Non-coplanar

Question 1

What is non-coplanar technique

Answer 1

When couch is rotated
Allow change of beam entry and exit

Question 2

Rationale for NCP planning

Answer 2

useful where transverse plane beams would enter or exitthrough an OAR.
▪ Can offer a Non-IMRT solution on tricky beam arrangements.
▪ Minimal technology (MLC)
▪ ‘Minimal’ time commitment
▪ NCP beam arrangements lowering dose to the Non-Target
Tissue(NTT)
avoids overlap of beams
best homogeneity with maximal sparing

Question 3

NCP Beam arrangement

Answer 3

easy to determine best angles : evaluate your dose distribution without wedges, decide which wedge to use and size

Question 4

clinical example for NCP brain

Answer 4

rt lat - couch 0, gantry 270
rt ant ob - couch 0, gantry 45
sup oblique - couch 270, gantry 45-55

Question 5

NCP disadvantages

Answer 5

higher plan complexity
risk of collision
easy to introduce some errors
Workflow in busy departments

Question 6

REV

Answer 6

Assist is checking wedge placement.
▪ Assist in checking collision with
gantry.
▪ Checking patient orientation.

Question 7

Rationale for FIF

Answer 7

Useful in situations where the high dose region needs to be somewhere that awedge can’t position it.
▪ Such as in the field centre

Homogeneity is better
• Can be used to improve target coverage
less MUs

Question 8

FIF shielding approaches

Answer 8

1. Jaw shifts - move inf/sup jaw to shield hot region
   
   2. MLC fields
      A combination of two

Question 9

How to improve target coverage

Answer 9

Subfields – Boost fields can be used
• Concomitant boost as a subfield within
each tangential beam
• These sub-fields would need
prescribing separately

Question 10

FIF considerations

Answer 10

Do not shield to RP unless dose is prescribed to a volume
Keep weighting small for small fields
✓ Min MUs- 6 per sub field
✓ Min field size is 3 x 3 cm

Question 11

How to design beam segments

Answer 11

1. Option 1: Define segments using dose volumes as ROIs
2. Option 2: Draw segments on 3D DRR displays
3. Option 3: Draw segments on 2D BEV displays
4. Option 4: Define segments using asymmetric jaws
5. Option 5:Define segments using variable block margins

Question 12

Clinical use of NCP Breast

Answer 12

LAO: Couch 340-345, gantry 55-65
RPO: Couch 0, Gantry 200-230
Post: Couch 0, gantry 180