DRSABCDE of CXR Interpretation • LITFL • Examination Medicine

Chest X-Rays (CXR) are routine investigation in clinical practice and consequently it is important for medical students and clinician’s alike to know how to interpret them. There are many approaches to CXR interpretation, each trying to ensure that key abnormalities are identified and no area is overlooked. Many people would be familiar with the ABC method to interpreting CXRs.

This is a simple way of approaching CXR, and it works for many people, however some people still struggle using this approach. DRSABCD is a familiar acronym for those who have undertaken First Aid/Basic Life Support courses. Now DRSABCDE can used as a simple, yet comprehensive, approach to CXR interpretation.

D – Details

DETAILS

Before you even begin interpreting a CXR you should have the correct details. This includes;

• Patient name, age / DOB, sex
• Type of film – PA or AP, erect or supine, correct L/R marker, inspiratory/expiratory series
• Date and time of study

R – RIPE (assessing the image quality)

RIPE

Next up, how “ripe” is the image. That is, what is the technical quality of the film?

• Rotation – medial clavicle ends equidistant from spinous process
• Inspiration – 5-6 anterior ribs in MCL or 8-10 posterior ribs above diaphragm, poor inspiration?, hyperexpanded?
• Picture – straight vs oblique, entire lung fields, scapulae outside lung fields, angulation (ie ’tilt’ in vertical plane)
• Exposure (Penetration) – IV disc spaces, spinous processes to ~T4, L) hemidiaphragm visible through cardiac shadow.

S – Soft tissues and bones

SOFT TISSUES/BONES

In CXR interpretation it is common to leave soft tissues until the end.

• Ribs, sternum, spine, clavicles – symmetry, fractures, dislocations, lytic lesions, density
• Soft tissues – looking for symmetry, swelling, loss of tissue planes, subcutaneous air, masses
• Breast shadows
• Calcification – great vessels, carotids

A – Airway & mediastinum

AIRWAY

• Trachea – central or slightly to right lung as crosses aortic arch
• Paratracheal/mediastinal masses or adenopathy
• Carina & RMB/LMB
• Mediastinal width <8cm on PA film
• Aortic knob
• Hilum – T6-7 IV disc level, left hilum is usually higher (2cm) and squarer than the V-shaped right hilum.
• Check vessels, calcification.

B – Breathing

BREATHING

Lung Fields:

• Vascularity – to ~2cm of pleural surface (~3cm in apices), vessels in bases > apices
• Pneumothorax – don’t forget apices
• Lung field outlines – abnormal opacity/lucency, atelectasis, collapse, consolidation, bullae
• Horizontal fissure on Right Lung
• Pulmonary infiltrates – interstitial vs alveolar pattern
• Coin lesions
• Cavitary lesions

Pleura

• Pleural reflections
• Pleural thickening

C – Circulation

CIRCULATION

• Heart position –⅔ to left, ⅓ to right
• Heart size – measure cardiothoracic ratio on PA film (normal <0.5)
• Heart borders – R) border is R) atrium, L) border is L) ventricle & atrium
• Heart shape
• Aortic stripe

D – Diaphragm

DIAPHRAGM

• Hemidiaphragm levels – Right Lung higher than Left Lung (~2. 5cm / 1 intercostal space)
• Diaphragm shape/contour
• Cardiophrenic and costophrenic angles – clear and sharp
• Gastric bubble / colonic air
• Subdiaphragmatic air (pneumoperitoneum)

EXTRAS

• ETT, CVP line, NG tube, PA catheters
• ECG electrodes, PICC line, chest tube
• PPM, AIDC, metalwork

Further Reading

• Labelled normal Chest X-ray
• ABC of CXR Interpretation
• Top 150 CXR Quiz
• Chest X-ray for the OSCE
• Dr Eric Strong Vodcast series on CXR Interpretation

Fraser Brims

Prof Fraser Brims Curtin Medical School, acute and respiratory medicine specialist, immediate care in sport doc, ex-Royal Navy, academic| Top 100 CXR | Google Scholar | ICIS Course ANZ

How to Read a Chest X-ray – A Step By Step Approach

Author(s): Dr Stephan Voigt, Consultant Radiologist

This article is an attempt
to give the reader guidance how to read a chest Xray and below are two methods. There is no perfect way
to read an x-ray. However, the important message I would like to give is, to
adopt one or the other approach, and to use the chosen approach consistently.

