Introduction to Imaging

Question 1

Why is imaging used?

Answer 1

Physical examination is unreliable

Different tests are good for different things

Faster diagnosis

Assess response to treatment

Question 2

What is triage?

Answer 2

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

Question 3

What is screening?

Answer 3

Identify diseases at an early stage to intervene

Question 4

What is an X-ray?

Answer 4

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

Question 5

What can an atom be defined by?

Answer 5

Mass number A

Atomic number Z

Nucleus

Electrons

Question 6

What is the mass number?

Answer 6

Amount of protons and neutrons

Question 7

What is the atomic number?

Answer 7

Amount of protons

Question 8

Where do gamma rays come from?

Answer 8

The nucleus

Question 9

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

Answer 9

Inner and outer shell

Question 10

What causes the electrical and chemical properties of an atom?

Answer 10

Outer shell of electrons

Question 11

What is responsible for the production of X rays?

Answer 11

Inner shell of electrons

Question 12

How does an X ray work?

Answer 12

1. Cathode heated to 2200^oC 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

Question 13

What does the intensity of the X ray depend on?

Answer 13

Tube current

Atomic number of target

Tube voltage

Question 14

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

Answer 14

Absorption

Transmission

Scatter

Question 15

What is attenuation?

Answer 15

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

Question 16

What does attenuation depend on?

Answer 16

Atomic number

Density

Thickness

Question 17

How do X rays interact with air?

Answer 17

Travel all the way through

Question 18

How do X rays interact with a tooth?

Answer 18

Most absorbed, some travels straight through

Question 19

How to X rays interact with the abdomen?

Answer 19

Complex due to gas, tissue and bone

Question 20

What is X ray film composed of?

Answer 20

Luminescent screen

Film emulsion

Luminescent screen

Question 21

What does the film emulsion contain?

Answer 21

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

Question 22

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

Answer 22

Speed of 1540m/s

Frequency of 1-20MHz

Question 23

How does ultrasound generate an image?

Answer 23

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

Question 24

Why is jelly used with ultrasound?

Answer 24

Because you need tight acoustic coupling

Question 25

What are the advantages of ultrasound?

Answer 25

Cheap Portable No radiation

Question 26

How do lower frequency and higher frequency ultrasound waves differ?

Answer 26

Lower frequency travels further but is less detailed

Question 27

What is barium?

Answer 27

A radio opaque contrast agent used for outlining the GI tract

Question 28

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

Answer 28

High atomic number

Question 29

When is barium dangerous?

Answer 29

When it leaks out of the bowel

Question 30

How does a CT scan work?

Answer 30

Rotating X ray tube Uses multiple beams

Question 31

What are CT scans great for?

Answer 31

Bony detail

Question 32

What is a disadvantage of a CT scan?

Answer 32

Exposure to radiation

Question 33

What is radiation?

Answer 33

Process of emitting energy in the form of particles or waves

Question 34

What is ionising radiation?

Answer 34

Particle or wave with sufficient energy to ionise a neutral molecule

Question 35

What are different types of radiation?

Answer 35

Alpha particle (2n and 2p) Beta particle (e^- or +) Photons (X or gamma ray)

Question 36

What are alpha particles stopped by?

Answer 36

Paper

Question 37

What are beta particles stopped by?

Answer 37

Hand

Question 38

What are photons stopped by?

Answer 38

Concrete

Question 39

What is a seivert?

Answer 39

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

Question 40

How much radiation do we typically absorb per year?

Answer 40

2.4mSv/year

Question 41

What kinds of cell damage does ionising radiation lead to?

Answer 41

Repair Cell death Transformation

Question 42

How can exposure to radiation be reduced?

Answer 42

Reducing time exposed Increasing distance Using protection

Question 43

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

Answer 43

Different tests have different risks of developing cancer in your lifetime Body CT has the most and dental X ray has the least