Specific absorption rate steering by patient positioning in the 'Coaxial TEM' system: phantom investigation

Cylindrical and elliptical homogenous phantoms were used to investigate, both theoretically and experimentally, the effect of phantom positioning on the specific absorption rate (SAR) distribution of the 'Coaxial TEM' system. Theoretical predictions indicated that the maximum of the SAR distribution was stationary around the central axis of the applicator system, irrespective of the position of the phantom. Therefore the maximum SAR can be located at different phantom sites as required. Although two-dimensional models give a qualitative insight in the phenomena studied, they lack quantitive agreement. The steering capacity has been confirmed experimentally and is now clinically applied by positioning the tumour mass according to these insights.