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Treatment Planning > breast > Flashcards

breast Flashcards

1
Q

why do we use bolus every other day when treating chest wall?

A

this is because we use VMAT instead of 3D-CRT. With VMAT, since the beams are perpendicular, the dose to skin is lower compared to oblique beams using tangent or 3D-CRT. Because of this, can use bolus to bring higher dose to skin and ensure the skin gets treated

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2
Q

what do you usually use for intact breast?

A

tangents (med and lat)- spare contra side more than with VMAT

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3
Q

what do you usually use for breast + lymph nodes

A

depending on how many lymph nodes involved, VMAT or 4 field

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4
Q

what is HER2 +

A

tests positive for HER2, promotes cancer cells

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5
Q

what is ER+

A

is used to describe breast cancer cells that may receive signals from the hormone estrogen to promote their growth. Good diagnosis because you can use hormones to help with treatment

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6
Q

breast treatment positions

A

supine with breast board, holds arms above head
-sometimes incline for comfort and consistency
prone with breast board

DIBH for left side (get heart away from field)

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7
Q

what is SSN

A

suprasternal notch
measured SSN to chin distance everyday and keep constant

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8
Q

advantages of prone position

A

-especially for larger breasts
-improves dose homogeneity, reduces lung dose and can reduce heart dose

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9
Q

how to verify hear/lung in the field for breast tangents?

A

MV imaging

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10
Q

position of thyroid, trachea, and esophagus

A

thyroid is ant to trachea which is ant to esophagus
thyroid sort of wraps around trachea in axial view

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11
Q

where are IMN nodes?

A

next to sternum, just behind ribs

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12
Q

where are SCN nodes?

A

ant to humeral head, go down to below armpit

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13
Q

typical breast fractionations

A

50/25
40/15 + 11/4 electron boost or 10/15 photon SIB or 12.5/5 sequantial photon boost
26/5 - small breasts only (PTV<2000cc)

38.5/10 BID (APBI)

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14
Q

field borders for breast tangents

A

medial-midsternum
lateral- 2 cm beyond palpable breast tissue (midaxillary line)
inferior- 2 cm from inframmamary fold
superior- head of clavicle- this is wrong
post field border should be half beam blocked

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15
Q

max amount of lung allowed in breast field

A

2 cm

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16
Q

heart allowed in breast field

A

non
use MLCs to shield completely

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17
Q

FLASH

A

-2cm MLC margin is left in anterior direction to allow for breathing motion and swlling

-using flash decreases # of MU required due to larger FS (larger output factor) without changing dose distribution in patient

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18
Q

SCN POP

A

-match inferior part with superior part of breast tangents. Use half beam block to minimize beam divergence between breast tangents and SCN fields
-superior goes to top of first rib
medial goes to pedicles of vertebral bodies
lateral goes to coracoid process or humeral head
-AP weight 0.7
-PA weight 0.3

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19
Q

contra breast tolerance

A

4 Gy

20
Q

heart tolerance

A

<2-3 Gy

21
Q

ipsi lung

A

4.5 Gy

22
Q

contra lung

A

2 Gy

23
Q

cord dmax

A

<50 Gy (2 Gy fractions)

24
Q

esophagus mean dose constraint

A

30 Gy

25
Q

humeral heads dmax constraint

A

40 Gy

26
Q

thyroid PRV dmax constraint

A

40 Gy

27
Q

erythema

A

reddening of skin from radiation

28
Q

heart toxicity

A

pericarditis
-inflammation of heart, can make it difficult to breathe

29
Q

liver mean dose constraint

A

30 Gy (2 Gy fractions)

30
Q

esophagus toxicity

A

esophagitis- sore throat, difficulty swallowing

31
Q

liver toxicity

A

radiation induced liver disease

32
Q

late skin effects

A

edema
fibrosis

33
Q

late heart effects

A

coronary artery disease (increasses by 7%/Gy)

34
Q

bone marrow toxic effects

A

can affect patient blood supply

35
Q

most important OARs for SCN treatment

A

cord, humeral head, thyroid, esophagus

36
Q

medial field tanget angle

A

~50 degrees
lat is ~220 degrees

37
Q

what do SCN and IMN stand for

A

supraclavicular nodes and imternal mammary nodes

38
Q

electron IMN treatment

A

junction electron to photon beam
may kick couch to get electron beam as unfirm as possible in sup-inf direction (beam it coming in perpendicular to patients chest in saggittal view)

. Rule of thumb: electron beam is ~5 to 10 degrees less oblique than the medial field. There is a trade-off between hotspot at the junction due to electron isodose distribution bulge when the electron beam is too close to being parallel with the photon medial field, and cold spot at the junction when the electron beam is too perpendicular to the body (not close enough to being parallel to the photon field). Generally want the electron beam angle to be somewhere in between being parallel with photon field divergence and perpendicular to the patient. Photon and electron fields in this case are typically abutted at the surface.

39
Q

describe isodose lines in tangent breast

A

105% hot spot at nipple
105%hot spots at beam entry points
-30% dips into lung- should see a dip into the lung since it is lower density
-100% to the norm point

40
Q

APBI

A

accelerated partial breast irradiation
-38.5/10
-non-coplanar beams
-all OARs to get < 1 Gy

41
Q

esophagus dmax constraint

A

40 Gy

42
Q

why do lower E isodose lines curve into lung whereas higher E isodose lines curve towards breast surface?

A

lung- inhomogeneity
higher isodose lines- breast separation is decreasing towards nipple- gets hotter towards nipple
amount of curving into breat depends on where you out the norm point

43
Q

PTV margin

A

0.5 cm

44
Q

CTV margin

A

surgical bed + 1 cm

45
Q

key rule of breast 3D planning

A

-keep field edges straight. avoid divergence
-avoid divergence into lung
-avoid divergence of tangents into SCN and vice versa

46
Q

SCN + tangents isocenter is where?

A

at junction of tangents and SCN field

47
Q

diagram of fields for tangents + SCN

A

Treatment Planning (17 decks)

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