Determining the photon interaction parameters of iodine compounds as contrast agents for use in radiology

Effect of Spatial Heterogeneity on the Unusual Uptake Behavior of Multivariate-Metal-Organic Frameworks

The uniqueness of multivariate metal-organic frameworks (MTV-MOFs) has been widely explored to discover their unknown opportunities. While mesoscopic apportionments have been studied, macroscopic heterogeneity and its spatial effects remain unexplored in MTV-MOFs. In this study, we investigated the effect of macroscopic heterogeneity on MTV-MOFs on their uptake behaviors by comparing three types of MTV-MOFs having the functional groups in inner, outer, or entire parts of crystals. Their adsorption behavior for carbon dioxide (CO₂) and water (H₂O) brought out that functional groups located in the outer part of the crystals dominantly influence the sorption behavior of MTV-MOFs. These results are also visualized by observing iodine adsorption in the three types of MTV-MOFs using scanning transmission electron microscopy-electron energy loss spectroscopy. We believe that this finding provides new ways to decipher and design MTV-MOFs for their unusual properties.

Photon interaction performance of various contrast agents: Theoretical and simulation results

In this study, total mass attenuation coefficient (μ/ρ) values in the energy range from 60 keV to 15 MeV for some contrast agents (Iopamidol, Metrizamide, Iohexol, Ioxaglic acid, Iopromide, Ioversol and Iopentol) were determined with the WinXCOM computer program and GEANT4 computer simulation code. Linear attenuation coefficients (μ), half value layers (HVL), tenth value layers (TVL), mean free paths (mfp), effective atomic numbers (Z_Eff) and effective electron densities (N_Eff) in the aforementioned energy range were obtained with the help of the calculated total mass attenuation coefficients. Energy absorption build-up factors (EABF) and exposure build-up factors (EBF) for contrast agents were calculated using the five-parameter geometric progression (G-P) fitting method in the energy region of 0.015 MeV ≤ E ≤ 15 MeV for different penetration depths up to 40 mfp with the help of the equivalent atomic numbers (Z_eqv). Kerma relative to air values were investigated in the energy region 0.001 MeV ≤ E ≤ 20 MeV. It has been observed that Ioxaglic acid is a good radiation absorber according to the other studied contrast agents. The present results may contribute to various application areas of radiation research.

Virtual Monoenergetic CT Imaging via Deep Learning

Conventional single-spectrum computed tomography (CT) reconstructs a spectrally integrated attenuation image and reveals tissues morphology without any information about the elemental composition of the tissues. Dual-energy CT (DECT) acquires two spectrally distinct datasets and reconstructs energy-selective (virtual monoenergetic [VM]) and material-selective (material decomposition) images. However, DECT increases system complexity and radiation dose compared with single-spectrum CT. In this paper, a deep learning approach is presented to produce VM images from single-spectrum CT images. Specifically, a modified residual neural network (ResNet) model is developed to map single-spectrum CT images to VM images at pre-specified energy levels. This network is trained on clinical DECT data and shows excellent convergence behavior and image accuracy compared with VM images produced by DECT. The trained model produces high-quality approximations of VM images with a relative error of less than 2%. This method enables multi-material decomposition into three tissue classes, with accuracy comparable with DECT.