Iterative reconstruction method for spectral, phase-contrast imaging
A system and related method for X-ray phase contrast imaging. A signal model is fitted to interferometric measurment data. The fitting operation yields a Compton cross section and a photo-electric image. A pro-portionality between the Compton cross section and electron-density is used to achieve a reduction of the number of fitting variables. The Compton image may be taken, up to a constant, as a phase contrast images.
1. An imaging system, comprising:
an X-ray source for generating X-ray radiation waves;
an X-ray detector, including a plurality of detector pixels, for detecting the X-ray radiation waves after passing through a specimen and providing measurement data; and
a signal processing system for processing the measurement data, the signal processing system comprising:
an input port for receiving the measurement data;
a model initializer configured to include the measurement data into a signal model;
a model fitting module configured to perform, for the plurality of detector pixels, a fitting operation to fit parameters of the signal model to the measurement data, wherein the signal model includes parameters that represent attenuation of the X-ray radiation waves, wherein at least one of the parameters accounts for photo-electric effect absorption or Compton scattering, wherein the Compton scattering parameter is a surrogate for the electron density in the specimen, wherein the signal model includes a term that models, as a function of the Compton scattering, a modulation of a phase change induced by the specimen;
an output port configured to output at least some of the fitted parameters as a photo-electric absorption image or a Compton scattering image.
2. The imaging system of claim 1 , wherein the Compton scattering image provides information in relation to the electron density and/or a phase contrast image.
3. The imaging system of claim 1 , wherein said term includes a spatial derivative of the Compton scattering parameter.
4. The imaging system of claim 1 , including a reconstructor configured to reconstruct for a cross-sectional slice image based on at least some of the fitted parameters.
5. The imaging system of claim 1 , wherein the fitting operation includes approximating the spatial derivative through differences of the fitted Compton parameter for neighboring detector pixel readings.
6. The imaging system of claim 1 , wherein the fitting operation includes analytically forming the derivate based on derivatives of basis functions associated with respective voxels.
7. The imaging system of claim 1 , wherein the measurement data is acquired along a single projection direction or is acquired from a plurality of projection directions.
8. The imaging system of claim 1 , wherein the X-ray detector is of the energy integrating type.
9. The imaging system of claim 1 , wherein the imaging system is a 2D projection imager or a computed tomography scanner.
10. A method for imaging a specimen, comprising:
generating X-ray radiation waves by an X-ray source;
detecting the X-ray radiation waves after passing through the specimen and providing measurement data by an X-ray detector that includes a plurality of detector pixels; and
processing the measurement data by a signal processing system, the processing comprising:
receiving the measurement data;
including the measurement data into a signal model;
for the plurality of detector pixels, fitting parameters of the signal model to the measurement data, wherein the signal model includes parameters that represent attenuation of the X-ray beam, wherein one of the parameters accounts for photo-electric absorption or Compton scattering, wherein the Compton scattering parameter is a surrogate for the electron density in the specimen, wherein the signal model includes a term that models, as a function of the Compton scattering, a modulation of a phase change induced by the object;
outputting at least some of the fitted parameters as a photo-electric absorption image or a Compton scattering image.
11. The method of claim 10 , comprising:
reconstructing for a cross-sectional slice image based on at least one or more of the fitted parameters.
12. The method of claim 10 , wherein the Compton scattering image is indicative of an image of the electron density and/or of a phase contrast image.
13. A non-transitory computer-readable medium having one or more executable instructions stored thereon, which when executed by a processor, cause the processor to perform a method for imaging a specimen, the method comprising:
generating X-ray radiation waves by an X-ray source;
detecting the X-ray radiation waves after passing through the specimen and providing measurement data by an X-ray detector that includes a plurality of detector pixels; and
processing the measurement data by a signal processing system, the processing comprising:
receiving the measurement data;
including the measurement data into a signal model;
for the plurality of detector pixels, fitting parameters of the signal model to the measurement data, wherein the signal model includes parameters that represent attenuation of the X-ray beam, wherein one of the parameters accounts for photo-electric absorption or Compton scattering, wherein the Compton scattering parameter is a surrogate for the electron density in the specimen, wherein the signal model includes a term that models, as a function of the Compton scattering, a modulation of a phase change induced by the object;
outputting at least some of the fitted parameters as a photo-electric absorption image or a Compton scattering image.