Pulsed magnetic field gradients generated by gradient coils are widely used in signal location in magnetic resonance imaging (MRI). However, gradient coils can also induce eddy currents in final magnetic field in the nearby conducting structures which lead to distortion and artifact in images, misguiding clinical diagnosis. We tried in our laboratory to measure the magnetic field of gradient-induced eddy current in 1.5 T superconducting magnetic resonance imaging device; and extracted key parameters including amplitude and time constant of exponential terms according to inductance-resistance series mathematical module. These parameters of both self-induced component and crossing component are useful to design digital filters to implement pulse pre-emphasize to reshape the waveform. A measure device that is a basement equipped with phantoms and receiving coils was designed and placed in the isocenter of the magnetic field. By applying testing sequence, contrast experiments were carried out in a superconducting magnet before and after eddy current compensation. Sets of one dimension signal were obtained as raw data to calculate gradient-induced eddy currents. Curve fitting by least squares method was also done to match inductance-resistance series module. The results also illustrated that pulse pre-emphasize measurement with digital filter was correct and effective in reducing eddy current effect. Pre-emphasize waveform was developed based on system function. The usefulness of pre-emphasize measurement in reducing eddy current was confirmed and the improvement was also presented. All these are valuable for reducing artifact in magnetic resonance imaging device.
Objective To study the effect of local appl ication of different concentrations of nerve growth factor (NGF) on fracture heal ing, and to further search for the appropriate concentration gradient of NGF to promote fracture heal ing. Methods Seventy-five adult male Sprague Dawley rats, weighing (220.0 ± 2.5) g, were made the right tibia fracture model at 1 cm distal from the tibial tubercle and randomly divided into 5 groups (groups A, B, C, D, and E, n=15). Fractures were treated with 0.3 mL normal sal ine containing different concentration of NGF (0.006 48 × 10-2, 0.032 40 × 10-2, 0.162 00 ×10-2, and 0.810 00 × 10-2 μg/g) in groups A, B, C, and D, respectively, and the same amount of normal sal ine in group E. After2, 4, and 6 weeks, the specimens were harvested from 5 rats of each group to perform the biochemical test and histological observation. Before the rats were sacrificed, the arteriovenous blood was taken from the eye-ball to test the alkal ine phosphatase (ALP) activity. Results After 2, 4, and 6 weeks, the gross observation showed that the size and hardness of bone tissue and callus tissue growth gradually increased in groups A, B, C, and D, and group D was higher than groups A, B, C, and E. The X-ray films showed that the calcified area gradually increased in groups A, B, C, and D, and group D was higher than groups A, B, C, and E. The histological observation showed that the trabecular qual ity and maturity in group D were better than those in groups A, B, C, and E. Group D was significantly higher than groups A, B, C, and E (P lt; 0.05) in the gray values of callus tissue and the calcium content of callus tissue at 4 and 6 weeks, in the wet weight of callus tissue at 2 and 4 weeks, and in the ALP content of serum at 2 weeks. The trabecula surface index of osteoblast, the trabecular volume, and the trabecular width decreased as time in the order of groups A, B, C, and D, which were higher than those of group E; group D was the highest, showing significant differences when compared with the other groups (P lt; 0.05). Conclusion The local appl ication of NGF can promote fracture heal ing in rats. The high concentration gradient of NGF (0.810 00 × 10-2 μg/g) has an obvious promotion role on fracture heal ing.
Objective To quantitatively evaluate the effect of 2 types of pressures induced injury by using threedimensional (3D) reconstruction of rats loaded tibial is anterior muscle from two-dimensional (2D) image of serial histological sections. Methods Twenty female or male Sprague Dawley rats, aged 10-12 weeks and weighing 280-300 g, were randomlydivided into experimental group (n=10) and control group (n=10). The random side of tibial is anterior muscle was givenintermittent gradient (8.0-21.3 kPa) and sustained (13.3 kPa) pressure in 0.12 cm2 area in experimental group and controlgroup, respectively; the experiment was terminated and the general condition of rats was observed after 3 cycles, and a single cycle included 2 hours of compression and 30 minutes of release. The general observations of pressed skin and tibial is anterior muscle were done after 24 hours of pressure rel ief, and the tibial is anterior muscle was harvested integrally from the loaded side, then made into interval 4 μm serial sections. After HE staining, 2D images were obtained. Necrosis and injury areas were distinguished by Image Pro Plus (IPP) 6.0 software and image registration was conducted by Photoshop 8.0.1 after 2D panorama images acquired by digital microscope (× 40) and IPP mosaic software. 3D reconstruction was establ ished via data processing using Mimics 10.1 software so as to get the volume, the surface area, and 3D images of the whole piece of tibial is anterior muscle and injury areas respectively. Results All rats of 2 groups survived till experiment terminated and no skin ulcers occurred after 24 hours. Edema and indentation were observed on press side skin and tibial is anterior muscles of 2 groups, fadeless maroon area was observed in control group. A total of 994 sl ices were obtained from 20 samples of tibial is anterior muscles. 3D images suggested that injury of control group was severe, which penetrated the whole piece of tibial is anterior muscle and expandedalong the tibia bony prominence. By contrast, injury of experimental group was less, but had similar width to the contact surface of indentor. There was no significant difference in the volume and the surface area of tibial is anterior muscle between 2 groups (P gt; 0.05), while the injury volume and the injury surface area were significantly smaller in experimental group than in control group (P lt; 0.05). Conclusion 3D reconstruction is an effective method to quantitatively evaluate pathological changes inside the integrity tissue and can provide the visual basis for the mechanical property distributed in the loaded muscle. Intermittent gradient pressure can reduce deep tissue injury.
