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MRI-Monitored Electromagnetic Heating Using Iterative Feedback Control and Phase

Summary: MRI-Monitored Electromagnetic Heating Using
Iterative Feedback Control and Phase
Interference Mapping
Department of Electrical and Computer Engineering, Beckman Institute for Advanced Science and Engineering,
University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
ABSTRACT: Noninvasive electromagnetic hyperthermia, used in combination with radio-
therapy or chemotherapy, is a promising technique in the treatment of large, deep-lying
tumours. One of the major difficulties in effective implementation, however, is that the spatial
distribution of electric fields within the patient is strongly influenced by tissue morphology and
dielectric properties, and is therefore difficult to model. Even when desired heating profiles are
achieved experimentally, the specific absorption rate at the focus generally does not reach its
theoretical maximum value since the E-fields are not completely coherent. In this article, a new
method, phase interference mapping, is developed to address this latter problem and is
demonstrated in phantoms. The complete process for optimizing spatial and temporal control
of electromagnetic heating has three separate steps. The first involves phase calibration of the
individual dipoles of a phased array applicator with a noninvasive E-field probe placed on the
surface of the phantom. In the second step, an iterative feedback method is used to rapidly
steer the thermal focus as close as possible to the desired location. Noninvasive mapping of the
temperature and specific absorption rate is realized by magnetic resonance imaging. The final


Source: Andrews, Anne M. - Huck Institutes of the Life Sciences, Pennsylvania State University


Collections: Biology and Medicine