CXR

Question 1

Four basic radiodensities

Answer 1

1. Gas = Black e.g. air filled lungs
2. Fat = Grey e.g. lipid tissue around muscle
3. Soft tissue = Grey e.g. heart, blood vessels & muscle
4. Bone or metal = White e.g. ribs & sternum

Question 2

Types of CXR

Answer 2

Posteroanterior (PA) Most common. X-ray passes posterior to anterior with the plate anterior to the patient’s chest. Patient is upright & the scapula are rotated away from the lung fields

Anteroposterior (AP)
Commonly used for portable CXR’s. X-ray passes anterior to posterior. Heart size is magnified

Lateral
Allows visualization of lung bases & lung tissue behind heart
Normally left lung base as this is obscured by the heart

Oblique

Lordotic

Expiratory

Lateral Decubitus

Question 3

Visible structures on CXR

Answer 3

Trachea
Hila
Lungs
Diaphragm
Heart
Aortic Knuckle
Ribs
Scapulae
Breasts
Bowel gas

Question 4

Important obscured/invisible structures on CXR

Answer 4

Sternum
Oesophagus
Spine
Pleura
Fissures
Aorta

Question 5

Preliminary checks

Answer 5

Who - have you got the right patient, check the hospital number and DoB

What – exactly was taken? Is it a CXR as a chest film will demonstrate aspects of the abdomen and MSK system (discuss abdominal x-ray),

When - how old is it? want less than 24 hours to be reflective, are there previous ones to compare to? In emergency less than an hour

Why – was the film taken? was it routine or emergency, was it post treatment or a line insertion

How – was the film taken? What position was the patient in? was it taken on the ward or in the department and then whether it is an AP or PA

Question 6

Quality of CXR

Answer 6

1. Overexposed - frequency of X-rays is too high or length of time the rays have been allowed to pass is too long = too black 2. Underexposed - frequency/intensity too low or not exposed for long enough time = too light

Question 7

Systematic Approach

Answer 7

A – Alignment – rotated using the end of the clavicle to assess

B – Bones – Not just ribs; Are they all there, intact & in a normal position?

C – Cardiac/mediastinum – clear heart boarder? About 1/3 total chest diameter with 1/3 on the right and 2/3 on the left, evidence of shifting?

D – Diaphragms – Are they both visible? Cardiophrenic (relation to heart = rounded) and costophrenic (relation to lungs) angles clear?

E – Expansion – 10th rib posteriorly should bisect the R hemidiaphragm at mid-clavicular line, 8th rib anteriorly; R hemidiaphragm slightly higher

F – lung Fields – clear lung markings (black with white fluffyness)? Densities, lung edge, shifting of structure’s?, fluid level? With collapse & consolidation you will see increased opacity but with collapse you can see shifting of structures or crowding of lung markings

G – Gadgets (drips, drains & tubes) are they in, on or around the patient; obscuring aspects of CXR

Question 8

Other imaging

Answer 8

CT (Computed Tomography)
MRI (Magnetic Resonance Imaging)
US of thorax
CTPA (Computed tomography pulmonary angiogram)

Question 9

What is CT scan used for

Answer 9

Typically used for –
• Bone fractures - Shows bony/thoracic wall lesions v. clearly
• Cancer monitoring
• Identifying internal bleeding
• Differentiates between lung and pleural tissues
• V. useful to visualise mediastinum

Supplements CXR rather than replacing

Question 10

Risks of CT scan

Answer 10

• Harm to unborn babies
• Very small dose of radiation
• Potential reaction to dyes

Question 11

What is MRI used for

Answer 11

Typically used for – 
• Joints	
• Brain
• Wrists & ankles
• Breast
• Heart
• Blood vessels

Particularly good for:

1. Mediastinal vascular problems such as aneurysms
2. Pancoast tumour of lung

Question 12

Risks of MRI

Answer 12

1. Possible reactions to metals due to magnets
2. Loud noises may cause hearing damage
3. Increase in body temperature during long scans
4. Claustrophobia

Question 13

Preliminary checks prior to MRI

Answer 13

1. Artificial joints, or implanted metal work
2. Eye implants
3. IUD
4. Pacemaker/internal defibrillators
5. Cochlear
6. Heart valve
7. Sternal wires
8. Brain aneurysm clips
9. Pregnant
10. Obese

Question 14

What is US of thorax used for

Answer 14

look for pleural effusions, abnormalities of the heart structure and function

Question 15

What is CTPA used for

Answer 15

To help diagnose pulmonary embolism (PE)

Question 16

CT vs MRI

Answer 16

• Both CT and MRI give an internal view
• CT is quicker than MRI
• CT is cheaper than MRI - An average MRI cost is approx. £130 but it depends what the MRI is of and how long it takes and whether it is with contrast or dye and a CT is generally half the cost
• CT is better at providing general images of tissues, organs and skeletal system
• MRI is thought to be more superior in regards to detail of image