Chest Radiology: Points to be NotedCollected by: Tapendra Koirala

May 1, 2023

“Though X-ray is all black and white, it’s not just about black

and white”

- Borrowed from somebody.

Checklist for a systematic approach1. Patient identity2. Image data3. Image quality4. The obvious abnormality - description/location5. Systematic check of anatomy6. Review areas7. Consider the clinical question (ie diagnosis)

Patient identity

I know you are good on this!

Which film? PA or AP

AP vs PA projection The heart, being an anterior structure within the chest, is

magnified by an AP view. Magnification is exaggerated further by the shorter distance

between the X-ray source and the patient, often required when acquiring an AP image. This leads to a more divergent beam to cover the same anatomical field.

As a rule of thumb, you should never consider the heart size to be enlarged if the projection used is AP. If however the heart size is normal on an AP view, then you can say it is not enlarged.

AP v PA - Scapular edges Radiographers will often label a chest X-ray as either PA or AP.

If the image is not labelled, it is usually fair to assume it is a standard PA view.

If, however, you are not sure, then look at the medial edges of each scapula.

If they are wide apart and are not parallel– then film is most likely PA

OR If the scapulae overlie the lung fields then the film is AP. If they do

not it is probably PA.

Once that is decided…

Position the x-ray upright and face Left (L) to your Right & vice versa.

Inspect the immage Quality

Components Rotation Inspiration Penetration

@ Rest In Peace (RIP)

1. Rotation

Check whether the medial end of clavicle are equidistant from the vertebral spinous processes.

Film must be well centered to comment on: Mediastinal shift Cardiomegaly Comparative study of radiolucency

Is the film well centralized?

If the medial end of left clavicle is nearer to spinous process then the film is considered to be rotated towards left and vice versa.

• Heart size can be assessed accurately with a well-centred posterior-anterior (PA) chest X-ray.

• If the patient is rotated to the left the heart may appear enlarged and if rotated to the right its size may be underestimated.

2. Inspiration and lung volume Chest X-rays are conventionally acquired in the inspiratory phase of

the respiratory cycle The radiographer asks the patient to, 'breathe in and hold your

breath!‘ When interpreting a chest X-ray it is important to recognise if there

has been incomplete inspiration If the image is acquired in the expiratory phase, the lungs are

relatively airless and their density is increased Also, the raised position of the diaphragm leads to exaggeration of

heart size, and obscuration of the lung bases

Assessing inspiration

To assess the degree of inspiration it is conventional to count ribs down to the diaphragm.

The diaphragm should be intersected by the 6th to 8th anterior ribs in the mid-clavicular line or 9-11th ribs posteriorly

Less is a sign of incomplete inspiration.

Assessing for hyperexpansion

While checking for adequate inspiration you may notice that a patient's lungs are hyperexpanded (>8th anterior rib intersecting the diaphragm at the mid-clavicular line). This is a sign of obstructive airways disease.

It is possible to assess for hyperexpansion by counting ribs, or by checking for flattening of the hemidiaphragms.

Normal expansion This patient has taken a good breath in such

that the diaphragm is intersected by the 6th rib in the mid-clavicular line.

In film in the left shows an imaginary line (dotted) between the costophrenic and cardiophrenic angles.

The distance between this line and the diaphragm (green line) should be greater than 1.5cm(asterisk) in normal individuals.

In practice this is rarely measured and a quick assessment of diaphragm shape is all that is necessary.

3. Penetration/Exposure

2. Is it a well exposed film? In a well exposed film only the spinous processes of first four

thoracic vertebra are seen. Others are hidden by cardiac shadow. If more than 4 vertebra are seen over exposed (lungs appear more

translucent)

Penetration is the degree to which X-rays have passed through the body.

OR• A well penetrated chest X-ray is one where the vertebrae are just visible behind the

heart.• The left hemidiaphragm should be visible to the edge of the spine. Loss of the

hemidiaphragm contour or of the paravertebral tissue lines may be due to lung or mediastinal pathology.

Why is this important?

Under penetrationThe left hemidiaphragm is not visible to the spineLung tissue behind the heart cannot be assessedRe-windowing the image using digital software can compensate

Well penetration (same pt.)The diaphragm (long arrows) is visible to the spine.The left paravertebral soft tissues are visible (short arrows) , and the right side of the spine is clear (arrowheads). There is no abnormality of lung tissue behind the heart.

Is there any artifacts?

