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In this paper, a new probe is proposed for the dielectric measurement of anisotropic tissue in radio frequency band, which could accomplish the dielectric measurement in perpendicular directions by one operation. The simulative studies are performed in the frequency range from 1-1 000 MHz in order to investigate the influence of probe dimension on the energy coupling and sensitivity of measurement. The suitable probe is designed and validated for the actual measurement in this frequency band. According to the simulation results, the energy coupling of the probe could be kept below -12 dB in the frequency range from 200-400 MHz with high sensitivity of measurement for the dielectric properties of anisotropic tissue. That indicates the new type of probe has the potential to achieve the dielectric measurement of anisotropic tissue in radio frequency band and could avoid the measurement error by multi-operations in the conventional method. This new type of probe could provide a new method for the dielectric measurement of anisotropic tissue in radio frequency band.
RESUMEN
Objective To explore the value of iDose4 iterative reconstruction for coronary CT angiography (CCTA).Methods Totally 124 coronary heart disease patients underwent iDose4 iterative reconstruction and filtered back projection (FBP) reconstruction,of whom,56 ones with BMI not less than 20 kg/m2 were put into No.1 iteration group using 135 kV tube voltage and 68 ones with BMI less than 20 kg/m2 were into No.2 iteration group using 110 kV tube voltage.FBP reconstruction was executed with 110 kV tube voltage.Comparison analyses were carried out on signal noise ratio (SNR),contrast to noise ratio (CNR) and image quality.Results There were significant differences between the values of SNR,radiation dose and image quality in No.1 iteration group and FBP group (P＜0.05).Statistical differences were also found between the values of CNR and radiation dose in No.2 iteration group and FBP group,while there were no obvious differences between the values of SNR and image quality in the above two groups (P＜0.05).Conclusion Low-voltage iDose reconstruction gains advantages in radiation dose and image quality during 64-slice CCTA,and thus is worthy promoting clinically.
RESUMEN
Magnetic induction method aims at the noninvasive detection of liver iron overload by measuring the hepatic magnetic susceptibility. To solve the difficulty that eddy current effects interfere with the measurement of magnetic susceptibility, we proposed an improved coil system based on the static field magnetization principle in this study. We used a direct current excitation to eliminate the eddy current effect, and a rotary receiver coil to get the induced voltage. The magnetic field for a cylindrical object due to the magnetization effect was calculated and the relative change of maximum induced voltage was derived. The correlation between magnetic susceptibility of object and maximum magnetic flux, maximum induced voltage and relative change of maximum induced voltage of the receiver coil were obtained by simulation experiments, and the results were compared with those of the theory calculation. The contrast shows that the simulation results fit the theory results well, which proves our method can eliminate the eddy current effect effectively.