Question

8. A 20 degree caudal angle was used on a particular AP exam. If the patient had to be imaged with a PA projection, how would the angle change to produce the same image?

Answer 1

The difference in AP and PA projection is important to know so here we talk about the difference between them then we will consider the given situation .

In simple words, during the procedure of taking x-ray radiograph when x-ray passes from posterior of body to anterior, it is called PA view. While in AP view the direction is opposite.

Now let's understand the importance of doing this. According to concepts of physics the less the distance between the object and screen more clearer shadow is formed. In this case x-ray is the light source and we are the object. So, in AP view posterior aspect gives better shadow, while in PA view anterior aspect gives better shadow.

The angle difference between the AP and PA view is maximum of 15-20 degrees when talking about same image.

Here the given situation suggest 20 degree caudal angle for AP exam . So for PA it has to be

20(+-) 15

It is 5 degrees or 35 degrees

Getting it at at 5 degrees is hard so we prefer the 35 degrees angle .