Partical image velocimetry suitable for X-ray projection imaging
A 2D or 3D velocity field is reconstructed from a cross-correlation analysis of image pairs of a sample, without first reconstructing images of the sample spatial structure. The method can be implemented via computer tomographic x-ray particle image velocimetry, using multiple projection angles, with phase contrast images forming dynamic speckle patterns. Estimated cross-correlations may be generated via convolution of a measured autocorrelation function with a velocity probability density function, and the velocity coefficients iteratively optimized to minimize the error between the estimated cross-correlations and the measured cross-correlations. The method may be applied to measure blood flow, and the motion of tissue and organs such as heart and lungs.
1. A method for presenting information derived from a sample, the method including the steps of:
a. recording images from at least one projection angle and carrying out image analysis, encoding velocity data for the sample in terms of coordinates;
b. reconstructing a 2D or 3D velocity field directly from the image analysis; and
c. calculating the expansion of one or more regions in terms of velocity (u, v and w) against time opposite co-ordinates (x, y and z) and using derivatives defined by δu/δx+δv/δy+δw/δz for textual or graphical presentation.
2. A method according to claim 1 wherein the reconstruction of step b is performed by first reconstructing 2D or 3D images.
3. A method according to claim 1 or 2 which further includes the step of:
d. for one or more regions, using the expansion calculated in step c to calculate a parameter associated with motion.
4. A method according to claim 1 which further includes the step of:
e. segmenting an image of the sample.
5. A method according to claim 4 which further includes the step of:
f. associating each segment with regions of the 2D or 3D velocity field.
6. A system operative on the basis of presenting information derived from a sample, the system comprising an image capture means, a processor, and a user interface, wherein
a. the image capture means records images from at least one projection angle and the processor carries out image analysis, encoding velocity data for the sample in terms of coordinates;
b. the processor reconstructs a 2D or 3D velocity field directly from the image analysis; and
c. the processor calculates the expansion of one or more regions in terms of velocity (u, v and w) against time opposite co-ordinates (x, y and z) and using derivatives defined by δu/δx+δv/δy+δw/δz and is operative to present the calculated values as text or graphics.
7. A non-transitory computer readable storage medium for storing an application for executing a method of presenting information derived from a sample, the method including the steps of:
a. recording images from at least one projection angle and carrying out image analysis, encoding velocity data for the sample in terms of coordinates;
b. reconstructing a 2D or 3D velocity field directly from the image analysis; and
c. calculating the expansion of one or more regions in terms of velocity (u, v and w) against time opposite co-ordinates (x, y and z) and using derivatives defined by δu/δx+δv/δy+δw/δz for textual or graphical presentation.