Module 2.7 - The Chest X-ray

Question 1

How are anteroposterior chest x-rays obtained?

Answer 1

• Usually obtained as a portable film with patient in supine position.
• The patient’s back is against the film plate
• Limits attainment of optimal image resulting in limited inspiration and flattening of the posterior of the heart causing the heart to be false widened – up to 15%.

Question 2

How are posteroanterior chest x-rays obtained?

Answer 2

• Usually obtained in the x-ray department, done in upright position.
• Pts chest against the film plate
• Allows for optimal imaging with sharper image, deeper inspiration to show more of the lungs and less distortion of the cardiac silhouette.

Question 3

How are lateral chest x-rays obtained?

Answer 3

• They are done with film against the patient’s left side.
• Useful in evaluating structures in the posterior mediastinal and retro cardiac spaces.
• Also useful in evaluating thoracic vertebrae.
• Free pleural fluid level can be seen if not seen in supine films.

Question 4

How are the differences in x-ray penetration determined?

Answer 4

Sufficient detail in the image is largely determined by the intensity of the x-ray beam.

• Optimal penetration is judged by clarity of the vertebral bodies on the image.
• Over penetration = beam too intense, image is overly dark with subtle details rendered invisible.
• Under penetration = beam insufficiently intense, overly while image, all details are lost in the glare.

Question 5

When should a chest x-ray be taken?

Answer 5

The film should be exposed during a deep inspiration to produce good alveolar inflation and avoid diaphragmatic displacement of the heart. Adequate inspiration= seventh rib is visible at or above the diaphragm. Inadequate inspiration flattens the inferior border of the heart causing the lateral borders to falsely widen.

Question 6

What is an interstitial pattern on a chest x-ray?

Answer 6

Appears as aerated lung with distinct linear or nodular markings. May indicate idiopathic pulmonary fibrosis, radiation pneumonitis or scleroderma.

Question 7

What is an alveolar pattern on a chest x-ray?

Answer 7

An alveolar pattern are cloudy to dense opacities and may be indicative of pulmonary edema, bronchopneumonia, hemorrhage, an atelectasis.

Question 8

How should you approach reading a chest x-ray?

Answer 8

1. Ensure you are looking at the proper film, identify the patient, date and time of the film
2. Examine the film for orientation, rotation and image quality. PA/AP views should be hung as if facing the patient from the front. Clavicles should be of equal length heads astride chest midline. Outline of the separate vertebral bodies should be evident. Compare side by side with previous x-rays. Check for adequate inspiration.
3. Use the ABCDEHI pneumonic

Question 9

What does the ABCDEHI pneumonic stand for when reading chest x-rays?

Answer 9

• Airway – trachea should be midline. A displaced trachea may indicate thyroid enlargement. The right main bronchus is straighter than the left main bronchus. If there is consolidation in the right lower lobe, consider aspiration pneumonia.
• Bones – Include the spine, clavicle, ribs and scapula in your assessment. Anterior ribs look flatter versus posterior ribs – examine each for fractures. Intercostal spaces should be noted for widening or asymmetry – hyperinflation of the lungs or chest wall tumors can cause these findings.
• Circulation or cardiac – Look closely at the mediastinum – if it is widened, it may indicate HF or aortic aneurysm. Calcification is indicative of atherosclerosis. Normal cardiac to thoracic ratio should be less than 50%. The left mediastinal border consists of the brachiocephalic vein, the aortic arch, the pulmonary artery, the atrial appendage and the left ventricle. The right mediastinal border consists of the brachiocephalic vein, the superior vena cava, the ascending aorta, the right pulmonary artery, the right atrium and the inferior vena cava.
• Diaphragm – Right side is normally 1-2 cm higher than the left due to the liver elevating the diaphragm. The costophrenic angles should be sharp. Air under the diaphragm can be indicative of bowel perforation as seen in this example.
• Edges or effusion – examine the edges of the lung and chest wall for subcutaneous emphysema, pneumothorax, hemothorax and pleural effusions.
• Fields – Lung parenchyma is examined for density changes or consolidations
• Gastric bubble – Loss of this could indicate hiatal hernia. Large bubble is consistent with bloating. Air density outside of the gastric bubble and GI tract can indicate pneumoperitoneum.
• Hilum – The hilar is the overlapping of pulmonary arteries and veins with the left hilum 1-2 cm above the right.
• Invasive lines – including tubes, lines, drains, catheters, wires

Question 10

How does CHF manifest on a chest x-ray?

Answer 10

• Often manifests as an enlarged cardiac shadow along with increased pulmonary vascular markings.
• Cardiogenic pulmonary edema can be seen on the chest x-ray as Kerley B Lines (horizontal lines that are less than 2 cm long found near the costophrenic angle of the lungs)
• You may also see pleural effusions with CHF.

Question 11

How does a pericardial effusion manifest on a chest x-ray?

Answer 11

The chest x-ray is not sensitive enough to detect pericardial effusion. If changes in the size of the cardiac silhouette are seen this may suggest an effusion. Serial x-rays would determine resolution or enlargement of the effusion

Question 12

How does emphysema manifest on a chest x-ray?

Answer 12

Pulmonary parenchyma tends to be more lucent than normal reflecting the loss of tissue and hyperinflation. Often the cardiac silhouette appears narrow, the diaphragmatic domes are flattened, and the lung volumes appear larger.

Question 13

How does pneumonia manifest on a chest x-ray?

Answer 13

• A chest x-ray is an essential part of the initial work up when you are evaluating your patient for pneumonia.
• If an infiltrate is seen in a specific area of the lung - suspect pneumonia.
• If a follow up chest x-ray is obtained, improvement in the infiltrate often lags behind improvement in the patient’s clinical status. Often a follow up chest x-ray is not needed if patient improves quickly.

Question 14

What are pulmonary nodules?

Answer 14

• A nodule is defined as a lesion smaller than 3 cm in size
• Larger lesions are referred to as masses
• Nodules should be followed with yearly chest CTs (more frequently if recommended by radiologist)

Question 15

In what type of patients are pulmonary nodules found?

Answer 15

• Benign nodules are often found in nonsmokers younger than 35 years old. They tend to be calcified and do not change over time… Calcifications in benign nodules are typically described as central, laminar diffuse or popcorn on a report. Nodules described as eccentric or stippled these may be benign or malignant. Chest CT scans or positron emission tomography would be indicated to evaluate questionable etiology.
• Persons ages 55-74, are current smokes or who have quit smoking within the past 15 years and/o have a smoking history of 30 pack years should receive lung cancer screening.