Chest Xray Interpretation Flashcards
How does an Xray work
A beam of ionizing radiation diverges from its source and travels in a straight line passing through the anatomical structure and terminating on the detector.
what does the result of an Xray depend on
the DENSITY of the structures
Depending on the density of the anatomical structure the beam will be absorbed in a variation of degree or be scattered (in the case of metal)
describe the density of bone, air, soft tissue, fat and metal
the order of these in least density to most density is shown below. therefore the material with the least density (air) appears black, whereas the most density (metal) appears white
What causes structures to be magnified? why is this important
structures that the beam hits first (the structures closest to the beam) will be magnified since they are farther from the detector.
this is what causes the difference in Posterior-Anterior CXR and Anterior-Posterior CXR
what is the main difference in PA CXR and AP CXR
in AP CXR the heart will be magnified since it is closer to the source of the beam and father from the detector. This makes the heart appear larger
what are common reasons that CXR are ordered
- Persistent cough
- Shortness of breath
- Wheezing
- Chest pain/injury
- Fever (unexplained)
- Monitoring of disease resolution or progression
- Lymphadenopathy (unexplained)
what is the patient preparation for CXR
- remove clothes, undergarments, all metal
- LMP/pregnancy test (females only, usually if its been greater than 3-4 weeks since LMP get pregnancy test)
what are the possible views for a CXR? What is contained in the standard 2 view CXR?
Posterior-Anterior (PA)
Lateral
Lateral Decubitus
Expiratory
Lordotic
Anterior-Posterior (AP)
standard 2 view = PA and lateral
what is the PA view
performed with the chest against the detector
what is the lateral view
performed with the left side of the body against the detector
when is lateral decubitus CXR view indicated
- pleural effusions vs consolidation
- loculated effusions vs free pleural fluid
- evaluate for small pneumothorax
what is the positioning for the lateral decubitus view for a suspected pleural effusion
the side of interest should be down because fluid travels down
what is the positioning for the lateral decubitus view for a suspected pneumothorax
the side of interest should be up because air travels up
A 56-year-old male presents with complaints of chest pain and shortness of breath that was sudden in onset 1 hour ago. Initial PA CXR shows is suspicious for a small right pneumothorax vs artifact.
What would be the most appropriate follow up x-ray you would want to order?
Left lateral decubitus position
when do we order an expiratory CXR view
- air trapping d/t a foreign body (food stuck in lung)
- small pneumothoraces
what is the abnormal side of this expiratory CXR view
the right side because it is bigger. this means the right side is not able to exhale as much air which indicates a foreign body in the bronchus.
what is a lordotic view
using a different angle to further evaluate structures that are superimposed and inhibiting view
when is a lordotic view indicated
to evaluate lung apices that appear obscured on the PA/AP.
(example: when you see something that may be an abnormality but you are unsure if it is a part of the superimpossed bone over the lung, or if it is a problem with the lung itself so you order a lordodic view)
when would you order an AP view CXR
for patients who cannot stand erect. this view is taken supine or sitting.
what is the differences between PA view and AP view
Why does the anatomy appear in the same position despite the way the image was captured in PA vs AP?
they rotate the image so that it always appears as if the patient is looking at you. In every xray image you see, it will be as if the patient is facing you
A 42-year-old female presents with complaints of cough and shortness of breath that was has progressively worsened over the last week. Initial x-ray shows a blunted costophrenic angle on the left. The radiologist is concerned about a pleural effusion.
What would be the most appropriate follow up x-ray you would want to order?
Order a CXR with Left lateral decubitus view.
gravity should pull the fluid down to confirm pleural effusion.
what are the 4 systematic steps to interpreting a CXR
- ensure basic information ( ID the patient and make sure its the right patient!)
- ensure its an adequate quality CXR.
- Interpret the CXR
- Always compare the CXR to past x rays.
what are things to look for to ensure a CXR is of good quality
- penetration
- Artifact
- Inclusion
- Rotation
what is penetration
the degree to which X-rays have passed through the body.
how will an adequately penetrated image present.
