Experimental Evaluation of an Adaptive Focusing Algorithm for a Microwave Planar Phased-Array Hyperthermia System at UCSF
Abstract
An adaptive focusing microwave planar phased-array hyperthermia system for improved heating of superficial tumors is experimentally investigated. A commercial microwave hyperthermia planar phased-array antenna system at the University of California at San Francisco (UCSF) Radiation Oncology Department has been modified to implement a gradient-search adaptive focusing algorithm. Adaptive focusing measurements in a muscle-equivalent liquid phantom with a 915-MHz microwave planar phased-array hyperthermia system comprising 16 independent amplitude/phase-controlled waveguide antenna elements (Microtherm-1000, Labthermics Technologies, Inc.) are reported. An electric-(E-) -field feedback probe detector, fabricated at UCSF, measures the E-field generated by the hyperthermia phased array. A method of steepest-ascent gradient-search feedback algorithm, implemented in software, controls the hyperthermia array phase shifters and focuses the transmitted radiation beam. In 10 to 15 iterations, the measured phantom data indicate rapid convergence of the adaptive focusing algorithm and significant increase of the focal region field strength due to the adaptive focusing. Two-dimensional E-field radiation pattern measurements were collected by scanning the E-field dipole probe antenna inside the muscle-equivalent liquid phantom. The measured, adaptively phase-focused radiation pattern data indicate a maximum useful heating depth of about 3 cm in a muscle-equivalent sugar/saline phantom having dielectric losses of 3 dB/cm.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 17, 1993
- Accession Number
- ADA267004
Entities
People
- Alan J. Fenn
- Chris J. Diederich
- Paul R. Stauffer
Organizations
- Massachusetts Institute of Technology