Monaco IMRT VMAT

Question 1

What are standard physician contours for prostate cancer?

Answer 1

CTV 78Gy (Prostate Prostate and SVs)

PTV 78Gy 0.7-1cm margin (0.5cm post margin)

Question 2

What are common contouring tools (Monaco)

Answer 2

Pencil
Paint brush
Auto threshold
Ez sketch

Question 3

What is the scan reference point?

Answer 3

Intersection of BBs and is used to shift to isocentre

Question 4

Why do we force ED values for the treatment couch?

Answer 4

To ensure that the correct attenuation factor is used to determine the dose delivered to the patient

Question 5

What is the purpose of Fill ED?

Answer 5

To reduce artefact within the CTV

Raises ED within this region to specified value

Question 6

What is a sector?

Answer 6

The increment value that splits the beam into a series of sectors

Question 7

What is a clinically acceptable dose grid?

Answer 7

0.25cm, the smaller the dose grid more accurate larger calculation time

Question 8

What are the two types of statistical uncertainty?

Answer 8

Per control point

Per calculation

Question 9

What is statistical uncertainty per control point?

Answer 9

is the percent (%) statistical uncertainty per voxel, on a per-segment basis, that you are willing to accept for the final dose calculation

Question 10

What is the recommended statistical uncertainty?

Answer 10

<1.5% per calculation

<5% per control point

Question 11

What are the characteristics of SSO?

Answer 11

Increased plan quality, optimisation time and MU

Decreased number of segments, treatment time

Question 12

What are common IMRT sequencing parameters?

Answer 12

Min SA 2cm
Segment width 0.5cm
Minimum MU 5MU
Max segments 250

Question 13

What are the impacts of increased fluence smoothing?

Answer 13

Higher MU

Reduced plan quality

Question 14

Types of fluence smoothing?

Answer 14

Off: Creates many segments Low: Creates more segments (use for complex plans) Medium: Creates an average number of segments (use for less complex plans) High: Creates few segments

Question 15

What is machine interdigitation?

Answer 15

Closed leaf gaps are placed inside the fluence map, which makes more efficient segments. Monaco optimizes dose leakage through the gaps and adds it to the total dose delivered by the plan

Question 16

What are common VMAT parameters?

Answer 16

Max number of arcs 1-4
Range of control points per arc 2-180 (120 prostates, 150-180 H and N)
Min segment width 0.5-2

Question 17

What is a standard target margin?

Answer 17

0.8mm and smaller reduce target coverage

Question 18

What does structure layering achieve?

Answer 18

Dictates voxel allocation

Question 19

What are objectives?

Answer 19

are anatomy-specific functions that establish dose and/or biological response goals. o Target penalty and EUDs are objectives.

Question 20

What are constraints

Answer 20

oare anatomy-specific functions that must be met. oare often referred to as hard constraints. oSerial and Parallel are biological cost functions and are ‘Constraints’.
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Question 21

What is a target penalty?

Answer 21

cost function
objective version of quadratic underdose for targets
DVH parameter

Question 22

What is a Quadratic overdose

Answer 22

a constraint
limits high doses
manage dose excess using RMS

Question 23

What is target EUD?

Answer 23

Higher cell sensitivity = increased penalty paid for cold spots • Lower sensitivity = increase the pressure to deliver dose to cold spots

common cell sensitivity 0.5

Question 24

What is a Quadratic Underdose?

Answer 24

Physical constraint acts as a minimum dose

Question 25

What is an Overdose DVH?

Answer 25

A physical cost function equivalent of a DVH constraint | controls a single point of DVH

Question 26

What is a underdose DVH?

Answer 26

Physical cost function for DVH used for target

Question 27

What is biological EUD?

Answer 27

EUD is a homogeneous dose that, when applied to an organ, has the same clinical effect as any given, inhomogeneous dose distribution Small k value means a large volume-effect is assumed

Question 28

What is a serial function?

Answer 28

Biological constraint that effects multiple points of DVH

Question 29

What is a parallel function?

Answer 29

effect on a DVH at multiple poinnts, larger the arrow the harder the function is working

Question 30

What is the purpose of a conformality function?

Answer 30

The purpose of the Conformality cost function is to shape the high dose volume tightly around one or several target volumes starts working 4cm from target up to 8cm

Question 31

What is the purpose of a shrink margin

Answer 31

nable the voxels near the targets and other OARs to have a “transition zone” between competing cost functions (0.6cm)

Question 32

What are two optimisation types?

Answer 32

Constrained (OAR then targets) | Pareto (Targets then OAR)

Question 33

What are the two stages of Monaco optimisation?

Answer 33

Fluence optimisation | SSO

Question 34

What is HI?

Answer 34

The Heterogeneity Index (HI) describes the uniformity of dose within a target volume and is directly calculated from the statistics of the DVH.

Question 35

What is CI?

Answer 35

The Conformity Index (CI) describes the degree to which the prescribed isodose volume conforms to the shape and size of the target volume.