Radiology 1: Intro to Clinical Imaging

Question 1

Give some benefits of digital x-ray recording over manual

Answer 1

• Post exposure manipulation reduced the need for repeated exposures
• Films won’t go missing
• Films easily shared with relevant people (national database)

Question 2

Describe the production of an x-ray image

Answer 2

x-rays are produced

The beam passes through the patient

The intensity of the x-rays incident of the is recorded

Question 3

Describe the relationship between tissue density and x-ray transmission

Answer 3

The denser the tissue, the fewer x-rays are transmitted

The less dense the tissue, the more x-rays are transmitted

Question 4

Describe the effect incident x-rays have on the x-ray film

Answer 4

Incident x-rays turn the x-ray film black

More x-rays –> More black
Less x-rays –> Lighter

Question 5

Describe the proportion x-rays that are transmitted through:

Air, soft tissue, cortical bone

Answer 5

Air - all x-rays (nearly)

Soft tissue - some

Cortical bone - none

Question 6

Describe the strengths of x-rays, and give an example of its use

Answer 6

They show denser objects surrounded by air very well
e.g.
Tumours or fluid in the lungs

They show less dense areas surrounded by very dense areas well
e.g.
A bone fracture, bone cancer

Question 7

Describe a the major weakness of an x-ray image

Give an application of this weakness

Answer 7

To be visible and distinguishable on an x-ray image the structures must be of significantly different density

e.g. soft tissues are imaged very poorly

Question 8

Describe what is meant by a contrast study

Answer 8

Where a liquid containing dense elements is applied between tissues, or inside tissues allowing them to become visible to x-rays

Question 9

Give 2 examples of contrast studies

Answer 9

Enemas and arthrograms

Question 10

Describe the danger of x-rays to the patient and operators

Answer 10

The radiation can damage cell DNA causing mutations, leading to cell death or cancer

Question 11

How can the risk to patients from x-rays be minimised?

Answer 11

By minimising the dose

Make sure the benefit outweigh the risk

Question 12

Describe how a CT image is taken

Answer 12

Same as an x-ray image, except that x-rays are fired from all around the body

Question 13

Describe another weakness of an x-ray image

Answer 13

As the x-rays come from 1 direction structure are superimposed

Question 14

Describe the main benefit of CT over x-ray images

Answer 14

CT images do not have superimposition as x-ray images do

Question 15

Of CT and x-rays which has a greater contrast resolution

Answer 15

CT

Question 16

Describe the sort of view provided by a CT scan

Answer 16

Cross-sectional

Question 17

What is the main negative of a CT scan over an x-ray

Answer 17

CT scans give far greater doses of ionising radiation

Question 18

Give a weakness of CT scans

Answer 18

Can’t distinguish between soft tissues of very similar densities

e.g.pelvic organs, muscles & tendons

Question 19

In an US (Ultrasound) scan what produces the pulses of sound waves

Answer 19

The transducer

Question 20

Why is jelly applied to the skin for US scans

Answer 20

To assist with the transmission of sound into the body

Question 21

How does an ultrasound scan work?

Answer 21

The transducer emits pulses of sound

The returning sound is detected and fed to a computer

Question 22

How is the US image produced?

Answer 22

The time taken for the sound to return to the transducer is used to build a cross-sectional image

Question 23

What type of tissue does US image best

Answer 23

Soft tissues

Question 24

What are the ideal conditions for a US scan?

Answer 24

Lots of sound reaches and returns from the tissue:

good skin contact, little fat (slim patient), the viewed structure is superficial

Tissues with different acoustic properties are being viewed

Question 25

What is a US scan good for viewing?

Answer 25

Solid structures surrounded by fluid

Tendons and muscles

Abnormal fluid collections

Tissues with different acoustic properties (e.g. soft tissue tumours)

Question 26

Describe the weaknesses of US scans

Answer 26

• They can see past bone as it reflects the sound back
  e. g. can’t see the brain, or bone marrow
• Fat patients are harder to image
• Gas blocks US, gas containing structure can’t be assessed
  e. g. can’t see lungs or bowel

Question 27

How does a MRI scan work?

Answer 27

The scanner produces radio waves that effect the body’s protons

The scanner then detects a signal from the protons

From this an image is produced

Question 28

Describe why an MRI scan can be dangerous

Answer 28

It is loud

Its magnetism can move certain metals causing:

• Projectiles
• Damage to internal tissue from internal metals (e.g. shrapnel)

Question 29

How long do MRI scans take?

Answer 29

A long time (25-60mins)

Question 30

Describe the strengths of MRI scans

Answer 30

Very good at imaging the brain

Can accurately asses muscle and tendon tears
(especially in deep tissue where US is less accurate)

Great detail of spinal canal disease

Great for imaging the interior of joints

Question 31

Describe the weaknesses of MRI scans

Answer 31

Expensive

Potentially dangerous

Takes a long time (bad for those who need monitoring or are unstable)

Some find it claustrophobic

Question 32

Describe the roles of clinical imaging

Answer 32

Help make/confirm differential diagnosis

To stage a diseases progression

To monitor treatments effectiveness

Question 33

Name a region that MRI images poorly

Answer 33

The lungs

Question 34

What is an image guided procedure?

Answer 34

A procedure where the surgeon is guided by imaging