High-resolution, low-dose phase contrast X-ray tomography for 3D diagnosis of human breast cancers.

Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ~10-20% of palpable tumors are not detectable on mammograms and only about 40% of biopsied lesions are malignant. Here we report a high-resolution, low-dose phase contrast X-ray tomographic method for 3D diagnosis of human breast cancers. By combining phase contrast X-ray imaging with an image reconstruction method known as equally sloped tomography, we imaged a human breast in three dimensions and identified a malignant cancer with a pixel size of 92 µm and a radiation dose less than that of dual-view mammography. According to a blind evaluation by five independent radiologists, our method can reduce the radiation dose and acquisition time by ~74% relative to conventional phase contrast X-ray tomography, while maintaining high image resolution and image contrast. These results demonstrate that high-resolution 3D diagnostic imaging of human breast cancers can, in principle, be performed at clinical compatible doses.

Imaging of the angular-dependent coherent-scatter cross section with analyzer crystal: a Monte Carlo simulation.

A nontomography approach for the measurement of angular-dependent coherent-scatter cross section of x rays (E≃40-80 keV) is described. It is shown that an analyzer crystal, which is proposed to be used for the sampling of the cross section, simultaneously provides information about the location of the scattering volume inside the object. A numerical simulation demonstrates that this method can be applied for nondestructive analysis of an object's internal structure.

Absorption, refraction and scattering in analyzer-based imaging: comparison of different algorithms.

Many mathematical methods have been so far proposed in order to separate absorption, refraction and ultra-small angle scattering information in phase-contrast analyzer-based images. These algorithms all combine a given number of images acquired at different positions of the crystal analyzer along its rocking curve. In this paper a comprehensive quantitative comparison between five of the most widely used phase extraction algorithms based on the geometrical optics approximation is presented: the diffraction-enhanced imaging (DEI), the extended diffraction-enhanced imaging (E-DEI), the generalized diffraction-enhanced (G-DEI), the multiple-image radiography (MIR) and the Gaussian curve fitting (GCF). The algorithms are theoretically analyzed in terms of their validity conditions and experimentally compared by using geometrical phantoms providing various amounts of absorption, refraction and scattering. The presented work shows that, due to their specific validity conditions, the considered algorithms produce results that may greatly differ, especially in the case of highly refracting and/or highly scattering materials. The various extraction algorithms are also applied to images of a human bone-cartilage sample. The aim is to validate the results obtained on geometrical phantoms and prove the efficiency of the different algorithms for applications on biological samples.

On the relative performance of edge illumination x-ray phase-contrast CT and conventional, attenuation-based CT.

PURPOSE: This article is aimed at comparing edge illumination (EI) x-ray phase contrast computed tomography (PCT) and conventional (attenuation-based) computed tomography (CT), based on their respective contrast and noise transfer. METHODS: The noise in raw projections obtained with EI PCT is propagated through every step of the data processing, including phase retrieval and tomographic reconstruction, leading to a description of the noise in the reconstructed phase tomograms. This is compared to the noise in corresponding attenuation tomograms obtained with CT. Specifically, a formula is derived that allows evaluating the relative performance of both modalities on the basis of their contrast-to-noise ratio (CNR), for a variety of experimental parameters. RESULTS: The noise power spectra of phase tomograms are shifted towards lower spatial frequencies, leading to a fundamentally different noise texture. The relative performance of EI PCT and CT, in terms of their CNR, is linked to spatial resolution: the CNR in phase tomograms is generally superior to that in attenuation tomograms for higher spatial resolutions (tens to hundreds of µm), but inferior for lower spatial resolutions (hundreds of µm to mm). CONCLUSION: These results imply that EI PCT could outperform CT in applications for which high spatial resolutions are key, e.g., small animal or specimen imaging.