在日常工作中对乳突的投照，常常是将暗盒放于摄影台上，我们感到有许多的不便，暗盒放于台面上易滑动，摆好位置后，患者头部稍微对暗盒用力，暗盒就会移动，使投照失败，造成废片，同时，无滤线器，二次射线对胶片影响很大，使胶片发灰．但还是没有使滤线器的效果好．所以在? In daily work on the mastoid projection, the cassette is often placed on the stage, we feel that there are many inconveniences, the cassette on the table easy to slide, put the position, the patient’s head a little force on the cassette, the cassette on Will move, so failed to vote, resulting in waste film, at the same time, no filter, the second ray of a great impact on the film, the film gray. But still did not make the filter good effect. So in?