Background Quantitative flow ratio(QFR)based lesion selection for percutaneous coronary intervention(PCI)treatment has shown clinical benefits in terms of reduced risk for myocardial infarction and repeat revasculariz...Background Quantitative flow ratio(QFR)based lesion selection for percutaneous coronary intervention(PCI)treatment has shown clinical benefits in terms of reduced risk for myocardial infarction and repeat revascularization.Whether this benefit is consistent across different age groups still needs further investigation.Methods In this prespecified subgroup study of FAVORⅢChina trial,we compared long-term clinical outcomes between QFR-guided and angiography-guided PCI among different age groups among 3825 enrolled subjects.The primary endpoint was major adverse cardiac events(MACEs),a composite of all-cause death,myocardial infarction,and ischemia-driven revascularization.Results Of the 3825 patients,1717(44.9%)were aged≥65 years.At baseline,patients≥65 had higher rates of hypertension,hyperlipidaemia,stroke history(P<0.0001),and peripheral vascular disease(P=0.024)and had higher SYNTAX scores(P=0.0095).Compared with standard angiography guidance,the QFR-guided strategy consistently reduced the 1-year(≥65 years,6.04%vs.9.19%,HR=0.65,95%CI:0.46–0.92;<65 years,5.53%vs.8.43%,HR=0.65,95%CI:0.47–0.91)and 3-year MACE rates in both age groups(≥65 years,11.8%vs.15.2%,HR:0.75,95%CI:0.58–0.98;<65 years,9.5%vs.14.6%,HR=0.63;95%CI:0.49–0.81),without a significant interaction(Pinteraction=0.99).Within the QFR-guided group,the 3-year MACE rate in patients with deferred vessels was numerically greater in patients aged≥65 years than in those aged<65 years(8.3%vs.3.0%,P=0.10).Conclusions Although with higher rate of comorbidities and more complex coronary anatomy,the long-term benefit of the QFR-guided PCI strategy remained consistent in patients≥65 years,compared with those<65 years.展开更多
Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound （HIFU） is beginning to offer a potential noninvasive alte...Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound （HIFU） is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements （diameter=1.4 cm and frequency=l MHz） were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume （a 2 cm×2 cm×3 cm volume） at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.展开更多
High-intensity focused ultrasound (HIFU) has attracted increasing interests as a promising noninvasive modality for the treatment of deep tumors in the thoracic and abdominal cavity.A 90-element HIFU spherical phased ...High-intensity focused ultrasound (HIFU) has attracted increasing interests as a promising noninvasive modality for the treatment of deep tumors in the thoracic and abdominal cavity.A 90-element HIFU spherical phased array applicator operated at 1 MHz has been developed for deep tissue ablation.The spherical array with a 5 cm wide central hole has a 21 cm diameter and an 18 cm radius of curvature.Annular element distribution with unequal element spacing is used to reduce the number of elements.The array is constructed with piezoelectric lead zirconate titanate (PZT-8) circular elements that are 1.4 cm in diameter and have a wall with thickness of 0.2 cm.The array offers an effective ablating depth of at least 8 cm in the tissue for both simulations and ex vivo experiments.The simulations demonstrate that the developed array can steer the focus with good quality of intensity distributions up to 6 mm off center over ranges from 17 to 21 cm when the water depth is set at 11 cm.We also present the beam focusing capability in deep tissue through a series of ex vivo experiments by measuring discoloration areas after sonications.These results indicate that the developed array is ideal for the ablation of deep-seated tissue.展开更多
Probability density function (PDF) method is proposed for analysing the structure of the reconstructed attractor in computing the correlation dimensions of RR intervals of ten normal old men. PDF contains important in...Probability density function (PDF) method is proposed for analysing the structure of the reconstructed attractor in computing the correlation dimensions of RR intervals of ten normal old men. PDF contains important information about the spatial distribution of the phase points in the reconstructed attractor. To the best of our knowledge, it is the first time that the PDF method is put forward for the analysis of the reconstructed attractor structure. Numerical simulations demonstrate that the cardiac systems of healthy old men are about 6-6.5 dimensional complex dynamical systems. It is found that PDF is not symmetrically distributed when time delay is small, while PDF satisfies Gaussian distribution when time delay is big enough. A cluster effect mechanism is presented to explain this phenomenon. By studying the shape of PDFs, that the roles played by time delay are more important than embedding dimension in the reconstruction is clearly indicated. Results have demonstrated that the PDF method represents a promising numerical approach for the observation of the reconstructed attractor structure and may provide more information and new diagnostic potential of the analyzed cardiac system.展开更多
A new speckle suppression method in contourlet domain was presented. By modeling the subband contourlet coefficients of the ultrasound images after logarithmic transform as generalized Gaussian distribution (GGD), we ...A new speckle suppression method in contourlet domain was presented. By modeling the subband contourlet coefficients of the ultrasound images after logarithmic transform as generalized Gaussian distribution (GGD), we gave a scale-adaptive threshold in Bayesian framework. Experimental results of both synthetic and clinical ultrasound images show that our method has a better performance on speckle suppressing than the wavelet-based method while well preserving the feature details.展开更多
