Chest X-Ray Flashcards
What is another term for chest radiograph (hint: think of how invented it)
Roentgenogram
How is the image of the chest radiograph produced
The x-ray beam comes out of the cathode tube passed through the chest to hit the anode film on the other side of the body where it will undergo a physical change to produce an image
What are the four main densities that are seen on a chest x-ray
From darkest (least dense) to lightest (most dense)
- Air
- Fat
- Water and Soft Tissues
- Bone
Air on an X-Ray
The x-ray beam will pass through and no be absorded meaning more of the beam will hit the film and turn the resulting shadow black (radiolucent)
Fat on the x-ray
Fat absorbs a small amount of x-ray beams and will be seen as a light grey
Water and Soft Tissue on X-Ray
Water and soft tissues will absorb a slightly greater amount of x-ray beams and will usually be seen as a medium grey
Bone appearance on x-ray
More of the x-ray will be absorbed in the dense bone leaving the film white (radiopaque)
Magnification on the Chest X-ray
As x-ray beams leave through the x-ray tube, they will scatter out so that they will cover the entire film.
This will lead to the magnification of the shadows on the film when the patient is close to the x-ray source and less magnification when they are farther away
What is the distance that people are exposed to radiation from chest x-rays
The radiation scatter is also important as individuals who are within 6 feet of the x-ray source are exposed to radiation
In order to see different structures on a chest x-ray what needs to happen with the densities of different structures
In order to see different structures on a chest x-ray when they are placed next to another they need to be of different densities
Ex. The soft tissues of the heart are visible because it is surrounded by the lungs which are composed of a lighter density. If the lungs are filled with water such as what happens in pulmonary effusions the normal heart shadow will disappear as it is of a similar density to that of the water
Indications for Chest X-ray
Detecting alterations of the lung caused by pathologic processes
Determining the appropriate therapy
Evaluating the effectiveness of treatment
Determining the position of tubes and catheters
Observing the progression of lung disease
Assessing the patient after an invasive procedure
Limitations of Chest X-ray
A chest x-ray provides a 2-dimensional view of a 3D object this means that if an object is on the same horizontal level it will produce the same shadow on the radiograph whether or not it is inside or outside the body
A chest x-ray can appear normal for a patient in respiratory failure due to a acute pulmonary embolism or a chronic obstructive lung disease
The chest x-ray may lag behind the clinical condition of a patient
Coin Lesions
A coin that is taped on the outside of the chest will produce the same shadow of a lung mass inside the lung, which is why many round shaped lung masses and nodules are called coin lesions
Nipple Shadows
Nipple shadow can cause a concern as they are not easily distinguishable from lesions
Clinical Condition of Pneumonia and chest x-ray
A patient with pneumonia may have a high fever and a cough but abnormalities on the chest x-ray will only appear after 12-24 hours and may also persist for days after resolution of symptoms
Posterior Anterior View (PA)
The patient will be standing or sitting upright where the x-ray beam will move through the patient posterior to anterior to strike the film place against the anterior portion of the chest
The shoulder need to be rotated in order to move the scapula away from the lung fields
The patient should be instructed to take a deep breath and hold it for the picture to be taken on a full inspiration
Anterior Posterior View (AP)
Done through portable machine
The film will be placed behind the patient’s back and x-ray source will be anterior to the patient
What is the Distance between the source of the x-ray and the pt with an AP view
The distance between the patient and the x-ray source is typically 4 feet
Because the source is closer to the patient there is more magnification of the heart and mediastinum compared to a PA view
Why is an AP view difficult to interpret
An AP view is difficult to interpret as it tends to not be centered, is rotated, and either over or underexposed, and not taken on a full inspiration.
There will also be the presence of extrathoracic shadows superimposed on the film such as bedding, gown, ECG leads, and tubing
AP Vs. PA view
With a PA view the patient will have their x-ray done in the radiological department and will be placed a standardized distance away from the x-ray source (6 feet) which will help to maximize the quality of the film
PA view are preferred as the anterior chest is closer to the film which will minimize the magnification of the heart
An AP view will be taken with a portable machine and the x-ray source is closer to the patient with the film behind the patient resulting in a magnification of the heart and an overall decreased quality of film
Oblique View
On a lateral image the shadows of the right and left lung will be superimposed on one another and cannot be distinguished, so for this reason an oblique view is often taken
To take an oblique view you move the patient ~5 degree from a routine lateral or a 45 degree to help localize an abnormality
When taking this view the anterolateral portion of the chest will be against the film
Lateral Decubitus
Similar to a later view but the patient will be laying on their side
If the patient is lying on their right side the view is called a right lateral decubitus and vice-versa
Often done in order to localize fluid and identify pleural effusions
This view is also helpful in the identification of pneumothorax.