Medical/surgical artifact Instruments (eg. NG tube, chest tube etc.)

Patient artifact Ornaments, Skinfolds Hair artifact

Radiologic artifact Quality issues (rotation, penetration, inspiration etc.)Hair artifact

In summary Image quality influences conclusions Check the image for - Labeling , Projection, Rotation,

Inspiration, Penetration and Artifact Quality is influenced by radiographic technique and patient

factors Check to see if a poor quality X-ray demonstrates a life

threatening abnormality before dismissing it Above all, Can the clinical question still be answered?If the film taken can still

answer the question then why to re-order another?

Once you’ve made sure that you are reading a good quality film then proceed further.

Inspect the lung field1. Study the lung field in 3 zones: Upper, Middle, and Lower

1. Upper: area above the anterior end of 2nd rib2. Lower: area below the anterior end of 4th rib3. Middle: area between above two fields

2. Compare the lung fields on both the side in each of 3 zones• Should be equally radiolucent bilaterally

3. Study the apices (area behind clavicle earliest TB lesion found)4. Look for bony asymmetry5. Look for cardio & costophrenic angles; should be sharply defined

1. Any obliteration is pathological2. Right diaphragm is 1 to 1.5 cm higher than Left diaphragm

1

2

3

1.Upper: area above the anterior end of 2nd rib

2.Lower: area below the anterior end of 4th rib

3.Middle: area in between

Inspect Hila Left slightly higher than the right

Identify the course of trachea up to the carina for any deviation

Inspection of cardiac silhouette Study the cardiac borders

Left cardiac border made up of: Aorta, pulmonary conus, left atrial appendage, and left ventricle

Right cardiac border: SVC and Rt. Atrium Measure the cardiothoracic ratio

Draw a vertical line through spinous processes Then draw perpendicular lines ‘a’ and ‘b’ from the point of maximal width on

left and right border to the vertical line a+b gives the maximum transverse diameter of the heart Measure ‘c’ ie the largest diameter of chest

Transverse line that joins the inner border of ribs at the widest portion of chest

ab

c

CT ratio= (a+b)/c

Inspection of Bones

Ribs Look for crowding/spreading and bony lesions

Clavicle Scapula Shoulder joints

Inspection of soft tissue

Muscles Subcutaneous tissues of the chest and the neck Breast (in female)

Key points - Review areas

Apices - Pneumothorax? Bones/soft-tissues - Fractures/density? Cardiac shadow- Consolidation/mass? Diaphragm - Pneumoperitoneum? Edge of the image - Unexpected findings? Mnemonic - ABCDE

Review areas - BonesBone abnormalities can be very subtle on chest X-rays. Here the first right rib is destroyed by a metastatic bone lesion(?).Compare this poorly defined area of increased soft tissue density with the normal first left rib.

Review areas - Cardiac shadowThe area behind the heart is too dense and the left hemidiaphragm is not well-defined to the midline. This is evidence of consolidation affecting the left lower lobe.There is also a reactive effusion.

Review areas - DiaphragmCheck every chest X-ray for pneumoperitoneum.Occasionally lung pathology is visible through the 'window' of the gastric bubble, which is normal in this case.

Review areas - Edge of the imageWell done if you noticed the small left pleural effusion.Did you spot the missing right humerus?!This patient had a history of a previous malignant bone lesion of the right humerus which had been resected. Note the surgical clips.

Review areas - ApicesA pneumothorax is often a very subtle finding, and may only be seen on a second review of each lung apex.You should also check the lung apices for tumours.

Chest X-ray checklist; A-H

A Airway (midline, no obvious deformities, no paratracheal masses)B Bones and soft tissue (no fractures, subcutaneous emphysema)C Cardiac size, silhouette and retro-cardiac density normalD Diaphragms (right above left by 1 cm to 3 cm, costophrenic angles sharp,

diaphragmatic contrast with lung sharp)E Equal volume (count ribs, look for mediastinal shift)F Fine detail (pleura and lung parenchyma)

G Gastric bubble (above the air bubble one shouldn't see an opacity of any more than 0.5 cm width)

H

Hilum (left normally above right by up to 3 cm, no larger than a thumb)Hardware (in the intensive care unit: endotracheal tube, central venous catheters)

The elephant in the image !If there is an elephant in the image, don't ignore it! Describe it in detail and then use your system to continue scrutinizing the image.

