长焦距髁突经咽侧位定位摄影架的研究

目的：髁突经咽侧位X线片可以清楚显示髁突骨质的微细结构，以往本片位的摄影方法X线源与患者皮肤的踊跃过近，皮肤辐射计量较大，本文研究出长焦距髁突经咽侧位的摄影方法，在X线源距皮肤20cm以上前提下，所拍摄影像可满足诊断要求，并有较好的可重复性，方法：在对100例成年患者定位头颅正侧位片测量分析基础上计算出适合大多数患者的最佳入射角，向头侧倾斜5度和向枕侧倾斜5度，依此制作长焦距定位摄影架，并进行20例（40侧）临床病例的照片图像显示效果评定和重复性检验，将这组病例的结果与20例（40例）短焦距摄影方法的病例进行比较，结果．；长焦距髁突经咽侧位片摄影效果与短焦距摄影片效果比较，甲级扯率从65％提高到72．5％。重量性比较结果与短焦距摄影方法基本相同，结论：将传统髁突经咽侧位改为长焦距摄影，可降低X射线对患者的照射剂量，使其达到国际放射卫生防护标准，由于使用了定位摄影架，本方法可使摄影技术难度下降，易于被初学者掌握。

The investigation of long distance projection of transpharyngeal projection

Objective The condylus can be shown very clearly with the transpharyngeal projection.But the focus-skin distance is only 10cm with the traditional method.which is shorter than the limitation of ICRP and has a higher risk of radiation.In this investigation,we tred to design a fixture device for this projection with 20 cm focus-skin distance and checked the image quality and its repetition.Methods After measuring on the lateral cephalography of 100 cases and calculating the best projecting angle of vertical and horizontal,we designed and made the long distance projection fixture.We applied the new method for 40 films (20 cases) in clinic.The 40 images were compared with other 40 radiograph projected by traditional method.Results The rate of first level image in the traditional method was 65%,while the rate of new method was 72.5%.The results of repetition of the two methods were similar.Conclusion With the new designed fixture device,the transpharyngeal projection could be taken with 20cm focus-skin distance,the new method is useful for clinic and easy to master.