What is the minimum amount of fluid that needs to be present for a lateral decubitus view to detect it
50 to 100 mL of pleural fluid can be detected with the lateral decubitus view
What side should the patient lay on when taking a lateral debucbitus view for penumothorax or pleural effusion
Air tends to rise and water tends to fall; therefore, patients with a suspected pneumothorax should be placed on the opposite side for radiologic examination, and patients with suspected pleural fluid should be placed on the same side as the suspected disease.
Expiratory X-Ray
Used to help detect small pneumothorax
As the patient exhales the lung volume will be reduced but the pleural air volume will remain the same so during exhalation the pneumothorax will occupy a greater percentage of thoracic volume and be easier to identify on the x-ray
Also the lung will be denser during expiration and the contrast will allow for the air density within the pleural space to be more easily visualized
Air Cyst Definition
A thin-walled radiolucent area that is surrounded by normal lung tissues
Bleb Definition
Superficial air cyst protruding into the pleura, also known as bulba
Cavity
A radiolucent (dark) area surrounded by a dense tissue (white). A cavity is the main hallmark of a lung abscess.
A fluid level may be seen inside a cavity.
Consolidation Definition
the act of becoming solid
Honeycombing Definition
A coarse reticular (netlike) density.
Commonly seen in pneumoconiosis
Pulmonary Mass Vs. Pulmonary Lesion
Pulmonary Mass: Refers to a lesion that is 6 cm or more in diameter. Commonly used to describe a pulmonary tumor
Pulmonary Nodule:Refers to a lesion that is less than 6 cm in diameter and composed of dense tissue. Also called a solidary pulmonary nodule or coin lesion due to its coin like appearance
What will happen if the patient is rotated in the chest radiograph
There will not be equal pentation in the image and one lung will be darker than the other
The heart and mediastinal structures may appear lager
How to check if a chest x-ray has been rotated
In order to check if an image has been rotated you should look to make sure that the vertebral column is centred between the medial ends of the clavicles and directly behind the trachea shadow, also you should check that the distance between the cost-phrenic angles and the spine are the same on both sides
Exposure Quality
Exposure quality should be assessed by looking at the vertebral column which should be visible up to T6 and should be visible through the cardiac shadow
When the vertebral bodies are easily seen, and the lungs are black there is probably overexposure
When the vertebral bodies are hard to see, and the lung fields are very white there is probably underexposure
Level of Inspiration
Level of inspiration is measured by counting the posterior ribs above the diaphragm
8-10 ribs on a PA view and 5-6 on a AP view indicates a good inspiratory effort
What changes in the radiograph are seen when the x-ray is done on inspiration
When an x-ray is done on expiration the lungs will be denser, hemi-diaphragm elevates, and heart falsely enlarged.
The heart may also be denser (whiter) which may mask abnormalities
Determining Whether You are Looking at a AP or PA view
With a PA view the clavicles are lower compared with AP, there is a decreased magnification in the heart,
With an AP view the clavicles are higher into the apices, the ribs will be more horizontal instead of curves, the heart will be magnified
Bony thorax on Chest X-ray
80-90% of the lung parenchyma will be covered with bone (ribs, clavicles, or thoracic spine) which may obscure abnormalities
The intercostal spaces should be assessed to make sure they are symmetrical and equal
These spaces may be larger in COPD patient due to hyperinflation
Lung Parenchyma on Chest X-ray
Always compare one lung to another
Tissue marking should be seen though all the lung fields
Absence of tissue markings can be the result of pneumothorax, COPD, or a recent pneumonectomy
Increased tissue marking can be the result of fibrosis, edema (alveolar or interstitial), lung compression
Hilum on the chest x-ray
The left hilar region will be ~2cm higher than the right
Vertical displacement of the hilum may indicate volume loss from the upper lobes on the affected side
Increased density of the hilar region can be caused by the engorgement of the hilar vessels which may be the result of an increased pulmonary vascular resistance (PVR)
Large lymph nodes that are located in the hilar region can become enlarged in response to conditions like histoplasmosis and tuberculosis
Pleura on the chest x-ray
The pleural membranes around the lung cannot be seen on a chest radiograph because they blend into the water density of the chest wall, diaphragm, and mediastinum. However, the visceral pleura separating the lobes can be seen if the pleural surface is parallel to the x-ray beam (as with the “minor” or “horizontal” fissure separating the right upper lobe from the right middle lobe on a PA chest x-ray).
