Measurement and simulation of phase effects in radiological images of weakly-absorbing cylindrical objects
M. Brandan 1*, K. Palma-Alejandro 1
1 Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico
We have performed a systematic study of phase effects in images acquired with microfocus X-ray tubes, analyzing the phase contrast observed at the edges of cylindrical objects. Digital images (48 µm pixel size) of nylon fibers were acquired with X-ray tubes (35 µm nominal focal spot) operated with a variety of anode/filter and voltage combinations. Geometrical conditions were source-to-detector distances up to 1 m and magnifications up to 4. The measured quantity was the fiber edge enhancement relative to background. Maximum edge enhancement, about 1.8 %, was observed for magnification 3 and a quasi-monoenergetic beam, about 15 keV effective energy.
Simulation tools were developed in MATLAB to preprocess the digital images, obtain intensity profiles using oversampling, and simulate intensity profiles of the cylindrical objects. A first tool corrects and preprocesses the images for further analysis. The second, quantifies phase effects using data oversampling techniques. The third program is a theoretical formalism of diffraction through the simulation of the radiation intensity produced by weakly absorbing cylindrical objects at the detector plane. Simulations show an excellent qualitative agreement with the experimental results.