1,721,126 research outputs found
Synchrotron Radiation for Biomedical Imaging
No full textA synchrotron radiation (SR) X-ray source is an extraordinary tool for many applications because of the high intensity, the energy spectrum properties, the peculiar laminar beam geometry and the high degree of coherence. In the past years several experimental studies have proven the suitability of SR in the field of biomedical X-ray imaging and in diagnostic radiography. SR based X-ray imaging techniques to be mentioned are transvenous coronary angiography, bronchography, computed tomography and mammography that have been successfully implemented at different SR laboratories all around the world. Moreover, the high degree of the coherence of the synchrotron source allows the implementation of novel phase-sensitive X-ray imaging modalities. In contrast to conventional X-ray radiography, based on different X-ray absorption properties of details within an object, these phase-based techniques are capable of visualizing structures that have different scattering and refraction properties respect to the surrounding material. Their importance in medical imaging lies in the fact that the diagnosis of several diseases requires the detection of tiny structures, that consist of light elements in a similar background, and that produce very low X-ray absorption, but considerable phase shift in the wave front propagation. Thus, phase-sensitive techniques may improve dramatically the image quality and subsequently the accuracy in diagnosis offering highly enhanced contrast with dose comparable or even lower than required by conventional radiography
Generalized diffraction enhanced imaging to retrieve absorption, refraction and scattering effects
No full textMicrobubbles as x-ray scattering contrast agents using analyzer-based imaging
No full textConventional contrast agents utilized in diagnostic radiology are based on x-ray absorption properties; alternative physical principles capable of providing a contrast enhancement in radiographs have never been applied. This study exploits the possibility of using a novel type of contrast media based on x-ray scattering. The contrast agents consist of microbubble echo-enhancing agents, usually applied in ultrasound examinations, which are invisible with conventional x-ray absorption techniques. The experiment was carried out at the medical beamline of the synchrotron radiation laboratory ELETTRA in Trieste, Italy. A flat silicon analyzer crystal typically used for diffraction-enhanced imaging was utilized as a tool for detecting the scattering properties of the contrast agents. In analyzer-based imaging, it is possible to detect the scattering properties of the sample by shifting the analyzer crystal to selected positions of its reflectivity curve. In particular, when the sample consists of a large number of micro-particles an overall effect can be observed. Phantoms containing contrast agents based on microbubbles were imaged at different angular positions of the analyzer crystal. High visibility of the details was demonstrated, and a strong contrast enhancement was measured compared to normal x-ray absorption techniques
Three-image diffraction enhanced imaging algorithm to extract absorption, refraction, and ultrasmall-angle scattering
No full textAs different methods to improve diffraction enhanced imaging are proposed, the authors introduce a simple algorithm that follows the original idea of Chapman et al. (Phys. Med. Biol. 42, 2015, 1997), but extend it to a general object featuring absorption, refraction, and ultrasmall-angle scattering. The information relative to the three effects is decoupled, requiring only three images in input. Simulation and experiment give accurate results, provided the refraction and scattering angles are small compared to the rocking curve width. The proposed algorithm can be readily and fruitfully implemented in several applications, particularly when time and dose constraints are relevant
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