Schneider C J, de Leeuw A A, van Dijk J D
Department of Radiotherapy, Academisch Medisch Centrum, Amsterdam, The Netherlands.
Int J Hyperthermia. 1992 Sep-Oct;8(5):609-19. doi: 10.3109/02656739209037996.
The utility of the light-emitting diode (LED) matrix, i.e. the qualitative localization of maxima and minima in the patterns of the specific absorption rate (SAR), can be extended to quantitative measurements by a method described. With the LED dipoles on the matrix representing light sources of similar characteristics, the minimal field strength necessary to produce light is a criterion which can be easily determined. From the power levels necessary to fulfil this criterion, relative SAR values have been calculated. The attenuation of field strength by the LED matrix has been measured by an additional dipole antenna with fibre-optic read-out, so that the calculated SAR profiles could be corrected for the relatively smaller attenuation near the edges. This technique has been tested for several set-ups in a 'Coaxial TEM applicator' and the resulting SAR profiles along the major axis of the aperture midplane were compared with SAR profiles determined using a single dipole E-field probe. Results show that, from a set of photographs at different power levels, SAR profiles can be constructed with limited accuracy along lines in any direction in the whole aperture midplane and by this the complete two-dimensional SAR pattern can be obtained.
发光二极管（LED）矩阵的效用，即特定吸收率（SAR）模式中最大值和最小值的定性定位，可以通过所述方法扩展到定量测量。由于矩阵上的LED偶极子代表具有相似特性的光源，产生光所需的最小场强是一个易于确定的标准。根据满足该标准所需的功率水平，已计算出相对SAR值。通过带有光纤读出的附加偶极天线测量了LED矩阵引起的场强衰减，以便可以针对边缘附近相对较小的衰减对计算出的SAR分布进行校正。该技术已在“同轴TEM applicator”中的几种设置上进行了测试，并将沿孔径中平面主轴的所得SAR分布与使用单个偶极电场探头确定的SAR分布进行了比较。结果表明，从不同功率水平下的一组照片中，可以在整个孔径中平面的任何方向上沿直线以有限的精度构建SAR分布，从而获得完整的二维SAR模式。
