MLCs

Question 1

What are the advantages and disadvantages of dynamic IMRT?

Answer 1

• ADV = faster delivery than static. Achieves more complex dose dist, smoothes dose across target volume
• DIS = inverse planning required, more difficult to recover from beam interruptions, difficult to verify leaf positions

Question 2

What does VMAT stand for?

Answer 2

Volumetric modulated arc therapy

Question 3

VMAT dose rate and gantry speed varies? WHY?

Answer 3

As arc moves, faster = lower dose rate (over OAR). Slower = higher dose to PTV

Question 4

What are disadvantages of VMAT?

Answer 4

• Set up accuracy
• Awareness of patient movement
• Need to have full clearance, e.g breasts with both arms up