Although very thin, the visceral pleura separating the lobes is visible because it is contrasted with aerated lung on either side.
The borders of the lung should be examined for accumulation of air, fluid, lesions, and thickening of the pleura
Diaphragm on the Chest X-ray
Normally, the diaphragm forms a dome that curves downward to attach to the chest wall on the lower ribs and thoracic and lumbar vertebra.
The diaphragm will appear to be lower than expected in COPD or fluid collecting in the pleural space
Hemi Diaphragmon the Chest X-ray
2 hemidiaphragms are visible with the right 2 cm above the left due to the liver
The elevation of a hemidiaphragm may be cause by a collapse of the right middle lobe or lower lobe on the affected side
costophrenic angle
On a chest radiograph, the arch of the diaphragm and the chest wall meet to form a point called the costophrenic angle.
The costophrenic angle is seen on both PA and lateral views. If the point of the costophrenic angle is rounded rather than sharp, it usually indicates that a pleural effusion is present
Gastric Air Bubble
Often will be seen under the left hemidiaphragm
The Heart on a Chest X-ray
Heart
The width of the heart shadow to the thorax is <1/2 (50%) on a standard PA shot of the chest
AP views may have a slightly enlarged heart, but still should not exceed 50%
There are two bulges that should be located on the right cardiac border
The upper bulge is the superior vena cava and the lower the right atrium
Three structures should be located on the left cardiac border, and are (from top to bottom) aorta, main pulmonary artery, and the left ventricle
An enlarged cardiac silhouette may occur with congestive heart failure or with a pericardial effusion
Pneumomediastinum
Pneumomediastinum, a form of barotrauma, may result from movement of air into the mediastinum, as also may be seen in cases of esophageal rupture
This condition usually occurs in the distal portion of the esophagus in patients who undergo procedures to stretch or dilate the esophagus.
Chest trauma may cause rupture of the trachea or a mainstem bronchus, also allowing movement of air into the mediastinum.
Rarely, air dissects down from the soft tissues of the neck after thyroid, parathyroid, or tonsillar surgery.
Gas associated with a retrotonsillar abscess may extend inferiorly into the mediastinum through the fascial planes of the neck.
Air that accumulates in the retroperitoneum may enter the mediastinum via openings in the diaphragm for the aorta or esophagus.
The RT should pay specific attention to areas where subtle abnormalities can be hiding which include
Lung apexes (behind the clavicles)
Area of the lung that projects behind the heart
Portion of the lung that lies deep in the posterior sulcus (extreme bottom of the lung projecting behind the dome of the diaphragm on the font view)
Abnormalities that decrease lung tissue density
such as cavities and blebs, absorb fewer x-rays and result in darker areas on the film.
The heart, diaphragm, and major blood vessels are considered to have the density of ___________
The heart, diaphragm, and major blood vessels are considered to have the density of water.
Water is denser than air, and water densities result in less exposure and therefore whitish-gray shadows on the chest radiograph.
The heart, diaphragm, and major blood vessels rarely alter in density but may change in size, shape, and position.
Evaluation of the shadows produced on the chest radiograph by these structures allows a clear view of any deviation from normal in position or size. It is important to note that the lung shadow on a normal chest radiograph is not uniformly black.
Normal Lung architecture
The pulmonary vessels that are perpendicular to the x-ray plane give round shadows, and the vessels that are parallel to the plane give tubular shadows. So the normal lung will appear “peppered” with dots and lines that represent pulmonary vasculature. This appearance is sometimes called normal lung architecture.
As a result of the absence of the lung vasculature, blebs and the air contained in pneumothorax do not have this particular lung architecture appearance, which makes it easier to distinguish them from the normal lung tissue.
