Developing skill with radiographic interpretation requires practice. Look at every film for your patients. Practice by looking at normal films, then compare between normal and abnormal. For example, compare an image for a patient with a normal cardiac silhouette and compare it with a patient with an abnormal silhouette with a widened mediastinum.

This is NOT an exhaustive list of everything that can be seen on a chest x-ray, but is an overview of common pathology that can be seen.

How to read a film

1. Identify- correct patient/ date/ time.

2. Identify orientation. Is the projection posterior-anterior (PA) or anterior-posterior (AP)? Is the patient rotated?

• PA is when the patient stands with their chest facing the x-ray cassette and the x-ray is behind the patient, so the x-ray beam travels from the posterior of the patient toward the plate, which is situated on the patients anterior surface.

• AP is when the patient’s back is towards the board and the x-ray is in from front of the patient, so the x-ray beam travels from the anterior of the patient toward the plate, which is situated on the patient’s posterior. This is the orientation when a patient is laying supine in the trauma bay. On an AP film, the heart appears enlarged compared to the PA.

• Rotated- compare bilateral or midline structures, such as clavicles and the spinous processes of the vertebra. If the clavicles are asymmetric or the spinous processes are not midline, the patient is rotated.

Structures (ABCs)

1. Airway

• Is the trachea midline?

• Are there any opacities in the lung fields- pneumonia, masses, bilateral haziness?

• Do the lung markings extend to the edge of the chest?

  • If not, and the space area is dark, this is suggestive of a pneumothorax.

  • In contrast, if the space is white, this is suggestive of a fluid collection (hemothorax, infected fluid, etc).

• Is there evidence of fluid? This depends on the patient’s postion and the consistency of the fluid. Free fluid (fresh hemothorax, pleural effusion) will layer dependently, so if the patient is upright, the costophrenic angles will be blunted. If the patient is supine, the fluid can cause generalized opacity of the lung field because it layers along the back of the patient.

2. Bones- examine for fracture, dislocation, masses (tumor)

• Upper extremity/ shoulder?

• Ribs?

• Vertebra?

3. Cardiac

• Silhouette size/ contour? Normal is <1/2 the size of the thoracic cavity

• Evidence of aortic injury? *Bonus- 3 places for blunt aortic injury- aortic root, diaphragm, and isthmus just past subclavian takeoff

  
  

  • Widened mediastinum (supine >8 cm or upright > 6cm)

  • Loss of aortopulmonary window

  • Abnormal aortic contour

  • Depressed left mainstem bronchus

  • Left apical capping

  • Left hemothorax

  • Nasogastric tube deviation

  • Widened paraspinal or paratracheal stripe

4. Diaphragm

• Elevated- symmetric elevation is consistent with poor inspiratory volume.

• Blunting of costophrenic angle- effusion.

• Abdominal contents in chest (ie gastric bubble in the left chest)- consistent with diaphragm injury or defect.

5. Everything else

• Air in soft tissue- many potential etiologies, but common causes include pneumothorax or esophageal/ airway disruption.

• Air under the diaphragm (pneumoperitoneum)- concerning for hollow viscus injury.

• Iatrogenic foreign bodies- endotracheal tube, central lines, ports, pacemaker, endovascular grafts, esophageal stents, feeding tubes

• Non-iatrogenic foreign bodies- swallowed objects

Additional References and Images from Radiopaedia.org

**Click on Cases and figures and Imaging differential diagnosis on the right-hand column of each page for more in-depth explanations of specific pathology**

1. Radiopaedia

2. Airway

3. Bones and Soft Tissue

4. Cardiac Silhouette and Mediastinum

5. Widened Mediastinum

6. Hemothorax

7. Pneumothorax

8. Nasogastric Tube Position