A novel imaging tool for hepatic portal system using phase contrast technique with hydrogen peroxide‐generated O2 gas

The objective of this study was to investigate the potential of hydrogen peroxide‐generated oxygen gas‐based phase contrast imaging (PCI) for visualizing mouse hepatic portal veins. The O₂ gas was made from the reaction between H₂O₂ and catalase. The gas production was imaged by PCI in real time. The H₂O₂ was injected into the enteric cavity of the lower sigmoid colon to produce O₂ in the submucosal venous plexus. The generated O₂ gas could be finally drained into hepatic portal veins. Absorption contrast imaging (ACI) and PCI of O₂‐filled portal veins were performed and compared. PCI offers high resolution and real‐time visualization of the O₂ gas production. Compared with O₂‐based ACI, O₂‐based PCI significantly enhanced the revealing of the portal vein in vivo. It is concluded that O₂‐based PCI is a novel and promising imaging modality for future studies of portal venous disorders in mice models.     

快中子照相模拟分析与实验验证

首次系统地推导出快中子照相像素值形成解析式, 建立图像反差不等式, 并利用该不等式首次对图像对比度与源强、照射时间和散射之间的关系进行说明. 并在像素值解析式基础上编制快中子照相模拟程序, 利用该程序对空间分辨率和图像对比度进行模拟, 并与实验对照, 研究结果表明空间分辨率模拟效果好于实验, 图像对比度模拟效果与实验相当. 最后通过对狭缝、方孔以及多材质组成的复杂样品模拟并与实验对照, 结果显示模拟效果与实验照片在反差灵敏度效果上非常一致, 该模拟计算方法可为实验设计和工程应用提供参考.     

A Frequency-Selective pH-Responsive paraCEST Agent

Paramagnetic chemical exchange saturation transfer (paraCEST) agents are well-suited for imaging tissue pH because the basis of CEST, chemical exchange, is inherently sensitive to pH. Several previous pH-sensitive paraCEST agents were based on an exchanging Ln³⁺-bound water molecule as the CEST antenna but this design often added additional line-broadening to the bulk water signal due to T₂ exchange. We report herein a pH-sensitive paraCEST agent that lacks an inner-sphere water molecule but contains one Ln-bound −OH group for CEST activation. The Yb³⁺ complex, Yb( 1 ), displayed a single, highly shifted CEST peak originating from the exchangeable Yb-OH proton, the frequency of which changed over the biologically relevant pH range. CEST images of phantoms ranging in pH from 6 to 8 demonstrate the potential of this agent for imaging pH. Initial rodent imaging studies showed that Gd( 1 ) remains in the vascular system much longer than anticipated but is cleared slowly via renal filtration.     

Unprecedented Kinetic Inertness for a Mn2+‐Bispidine Chelate: A Novel Structural Entry for Mn2+‐Based Imaging Agents

The search for more biocompatible alternatives to Gd³⁺‐based MRI agents, and the interest in ⁵²Mn for PET imaging call for ligands that form inert Mn²⁺ chelates. Given the labile nature of Mn²⁺, high inertness is challenging to achieve. The strongly preorganized structure of the 2,4‐pyridyl‐disubstituted bispidol ligand L₁ endows its Mn²⁺ complex with exceptional kinetic inertness. Indeed, MnL₁ did not show any dissociation for 140 days in the presence of 50 equiv. of Zn²⁺ (37 °C, pH 6), while recently reported potential MRI agents MnPyC3A and MnPC2A‐EA have dissociation half‐lives of 0.285 h and 54.4 h under similar conditions. In addition, the relaxivity of MnL₁ (4.28 mm ^?1 s^?1 at 25 °C, 20 MHz) is remarkable for a monohydrated, small Mn²⁺ chelate. In vivo MRI experiments in mice and determination of the tissue Mn content evidence rapid renal clearance of MnL₁. Additionally, L₁ could be radiolabeled with ⁵²Mn and the complex revealed good stability in biological media.     

Imaging the In Vivo Degradation of Tissue Engineering Implants by Use of Supramolecular Radiopaque Biomaterials

For in situ tissue engineering (TE) applications it is important that implant degradation proceeds in concord with neo‐tissue formation to avoid graft failure. It will therefore be valuable to have an imaging contrast agent (CA) available that can report on the degrading implant. For this purpose, a biodegradable radiopaque biomaterial is presented, modularly composed of a bisurea chain‐extended polycaprolactone (PCL2000‐U4U) elastomer and a novel iodinated bisurea‐modified CA additive (I‐U4U). Supramolecular hydrogen bonding interactions between the components ensure their intimate mixing. Porous implant TE‐grafts are prepared by simply electrospinning a solution containing PCL2000‐U4U and I‐U4U. Rats receive an aortic interposition graft, either composed of only PCL2000‐U4U (control) or of PCL2000‐U4U and I‐U4U (test). The grafts are explanted for analysis at three time points over a 1‐month period. Computed tomography imaging of the test group implants prior to explantation shows a decrease in iodide volume and density over time. Explant analysis also indicates scaffold degradation. (Immuno)histochemistry shows comparable cellular contents and a similar neo‐tissue formation process for test and control group, demonstrating that the CA does not have apparent adverse effects. A supramolecular approach to create solid radiopaque biomaterials can therefore be used to noninvasively monitor the biodegradation of synthetic implants.     

