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Treatment planning for capacitive regional hyperthermia
H Kroeze1, J B van de Kamer, A A C de Leeuw
1Department of Radiation Oncology, University Medical Centre Utrecht MS Q00.118, PO Box 85500, 3508 GA Utrecht, The Netherlands. h.kroeze@radth.med.uu.nl
Summary
Capacitively coupled hyperthermia treatment planning requires high-resolution simulation. This study developed a system for accurate modeling, revealing limitations of agar phantoms and highlighting the need to manage hot spots for effective deep-seated tumor heating.
Area of Science:
- Biomedical Engineering
- Medical Physics
- Computational Modeling
Background:
- Capacitively coupled hyperthermia (CCH) devices are prevalent, particularly in Asia.
- Accurate modeling of CCH treatments is crucial for effective patient care.
- Existing methods may not fully capture the complexities of heat distribution in vivo.
Purpose of the Study:
- To develop and validate a comprehensive treatment planning system for CCH.
- To investigate the accuracy of the quasi-static approximation for high-resolution electromagnetic modeling.
- To evaluate the efficacy of CCH for deep-seated pelvic tumors and compare in vivo modeling with phantom studies.
Main Methods:
- Developed a treatment planning system incorporating Specific Absorption Rate (SAR) and thermal models for CCH.
- Employed the quasi-static approximation for computationally efficient, high-resolution electromagnetic simulations.
- Validated the quasi-static approximation by comparing Maxwell solutions with phantom data.
- Modeled CCH for prostate cancer using a heterogeneous patient model.
Main Results:
- The quasi-static approximation provides accurate solutions with acceptable computational cost.
- Modeling prostate CCH highlighted challenges in heating deep pelvic tumors.
- Patient models revealed shielding effects from pelvic bone and influence of tissue composition (fat/muscle) on SAR distribution.
- Agar phantom evaluations yielded overly optimistic results compared to patient models.
Conclusions:
- Agar phantoms do not accurately represent in vivo CCH conditions due to shielding and tissue variations.
- Achieving therapeutic temperatures in deep tumors necessitates allowing temperature extremes in surrounding normal tissues.
- Clinical practice acknowledges treatment-limiting hot spots, which are critical for tumor heating.
- Cold bolus bags offer only superficial cooling effects.
- The developed model enables personalized treatment planning, applicator optimization, and device comparison for CCH.