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Science for Medicine COPY > Introduction to Imaging > Flashcards

Introduction to Imaging Flashcards

1
Q

Why is imaging used?

A

Physical examination is unreliable

Different tests are good for different things

Faster diagnosis

Assess response to treatment

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2
Q

What is triage?

A

Identify who is going to benefit most from surgery and other treatment

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3
Q

What is screening?

A

Identify diseases at an early stage to intervene

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4
Q

What is an X-ray?

A

Electromagnetic packet of energy with a short wavelength between 0.1 and 10nm

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5
Q

What can an atom be defined by?

A

Mass number A

Atomic number Z

Nucleus

Electrons

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6
Q

What is the mass number?

A

Amount of protons and neutrons

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7
Q

What is the atomic number?

A

Amount of protons

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8
Q

Where do gamma rays come from?

A

The nucleus

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9
Q

What are the layers of electrons around the nucleus known as?

A

Inner and outer shell

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10
Q

What causes the electrical and chemical properties of an atom?

A

Outer shell of electrons

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11
Q

What is responsible for the production of X rays?

A

Inner shell of electrons

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12
Q

How does an X ray work?

A
  1. Cathode heated to 2200oC to produce a stream of electrons
  2. Travel to T which is positively charged, crossing a vacuum
  3. 0.1% of energy creates X rays, rest is heat, rotar (r) and S makes sure the disk spins quick
  4. O and E controls the heat and B allows it to expand
  5. X rays travel down the LED glass/window
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13
Q

What does the intensity of the X ray depend on?

A

Tube current

Atomic number of target

Tube voltage

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14
Q

What are the 3 paths of an X ray once it interacts with matter?

A

Absorption

Transmission

Scatter

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15
Q

What is attenuation?

A

Process by which radiation loses power as it travels through matter and interacts with it

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16
Q

What does attenuation depend on?

A

Atomic number

Density

Thickness

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17
Q

How do X rays interact with air?

A

Travel all the way through

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18
Q

How do X rays interact with a tooth?

A

Most absorbed, some travels straight through

19
Q

How to X rays interact with the abdomen?

A

Complex due to gas, tissue and bone

20
Q

What is X ray film composed of?

A

Luminescent screen

Film emulsion

Luminescent screen

21
Q

What does the film emulsion contain?

A

Silver halide which clumps after exposure to light generated on luminescent screen

22
Q

What speed and frequency does ultrasound travel through the body at?

A

Speed of 1540m/s

Frequency of 1-20MHz

23
Q

How does ultrasound generate an image?

A

Some waves are reflected which is detected and used to generate an image

24
Q

Why is jelly used with ultrasound?

A

Because you need tight acoustic coupling

25
Q

What are the advantages of ultrasound?

A

Cheap

Portable

No radiation

26
Q

How do lower frequency and higher frequency ultrasound waves differ?

A

Lower frequency travels further but is less detailed

27
Q

What is barium?

A

A radio opaque contrast agent used for outlining the GI tract

28
Q

Why does barium absorb more X rays than the surrounding tissues?

A

High atomic number

29
Q

When is barium dangerous?

A

When it leaks out of the bowel

30
Q

How does a CT scan work?

A

Rotating X ray tube

Uses multiple beams

31
Q

What are CT scans great for?

A

Bony detail

32
Q

What is a disadvantage of a CT scan?

A

Exposure to radiation

33
Q

What is radiation?

A

Process of emitting energy in the form of particles or waves

34
Q

What is ionising radiation?

A

Particle or wave with sufficient energy to ionise a neutral molecule

35
Q

What are different types of radiation?

A

Alpha particle (2n and 2p)

Beta particle (e- or +)

Photons (X or gamma ray)

36
Q

What are alpha particles stopped by?

A

Paper

37
Q

What are beta particles stopped by?

A

Hand

38
Q

What are photons stopped by?

A

Concrete

39
Q

What is a seivert?

A

A unit used for describing the absorption of radiation by the human body

40
Q

How much radiation do we typically absorb per year?

A

2.4mSv/year

41
Q

What kinds of cell damage does ionising radiation lead to?

A

Repair

Cell death

Transformation

42
Q

How can exposure to radiation be reduced?

A

Reducing time exposed

Increasing distance

Using protection

43
Q

What can you say about types of tests and the increased risk of developing cancer?

A

Different tests have different risks of developing cancer in your lifetime

Body CT has the most and dental X ray has the least

Science for Medicine COPY (55 decks)

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