Revising the lower statistical limit of x-ray grating-based phase-contrast computed tomography.

Phase-contrast x-ray computed tomography (PCCT) is currently investigated as an interesting extension of conventional CT, providing high soft-tissue contrast even if examining weakly absorbing specimen. Until now, the potential for dose reduction was thought to be limited compared to attenuation CT, since meaningful phase retrieval fails for scans with very low photon counts when using the conventional phase retrieval method via phase stepping. In this work, we examine the statistical behaviour of the reverse projection method, an alternative phase retrieval approach and compare the results to the conventional phase retrieval technique.

Improved Diagnostics by Assessing the Micromorphology of Breast Calcifications via X-Ray Dark-Field Radiography.

Breast microcalcifications play an essential role in the detection and evaluation of early breast cancer in clinical diagnostics. However, in digital mammography, microcalcifications are merely graded with respect to their global appearance within the mammogram, while their interior microstructure remains spatially unresolved and therefore not considered in cancer risk stratification. In this article, we exploit the sub-pixel resolution sensitivity of X-ray dark-field contrast for clinical microcalcification assessment.

Improved visualization of breast cancer features in multifocal carcinoma using phase-contrast and dark-field mammography: an ex vivo study.

Objectives: Conventional X-ray attenuation-based contrast is inherently low for the soft-tissue components of the female breast. To overcome this limitation, we investigate the diagnostic merits arising from dark-field mammography by means of certain tumour structures enclosed within freshly dissected mastectomy samples.

Methods: We performed grating-based absorption, absolute phase and dark-field mammography of three freshly dissected mastectomy samples containing bi- and multifocal carcinoma using a compact, laboratory Talbot-Lau interferometer.

Non-invasive differentiation of kidney stone types using X-ray dark-field radiography.

Treatment of renal calculi is highly dependent on the chemical composition of the stone in question, which is difficult to determine using standard imaging techniques. The objective of this study is to evaluate the potential of scatter-sensitive X-ray dark-field radiography to differentiate between the most common types of kidney stones in clinical practice. Here, we examine the absorption-to-scattering ratio of 118 extracted kidney stones with a laboratory Talbot-Lau Interferometer.

Regularized iterative integration combined with non-linear diffusion filtering for phase-contrast x-ray computed tomography.

Phase-contrast x-ray computed tomography has a high potential to become clinically implemented because of its complementarity to conventional absorption-contrast.In this study, we investigate noise-reducing but resolution-preserving analytical reconstruction methods to improve differential phase-contrast imaging. We apply the non-linear Perona-Malik filter on phase-contrast data prior or post filtered backprojected reconstruction.

Energy-resolved visibility analysis of grating interferometers operated at polychromatic X-ray sources.

Grating interferometry has been successfully adapted at standard X-ray tubes and is a promising candidate for a broad use of phase-contrast imaging in medical diagnostics or industrial testing. The achievable image quality using this technique is mainly dependent on the interferometer performance with the interferometric visibility as crucial parameter. The presented study deals with experimental investigations of the spectral dependence of the visibility in order to understand the interaction between the single contributing energies.

Quantitative electron density characterization of soft tissue substitute plastic materials using grating-based x-ray phase-contrast imaging.

Many scientific research areas rely on accurate electron density characterization of various materials. For instance in X-ray optics and radiation therapy, there is a need for a fast and reliable technique to quantitatively characterize samples for electron density. We present how a precise measurement of electron density can be performed using an X-ray phase-contrast grating interferometer in a radiographic mode of a homogenous sample in a controlled geometry.

Fast one-dimensional wave-front propagation for x-ray differential phase-contrast imaging.

Numerical wave-optical simulations of X-ray differential phase-contrast imaging using grating interferometry require the oversampling of gratings and object structures in the range of few micrometers. Consequently, fields of view of few millimeters already use large amounts of a computer's main memory to store the propagating wave front, limiting the scope of the investigations to only small-scale problems. In this study, we apply an approximation to the Fresnel-Kirchhoff diffraction theory to overcome these restrictions by dividing the two-dimensional wave front up into 1D lines, which are processed separately.

