Session 2 ILOs - An introduction to medical imaging

Question 1

X-ray

Describe the fundamental principles of how this technique works, the advantages and disadvantages
Give a clinical example of where the technique can be used most efficiently

Answer 1

How it works: X-rays work by firing electrons at the subject that are absorbed on a screen on the other side to form the image. Substances that absorb electrons well will be white e.g. bones, however those that don’t absorb well will be black e.g. air

Advantage: Able to see clearly the hard structures in the body and are relatively fast and painless

Disadvantage: Does expose the individual to a small amount of radiation, therefore the benefits of the scan need to be compared against this. Also, only 2D images are formed.

Clinical example: able to x-ray an area of possible bone fracture to confirm if and how it has been broken

Question 2

Fluoroscopy

Describe the fundamental principles of how this technique works, the advantages and disadvantages
Give a clinical example of where the technique can be used most efficiently

Answer 2

How it works: The individual is given a fluorescent fluid (ingested or injected) and it can show the route of the fluid through the body. An x-ray is done and the fluid absorbs the x-rays very well = image/animation formed

Advantage: Very low risk and can see real time, live images of processes = accurate representation

Disadvantage: Some radiation & very low risk of complications

Clinical example: Patient can swallow the fluid and you are able to observe their swallow response

Question 3

CT (Computerised Tomography Scanning)

Describe the fundamental principles of how this technique works, the advantages and disadvantages
Give a clinical example of where the technique can be used most efficiently

Answer 3

How it works: CT scans work by firing x-rays in a circular range, to help create a 3D image

Advantage: Able to form 3D imagines see clearly the structures in the body and relatively fast (used in emergency situations)

Disadvantage: Exposes the individual to a small amount of radiation and requires breath holding

Clinical example: To find/check tumour development, brain for a subdural haemotoma

Question 4

MRI (Magnetic Resonance Imaging)

Describe the fundamental principles of how this technique works, the advantages and disadvantages
Give a clinical example of where the technique can be used most efficiently

Answer 4

How it works: Hydrogen atoms are excited with the magnetic forces and orientate, once the magnet is turned off then the electrons reorientate themselves and this energy is captured and helps to form the image. Can have 2 forms of MRI, T1 (air/fat = black, bone = white) and T2 (air/fat = white, bone = black)

Advantage: Able to form a very clear, 3D image of a section of the body and NO radiation

Disadvantage: Involves magnets so isn’t available to everyone, it’s a slow process (non-emergency), expensive and some individuals struggle with claustrophobia

Clinical example: MRI scans can be used for brain scans to identify tumours

Question 5

PET (Positron Emission Tomography)

Describe the fundamental principles of how this technique works, the advantages and disadvantages
Give a clinical example of where the technique can be used most efficiently

Answer 5

How it works: radioactive tracers that are combined with glucose are ingested or injected and then absorbed by body tissue. PET camera detects the emitted gamma rays. Hot spots are areas of high glucose metabolism - heavily used in oncology

Advantage: PET scans show areas of high metabolic activity and can be combined with CT/MRI for a more accurate diagnosis

Disadvantage: May not be appropriate for diabetic patients as it uses glucose

Clinical example: Used heavily in Oncology, tumour staging, assessment of treatment etc.

Question 6

Ultrasound Scanning

Describe the fundamental principles of how this technique works, the advantages and disadvantages
Give a clinical example of where the technique can be used most efficiently

Answer 6

How it works: high frequency sound waves are sent from the transducer probe and the sound waves are reflected back by tissues where density differs

Advantage: Non-invasive, cheap, quick

Disadvantage: Can only be used for soft tissues as bones, air and stones block = acoustic shadowing

Clinical example: Ultrasounds to check stages in pregnancy