Correlations between image quality and radiation dose in prospective and retrospective ECG-gated CT coronary angiography in patients with different heart rates / 中国医学物理学杂志

Objective To explore the correlations between image quality of prospective and retrospective electrocardiogram(ECG)-gated CT coronary angiogram and radiation dose in patients with different heart rates.Methods A total of 135 patients undergoing 256-slice spiral CT coronary angiography were enrolled in the study.Among them,66 cases received prospective ECG-gated scanning(prospective ECG-gated group)and further divided into two subgroups with heart rate≤80 beats/min(prospective ECG-gated+low heart rate subgroup,n=39)and>80 beats/min(prospective ECG-gated+high heart rate subgroup,n=27).The other 69 cases underwent retrospective ECG-gated scanning(retrospective ECG-gated group),including 45 cases with heart rate≤80 beats/min(retrospective ECG-gated+low heart rate subgroup)and 24 with heart rate>80 beats/min(retrospective ECG-gated+high heart rate subgroup).The baseline data,image quality[mean CT value,image noise,signal-to-noise ratio(SNR),subjective image quality score]and radiation dos[CT volume dose index(CTDIvol),dose length product(DLP),effective dose(ED)]were compared among 4 subgroups.The correlations of image quality with heart rate and radiation dose in prospective and retrospective ECG-gated groups were analyzed.Results The heart rates in prospective and retrospective ECG-gated+low heart rate subgroups were lower than those in prospective and retrospective ECG-gated+high heart rate subgroups(P<0.05).When comparing the mean CT value,image noise,SNR and subjective image quality score among 4 subgroups,no statistically significant differences were observed(P>0.05).The CTDIvol,DLP and ED in prospective ECG-gated+low heart rate subgroup were significantly lower than those in the other 3 subgroups(P<0.05),and the indicators in prospective ECG-gated+high heart rate subgroup were lower than those in retrospective ECG-gated group(including low and high heart rate subgroups)(P<0.05).Pearson correlation coefficient analysis revealed that the mean CT value,image noise,SNR,subjective image quality score had no significant correlation with heart rate,CTDIvol,DLP and ED in prospective and retrospective ECG-gated groups(P>0.05).Conclusion The subjective and objective image quality of 256-slice spiral CT coronary angiography is not correlated with radiation dose.Prospective ECG-gated scanning can reduce the radiation dose and ensure the image quality as compared with retrospective ECG-gated scanning.This holds true for eligible patients with high heart rate,and the former can effectively reduce radiation exposure.Therefore,prospective ECG-gated scanning is worthy to be promoted in clinic.

Research on wireless transmission system of multi-parameter signs / 国际生物医学工程杂志

Objective To design a wireless transmission solution of multi-parameter vital signs signal which can be applied in psychological status assessment.Methods C8051F350 SOC was used to define data frame structure,on application level,including channel number,control words,data and so on,which put all nodes data into the upper computer cache area by channel in an orderly way.A transfer rate of five seconds on a grid,each grid at least 48 groups of data was chosen in buffer,which could not only match the dynamic PC image display,but also to achieve the stability of the channel signal acquisition and orderly transfer.Results After operating test,with the communication distance within 10～15 m,the dynamical display of the upper computer showed a smooth curve data,which met the system design requirement.After optimization of the data frame,the transmission power could be reduced to 1/12 of that of normal mode.The whole system with three advantages of small size,low power and easy to carry.Conclusion Multi-parameter wireless acquisition system described in this paper eliminates the data line connected to the subjects,which does not affect their normal activities and is conducive to the real response of subjects' mental state,and provides a reliable means of detection for psychological assessment.

Current source and digital demodulation technique in EIT system based on FPGA / 国际生物医学工程杂志

ObjectiveA general experiment platform of electrical impedance tomography(EIT) based on field programmable gate array(FPGA) was designed to meet the requirements of EIT digital measurement.A digital current source and the research on digital demodulation method was completed.MethodsFor construction of the experiment platform,DDS module,D/A and A/D interface module,digital demodulation module and RS-232 communication module were all integrated in one FPGA chip.ResultsThe source can provide multi-frequency excitation signals of 2 mA in the range of 6.1-390.6 kHz.The output impedance of the source was higher than 190 kΩ.Both the real and the virtual information of measured impedance could be extracted.ConclusionMeasurements based on bioimpedance-equivalent circuit model verified the validity of the platform.The research results of this paper provides a foundation for the construction of a practical EIT system.

Review of the active locomotion system for capsule endoscope / 生物医学工程学杂志

This review summarized the progress of researches on the active locomotion system for capsule endoscope, analyzed the moving and controlling principles in different locomotion systems, and compared their merits and shortcomings. Owing to the complexity of human intestines and the limits to the size and consumption of locomotion system from the capsule endoscope, there is not yet one kind of active locomotion system currently used in clinical practice. The locomotive system driven by an outer rotational magnetic field could improve the commercial endoscope capsule, while its magnetic field controlling moving is complex. Active locomotion system driven by shape memory alloys will be the orientated development and the point of research in the future.

Development of a video image system for wireless capsule endoscopes based on DSP / 生物医学工程学杂志

A video image recorder to record video picture for wireless capsule endoscopes was designed. TMS320C6211 DSP of Texas Instruments Inc. is the core processor of this system. Images are periodically acquired from Composite Video Broadcast Signal (CVBS) source and scaled by video decoder (SAA7114H). Video data is transported from high speed buffer First-in First-out (FIFO) to Digital Signal Processor (DSP) under the control of Complex Programmable Logic Device (CPLD). This paper adopts JPEG algorithm for image coding, and the compressed data in DSP was stored to Compact Flash (CF) card. TMS320C6211 DSP is mainly used for image compression and data transporting. Fast Discrete Cosine Transform (DCT) algorithm and fast coefficient quantization algorithm are used to accelerate operation speed of DSP and decrease the executing code. At the same time, proper address is assigned for each memory, which has different speed;the memory structure is also optimized. In addition, this system uses plenty of Extended Direct Memory Access (EDMA) to transport and process image data, which results in stable and high performance.