Objective: To study magnetic resonance elastography (MRE) technique. Methods: An external force actuator was developed, the imaging pulse sequence of MRE was designed,and tissue simulating phantoms were constructed. The actuator controlled by the pulse sepuence produced shear waves at low frequency on the surface of the phantoms. A modified gradient echo sequence was developed with motion sensitizing gradient (MSG)imposed along X,Y or Z direction.Cyclic displacement within the medium induced by shear waves caused a measurable phase shift in the received MR signal.From the measured phase shift,the displacement at each voxel could be calculated,and the propatating shear waves within the medium were directly imaged. By adjusting the phase offsets,the dynamic propagation of shear waves in a wave cycle was obtained.The phase images were processed to aquire quantitative elasticity image using local frequency estimation(LFE)method. The experiments were implemented with 1.0% and 1.5% tissue simulating agarose gel. Shear waves at frequency of 150 Hz,200 Hz,250 Hz,and 300 Hz were applied. Results: The phase images of MRE directly imaged the propagating shear waves within the phantoms.The wavelength of shear waves varied with the change of exciting frequency and stiffness of the phantoms. The wavelength of shear waves was exactly proportional to the frequency and stiffness of the phantom. The contrast of elasticity in agarose gel with two concentrations was clearly demonstrated on elasticity images.Conclusion: The phase images of MRE can directly visualize the propagation of shear waves in the medium. The elasticity image of MRE can quantitatively image the elastic modulus of the medium

Objective To investigate the potential values of magnetic resonance elastography (MRE)for evaluating the brain tumor consistency in vivo.Methods Fourteen patients with known solid brain tumor(5 male,9 female;age range:16-63 years)underwent brain MRE studies.Informed consent was obtained from all patients.A dedicated external force actuator for brain MRE study Was developed.The actuator was fixed to the head coil.During scan.one side of the actuator was attached to the patients'head.Low frequency oscillation Was produced by the actuator and caused shear waves propagating into brain tissue.The pulse sequence used in the study Writs phase-contrast gradient-echo sequence.Phase images of the brain were obtained and the shear waves within the brain were directly imaged.Phase images were processed with local frequency estimation (LFE) technique to obtain the elasticity image.Consistency of brain tumors Was evaluated at surgery and Was classified as soft,intermediate,or hard with comparison to the white matter of the brain.Correspondence of MRE evaluation with operative results was studied.Results The elastic modulus of the tumor Was lower than that of white matter in 1 patient,higher inll patients,and similar in 2 patients.At surgery,the tumor manifested a soft consistency in I patient,hard consistency in 11 patients,intermediate consistency in 2 patients.The elasticity of tumors in 14 patients evaluated by MRE was correlated with the tumor consistency on the operation.Conclusion MRE Can noninvasively display the elasticity of brain tumors in vivo,and evaluate the brain tumor consistency before operation.

Objective:To investigate the application of virtual reality technology combined with case-based learning in forward surgical team (FST) basic skill teaching for undergraduates.Methods:A total of 42 undergraduates who received clinical practice in The Second Affiliated Hospital of Navy Medical University from January 2020 to January 2021 were selected as research subjects, and they were randomly divided into experimental group (virtual reality technology combined with case-based learning for FST basic skill teaching) and control group (traditional teaching methods for FST basic skill teaching). A questionnaire survey and assessments were performed to evaluate the effectiveness of teaching, and SPSS 23.0 was used to perform the t-test, the chi-square test, or the Fisher's exact test. Results:The questionnaire survey showed that there were no significant differences between the two groups in the degree of overall satisfaction with teaching, comprehension and practice in learning, and post-learning memory, and compared with the control group, the experimental group had significantly higher scores of improvement in theoretical knowledge (4.33±0.26 vs. 4.17±0.21, P<0.05), improvement in skill operation (4.32±0.22 vs. 4.12±0.27, P<0.05), improvement in the ability to analyze and solve practical problems (4.04±0.37 vs. 3.69±0.38, P<0.05), learning interest and enthusiasm (4.34±0.28 vs. 3.92±0.43, P<0.05), learning attention (4.21±0.35 vs. 3.81±0.34, P<0.05), and learning interaction (4.18±0.29 vs. 4.01±0.21, P<0.05). The results of assessments showed that compared with the control group, the experimental group had a significantly higher total score (85.96±5.35 vs. 77.03±7.29, P<0.05) and significantly better scores of theoretical knowledge (28.25±4.74 vs. 25.01±5.37, P<0.05) and skill operation (57.47±4.96 vs. 51.99±8.03, P<0.05). Conclusions:Virtual reality technology combined with case-based learning has unique advantages in FST basic skill teaching for undergraduates, and related studies and application research can be conducted in the future.

Pulmonary blast injury has become the main type of trauma in modern warfare, characterized by externally mild injuries but internally severe injuries, rapid disease progression, and a high rate of early death. The injury is complicated in clinical practice, often with multiple and compound injuries. Currently, there is a lack of effective protective materials, accurate injury detection instrument and portable monitoring and transportation equipment, standardized clinical treatment guidelines in various medical centers, and evidence-based guidelines at home and abroad, resulting in a high mortality in clinlcal practice. Therefore, the Trauma Branch of Chinese Medical Association and the Editorial Committee of Chinese Journal of Trauma organized military and civilian experts in related fields such as thoracic surgery and traumatic surgery to jointly develop the Clinical treatment guideline for pulmonary blast injury ( version 2023) by combining evidence for effectiveness and clinical first-line treatment experience. This guideline provided 16 recommended opinions surrounding definition, characteristics, pre-hospital diagnosis and treatment, and in-hospital treatment of pulmonary blast injury, hoping to provide a basis for the clinical treatment in hospitals at different levels.