The Observation Of Multi-slice CT In Nasal Bone And Its Fine Structure

Objective:To study the morphological characteristic,variation,and CT imaging of nasal bone and nasal foramina and explore the application value of different scanning parameters and postprocessing techniques in differentiation of nasal foramina and nasal bone fracture.Methods:Twenty dry human skulls were performed 16 slices spiral CT scans from frontal sinus to hard palate.The scan parameters were as follows:tube voltage 140Kv,tube current 100mAs,collimation 0.75mm,bed speed 6.6mm/rot, matrix 512×512,FOV 310mm,Pitch 0.6,pitch 1.0,pitch 1.4 respectively.After acquired original axial images,post procession were performed and then input the images into WIZARD workstation to acquire the MPR and INSPACE images. Then the optimal parameters of multi-slice CT scan and post procession techniques were determined to display the anatomic structures of nasal bone and nasal foramina.200 patients were performed nasal bone by 16 slice spiral CT scanner from Jan 2007 to March 2008 in Shandong Medical Imaging Research Institute.50 cases with nasal fracture and 150 cases without nasal fracture were included.The imaging quality was evaluated by sharpness.CT images which can not demonstrate nasal anatomic structure were defined 1 score;images with significant step formation artifacts were defined 2 score;images without artifacts and can not accurately show the fine nasal structure were defined 3 score; imaging which could be used to diagnose for showing nasal anatomic structure clearly were defined 4 score;images which perfectly demonstrate the distribution, direction and local anatomic structure of the nasal bone structure and nasal foramina were defined 5 score.The paired-sample t test were used and p＜0.05 were considered statistical significance.Results:①Adjust the pitch from 0.6 to 1.4,there were no significant difference for MPR images of nasal foramina structures.Changed reconstruction space from 0.3 to 0.5,the quality of MPR and INSPACE images did not improve.However, the quality of post procession images was significantly improved when the reconstruction space from 0.5 to 1.The bigger convolution kernel,the higher post procession images.The images which obtained by used clinic common scanning and postprocessing parameter can meet the requirement to diagnose nasal bone fracture and show nasal bone foramina as well as dry human skulls do..②(The mean length of nasal bone was 28.9mm for adult male,27.5mm for adult female, and 24.4 for under adult patients.Irregularity of nasal bone inferior margin is displayed on plain spiral CT.Nasal foramina usually located at the junction of 1/3 to 1/2 of nasal bone.It may be lower in child than adult.In CT images,nasal foramina may show discontinued line.The variation of nasal foramina is variety.③There are several differentiated diagnosis points:firstly,in CT images,nasal foramina can only be displayed in continued 3 to 5 slices,while nasal bone fracture line displayed in more slices.In addition,nasal foramina are natural, fuzzy edges,less sharp margin,while the fracture line is rigid,sharp margin.At last,nasal bone fracture line is usually company with obvious wrong angle dislocation,while nasal foramina are regular on both sides.Conclusion:The optimal multi-slice CT scanning parameters and post-processing parameters can show the nasal bone and nasal foramina anatomical structure well.Based on the CT images,nasal bone fracture could be accurately diagnosed and identified from normal nasal foramina.