CXR & CT white vs dark space
- Solid tissues absorb radiation and appear
white on diagnostic imaging - Air filled spaces do not absorb radiation
and thus will appear dark
MRI uses
magnets and radiofrequency pulses
Ultrasound uses
high frequency sound waves, reflected from tissues
Nuclear medicine imaging uses
Radioactive medication is injected, inhaled
or swallowed, then picked up with a gamma camera
common Conditions for Imaging
- Chest infection
- Respiratory failure
- Adult respiratory distress syndrome (ARDS)
- Pulmonary embolism
- Trauma
Common diseases for Imaging
- Cystic fibrosis
- Bronchiectasis
- Chronic obstructive airways disease (COPD)
- Cancer (tumour)
- Congenital disease
Chest X-ray limitation
– Provides a 2D view of a complex, 3D structure
– Therefore requires multiple CXR views to visualise structures adequately
How a CXR is taken: Posterior-Anterior (PA) view
- Rays pass posteriorly to anteriorly, with plate in front of patient
- PA is the standard/ideal Xray view
- Once taken, a CXR is always viewed as if the patient is facing you
How a CXR is taken: Lateral view
- The lateral view often provides key findings that are not visible on the frontal view
- The patient has the left chest wall on the cassette
– diminishes effect of heart magnification
– demonstrates better anatomical detail of the heart
How a CXR is taken: Anterior – Posterior (AP) view
- Also called “mobile” or “portable” film
- Used when patient is unable to stand or go to the radiology department (eg in ICU, ED)
- May be taken sitting upright in bed or supine
How to Read a CXR
- Technical details
- Quality of film
- Extra-thoracic structures
* UL girdle, soft tissues, abdominal structures - Thoracic cage
* Bones, diaphragm - Intra-thoracic structures
* Mediastinum (trachea, heart, hilum)
* Lung fields - Attachments/foreign structures (devices, implants, lines,
tubes etc)
what are the technical details
- Check image for name, date, time, MRN
- Look for the side marker indicating:
– View (projection): PA, AP or Lateral
– Left or right
what are Image Quality
- Rotation/alignment
– Medial ends of clavicle should be equidistant from the spinal processes - Level of inspiration
- Film should be taken on full inspiration
– Anteriorly: rib 5-6 on right intersects mid diaphragm
– Posteriorly: rib 9-10 on right intersects mid diaphragm - Exposure
– The IV disc should be just visible through heart shadow
what are Extra-thoracic Structures
Upper limb girdle, including
– Clavicle height
– Scapular outlines
Soft tissues
– Muscles/adipose tissue
– Breast shadows
Below diaphragm
– Air, eg gastric bubble
what is the thoracic cage
- Spine
– Curvatures (eg scoliosis), rotation - Ribs
– Shape ant & post
– Crowding or increased rib spaces - Diaphragm
– Shapes, outline/borders, position, angles
what is a raised diaphragm indicative of
‒ Paralysed (SCI or phrenic nerve)
‒ Lower lobe atelectasis/collapse
‒ Low lung volumes/poor inspiratory effort
what is a lowered diaphragm indicative of
‒ Hyperinflation: gas trapped inside lungs (eg, asthma, emphysema) or
‒ Gas in the pleural space (pneumothorax)
what is the Intra-Thoracic Structures
- Mediastinum
– Trachea
– Hilar regions
– Heart and major vessels - Lung fields
what does the hillier region contain
pulmonary arteries/veins, bronchi, lymph nodes
Note position (L should be higher than R)
what should the heart position be
– 1/3 on right, 2/3 on left
what should the lung fields appear as
appear mostly dark, with thin white lung markings throughout
‒ Lung markings (blood vessels) should extend to edges (Absent in pneumothorax)
- density of the lungs should be L=R
what are the 3 main types of chest CT
- Standard method
- CTPA (CT pulmonary angiography)
- High resolution CT
- Standard method of chest CT used for
to highlight mediastinal structures
CTPA (CT pulmonary angiography) used for
Looking for blood flow anomalies, such as pulmonary embolus
