PARENT SESSION
1:30 PM to 3:30 PM
Monday, April 22, 2002
Poster Session 3 Heating Devices and High Temperature Therapy
Room: Nevada 1-2
(MP03-29) SAR characteristics of six different sigma-eye applicator configurations in a homogeneous cylindrical phantom using the schottky diode sheet, a multi-institutional study.
Ameziane, Ali1, Abdel-Rahman, Sultan2, Issels, Rolf2, Futschik, Gunther3, Turner, Paul4, Hagmann, Mark4, van Rhoon, Gerard*,1, 1 University Hospital Rotterdam-Daniel, Rotterdam, The Netherlands2 Klinische Kooperationsgruppe Hyperthermie-GSF-National Research Center for Environment and Health, Munich, Germany3 Dr. Sennewald Medizintechnik, Munich, Germany4 BSD Medical Corp., Salt Lake City, Utah, USA
ABSTRACT-
Purpose: The Sigma-Eye applicator of the BSD2000-3D system possesses unique 3D-SAR steering features. Conformation and quantitative assessment of the 3D-SAR steering feasibility of the Sigma-Eye by independent research groups is still limited. In view of the growing interest in international, multi-institutional clinical hyperthermia studies it is essential to gain a thorough knowledge of the consistency of the various individual Sigma-Eye applicators used. Material & Methods: The Sigma-Eye applicators investigated: three standard factory delivered applicators (UHR, KKG new and old), one applicator with additional tuning of the twelve dipole antennae (Clinic Kempfenhausen) and one special MRI-modified applicator. The latter applicator was tested under two conditions: attached to the MRI but placed out of or inside of the magnet. The Schottky diode sheet system was used to perform on-line SAR characterisation measurements in a homogeneous abdomen-equivalent cylindrical phantom at the central horizontal plane. Note that all experiments were performed without preparation of the system. Results and conclusions: Analysis of measured data showed that substantial differences between the applicators exist. The efficiency, expressed as the maximum squared voltage (V2), of the non-MRI Sigma Eye applicators and the MRI-modified Sigma-Eye outside the MRI varied between 1.80 to 2.61 V2. The effective field size of these five applicator configurations ranged from 178 to 228 cm2. These values were measured for a central target, for equal amplitudes to all twelve antennae and zero phase offset. In evaluating these differences it should be noted that the Clinic Kempfenhausen Sigma-Eye has been modified with respect to their dipole antenna tuning. This apparently affected the power coupling to the phantom but not the relative SAR distribution. Furthermore, the data suggest that the basic SAR characteristics of the MRI modified Sigma-Eye applicator are comparable to the standard applicator but once placed in the MRI magnet a large energy loss (30%) occurs due to the E-Field absorption in the metal structure of the MRI-magnet. Acknowledgement: This work was supported by the Dutch Cancer Society: grant 97-1497.
KEYWORDS: Regional hyperthermia, Quality assurance, SAR measurement