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X-Ray Computed Tomography and Nanomaterials as Contrast Agents for Tumor Diagnosis
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
R. G. Aswathy, D. Sakthi Kumar
Yb-based nanoparticulate CT contrast agents have been developed [55] and owing to the attenuation characteristics of Yb-based NPs, they offer higher contrast than clinical iodinated contrast agents. They tend to be efficient than presently employing Au-, Bi-, Pt-, and Ta-based NP-based CT contrast agents operating at 120 kilo voltage peak (kVp). The perfection is chiefly credited to Yb’s K-edge energy that is within the higher energy section of X-ray spectrum. The K-edge energy of an element is the rapid enhancement in the attenuation coefficient of photons at energy beyond the binding energy of K-shell electron of atoms within the X-ray beam. When encapsulated in a PEG shell, the NPs showed enhanced biocompatibility and prolonged circulation time in vivo [56]. These NPs exhibited high performance in in vivo angiography and image guided lymph node mapping. Furthermore, NIR-to-visible (NIR-to-Vis) or NIR- to-NIR UCL property of the Yb-NPs was used for deep tissue imaging and preventing the tissue damage related with UV excitation [57]. Doping of Er3+ and Gd3+ in these NPs imparted them with MRI capability [58,59].
Basics of x-ray tubes
Published in Gavin Poludniowski, Artur Omar, Pedro Andreo, Calculating X-ray Tube Spectra, 2022
Gavin Poludniowski, Artur Omar, Pedro Andreo
In addition, extra filtration, often aluminium or copper, may be added to modify the beam. The purpose is to remove low-energy x rays too soft to be useful and to tune the penetrative capabilities of the beam to the particular task. Such filtration is referred to as added filtration. Most commonly this is used to harden the beam, with lower energy x rays being preferentially removed. This is not always the case, however, as the K-edge of some materials may be taken of advantage for the increased suppression of x rays of energy above the K-edge. In such a situation, the material acts more as a band-pass filter.
Photon Interactions with Matter
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
The photoelectric interaction probability depends sensitively on the material type. Figure 5.1.4 shows the mass absorption coefficient for interactions of the photons with muscle (red). For lead, the plot looks quite different. First, overall the mass absorption coefficient is much larger for lead than muscle. This is because of the higher atomic number of lead (Z = 82) vs. muscle. Note that the mass absorption coefficient scales as approximately Z3. Also notable in the curve for lead is the presence of various “edges,” i.e. discontinuities where the mass absorption coefficient suddenly changes. These are due to the various principle quantum numbers of electrons in the atom (n = 1, 2, 3…) which in X-ray spectroscopy are labeled as K (the highest binding energy), L, M, and so on. To understand this, consider the K edge. If an incident photon has an energy less than the K edge energy it will not be able to ionize an electron in the K shell. However, as soon as the energy of the photon exceeds this threshold the electron can be liberated. The mass absorption coefficient, therefore, suddenly increases since more photons can be absorbed. This accounts for the sudden discontinuities in the mass absorption coefficient. Aside from the shell transitions the mass absorption coefficient for lead also decreases like 1/E3. Note that there are no K or L shells visible on the curves for muscle because it is composed mostly of carbon, oxygen, and hydrogen which are low-Z materials and have binding energies which are very small.
Pterostilbene fluorescent probes as potential tools for targeting neurodegeneration in biological applications
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Lidia Ciccone, Susanna Nencetti, Maria Marino, Chiara Battocchio, Giovanna Iucci, Iole Venditti, Martina Marsotto, Emiliano Montalesi, Simone Socci, Beatrice Bargagna, Elisabetta Orlandini
Near-edge X-ray absorption fine structure (NEXAFS) spectra were acquired at the BEAR beamline (bending magnet for emission absorption and reflectivity) at the ELETTRA storage ring. BEAR is installed at the left exit of the 8.1 bending magnet exit. The apparatus is based on a bending magnet as a source and beamline optics delivering photons from 5 eV up to about 1600 eV with selectable degree of ellipticity. The UHV end station is equipped with a movable hemispherical electron analyser and a set of photodiodes to collect angle-resolved photoemission spectra, optical reflectivity, and fluorescence yield. In these experiments, we used ammeters to measure drain current from the sample. C, N, and O K-edge spectra were collected at grazing (20°) incidence angles of the linearly polarised photon beam with respect to the sample surface. In addition, our carbon, nitrogen and oxygen K-edge spectra have been further calibrated using the resonance at 285.00 eV, assigned to the C = C aromatic 1 s − π* transition, the resonance at 401.00 eV, assigned to the 1 s − π* transition of the Car-N bond and the resonance at 531.5 eV, assigned to the C = O carbonyl 1 s − π* transition, respectively. The raw C, N, and O K-edge NEXAFS spectra were normalised to the incident photon flux by dividing the sample spectrum by the spectrum collected on a freshly sputtered gold surface. Spectra were then normalised subtracting a straight line that fits the part of the spectrum below the edge and assessing to 1 the value at 330.00, 430.00, and 560.00 eV for carbon, nitrogen, and oxygen, respectively.
Scanning transmission X-ray microscopy study of subcellular granules in human platelets at the carbon K- and calcium L2,3-edges
Published in Platelets, 2022
Jeonghee Shin, Sehee Park, Tung X. Trinh, Sook Jin Kwon, Jiwon Bae, Hangil Lee, Eugenia Valsami-Jones, Jian Wang, Jaewoo Song, Tae Hyun Yoon
STXM observations of the same platelets were performed at the carbon K-edge and their carbon distribution maps were obtained through a similar image analysis process (Figure 2 (a2, 2a2′, 2b2, and 2c2)) as used for the calcium L-edge. The carbon K-edge XANES spectra of the six DGs (a2, a3, b1, b2, c1, and c2) as well as the cytoplasm region (a1) are presented in Figure 2d. Different energy positions of the carbon K-edge XANES spectra were denoted as a*–g* and assigned as aromatic-olefinic, ketone-phenol-nitrile-imine, aliphatic, amide carbonyl, carboxylic acid, alcohol-ether-hydroxylated aliphatic, and carbonate functional groups, respectively, based on a recent studies on carbon K-edge XANES spectra references [23–25,33,34] (see Table II), which are later used to investigate the biological components of the platelet DGs and cytoplasm using the deconvolution code of Le Guillou and colleagues[33]. Firstly, we have conducted PCA on the human platelet carbon and calcium STXM image stack (shown in Figure 3a) and the analysis results are presented in Figure 3. The PCA of the STXM stack resulted in 10 components, as shown in Figure 3 b, 3C and 3D.
Monte Carlo-based calculation of nano-scale dose enhancement factor and relative biological effectiveness in using different nanoparticles as a radiosensitizer
Published in International Journal of Radiation Biology, 2021
Mostafa Robatjazi, Hamid Reza Baghani, Atefeh Rostami, Ali Pashazadeh
A significant increase in the DEF value was observed at the distance range of 300–700 nm for all NPs irradiated by 30 keV photon energy. This result is because of the very short range of produced secondary electrons which is limited to very close distances around the considered NPs. Also, a sharp fall-off in DEF value was seen after this range for the majority of the NPs when irradiated by 30 keV photon energy. At this energy, the maximum DEF value belongs to the AgNP. This observation can be well described by the secondary electrons produced by the K-edge. Beyond the 600-nm distance from the NPs surface, the maximum DEF was reported for the PtNP and AuNP for this energy. These NPs show great DEF values without a significant fall-off in the considered range when irradiated by 30 keV photons.