Objective To investigate the effect of dissociation of the human retinal pigment epithelium (RPE) cells by ficoll hypaque gradient centrifugation.Methods The primary human RPE cells and subcultured human RPE cells were dissociated with ficoll gradient centrifugation solution (d=1.077 g/ml)and the same divid ed cells as the control were dissociated with routine normal culture medium cent rifugation. The Trypan blue (0.4%) rejection staining was used, and the mouse anti-human monoclonal anti-body and fluorescein isothiocyanate (FITC) labeled rabbit anti-mouse IgG were utilized for indirect immunoreactivity for the test of human cytokeratin (CK) in active RPE cells cytoplasm. Flow cytometry assay was used to analyzed the percentages of CK positive staining RPE cells. simultaneously, the cells configuration, growth condition, the rate of clone formation, and the purifying result were observed under the fluorescent and confocal microscope.Results The survival rate and positive rate of CK of RPE cells in experimental group were higher than those in the control（P＜0.001）, but the number of the cells was reduced. The cells in the experimental group were integrated round with smooth border, symmetrical staining, homogeneous configuration and higher rate of clone formation （P＜0.001）. Conclusions RPE cells disas sociated with ficoll gradient centrifugation have the better dissociation effects. (Chin J Ocul Fundus Dis，2003，19：333-404)
ObjectiveTo explore the variation of the structure of the intestinal flora between healthy people and patients with obstructive jaundice perioperatively. MethodsFrom February 2013 to August 2014, 20 patients with obstructive jaundice and 10 healthy persons (normal control group) in our hospitol were selected as the research object. The first stool specimens of the research object after admission were obtained and the total fecal bacteria DNA were extracted. After polymerase chain reaction amplification, the changes in the structure of bacterial flora were dynamic observed by using denaturing gradient gel electrophoresis (DGGE), and the gel bands were analyzed by using Quantity One software. The similarity and diversity of flora structure, and principal component analysis (PCA) were analyzed. ResultsSignificant differences of colonic microflora were found between patients with obstructive jaundice and healthy people; advantage intestinal flora in obstructive jaundice patients was significant lower than the normal control group. With the extension of time and degree of obstruction aggravated, a descending trend was found in number, abundance, and diversity of the intestinal microflora (P < 0.05). ConclusionThere is significant differences in the structure of colon bacteria in patients with obstructive jaundice and healthy persons.
The dose data produced by treatment plan system (TPS) in intensity-modulated radiation therapy (IMRT) has many gradient edge points. Considering this feature we proposed a new interpolation algorithm called treatment plan dose interpolation algorithm based on gradient feature in intensity-modulated radiation therapy (TDAGI), which improves the Canny algorithm to detect the gradient edge points and non-edge points by using the gradient information in the dose data plane. For each gradient edge point, the corresponding gradient profile was traced and the profile's sharpness was calculated, and for each non-edge point, the dispersion was calculated. With the sharpness or dispersion, the kernel coefficients of bi-cubic interpolation can be obtained and can be used as the central point to complete the bi-cubic interpolation calculation. Compared with bi-cubic interpolation and bilinear interpolation, the TDAGI algorithm is more accurate. Furthermore, the TDAGI algorithm has the advantage of gradient keeping. Therefore, TDAGI can be used as an alternative method in the dose interpolation of TPS in IMRT.
