Abutting Fields

Question 1

abutting fields can also be called what?

Answer 1

adjacent fields

Question 2

abutting fields can be used for different treatments, however which one is a common treatment?

Answer 2

CSI (craniospinal)

Question 3

describe abutting/adjacent fields -

Answer 3

abutting/adjacent fields are two fields next to one another that meet at a determined depth within the patient because of beam divergence

Question 4

_______ reduce hot and or cold spots for adjacent/abutting fields

Answer 4

skin gaps

Question 5

the following is depicting a CSI trt, which uses what field technique?

Answer 5

abutting fields

Question 6

to match spine field… what is employed for the whole brain field of a CSI trt

Answer 6

collimation

Question 7

what does CSI stand for?

Answer 7

Craniospinal Irradiation

Question 8

in general, where photon fields are measured are at the 50% isodose line, where abutting fields connect adds up to ___%

Answer 8

100%

Question 9

what equation does skin gaps use?

Answer 9

gap calc

Question 10

_____ BLURS SKIN GAP and further reduces any hot or cold spots

Answer 10

feathering

Question 11

for gap calc - when looking at which field edge to use, you want to use ___larger/smaller___ field length ?

Answer 11

for gap calc use the larger field length!!!; larger # will be length

Question 12

what is the gap calc?

Answer 12

Question 13

label this skin gap diagram -

Answer 13

1. SSD1
2. L1
3. gap
4. depth
5. L2
6. SSD2
7. patient’s surface

Question 14

in a CSI skin gap problem - what should remain the same, Length or Width? Or does both Length and Width change?

Answer 14

Width should remain the same, length changes

Question 15

calculate the skin gap -

Answer 15

answer = 1.7 cm gap on skin surface

Question 16

fill in the blanks -

Answer 16

SKIN –> DIVERGE

Question 17

Concept check! EXPLAIN why/how on a CSI spine fields, on the skin there will be a gap but in the body there is not one

Answer 17

gap on skin but in reality the beams diverge w/i body for full coverage

Question 18

typically CSI’s are treated ____supine/prone____

Answer 18

prone

Question 19

for a CSI what fields are used to treat the brain (whole brain) and what field treat the spine?

Answer 19

RT and LT lats for whole brain (POPs)
single PA fld for spine

Question 20

the spine and whole brain fields of a CSI are ______ junctions

Answer 20

orthogonal junctions

Question 21

to determine a CSI COLLIMATOR angle use the ____ field length & SSD

Answer 21

spine!

Question 22

to determine a CSI COUCH kick angle use the ____ field length & SSD

Answer 22

brain!

Question 23

solve for the CSI collimator rotation angle -

Answer 23

= 6.3 degrees
**hint - use spine length because spine is long and collimator is a longer word !!!! and SSD because it has a lot of S’s

Question 24

solve for the CSI couch kick rotation angle -

Answer 24

= 5.14 degrees
**hint - use brain because couch is shorter word than collimator and brain = SAD because SAD in brain!!!

Question 25

what is equation for CSI collimator rotation?

Answer 25

Question 26

what is equation for CSI couch rotation?

Answer 26

Question 27

typically, for CSI in which direction do we rotate the couch?

Answer 27

towards the gantry

Question 28

the following depicts what kind of treatment?

Answer 28

CSI (craniospinal)

Question 29

half beam block is another method for setting up _____ fields

Answer 29

abutting
-seen a lot with breasts (personally)

Question 30

half beam block is ____isocentric technique

Answer 30

monoisocentric technique

Question 31

monoisocentric means there is how many isocenters?

Answer 31

1

Question 32

for a half beam block the ___ closes to ___ and there would be no beam divergence

Answer 32

jaw closes to zero

Question 33

a half beam block has NO beam _________

Answer 33

divergence

Question 34

3 or 4-fld breasts typically use what technique?

Answer 34

half beam blocks

Question 35

if using a half beam block, what is not needed/used?

Answer 35

no couch kicks or collimation

Question 36

the following is an example of what?

Answer 36

a half beam block