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BodyLog * > S9 Medical Imaging > Flashcards

S9 Medical Imaging Flashcards

1
Q

What is an X-ray?

A

Focused beam of high energy electrons pass through body onto receiver (some are absorbed/scattered dependent on density)

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2
Q

Thinking about fat, air, metal, bone and soft tissue, label from high density to low density in X-ray.

A

Air, fat, soft tissue, bone, metal

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3
Q

On an X-ray is white high or low density?

A

High density

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4
Q

What are the advantages of using an X-ray?

A
  1. Quick
  2. Cheap
  3. Portable
  4. Simple
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5
Q

What are the disadvantages of using an X-ray?

A
  1. Radiation
  2. 2D imaging
  3. Can’t visualise all areas
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6
Q

What are the uses of X-ray?

A

Checking for bone fractures and trauma in e.g. the chest

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7
Q

What is fluoroscopy?

A

Uses a constant stream of xrays and is enhanced by contrast media e.g. barium (absorbs xrays)

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8
Q

What are the two examples of plain film imaging?

A

Xray

Fluoroscopy

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9
Q

What are the two examples of cross-sectional imaging?

A

CT

MRI

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10
Q

What are the uses of fluoroscopy?

A
  1. Contrast GI studies
  2. Study of joints
  3. Therapeutic joint injections
  4. Screening in theatre
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11
Q

What are the advantages of fluoroscopy?

A
  1. Cheap

2. Allows for dynamic studies

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12
Q

What are the disadvantages of fluoroscopy?

A
  1. Radiation

2. Clinical exposure must be minimised

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13
Q

What is computed tomography (CT)?

A

Rotating gantry (with X-ray tube on one side, detectors on the other side)

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14
Q

What are the uses of CT scans?

A

Diagnosis (cancer/stroke), guide for tests/treatments (cancer treatment)

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15
Q

What are the advantages of CT scans?

A
  1. Quick

2. Good spatial resolution

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16
Q

What are the disadvantages of CT scans?

A
  1. Radiation
  2. Can be overused
  3. Requires breath holding
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17
Q

What is an MRI scan and how does it work?

A

Has a narrow gantry and uses a magnetic field to align hydrogen atoms in the body, some point one way, the other in the other way (not 50/50), the unmatched atoms absorb energy when radiofrequency pulse applied, it spins and when pulse is turned off, spins back and emits energy which is detected

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18
Q

What is the difference between T1 and T2 in terms of MRI?

A

T1 - fat is white, water is black
T2 - fat is black, water is white

White is the high signal

19
Q

What are the advantages of MRI?

A
  1. No radiation

2. Good contrast resolution

20
Q

What are the disadvantages of MRI?

A
  1. Expensive
  2. Some patients don’t fit
  3. Time-consuming
  4. Loud
  5. Claustrophobic
  6. Not safe if have metal work
21
Q

What is a positron emission tomography (PET) scan?

A

Decay of radionuclides by positron emission. Binds to glucose (see ‘hot spots’ (darker areas) where there is a high glucose metabolism)

22
Q

What are the uses of PET scans?

A

Oncology - determining if a tumour is benign or malignant, what stage a tumour is in, etc.

23
Q

What is ultrasound and how does it work?

A

Using high frequency sound waves which are reflected back where density differs and are detected by a probe.

More reflective areas (bone/air/stones) are white, non-reflective areas (pure fluid) are black

24
Q

Why can’t you see behind bone, air or stones on a ultrasound?

A

There is such a great difference in tissue density that means the sound waves are completely reflected (acoustic shadowing)

25
Q

How does blood affect an ultrasound?

A

Doppler effect - moving objects influence sound waves.

Blood moving towards sound waves increases the frequency and moving away the opposite.

26
Q

What are the uses of ultrasound?

A
  1. Obs/gynae - pregnancy and uterus
  2. Looking in body cavities
  3. Looking at the urinary tract - stones?
  4. Looking at solid organs - liver, kidneys, spleen, etc
27
Q

What are the advantages of ultrasound?

A
  1. Cheap
  2. Portable
  3. Can be inserted into body cavities
  4. Dynamic (blood flow)
  5. No radiation
  6. Can be used on babies
28
Q

What are the disadvantages of ultrasound?

A
  1. Operator dependent

2. No bone/gas penetration

29
Q

How many days/months/years of background radiation do chest and abdominal X-ray scans cause?

A

Chest - 3 days

Abdominal - 4 months

30
Q

How many days/months/years of background radiation do chest and abdominal and head CT scans cause?

A

Chest - 3.6 years
Abdominal - 4.5 years
Head - 1 year

31
Q

How many days/months/years of background radiation do ultrasound scans cause?

A

0

32
Q

How many days/months/years of background radiation do MRI scans cause?

A

0

33
Q

What is nuclear medicine?

A

Administration of radio-pharmaceuticals labelled with radioactive tracers into the body - drugs have affinity for specific body tissues.

34
Q

What is nuclear medicine useful for?

A

Displaying physiological function e.g excretory function of the kidneys, blood flow to heart muscle, etc.

35
Q

What is angiography?

A

Medical imaging technique to visualise blood vessels

36
Q

Why is contrast media useful?

A

Helps better differentiate tissues

37
Q

What is an example of contrast media?

A

Barium sulphate (Barium meal)

38
Q

Contrast media can be negative or positive, give examples of each and which colour they show up as.

A

Positive - barium, iodine and gadolinium - white

Negative - water, air, CO2 - black

39
Q

What are the ideal factors for contrast media to be effective?

A
  1. Low osmolality and viscosity
  2. High water solubility
  3. Biologically inert
  4. Safe
  5. Heat and chemical stable
  6. Cost effective
40
Q

How can contrast media be administered?

A
  1. Orally
  2. Rectally
  3. By IV
41
Q

How is contrast media excreted?

What is its half life?

A

By the kidneys (consider consequences of using if person has kidney damage)

30-60mins

42
Q

What are the side effects of contrast media?

What two types of side effects are there?

A
  1. Endothelial damage
  2. Thrombosis
  3. Vasodilation
  4. Vascular pain
  5. Idiosyncratic (can’t predict)
  6. Non-idiosyncratic (aware patient has an issue)
43
Q

What is interventional radiologist?

Give an example of when it can be used.

A

Minimally invasive, image-guided treatments.

Used to remove a blood clot causing a stoke

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