| BackgroundCauda equina is a special kind of peripheral nerve,which is weaker than normal peripheral nerves and has weak resistance to adverse external stimuli.In the event of injury,serious symptoms of lower extremity dysfunction,sellar sensation,and dexterous dysfunction may occur,the prognosis of surgical treatment is poor,the degree of recovery of nerve function is limited,have brought a heavy economic and mental burden to patients and their families.At present,little substantive progress has been made on the basic and clinical researches of cauda equina injury,and there is also lack of innovative techniques and methods in neuroimaging research.In the current study of neuro-morphology of cauda equina,the most commonly used detection methods are light microscopy and electron microscopy.Observing the nerve tissue section stained under the microscope,although it can achieve high resolution,it is limited to illumination beams and electrons.The penetrating ability of the beam cannot be directly used for the three-dimensional imaging of the internal space structure of the sample.Only a clear two-dimensional image of the local sample can be obtained,and the three-dimensional spatial structure within the nerve cannot be observed.It can only obtain a clear two-dimensional image of the local specimen,making it difficult to image the entire tissue and failing to observe the three-dimensional spatial structure of the nerve.Synchrotron radiation is a continuously distributed electromagnetic radiation emitted by tangential particles along an orbital path due to acceleration.Due to its unique and excellent characteristics such as high purity,high brightness,high collimation,high polarization and quasi-coherence,and Its great advantage in temporal and spatial resolution enables three-dimensional and dynamic observation of tiny tissues and even cells.At present,some biologists have been investigating the three-dimensional structure of biological macromolecules based on synchrotron radiation source.Phase contrast imaging is a new theory and technique of imaging.It uses the X-ray refraction effect and different refractive index of different tissues to carry out imaging.It has the spatial resolution in the order of microns and the resolution of soft tissue composed of light elements is increased by 1000 Times,so it can have a good imaging results and high resolution on the nerve,blood vessels,ligaments and soft tissue tumors.At present,synchrotron radiation phase contrast imaging has been used for three-dimensional imaging of cerebrovascular,spinal vascular,and liver tissues with a resolution of microns,which can clearly observe the internal structure and subtle changes of tissue and provide new findings for clinical research.So far,synchrotron radiation imaging applied to cauda equina injury has not been reported.Therefore,the subject of synchronous phase contrast imaging applied to observe the morphological changes of normal and acute cauda equina injury of cauda equina nerve fibers and internal spatial structure,to provide a new theoretical support for the treatment of nerve injury and repair of cauda equina injury.ObjectiveTo establish the model of acute cauda equina injury in rats.After the specimens were obtained,the cauda equina nerve was stained with osmium tetroxide.Phase contrast imaging was performed on normal and injured cauda equina using high-brightness and high-dry coherence X-ray generated by Shanghai Synchrotron Radiation Source(SSRF).To observe the changes of the internal structure of the cauda equina nerve after injury,and to provide new theoretical support for the injury repair of cauda equina.Methods1.24 adult SD rats were selected and divided into control group(n=6),sham operation group(n=6),model group 1(n=6).and model group 2(n=6).After inhaled anesthetized with seven fluothane,L5-6 laminectomy was performed.Injured rats were treated with modified Allen,s weight impact method to make rat model of acute cauda equina injury of L5-L6.Postoperative BBB score,tail-flick were used to evaluation the behavioral changes in rats,and the HE staining,immunofluorescence staining,LFB staining of the specimens were used to observing the pathological changes of cauda equina nerve tissue.2.The cauda equina specimens were processed with formaldehyde fixation,alcohol gradient dehydration,osmium acid staining,epoxy resin embedding,making synchronous radiation phase contrast imaging experimental specimens.3.Phase contrast imaging was performed at the BL13W1 biomedical station of Shanghai Synchrotron Light Source(SSRF)to obtain the original projection image.4.Using PITRE and PITRE-BM software,the original image was phase-restored,sinogram reconstructed and slice generated.Three-dimensional reconstruction of the slice was performed with VG Studio MAX 3.0 software and the cauda equina was three-dimensionally imaged.5.Compare and analyze the changes of internal space structure and changes of nerve fibers in normal cauda equina and injured cauda equina.Result1.Established a cauda equina acute injury model successfully.2.Imaging the cauda equina using phase-contrast technique,a high-resolution tomographic image can be obtained,and the three-dimensional imaging of the cauda equina and internal nerve fibers can be further reconstructed.Equivalent to three dimensional CT examination of the cauda equina nerve was performed by the application of synchrotron radiation imaging.3.By comparing the images and the three-dimensional images of normal cauda equina and the injured cauda equina,we found that when the mechanical injury resulted in acute injury of cauda equina,myelin sheath was swollen and disintegrated,and the nerve fiber went disorder,the volume ratio of myelin sheath in the nerve decreased.For the lesser damage of the cauda equina,the proportion of the volume ratio increases with the edema of the nerve and the myelin sheath.ConclusionThe acute cauda equina nerve injury model established by Allens heavy impact method is simple and repeatable.It simulates the pathogenesis of acute injury of cauda equina under mechanical action well.Using synchrotron radiation phase contrast imaging technique,three-dimensional imaging of the cauda equina nerve was performed to obtain the three-dimensional structure information of the cauda equina and inner nerve fibers on the order of microns.The morphological changes of the cauda equina nerve in the normal state and the acute injury were observed more clearly and intuitively.And this can provide theoretical and technical support for cauda equina injury repairment. |
PDF Full Text Request