ObjectivesTo investigate simple assess method of the degree of low transvalvular gradient aortic stenosis patients with impaired left ventricular function and to investigate aortic valve replacement indications, short and mid-term outcome of this kind of patients. MethodsWe retrospectively analyzed the clinical data of 21 low-gradient patients with impaired left ventricular function in our hospital from January 2011 through May 2014. There were 15 males and 6 females aged 41-66 (54.6± 10.7) years with mean aortic transvalvular gradient less than 40 mm Hg and left ventricular ejection fraction (LVEF) less than 50%. ResultsIn response to dobutamine echocardiography stress test, 20 patients underwent aortic valve replacement. The result of intraoperative pathology showed 11 patients were with bicuspid aortic valve malformation, 4 patients with degenerative changes, 4 patients with rheumatic disease. During the same period, 3 patients underwent atrial fibrillation ablation, 1 patient with ascending aorta replacement, 2 patients with coronary artery bypass grafting, 1 patient with mitral valvuloplasty. One patient died of multiple organ failure on the fourth day after operation. The remaining patients recovered. The patients were followed up for 3 to 37 months after operation. Heart function of majority improved to gradeⅠorⅡin 3 months after surgery. The result of echocardiogram showed prosthetic valve function was good and LVEF increased (preoperative 35.7%± 8.2% vs. postoperative 49.4%± 7.2%). One patient suffered sudden death of unknown cause in the 11th months after operation. ConclusionsFor patients whose dobutamine echocardiography stress test displayed with true severe aortic stenosis and left ventricular contractile reserve capacity, after aortic valve replacement and relief of the obstruction, the left ventricular afterload decreases significantly, the left ventricular function also improves, LVEF and the quality of life improve significantly after operation.
Objective To analyze the relationship between end-tidal carbon dioxide partial pressure (PETCO2) and arterial CO2 pressure (PaCO2) in invasive ventilated patients. Methods An observational study was conducted in adult patients admitted to Intensive Care Unit (ICU) between June 2016 and March 2017. Samples were immediately analyzed for PaCO2 using a blood gas analyzer. At the same time the arterial to end-tidal CO2 gradient was determined. Relationship in different mechanical ventilation modes, disease categories and PaO2/FiO2 were analyzed in this study. Results A total of 225 arterial blood gases were obtained from the 104 patients. In each of these modes the PETCO2 was generally lower than the PaCO2. There was a positive correlation between PaCO2 and PETCO2 regardless of different mode (r=0.70, Y=11.08+0.77X). A positive correlation was found in SIMV and SPONT modes, but not in A/C mode. The relationship between PaCO2 and PETCO2 in COPD, trauma, cerebrovascular disease and severe pneumonia patients shown a positive correlation (r value was 0.76, 0.64, 0.53, and 0.56, respectively). There was a significant correlation whether PaCO2/FiO2<200 mm Hg (r=0.69, P<0.001) or ≥200 mm Hg (r=0.71, P<0.001). Conclusions The results of this study show that PETCO2 monitoring accurately reflects PaCO2 during mechanical ventilation. A positive correlation is found in different ventilation modes, regardless of disease categories or PaCO2/FiO2.
The peak period of cardiovascular disease (CVD) is around the time of awakening in the morning, which may be related to the surge of sympathetic activity at the end of nocturnal sleep. This paper chose 140 participants as study object, 70 of which had occurred CVD events while the rest hadn’t during a two-year follow-up period. A two-layer model was proposed to investigate whether hypnopompic heart rate variability (HRV) was informative to distinguish these two types of participants. In the proposed model, the extreme gradient boosting algorithm (XGBoost) was used to construct a classifier in the first layer. By evaluating the feature importance of the classifier, those features with larger importance were fed into the second layer to construct the final classifier. Three machine learning algorithms, i.e., XGBoost, random forest and support vector machine were employed and compared in the second layer to find out which one can achieve the highest performance. The results showed that, with the analysis of hypnopompic HRV, the XGBoost+XGBoost model achieved the best performance with an accuracy of 84.3%. Compared with conventional time-domain and frequency-domain features, those features derived from nonlinear dynamic analysis were more important to the model. Especially, modified permutation entropy at scale 1 and sample entropy at scale 3 were relatively important. This study might have significance for the prevention and diagnosis of CVD, as well as for the design of CVD-risk assessment system.
Heart sound is one of the common medical signals for diagnosing cardiovascular diseases. This paper studies the binary classification between normal or abnormal heart sounds, and proposes a heart sound classification algorithm based on the joint decision of extreme gradient boosting (XGBoost) and deep neural network, achieving a further improvement in feature extraction and model accuracy. First, the preprocessed heart sound recordings are segmented into four status, and five categories of features are extracted from the signals based on segmentation. The first four categories of features are sieved through recursive feature elimination, which is used as the input of the XGBoost classifier. The last category is the Mel-frequency cepstral coefficient (MFCC), which is used as the input of long short-term memory network (LSTM). Considering the imbalance of the data set, these two classifiers are both improved with weights. Finally, the heterogeneous integrated decision method is adopted to obtain the prediction. The algorithm was applied to the open heart sound database of the PhysioNet Computing in Cardiology(CINC) Challenge in 2016 on the PhysioNet website, to test the sensitivity, specificity, modified accuracy and F score. The results were 93%, 89.4%, 91.2% and 91.3% respectively. Compared with the results of machine learning, convolutional neural networks (CNN) and other methods used by other researchers, the accuracy and sensibility have been obviously improved, which proves that the method in this paper could effectively improve the accuracy of heart sound signal classification, and has great potential in the clinical auxiliary diagnosis application of some cardiovascular diseases.