A rapid and practical method is proposed to reconstruct surface based on the linked structured light stripes which are produced by structured light projection.The subpixel points on a stripe are linked firstly one by ...A rapid and practical method is proposed to reconstruct surface based on the linked structured light stripes which are produced by structured light projection.The subpixel points on a stripe are linked firstly one by one to form a stripe ensemble which is then transformed to a point ensemble in 3D space.The initial mesh with local optimization is generated by triangulating each two adjacent point ensembles.In order to obtain a better mesh,our improved edge flipping algorithm is employed to optimize the initial mesh globally.Because of employing the information of the linked structured stripes,our reconstruction algorithm is performed fastly.Moreover,the subpixel points on each stripe are already linked on the captured images such that they do not require the high sampling density.The experiments show that the proposed method constructs a surface rapidly and effectively.展开更多
A fast two-stage geometric active contour algorithm for image segmentation is developed. First, the Eikonal equation problem is quickly solved using an improved fast sweeping method, and a criterion of local minimum o...A fast two-stage geometric active contour algorithm for image segmentation is developed. First, the Eikonal equation problem is quickly solved using an improved fast sweeping method, and a criterion of local minimum of area gradient (LMAG) is presented to extract the optimal arrival time. Then, the final time function is passed as an initial state to an area and length minimizing flow model, which adjusts the interface more accurately and prevents it from leaking. For object with complete and salient edge, using the first stage only is able to obtain an ideal result, and this results in a time complexity of O(M), where M is the number of points in each coordinate direction. Both stages are needed for convoluted shapes, but the computation cost can be drastically reduced. Efficiency of the algorithm is verified in segmentation experiments of real images with different feature.展开更多
BACKGROUND Intermediate coronary lesions(ICLs)are highly prevalent but ported mixed prognosis.Radial strain has been associated with plaque vulnerability,yet its role in predicting lesion progression is largely unknow...BACKGROUND Intermediate coronary lesions(ICLs)are highly prevalent but ported mixed prognosis.Radial strain has been associated with plaque vulnerability,yet its role in predicting lesion progression is largely unknown.The purpose of this study was to determine the predictive value of angiography-derived radial wall strain(RWS)for progression of untreated non-culprit ICLs.METHODS Post-hoc analysis was conducted in a study cohort including 603 consecutive patients with 808 ICLs identified at index procedure with angiographic follow-up of up to two years.RWS analysis was performed on selected angiographic frames with minimal foreshortening and vessel overlap.Lesion progression was defined as≥20%increase in percent diameter stenosis.RESULTS Lesion progression occurred in 49 ICLs(6.1%)with a median follow-up period of 16.8 months.Maximal RWS(RWSmax),frequently located at the proximal and throat plaque regions,distinguished progressive ICLs from silent ones.The largest area under the curve value of 0.75(95%CI:0.67–0.82,P<0.001)was reached at the optimal RWSmax cutoff value of>12.6%.According to this threshold,178 ICLs were classified as having a high strain pattern.Exposure to a high strain amplitude with RWS_(max)>12.6%was independently associated with an increased risk of lesion progression(adjusted HR=6.82,95%CI:3.67–12.66,P<0.001).CONCLUSIONS Assessment of RWS from coronary angiography is feasible and provides independent prognostic value in patients with untreated ICLs.展开更多
In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,...In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%.展开更多
A method of medical image segmentation based on support vector machine (SVM) for density estimation is presented. We used this estimator to construct a prior model of the image intensity and curvature profile of the s...A method of medical image segmentation based on support vector machine (SVM) for density estimation is presented. We used this estimator to construct a prior model of the image intensity and curvature profile of the structure from training images. When segmenting a novel image similar to the training images, the technique of narrow level set method is used. The higher dimensional surface evolution metric is defined by the prior model instead of by energy minimization function. This method offers several advantages. First, SVM for density estimation is consistent and its solution is sparse. Second, compared to the traditional level set methods, this method incorporates shape information on the object to be segmented into the segmentation process. Segmentation results are demonstrated on synthetic images, MR images and ultrasonic images.展开更多
Outliers in point clouds affect the performance of surface reconstruction directly. Most of outlier removal methods just remove those outliers far away from the real surface and are only applied to handle watertight s...Outliers in point clouds affect the performance of surface reconstruction directly. Most of outlier removal methods just remove those outliers far away from the real surface and are only applied to handle watertight surface. In this paper, a two-step outlier removal procedure is proposed to filter the point clouds acquired from the gray code and line-shifting technique. The first step is to remove the outliers far away from the real surface. Some feature points are extracted from the point clouds to construct an initial surface. The points with distances to the initial surface greater than a given threshold are removed as distant outliers. The retained points are linked into lines in each structured light sheet using their Voronoi diagrams. Some of lines which are very close to the real surface are removed as near outliers in the second step. The experimental results show that the proposed method is very effective in removing outliers for surface reconstruction.展开更多
The feasibility of a new full bridge high intensity focused ultrasound(HIFU) amplifier system with harmonic cancellation is evaluated in this study. Harmonic cancellation technique is applied to these power amplifiers...The feasibility of a new full bridge high intensity focused ultrasound(HIFU) amplifier system with harmonic cancellation is evaluated in this study. Harmonic cancellation technique is applied to these power amplifiers, which can eliminate the 3rd harmonic and all even harmonics. Since this technique requires two channels of phase signal to control one channel of power amplifier, the signal generator is required to double its output. The transducer array proposed in this study has 100 elements. So we choose an FPGA chip to generate 200 driving signals, and each channel has a phase resolution of 2ns, less than 1°. The phase signal from the FPGA meets the requirement of driving the power amplifiers. The output waveform of one channel of power amplifier(voltage across the transducer) is evaluated, and shows fewer harmonic components.展开更多
Ultrasound hyperthermia is one of the most important methods in tumor treatment and characterized by non-invasiveness. Magnetic resonance imaging(MRI)-based temperature mapping techniques are safe compared with invasi...Ultrasound hyperthermia is one of the most important methods in tumor treatment and characterized by non-invasiveness. Magnetic resonance imaging(MRI)-based temperature mapping techniques are safe compared with invasive methods and have been applied to detect temperature changes for a variety of applications. Among these techniques, the proton resonance frequency(PRF) method is relatively advanced. With a temperature measuring experiment, the effectiveness of PRF method has been proved, because the outcome temperature curve and the real temperature curve fit well. After that, an experiment has been conducted on tumors inside rabbit legs and the result indicates that this system is able to performance hyperthermia at targets based on PRF method in temperature mapping.展开更多
This paper describes a new method for three-dimensional medical image registration. In the interactive image-guided HIFU （ High Intensity Focused Ultrasound） therapy system, a fast and precise localization of the tu...This paper describes a new method for three-dimensional medical image registration. In the interactive image-guided HIFU （ High Intensity Focused Ultrasound） therapy system, a fast and precise localization of the tumor is very important. An automatic system is developed for registering pre-operative MR images with intra-operative ultrasound images based on the vessels visible in both of the modalities. When the MR and the ultrasound images are aligned, the eenterline points of the vessels in the MR image will align with bright intensities in the ultrasound image. The method applies an optimization strategy combining the genetic algorithm with the conjugated gradients algorithm to minimize the objective function. It provides a feasible way of determining the global solution and makes the method robust to local maximum and insensitive to initial position. Two experiments were designed to evaluate the method, and the results show that our method has better registration accuracy and convergence rate than the other two classic algorithms.展开更多
A new hierarchical approach called bintree energy segmentation was presented for color image segmentation. The image features are extracted by adaptive clustering on multi-channel data at each level and used as the cr...A new hierarchical approach called bintree energy segmentation was presented for color image segmentation. The image features are extracted by adaptive clustering on multi-channel data at each level and used as the criteria to dynamically select the best chromatic channel, where the segmentation is carried out. In this approach, an extended direct energy computation method based on the Chan-Vese model was proposed to segment the selected channel, and the segmentation outputs are then fused with other channels into new images, from which a new channel with better features is selected for the second round segmentation. This procedure is repeated until the preset condition is met. Finally, a binary segmentation tree is formed, in which each leaf represents a class of objects with a distinctive color. To facilitate the data organization, image background is employed in segmentation and channels fusion. The bintree energy segmentation exploits color information involved in all channels data and tries to optimize the global segmentation result by choosing the 'best' channel for segmentation at each level. The experiments show that the method is effective in speed, accuracy and flexibility.展开更多