地面目标红外特性及其隐身技术研究

随着红外搜索与制导技术的飞速发展,对于地面目标红外特征及其隐身技术的研究具有越来越重要的军事意义.在简化目标传热模型的基础之上,计算出目标的瞬时温度变化,并与背景的温度比较发现,目标与背景在一天之中均存在明显温差,最大温差可达10℃.从目标与背景的辐射对比度出发,分析了辐射对比度与目标表面发射率以及目标与背景温差的关系,发现了当目标与背景温差控制在±4℃之内时,采用固定发射率涂料可以使目标达到红外隐身的目的.     

条纹管激光成像系统空间分辨力实验研究

简要分析了非扫描激光成像的技术优势,介绍了利用条纹管实现非扫描激光成像的工作原理,说明了图像空间分辨力与系统距离精度的对应关系。对影响图像空间分辨力的主要因素进行了理论分析,得到了系统总空间分辨力与各单元器件空间分辨力和放大倍率的对应关系,在此基础上,对现有条纹管成像系统进行了相应的计算,得到了空间分辨力的理论预期值;最后,提出了一种基于分辨力板成像的系统空间分辨力测试方法,设计了相应的验证实验,对实测图像进行了去噪处理和数据分析,得到了图像的衬比度传递函数(CTF)曲线,通过衬比度传递函数分析,计算出了成像系统的实际空间分辨力,并将实测的分辨力数据与理论值进行了对比分析。     

基于小波变换的图像融合新算法

针对现有图像融合技术中的尺度系数卷积法存在的边缘细节损失和对比度下降问题,提出了将Canny边缘检测算子等价于提取图像的小波变换模极大值点这一思想引入图像的低频分量融合规则以及用于高频子带融合的局部对比度结合方向方差方法.最后通过仿真试验以及熵值数据证明该算法有效改善了边缘细节的准确度,提高了分辨率,并使局部对比度信息得以保留,从而更加符合人类的视觉特性.     

DCE-MRI定量参数对子宫内膜癌的诊断价值及与临床病理因素的相关性

本文选取了子宫内膜癌患者108例作为观察组,另选取子宫内膜良性病变患者105例作为对照组,均行DCE-MRI检查后发现,观察组容量转移常数(Ktrans)、速率常数(Kep)、血管外细胞外间隙容积比值(Ve)高于对照组(P＜0.05);Ktrans、Kep、Ve值联合诊断子宫内膜癌的曲线下面积(AUC)为0.841;K...     

A New Oxygen Containing Pyclen-Type Ligand as a Manganese(II) Binder for MRI and 52Mn PET Applications: Equilibrium,Kinetic, Relaxometric,Structural and Radiochemical Studies

A new pyclen-3,9-diacetate derivative ligand (H₂3,9-OPC2A) was synthesized possessing an etheric O-atom opposite to the pyridine ring, to improve the dissociation kinetics of its Mn(II) complex (pyclen = 3,6,9,15-tetraazabicyclo(9.3.1)pentadeca-1(15),11,13-triene). The new ligand is less basic than the N-containing analogue (H₂3,9-PC2A) due to the non-protonable O-atom. In spite of its lower basicity, the conditional stability of the [Mn(3,9-OPC2A)] (pMn = −log(Mn(II)), c_L = c_Mn(II) = 0.01 mM. pH = 7.4) remains unaffected (pMn = 8.69), compared to the [Mn(3,9-PC2A)] (pMn = 8.64). The [Mn(3,9-OPC2A)] possesses one water molecule, having a lower exchange rate with bulk solvents (k_ex²⁹⁸ = 5.3 ± 0.4 × 10⁷ s⁻¹) than [Mn(3,9-PC2A)] (k_ex²⁹⁸ = 1.26 × 10⁸ s⁻¹). These mild differences are rationalized by density-functional theory (DFT) calculations. The acid assisted dissociation of [Mn(3,9-OPC2A)] is considerably slower (k₁ = 2.81 ± 0.07 M⁻¹ s⁻¹) than that of the complexes of diacetates or bisamides of various 12-membered macrocycles and the parent H₂3,9-PC2A. The [Mn(3,9-OPC2A)] is inert in rat/human serum as confirmed by ⁵²Mn labeling (nM range), as well as by relaxometry (mM range). However, a 600-fold excess of EDTA (pH = 7.4) or a mixture of essential metal ions, propagated some transchelation/transmetalation in 7 days. The H₂3,9-OPC2A is labeled efficiently with ⁵²Mn at elevated temperatures, yet at 37 °C the parent H₂3,9-PC2A performs slightly better. Ultimately, the H₂3,9-OPC2A shows advantageous features for further ligand designs for bifunctional chelators.