On all Xrays check the following:

• Check patient details
  • First name, surname, date of birth.

• Check orientation, position and side description
  • Left, right, erect, ap, pa, supine, prone

• Check additional information
  •  inspiration,
    expiration

• Check for rotation
  • measure the distance from the medial end of each clavicle to
    the spinous process of the vertebra at the same level, which should be equal

• Check adequacy of inspiration
  • Nine pairs of ribs should be seen posteriorly in order to
    consider a chest x-ray adequate in terms of inspiration

• Check penetration
  • one should barely see the thoracic vertebrae behind the heart

• Check exposure
  • One needs to be able to identify both costophrenic angles and
    lung apices

Specific Radiological Check List:

A – Airway

• Ensure trachea is visible and in midline
  • Trachea gets pushed away from abnormality, eg pleural
    effusion or tension pneumothorax
  • Trachea gets pulled towards abnormality, eg atelectasis
  • Trachea normally narrows at the vocal cords
  • View the carina, angle should be between 60 –100 degrees
  • Beware of things that may increase this angle, eg left atrial
    enlargement, lymph node enlargement and left upper lobe atelectasis
  • Follow out both main stem bronchi
  • Check for tubes, pacemaker, wires, lines foreign bodies etc
  • If an endotracheal tube is in place, check the positioning,
    the distal tip of the tube should be 3-4cm above the carina

• Check for a widened mediastinum
  • Mass lesions (eg tumour, lymph nodes)
  • Inflammation (eg mediastinitis, granulomatous inflammation)
  • Trauma and dissection (eg haematoma, aneurysm of the major
    mediastinal vessels)

B – Bones

• Check for fractures, dislocation, subluxation, osteoblastic
  or osteolytic lesions in clavicles, ribs, thoracic

• Spine and humerus including osteoarthritic changes

• At this time also check the soft tissues for subcutaneous
  air, foreign bodies and surgical clips

• Caution with nipple shadows, which may mimic intrapulmonary
  nodules
  • compare side to side, if on both sides the “nodules” in
    question are in the same position, then they are likely to be due to nipple
    shadows

C – Cardiac

• Check heart size and heart borders
  • Appropriate or blunted
  • Thin rim of air around the heart, think of pneumomediastinum

• Check aorta
  • Widening, tortuosity, calcification

• Check heart valves
  • Calcification, valve replacements

• Check SVC, IVC, azygos vein
  • Widening, tortuosity

D – Diaphragm

• Right hemidiaphragm
  • Should be higher than the left
  • If much higher, think of effusion, lobar collapse,
    diaphragmatic paralysis
  • If you cannot see parts of the diaphragm, consider infiltrate
    or effusion

• If film is taken in erect or upright position you may see
  free air under the diaphragm if intra-abdominal perforation is present

E – Effusion

• Effusions
  • Look for blunting of the costophrenic angle
  • Identify the major fissures, if you can see them more obvious
    than usual, then this could mean that fluid is tracking along the fissure

• Check out the pleura
  • Thickening, loculations, calcifications and pneumothorax

F – Fields (Lungfields)

• Check for infiltrates
  • Identify the location of infiltrates by use of known
    radiological phenomena, eg loss of heart borders or of the contour of the
    diaphragm
  • Remember that right middle lobe abuts the heart, but the
    right lower lobe does not
  • The lingula abuts the left side of the heart

