|Budget Amount *help
¥6,000,000 (Direct Cost : ¥6,000,000)
Fiscal Year 1995 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1994 : ¥3,900,000 (Direct Cost : ¥3,900,000)
(1) A newly designed 1.2GHz radiometer receiver has been developed and incorporated into a 5-frequency-band radiometer system previously developed at Shizuoka University. A new feedback control circuit, in which a stepping motor was replaced with a 12-bit D/A converter, was installed in the 1.2GHz receiver to control the temperature of the reference temperature noise source. With this modification, the brightness temperature resolution of 0.036K was achieved at a 5-second integration time, where the theoretical value was 0.032K.
(2) A dielectric-filled (epsilon_r=60) waveguide antenna having a 4.6cm x 4.6cm aperture has been developed to achieve the depth of measurement sensitivity of about 4cm. The electromagnetic coupling of this antenna to a homogeneous tissue medium and to a four-layred tissue medium consisting of bolus, skin, fat and muscle has been analyzed in 3 dimensions using the modal analysis and the finite-difference time-domain method. From the 3D field analysis results, ra
diometric weighting functions were derived for the realistic model of the antenna-tissue system. A temperature profile retrieval algorithm has also been developed using the new weighting functions.
(3) Experiments were performed using this antenna and a 5-band radiometer system to measure the temperature profile in an agar phantom (agar powder : 4%, NaCl : 0.24%, NaN_3 : 0.4%, distillled water : 95.36%). The temperature profile obtained by the radiometric method agreed well with probe measurement results, demonstrating the validity of the radiometric method. The resolution (2sigma interval) of tissue temperature measurement was 0.2ﾟC at 2cm, 0.7ﾟC at 3cm, 1.6ﾟC at 4cm from the phantom surface.
(4) An intracavitary antenna has been developed. Experiments were made by inserting this antenna in an agar phantom. The antenna was used both for the 2.45GHz heating and the radiometric temperature measurement at 2.4GHz in a time division scheme. The single-band radiometric measurement was made to estimate the maximum temperature in tissue. The radiometric estimation gave higher values than the highest temperatures by measured by probes by about 0.5ﾟC. Less