- Vertebrae are slightly visible behind the heart
- Left hemidiaphragm should be visible to the edge of the spine
what are the two types of artifact
radiologic and patient.
what are the possible radiologic sources of artifact
- Abnormal rotation of patient
- Incomplete inspiration
- Incorrect penetration
what are the possible patient sources of artifact
- Poor cooperation of patient
- Movement
- Clothing, hair, jewelry
- Metal or implants in the body
- Skin folds
- Adipose or breast tissue
what are the 4 parts of inclusion when considering quality of a CXR
- 5-7 Anterior Ribs (angled (PA))
- 10 Posterior Ribs (horizontal (PA))
- Costophrenic Angles
- Lateral edges of Ribs
what is considered in the rotation portion of quality check for a CXR
- Spinous processes of the thoracic vertebrae should be at the midline of the posterior chest
- The medial ends of the clavicles should form a vertical line and should be equidistant from the midline
what is the pneumonic used for interpretation of a CXR
ABCDEGH
Airway
Bones
Circulation
Diaphragm
Extra features
Gastric bubble/free air
Hilum
What is included in the “airway” portion of the interpretation
Trachea
bronchi
lung parenchyma
How should the trachea and bronchi appear in a CXR
- Contains air so lower density than surrounding structures resulting in a darker gray structure
- Trachea should be midline, straight and branches off to R/L mainstem bronchus at the carina
what are the zones of the lungs
upper, middle and lower. split into thirds.
how should lung parenchyma be assessed in a CXR
Inspection should be in a right-to-left pattern moving from the apex to the lung bases
-always compare R/L
-note asymmetries.
what are the lobes of the lungs
the left lung has 2 longes (upper and lower)
the right lung has 3 lobes (upper, middle, lower)
what are the fissures of the lunsg
oblique/major fissure - pleural covering separating the lower lobe from upper lobes in both lungs
Horizontal fissure - separates the R middle from upper lobe
what bones are visible on a CXR
Clavicles
ribs
scapulae
proximal humerus
vertebra
what is the significance of the ribs in a CXR, why are they always assessed and visualized.
their pathology affects adequacy of inspiration.
what diseases should be assessed when looking at bones on a CXR
- fracture
- arthritic changes
- dislocation
- metastatic pathology
what is considered in the “circulation” portion of the CXR interpretation
Heart size
mediastinum
How is heart size determined on a CXR
in relation to total thoracic width.
AKA cardiothoracic ratio which is -
Cardiac width: thoracic width
when should cardiothoracic ratio NOT be used
when you are not using a PA view
what is normal cardiothoracic ratio
Cardiac width < 50% of the total thoracic width
what are mediastinal contours
the borders of the heart and great vessels as well as the spaces in front and behind the heart.
How should borders appear on a CXR
SHARP
what are the compartments of the mediastinum
the superior, posterior, middle and anterior mediastinum
why are compartments evaluated on a CXR
knowing the compartments allows us to narrow a differential diagnosis when there is a mediastinal mass
what does the diaphragm separate
the thoracic cavity from abdominal cavity
what is a normal appearance of the diaphragm
rounded, domed structure with a crisp white edge contrasted against the adjacent dark lung.
often the right diaphragm will be slightly higher than the left
Does the diaphragm in this image appear abnormal?
no, the right side of the diaphragm sits higher than the left. This is because the liver is on the right side.
what are teh costophrenic angles?
angles formed by the hemidiaphragms and the chest wall.
what is a normal costophrenic angle? what is the term for abnormal costophrenic angles?
CPA should be <30 degrees
if CPA is over 30 degrees its called “costophrenic blunting”
what are cardiophrenic angle
formed by the diaphragm and the heart
which side has costophrenic blunting?
right side!
when should you see the pleural spaces on a CXR
NEVER in a normal CXR
the only time is when there is AIR or FLUID in the pleural space.
this picture shows fluid in the pleural space
what is shown in this picture
a collapsed left lung. the left side has a darker appearance suggesting that there is air in the pleural space.
what are extra features you should assess in a CXR
medical equiptment
breasts
nipple markings
pseudo-blunting of CPAs d/t rotation or large pendulous breasts
How common are gastric air bubbles in normal CXRs?
present in 70% of CXRs!
what does free air under the diaphragm suggest
indicative of perforated intestinal organ
what are the structures contained within the hilum
major bronchi and pulmonary vessels
is the left or right hilum higher up?
left
what is consolidation
a solidification of lung tissue with liquid or solid material that normally contains gas (air)
what are possible etiologies of consolidation?
