Monaco 2 Flashcards
Monaco is a
Voxel based planning system
What is the advantage of voxel based planning
Can define the voxels you want to control instead of controlling the structure
What is a possible disadvantage voxel based planning?
If 50% or more voxels are inside the contour, the planning system considers it to be part of the structure (e.g. rectum in prostate)
What are the voxels dependant on?
Grid size and thickness of slices
Stage 1 Op
Fluence optimisation
Stage 2 Op
Segmentation and dose calculation
What energy would you use to treat pancreas?
Provide (2) reasons why this energy is ideal
6MV - small volume and close proximity to bowel (has air) the pneumbra increases
- can consider Monaco planning system (6MV is faster computation)
How many arcs?
2 Arcs
What collimator angles to use?
Complement angles (5-15 degrees)
How does increasing arc increment affect the plan quality?
Degrades plan quality
What happens when you decrease arc increment size>
Introduces more sectors and increases planning time (doesn’t necessarily improve quality)
SSO?
Segment shape optimisation
What does SSO do?
Improves plan quality and deliverability
What does SSO increase (3)
Optimization time
Plan quality
MUs
What does SSO decrease (2)
Delivery time
Segment #
For a complex plan what fluence smoothing option would you use?
Low as this creates more segments
What is the effect of increasing statistical uncertainty?
increases noise and degrades plan quality
3% is the recommendation
Pareto mode
Prioritizes target underdoses on tumour volumes and relax constraints on healthy tissue
OARS>Targets
Constrained mode
Sets constraints on healthy tissue while administers dose to target volumes.
Targets>OARs
What cost function can be used for target structures
Target EUD & Target penalty (works as a minimum dose) Quadratic overdose (works as a maximum dose with RMS allowing for leeway with dose excess)
What cost functions can be used for OARs
Biological parallel and serial
Tradiational DVH
What cost functions are used for dose outside of targets and OARs
Quadratic overdose
Conformality
Define EUD
Dose that causes the same effect if applied homogenously to the entire organ volume (any two or more dose distributions that yield the same radiobiological effect)
Isoconstraint?
Value defined by user
Isoeffect?
Calculated EUD
Rule of thumb for determining k value in serial
k = 0.15 x D50
When is conformality cost function useful (2)
Single target volumes and steroetactic volumes where there are large areas of unspecified tissue
Shaping high dose volume tightly around one or more target volumes
When would conformality cost function not be useful
Complex plans where there is several overlapping structures (head and neck)
When hotspot is outside of margin >8cm away
What is batch optimisation?
Automatic Stage 1 to Stage 2 (can pause)
Define a control point
Defines the movement of MLC during treatment delivery from start to end of each segement