• Identify the pattern of infiltration
  • Interstitial pattern (reticular) versus alveolar (patchy or
    nodular) pattern
  • Lobar collapse
  • Look for air bronchograms, tram tracking, nodules, Kerley B
    lines
  • Pay attention to the apices

• Check for granulomas, tumour and pneumothorax

G – Gastric Air Bubble

• Check correct position

• Beware of hiatus hernia

• Look for fee air

• Look for bowel loops between diaphragm and liver

H – Hilum

• Check the position and size bilaterally

• Enlarged lymph nodes

• Calcified nodules

• Mass lesions

• Pulmonary arteries, if greater than 1. 5cm think about
  possible causes of enlargement

Extended Radiological Check List – Lateral Film:

A – Airway

• Ensure trachea is visible and in midline
  • Trachea gets pushed away from abnormality, eg pleural
    effusion or tension pneumothorax
  • Trachea gets pulled towards abnormality, eg atelectasis
  • Trachea normally narrows at the vocal cords
  • View the carina, angle should be between 60 –100 degrees
  • Beware of things that may increase this angle, eg left atrial
    enlargement, lymph node enlargement and left upper lobe atelectasis
  • Follow out both main stem bronchi
  • Check for tubes, pacemaker, wires, lines foreign bodies etc
  • If an endotracheal tube is in place, check the positioning,
    the distal tip of the tube should be 3-4cm above the carina

• Check for a widened mediastinum
  • Mass lesions (eg tumour, lymph nodes)
  • Inflammation (eg mediastinitis, granulomatous inflammation)
  • Trauma and dissection (eg haematoma, aneurysm of the major
    mediastinal vessels)

B – Bones

• Check the vertebral bodies and the sternum for fractures or
  other osteolytic changes

C – Cardiac

• Check for enlargement of the right ventricle and right atrium
  (retrosternal and retrocardiac spaces)

• Trace the aorta

D – Diaphragm

• Check for fluid tracking up, costophrenic blunting and the
  associated hemidiaphragm

E – Effusions

• Check to see the fissures here as well – both major fissures
  and the horizontal may be found in the lateral view

F – Fields

• Check the translucency of the thoracic vertebrae in the
  lateral view, when there is a sudden change in transparency, then this is
  likely to be caused by infiltrate

• Also try to find the infiltrate that you think you saw on the
  pa-film to verify existence and anatomical location

• Pay special attention to the lower lung lobes

I would like to close with a
clarification of two important radiological findings, whose understanding is
very useful for a correct interpretation of chest x-ray findings.

The first is the silhouette sign, which can localise
abnormalities on a pa-film without need for a lateral view. The loss of clarity
of a structure, such as the hemidiaphragm or heart border, suggests that there
is adjacent soft tissue shadowing, such as consolidated lung, even when the
abnormality itself is not clearly visualised. The reason is, that borders,
outlines and edges seen on plain radiographs depend on the presence of two
adjacent areas of different density, Roughly speaking, only four different
densities are detectable on plain films; air, fat, soft tissue and calcium
(five if you include contrast such as barium). If two soft tissue densities lie
adjacent, then they will not be visible separately (eg the left and right
ventricles). If, however, they are separated by air, the boundaries of both
will be seen.  

The second important x-ray
finding is the lung collapse. A
collapse usually occurs due to proximal occlusion of a bronchus, causing
subsequently a loss of aeration. The remaining air is gradually absorbed, and
the lung loses volume. Proximal stenosing bronchogenic carcinoma, mucous
plugging, fluid retention in major airways, inhaled foreign body or malposition
of an endotracheal tube are the most common reasons for a lung collapse.
Tracheal displacement or mediastinal shift towards the side of the collapse is
often seen. Further findings are elevation of the hemidiaphragm, reduced vessel
count on the side of the collapse or herniation of the opposite lung across the
midline.

Figure
1: Left mid mediastinal / paraaortic tumour and left upper lobe satellite
lesion

Figure
2: Left basal pleural effusion and consolidation

 Figure
3: Left upper lobe tumour

Figure
4: Right pleural metastases and pleural effusion due to carcinoma of the ovary

Figure
5: Pleural calcifications and adhesions due to asbestos exposure

Figure
6: Pulmonary fibrosis and superimposed infection

Figure
7: Right middle lobe pneumonia

Chest X-Ray – Systematic Approach

Introduction

A systematic approach in the analysis of chest X-rays is used to ensure that important structures are not missed, and a flexible approach is needed for different clinical situations.

Although there is no single agreed upon order of image analysis, you can find many examples of chest x-ray descriptions.

Below is a short example.

Anatomical structures checklist

1. Trachea and large bronchi

2. Lung roots

3. Lung fields

4. Pleura

5. Lung lobes/interlobar fissures

6. Rib-diaphragm Minor sinuses

7. Diaphragm

8. Heart

9. Mediastinum

10. Soft tissue

11. Skeletal framework

analysis of patient data, image data and image quality. Next, you will study where and what pathological changes can be described. The manual also discusses an overview of blind spots where it is easy to miss a pathological process. Your results will be better if you are able to analyze and relate clinical data to radiological findings.

Patient and image data

Patient identifiers and date

Patient identification must be performed before X-ray image interpretation. The date of the examination, as well as, necessarily, the time, must be noted, as the patient may have more than one radiograph on the same day.

Image Projection

Note which view, AP or AP, the image was taken; standing, lying or sitting; stationary or mobile device.

Image annotations

Useful information is often displayed on an image. If the projection is not marked, it is likely that the image was taken in a standard anterior-posterior (PA) projection. If there are side markers, pay attention to the correct position of their position.

Image quality

Image quality should always be assessed as clinical questions cannot be answered if the image quality is inadequate.

Pay attention to the rotation of the chest, the depth of inhalation and the adequacy of the penetrating power of the x-rays.

Image annotations

Artifacts

When you describe a chest x-ray, it is good practice to comment on the presence of any artifact.
An example is shown below.

Central catheter position ?

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A large number of radiographs are taken to assess the position of medical equipment such as a nasogastric tube or central catheter. If you are evaluating a chest x-ray for this purpose, remember to evaluate the entire image systemically.

Obvious pathology

It is advisable to start the analysis with the most pronounced pathology. However, once done, it is important to continue analyzing the rest of the image according to the checklist. Remember that a more prominent pathology may not be of clinical significance.

For example, don’t make the mistake of devoting most of your time to rigorously following a systems approach while ignoring obvious pathology.

The rule can be stated as – don’t ignore the “elephant” in the image – describe its long trunk, its large ears, tusks and rough, gray skin and you will increase the probability of diagnosing the “animal” you are dealing with, but then you must continue the analysis with a systematic approach to look at the rest of the image.

Description of pathology

The art of radiology, not merely in stating and describing pathological features, but knowing how to relate the meaning of these pathological features and knowing which ones can be omitted. First, describing radiographic features can be difficult, and many medical students want clear terminological rules. However, in reality there are no clear rules. The main difficulties begin when describing the pathology of the lung parenchyma. What one radiologist describes as “darkening” may be referred to by others as “decrease in pneumatization” or “infiltration.” In fact, all of these terms are acceptable.

The description of the pathology on a chest x-ray can be compared with the description of a skin rash in a dermatological patient. Attention should be directed to such features as quantity, localization, size, shape, density and structure.

Special Findings

There are many specific radiological findings that can guide you towards the correct diagnosis. For example, occlusion of the costophrenic sinus, forming obtuse angles with the chest wall, should make you think of a pleural effusion. Obvious consolidations (infiltrations) with a sign of an air bronchogram should first of all suggest an infectious process. These signs must be indicated in the descriptive picture.