A sample CXR presentation This is the CXR of [child’s name]. The film is an AP view with good inspiratory effort. There is an isolated fracture of the 8th

rib on the right. There is no tracheal deviation or mediastinal shift. There is no pneumo- or hemothorax. The cardiac silhouette appears to be of normal size. The diaphragm and heart borders on both sides are clear, no infiltrates are noted. There is a central venous catheter present, the tip of which is in the superior vena cava. This shows improvement over the CXR from [number of days ago] as the right lower lobe

infiltrate is no longer present.

Thank YouGood luck ! with the X-rays.

Annex

Random collections

Pleural effusion

Table: Common causes of pleural effusionInfectionNeoplasmCardiovascular disease (congestive heart failure)CirrhosisHypoproteinemiaPancreatitisUremiaSubdiaphragmatic abscessTrauma (hemothorax, chylothorax)Occupational (asbestos)Collagen vascular disease (systemic lupus erythematosus)Hypothyroidism (often with pericardial effusion)Pulmonary embolism

• The appearance of an effusion depends on the patient's position at the time of the radiologic examination and on the mobility of the effusion.

• In an upright person, fluid collects mainly in the lower pleural space, as long as it is freely mobile, creating a homogeneous opacity with a curvilinear upper border that is sharply marginated and concave to the lung.

• Fluid can collect in the fissures, creating a ‘pseudotumor’ that conforms to the edges of the fissures and resolves with clearing of lung edema.

• In supine patients, freely mobile fluid layers posteriorly, creating hazy, veillike opacification of the affected hemithorax with preserved vascular shadows.

• Depending on the size of the effusion, this can be a subtle finding; when bilateral, it may not be detected at all, especially when small, or it may be confused with pulmonary edema• Other findings of pleural effusions in supine patients include • blunting of the costophrenic angle (although this is often

a false-positive finding) (6), • capping of the lung apex, thickening of the minor fissure,

and • widening of the paraspinal soft tissues.

• Lateral decubitus views can be useful in verifying pleural effusions when the supine examination is equivocal, and they can allow determination of whether pleural fluid is mobile or not.

• The lateral decubitus view is much more sensitive than the upright view for the detection of pleural effusions; it can demonstrate as little as 5 mL of pleural fluid

Causes of a large unilateral pleural effusion“ITCH”Infection (empyema)Tumor (primary bronchogenic cancer, metastasis, mesothelioma, lymphoma)Chylous (ruptured thoracic duct, lymphoma)Hemorrhage (trauma, either iatrogenic or otherwise)

Re-expansion pulmonary edema. A: PA chest radiograph of a 78-year-old woman with metastatic breast cancer shows a large left pleural effusion associated with collapse of the left lung and shift of the mediastinum to the right. These findings suggest tension hydrothorax. B: PA chest radiograph after placement of a left chest tube and adequate drainage of pleural fluid shows re-expansion pulmonary edema on the left.

Empyema. A: PA chest radiograph of a 60-year-old man with right lower lobe pneumonia shows a large right hydropneumothorax with air fluid level. There is an incidental calcified granuloma in the right mid lung

Tuberculous empyema. PA chest radiograph shows a large left pleural effusion. A large unilateral pleural effusion is worrisome for empyema, hemothorax, malignancy, or chylothorax.

Pneumthorax

In the supine patient, the highest part of the chest cavity lies anteriorly or anteromedially at the base near the diaphragm, and free pleural air rises to this region. If the pneumothorax is small or moderate in size, the lung is not separated from the chest wall laterally or at the apex and therefore the pneumothorax may not be appreciated

In the upright patient, air rises in the pleural space and separates the lung from the chest wall, allowing the visceral pleural line to become visible as a thin curvilinear opacity between vessel-containing lung and the avascular pneumothorax space. The pleural line remains fairly parallel to the chest wall.

Skin fold mimicking pneumothorax

Radiographic signs of pneumothorax in the supine patient• Relative increased lucency of the involved hemithorax• Increased sharpness of the adjacent mediastinal margin and

diaphragm• Deep, sometimes a tonguelike costophrenic sulcus• Visualization of the anterior costophrenic sulcus• Increased sharpness of the cardiac borders• Visualization of the inferior edge of the collapsed lung above the

diaphragm• Depression of the ipsilateral hemidiaphragmRadiologic signs of tension pneumothorax

• Contralateral displacement of the mediastinum• Inferior displacement of the diaphragm • Hyperlucent hemithorax and • Ipsilateral collapse of the lung