Imaging study · Low dose
X-ray
Also known as: plain radiograph, chest X-ray, CXR, radiograph, plain film
The oldest and most widely available imaging test: a brief beam of X-rays casts a shadow picture of bone, air and soft tissue, ideal for fractures, chest infections and dental checks.
How it works
A brief pulse of X-rays passes through the body onto a digital detector. Dense tissue such as bone absorbs most of the beam and appears white; air absorbs almost none and appears black; soft tissue and fluid are shades of grey in between. The image is a two-dimensional shadow of everything in the beam's path.
What it shows
- Bone: fractures, dislocations, arthritis, bone tumours and infection
- Chest: pneumonia, fluid, collapsed lung, heart size, tumours
- Abdomen: bowel obstruction, free air from a perforation, some stones
- Teeth and jaw
- Foreign bodies made of metal or glass
Best for
- A first look at bones and the chest: fast, cheap and available everywhere
- Following fracture healing
- Bowel obstruction and perforation as a screen
Not the right tool for
- Soft tissues such as ligaments, cartilage, brain and spinal cord
- Early stress fractures and small bone injuries (MRI or CT)
- Subtle lung disease (CT)
What to expect
- Modality
- X-ray (radiography)
- Preparation
- None. Remove metal from the area; tell the radiographer about any possibility of pregnancy.
- Duration
- A few minutes; the exposure lasts a fraction of a second.
- Radiation
- A chest X-ray is about 0.1 mSv, comparable to a few days of natural background radiation; a lumbar spine film is around 1 mSv.
- Contrast
- Barium swallows and enemas coat the gut to outline it on fluoroscopy; iodine contrast is used for joints (arthrogram) and blood vessels (angiography).
- Risks
- The radiation dose is tiny for a single film; the abdomen and pelvis are shielded or avoided in pregnancy unless essential.
Common uses
| Region | Typical question |
|---|---|
| Chest | Cough, breathlessness, chest pain, fever, suspected pneumonia or heart failure |
| Limbs and spine | Injury, joint pain, suspected fracture, osteoarthritis |
| Abdomen | Obstruction, perforation, swallowed objects |
| Bone density | DEXA scanning uses two low-energy X-ray beams to measure bone mineral density for osteoporosis |
Studies this page covers
Named studies of the master test taxonomy that this modality page covers; each links to its test category.