Chest Anatomy & Radiography

Divisions of Chest Anatomy

• The bony thorax acts as a protective framework.
• The respiratory system includes the lungs and airways.
• The mediastinum is the space between the lungs.

Body Habitus Types

• Hypersthenic body habitus is 5% of the population.
• Sthenic body habitus is 50% of the population.
• Hyposthenic body habitus is 35% of the population.
• Asthenic body habitus is 10% of the population.
• Body habitus impacts radiographic positioning, which is detailed on pages 15-17.
• Body habitus also affects whether a portrait (lengthwise) or landscape (crosswise) image is needed, as discussed on page 17.

Expiration vs. Inspiration

• Inspiration involves increases in three dimensions which include:
  • Vertical diaphragm movement downward
  • Transverse expansion
  • AP dimension

Degree of Inspiration

• A minimum of 10 ribs should be visible on a chest radiograph to ensure adequate inspiration.
• Posterior ribs should be counted to assess the degree of inspiration.

Patient Preparation

• Remove any opaque objects that could interfere with the image.
• Address any clothing artifacts that may be present.
• Ensure long hair is fastened to keep it out of the image field.
• O2 lines and pacemaker leads should not be superimposed over lung fields.

Radiation Protection

• Limit repeat exposures to minimize patient radiation dose.
• Use collimation to restrict the beam to the area of interest.
• Employ gonadal shielding to protect reproductive organs when possible.
• Consider backscatter protection measures for personnel.

Technical Factors

• High kVp (110 to 125) is used for chest radiography.
• A grid is typically utilized to improve image quality.
• High mA and short exposure time settings are used to minimize motion blur.

Patient Identification

• Proper patient identification on the image is crucial.
• Anatomic side markers are used to indicate the left or right side of the patient.
• Situs inversus is a condition where the organs are mirrored from their normal positions.

Breathing Instructions

• Provide clear and concise breathing instructions to the patient.
• The exposure should be made upon the second full breath.
• Ideally, 10 posterior ribs above the diaphragm are visualized with proper inspiration.

Reasons for Erect Chest Position

• It allows the diaphragm to move farther down.
• It demonstrates air-fluid levels.
• It prevents engorgement of pulmonary vessels.

Criteria: No Rotation

• Rotation is evident by asymmetry of the sternoclavicular (SC) joints.

Criteria: Chin Extended

• Having the chin up and extended is important for clear visualization of anatomical structures.

Criteria: Minimize Breast Shadows

• Minimize breast shadows for improved visualization of underlying structures.

Lateral Chest Position

• Place the side of interest closest to the image receptor (IR).
• A left lateral position is commonly used.

Criteria: No Rotation (Lateral)

• Rotation can be identified by lack of superimposition of the posterior ribs.

Criteria: Arms Raised High

• Ensure that the arms are raised sufficiently to avoid superimposition over the lung fields.

Topographic Landmarks for PA Chest

• On average, the vertebra prominens (C7) is located approximately 7 inches (18 cm) from the jugular notch in females.
• It is located approximately 8 inches (20 cm) from the jugular notch in males.
• The jugular notch is typically 3-4 inches (8-10 cm) from the top of the sternum.

Hand Spread Method

• A ruler can be used to determine an individual's hand spread.
• Measure from thumb-to-fifth digit.

Topographic Landmarks for PA Chest

• For a PA chest radiograph, the central ray (CR) is 3-4 inches (8-11 cm) below the jugular notch.

Collimation Guidelines

• Collimation borders above the apex of the lungs should approximately equal collimation borders below the costophrenic angles.

Chest Radiography Projections

• Routine chest projections include PA and lateral views.
• Special chest projections include:
• AP supine or semierect
• Lateral decubitus
• AP lordotic
• Anterior oblique
• Posterior oblique

PA Chest

• The central ray (CR) should be directed to T7.

PA Chest Evaluation Criteria

• Entire lungs are included on the image.
• There must be no rotation.
• Scapulae should be removed from the lung fields.
• There must be full inspiration.
• There should be equal collimation top and bottom.
• There must be no motion.
• Exposure factors should be optimal.

Left Lateral Chest

• The central ray (CR) is directed to T7.
• There must be no rotation.

Left Lateral Chest

• Lower central ray 2.5 cm from PA.

Lateral Chest Evaluation Criteria

• The entire lungs must be included on the image.
• There should be no rotation.
• The chin and arms should be elevated.
• Collimation should be correct.
• There should be no motion.
• Exposure factors should be optimal.

AP Supine or Semierect

• The central ray (CR) should be directed to T7, perpendicular to the sternum.

AP Semierect Evaluation Criteria

• Similar to PA, except the heart may appear larger.
• Air-fluid levels may not be well defined.
• Full inspiration frequently not achieved, resulting in visualization of 8 to 9 ribs.

Left Lateral Decubitus (AP)

• Support should be placed under the lower chest.

Lateral Decubitus Evaluation Criteria

• The entire lungs must be included.
• There should be no rotation.
• Arms should not be superimposed over the lungs.
• Full inspiration is required.
• There should be no motion.
• Exposure factors should be appropriate.

AP Lordotic

• The central ray (CR) is directed horizontally to midsternum.
• The patient is angled in the lordotic position.

AP Semiaxial Lordotic

• The central ray (CR) should be angled 15° to 20° cephalad.

AP Lordotic Evaluation Criteria

• Clavicles should be above the apices of the lungs.
• There should be no rotation.
• There should be no motion.
• Exposure factors should be optimal.

Anterior Oblique

• The patient is positioned in a 45° RAO position.

Anterior Oblique - Thorax Elongation

• With each oblique position, the focus is on which side of the thorax is elongated.
• The Right Anterior Oblique (RAO) positon elongates the right thorax.
• The Left Anterior Oblique (LAO) position elongates the left thorax.

Anterior Oblique Evaluation Criteria

• In the RAO position, the correct side of the thorax (right side) should be elongated.
• For both RAO and LAO, the entire lungs should be included.
• Optimum exposure factors are essential for good image quality in both positions.

Posterior Oblique

• The patient is positioned at 45° LPO.

Posterior Oblique - Thorax Elongation

• The 45° Right Posterior Oblique (RPO) position elongates the right side.

Posterior Oblique Evaluation Criteria

• The 45° LPO elongates the left side.
• RPO, LAO positions show elongation of the right side.
• LPO, RAO positions show elongation of the left side.
• Both lungs should be demonstrated.
• There should not be motion.
• Optimal exposure factors should be selected.

Quiz Answers

• Quiz 1: A. True. The pharynx is a common passageway for food and respiration.
• Quiz 2: A. True. The left bronchus is smaller in diameter than the right but is approximately twice as long.
• Quiz 3: A. Parietal pleura. The outermost layer of the pleura is referred to as the parietal pleura.
• Quiz 5: D. 10. Ten posterior ribs should be seen above the diaphragm for a well-inspired PA chest projection.
• Quiz 6: D. 110 to 125 kVp. The recommended kVp range for an adult chest is 110 to 125 kVp.
• Quiz 7: A. Use Pigg-O-Stat. In a young pediatric patient, in a chest study you should use a Pigg-O-Stat.
• Quiz 8: D. Right lateral decubitus. If the patient cannot stand, the right lateral decubitus projection is the proper position to perform to demonstrate a pleural effusion in the right lung
• Quiz 9: B. Left lateral decubitus. Left lateral decubitus is the proper projection/position to utilize to demonstrate a pneumothorax in the left lung if the patient cannot stand.