Chest X-ray: what a chest image shows

A referral for a chest X-ray almost always raises questions: what exactly will be seen on the image, whether it hurts, and why you are sometimes asked to stand sideways. We explain step by step what a chest X-ray shows, why two views are needed, and in which cases one image is not enough.

What a lung and chest X-ray is

Chest radiography is a classic projection study using X-ray radiation. The image shows the lungs, heart, major arteries, ribs, diaphragm, and soft tissues of the chest.

A referral is issued for a specific task. Reasons include:

• a cough that does not go away for a long time;
• chest pain after an injury — with a possible rib fracture — or due to heart problems;
• blood when coughing;
• difficulty breathing;
• elevated temperature.

An image is also taken when tuberculosis, lung cancer, or other chest diseases are suspected, and as a screening method in people with occupational hazards. A series of repeat images helps the doctor monitor changes that were visible last time.

What can be seen on the image

The doctor reads the image detail by detail: looking at the lung fields and their transparency, the lung markings — vascular shadows, the lung roots, the domes of the diaphragm and the sinuses of the pleural cavities, and the shape and size of the mediastinal shadow together with the heart. Most often, radiography is used to diagnose pneumonia and congestive heart failure.

Extra or missing shadow elements are considered abnormal: opacities and lucencies, changes in the transparency of the lung background, impoverished or enriched lung markings. Findings include foci, that is, limited areas of opacity, air cavities, pleural effusion, and diffuse changes of the ground-glass type. Abnormal results occur, for example, with lung collapse, fluid around the lung, pneumonia, or tuberculosis.

The doctor also assesses the airiness of the bronchi — this is an additional sign that helps distinguish lung diseases from mediastinal diseases.

Views: frontal and lateral

Usually two images are taken. First the patient stands facing the machine — this is the frontal view, anterior or posterior, depending on where the detector is located. Then the patient turns sideways — a lateral image, left or right. Two views are usually taken as part of one study.

Sometimes additional positions are needed: lying on the side — to see fluid that moves when position changes; with the back arched — for the lung apices; on exhalation — when pneumothorax is being looked for.

Digital and film image: the difference in dose

The difference is primarily in the dose and in the image carrier. The average individual dose for film chest radiography is about 0.3 mSv, for digital about 0.03 mSv, that is, ten times less. For some diseases radiography is good as a screening method; for others its diagnostic value is insufficient.

How the study is performed

The patient is asked to take a breath and hold it — there is no pain, except perhaps if the plate turns out to be cold. Before the study, pregnancy or the possibility of it is reported: chest X-rays during pregnancy are usually avoided, and if one is still needed, special precautions are taken. Patients are asked to remove anything containing metal: jewelry, a bra, clothing with zippers and snaps.

A medical specialist should explain what is visible on the image and whether further examinations are needed.

Limitations of the method and when CT is needed

X-ray is not an all-seeing glass. A false-negative result occurs if the shadow of a focus overlaps a normal structure — the diaphragm or mediastinum — if the focus itself is of low intensity, as in early inflammation, especially with agranulocytosis, or if an inadequate view is chosen — this is typical for mediastinal pathology and fractures of the ribs and sternum. In such cases, computed tomography becomes the method of choice, as it lacks these drawbacks; bronchoscopy is added if necessary. Radiation exposure during X-ray is small, doses are monitored, and pregnant women and children are more sensitive to the risks.

A referral for an X-ray or a completed image is not in itself a reason to call an ambulance. Call 103 or 112 if the condition is life-threatening: for example, with difficulty breathing, coughing up blood, or severe chest pain after an injury.

This material is for reference: it explains what a chest image shows but does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer