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Body Logistics > An Introduction to Medical Imaging: > Flashcards

An Introduction to Medical Imaging: Flashcards

1
Q

Describe what is meant by the coronal, sagittal and transverse body plane?

A

Sagittal plane - from the side of someone.
Coronal plane - looking straight ahead.
Transverse plane - looking from feet up/head down.

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2
Q

How do you produce an X ray image?

A
  • Electrons accelerates towards a metal target, produces photons (X rays) (single pulse of X rays).
  • Some X rays pass through the patient to a detector.
  • Some are attenuated by the patient (e.g. absorbed or scattered).
  • an image is created.
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3
Q

What does the amount of attenuation of X rays depend on?

A
  • density and atomic number of tissue/material.

- energy of the X-ray beam.

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4
Q

What are the advantages of X rays?

A

They are quick, portable, cheap and simple.

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5
Q

What are some disadvantages of X-rays?

A
  • radiation omitted (risk relatively low).
  • poor soft tissue imaging.
  • cannot see all pathology.
  • one plane, two dimensional.
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6
Q

What are the clinical uses of X-rays?

A
  • chest (for chest pain, pneumothorax, infection etc).
  • abdomen/pelvis (obstruction, pain or perforation)
  • MSK (for trauma, pain, fracture or tumours).
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7
Q

How do you carry out a fluoroscopy?

A
  • similar process to an X-ray.

- instead pulsed/continuous X rays are used to create moving images.

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8
Q

What are the clinical uses of fluoroscopy?

A
  • vascular/angiography (e.g. coronaries)
  • GI
  • GU (genitourinary - genital/urinary systems).
  • MSK (orthopaedic surgery, therapeutic joint infections).
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9
Q

What are the advantages of fluoroscopy?

A
  • real-time moving images created.
  • can assess function or carry out intervention in real-time.
  • quick
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10
Q

What are the disadvantages of fluoroscopy?

A
  • Higher radiation dose than a single X ray.
  • radiation exposure to clinician.
  • poor soft tissue imaging.
  • cannot see all pathology.
  • one plane, two dimensional.
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11
Q

How is a CT scan produced?

A
  • X rays produced in standard way.
  • X ray tube on one side of a rotating gantry (ring), detectors on the opposite side.
  • patient moves through gantry.
  • same principle of X ray attenuation as before.
  • cross sectional slices of the patient imaged and processed by computer.
  • cross sectional images produced.
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12
Q

What are the clinical uses of CT?

A
  • diagnosing/guiding further investigation/management (e.g. infection, bleed, cancer etc).
  • directly guiding an intervention (e.g. biopsy, radiotherapy).
  • monitoring conditions (e.g. cancer treatment).
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13
Q

What does CT stand for?

A

Computed tomography (CT)

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14
Q

What are the advantages of CT?

A
  • quick
  • good spacial resolution
  • can scan most parts of the body well (but not all)
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15
Q

What are the disadvantages of CT?

A
  • radiation
  • lower contrast resolution
  • affected by artefacts
  • requires breath holding (not all patients can do this).
  • not the best for some areas (e.g. gynae)
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16
Q

What is the full name for a PET scan?

A

Positron emission tomography scan

17
Q

How does a PET scan work?

A
  • uses radionuclides to emit positrons during decay.
  • emitted positrons collide with nearby electrons in patient (annihilation).
  • two annihilation gamma photons are produced which are detected by the gamma camera.
  • gamma camera contains a scintillator (converts signal into light).
  • light sample amplified and processed by computers to produce images.
18
Q

What type of rays from the electromagnetic spectrum are used in a PET scan?

A

Gamma rays (NOT X-rays)

19
Q

What are some clinical uses of PET scans?

A
  • oncology (detection of tumours, staging and response to treatment).
  • neurological (localisation of seizure focus, and diagnosis of Alzheimers disease).
  • cardiac
  • infection/inflammation (pyrexia of unknown origin).
20
Q

What are the advantages of a PET scan?

A
  • good contrast and spatial resolution.

- can analyse anatomy and function.

21
Q

What are the disadvantages of a PET scan?

A
  • physiological uptake of radiopharmaceutical
  • radiation dose to patient
  • risk of radiation to others
  • radioactive waste produced
  • very expensive and time consuming.
22
Q

When is a radiopharmaceutical used and what do both parts of it do?

A
  • Used in a PET scan.
  • pharmaceutical (takes compound to tissues of interest)
  • radionuclide (creates the image)
23
Q

What does MRI stand for?

A

Magnetic resonance imaging

24
Q

How does MRI work?

A
  • Atoms spin in random directions around their individual magnetic fields.
  • in the magnetic field produced by the MRI, atoms line up either north or south. Roughly half the atoms go each way, but there are a few unmatched atoms.
  • when radio frequency pulse is applied, the unmatched atoms spin the other way.
  • when the radio frequency is turned off the extra atoms return to normal position, emitting energy.
  • the energy sends a signal to a computer which uses a mathematical formula to convert the signal into an image.
25
Q

How is the contrast in MRI images created?

A
  • From different relaxation times of the hydrogen atoms back to their normal positions in different tissues.
26
Q

What are the advantages of MRI?

A
  • no radiation used.

- good contrast resolution (especially of soft tissues).

27
Q

What are the disadvantages of MRI?

A
  • expensive
  • time consuming
  • not many machines/radiographers
  • can be a claustrophobic process
  • risk of magnetic objects becoming missiles in the room.
  • risk of overheating
28
Q

What are the clinical uses of MRI?

A
  • CNS (brain and spinal cord).
  • bones and joints
  • soft tissue lesions
  • heart and blood vessels
  • gynaecological (female reproductive system) tumours.
  • used in pregnancy/paediatrics to avoid radiation from CT.
29
Q

How is an ultrasound produced?

A
  • uses sound waves (not part of electromagnetic spectrum).
  • high frequency sounds waves are released.
  • sound waves travel through tissues and are reflected back at boundaries between tissues of different densities.
  • probe detects reflected sound waves and converts them into electrical signal to create an image.
30
Q

What does hyperechoic and hypoechoic mean in relation to an ultrasound?

A
  • hyperechonic = more reflection (white on image)

- hypoechomic = less reflection (dark on image)

31
Q

What is the time taken for the echo to return used to calculate in an ultrasound?

A

Where it was reflected from.

32
Q

How would something moving towards or away from the sound wave be affected during an ultrasound?

A
  • moving towards the wave - increase frequency of echo wave.
  • moving away from the wave - decreased frequency of echo wave.
33
Q

What are the clinical uses of ultrasound?

A
  • look at solid organs (e.g. liver, pancreas, kidney etc.)
  • look at hollow structures (tubes, ducts, bladders).
  • obstetrics (pregnancy, fetal growth/placental location).
  • musculoskeletal (assessing muscles, tendons, ligaments, joints, nerves etc).
34
Q

What are the advantages of ultrasounds?

A
  • lack of radiation
  • low cost
  • portable
  • dynamic (can see movement and assess blood flow).
35
Q

What are the disadvantages of ultrasounds?

A
  • operator dependent (must be experienced at them).
  • no bone/gas penetration.
  • difficult with obese/fragile/unwell patients.
  • theoretical risk of overheating foetus if misused.
36
Q

What is not visible on a chest X ray?

A

Air

37
Q

In T1 and T2 weighting what colours would fat and water be?

A

T1- Fat is bright, water is dark.

T2 - Fat is quite bright, water very bright.

Body Logistics (6 decks)

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