Development and testing of SAR-visualizing phantoms for quality control in RF hyperthermia.

Abstract

A new prototype of an elliptical standard phantom with fat-equivalent walls and a lamp matrix for SAR (specific absorption rate) visualization has been developed. This paper outlines the manufacture of solid components based upon either polyester resin or epoxy resin, as well as the adjustment of their electrical conditions (epsilon r, sigma) by admixtures of carbon and/or aluminium powder. Visualizing sensors (LED = light-emitting diodes, miniature lamps) are evaluated with respect to their transformation of electric field strength into light. Standard SAR patterns of the hyperthermia system BSD-2000 have been semiquantitatively assessed by the visualizing technique (power stepping method) and quantitatively by E field sensor scans. Extracted iso-SAR distributions are in good agreement with E field sensor scans performed with a lamp sensor coupled to a fibre or using a dipole probe with high resistive leads. The requirement for periodic quality control of SAR patterns of RF (radio frequency) hyperthermia systems is demonstrated. Comparisons between techniques are given, specifically with respect to the LED phantom of Schneider and van Dijk.