Dear Editor,We have read and reviewed the article entitled＂The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography...Dear Editor,We have read and reviewed the article entitled＂The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography＂by Zhao et al^（[1]）with great interest.展开更多
Background Optical coherence tomography （OCT） is a new imaging technique capable of obtaining high-resolution intravascular images of small vessels and has been widely used in interventional cardiology. However, app...Background Optical coherence tomography （OCT） is a new imaging technique capable of obtaining high-resolution intravascular images of small vessels and has been widely used in interventional cardiology. However, application of OCT in peripheral pulmonary arteries in patients has been seldom documented. Methods Three patients who were highly suspected peripheral pulmonary arteries thrombi and had undergone CT pulmonary angiography but tested negative for thrombi in peripheral pulmonary arteries were enrolled. Subsequently, OCT imaging was performed in peripheral pulmonary arteries. The patients received more than three-month anticoagulative treatment if thrombi were detected by OCT. Thereafter, OCT re-evaluation of the thrombolized blood vessels detected earlier was performed. The changes of thrombi before and after anticoagulative treatment were compared. Results Three patients underwent OCT imaging of peripheral pulmonary arteries. Thrombi were found in most of imaged vessels in these patients. Red and white thrombi can be differentiated, according to features of the thrombus on OCT images. After anticoagulation treatment, these patients＇ symptoms and hypoxemia improved. Repeated OCT imaging showed that most thrombi disappeared or became smaller. Conclusion OCT may be used as a potential tool for detecting peripheral pulmonary artery thrombi and differentiating red thrombi from white ones.展开更多
Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of su...Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection’s images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers <em>M</em><em><sub>j</sub></em> ranging from 1.47 - 1.71, where the design Mach number is <em>M<sub>d</sub></em> = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types “upright” and “diagonal” of “cross-shaped”. The initial axis-switching is 45<span style="white-space:nowrap;">°</span> within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.展开更多
This report deals with introducing two new techniques based on a novel concept of complex brightness gradient in quantitative schlieren images, “inverse process” and “multi-path integration” for image-noise reduct...This report deals with introducing two new techniques based on a novel concept of complex brightness gradient in quantitative schlieren images, “inverse process” and “multi-path integration” for image-noise reduction. Noise in schlieren images affects the projections (density thickness) images of computerized tomography (CT). One spot noise in the schlieren image appears in a line shape in the density thickness image. Noise effect like an infectious disease spreads from a noisy pixel to the next pixel in the direction of single-path integration. On the one hand, the noise in the schlieren image reduces the quality of the image and quantitative analysis and is undesirable;on the other it is unavoidable. Therefore, the importance of proper noise reduction techniques seems essential and tangible. In the present report, a novel technique “multi-path integration” is proposed for noise reduction in projections images of CT. Multi-path integration is required the schlieren brightness gradient in two orthogonal directions. The 20-directional quantitative schlieren optical system presents only images of schlieren brightness in the horizontal gradient and another 20-directional optical system seems necessary to obtain vertical schlieren brightness gradient, simultaneously. Using the “inverse process”, a new technique enables us to obtain vertical schlieren brightness gradient from horizontal experimental data without the necessity of a new optical system and can be used for obtaining any optional directions of schlieren brightness gradient.展开更多
文摘Dear Editor,We have read and reviewed the article entitled＂The diurnal variation pattern of choroidal thickness in macular region of young healthy female individuals using spectral domain optical coherence tomography＂by Zhao et al^（[1]）with great interest.
文摘Background Optical coherence tomography （OCT） is a new imaging technique capable of obtaining high-resolution intravascular images of small vessels and has been widely used in interventional cardiology. However, application of OCT in peripheral pulmonary arteries in patients has been seldom documented. Methods Three patients who were highly suspected peripheral pulmonary arteries thrombi and had undergone CT pulmonary angiography but tested negative for thrombi in peripheral pulmonary arteries were enrolled. Subsequently, OCT imaging was performed in peripheral pulmonary arteries. The patients received more than three-month anticoagulative treatment if thrombi were detected by OCT. Thereafter, OCT re-evaluation of the thrombolized blood vessels detected earlier was performed. The changes of thrombi before and after anticoagulative treatment were compared. Results Three patients underwent OCT imaging of peripheral pulmonary arteries. Thrombi were found in most of imaged vessels in these patients. Red and white thrombi can be differentiated, according to features of the thrombus on OCT images. After anticoagulation treatment, these patients＇ symptoms and hypoxemia improved. Repeated OCT imaging showed that most thrombi disappeared or became smaller. Conclusion OCT may be used as a potential tool for detecting peripheral pulmonary artery thrombi and differentiating red thrombi from white ones.
文摘Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection’s images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers <em>M</em><em><sub>j</sub></em> ranging from 1.47 - 1.71, where the design Mach number is <em>M<sub>d</sub></em> = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types “upright” and “diagonal” of “cross-shaped”. The initial axis-switching is 45<span style="white-space:nowrap;">°</span> within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.
文摘This report deals with introducing two new techniques based on a novel concept of complex brightness gradient in quantitative schlieren images, “inverse process” and “multi-path integration” for image-noise reduction. Noise in schlieren images affects the projections (density thickness) images of computerized tomography (CT). One spot noise in the schlieren image appears in a line shape in the density thickness image. Noise effect like an infectious disease spreads from a noisy pixel to the next pixel in the direction of single-path integration. On the one hand, the noise in the schlieren image reduces the quality of the image and quantitative analysis and is undesirable;on the other it is unavoidable. Therefore, the importance of proper noise reduction techniques seems essential and tangible. In the present report, a novel technique “multi-path integration” is proposed for noise reduction in projections images of CT. Multi-path integration is required the schlieren brightness gradient in two orthogonal directions. The 20-directional quantitative schlieren optical system presents only images of schlieren brightness in the horizontal gradient and another 20-directional optical system seems necessary to obtain vertical schlieren brightness gradient, simultaneously. Using the “inverse process”, a new technique enables us to obtain vertical schlieren brightness gradient from horizontal experimental data without the necessity of a new optical system and can be used for obtaining any optional directions of schlieren brightness gradient.
