Radiographic Techniques of the Thorax: Larynx

Radiographic Techniques of the Thorax: Larynx

• Plain radiography is used to locate soft tissue swellings, assess their effects, and identify foreign bodies or laryngeal trauma.
• Tomography, CT, and MRI may be used for a full evaluation of disease processes.
• Two projections are typically taken, an anteroposterior (AP) and a lateral.

Anteroposterior (AP) Projection (Fig. 7.1a)

• Patient lies supine with the median sagittal plane aligned with the central long axis of the couch.
• Chin is raised to show soft tissues below the mandible.
• Image receptor is centered at the level of the 4th cervical vertebra.
• X-ray beam is directed 10° cranially and centered in the midline at the level of the 4th cervical vertebra.
• Beam is collimated to include the area from the occipital bone to the 7th cervical vertebra.

Lateral Projection (Fig. 7.2a)

• Patient stands or sits with a shoulder against the cassette or Bucky.
• Median sagittal plane of the trunk and head are parallel to the image receptor.
• Jaw is raised slightly to separate the angles of the mandible from the upper cervical vertebrae.
• A point 2 cm posterior to the angle of the mandible should align with the vertical central line of the image receptor.
• The image receptor is centered at the level of the thyroid cartilage.
• Before exposure, the patient depresses their shoulders to project structures below the 7th cervical vertebra.
• Exposure is made on forced expiration.
• Collimated horizontal central ray is centered below the mastoid process at the level of the thyroid cartilage through the 4th cervical vertebra.
• Soft tissues should be demonstrated from the skull base to C7 to clearly visualize the laryngeal cartilages and possible foreign bodies.

Lungs

• Radiographic examination of the lungs is used to assess a wide range of medical conditions, including primary lung disease and pulmonary effects of other diseases.
• Changes in lung parenchyma appearance may vary based on the disease's nature and extent.

Positioning

• Erect or decubitus positioning is chosen based on the patient's condition.
• Most patients are positioned erect; immobile or severely ill patients are positioned supine or semi-erect.
• Erect positioning simplifies the procedure due to the gravitational effects on abdominal organs, allowing better visualization of the lung tissue and fluid levels, especially when using a horizontal central ray.

Posteroanterior (PA) Projection

• The PA projection is favored over AP due to easier arm positioning, resulting in a reduced heart magnification, and reduction in breast tissue compression.
• The mediastinum and heart shadows may obscure parts of the lung fields, making a lateral radiograph sometimes necessary.

Respiration

• Images are acquired during arrested deep inspiration to visualize air-filled lungs.
• AP magnification makes assessing heart size and apical region difficult, as well as the mediastinum.

Exposure

• Overexposure reduces the visibility of lung parenchymal details and hides consolidations.
• Underexposure can falsely highlight normal markings as disease.
• Inadequate exposure may obscure central areas and potentially hinder the diagnosis of mediastinal abnormalities.

Soft-tissue Artifacts

• Soft tissue artifacts can cause misinterpretations.
• The normal nipple, skin lesions, and breast tissue/masses can mimic lung lesions.
• Clothing folds and creases (especially in thin patients) can create linear artifacts.

Radiographic Anatomy

• Lungs are positioned in the thoracic cavity on either side of the mediastinum.
• The diaphragm separates the lungs from the abdomen.
• The right lung is larger than the left due to heart position.
• Rib, clavicle, and heart positions obscure certain lung tissue on the PA radiograph, but other projections can showcase more.
• The right and left lungs are divided into upper, middle, and lower lobes, separated by fissures that are most visible in PA radiographs when parallel with the beam.

Trachea and Bronchi

• The trachea is centrally located in the upper chest, splitting into the right and left main bronchi at the 4th thoracic vertebra.
• The right main bronchus is wider and more vertical than the left, influencing foreign body inhalation.
• Bronchi subdivide into progressively smaller bronchioles, then alveolar air spaces, increasing in density.
• Hilar regions (the points where the pulmonary arteries and veins branch) present as areas of increased radio-opacity.
• Lung markings are a visualization of the pulmonary vessels, and decrease in size as they branch away from the hilum.

Patient Preparation and Notes

• Patient preparation is crucial by removing any radiopaque items and ensuring proper positioning.
• Patients with chest tubes/underwater-sealed bottles require careful handling to prevent displacement; the bottle should not be placed above chest level.
• PA side markers are used for accurate image identification. Misidentification of cases like dextrocardia needs care.
• Long hair should be removed from the image area.

This quiz focuses on the radiographic techniques used for evaluating the larynx, including plain radiography, tomography, CT, and MRI. It details the procedures for anteroposterior and lateral projections, including patient positioning and beam alignment. Test your knowledge on essential imaging techniques for laryngeal assessment.