Vector-Field dynamic X-ray (VF-DXR) using Optical Flow Method

Objectives: To explore the feasibility of Vector-Field DXR (VF-DXR) using optical flow method (OFM). Methods: Five healthy volunteers and five COPD patients were studied. DXR was performed in the standing position using a prototype X-ray system (Konica Minolta Inc., Tokyo, Japan). During the examination, participants took several tidal breaths and one forced breath. DXR image file was converted to the videos with different frames per second (fps): 15 fps, 7.5 fps, five fps, three fps, and 1.5 fps. Pixel-value gradient was calculated by the serial change of pixel value, which was subsequently converted mathematically to motion vector using OFM. Color-coding map and vector projection into horizontal and vertical components were also tested. Results: Dynamic motion of lung and thorax was clearly visualized using VF-DXR with an optimal frame rate of 5 fps. Color-coding map and vector projection into horizontal and vertical components were also presented. VF-DXR technique was also applied in COPD patients. Conclusion: The feasibility of VF-DXR was demonstrated with small number of healthy subjects and COPD patients. Advances in knowledge: A new Vector-Field Dynamic X-ray (VF-DXR) technique is feasible for dynamic visualization of lung, diaphragms, thoracic cage, and cardiac contour.

Energy flux of a vortex field focused using a secant gradient lens

In this paper we simulated the focusing of left circular polarized beam with a second order phase vortex and a second-order cylindrical vector beam by a gradient index Mikaelian lens. It was shown numerically, that there is an area with a negative Poynting vector projection on Z axis, that can be called an area with backward energy flow. Using a cylindrical hole in the output surface of the lens and optimizing it one can obtain a negative flow, which will be situated in the maximum intensity region, unlike to previous papers, in which such backward energy flow regions were situated in a shadow area. Thereby, this lens will work as an “optical magnet”, it will attract Rayleigh particles (with diameter about 1/20 of the wavelength) to its surface.