MicroCT of Coronary Stents: Staining Techniques for 3-D Pathological Analysis

In the area of translational research, stent developers consult pathologists to obtain the best and most complete amount of data from implanted test devices in the most efficient manner. Through the use of micron-scale computed tomography along with post-fixation staining techniques in this study, full volumes of previously implanted stents have been analyzed in-situ in a non-destructive manner. The increased soft tissue contrast imparted by metal-containing stains allowed for a qualitative analysis of the vessel’s response to the implant with greater sensitivity and specificity while reducing beam-hardening artifact from stent struts. The developed staining techniques included iodine-potassium iodide, phosphomolybdic acid, and phosphotungstic acid, all of which bind to soft tissue and improve image quality through their ability to attenuate high energy X-rays. With these stains, the overall soft tissue contrast increased by up to 85 percent and contrast between medial and neointimal layers of the vessel increased by up to 22 percent. Beam hardening artifact was also reduced by up to 38 percent after staining. Acquiring data from the entirety of the stent and the surrounding tissue increased the quality of stent analysis in multiple ways. The three dimensional data enabled a comprehensive analysis of stent performance, lending information such as neointimal hyperplasia, percent stenosis, delineation of vessel wall layers, stent apposition, and stent fractures. By providing morphological data about stent deployment and host response, this method circumvents the need to make the more traditional histology slides for a morphometric analysis. These same data may also be applied to target regions of interest to ensure histology slides are cut from the optimal locations for a more in-depth analysis. The agents involved in such techniques are readily available in most pathology laboratories, are safe to work with, and allow for rapid processing of tissue. The ability to forego histology altogether or to highly focus what histology is performed on a vessel has the potential to hasten the development process of any coronary stent

MicroCT of Coronary Stents: Staining Techniques for 3-D Pathological Analysis

In the area of translational research, stent developers consult pathologists to obtain the best and most complete amount of data from implanted test devices in the most efficient manner. Through the use of micron-scale computed tomography along with post-fixation staining techniques in this study, full volumes of previously implanted stents have been analyzed in-situ in a non-destructive manner. The increased soft tissue contrast imparted by metal-containing stains allowed for a qualitative analysis of the vessel’s response to the implant with greater sensitivity and specificity while reducing beam-hardening artifact from stent struts. The developed staining techniques included iodine-potassium iodide, phosphomolybdic acid, and phosphotungstic acid, all of which bind to soft tissue and improve image quality through their ability to attenuate high energy X-rays. With these stains, the overall soft tissue contrast increased by up to 85 percent and contrast between medial and neointimal layers of the vessel increased by up to 22 percent. Beam hardening artifact was also reduced by up to 38 percent after staining. Acquiring data from the entirety of the stent and the surrounding tissue increased the quality of stent analysis in multiple ways. The three dimensional data enabled a comprehensive analysis of stent performance, lending information such as neointimal hyperplasia, percent stenosis, delineation of vessel wall layers, stent apposition, and stent fractures. By providing morphological data about stent deployment and host response, this method circumvents the need to make the more traditional histology slides for a morphometric analysis. These same data may also be applied to target regions of interest to ensure histology slides are cut from the optimal locations for a more in-depth analysis. The agents involved in such techniques are readily available in most pathology laboratories, are safe to work with, and allow for rapid processing of tissue. The ability to forego histology altogether or to highly focus what histology is performed on a vessel has the potential to hasten the development process of any coronary stent

Imaging Performance of Quantitative Transmission Ultrasound

Quantitative Transmission Ultrasound (QTUS) is a tomographic transmission ultrasound modality that is capable of generating 3D speed-of-sound maps of objects in the field of view. It performs this measurement by propagating a plane wave through the medium from a transmitter on one side of a water tank to a high resolution receiver on the opposite side. This information is then used via inverse scattering to compute a speed map. In addition, the presence of reflection transducers allows the creation of a high resolution, spatially compounded reflection map that is natively coregistered to the speed map. A prototype QTUS system was evaluated for measurement and geometric accuracy as well as for the ability to correctly determine speed of sound

Evolution of cuticular hydrocarbons in the hymenoptera : a meta-analysis

Chemical communication is the oldest form of communication, spreading across all organisms of life. In insects, cuticular hydrocarbons (CHC) function as the chemical recognition cues for the recognition of mates, species and nest-mates in social insects. Although much is known about the function of individual hydrocarbons and their biosynthesis, a phylogenetic overview is lacking. Here we review the CHC profiles of 241 species of hymenoptera, one of the largest and important insect orders, including the Symphyta (sawflies), the polyphyletic Parasitica (parasitoid wasps) and the Aculeata (wasps, bees and ants). We investigated whether these five major taxonomic groups differed in the presence and absence of CHC classes and whether the sociality of a species (solitarily vs. social) had an effect on CHC profile complexity. We found that the main CHC classes (i.e., n-alkanes, alkenes and methylalkanes) were all present early in the evolutionary history of the hymenoptera, as evidenced by their presence in ancient Symphyta and primitive Parasitica wasps. Throughout all groups within the Hymenoptera the more complex a CHC the fewer species that produce it, which may reflect the Occam's razor principle that insects’ only biosynthesize the most simple compound that fulfil its needs. Surprisingly there was no difference in the complexity of CHC profiles between social and solitary species, with some of the most complex CHC profiles belonging to the Parasitica. This profile complexity has been maintained in the ants, but some specialisation in biosynthetic pathways has led to a simplification of profiles in the aculeate wasps and bees. The absence of CHC classes in some taxa or species may be due to gene silencing or down-regulation rather than gene loss, as evidenced by sister species having highly divergent CHC profiles, and cannot be predicted by their phylogenetic history. The presence of highly complex CHC profiles prior to the vast radiation of the social hymenoptera indicates a 'spring-loaded' system where the diverse CHC needed for the complex communication systems of social insects, were already present for natural selection to act upon rather than evolve independently. This would greatly aid the multiple evolution of sociality in the Aculeata

Imaging Performance of Quantitative Transmission Ultrasound

Quantitative Transmission Ultrasound (QTUS) is a tomographic transmission ultrasound modality that is capable of generating 3D speed-of-sound maps of objects in the field of view. It performs this measurement by propagating a plane wave through the medium from a transmitter on one side of a water tank to a high resolution receiver on the opposite side. This information is then used via inverse scattering to compute a speed map. In addition, the presence of reflection transducers allows the creation of a high resolution, spatially compounded reflection map that is natively coregistered to the speed map. A prototype QTUS system was evaluated for measurement and geometric accuracy as well as for the ability to correctly determine speed of sound

Cold ion demagnetization near the X-line of magnetic reconnection

International audienceAlthough the effects of magnetic reconnection in magnetospheres can be observed at planetary scales, reconnection is initiated at electron scales in a plasma. Surrounding the electron diffusion region, there is an Ion-Decoupling Region (IDR) of the size of the ion length scales (inertial length and gyroradius). Reconnection at the Earth's magnetopause often includes cold magnetospheric (few tens of eV), hot magnetospheric (10 keV), and magnetosheath (1 keV) ions, with different gyroradius length scales. We report observations of a subregion inside the IDR of the size of the cold ion population gyroradius (15 km) where the cold ions are demagnetized and accelerated parallel to the Hall electric field. Outside the subregion, cold ions follow the E × B motion together with electrons, while hot ions are demagnetized. We observe a sharp cold ion density gradient separating the two regions, which we identify as the cold and hot IDRs