Objective To develop an ultra-sensitive nanoparticle contrast agent for magnetic resonance angiography(MRA),to establish a highly sensitive imaging method for complicated vascular structures,and to provide imaging evidence for precision diagnosis,treatment,prognosis,and individualized treatment of ischemic stroke.Methods A dual-modality MRA contrast agent was prepared through ligand exchange of ultra-small NaGdF4 nanocrystals synthesized via a high temperature method,with biocompatible polyethylene glycol(PEG-dp)ligands.The basic structure,morphology,size distribution,and relaxation rate of the NaGdF4 nano contrast agent were characterized using transmission electron microscopy(TEM),a particle size potential analyzer,and a 7.0 T small-animal MRI scanner.A total of 6 healthy male SPF-grade BALB/c mice were selected and randomly divided into two groups,a NaGdF4 group and a Gd-DTPA group.The mice in the two groups were injected with NaGdF4 nanoparticle contrast agent or clinical Gd-DTPA contrast agent(0.1 mmol Gd3+/kg)via the tail vein.MRA images were obtained using a 7.0 T small animal magnetic resonance imaging system before and after the injection.A total of 6 healthy male SPF-grade Sprague Dawley(SD)rats were selected to establish a right middle cerebral artery occlusion(rMCAO)model to simulate ischemic stroke.The rats were injected with NaGdF4 nano-contrast agent(0.1 mmol Gd3+/kg)via the tail vein.Before and after the injection,brain MRI images of the rats were obtained using a 7.0 T small animal magnetic resonance imaging system.The in vitro and in vivo biological safety of the nano contrast agent was verified through cytotoxicity and hemolysis experiments and HE staining.Results Uniform spherical oil-phase NaGdF4 nanocrystals with an average particle size of approximately(4.43±0.46)nm were successfully prepared.After ligand exchange,biocompatible water-phase nanocrystals were obtained with a hydrodynamic size of 16.1 nm and a surface potential of-1.9 mV.The relaxation performance of this nanocrystal contrast agent was significantly superior to that of the clinical contrast agent Gd-DTPA.The longitudinal molar relaxivity rate(r1)of the NaGdF4 nano contrast agent was 8.84 mM-1s-1,while the transverse molar relaxivity rate(r2)was 27.36 mM-1s-1,which were 1.96 times(4.52 mM-1s-1)and 3.37 times(8.13 mM-1s-1)those of Gd-DTPA,respectively.It also demonstrated excellent biocompatibility.NaGdF4-enhanced MRA achieved high-resolution vascular imaging and effectively enabled the differentiation of the ischemic area,infarct core,and ischemic penumbra in an animal model of ischemic stroke.Conclusion The multi-parameter MRA based on NaGdF4 nanoparticles provides critical imaging evidence for the clinical diagnosis and prognosis of ischemic stroke.

Objective:To build enhanced recovery after surgery (ERAS) ward management system based on the staff, stuff, structure space and systems (4S) management model, and explore the implementation effects of accelerated rehabilitation nursing management.Methods:A retrospective analysis was carried out on the implementation process of ERAS before 2020 in the Department of Hepatobiliary and Pancreatic Surgery, Ningbo First Hospital, Zhejiang Province. It was found that there were problems such as imperfect multidisciplinary team personnel, lack of systems, and lack of standardized process implementation rules. In April 2020, we created an ERAS ward based on the concept of 4S management model, improved the multi-disciplinary professional staff, equipment and venues, and formulated an ERAS ward system process. Patients undergoing ERAS in Hepatobiliary and Pancreatic Surgery Department from April to September 2019 were selected as the control group (383 cases of gallbladder surgery and 59 cases of liver surgery) , and patients admitted to the ERAS ward from April to September 2020 were selected as the experimental group (332 cases of gallbladder surgery and 72 cases of liver surgery) . The satisfaction, average length of hospitalization, hospitalization expenses and complication rate of the two groups of patients were compared, and doctors and nurses' specification implementation rate of the ERAS ward was counted.Results:The average length of hospitalization of patients with gallbladder surgery and liver surgery in the experimental group was shorter than that of the control group, and the hospitalization expenses were lower than those of the control group, and the differences were statistically significant ( P<0.01) . The complication rate (9.9%, 33/332) of patients undergoing gallbladder surgery in the experimental group was lower than that (16.7%, 64/383) in the control group, and the difference was statistically significant ( P<0.01) . The satisfaction of patients in the experimental group was higher than that in the control group, and the difference was statistically significant ( P<0.01) . The specification implementation rate of doctors and nurses was 96.7% (58/60) . Conclusions:The ERAS ward is based on the scientific supervision of staff, stuff, structure space and systems according to the concept of 4S management model, which is conducive to the comprehensive and standardized implementation of ERAS treatment and nursing, improves patient clinical outcomes and increases patient satisfaction.