Abstract
The measurement of the transfer function is a good tool to evaluate the radiofrequency heating of complex conductive wires, such as pacemaker leads. The aim is to describe precisely the design of a transfer function bench and compare the measurements to simulations. The transfer function was measured by mean of an excitation probe and a receiving probe, both connected to a two-port vector network analyzer. The experimental results were compared with the simulated results, reproducing the excitation scheme. This procedure was applied to two different cables with different geometrical and insulation properties to test the robustness of the setup. It is possible to touch the cable electrode with the excitation probe without inducing an error in the measured transfer function, which solves the direct coupling problem. There is a good agreement between the measured and simulated transfer function for both tested cables. A valid transfer function measurement bench is described. Magn Reson Med 79:1766-1772, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Highlights
(ASTM) phantom [11] under the usual test conditions along the side of the phantom [11,12]
If we consider the normalized simulated and measured transfer functions and a constant amplitude and phase incident field, we find that the calibration factors are equal
At the excited end of the cable, the simulated transfer function showed discontinuities in the derivative at 1.3 cm from the beginning of the insulation, which can be explained by the fact that the excitation probe excites the cable through the direct contact and through a radiated field
Summary
Simulations have been done placing the excitation monopole transversally 0.5 mm away from the cable electrode and the transfer function fitted perfectly to the case where it touches to an amplitude scale factor and a constant phase shift close. At the excited end of the cable, the simulated transfer function showed discontinuities in the derivative at 1.3 cm from the beginning of the insulation, which can be explained by the fact that the excitation probe excites the cable through the direct contact and through a radiated field. This is consistent with the evaluation of the radiated field from the emission probe being received directly by the reception probe without the presence of the cable under test.
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