L21: imaging of the head & neck

Question 1

Describe CT scans

Answer 1

Uses a combination of x-rays to obtain images
The denser the tissue, the more x-rays are absorbed & so fewer x-rays reach the detector = appear white
Structures that are less dense – no or fewer x-rays are absorbed -> more x-ray radiation reaches the detector = appear black

Question 2

Describe the uses of different imaging modalities in head and neck

Answer 2

Plain radiographs – visualising bony structures
CT scans – bone, soft tissue & brain to be viewed in detail
MRI scans – used to further investigate pathology seen on eg. CT (tumour)
US – thyroid and superficial soft tissue only

Question 3

List the advantages and disadvantages of ultrasounds

Answer 3

Advantages: cheap, no ionising radiation
Disadvantages: operator dependent, limited by bone

Question 4

List the advantages and disadvantages of x-rays

Answer 4

Advantages: cheap, readily available, low radiation
Disadvantages: not helpful viewing any other tissue except bone, 2D images, low contrast

Question 5

List the advantages and disadvantages of CT scans

Answer 5

Advantages: 3D images, cross-sectional views, bone, soft tissue, brain viewed in detail
Disadvantages: higher dose of radiation than x-ray

Question 6

List the advantages and disadvantages of MRI scans

Answer 6

Advantages: can see soft tissue in more detail than CT, no radiation
Disadvantages: more expensive, noisy, takes much longer, no metallic foreign bodies