Planer Angles And Spatial Position Of The Semicircular Canals

Background:The planer angle and spatial position of the semicircular canals are very important for the study of vestibular function and patients with vestibular diseases.The spatial orientation of the semicircular canals may play a key role in reducing the diagnosis and treatment of benign paroxysmal positional vertigo.Purpose:This study aimed to measure the mutual angle and spatial position direction of the semicircular canals,compare the differences of different detection methods(CT vs MRI)and angle measurement methods and explore a new MRI image reference coordinate system.Methods:A total of 101 cases of mastoid CT and 111 cases of internal auditory canal MRI were selected from patients in the First Affiliated Hospital of Guangzhou Medical University from 2018 to November 2020.Mimics 21.0 software was used to reconstruct the semicircular canal and establish a spatial coordinate system.The rotating coordinate plane method,the 3-point plane method and the multi-point coordinate fitting plane equation method were used to measure the mutual angle and spatial direction of the semicircular canals.By establishing five different coordinate horizontal planes to compare the difference of different coordinate horizontal planes,and a new MRI image coordinate system was established.Finally,the mutual angle and spatial position angle of the semicircular canals reported in the literature were summarized by the method of Meta-analysis.Result : Mastoid CT and internal auditory canal MRI could clearly show the anatomical structure of the cochlear semicircular canal after three-dimensional reconstruction;The results of different angle measurement methods were statistically different(P<0.05);By using the multi-point coordinate fitting plane equation method,the mutual angle and spatial position angle of the semicircular canals based on CT and MRI were not statistically significant(P>0.05).The multi-point coordinate fitting plane equation method measures the angle between the anterior semicircular canal(ASCC)and the horizontal semicircular canal(LSCC)was 85.11°± 5.78,the angle between ASCC and posterior semicircular canal(PSCC)was 94.71°± 4.51,and the angle between the LSCC and PSCC was 92.37°± 5.37.Additionally,the angle of the sagittal plane to PSCC was 48.57°± 4.52 and angle of the horizontal plane to LSCC was 15.76°± 3.98.This study found that the angles between the LSCC and the center point of the eyeball and the vertex ASCC plane and the horizontal plane of the Reid’s coordinate system were 15.23°± 4.56 and 15.63°± 4.08,respectively,and the difference was not statistically significant(P>0.05);A new rectangular coordinate system(W-X coordinate system)was established to measure the spatial position and angle of the semicircular canal,based on the eyeball center point-the the vertex of ASCC plane.There was no statistically significant difference between W-X coordinate system and Reid coordinate system(P>0.05).Finally,a meta-analysis of the results of 16 articles found that the mutual angle of the semicircular canals was basically consistent with the measurement results of this paper.Conclusion: The mutual angle and spatial position of the semicircular canals have great individual differences and the measurement results of different angle measurement methods were different.In addition,there was no difference in the mutual angle and spatial direction of semicircular canals in mastoid CT and internal auditory canal MRI image.Finally,W-X coordinate system could be used as a new reference coordinate system for cranial image.