Noise-robust Mojette reconstruction using sparse-view CT projections.

Sparse-view Computed Tomography (CT) has important significance in industrial inspection and medical diagnosis. Mojette transform is a kind of discrete Radon transform that can yield exact reconstructions instead of an approximate solution due to finite Radon sampling. However, the image is iteratively reconstructed pixel by pixel from corner to center, and the image error is proportional to the number of iterations. In this paper, we propose that there exist different sets of projection combinations to recover the original image within the close-to-minimal iterations. And a scheme is given to obtain multiple projection sets, each of which has the same number of minimum iterations and can recover a CT image with a similar level of small noise but different distributions. These images can be used further to restore the final CT image by counteracting noise with each other. The accuracy and validity of the proposed algorithm are verified by comparison with both other Mojette inversion algorithms and the classical SART algorithm.

Priority-based Mojette reconstruction from sparse noisy projections.

Sparse-view Computed Tomography (CT) plays an important role in industrial inspection and medical diagnosis. However, the established reconstruction equations based on traditional Radon transform are ill-posed and obtain an approximate solution in the case of finite sampling angles. By contrast, Mojette transform is considered as the discrete geometry of the projection and reconstruction lattice. It determines the geometrical conditions for ensuring a unique solution instead of solving an ill-posed problem from the start. Therefore, Mojette transform results in theoretical exact image reconstruction in the discrete domain, and approximately gets the minimum number of projections, as well as their directions. However, the reconstruction method utilizing Mojette transform is very sensitive to noise. To address the problem, the paper proposes a sparse-view Mojette inversion algorithm based on the minimum noise accumulation by selecting the prioritized projections for an image reconstruction. Experimental results show that the proposed method can effectively suppress the noise accumulation without increasing the number of projections and produce better reconstruction results than traditional corner-based Mojette inversion (CBI).

Effects of preventative application of metformin on bile acid metabolism in high fat-fed/streptozotocin-diabetic rats.

OBJECTIVE: This study was designed to investigate the effects of metformin on bile acid in type 2 diabetes mellitus (T2DM). METHODS: In this study, we constructed a model of T2DM by a combination of high-fat diet (HFD) and low dose of streptozotocin (STZ) intraperitoneal injection. Blood samples by tail vein and eye angular vein were withdrawn before (time 0) and 30, 60, and 120 minutes after administration of glucose before STZ injection and once a week after diabetes induction, and were analyzed to evaluate the level of the fasting blood glucose and fasting insulin using glucometer. Triglyceride, low density lipoprotein cholesterin, high density lipoprotein cholesterin were detected by automatic biochemical analyzers. Total cholesterol and total bile acid (TBA) were analyzed using ELISA kits. RESULTS: Before STZ injection, the TBA level in HFD group was significantly higher relative to that in standard diet (SD) group and there was a moderate reduction of the TBA level in early intervention (EI) group 6 week after metformin administration comparing with that in HFD group but was still higher than that of SD group. However, after STZ injection, the TBA level was significantly higher in DM rats relative to that in normal control (NC) rats and the TBA level in late intervention (LI) (19.92 µmol/L) and EI rats (42.97 µmol/L) with metformin administration was significantly higher comparing with that in DM rats. CONCLUSION: The effects of metformin in plasma glucose and lipid metabolism might be associated with bile acid metabolism.

[Expressions of atherosclerosis-related genes in aorta in young apoE/LDLR double knockout mice].

To systematically clarify the effects of apolipoprotein E (aopE) and low-density lipoprotein receptor (LDLR) gene mutant on hyperlipidemia, vascular inflammation impairment and pathogenesis of atherosclerosis (AS), total RNA was isolated from fresh aortas of young apoE/LDLR double knockout (apoE(-/-)/LDLR(-/-)) and wild type (WT) mice using TRIzol reagent. Then RNA was reversely transcribed to first-strand cDNA by reverse transcriptase for reverse transcription polymerase chain reaction (RT-PCR) and real-time RT-PCR. Primer pairs were designed using primer design software according to the gene sequences available in GenBank. ß-actin was used as an internal control. Then RT-PCR assay was used to analyze the expression patterns of interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α), nuclear factor-κB (NF-κB), granulocyte-macrophage colony-stimulating factor (GM-CSF), CD36, endothelin-1 (ET-1), toll-like receptor 2 (TLR2), monocyte chemoattractant protein-1 (MCP-1), vascular adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and platelet-derived growth factor-α (PDGF-α). SYBR Green quantitative real-time RT-PCR was used to validate gene expressions identified by RT-PCR. Blood samples were taken from the retro-orbital venous plexus, and serum levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were measured by using biochemical techniques. Serum concentrations of circulating TNF-α, IL-1ß and oxidized LDL (ox-LDL) were determined by ELISA. Frozen sections of aortic sinus were stained with Sudan IV to visualize intimal fatty lesions. The results showed that the relative expressions of IL-1ß, GM-CSF, ET-1, TLR2, CD36, MCP-1, ICAM-1 and VCAM-1 in apoE(-/-)/LDLR(-/-) mice at the age of 1 month were higher than those in age-matched WT mice (P<0.05, P<0.01), respectively. The expressions of PDGF-α and TNF-α in apoE(-/-)/LDLR(-/-) mice at the age of 2 months were up-regulated compared to those in age-matched WT mice (P<0.05). All the expressions of target genes continued to be up-regulated (P<0.05, P<0.01) except that ET-1 expression at the age of 2 months, TLR2, VCAM-1 and ICAM-1 expressions at the age of 3 months were down-regulated to that in WT mice. NF-κB expression had no significant changes between two genotype mice at different ages. All the gene expressions kept unchanged in WT mice at different ages, except that IL-1b expressions were slightly up-regulated at the ages of 2 and 3 months. Serum levels of TC, TG, LDL, HDL, TNF-α, IL-1ß and ox-LDL in apoE(-/-)/LDLR(-/-) mice at different ages were higher than those in age-matched WT mice (P<0.05, P<0.01), and were increasing with age. Primary atherosclerotic lesions were observed in 1-month old apoE(-/-)/LDLR(-/-) mice and were progressing with age. There were no lesions observed in all WT mice at different ages. The data suggest that hyperlipidemia due to apoE and LDLR gene mutant may stimulate the temporal expressions of AS-related genes and contribute to primary atherogenetic lesions and vascular inflammation impairment.