyperthermia System A designed board of n=3 band pass filter connected with a n=3 high pass filter 2007 ANSYS, Inc. All rights reserved. 13 ANSYS, Inc. Proprietary

Initial Analysis Based on Simplified Models for Homogeneous Medium A schematic diagram of the MAPA in HFSS Eight copper foil strip dipole antennas Connected in parallel pairs and printed on the inner

16 Initial Analysis Based on Simplified Models for Homogeneous Medium A schematic diagram of the MAPA in HFSS Eight copper foil strip dipole antennas Connected in parallel pairs and printed on the inner surface of a cylindrical plastic shell. Fed by coax cables Each cable has a stub for impedance matching 140 MHz Water cooling inside HFSS simulation results in the xy plane with different 4-channel phases 2007 ANSYS, Inc. All rights reserved. 16 ANSYS, Inc. Proprietary

17 Hotspot regions in the xy plane with different 4-channel phases At 140 MHz, in all simulations, the maximum local SAR was produced when all 4 inputs were in phase. When the four inputs were in phase, the local SAR was concentric within the applicator and approximately 9 cm diameter, with a maximum of 24.3 W/kg at the center. The SAR peak shifted away from the antennas with increased phase. Further increases in phase caused the energy to split into two separate regions. SAR can be adjusted to move a single 9 cm diameter focal hot spot within 75% of the array diameter by adjusting relative phase of four inputs ANSYS, Inc. All rights reserved. 17 ANSYS, Inc. Proprietary

Simulations in Realistic Models: Patient Body Model Patient body model can be made by utilizing computed tomography (CT) or other medical imaging methods.

18 Simulations in Realistic Models: Patient Body Model Patient body model can be made by utilizing computed tomography (CT) or other medical imaging methods. A anatomical reconstruction of a patient's leg with sarcoma inside. This figure is provided by Dr. Vadim Stakhursky 2007 ANSYS, Inc. All rights reserved. 18 ANSYS, Inc. Proprietary

19 Patient Body Model Place leg inside of the MAPA Tumor comes from CT data some detail has been removed in the model The tumor has been inserted in the correct location 2007 ANSYS, Inc. All rights reserved. 19 ANSYS, Inc. Proprietary

20 Electromagnetic Simulations in a Patient Body Model This is the Ansoft adult male body model, which has an accuracy at the millimeter level. Within this model, there are more than 300 objects inside to represent bones, muscles and organs. A material database with frequency-dependent materials is included ANSYS, Inc. All rights reserved. 20 ANSYS, Inc. Proprietary

22 Simulation Strategy 3D FEM EM simulator-hfss solves for field quantities in the area of interest. 3D FEM thermodynamic simulator-ephysics takes field inputs and provides temperature maps by solving bio-heat transfer equation in the area of interest ANSYS, Inc. All rights reserved. 22 ANSYS, Inc. Proprietary

Optimized Hyperthermia Treatment Planning How

Professor, Department of Radiation Oncology, Duke University Duke Electrical and Computer Engineering Department: John Stang, Steven Keller, Tao

26 Acknowledgements William T. Joines Professor, Department of Electrical and Computer Engineering, Duke University Paul R. Stauffer Director of Hyperthermia Physics Division. Professor, Department of Radiation Oncology, Duke University Duke Electrical and Computer Engineering Department: John Stang, Steven Keller, Tao Zhou Ansoft Corporation: Martin Vogel, Rob Holoboff Duke Radiation Oncology Department: Paolo Maccarini, Brian J. Soher, Omar Arabe, Vadim Stakhursky, Oana Craciunescu, James MacFall, Shiva Das ANSYS, Inc. All rights reserved. 26 ANSYS, Inc. Proprietary

Microwave Antennas for Medical Applications

Seoul, Korea 6 Sept. 27 Microwave Antennas for Medical Applications IEEE AP-S Distinguished Lecturer Koichi ITO Department of Medical System Engineering Chiba University, Japan k-ito@ieee.org Medical applications