Imaging is a technical way of making pictures of the inside of a body, so a doctor can look without cutting. X-rays, ultrasound, CT, and MRI are kinds of imaging. The hospital department that does this is often called medical imaging. It is a cold, scientific word: you “have imaging”, or “imaging showed a break in the bone”. Though actually, the same word is used outside hospitals too — a satellite can do imaging of the earth — but the meaning you need first is the medical one. It is not the same as imagining, which happens only in the mind.