- atelectasis
- infection/exudate
- pulmonary edema
- inflammatory exudate
- inhaled water
- blood
- tumor
what is hyperexpansion
aka hyperinflation
an excessive amount of gas trapped in the alveoli of the lungs over a long period of time
How will hyperexpanded or hyperinflated lungs present
lungs appear elongated and diaphragm is flattened
what is the pathophysiology of hyperexpansion
loss of elasticity preventing expulsion of air
what is the MC cause of Hyperexpansion
COPD
what are etiologies of CPA blunting
- pleural effusion - MC
- pleural abscess
- hemothorax
- pulmonary embolism
- other lung disease in the lateral base of the lung
what is pulmonary edema
a collection of fluid in the alveoli of the lungs preventing adequate air exchange
what are the possible etiologies of pulmonary edema
- Cardiogenic pulmonary edema - MC
- Acute respiratory distress syndrome (ARDS)¹
- Neurogenic pulmonary edema (NPE)²
- Adverse drug reaction
- Pulmonary embolism
- Viral infections
- Lung injury
what is air bronchogram
a tubular outline of an airway made visible by filling of the surrounding alveoli by fluid or inflammatory exudates
what are the etiologies of air bronchogram
- lung consolidation
- pulmonary edema
- non-obstructive pulmonary atelectasis
- severe interstitial disease
- neoplasm
- normal expiration
what is a pneumothorax
collapsed lung
occurs when air leaks into the pleural space
what are possible causes of pneumothorax
- idiopathic
- chest wall trauma
- lung disease
- ruptured blebs
- mechanical ventilation
what is a pleural effusion
excess fluid building in the pleural space.
what are etiologies of pleural effusion
- Congestive heart failure
- Kidney failure
- Infection
- Malignancy
- Pulmonary embolism
- Hypoalbuminemia
- Cirrhosis
- Trauma
what is cardiomegaly
an abnormal enlargement of the heart
what are etiologies of cardiomegaly
- hypertension
- valvular disease
- cardiomyopathy
- pulmonary hypertension
- pulmonary effusion
- anemia
- thyroid dysfunction
- hemochromatosis (iron excess * deposits in heart muscle)
- amyloidosis (abnormal proteins build up in heart muscle)
what are septal “kerley” lines
Lung markings seen on imaging that represent thickened interlobular septa in the pulmonary interstitium
what are kerley A lines
2-6 cm oblique lines that course toward the hila
what are kerley B lines
1-2 cm horizontal seen in the periphery of the lungs (perpendicular to the pleural surface)
what are Kerley C lines
same as Kerley B but coursing ventrally
what are Kerley D lines
same as Kerley B but seen on the lateral CXR in the retrosternal air space
what are possible causes of Septal “Kerley” lines
- pulmonary edema
- malignant lymphoma
- viral/mycoplasmal pneumonia
- pulmonary fibrosis
- pneumoconiosis
- sarcoidosis
what is mediastinal widening
an enlargement of mediastinal structures such as heart, cardiac vessels and other organs including:
esophagus
trachea
phrenic and cardiac nerves
the thoracic duct
thymus
lymph nodes of the central chest
Interpret this CXR
Note that this is an upright AP (top right corner)
left lung pneumothorax
Air in the pleural space on the left
no gastric air bubble
interperet this CXR
This appears to be a female due to seeing lines indicating breasts.
increase in tissue density in the right lung AKA right lung consolidation in the middle zone. Likely pneumonia.
interpret this CXR
multiple sources of artifact present.
pulmonary edema bilaterally
large gastric bubble on left side
interpret this CXR
appears to be in AP due to the angle of the clavicles.
very poor quality image.
blunting of costophrenic angles worse on right than left with possible pleural effusion.
no gastric air bubble or free air.
interpret this CXR
Kerley Lines present
no free air.
Flattened Diaphragm indicating posible COPD
