ABSTRACT
This study aims to propose a multifrequency time-difference algorithm using spectral constraints. Based on the knowledge of tissue spectrum in the imaging domain, the fraction model was used in conjunction with the finite element method (FEM) to approximate a conductivity distribution. Then a frequency independent parameter (volume or area fraction change) was reconstructed which made it possible to simultaneously employ multifrequency time-difference boundary voltage data and then reduce the degrees of freedom of the reconstruction problem. Furthermore, this will alleviate the illness of the EIT inverse problem and lead to a better reconstruction result. The numerical validation results suggested that the proposed time-difference fraction reconstruction algorithm behaved better than traditional damped least squares algorithm (DLS) especially in the noise suppression capability. Moreover, under the condition of low signal-to-noise ratio, the proposed algorithm had a more obvious advantage in reconstructions of targets shape and position. This algorithm provides an efficient way to simultaneously utilize multifrequency measurement data for time-difference EIT, and leads to a more accurate reconstruction result. It may show us a new direction for the development of time-difference EIT algorithms in the case that the tissue spectrums are known.
ABSTRACT
Objective To observe the difference of efficacy of three different treatment of internal fixation of intervetebral crasis on cervical spondylosis (spinal cord) .Methods From January 2009 to January 2013 ,There are 167 cases of patients admitted to hospital from cervical spondylosis (spinal cord ) ,randomly selected different fusion fixation methods are divided into three groups :in the first group ,there were 55 patients treated with autologous iliac bone graft fusion plate fixation ;in the second group , there were 60 patients treated with zero profile material PEEK interbody fusion with autologous bone graft ;in the third group ,the 52 patients were treated with the PEEK material MC + self‐locking cervical interbody fusion with autologous bone graft .Observa‐tion and comparison indicators include :spinal cord function JOA scores before and after surgery ,surgical segment intervertebral height and cervical curvature condition .Results Follow‐up lasted from 13 to 50 months ,the average length was 26 months .The difference in operation time ,blood loss during surgery analysis ,wherein the first group and the second or third group of three groups was statistically significant (P0 .05) .In the first group ,there were 17 patients had transient throat discomfort and symptom disappeared 48 hours later ;dysphagia relieved or disappeared in one week ;there were two cases of screws and titanium loosen one week after operation , and were treated with immediate revision surgery .In the second ,third group ,there were 19 cases and 13 cases showed temporary throat discomfort disappeared within 48 hours after surgery respectively ,there was no dysphagia .No patient experienced cerebrospi‐nal fluid leakage ,hematoma and wound infection .The postoperative JOA scores spinal cord function (17 points France) ,surgical segmental cervical intervertebral height and curvature of three groups improved significantly compared with preoperative evaluation index ,and there was no significant difference among three groups (P>0 .05) .In the last follow‐up ,the interbody fusion rates of the first ,second and third groups were 67 .1% ,66 .3% and 65 .9% ,the difference between groups was not statistically significant (P>0 .05) .Conclusion Anterior decompression and interbody fusion locking device applications showed good performance in maintai‐ning the intervertebral height segment surgery ,rehabilitation cervical curvature ,and promote bone fusion with autogenous titanium plate fixation comparison .Patients can get a good surgery ,and the former has a simpler surgical fixation method ,shorter time ,less bleeding and less complications .
ABSTRACT
Objective To compare the performance of novel Ag/AgCl pulverized electrodes with conventional Ag/AgCl coating electrodes in cerebral application of Electrical Impedance Tomography(EIT).Methods Based on the EIT system developed by our group,raw data were measured on a phantom and an adult volunteer,with Ag/AgCl coating electrodes and pulverized electrodes,respectively.The performances of electrode systems were evaluated in contact impedance and two other figures(the high-frequency SNR,HFSNR;the low-frequency SNR,LFSNR).Results Ag/AgCl pulverized electrode plays a better performance in resisting noise and keeping stabilization.Conclusion Ag/AgCl pulverized electrode develops the needs of imaging and monitoring human brains in EIT more availably.
ABSTRACT
Objective To provide the hardware system of EIT with an excellent direct current(DC) power source. Methods The spectrums of the outputs of DC power source and the driving source were analyzed by means of Spectrum Analyzer- E4408B when EIT system was respectively powered by battery, linear power source and switching power source. Based on the numbers and power levels of the spurs of the three power sources and the numbers and power levels of the interferences within the driving source, the influence of the three power sources on the error of measuring was estimated. Meanwhile the EIT system did data acquisition, the overall signal-to-noise-ratio(SNR) of the three power sources at the 18 frequencies were calculated and the influence of the three power sources on the error of measuring was judged. Results With respect to the numbers and power levels of the interferences within the driving source when EIT was powered respectively by the three power sources, the battery output 6 interferences, the highest power of which achieved -78.25 dBm; the linear power source output 6 interferences, the highest power of which achieved -67.11 dBm; the switching power source output 15 interferences, the highest power of which achieved -35.83 dBm. The overall SNRs of the battery at the 18 driving frequencies were higher than that of the linear power source, and the overall SNRs of the linear power source were higher than that of the switching power source. Conclusion The power mode of battery is the best for the hardware of EIT among the three power sources.
ABSTRACT
The reverse problem of Electrical impedance tomography(EIT) is a highly ill-posed problem.It is concluded that spatial prior information could improve the final image quality.This paper proposes a new method for obtaining prior information.By this method,the inspected cross-section contour and internal structure for EIT can be achieved.