Exploring the distribution of focused ultrasound field attracts more and more investigators' attention.Making use of the heat property of focused ultrasound, we can measure the distribution of temperature to calcu...Exploring the distribution of focused ultrasound field attracts more and more investigators' attention.Making use of the heat property of focused ultrasound, we can measure the distribution of temperature to calculate the distribution of focused ultrasound field. During the exploration, we found that the temperature rise rate had a liner relation to sound intensity. So we conducted experiments and got the infrared images with noise. In order to obtain an accurate distribution of focused ultrasound field, it's necessary to find out a solution to get rid of the noise in infrared images. In traditional, we use hydrophone to explore the distribution of focused ultrasound field even in nonlinear area. So the result got by hydrophone was considered as standard. So the investigation was focused on the experimental validation of a filter which was the most suitable way for image process of infrared chart. So the ability of the filter should be that removing most noise and the distribution of temperature rise rate is unchanged. Six kinds of filters were used to deal with the raw data to obtain related information, from the results, we drew a conclusion that gauss filter was superior to the others filter, and a non- distortion distribution of focused ultrasound field would be get by the use of Gaussian filter.展开更多
BACKGROUND The recently introduced ultrasonic flow ratio(UFR),is a novel fast computational method to derive fractional flow reserve(FFR)from intravascular ultrasound(IVUS)images.In the present study,we evaluate the d...BACKGROUND The recently introduced ultrasonic flow ratio(UFR),is a novel fast computational method to derive fractional flow reserve(FFR)from intravascular ultrasound(IVUS)images.In the present study,we evaluate the diagnostic performance of UFR in patients with intermediate left main(LM)stenosis.METHODS This is a prospective,single center study enrolling consecutive patients with presence of intermediated LM lesions(diameter stenosis of 30%-80%by visual estimation)underwent IVUS and FFR measurement.An independent core laboratory assessed offline UFR and IVUS-derived minimal lumen area(MLA)in a blinded fashion.RESULTS Both UFR and FFR were successfully achieved in 41 LM patients(mean age,62.0±9.9 years,46.3%diabetes).An acceptable correlation between UFR and FFR was identified(r=0.688,P<0.0001),with an absolute numerical difference of 0.03(standard difference:0.01).The area under the curve(AUC)in diagnosis of physiologically significant coronary stenosis for UFR was 0.94(95%CI:0.87-1.01),which was significantly higher than angiographic identified stenosis>50%(AUC=0.66,P<0.001)and numerically higher than IVUS-derived MLA(AUC=0.82;P=0.09).Patient level diagnostic accuracy,sensitivity and specificity for UFR to identify FFR≤0.80 was 82.9%(95%CI:70.2-95.7),93.1%(95%CI:82.2-100.0),58.3%(95%CI:26.3-90.4),respectively.CONCLUSION In patients with intermediate LM diseases,UFR was proved to be associated with acceptable correlation and high accuracy with pressure wire-based FFR as standard reference.The present study supports the use of UFR for functional evaluation of intermediate LM stenosis.展开更多
Background:The FAVOR(Comparison of Quantitative Flow Ratio Guided and Angiography Guided Percutaneous Intervention in Patients with Coronary Artery Disease)III China trial demonstrated that percutaneous coronary inter...Background:The FAVOR(Comparison of Quantitative Flow Ratio Guided and Angiography Guided Percutaneous Intervention in Patients with Coronary Artery Disease)III China trial demonstrated that percutaneous coronary intervention(PCI)lesion selection using quantitative flow ratio(QFR)measurement,a novel angiography-based approach for estimating fractional flow reserve,improved two-year clinical outcomes compared with standard angiography guidance.This study aimed to assess the cost-effectiveness of QFR-guided PCI from the perspective of the current Chinese healthcare system.Methods:This study is a pre-specified analysis of the FAVOR III China trial,which included 3825 patients randomized between December 25,2018,and January 19,2020,from 26 centers in China.Patients with stable or unstable angina pectoris or those≥72 hours post-myocardial infarction who had at least one lesion with a diameter stenosis between 50%and 90%in a coronary artery with a≥2.5 mm reference vessel diameter by visual assessment were randomized to a QFR-guided strategy or an angiography-guided strategy with 1:1 ratio.During the two-year follow-up,data were collected on clinical outcomes,quality-adjusted life-years(QALYs),estimated costs of index procedure hospitalization,outpatient cardiovascular medication use,and rehospitalization due to major adverse cardiac and cerebrovascular events(MACCE).The primary analysis calculated the incremental cost-effectiveness ratio(ICER)as the cost per MACCE avoided.An ICER of¥10,000/MACCE event avoided was considered economically attractive in China.Results:At two years,the QFR-guided group demonstrated a reduced rate of MACCE compared to the angiography-guided group(10.8%vs.14.7%,P<0.01).Total two-year costs were similar between the groups(¥50,803±21,121 vs.¥50,685±23,495,P=0.87).The ICER for the QFR-guided strategy was¥3055 per MACCE avoided,and the probability of QFR being economically attractive was 64%at a willingness-to-pay threshold of¥10,000/MACCE avoided.Sensitivity analysis showed that QFR-guided PCI would become cost-saving if the cost of QFR were below¥3682(current cost:¥3800).Cost-utility analysis yielded an ICER of¥56,163 per QALY gained,with a 53%probability of being cost-effective at a willingness-to-pay threshold of¥85,000 per QALY gained.Conclusion:In patients undergoing PCI,a QFR-guided strategy appears economically attractive compared to angiographic guidance from the perspective of the Chinese healthcare system.展开更多
