Study On The Diameter Measurement Of Nerve Fiber Based On Light Microscope Images

The brain is the supreme commander of the human body.From simple body movements to advanced emotional thinking are inseparable from brain control.Neurons are the smallest functional units of the brain.Different types of neurons have different morphological and structural characteristics,playing different functions.Fiber diameter is one of the basic morphological parameters of neurons,which is closely related to the topology,connection mode and signal transmission efficiency of neurons.Therefore,it is very important to accurately obtain the diameter information of nerve fibers for the simulation of the signal transmission process in neural circuits.It is still challenging to obtain the diameter of nerve fibers in the whole brain.With the help of high-resolution imaging techniques such as electron microscopy,researchers can obtain nanoscale images of the fine structure of neurons,which is the "gold standard" for obtaining local morphological parameters of neurons.However,due to the limitations of sample preparation and imaging speed,it is difficult for researchers to measure neuronal diameter in the whole brain with electron microscopy.In recent years,with the development of light microscopy,it has been possible to obtain the fine structure of neurons with high resolution in the whole brain.But because of the huge amount of data,complex image features and resolution limit,it is still difficult to accurately measure the axon diameter of long-range projection neurons.As a result,the diameter information of neurons is often ignored in existing reconstruction methods,or replaced by cylinders with uniform diameter,which leads to errors in subsequent research work such as neuron simulation.In addition,there is a huge amount of neuronal image data in the whole brain,and manual measurement will face the problems of heavy workload and low efficiency.To this end,this paper optimizes the "accuracy" and "automation" in the process of neuron axon diameter measurement,and on this basis,establishes the process framework of axon diameter measurement.In this thesis,combined with biological knowledge and optical microscope images,the measurement of axon diameter of long-range projection neurons in mice was studied.By analyzing the principle of neuron labeling and morphological characteristics,the definition of neuronal axon diameter and the source of the signal of the measured object are clarified.Furthermore,in order to improve the accuracy of fiber diameter measurement,this paper optimizes the complete measurement process,proposes the method of measurement data pre-processing and measurement result correction,and quantitatively analyzed the measurement error caused by the point spread function in optical microscopic images.Finally,this study establishes the measurement framework of neuron axon diameter,and combines with the neuron topology skeleton to realize the automatic measurement of neuron axon diameter in the whole brain,which is applied to the real neuron data to explore the distribution law of neuron axon diameter.Compared with the existing methods,this new measurement method is based on the real morphology of axons,combine with the marker principle and image features,and proposes a new measurement idea.It can measure axon diameter more accurately and automatically.In the study of the distribution of axonal segment diameter,it is found that the diameter decreased significantly during axonal elongation when the branches are generated,which is consistent with the conclusion of previous studies.In addition,in the study of the axon diameter of long-range projection pyramidal neurons,it is found that with the increase of path distance and the number of axon branches,the axon diameter mainly decreased,and there is a positive correlation between the diameter and the number of sub-branches.Furthermore,it is found that axons with cell bodies in the same brain region and different projection patterns also have significant differences in the average diameter of their trunk,suggesting that the average diameter of axons can also be used as one of the attributes with potential for neuron classification.In summary,this paper studies the measurement of nerve fiber diameter in light microscope images and establishes an accurate and automatic measurement method of axon diameter in the whole brain.It can obtain the axon diameter of long-range projection neurons and their distribution rules.By comparing the differences of axon diameter data,the potential law between axon diameter and axon projection pattern is revealed.The research results will provide an important reference for future research on neuronal morphology measurement,simulation,reconstruction analysis and visualization.