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Last sem > Monaco IMRT VMAT > Flashcards

Monaco IMRT VMAT Flashcards

1
Q

What are standard physician contours for prostate cancer?

A

CTV 78Gy (Prostate Prostate and SVs)

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

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2
Q

What are common contouring tools (Monaco)

A

Pencil
Paint brush
Auto threshold
Ez sketch

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3
Q

What is the scan reference point?

A

Intersection of BBs and is used to shift to isocentre

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4
Q

Why do we force ED values for the treatment couch?

A

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

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5
Q

What is the purpose of Fill ED?

A

To reduce artefact within the CTV

Raises ED within this region to specified value

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6
Q

What is a sector?

A

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

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7
Q

What is a clinically acceptable dose grid?

A

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

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8
Q

What are the two types of statistical uncertainty?

A

Per control point

Per calculation

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9
Q

What is statistical uncertainty per control point?

A

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

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10
Q

What is the recommended statistical uncertainty?

A

<1.5% per calculation

<5% per control point

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11
Q

What are the characteristics of SSO?

A

Increased plan quality, optimisation time and MU

Decreased number of segments, treatment time

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12
Q

What are common IMRT sequencing parameters?

A

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

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13
Q

What are the impacts of increased fluence smoothing?

A

Higher MU

Reduced plan quality

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14
Q

Types of fluence smoothing?

A

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

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15
Q

What is machine interdigitation?

A

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

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16
Q

What are common VMAT parameters?

A

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

17
Q

What is a standard target margin?

A

0.8mm and smaller reduce target coverage

18
Q

What does structure layering achieve?

A

Dictates voxel allocation

19
Q

What are objectives?

A

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

20
Q

What are constraints

A

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’.
13

21
Q

What is a target penalty?

A

cost function
objective version of quadratic underdose for targets
DVH parameter

22
Q

What is a Quadratic overdose

A

a constraint
limits high doses
manage dose excess using RMS

23
Q

What is target EUD?

A

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

24
Q

What is a Quadratic Underdose?

A

Physical constraint acts as a minimum dose

25
Q

What is an Overdose DVH?

A

A physical cost function equivalent of a DVH constraint

controls a single point of DVH

26
Q

What is a underdose DVH?

A

Physical cost function for DVH used for target

27
Q

What is biological EUD?

A

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

28
Q

What is a serial function?

A

Biological constraint that effects multiple points of DVH

29
Q

What is a parallel function?

A

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

30
Q

What is the purpose of a conformality function?

A

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

31
Q

What is the purpose of a shrink margin

A

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

32
Q

What are two optimisation types?

A

Constrained (OAR then targets)

Pareto (Targets then OAR)

33
Q

What are the two stages of Monaco optimisation?

A

Fluence optimisation

SSO

34
Q

What is HI?

A

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

35
Q

What is CI?

A

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

Last sem (6 decks)

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