If you see one of these clear signs, try not to jump to conclusions. Continue the systematic description of the changes and perhaps you will see that the blunting of the angle of the costophrenic sinus is caused by emphysematous enlargement of the lung fields, and the consolidation of the lung tissue is combined with the destruction of the rib, making cancer a more likely diagnosis? than pneumonia.

Location of changes

In addition to determining the side of the identified changes, it is necessary to evaluate the localization in the anterior-posterior projection. A lateral view helps to localize changes in 3D space, but this is also possible from a direct view, with knowledge of x-ray anatomy and understanding of the contours of the shadows.

Contour sign

Contour sign is an erroneous name, it is more correct to call it a “lost contour” sign. Normal adjacent anatomical structures of varying density form clear “silhouettes” or contours. Violation of normal boundaries can help determine the position of the pathological process.

For example, the heart (soft tissue density, white color) borders on lung tissue (air density, dark color). A clear contour, or “silhouette” is formed at the junction of two fabrics of different density. The loss of a clear contour of the right heart (formed by the right atrium) suggests localization of the disease in the right middle lobe, which is adjacent to the right atrium. The loss of the density difference of the left heart contour indicates the pathology of the lingular regions (the part of the upper lobe of the left lung that surrounds the left ventricle).

Changes simulating a contour sign

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Changes simulating a contour sign

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03

After a systematic complete examination of the chest, it is worth re-examining areas that may be hiding important pathology.

It is always worth double-checking that there is no pneumothorax or pneumoperitoneum. And indicating their absence in the descriptive part is a good practice.

Pneumothorax is easily seen at the apex on an anteroposterior radiograph. Pneumoperitoneum (free gas under the diaphragm), only visible on standing x-rays

Other areas to look at include soft tissue, bone, posterior mediastinum, and image margins.

Inspection areas – Tops

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Inspect areas – Bones

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Area Inspection – Heart Shadow

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Area Inspection – Diaphragm

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Area Inspection – Edges of Image

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Clinical Tasks 900 03

At first, most students think that X-rays provide accurate answers without comparing them with clinical data. Sometimes this may be the case, but ideally radiography should always be interpreted in full correlation with the clinical findings. Most radiological conclusions can only be given in the light of clinical data. Thus, you should always be provided with specific clinical data when requesting an x-ray.

Often the results will confirm the preliminary diagnosis, and the absence of changes will improve the prognosis, since an experienced clinician will often know the diagnosis before the X-ray examination, and use it to clarify the extent and localization of the pathological process.

Therefore, results should only be interpreted in relation to clinical data. Remember, the radiologist does not treat the patient. Occasionally there will be incidental findings that require careful consideration, especially if they can be interpreted in two ways or if they do not correspond to clinical data.

No clinical data provided

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Clinical data provided

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missing important changes.

Patient data and image quality must always be evaluated.

Anatomical structures checklist

Trachea and large bronchi

Lung roots

Lung fields

Pleura

Lung lobes/interlobar fissures

Costophrenic sinuses

Dia fragma

Heart

Mediastinum

Soft tissue

Skeletal framework

If you see pathology, try to localize and describe it as completely as possible before continuing to examine the image. Finally, double check the areas of interest.

Try to answer specific clinical questions.

X-ray examination of the child’s chest

X-ray is an informative and inexpensive method of radiological examination. Having passed ionizing rays through the area under study, the device produces a black-and-white image, in which tissues of different density receive a different shade: the denser the tissue, the more rays it retains and reflects, the lighter the shadow in the image (example: chest bone structures are visible on X-ray as white, lung tissue is dark). Thus, it is possible to detect seals or gaps in uncharacteristic places, which makes it possible to suspect the presence of a neoplasm or a violation of the integrity of the organ.

Advantages: non-invasiveness, accessibility (X-rays are available in all major clinics), speed of conduction, obtaining a picture that can be presented to different doctors on demand.

Why is X-ray harmful?

