Introduction to Medical Imaging

Question 1

Name two types of medical imaging techniques

Answer 1

Ionising radiation techniques

Non-radiation techniques

Question 2

What are different types of ionising radiation techniques?

Answer 2

Plain Radiographs (x-rays)
Computer Topography
Fluoroscopy
Nuclear Medicine

Question 3

What are different types of non-radiation techniques?

Answer 3

Magnetic Resonance Imaging (MRI)

Ultrasonography (Ultrasound)

Question 4

Which parts of the electromagnetic spectrum is considered to be ionising?

Answer 4

X-rays and gamma rays as they have high energies

Question 5

Why is ionising radiation harmful?

Answer 5

It carries enough energy to free electrons from atoms or molecules, thereby ionising them

Question 6

What are the two units of radiation?

Answer 6

Sievert (mainly measured in mSv)

Gray

Question 7

What are Sieverts used to measure?

Answer 7

Diagnostic doses of radiation

Question 8

What are Grays used to measure?

Answer 8

Therapeutic doses of radiation

Question 9

What’s the average background radiation dose for a UK citizen?

Answer 9

2.5 mSv

Question 10

Why is good image contrast important in imaging procedures?

Answer 10

The imaging technique will emphasize certain contrast characteristics of anatomical structures and allow us to differentiate the structures and determine which structures are abnormal.

Question 11

What causes the different colours on X-Rays?

Answer 11

Denser materials block rays from reaching the film, leaving it white. X-rays pass through less dense tissue to the film, resulting in more blackening of the film

Question 12

Positives of x-rays

Answer 12

Fast 
Non-invasive
Painless
No special prep required
No recovery time

Question 13

Negatives of x-rays

Answer 13

Radiation risk
Image quality can be low
Distortion
Not good for soft tissues
Inappropriate during pregnancy

Question 14

Positives of CT scans

Answer 14

Fast
Non-invasive 
Painless 
No special prep required
No recovery time
Better for soft tissues

Question 15

Negatives of CT scans

Answer 15

Inappropriate during pregnancy
Contrast Issues
Higher Radiation risk

Question 16

Why are CT scans able to produce transverse images?

Answer 16

It uses 360° focused X-rays

Question 17

Why are contrast mediums used?

Answer 17

They are used to examine structures that do not have inherent contrast differences

Question 18

Define radiopaque

Answer 18

A substance that’s opaque to X-rays or similar radiation.

Question 19

Define radiolucent

Answer 19

A substance that’s transparent to X-rays

Question 20

Give two examples of contrast mediums

Answer 20

Barium meal

Angiography

Question 21

Positives of contrast mediums

Answer 21

Excellent differentiation of tissues

Sequential images – follow through

Question 22

Negatives of contrast mediums

Answer 22

Special Preparation
Adverse Reactions
Recovery Time
Invasive
Slower
Transverse

Question 23

What’s CT short for?

Answer 23

Computer Tomography

Question 24

Describe the science behind MRIs

Answer 24

Certain atomic nuclei can absorb and emit radio frequency energy when placed in an external magnetic field. Hydrogen atoms exist naturally in people and animals in abundance, particularly in water and fat and have their own magnetic moments

Question 25

MRI scans map the location of what in the body?

Answer 25

Water and fat

Question 26

Positives of MRI scans

Answer 26

``` Excellent differentiation of tissues Sequential images – follow through Any plane Images structures better without contrast Non invasive Detect abnormal tissues No risk to “normal” patient No radiation ```

Question 27

Negatives of MRI scans

Answer 27

Scans take longer Remain completely still (hold breath) Bowel movements and heart always in motion Distortion from metallic implants, fillings Cost

Question 28

What do ultrasound scans use to create the images?

Answer 28

High frequency sound waves, which create echoes/reflections

Question 29

Positives of ultrasound

Answer 29

``` Quick Low cost Portable No radiation Risk free Use on “high risk” patients Live feedback – not static Biopsy ```

Question 30

Negatives of ultrasound

Answer 30

Varying quality Unable to cross tissue-gas or tissue-bone boundary Gas containing structures can obscure deeper tissues High degree of technical skill

Question 31

Define the term 'stochastic effects'

Answer 31

Effects of radiation that occur on a random basis, independent of the size of the radiation size

Question 32

Define the term 'non-stochastic effects'

Answer 32

Effects of radiation that have a clear relationship between the exposure and the effect. The magnitude of the effect is directly proportional to the size of the dose