文摘Background Quantitative flow ratio(QFR)based lesion selection for percutaneous coronary intervention(PCI)treatment has shown clinical benefits in terms of reduced risk for myocardial infarction and repeat revascularization.Whether this benefit is consistent across different age groups still needs further investigation.Methods In this prespecified subgroup study of FAVORⅢChina trial,we compared long-term clinical outcomes between QFR-guided and angiography-guided PCI among different age groups among 3825 enrolled subjects.The primary endpoint was major adverse cardiac events(MACEs),a composite of all-cause death,myocardial infarction,and ischemia-driven revascularization.Results Of the 3825 patients,1717(44.9%)were aged≥65 years.At baseline,patients≥65 had higher rates of hypertension,hyperlipidaemia,stroke history(P<0.0001),and peripheral vascular disease(P=0.024)and had higher SYNTAX scores(P=0.0095).Compared with standard angiography guidance,the QFR-guided strategy consistently reduced the 1-year(≥65 years,6.04%vs.9.19%,HR=0.65,95%CI:0.46–0.92;<65 years,5.53%vs.8.43%,HR=0.65,95%CI:0.47–0.91)and 3-year MACE rates in both age groups(≥65 years,11.8%vs.15.2%,HR:0.75,95%CI:0.58–0.98;<65 years,9.5%vs.14.6%,HR=0.63;95%CI:0.49–0.81),without a significant interaction(Pinteraction=0.99).Within the QFR-guided group,the 3-year MACE rate in patients with deferred vessels was numerically greater in patients aged≥65 years than in those aged<65 years(8.3%vs.3.0%,P=0.10).Conclusions Although with higher rate of comorbidities and more complex coronary anatomy,the long-term benefit of the QFR-guided PCI strategy remained consistent in patients≥65 years,compared with those<65 years.
基金supported by the National Natural Science Foundation of China (No. 30800246)Shanghai Key Technologies R&D Programof China (No. 09441900500)
文摘Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound （HIFU） is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements （diameter=1.4 cm and frequency=l MHz） were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume （a 2 cm×2 cm×3 cm volume） at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.
基金the National Natural Science Foundation of China(No. 30800246)the Shanghai Key Technologies R&D Program of China(No. 09441500900)the Med-X Shanghai Engineering Center Foundation(No. 08DZ2211201)
文摘High-intensity focused ultrasound (HIFU) has attracted increasing interests as a promising noninvasive modality for the treatment of deep tumors in the thoracic and abdominal cavity.A 90-element HIFU spherical phased array applicator operated at 1 MHz has been developed for deep tissue ablation.The spherical array with a 5 cm wide central hole has a 21 cm diameter and an 18 cm radius of curvature.Annular element distribution with unequal element spacing is used to reduce the number of elements.The array is constructed with piezoelectric lead zirconate titanate (PZT-8) circular elements that are 1.4 cm in diameter and have a wall with thickness of 0.2 cm.The array offers an effective ablating depth of at least 8 cm in the tissue for both simulations and ex vivo experiments.The simulations demonstrate that the developed array can steer the focus with good quality of intensity distributions up to 6 mm off center over ranges from 17 to 21 cm when the water depth is set at 11 cm.We also present the beam focusing capability in deep tissue through a series of ex vivo experiments by measuring discoloration areas after sonications.These results indicate that the developed array is ideal for the ablation of deep-seated tissue.
文摘Probability density function (PDF) method is proposed for analysing the structure of the reconstructed attractor in computing the correlation dimensions of RR intervals of ten normal old men. PDF contains important information about the spatial distribution of the phase points in the reconstructed attractor. To the best of our knowledge, it is the first time that the PDF method is put forward for the analysis of the reconstructed attractor structure. Numerical simulations demonstrate that the cardiac systems of healthy old men are about 6-6.5 dimensional complex dynamical systems. It is found that PDF is not symmetrically distributed when time delay is small, while PDF satisfies Gaussian distribution when time delay is big enough. A cluster effect mechanism is presented to explain this phenomenon. By studying the shape of PDFs, that the roles played by time delay are more important than embedding dimension in the reconstruction is clearly indicated. Results have demonstrated that the PDF method represents a promising numerical approach for the observation of the reconstructed attractor structure and may provide more information and new diagnostic potential of the analyzed cardiac system.
基金the National Basic Research Program(973) of China (No. 2003CB716103)
文摘A new speckle suppression method in contourlet domain was presented. By modeling the subband contourlet coefficients of the ultrasound images after logarithmic transform as generalized Gaussian distribution (GGD), we gave a scale-adaptive threshold in Bayesian framework. Experimental results of both synthetic and clinical ultrasound images show that our method has a better performance on speckle suppressing than the wavelet-based method while well preserving the feature details.
