MONACO Flashcards
What kind of TPS is Monaco
Voxel based
Meaning you can control voxels but not structures
If 50% of voxel is inside the contour, Monaco considers it to be a part of the structure
Voxels
Extend from iso and are based of grid size
Finer the grid size, greater number of voxels
Workflow of Monaco planning
- Import the studyset(s) and assign the CT to ED.
- Open the patient in the workspace.
- Fuse multiple studysets.
- Carefully contour all required targets and OARs. Create necessary margins.
- Define and lock scan reference point.
- Import applicable treatment devices.
- Start a Monaco plan (load a plan template).
- Verify/edit beam geometry, isocentre, machine and energy.
- Verify/edit prescription.
- Verify/edit electron densities and structure layering order.
- Resolve any structure mismatches and edit the IMRT Constraints, Calculation
Properties, IMRT Parameters, and Sequencing Parameters as necessary. - Run fluence optimization (Stage one).
- Use plan analysis tools to evaluate your plan.
- Adjust the parameters and prescription (constraints) as necessary.
- Re-optimize the fluence and repeat evaluation until you have an acceptable
optimized plan. - Run segment optimization (Stage two).
- Use the plan analysis tools to evaluate your final plan
- If the plan is not acceptable, make edits to the properties and/or prescription
(constraints) as needed. - Verify plan meets all objectives.
- Save and name plan.
- Request proper plan approval.
- DICOM export all necessary data.
- Export plan PDF.
- Create a QA plan.
Arc increment
If you use an increment that is too large, Monaco creates fewer sectors.
• This can produce poor quality plans. When you use an increment that is too
small, Monaco gives you more sectors.
Use rule of 3 - add 3 to the number of static beams
Partial arc sector
the system selects the closest
increment value that is uniformly divisible with the
posterior arc increment split into two.
Sweep sequencer
Sweeping leaf sequencer is that the leaves move from
their start position to their end position in a continuous,
unidirectional manner
• The length they do this is determined by the sector
• Beginning with the first sector, the leaves move to the left
side of the BEV
• They then change direction and move to the right side of
the BEV
• The minimum width of these end segments is hard coded
at 5mm.
Segment shape optimisation SSO
Segment Shape Optimization includes smoothing,
sequencing (clustering) and optimization of beam
weights and shapes.
• Range 1 to 20
Fluency smoothing
Controlled im stage 1
Increase smoothing leads to decreased plan quality and control points
Option of off, low, medium and high
Statistical uncertainty
the percent
(%) statistical uncertainty per voxel, on a per-segment
basis, that you are willing to accept for the final dose
calculation
Optimisation approaches
Constrained and Pareto
Constraint mode
set constraints on healthy tissue while it administers dose to
target volumes
Pareto mode
prioritizes target underdoses on tumour volumes and relax
constraints on healthy tissue. This effectively reverses how Monaco normally
works.
Cost functions
Target EUD
• Target Penalty
• Quadratic Overdose
• Parallel
• Serial
• Overdose DVH
• Underdose DVH
• Maximum dose
• Quadratic Underdose
• Conformality
EUD
The dose that causes the same effect if applied homogeneously to the
entire organ volume or
• The EUD represents any two or more dose distributions that yield the
same radiobiological effect.
Target EUD
Biological cost function
Default cell sensitivity of 0.5
Higher cell sensitivity = increased penalty paid for
cold spots
• high cell sensitivity = increase the pressure to deliver
dose to cold spots
Quadratic overdose
Physical cost function =constraint
To limit high dose
Isoconstraint is the root mean square
Can be used to control conformity
Parallel structure cost function
3 cost functions
The first parameter is the Reference Dose (Gy) whose
value is analogous to the dose that is only just
acceptable for the majority of the structure, and at which
a clear dose response begins to show
• The second parameter is the Isoconstraint, which is the
Mean Organ Damage (%) to the structure. The Mean
Organ Damage is the biological equivalent to the fraction
of the volume of the structure that can be sacrificed.
The third parameter is the Power Law Exponent (k). This
value changes the shape of the dose response curve and
determines how responsive the structure is to the Reference
Dose (Gy) and Mean Organ Damage (%) values entered.
K value
For parallel ranges from 1-4
• A k value of 1 with the Parallel cost function, applies its greatest penalty to the region of low
dose and applies a penalty over most of the curve
• A Parallel cost function with a k value of 4 applies penalty in the region of the reference dose.
Serial cost function
EUD
Biological equivalent of a max dose
Power law exponent
K=0.15*D50
Overdose DVH
This physical cost function is the equivalent of a
DVH constraint for an OAR.
When you add more than one DVH constraint to a
structure, the values for dose and percent (%)
volume must be consecutive so that they create a
single continuous curv
Underdose dvh
This physical cost function is the equivalent of a
DVH constraint for targets.
Should be cautious using this
Conformality
Physical cost function that can be used with OARs
Shapes high dose volume around 1 or more target volumes
Works well for single or stereotactic volumes
Does not work well with head and neck
Start at 1, range 0-1
Shrink margin
Instead of dose controlling ROIs
Surface margin
Use for tumours on the surface
Optimisation process
Stage 1: Produces the preliminary result “ideal” fluence distribution) so you can
evaluate how accurately the cost function(s) achieve the goals you set.
• Stage 2: The second stage performs the segmentation, which includes
optimizing the segment shapes and weights, so that deliverable fields are
obtained.
• Batch Optimisation -After stage 1 optimization and proceeds directly to stage 2
optimization
Control point
Control points describe the movement of the MLC during treatment delivery
from the start to the end of each segment.
