Contouring

Question 1

What is the motivation for auto segmentation?

Answer 1

• interpretation of large data sets
• IMRT and VMAT increases contouring
• manual contouring is time consuming and prone in interobsever error

Question 2

What is the gold standard contouring method? Why?

Answer 2

• manual contouring
• clinical expertise and reasoning
• knowledge of spatial relationships, normal anatomy and patterns of diease

Question 3

What affects the outcome of manual contouring?

Answer 3

• window level
• image interpretation skills
• limitation due to image quality

Question 4

What is the threshold technique?

Answer 4

• upper and lower CT no. set

- usually applied to a 2D slice of a 3D data set

Question 5

What is threshold/autocontouring dependent on?

Answer 5

• image quality
• contrast between corresponding structures
• continous surface

Question 6

What is the body atlas based method?

Answer 6

• two step process
  1. reference image associated with atlas contours and matched to patient image (CT or CBCT)
  2. resulting deformation field used to morph atals contours to match patient image

Question 7

What is statistical shape modelling?

Answer 7

• do not rely soley on deformable registration maps

- incorporate a probalistic model of the organs

Question 8

What are the limitations of manual contouring?

Answer 8

• time consuming

- prone to intra and inter observe error

Question 9

What are the four classes of contouring tools?

Answer 9

• manual
• image greyscale interrogation
• body atlas based methods
• statistical shape modelling

Question 10

What are the two types of grey-scale interrogation?

Answer 10

• threshold technique

- model based segmentation (pinnacle)