基金the Fundamental Research Funds for the Central Universities of SCUT (No.2009ZM0235)the National Natural Science Foundation of China (No.30470488)
文摘A rapid and practical method is proposed to reconstruct surface based on the linked structured light stripes which are produced by structured light projection.The subpixel points on a stripe are linked firstly one by one to form a stripe ensemble which is then transformed to a point ensemble in 3D space.The initial mesh with local optimization is generated by triangulating each two adjacent point ensembles.In order to obtain a better mesh,our improved edge flipping algorithm is employed to optimize the initial mesh globally.Because of employing the information of the linked structured stripes,our reconstruction algorithm is performed fastly.Moreover,the subpixel points on each stripe are already linked on the captured images such that they do not require the high sampling density.The experiments show that the proposed method constructs a surface rapidly and effectively.
文摘A fast two-stage geometric active contour algorithm for image segmentation is developed. First, the Eikonal equation problem is quickly solved using an improved fast sweeping method, and a criterion of local minimum of area gradient (LMAG) is presented to extract the optimal arrival time. Then, the final time function is passed as an initial state to an area and length minimizing flow model, which adjusts the interface more accurately and prevents it from leaking. For object with complete and salient edge, using the first stage only is able to obtain an ideal result, and this results in a time complexity of O(M), where M is the number of points in each coordinate direction. Both stages are needed for convoluted shapes, but the computation cost can be drastically reduced. Efficiency of the algorithm is verified in segmentation experiments of real images with different feature.
基金supported by the National Natural Science Foundation of China(No.82020108015&No.81871460&No.82170333)。
文摘BACKGROUND Intermediate coronary lesions(ICLs)are highly prevalent but ported mixed prognosis.Radial strain has been associated with plaque vulnerability,yet its role in predicting lesion progression is largely unknown.The purpose of this study was to determine the predictive value of angiography-derived radial wall strain(RWS)for progression of untreated non-culprit ICLs.METHODS Post-hoc analysis was conducted in a study cohort including 603 consecutive patients with 808 ICLs identified at index procedure with angiographic follow-up of up to two years.RWS analysis was performed on selected angiographic frames with minimal foreshortening and vessel overlap.Lesion progression was defined as≥20%increase in percent diameter stenosis.RESULTS Lesion progression occurred in 49 ICLs(6.1%)with a median follow-up period of 16.8 months.Maximal RWS(RWSmax),frequently located at the proximal and throat plaque regions,distinguished progressive ICLs from silent ones.The largest area under the curve value of 0.75(95%CI:0.67–0.82,P<0.001)was reached at the optimal RWSmax cutoff value of>12.6%.According to this threshold,178 ICLs were classified as having a high strain pattern.Exposure to a high strain amplitude with RWS_(max)>12.6%was independently associated with an increased risk of lesion progression(adjusted HR=6.82,95%CI:3.67–12.66,P<0.001).CONCLUSIONS Assessment of RWS from coronary angiography is feasible and provides independent prognostic value in patients with untreated ICLs.
基金support by the National SKA Program of ChinaNo.2022SKA0110100+1 种基金the CAS Interdisciplinary Innovation Team(JCTD-2019-05)the science research grants from the China Manned Space Project with No.CMS-CSST-2021-B01。
文摘In the neutral hydrogen(H I)galaxy survey,a significant challenge is to identify and extract the H I galaxy signal from the observational data contaminated by radio frequency interference(RFI).For a drift-scan survey,or more generally a survey of a spatially continuous region,in the time-ordered spectral data,the H I galaxies and RFI all appear as regions that extend an area in the time-frequency waterfall plot,so the extraction of the H I galaxies and RFI from such data can be regarded as an image segmentation problem,and machine-learning methods can be applied to solve such problems.In this study,we develop a method to effectively detect and extract signals of H I galaxies based on a Mask R-CNN network combined with the PointRend method.By simulating FAST-observed galaxy signals and potential RFI impact,we created a realistic data set for the training and testing of our neural network.We compared five different architectures and selected the best-performing one.This architecture successfully performs instance segmentation of H I galaxy signals in the RFI-contaminated time-ordered data,achieving a precision of 98.64%and a recall of 93.59%.
基金Project (No. 2003CB716103) supported by the National BasicResearch Program (973) of China and the Key Lab for Image Proc-essing and Intelligent Control of National Education Ministry, China
文摘A method of medical image segmentation based on support vector machine (SVM) for density estimation is presented. We used this estimator to construct a prior model of the image intensity and curvature profile of the structure from training images. When segmenting a novel image similar to the training images, the technique of narrow level set method is used. The higher dimensional surface evolution metric is defined by the prior model instead of by energy minimization function. This method offers several advantages. First, SVM for density estimation is consistent and its solution is sparse. Second, compared to the traditional level set methods, this method incorporates shape information on the object to be segmented into the segmentation process. Segmentation results are demonstrated on synthetic images, MR images and ultrasonic images.
