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Treatment Planning > Lung > Flashcards

Lung Flashcards

1
Q

what is increase in dose beyond healthy lung tissue?

A

2%/cm of lung for 10 MV beam

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2
Q

immobilization and breathing management

A

wing board
va-lock bag
compression
repiratory tracking, gating, DIBH

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3
Q

how does 4DCT work

A

IR fiducial marker is placed on patient abdomen to track breathing motion. At each slice, the CT scanner acquires images for the full breathing cycle. These are then binned into 10 bins according to the breathing motion recorded from the tracker.

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4
Q

pitch in CT

A

pitch = L/NT, L is distasnce travelled by the couch between slices, N is number of detectors, T is slice thickness
pitch > 1 is undersampled
pitch < 1 is oversampled

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5
Q

MIP and AIP

A

maximum intensity projection- captures full range of motion - contour target here
-for MIP, assign each pixel the max HU value for that pixel based on all phases
average intensity projection- average value in each pixel-contour OARs here

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6
Q

does MIP include all breathing phases?

A

Only the ones that will be used for treatment

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7
Q

2 types of gating

A

amplitude based - amplitude of breathing trace is within certain bounds
phase based - based on breathing cycle phase

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8
Q

lung 3DCRT imaging

A

kV orthos

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9
Q

typical fractionations

A

66/33 (same as 60/30 without heterogeniety correction)
45/30 BID - SCLC
40/15 - SCLC
60/30 RT alone, 60/15 for chemorads

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10
Q

max energy to use in lung per TG 65

A

12 MV

-favour lower energies because difficult to get build-up in lung with higher energy (longer penumbra)

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11
Q

common CTV and PTV margin

A

CTV- 0.5-cm

PTV- 0.5-1.5 cm

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12
Q

common lung constraints

A

MLD< 18 Gy (but 7 Gy should be do-able)

V20Gy < 20 %

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13
Q

esophagus constraint

A

Dmean < 34 Gy (2 Gy fx)

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14
Q

spinal cord constraint

A

Dmax < 50 Gy for PRV (2 Gy fx)

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15
Q

brachial plexcus constraint

A

Dmax < 60 Gy

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16
Q

heart constraint

A

Dmean < 26 Gy
Dose to pacemaker below 2 Gy
2 Gy fx

17
Q

liver constraint

A

Dmean < 30 Gy

2 Gy fx

18
Q

kidney constraint

A

Dmean < 15 Gy

2 Gy fx

19
Q

what happens to OAR constraints when RT combined with chemo?

A

constraints are more stringent

20
Q

what is pulmonary fibrosis

A

shrotness of breath (dyspnea) due to scarred tissue

21
Q

which os NSCLC and SCLC responds better to RT and chemo?

A

SCLC

10-15 % of lung cancer

22
Q

3 types of NSCLC

A

adenocarcinoma
squamous cell carcinoma
large cell carcinoma

23
Q

mets are common in brain. What is used to reduce the chance of this?

A

prophylactic cranial irradiation

24
Q

typical 3DCRT beam arrangement

A

K

avoid going through spinal cord and a lot of lung tissue

25
Q

difference between correcting for inhomogeneities for primary beam only vs for primary beam and scatter

A

-primary beam only won’t show lateral bulging of isodose lines in lung- correcting for primary and scatter will

26
Q

lung density and effective Z

A

0.3 g/cm3

7

27
Q

Report on inhomogeneity corrections

A

TG65

28
Q

spinal cord PRV constraint for 3 Gy fx

A

Dmax < 33Gy

29
Q

spinal cord PRV constraint for 4 Gy fx

A

Dmax < 22 Gy

30
Q

spinal cord PRV constraint for 40/15

A

35 Gy

31
Q

spinal cord PRV constraint for 45/30 BID

A

42 Gy

32
Q

HART and CHART and results

A

Hyperfractionated accelerated RT (HART) or continuous hyperfractionated accelerated RT (CHART)
-the therapeutical ratio increases with increasing dose per fraction in the cases of higher prescription dose and small target volume, while it increases with decreasing dose per fraction in the cases of lower prescription dose and large target volume

33
Q

lung window level settngs

A 
W = 400 to 1600
L= -400 to -600
34
Q

normal lung volume

A

lung-Gtv

35
Q

What is PET used for with lung?

A

-differentiate collapsed lung from disease- cannot see with CT

36
Q

concern of using IMRT in lung cancer

A

interplay effect

37
Q

what is min projection from 4DCT used for?

A

-negative contrast (like liver)

38
Q

if there is extreme mtion is it better to gate or track?

A

Gate because tracking will expose more healthy lung to dose

39
Q

describe K shape in lung

A

avoids going through cord

comes in through heart and ipsi lung

Treatment Planning (17 decks)

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