No abstract

An artificial intelligence algorithm differentiated between COVID-19 pneumonia and non-COVID-19 pneumonia in chest x-ray radiographs with high sensitivity and specificity.

Absorption, refraction, and SAS CT imaging can be achieved using the Talbot-Lau interferometer without the additional overhead of long scan time and phase stepping.

It remains crucial to develop a laboratory model for studying hepatitis B virus (HBV) chronic infection. We hereby produced a recombinant covalently closed circular DNA (rcccDNA) in view of the key role of cccDNA in HBV persistence. A loxP-chimeric intron was engineered into a monomeric HBV genome in a precursor plasmid (prcccDNA), which was excised using Cre/loxPmediated DNA recombination into a 3.3-kb rcccDNA in the nuclei of hepatocytes. The chimeric intron was spliced from RNA transcripts without interrupting the HBV life cycle. In cultured hepatoma cells, cotransfection of prcccDNA and pCMV-Cre (encoding Cre recombinase) resulted in accumulation of nuclear rcccDNA that was heat stable and epigenetically organized as a minichromosome. A mouse model of HBV infection was developed by hydrodynamic injection of prcccDNA. In the presence of Cre recombinase, rcccDNA was induced in the mouse liver with effective viral replication and expression, triggering a compromised T-cell response against HBV. Significant T-cell hyporesponsiveness occurred in mice receiving 4 g prcccDNA, resulting in prolonged HBV antigenemia for up to 9 weeks. Persistent liver injury was observed as elevated alanine transaminase activity in serum and sustained inflammatory infiltration in the liver. Although a T-cell dysfunction was induced similarly, mice injected with a plasmid containing a linear HBV replicon showed rapid viral clearance within 2 weeks. Collectively, our study provides an innovative approach for producing a cccDNA surrogate that established HBV persistence in immunocompetent mice. It also represents a useful model system in vitro and in vivo for evaluating antiviral treatments against HBV cccDNA. (cccDNA) is an essential component of the HBV replication cycle and is regarded as a primary molecular mechanism for HBV persistence. The amount of cccDNA in cells is low, with around 5 to 50 copies in the nucleus. Nevertheless, cccDNA is stable, with a loss rate that correlates with the mitosis or death of infected hepatocytes (1, 2). Current antiviral treatments fail to eliminate the preexisting cccDNA pool that is responsible for viral rebound after therapy cessation. On the other hand, there is still lack of convenient techniques with high sensitivity and specificity to measure the HBV cccDNA pool in the hepatocyte nucleus (3)(4)(5).A laboratory animal model will be crucial for studying chronic HBV infection and disease. Mice are not susceptible to HBV infection because they lack a receptor(s) for viral entry. Even in HBV transgenic (Tg) mice, cccDNA is not formed, for unknown reasons (6, 7). These barriers can be experimentally overcome by hydrodynamic injection of naked plasmid DNA encoding an overlength HBV replicon, which enables intracellular replication of HBV in murine hepatocytes (8)(9)(10)(11)(12). However, the HBV replicon-based hydrodynamic injection induces only transient HBV viremia resembling an acute infection in immunocompetent mice. In this regard, a recent model of HBV persistence generated by inject...

Purpose:The superior radiation dose efficiency of a newly implemented differential phase contrast CT imaging method compared to the conventional absorption CT method is demonstrated. Methods: A differential phase contrast CT imaging method has recently been implemented using conventional x-ray sources with a grating interferometer consisting of three gratings. This approach offers the possibility of simultaneous reconstruction of both attenuation contrast and phase contrast images from a single acquisition. This enables a direct comparison of radiation dose efficiency of both types of reconstructed images under identical conditions. Radiation dose efficiency was studied by measuring the change in contrast-to-noise ratio ͑CNR͒ with different exposure levels. A physical phantom of 28.5 mm diameter was constructed and used for measurement of CNR in both the absorption and phase contrast CT images, which were reconstructed from the same data set. Results: For three of the four materials studied, at any given exposure level, the CNR of the differential phase contrast CT images was superior to that of the corresponding absorption contrast CT images. The most dramatic improvement was noted in the contrast between PMMA and water, where the CNR was improved by a factor of approximately 5.5 in the differential phase contrast CT images. Additionally, the CNR of phase contrast CT is empirically shown to have the same square root dependence on exposure, as is the case for absorption contrast CT. Conclusions: The differential phase contrast CT method provided higher CNR than conventional absorption CT at equivalent dose levels for most of the materials studied, and so may enable achievement of the same object visibility as conventional absorption CT methods at a lower exposure level.

Time-resolved cardiac imaging is particularly interesting in the interventional setting since it would provide both image guidance for accurate procedural planning and cardiac functional evaluations directly in the operating room. Imaging the heart in vivo using a slowly rotating C-arm system is extremely challenging due to the limitations of the data acquisition system and the high temporal resolution required to avoid motion artifacts. In this paper, a data acquisition scheme and an image reconstruction method are proposed to achieve time-resolved cardiac cone-beam computed tomography imaging with isotropic spatial resolution and high temporal resolution using a slowly rotating C-arm system. The data are acquired within 14 s using a single gantry rotation with a short scan angular range. The enabling image reconstruction method is the prior image constrained compressed sensing (PICCS) algorithm. The prior image is reconstructed from data acquired over all cardiac phases. Each cardiac phase is then reconstructed from the retrospectively gated cardiac data using the PICCS algorithm. To validate the method, several studies were performed. Both numerical simulations using a hybrid motion phantom with static background anatomy as well as physical phantom studies have been used to demonstrate that the proposed method enables accurate reconstruction of image objects with a high isotropic spatial resolution. A canine animal model scanned in vivo was used to further validate the method.

Purpose:The noise variance versus spatial resolution relationship in differential phase contrast ͑DPC͒ projection imaging and computed tomography ͑CT͒ are derived and compared to conventional absorption-based x-ray projection imaging and CT. Methods: The scaling law for DPC-CT is theoretically derived and subsequently validated with phantom results from an experimental Talbot-Lau interferometer system. Results: For the DPC imaging method, the noise variance in the differential projection images follows the same inverse-square law with spatial resolution as in conventional absorption-based x-ray imaging projections. However, both in theory and experimental results, in DPC-CT the noise variance scales with spatial resolution following an inverse linear relationship with fixed slice thickness. Conclusions:The scaling law in DPC-CT implies a lesser noise, and therefore dose, penalty for moving to higher spatial resolutions when compared to conventional absorption-based CT in order to maintain the same contrast-to-noise ratio.

No abstract