基金the National Natural Science Foundation of China (No. 30470488)
文摘Outliers in point clouds affect the performance of surface reconstruction directly. Most of outlier removal methods just remove those outliers far away from the real surface and are only applied to handle watertight surface. In this paper, a two-step outlier removal procedure is proposed to filter the point clouds acquired from the gray code and line-shifting technique. The first step is to remove the outliers far away from the real surface. Some feature points are extracted from the point clouds to construct an initial surface. The points with distances to the initial surface greater than a given threshold are removed as distant outliers. The retained points are linked into lines in each structured light sheet using their Voronoi diagrams. Some of lines which are very close to the real surface are removed as near outliers in the second step. The experimental results show that the proposed method is very effective in removing outliers for surface reconstruction.
基金the National Natural Science Foundation of China(No.30800246)the Shanghai Key Technologies R&D Program of China(No.09441900500)the Research Program of Shanghai Education Commission(No.14CXY05)
文摘The feasibility of a new full bridge high intensity focused ultrasound(HIFU) amplifier system with harmonic cancellation is evaluated in this study. Harmonic cancellation technique is applied to these power amplifiers, which can eliminate the 3rd harmonic and all even harmonics. Since this technique requires two channels of phase signal to control one channel of power amplifier, the signal generator is required to double its output. The transducer array proposed in this study has 100 elements. So we choose an FPGA chip to generate 200 driving signals, and each channel has a phase resolution of 2ns, less than 1°. The phase signal from the FPGA meets the requirement of driving the power amplifiers. The output waveform of one channel of power amplifier(voltage across the transducer) is evaluated, and shows fewer harmonic components.
基金the National Natural Science Foundation of China(No.30800246)the Shanghai Key Technologies R&D Program of China(No.09441900500)the Research Program of Shanghai Education Commission(No.14CXY05)
文摘Ultrasound hyperthermia is one of the most important methods in tumor treatment and characterized by non-invasiveness. Magnetic resonance imaging(MRI)-based temperature mapping techniques are safe compared with invasive methods and have been applied to detect temperature changes for a variety of applications. Among these techniques, the proton resonance frequency(PRF) method is relatively advanced. With a temperature measuring experiment, the effectiveness of PRF method has been proved, because the outcome temperature curve and the real temperature curve fit well. After that, an experiment has been conducted on tumors inside rabbit legs and the result indicates that this system is able to performance hyperthermia at targets based on PRF method in temperature mapping.
文摘This paper describes a new method for three-dimensional medical image registration. In the interactive image-guided HIFU （ High Intensity Focused Ultrasound） therapy system, a fast and precise localization of the tumor is very important. An automatic system is developed for registering pre-operative MR images with intra-operative ultrasound images based on the vessels visible in both of the modalities. When the MR and the ultrasound images are aligned, the eenterline points of the vessels in the MR image will align with bright intensities in the ultrasound image. The method applies an optimization strategy combining the genetic algorithm with the conjugated gradients algorithm to minimize the objective function. It provides a feasible way of determining the global solution and makes the method robust to local maximum and insensitive to initial position. Two experiments were designed to evaluate the method, and the results show that our method has better registration accuracy and convergence rate than the other two classic algorithms.
基金The National Basic Research Program (973) of China (No. 2003CB716103) The Key Lab of Image Processing & Intelligent control of National Education Ministry (No. TKLJ0306)
文摘A new hierarchical approach called bintree energy segmentation was presented for color image segmentation. The image features are extracted by adaptive clustering on multi-channel data at each level and used as the criteria to dynamically select the best chromatic channel, where the segmentation is carried out. In this approach, an extended direct energy computation method based on the Chan-Vese model was proposed to segment the selected channel, and the segmentation outputs are then fused with other channels into new images, from which a new channel with better features is selected for the second round segmentation. This procedure is repeated until the preset condition is met. Finally, a binary segmentation tree is formed, in which each leaf represents a class of objects with a distinctive color. To facilitate the data organization, image background is employed in segmentation and channels fusion. The bintree energy segmentation exploits color information involved in all channels data and tries to optimize the global segmentation result by choosing the 'best' channel for segmentation at each level. The experiments show that the method is effective in speed, accuracy and flexibility.
基金the National Natural Science Foundation of China(No.30800246)the Shanghai Key Technologies R&D Program of China(No.09441900500)the Research Program of Shanghai Education Commission(No.14CXY05)
文摘Exploring the distribution of focused ultrasound field attracts more and more investigators' attention.Making use of the heat property of focused ultrasound, we can measure the distribution of temperature to calculate the distribution of focused ultrasound field. During the exploration, we found that the temperature rise rate had a liner relation to sound intensity. So we conducted experiments and got the infrared images with noise. In order to obtain an accurate distribution of focused ultrasound field, it's necessary to find out a solution to get rid of the noise in infrared images. In traditional, we use hydrophone to explore the distribution of focused ultrasound field even in nonlinear area. So the result got by hydrophone was considered as standard. So the investigation was focused on the experimental validation of a filter which was the most suitable way for image process of infrared chart. So the ability of the filter should be that removing most noise and the distribution of temperature rise rate is unchanged. Six kinds of filters were used to deal with the raw data to obtain related information, from the results, we drew a conclusion that gauss filter was superior to the others filter, and a non- distortion distribution of focused ultrasound field would be get by the use of Gaussian filter.