One of the few disadvantages of the method is its radioactivity. Large doses of radiation can provoke changes in the structure of cells and serve as an impetus for the development of tumors, malignancy of hyperplasia. Therefore, exposure is strictly dosed – the study is rarely carried out more than 3 times a year.

This is why, unlike adults, children do not undergo fluorography: increased cell division in childhood increases the risk of developing oncopathologies.

Only by carefully evaluating the balance of harm and benefit, the doctor may order a chest x-ray of the child.

When can a procedure be scheduled?

• If serious diseases of the lungs and bronchi are suspected: pneumonia, obstructive bronchitis, asthma, tuberculosis, abscess, pleurisy, tumors
• To assess the state of the thymus (thymus gland) in case of suspected tumor, the presence of problems with immunity
• After trauma with a high probability of dislocations, fractures, pneumothorax, hemothorax, the presence of traumatic foreign bodies
• With symptoms of asphyxia (suffocation) to detect the cause of obturation (blockage) of the trachea, examination of vessels for damage or the presence of blood clots
• When planning an operation for a child with cardiac pathologies

Performing x-ray diagnostics

X-rays of the lungs of a child should not be performed on adult equipment, as it requires a reduction in the radiation dose. Modern digital devices for pediatric use allow minimizing radiation exposure, and in addition, they are adjusted to children’s dimensions and are equipped with special non-traumatic fixators.

The procedure is quick:

Young children are restrained vertically with a restraint or examined lying down with padded straps on the couch. Body parts not involved in the study are covered with a lead apron of the appropriate size.

• Infant can be held by the mother, who is also given an apron for protection
• Adult children who are able to remain still for the required time are examined while standing

The procedure takes no more than a few seconds. It is important to remain completely still in a given position for this time in order to obtain a clear image.

Types of X-ray examinations

In addition to static radiography, there are other methods of X-ray examination.

• Fluorography – photograph of a picture from a fluorescent screen, depicting the examined organ in a reduced form
• Fluoroscopy (X-ray television transillumination) – demonstrates the organ on the screen in real time. Previously, fluorescent screens were used to show the image of the organ. With the development of digital technologies, the image began to be broadcast on the monitor, and also stored on a digital medium. The radiation dose during fluoroscopy is higher than with radiography, but the method is indispensable for some manipulations, as it allows you to observe instantaneous changes in the organ (during bronchoscopy, some operations)
• Computed tomography – allows you to examine the structures of the organ in detail, cross-sectional. Some operations are also performed under CT guidance. However, up to 7 years, the study is performed under anesthesia, as the patient is required to lie still for 15–20 minutes

These chest x-ray methods for a child are performed strictly according to indications (for example, in cardiac surgery).

How often can an x-ray be taken?

Unlike radioactive substances, rays do not accumulate in the body, the effect of radiation stops with the procedure. Therefore, when performing an x-ray of the lungs of a child, a single dose of radiation, the duration and frequency of exposures will matter.

X-ray exposure is measured in Sieverts and averages between 0.1 and 0.42 millisieverts per image (chest CT about 7 mSv). Digital devices allow you to further reduce the dose.

At the same time, according to the recommendations of the Ministry of Health of the Russian Federation, the maximum annual radiation dose should not exceed 1 mSv per year on average (over the next 5 years) and maximum over 1 year – 5 mSv.

Thus, X-ray diagnostics of the chest can be carried out without harm to health from 3 to 10 times a year (depending on the settings of the device, the age and health of the child).

Benefits of the procedure at MEDSI

• Availability of the latest generation digital devices for children with comfortable fixation devices – safe examination in a calm environment
• Visit at your convenience
• Image interpretation by experienced diagnosticians
• Possibility of having a procedure and visiting a pulmonologist, phthisiatrician or pediatrician with the results of the examination in the same place

To make an appointment, call the round-the-clock phone number 8 (495) 7-800-500.