Structural control of magnetic nanoparticles for positive nuclear magnetic resonance imaging

In addition to the tens of millions of medical doses consumed annually around the world,a vast number of nuclear magnetic resonance imaging(MRI)contrast agents are being deployed in MRI research and development,offering precise diagnostic information,targeting capabilities,and analyte sensing.Superparamagnetic iron oxide nanoparticles(SPIONs)are notable among these agents,providing effective and versatile MRI applications while also being heavy-metal-free,bioconjugatable,and theranostic.We designed and implemented a novel two-pronged computational and experimental strategy to meet the demand for the efficient and rigorous development of SPION-based MRI agents.Our MATLAB-based modeling simulation and magnetic characterization revealed that extremely small maghemite SPIONs in the 1-3 nm range possess significantly reduced transversal relaxation rates(R_(2))and are therefore preferred for positive(T_(1)-weighted)MRI.Moreover,X-ray diffraction and X-ray absorption fine structure analyses demonstrated that the diffraction pattern and radial distribution function of our SPIONs matched those of the targeted maghemite crystals.In addition,simulations of the X-ray near-edge structure spectra indicated that our synthesized SPIONs,even at 1 nm,maintained a spherical structure.Furthermore,in vitro and in vivo MRI investigations showed that our 1-nm SPIONs effectively highlighted whole-body blood vessels and major organs in mice and could be cleared through the kidney route to minimize potential post-imaging side effects.Overall,our innovative approach enabled a swift discovery of the desired SPION structure,followed by targeted synthesis,synchrotron radiation spectroscopic studies,and MRI evaluations.The efficient and rigorous development of our high-performance SPIONs can set the stage for a computational and experimental platform for the development of future MRI agents.

In-situ observation and modeling approach to evolution of pore-fracture structure in coal

The characterisation of the pore-fracture structure(PFS)and its evolution in coal during mining are essential for preventing gas outbursts and improving gas extraction efficiency.In this study,the evolution of the PFS in coal samples under the condition of mining stress was directly captured in situ by combination of the mechanical testing system with high-precision visualisation nuclear magnetic resonance equipment.A fractional derivative model was established to describe the relationship between stress and porosity based on experimental results of the PFS under different stress states.The results showed that with an increase in the deviatoric stress,the adsorption pore content increases rapidly initially and then increases slowly or remains unchanged;the seepage pore and fracture(SPF)content decreases initially and then increases.The SPF compressibility coefficient decreases with an increase in the deviatoric stress.The fractional derivative model can accurately describe the stress sensitivity of the SPFs at the pre-peak stage,thus providing a new approach for accurately characterising the seepage characteristics of coal reservoirs.

Imbibition characteristics of sandstone cores with different permeabilities in nanofluids

The core imbibition and shifting nuclear magnetic resonance(NMR) imaging experiment has loss of surface oil phase and air adsorption, which will affect the accuracy of the experiment result. To solve this issue, a modified experiment method, in-situ imbibition NMR method has been worked out. This method was used to carry out sandstone core imbibition experiment in nanofluid, and the oil migration images in the entire process were recorded. In combination with physical properties of the sandstone cores and the variations of the driving force during the imbibition process, imbibition characteristics of the sandstone cores with different permeabilities in nanofluid were analyzed. The results show that: the nanofluid can greatly reduce the interfacial tension of oil phase and improve the efficiency of imbibition and oil discharge, the higher the concentration, the lower the interfacial tension and the higher the efficiency of imbibition and oil discharge would be, but when the concentration reaches a certain value, the increase in imbibition and oil discharge efficiency slows down;the rise of temperature can reduce the oil viscosity resistance and interfacial tension, and hence enhance the imbibition and oil discharge rate;when the sandstone core is higher in permeability, the bottom crude oil would migrate upward and discharge during the imbibition, the higher the permeability of the sandstone core, the more obvious this phenomenon would be, and the phenomenon is shown as top oil discharge characteristic;when the sandstone core is low in permeability, the crude oil in the outer layer of the sandstone core would discharge first during the imbibition, then crude oil in the inside of the core would disperse outside and discharge, which is shown as oil discharge characteristic around the core;but under long time effect of nanofluid, the core would become more and more water-wet and reduce in the oil-water interfacial tension, so would have top oil discharge characteristic in the later stage of imbibition.

Study of MR image for involvement of paranasal sinuses in 56 cases with nasopharyngeal carcinoma

Objective： The aim of the study was to study the nuclear magnetic resonance image （MRI） feature for involvement of paranasal sinuses in patients with nasopharyngeal carcinoma （NPC）. Methods： The MRI of 56 patients with NPC and paranasal sinuses infringed were evaluated between December 2003 and August 2004. Results： Among them, 56 （100%） showed breakage in the wall of paranasal sinuses, 29 （51.8%） had thick mucous membrane in sinuses, 36 （64.3%） showed tumour invasion sinuses, 55 （98.2%） connected with primary carcinoma with the lesion, and 14 （25%） stored up fluid in si- nuses. On MRI scan technique, the positive ratios of diagnoses were 66.1%, 76.8%, and 98.2% respectively （P 〈 0.000） in the horizontal section, coronal section and sagittal section. And nearly 60% was in the TlWl and T2Wl, but 100% in strengthen scan. Conclusion： The findings of sinuses wall breakage, thick mucous membrane in sinuses, tumour invasion cavity connective mass, and same enhancement signal in MR image may indicate the paranasal sinuses involved by primary turnout. The sagittal section and enhanced MRI scans are helpful to diagnosis.