In the magnetic induction tomography(MIT) system,the electrical conductivity of biological tissue is direct proportion to the phase difference between the excitation signal and the detection signal.To obtain the image of the contribution of tissue's electrical conductivity,the system must have the function of phase detection with high accuracy.The paper focuses on the means of digital phase detection,including FFT method,the correlation method and the classic method,which are ultimately compared with analogue phase detection method.The experimental results show that FFT method and the correlation method,with low error level and high linearity,can better detect the phase difference with the level of 0.1?.The digital phase difference detection provides a kind of effective method for MIT system.

Objective To determine the effects of non-thermal biological effect of low frequency pulsed electromagnetic field (LFPEF) with 15 Hz and 30 mT on ulcer wound during the plateau stress ulcer cure.Methods Thirty male Sprague-Dawley rats were assigned to three equal groups:control,normal cure group (NC) and exposure treatment groups (ET).The plateau rats stress ulcer models were constructed with the combination method of a hypoxic and low-pressure acclimation and the stimulation of absolute ethyl alcohol irrigating stomach.The LFPEF equipment generated the LFPEF of 15 Hz,40％ duty cycle and 30 mT to expose and treat the rats' stomach of ET group with the frequency of 3 hours each day.After 6 days of exposure treatment,the stress ulcer cure situation of each group was evaluated by the methods of macroscopic observation,the gastric juice pH values detection and ulcer index (UI) measurement.Results After 6 days of model,the macroscopic observation showed that the ulcer of NC group was worse than the that of ET group (P＜0.05).The pH values and UI of ET group were significantly different with those of NC group,and closed to those of the control group.Conclusion The nonthermal biological effect of LFPEF could promote the plateau stress ulcer cure.

Objective To determine the difference in blood microcirculation recovery between normal frostbite and high-altitude frostbite during the wound healing.Methods Twenty four male rats were randomly divided into control group (n=8), normal frostbite group (n=8), and high-altitude group (n=8). The normal frostbite group rats were frozen to produce mid-degree frostbite models by controlling the freezing time with liquid nitrogen penetration equipment. The high-altitude frostbite group rats were acclimated to a hypoxic and low-pressure environment for 1 week, and then the high-altitude frostbite models were constructed by the same way with liquid nitrogen penetration apparatus. On days 3, 7, 11, 15, 19, and 23 after modeling, the recovery situation of blood circulation of each group was observed with contrast ultrasonography by injecting SonoVue micro-bubble into rats' tail. Finally, the micro-bubble concentration (MC) was calculated to confirm the blood circulation recovery with software Image Pro. ResultsAt different time points, the wound area of the high-altitude frostbite group was bigger than that of the normal frostbite group, and the MC of control group was always about (27±0.2)×109/ml. On day 3, 7, 11, 15, 19, and 23, the MC was significantly lower in the high-altitude frostbite group than in the control group and normal frostbite group (P<0.05). The MC of normal frostbite group was significantly lower than that of the control group on day 3, 7, 11, 15 and 19 (P<0.05). In addition, no obvious difference in MC was found between normal group and control group on the 23th day (P<0.05).Conclusion The blood microcirculation recovery after high-altitude frostbite is significantly slower than the normal frostbite.

This research work was aimed to improve the performance of magnetic induction tomography (MIT) system by designing a high-performance excitation source and the optimal excitation coil. A new type excitation source with adjustable output was designed, and then the power circuit was simulated by the software ICPA. Focused and solenoid coils were designed in accordance with the design principle of coil, then the optimal excitation coil was proved by measuring the magnetic field distribution and the experimentation of phase detection using neuron cell models. At the stated excitation frequency, the parameters of the excitation source are output power 0.035 W-31.4 W, steady output peak current over 1 A, frequency stability 10(-9), and THD amplitude less than -51dB. When compared with other coils, the focused discal excitation coil is most effective for phase detection with the use of neuron cell models. The excitation source can produce the stated frequency sine wave with higher frequency stability, lower THD and wider adjustable output power. The phase difference between normal cell model and edema cell model was more significant by measurement using focused discal coil.
Brain ; physiology ; Electronics, Medical ; instrumentation ; Equipment Design ; Humans ; Image Processing, Computer-Assisted ; Magnetics ; instrumentation ; Tomography ; methods