Advanced TP

Question 1

What are the two types of motion?

Answer 1

• physical: respiration and cardiac motion (systematic)

- violitional: swallowing and couhing (random)

Question 2

What is intrafraction motion?

Answer 2

• movement of patient during a single fraction
• main focus of 4D applications
• 4DCT

Question 3

What is inerfraction motion?

Answer 3

• motion between fractions
• organ filling/emptying variations
• adaptive therapy

Question 4

What are the benefits of controlling motion?

Answer 4

• tumour margins decreased
• OAR sparing
• potential dose escalaiton
• improve clinical outcomes

Question 5

What are some motion management solutions?

Answer 5

• vacbag

- breathing control (ABC, RPM, compression belt)

Question 6

What is 4DCT?

Answer 6

• aquisition of multiple images at slice positions, each tagged with breathing signal
• images are sorted based on breathing signal

Question 7

4D vs 3D imgaing?

Answer 7

• 4D allows full tumour trajectory tracking

- 3D gives partial tumour trajectory (inspiration, expiration)

Question 8

What is MIP?

Answer 8

• maximum image projectory
• displays the max no. of all pixels at the same locatin over the respiratory cycle
• shows entire extent of tumour motion
• caution for tumour close to diaphragm and chest wall

Question 9

What is MinIP?

Answer 9

• minimum image projectory
• displays the min no. of all pixels at the same sptial location over the respiratory cycle
• shows where some of the tumour always is
• useful for liver tumours that present at low density

Question 10

What is AvgIP?

Answer 10

• average image projectory
• displays the avg no. of all pixels at the same sptial location over the respiratory cycle
• considered appropriate for planning which reduces the need for additional scan and thus dose

Question 11

What is MLC interplay?

Answer 11

• relationship between the leaves and target
• in normal treatment the effect is averaged out over 30 fractions, but with one fraction the clinical outcome of inteplay could be huge

Question 12

What is the benefit of variable dose rate?

Answer 12

• decrease dose rate and increase linac when going through OAR and increase dose rate and slow linac when going through tumour

Question 13

What is a specialty Image Set?

Answer 13

• feature that combines 2 or more image sets to make a specialty image
• e.g. MIP, MinIP, AvgIP