抄録
The paper is concerned with improvement of the chirp radar-type microwave computed tomography developed for non-invasive thermometry of the human body. The hardware of the radar-type microwave CT is quite simple and the reconstruction algorithm which has been used for X-ray CT systems is applicable. This is because the microwave CT can discriminate the transmitted waves on the straight ray path between the transmitting antenna and the receiving antenna from multipath signals. We have already reported that the spatial resolution is about 1cm, but temperature resolution has never been directly measured because of its poor resolution of the FFT analyzer. The analyzer was replaced by the new model whose resolution and accuracy were enough for discriminating temperature change less than 1°C. The YIG-tuned bandpass filter was incorporated in the improved system along with the YIG-tuned oscillator which was used to generate the microwave chirp signals. This was very useful to improve the SN ratio of the tomograms and also useful to expand the dynamic range of the attenuation measurements. Throughout a series of the experiments using phantoms of a human body, temperature change by 2°C was successfully imaged. The temperature change by 1°C was not observable as the image for temperature instability of the system. But imaging of the temperature change which is less than 1°C may be feasible by shortening the time required for the measurement.
