Normal chest x ray

A self explanatory presentation which gives you the basics of interpreting a normal chest X-ray

1. Normal X-ray Dr. Kaustubh Mohite

2. Before starting reading an X-ray….. Patient identification details. Confirming the view (PA, AP, Lateral). Breath (Inspiration or Expiration). Penetration (Under or Over-exposed). Rotation.

3. Views PA AP

4. Views PA: Standard position. Patient stands upright with anterior wall of chest placed against the front of the film. Shoulders are rotated forwards, ensuring that the scapula does not obscure the lung fields. Taken on full inspiration. Clavicle projects over lung fields. Posterior ribs are more distinct. AP: Used in debilitated, immobilized or non co-operative patients. Film in behind the patient’s back in supine position. Heart is at a greater distance from the film and hence appears magnified. Scapula is seen over lung fields. Clavicle appears above the apex of lung fields. Anterior ribs are more prominent.

5. Other positions: Lateral: Patient stands with the left side of the chest against the film and arms raised over the head. Allows the viewer to see behind the heart and diaphragmatic dome. Done in conjunction with PA view of the same side of the chest to help determine the 3D position of organs or abnormal densities.

6. Lateral Decubitus: Patient lies on either the right or left side. Radiograph is labeled according to the side that is placed down. Useful in revealing a pleural effusion that cannot be easily observed in an upright view.

7. Breath Inspiration 6 anterior ribs visible 10 posterior ribs visible Expiration

8. Penetration: Underexposure: Cardiac shadow is opaque, with little or no visible thoracic vertebra. Lungs appear much denser and whiter, giving appearance of infiltrates. Overexposure: Heart becomes more radiolucent and lungs become proportionately darker. Appearance of lacking lung tissue, as seen in conditions like emphysema

9. Things to be seen in a normal Chest X-ray…. Trachea and major bronchi. Hilar structures. Lung Zones. Pleura and pleural spaces. Diaphragm. Costophrenic recesses and angles Heart size and contours. Mediastinal contours. Soft tissues. Bones.

10. To keep it simple…… A – Airway B – Bones and Soft tissue C – Cardia D – Diaphragm E – Effusions F – Fields (Lung Fields) G – Gastric Bubble H – Hila and Mediastinum

11. Visible Structures: 1 – Trachea 2 – Hilum 3 – Lung 4 – Diaphragm 5 – Heart 6 – Aortic knuckle 7 – Ribs 8 – Scapulae 9 – Breast 10 – Bowel gas Invisible Structures: Sternum Oesophagus Spine Pleura Fissures Aorta

12. Trachea and Major Bronchi: Start your assessment of every chest X-ray by looking at the airways. The trachea should be central or slightly to the right at the level of the aortic knuckle. If the trachea is deviated, it is important to establish if this is because of patient rotation or if it is due to pathology. If the trachea is genuinely deviated you should then try to decide if it has been pushed or pulled by a disease process.

13. Hilar structures: Each hilar point is the angle formed where the upper and lower lobe pulmonary vessels meet. They are useful points of reference to determine the position of the hila. Commonly the left hilum is higher than the right

14. Pulmonary Arteries: Deoxygenated blood ( blue arrows ) is pumped upwards out of the right ventricle ( RV ) via the main pulmonary artery ( Main PA ). The main PA divides into left pulmonary artery ( Left PA ) and right pulmonary artery ( Right PA ) which pass into the lungs via the hila. The left PA hooks backwards over the left main bronchus. The right PA passes anterior to the right main bronchus.

15. Lung Zones: Note that the lower zones reach below the diaphragm ( dotted white line ) – the lungs pass behind the dome of the diaphragm into the posterior sulcus of each hemithorax ( asterisks )

16. Pleura and pleural spaces: Trace round the entire edge of the lung where pleural abnormalities are more readily seen. Start and end at the hila.

17. Lung Lobes and fissures:

18. Found normally in 1 – 2% individuals. Azygos vein passes horizontally along the right side of the mediastinum. In those with an azygos fissure a small section of the right upper lobe (an azygos lobe) develops medial to the vein which is pushed away from the mediastinum. It is surrounded by both parietal and visceral pleura. Four layers of pleura, two parietal layers and two visceral layers. The appearance resembles a tadpole - the head is the azygos vein and the tail the azygos fissure.

19. Diaphragm: The right hemidiaphragm is slightly higher than the left. The liver is located inferior to the right hemidiaphragm. The stomach and spleen are located inferior to the left hemidiaphragm. Lung markings are visible below the diaphragm on both sides – most clearly through the stomach bubble. The cardio-phrenic angles ( asterisks ) are the points at which the hemidiaphragms meet the heart. On both sides, the contour of the hemidiaphragm ( dotted line ) should be seen passing medially as far as the spine.

20. Costophrenic recesses and angles: The costophrenic recesses are seen on each side as the costophrenic angles. The costophrenic angles are formed by the lateral chest wall and the dome of each hemidiaphragm.

21. Heart Size and Contours: The left heart contour ( red line ) consists of the left lateral border of the Left Ventricle ( LV ). The right heart contour is the right lateral border of the Right Atrium ( RA ).

22. Cardio – Thoracic ratio: Cardiac size is measured by drawing vertical parallel lines down the most lateral points of the heart and measuring between them. Thoracic width is measured by drawing vertical parallel lines down the inner aspect of the widest points of the rib cage, and measuring between them. The cardio-thoracic ratio can then be calculated. Here the CTR is approximately 15 : 33 (cm) and is therefore within the normal limit of 50%.

23. Mediastinal Contours: The aortic knuckle represents the left lateral edge of the aorta as it arches backwards over the left main bronchus. The contour of the descending thoracic aorta can be seen in continuation from the aortic knuckle. Displacement or loss of definition of these contours can indicate diseases such as aortic aneurysm or adjacent lung consolidation.

24. Normal Aorto-pulmonary window: The aortopulmonary window is located between the Aortic Knuckle ( AK ) and the Left Pulmonary Artery ( LPA ). It is a space where abnormal enlargement of mediastinal lymph nodes can be seen on a chest X-ray.

25. Bones: Clavicle / Ribs: Act as landmarks Less than 5 ribs indicates incomplete inspiration. More than 7 ribs suggests lung hyper-expansion. Anterior end of the 7th rib ( asterisk ) intersects the diaphragm at the mid-clavicular line. The subcostal grooves are visible on the underside of the ribs ( red highlights ). The spine can be seen through the heart indicating adequate X-ray penetration.

26. Take home points…. Do not forget the pre-requisites before you start to read a chest X-ray. Always have a systematic approach while interpreting an X-ray making sure that you have seen all the components as mentioned above. Always focus more on the prominent observations rather than commenting over the rare abnormalities. The more the number of normal X-rays you see, the easier it is to find out abnormal X-rays.

27. Thank you….