Lung

Question 1

what is increase in dose beyond healthy lung tissue?

Answer 1

2%/cm of lung for 10 MV beam

Question 2

immobilization and breathing management

Answer 2

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

Question 3

how does 4DCT work

Answer 3

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.

Question 4

pitch in CT

Answer 4

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

Question 5

MIP and AIP

Answer 5

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

Question 6

does MIP include all breathing phases?

Answer 6

Only the ones that will be used for treatment

Question 7

2 types of gating

Answer 7

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

Question 8

lung 3DCRT imaging

Answer 8

kV orthos

Question 9

typical fractionations

Answer 9

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

Question 10

max energy to use in lung per TG 65

Answer 10

12 MV

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

Question 11

common CTV and PTV margin

Answer 11

CTV- 0.5-cm

PTV- 0.5-1.5 cm

Question 12

common lung constraints

Answer 12

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

V20Gy < 20 %

Question 13

esophagus constraint

Answer 13

Dmean < 34 Gy (2 Gy fx)

Question 14

spinal cord constraint

Answer 14

Dmax < 50 Gy for PRV (2 Gy fx)

Question 15

brachial plexcus constraint

Answer 15

Dmax < 60 Gy

Question 16

heart constraint

Answer 16

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

Question 17

liver constraint

Answer 17

Dmean < 30 Gy

2 Gy fx

Question 18

kidney constraint

Answer 18

Dmean < 15 Gy

2 Gy fx

Question 19

what happens to OAR constraints when RT combined with chemo?

Answer 19

constraints are more stringent

Question 20

what is pulmonary fibrosis

Answer 20

shrotness of breath (dyspnea) due to scarred tissue

Question 21

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

Answer 21

SCLC

10-15 % of lung cancer

Question 22

3 types of NSCLC

Answer 22

adenocarcinoma
squamous cell carcinoma
large cell carcinoma

Question 23

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

Answer 23

prophylactic cranial irradiation

Question 24

typical 3DCRT beam arrangement

Answer 24

K

avoid going through spinal cord and a lot of lung tissue

Question 25

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

Answer 25

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

Question 26

lung density and effective Z

Answer 26

0.3 g/cm3 | 7

Question 27

Report on inhomogeneity corrections

Answer 27

TG65

Question 28

spinal cord PRV constraint for 3 Gy fx

Answer 28

Dmax < 33Gy

Question 29

spinal cord PRV constraint for 4 Gy fx

Answer 29

Dmax < 22 Gy

Question 30

spinal cord PRV constraint for 40/15

Answer 30

35 Gy

Question 31

spinal cord PRV constraint for 45/30 BID

Answer 31

42 Gy

Question 32

HART and CHART and results

Answer 32

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

Question 33

lung window level settngs

Answer 33

``` W = 400 to 1600 L= -400 to -600 ```

Question 34

normal lung volume

Answer 34

lung-Gtv

Question 35

What is PET used for with lung?

Answer 35

-differentiate collapsed lung from disease- cannot see with CT

Question 36

concern of using IMRT in lung cancer

Answer 36

interplay effect

Question 37

what is min projection from 4DCT used for?

Answer 37

-negative contrast (like liver)

Question 38

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

Answer 38

Gate because tracking will expose more healthy lung to dose

Question 39

describe K shape in lung

Answer 39

avoids going through cord | comes in through heart and ipsi lung