Accuracy of electrical field measurement using the flexible Schottky diode sheet at 433 MHz.
In this study, the accuracy of Schottky diode sensors mounted as a two-dimensional array on a flexible 125 micro m thick polyester foil has been studied. The diodes are placed at a distance of 2.5 x 2.5 cm, resulting in a measuring area of 20 x 20 cm. The diodes are placed across the gap between both arms (3 x 5 mm) of a dipole, total length 12 mm. High resistance (1 M Omega/m) carbon transmission lines printed on the sheet are used to connect each electrical (E) field sensor to the read-out electronics and a data-acquisition system. It is demonstrated that the flexible Schottky diode sheet can quantitatively measure E-field distributions at 433 MHz with an overall accuracy of approximately 6% (1 SD). The largest contribution to the inaccuracy is related to the phantom heterogeneity. The absolute sensitivity of this electrical field sensor is 0.71 V/m per V/m of the applied external electromagnetic field. The DC-voltage signal of the diodes shows a more or less square root relation to the RF-power applied to the applicator over a 15-fold range. An important feature of the system is that it provides the ability to perform on-line monitoring of the E-field, i.e. the SAR distribution of 433 MHz applicators. Further, it enables the introduction of fast and easy quality control protocols for superficial hyperthermia applicators.
van Rhoon
G C
GC
Erasmus MC-Daniel den Hoed Cancer Center, Department of Radiation Oncology, Unit Hyperthermia, PO Box 5201, 3008 AE, Rotterdam, The Netherlands. rhoon@hyph.azr.nl
Ameziane
A
A
Lee
W M
WM
van der Heuvel
D J
DJ
Klinkhamer
H J
HJ
Barendrecht
C
C
Volenec
K
K
Rietveld
P J M
PJ
D004560:Electricity; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity