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Body Logs > L18- Medical imaging > Flashcards

L18- Medical imaging Flashcards

1
Q

How do X-rays give an image?

A
  • there is a focused beam of high energy electrons
  • these can pass through the body onto reciever
  • but some are absorbed or scattered (attenuation)
  • this depends on the density and atomic number (metals)
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2
Q

If something appeared very light on an x-ray what would that mean about its density?

A

More dense/higher atomic number = more attenuation and hence lighter appearance

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3
Q

From dark to lightest what are the 5 principle densities?

A 
DARKEST 
1. Air
2. Fat
3. Soft tissue
4. Bone
5. Metal
LIGHTEST
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4
Q

What do you need to keep in mind when reading an X-ray?

A
  • Date taken
  • patient demographics
  • penetration (amt of energy)
  • The view: Posterior to Anterior (back to front) or Anterior to posterior (front to back)
  • Rotation
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5
Q

What is the mnemonic to reading a chest x-ray?

A

ABCDE

  1. A: AIRWAYS: Trachea, right and left bronchus
  2. B: BREATHING- lungs (do they go the whole way?)
  3. C: CIRCULATION: Heart and aorta, shadows, are they well defined, size of heart?
  4. D: DISABILITY: bones
  5. E: EVERYTHING ELSE
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6
Q

What is the mnemonic to reading an abdominal X-ray?

A

ABDO:

  1. AIR
  2. B: BOWEL: small bowel and large bowel
  3. D: DENSITIES (BONES)
  4. O: ORGANS
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7
Q

Advantages and disadvantages of using X-RAY?

A

Advantages:

  • quick
  • portable
  • cheap
  • simple

Disadvantages:

  • small amt of radiation
  • one plane (2D)
  • would not see all pathology
  • cannot visualise all areas
  • poor soft tissue imaging
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8
Q

Uses of X-RAY?

A
  • Chest: infection, pneumothorax, trauma, effusion, oedema
  • bowel: perforation, dilation
  • orthopaedic: fratures
  • post-procedure: nasogastric tube, pacemaker, PICC
  • Dentist
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9
Q

What is fluoroscopy?

A

Fluoroscopy is a type of medical imaging that shows a continuous X-ray image on a monitor, much like an X-ray movie

  • constant stream ofx-ray
  • often enhanced by contrast: barium iodine, or gadolinium that strongly absorb x-rays
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10
Q

Use of fluoroscopy?

A
  • angiography
  • contrast SI studies
  • therapeutic joint injections
  • arthrograms
  • screening in theatre
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11
Q

Advantages and disadvantages of fluoroscopy?

A

Advantages:

  • dynamic studies
  • cheap
  • interventional procedures

Disadvantages:

  • clinician exposure must be minimised
  • radiation
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12
Q

What does computed tomography involve?

A
  • rotating gantry: x-ray tube on one side with detectors on the other
  • images put together by a computer with same principle of attenuation
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13
Q

What is the view of a CT scan?

A
  • looking from feet up (transverse imaging)
  • Left side of image: right side of body
  • right side of image: left side of body
  • spine is posterior
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14
Q

What side are the following organs in the body:

a) liver
b) spleen
c) kidney
d) appendix
e) gall bladder

A

a) Right
b) left
c) both
d) right
e) right

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15
Q

Advantages and disadvantages of a CT scan?

A

Advantages:

  • quick
  • good spacial resolution
  • can scan most areas

Disadvantages:

  • radiation
  • low contrast resolution
  • affected by artefact
  • requires breath holding
  • overuse
  • incidental findings
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16
Q

Uses of CT scan?

A
  • Diagnosis: cancer, stroke, bony injury, blood flow
  • guide further tests or treatments; radiotherapy, biopsy
  • monitor conditions: cancer treatment
17
Q

How does an MRI work?

A
  • strong,magnetic field
  • aligns h atoms
  • some point towards head and some toward feet
  • radio frequency pulse applied
  • unmatched ions absorb energy and spin in different direction
  • pulse is turned off and atoms spin returns which emits energy
  • computer processing to generate image
18
Q

MRI WEIGHTING

What colour is a) Fat and b) Water in the following:

i) T1 weighting
ii) T2 weighting

A

i) a) fat is white b) water is black

ii) a) Fat is black b) Water is white

19
Q

Uses of MRI scan?

A
  • CNS: brain and spinal cord
  • bones and joint
  • heart and blood vessels
  • internal organs
20
Q

Advantages vs disadvantages of MRI?

A

Advantages:

  • no radiation
  • good contrast resoution

Disadvantages:

  • expensive
  • time consuming
  • availability
  • claustrophobic
  • some patients wont fit
  • loud
  • lie still
  • metal work
21
Q

What is involved in Positron Emission Tomography (PET SCANS)?

A
  • radionuclides that decay positron emission
  • bound to nucleus
  • PET camera detects annihilations (high energy gamma rays), more annihalations the bigger the signal
22
Q

What is PET scans used for commonly?

A
  • oncology: tumor staging, assessment of treatment, differentiate benign and malignancy
23
Q

How does ultrasound work?

A
  • high frequency sound waves from transducecr probe
  • sound wave is reflected back by tissues where density (impedance) differs
  • probe detects reflected sound waves
  • creates electrical signal
  • determine distance: time taken to come back and impedance: proportion of reflected waves
24
Q

What does:

a) hyperechoic
b) hypoechoic
c) anechoic

mean in terms of ultrasound?
COLOURS

A

a) more refelctive - white
b) less reflective- dark greay
c) not reflective (pure fluid)- black

25
Q

Think about an ambulance going past you.

How does flowing blood affect DUPPLER Ultrasound signal when:

a) coming towards
b) going away?

A

a) increased frequency

b) decreased frequency

26
Q

Common ultrasound scans?

A
  • pregnancy

- neck dopplr for carotid artery stenosis

27
Q

Uses of ultrasound?

A
  • Solid organs: liver, kidneys, spleen, pancreas, thyroid, testes
  • urinary tract: stones, dilation, volume
  • obs and gynae: pregnancy, uterus
  • musculoskeletal
  • use in body cavities: transvaginal, transrectal, transoesophageal
28
Q

Advantages vs disadvantages of ultrasound?

A

Advantages

  • lack of ionising radiation
  • low cost
  • portable
  • can be inserted into body cavities
  • babies
  • dynamic (blood flow)

Disadvantages:

  • operator dependant
  • no bone or gas penetration
  • body habitus
29
Q

a) How much radiation are we exposed to in one year normally?

b) How much radiation do the following expose us to:
i) chest x-ray
ii) ab x-ray
iii) CT abdomen
iv) CT chest
v) CT head
vi) ultrasound
vii) MRI

A

a) 2.2mSv/year

b)

i) 0.02mSv equiv to 3 days
ii) 0.7mSv equiv to 4 months
iii) 10mSv equiv to 4.5 years
iv) 8mSv equiv to 3.6 years
v) 2mSv equiv to 1 year
vi) 0 mSv
vii) 0mSv

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