Rad tech student here. So post LL discrepancy surgery, a pt's limb was placed in a ring external fixation device. It looks something like an Ilizarov device to me, but I'm not 100% on what the device used in the hospital was. The pt is sent down for an ap/lat knee x-ray with very specific instructions to get the distal ring in profile + centered to a tab. They specially called a senior radiographer over to do this case. Dude got the images in one shot each. The ring was perfectly superimposed in a straight line, the tab was perfectly centered. The rad explained that he looks carefully at the shadow thrown by the device to judge if he has angled enough. However, he had to leave asap for something else and I didn't get to ask him about the rationale behind such specific instructions from the doc. Wondering if this community knows why we have to do this, and whether there are links to resources that help to explain this view. I couldn't find any articles in my own searc...