Phase contrast x-ray imaging is a powerful technique for the detection of low-contrast details in weakly absorbing objects. This method is of possible relevance in the field of diagnostic radiology. In fact, imaging low-contrast details within soft tissue does not give satisfactory results in conventional x-ray absorption radiology, mammography being a typical example. Nevertheless, up to now all applications of the phase contrast technique, carried out on thin samples, have required radiation doses substantially higher than those delivered in conventional radiological examinations. To demonstrate the applicability of the method to mammography we produced phase contrast images of objects a few centimetres thick while delivering radiation doses lower than or comparable to doses needed in standard mammographic examinations (typically approximately 1 mGy mean glandular dose (MGD)). We show images of a custom mammographic phantom and of two specimens of human breast tissue obtained at the SYRMEP bending magnet beamline at Elettra, the Trieste synchrotron radiation facility. The introduction of an intensifier screen enabled us to obtain phase contrast images of these thick samples with radiation doses comparable to those used in mammography. Low absorbing details such as 50 microm thick nylon wires or thin calcium deposits (approximately 50 microm) within breast tissue, invisible with conventional techniques, are detected by means of the proposed method. We also find that the use of a bending magnet radiation source relaxes the previously reported requirements on source size for phase contrast imaging. Finally, the consistency of the results has been checked by theoretical simulations carried out for the purposes of this experiment.

The transformation of amorphous colloidal calcium carbonate into single microcrystals was observed in supersaturated solutions in situ. The observations are done by simultaneous time-resolved small-angle and wide-angle X-ray scattering experiments (TR-SAXS/WAXS) at a third generation synchrotron source. TR-SAXS/WAXS demonstrates that the particles generated by reaction of Ca 2+ and CO 3 2-ions are amorphous. The transformation of these amorphous CaCO 3 particles proceeds via dissolution and subsequent heterogeneous nucleation of the crystalline modification on the walls of the quartz capillary containing the reacting mixture. The crystalline modifications thus generated could be identified. No solid-solid transition is observed. TR-SAXS/WAXS is therefore well-suited to follow the mineralization from aqueous solution in great detail.The formation of calcium carbonate from supersaturated solutions has been studied for more than a century and it has received renewed interest, especially in the field of biomineralization. 1 The metastable forms of calcium carbonate can be investigated more precisely nowadays thanks to the improvement of the experimental techniques. 2 In particular amorphous calcium carbonate (ACC) has emerged as a precursor to the formation of more stable crystalline forms. 3 A topic of intense research activity is presently the detailed mechanism of phase transformation leading from the initial amorphous material to the final, thermodynamically stable, crystalline modification (calcite). Different mechanisms are being discussed, as, e.g., a solid/solid phase transition and a dissolution/crystallization process. This process also depends strongly on reagent concentrations and reaction conditions. 4 The transition from the amorphous state into a stable, crystalline modification is difficult to be studied in a timeresolved experiment. A number of experimental techniques have been applied to the study of the calcium carbonate formation, including optical, electron, and X-ray microscopies, dynamic light scattering, turbidimetry, and conductivity methods. 2,5 These methods, however, do not give the structural information as a function of time. On the other hand, the application of X-ray scattering methods is particularly well suited because it allows in-situ measurements of the size, morphology, and interactions of colloidal particles growing in solution. 6,7 Hence, scattering experiments probing directly the crystal structure of a given population of particles would be helpful to investigate the mineralization leading to a stable crystalline form.Recently, we studied the nucleation and growth of colloidal spheres made of calcium carbonate (CaCO 3 ) by using timeresolved small-angle X-ray scattering (TR-SAXS). 6 This method allows us to follow the growth of the particles from ∼20 ms after mixing the reagent solutions to their final size with a time resolution down to ∼0.1 s. In particular, we showed that the evolving particles consist of amorphous calcium carbonate. This could be deduced from the low m...

The authors evaluated the effect on mammographic examinations of the use of synchrotron radiation to detect phase-perturbation effects, which are higher than absorption effects for soft tissue in the energy range of 15-25 keV. Detection of phase-perturbation effects was possible because of the high degree of coherence of synchrotron radiation sources. Synchrotron radiation images were obtained of a mammographic phantom and in vitro breast tissue specimens and compared with conventional mammographic studies. On the basis of grades assigned by three reviewers, image quality of the former was considerably higher, and the delivered dose was fully compatible.

The density deficit of water at hydrophobic interfaces, frequently called the hydrophobic gap, has been the subject of numerous experimental and theoretical studies in the past decade. Recent experiments give values for the interfacial depletion that consistently correspond to less than a monolayer of water. The main question which remained so far unanswered is its origin and the mechanisms affected by the chemistry and molecular geometry of a particular hydrophobic coating. In this work, we present a combined high-energy X-ray reflectivity and molecular dynamics simulation study of the water depletion at a perfluorinated hydrophobic interface with a spatial resolution on the molecular scale. A comparison of our experimental and computational results elucidates the underlying mechanisms that affect the extent of the interfacial depletion. The complex interplay between surface chemistry and topography precludes the existence of a direct and universal relation between the macroscopic contact angle and the nanoscopic water depletion.