Radiologists are able to work with internal medicine, pediatrics, surgery, obstetrics, and all the sub-specialties, giving radiologists a huge range of things they can participate in. Although a radiologist is a physician, they generally don't interact with patients. In a way, radiologists are doctor's doctors. When a physician is not sure about a certain problem his patient is having, he will order a test (an x-ray, MRI, CT scan, or an ultrasound) and will sometimes consult with the radiologist personally to try and figure the problem out.
Typically, whatever the results are that come back from the radiologist will determine the course of the patient's therapy. Even though a radiologist doesn't get a lot of patient recognition and gratitude for their work, they do get a lot of satisfaction in knowing that what they do makes a big difference in people's lives everyday.