基金supported by CAMS Innovation Fund for Medical Sciences(CIFMS)(2022–12M-C&TB-043).
文摘BACKGROUND The recently introduced ultrasonic flow ratio(UFR),is a novel fast computational method to derive fractional flow reserve(FFR)from intravascular ultrasound(IVUS)images.In the present study,we evaluate the diagnostic performance of UFR in patients with intermediate left main(LM)stenosis.METHODS This is a prospective,single center study enrolling consecutive patients with presence of intermediated LM lesions(diameter stenosis of 30%-80%by visual estimation)underwent IVUS and FFR measurement.An independent core laboratory assessed offline UFR and IVUS-derived minimal lumen area(MLA)in a blinded fashion.RESULTS Both UFR and FFR were successfully achieved in 41 LM patients(mean age,62.0±9.9 years,46.3%diabetes).An acceptable correlation between UFR and FFR was identified(r=0.688,P<0.0001),with an absolute numerical difference of 0.03(standard difference:0.01).The area under the curve(AUC)in diagnosis of physiologically significant coronary stenosis for UFR was 0.94(95%CI:0.87-1.01),which was significantly higher than angiographic identified stenosis>50%(AUC=0.66,P<0.001)and numerically higher than IVUS-derived MLA(AUC=0.82;P=0.09).Patient level diagnostic accuracy,sensitivity and specificity for UFR to identify FFR≤0.80 was 82.9%(95%CI:70.2-95.7),93.1%(95%CI:82.2-100.0),58.3%(95%CI:26.3-90.4),respectively.CONCLUSION In patients with intermediate LM diseases,UFR was proved to be associated with acceptable correlation and high accuracy with pressure wire-based FFR as standard reference.The present study supports the use of UFR for functional evaluation of intermediate LM stenosis.
基金This study is supported by grants from the National High Level Hospital Clinical Research Funding(Nos.2022-GSP-GG-20 and 2023-GSP-GG-3)the Capital’s Funds for Health Improvement and Research(No.2022-2-4033)the Chinese Academy of Medical Sciences(No.2022-I2M-C&T-A-009).
文摘Background:The FAVOR(Comparison of Quantitative Flow Ratio Guided and Angiography Guided Percutaneous Intervention in Patients with Coronary Artery Disease)III China trial demonstrated that percutaneous coronary intervention(PCI)lesion selection using quantitative flow ratio(QFR)measurement,a novel angiography-based approach for estimating fractional flow reserve,improved two-year clinical outcomes compared with standard angiography guidance.This study aimed to assess the cost-effectiveness of QFR-guided PCI from the perspective of the current Chinese healthcare system.Methods:This study is a pre-specified analysis of the FAVOR III China trial,which included 3825 patients randomized between December 25,2018,and January 19,2020,from 26 centers in China.Patients with stable or unstable angina pectoris or those≥72 hours post-myocardial infarction who had at least one lesion with a diameter stenosis between 50%and 90%in a coronary artery with a≥2.5 mm reference vessel diameter by visual assessment were randomized to a QFR-guided strategy or an angiography-guided strategy with 1:1 ratio.During the two-year follow-up,data were collected on clinical outcomes,quality-adjusted life-years(QALYs),estimated costs of index procedure hospitalization,outpatient cardiovascular medication use,and rehospitalization due to major adverse cardiac and cerebrovascular events(MACCE).The primary analysis calculated the incremental cost-effectiveness ratio(ICER)as the cost per MACCE avoided.An ICER of¥10,000/MACCE event avoided was considered economically attractive in China.Results:At two years,the QFR-guided group demonstrated a reduced rate of MACCE compared to the angiography-guided group(10.8%vs.14.7%,P<0.01).Total two-year costs were similar between the groups(¥50,803±21,121 vs.¥50,685±23,495,P=0.87).The ICER for the QFR-guided strategy was¥3055 per MACCE avoided,and the probability of QFR being economically attractive was 64%at a willingness-to-pay threshold of¥10,000/MACCE avoided.Sensitivity analysis showed that QFR-guided PCI would become cost-saving if the cost of QFR were below¥3682(current cost:¥3800).Cost-utility analysis yielded an ICER of¥56,163 per QALY gained,with a 53%probability of being cost-effective at a willingness-to-pay threshold of¥85,000 per QALY gained.Conclusion:In patients undergoing PCI,a QFR-guided strategy appears economically attractive compared to angiographic guidance from the perspective of the Chinese healthcare system.