Bi-directional x-ray phase-contrast mammography.

Phase-contrast x-ray imaging is a promising improvement of conventional absorption-based mammography for early tumor detection. This potential has been demonstrated recently, utilizing structured gratings to obtain differential phase and dark-field scattering images. However, the inherently anisotropic imaging sensitivity of the proposed mono-directional approach yields only insufficient diagnostic information, and has low diagnostic sensitivity to highly oriented structures.

Visualizing typical features of breast fibroadenomas using phase-contrast CT: an ex-vivo study.

Background: Fibroadenoma is the most common benign solid breast lesion type and a very common cause for histologic assessment. To justify a conservative therapy, a highly specific discrimination between fibroadenomas and other breast lesions is crucial. Phase-contrast imaging offers improved soft-tissue contrast and differentiability of fine structures combined with the potential of 3-dimensional imaging.

Quantitative breast tissue characterization using grating-based x-ray phase-contrast imaging.

X-ray phase-contrast imaging has received growing interest in recent years due to its high capability in visualizing soft tissue. Breast imaging became the focus of particular attention as it is considered the most promising candidate for a first clinical application of this contrast modality. In this study, we investigate quantitative breast tissue characterization using grating-based phase-contrast computed tomography (CT) at conventional polychromatic x-ray sources.

Grating-based X-ray phase contrast for biomedical imaging applications.

In this review article we describe the development of grating-based X-ray phase-contrast imaging, with particular emphasis on potential biomedical applications of the technology. We review the basics of image formation in grating-based phase-contrast and dark-field radiography and present some exemplary multimodal radiography results obtained with laboratory X-ray sources. Furthermore, we discuss the theoretical concepts to extend grating-based multimodal radiography to quantitative transmission, phase-contrast, and dark-field scattering computed tomography.

Beam hardening effects in grating-based x-ray phase-contrast imaging.

Purpose: In this work, the authors investigate how beam hardening affects the image formation in x-ray phase-contrast imaging and consecutively develop a correction algorithm based on the results of the analysis.

Methods: The authors' approach utilizes a recently developed x-ray imaging technique using a grating interferometer capable of visualizing the differential phase shift of a wave front traversing an object. An analytical description of beam hardening is given, highlighting differences between attenuation and phase-contrast imaging.

[Acute leukemia in children with Down syndrome: analysis of cases].

An analysis of clinical and laboratory parameters and the results of treatment of 14 children with Down Syndrome and acute leukaemia was performed. The children were treated between 1986-1997. Their age ranged from 1 day to 13 years (average 5.

[Thrombus of the right ventricle simulating a cardiac tumor--case report].

A nine day infant with Down syndrome and congenital heart disease is presented in whom the course of neonatal sepsis was complicated by the presence of difficult to diagnose pathological masses in the right ventricle. The etiology of pathological masses was difficult to establish in survival investigations. Histopathological examinations revealed the presence of thrombus in the right heart and foci of granulation on a muscle of right ventricle outflow, probably after a septic embolus.

[The clinical course of fungal urinary tract infection in neonates].

The authors present the clinical course of 8 cases of fungal infection of the urinary tract in newborns. Three of the investigated children were premature or with intrauterine hypotrophy, a congenital defect of the urinary tract was detected in one child. In 5 cases the fungal infection followed bacterial septicaemia.

Cellular and humoral components of neutrophil chemotaxis in neonates with bacterial infection.

The initial stage of infection is characterized by both, changes in leucocyte function and humoral factors activity. In this paper we evaluated random migration and chemotaxis of neutrophils and serum ability to generate humoral factors influencing the neutrophil function. The studies were performed in 51 neonates during the acute phase of bacterial infection and in the remission time.

[Aspergillosis of the lymphatic nodes].

The authors emphasize fungal lesions to the lymphatic nodes confirmed by the presence of Aspergillus flavus in blood and throat smear cultures (on Sabouraud's medium) and presence of A. flavus in cytological examination of biopsy from the lymphatic node, increased number of eosinophils in peripheral blood, and infiltration of eosinophils in bone marrow and lymphatic nodes. Aspergillosis coexisted with the infection with Candida albicans and S.