ABSTRACT
For the existing measurement methods of residual voltage which can't turn the power off at peak voltage exactly and simultaneously display waveforms, a new residual voltage detection method is put forward in this paper. First, the zero point of the power supply is detected with zero cross detection circuit and is inputted to a single-chip microcomputer in the form of pulse signal. Secend, when the zero point delays to the peak voltage, the single-chip microcomputer sends control signal to power off the relay. At last, the waveform of the residual voltage is displayed on a principal computer or oscilloscope. The experimental results show that the device designed in this paper can turn the power off at peak voltage and is able to accurately display the voltage waveform immediately after power off and the standard deviation of the residual voltage is less than 0.2 V at exactly one second and later.
Subject(s)
Electric Power Supplies , Equipment Design , Microcomputers , Signal Processing, Computer-AssistedABSTRACT
ObjectiveTo investigate whether the T1-weighted dynamic contrast-enhanced perfusion magnetic resonance imaging (DCEPMRI) technique can help to delineate the clinical target volume of brain glioma patients.MethodsThe DCE T1-weighted images from 28 glioma patients were collected after GdDTPA was injected.After the acquired images were processed and analyzed using modified Tofts-Kermode'two compartment analysis model and de-convolution method,the value and its pseudo mapping of quantitative parameter Ktrans related to microvascular permeability were obtained.The tumor size in the largest diameter slice measured both in routine enhanced MRI and Ktrans mapping of T1-weighted DCEPMRI were compared.ResultsThe vascular permeability and tumor infiltration was lower in low grade glioma,the difference of the tumor size between T1-weighted DCEPMRI and routine enhanced MRI reached 0.2％ -0.3％ there was significant difference of tumor size between T1 -weighted DCEPMRI and routine enhanced MRI ( grade Ⅰ and Ⅱ grade with 2.93 cm2∶2.46 cm2(t=6.90,P=0.000) and 4.18 cm2∶3.21 cm2(t=10.22,P=0.000) ).While in high grade glioma,the vascular permeability and the tumor infiltration were higher,the difference of the tumor size between T1-weighted DCEPMRI and routine enhanced MRI reached 25％ - 26％( the size of grade Ⅲ and Ⅳ were 6.46 cm2 vs 5.48 cm2 ( t =10.83,P =0.000) and 8.26 cm2 vs 6.52 cm2(t =18.53,P =0.000) ).ConclusionsThe pseudo mapping of quantitative parameter Ktrans related to microvascular permeability acquired by T1-weighted DCEPMRI reflect the infiltrating circumscription in glioma,T1-weighted DCEPMRI can provide more information in delineation the clinical target volume,and it can be used as a new method for tumor volume evaluation.
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Objective To assess the impact of different number of diffusion gradient directions (NDGD) of diffusion tensor imaging (DTI) on dispersion degree of fractional anisotropy (FA) values and signal-to-noise ratio (SNR) for adult brain tissues. Methods Eight healthy volunteers underwent DTI with 7 NDGD respectively, and the associated FA maps were obtained. Four region of interest (ROI) (genu and splenial of corpus callosum, genu and posterior limb of internal capsule) were chosen in white matter of FA maps, FA values and the corresponding SNRs of the ROIs were computed and analyzed with NDGD increasing. Results FA values within all ROIs did not change remarkably with NDGD increasing. Variance of FA value within two ROIs with high gray value (genu and splenial of corpus callosum) fluctuated randomly and SNR increased slightly, while variance of FA value within the ROIs with low gray value (genu and posterior limb of internal capsule) diminished significantly with NDGD increasing. Conclusion In clinical applications of DTI, an optimum NDGD for DTI data acquisition should be selected according to the ROIs in human brain to be inspected.
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Objective: An automatic seamless stitching method with spinal X-ray image sequence is presented in this paper. Methods: First, biorthogonal wavelet transform is used to implement decomposing of the multi-resolution and the effective edge of the image can be extracted by this method combined with Canny operator. The feature points of the image can be obtained by calculating the edge contour matrix E and the value matrix H. Second, the roughly matching of feature points can be achieved by using Normalized Cross Correlation (NCC) algorithm and the random sample consensus (RANSAC) algorithm is introduced to remove false matching pairs and to achieve precisely matching. Third, the image sequence is automatically sorted with the improved genetic algorithm to achieve automatic stitching. At last, the weighted average fusion algorithm is appfied to achieve smooth and seamless image stitching. This algorithm is robust for the weak-contrast X-ray image sequence. Results: Experimental results show that high-quality and fast image sequence stitching can be obtained automatically by using this method. Conclusions: To a certain extent, it overcomes the shortcomings of X-ray image sequence such as the strong image noise, concentration of values ofpixels, blurred boundaries, large overlap area and the sequence constraint, and therefore it may be applied to in medical imaging field widely.
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Dual-kilovolt technique was realized in dual energy X-ray imaging system with computer controlled KV adjustment, filter switching and image acquirement. The dual energy images can be obtained in 2-3 seconds to avoid moving artifact. Low energy photons in high energy X-ray beam can be attenuated effectively by a 2 mm Cu filter to separate the spectra of the high and low energy X-rays. A simplified dual energy decomposition method was used to obtain the soft tissue image. An example of chest dual energy radiographs is presented to illustrate the performance of the system.
Subject(s)
Humans , Radiography, Dual-Energy Scanned Projection , Methods , Radiography, Thoracic , Signal Processing, Computer-AssistedABSTRACT
Objective To investigate the application of computed radiography(CR) in X-ray projection of whole lower limbs.Methods The radiography in the patient with bilateral knee-malformation was performed using 500 mA X-ray apparatus and several imaging plates(IP) jointed together,then the images including whole both sides of lower limbs were obtained by post-proccesing technique.Results The images not only could show the whole lower limbs on a single film,but be intact.The images also could be used for measuring the length of leg,the angle between the axises of the thigh and the magnifying really.Conclusion The image of whole bilateral lower limbs with a good quality and unity can be acquired using CR and post-processing technique appropriately.
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Objective To design an electrostimulator for cerebellar fastigial nucleus stimulus, which is controlled with singlechip system and using EEG(Electroencephalogram)to modulate amplitude of the carrier wave. Methods The EEG with instrumentation amplifier of high CMRR (Common Mode Rejection Ratio) and some filters are collected. The electric insulation is achieved by using linear optocouplers on the parts of input and output. Results The stimulator can solve the problem of adaptability for wave to simulate the body, and is safe, non -invasive, and of obvious therapy for ischemic cerebrovascular disease. Conclusion The cerebellar fastigial nucleus stimulus can cure ischemic cerebrovascular disease obviously, and the modulation with EEG can solve the problem of adaptability for wave to simulate the body.