Geometric Parameters and Patient Measurements/Treatment Planning Parameters

Question 1

measurements of the treatment field are defined at _______________

Answer 1

isocenter
(width x length)

Question 2

how is a field size created?

hint - probably more in depth than you’re thinking

Answer 2

created by two pairs of the secondary asymmetric collimator jaws

Question 3

from a base field size, fields can be further shaped via _________

Answer 3

MLCs/and or custom Cerrobend blocks

Question 4

_____ are a document of the field parameters

Answer 4

DRRs

Question 5

the physical radiation field size is delineated at the _____% isodose line

Answer 5

50%

Question 6

what happens to the physical radiation field size at the 50% isodose line?

Answer 6

it is delineated

Question 7

tumor depth is established with ____ imaging

Answer 7

3D imaging

Question 8

tumor depth/depth of a tumor determines ________ and ______ according to Laura Nappi

Answer 8

-the energy of the beam
-the type of treatment

Question 9

superficial tumors are most likely to be treated with __________

Answer 9

electrons

Question 10

deeper tumors are most likely to be treated with __________

Answer 10

photons

Question 11

“Patient Separation” can also be called what? (looking for 3 other names)

Answer 11

• patient thickness
• intrafield distance
• innerfield distance (IFD)

Question 12

what does IFD stand for?

Answer 12

Innerfield Distance

Question 13

what does DRR stand for?

Answer 13

Digitally Reconstructed Radiograph

Question 14

patient separation is measured how and where?

Answer 14

• measured at central axis and at specific points within the treatment field

*think about in class with megan and graph paper and wire

Question 15

patient separation can be measured using what type of tool?

Answer 15

caliper

Question 16

what is a caliper?

Answer 16

a ruler with one sliding leg and one stationary leg

Question 17

what does SSD stand for?

Answer 17

Source to Skin/Surface Distance

Question 18

what does SAD stand for?

Answer 18

Source to Axis Distance

Question 19

the following is describing SAD or SSD?

• 100 cm OR it is possible to have it at another specified “fixed”
• used for electron fields or to be able to obtain larger field sizes
• used for electron fields
• distance from the source of radiation to the patient’s skin surface
  -typically what is taken every 5th trt day

Answer 19

SSD

Question 20

the following is describing SAD or SSD?

• in current LINACS it is located at 100 cm, in older Cobalt-60 machines it is at 80 cm
• Isocentric technique
• distance from source of radiation to isocenter (within patient)
• should never change

Answer 20

SAD

Question 21

T/F:

isocenter can be within or on a patient

Answer 21

TRUE

tumor within or superficial tumor!

Question 22

define “isocentric technique”

Answer 22

when the isocenter is located WITHIN the PATIENT

Question 23

for an isocentric technique SSD is what?

Answer 23

less than 100 cm

Question 24

does a patient need to be moved between fields of an isocentric technique?

Answer 24

No

Question 25

are there more or less chances of error with an isocentric trt?

Answer 25

less

Question 26

T/F: if using an isocentric or SAD technique, the SSD WILL change at different gantry angles *hint - think about clinic and when you check different SSDs like a true lat or AP*

Answer 26

TRUE

Question 27

there is more chance of error using an SSD or SAD trt

Answer 27

SAD is a more sure way, with less chance of error

Question 28

what can an isocentric technique also be called? -

Answer 28

SAD technique

Question 29

T/F: for an SSD technique trt, a patient may need to be moved between fields

Answer 29

TRUE -which causes more chance of error

Question 30

the _________ collimating jaws are movable and asymmetric

Answer 30

secondary

Question 31

secondary collimating jaws can create __________ field sizes ranging from __x__ cm to ___x___ cm at the isocenter

Answer 31

-rectangular 0x0 cm to 40x40 cm

Question 32

jaws are made of what material?

Answer 32

tungsten

Question 33

only ____ percent of transmission through jaws is permitted

Answer 33

only <0.5%

Question 34

as field size increases, does collimator scatter decrease OR increase

Answer 34

INCREASE

Question 35

T/F: collimator scatter contributes to dose a patient receives

Answer 35

TRUE

Question 36

collimator scatter contributes to dose, therefore, less ____ is needed

Answer 36

MU (monitor units)

Question 37

abutting or adjacent fields meet at a determined depth within the patient because of ____________

Answer 37

beam divergence

Question 38

to avoid hot spots or cold spots, there must be a _____ on the skin surface

Answer 38

gap

Question 39

to avoid hot spots or cold spots, there must be a gap, where?

Answer 39

on the skin surface

Question 40

what calculation is commonly used in CSI (craniospinal irradiation)

Answer 40

gap calculation

Question 41

what is a common orthogonal field area of possible overlap for CSI (craniospinal irradiation)?

Answer 41

laterals for the cranium and PA fields for the spine

Question 42

*Scenario: CSI (craniospinal irradiation) ___________ causes overlap between the cranium and spine fields, and between the multiple spine fields

Answer 42

beam divergence

Question 43

what are other techniques to avoid overlap besides the gap calculation? (3)

Answer 43

- half-beam block - beam splitters - couch rotation (kick)

Question 44

__________ is a technique used to move or change the location of the gap throughout the treatment

Answer 44

feathering

Question 45

T/F: feathering position is adjusted at least 2-3 times throughout the treatment, usually every 5 fractions

Answer 45

TRUE

Question 46

_______ blurs any inhomogeneous (not the same) doses within the gap area

Answer 46

feathering

Question 47

with Feathering, the ________ axis remains the same, but the field ______ change

Answer 47

the central axis remains the same but the field lengths change

Question 48

image ______ uses multiple imaging modalities to provide better visualization of the patient's anatomy - --> the images from the multiple sources are laid over one another to create a more informative image

Answer 48

image fusion

Question 49

the following is an example of image fusion - what two images are fused?

Answer 49

MRI and CT

Question 50

the following is an example of image fusion - what two images are fused?

Answer 50

PET and CT

Question 51

what is another name for the treatment planning computer?

Answer 51

Virtual Simulator

Question 52

in the _______ simulator, the physician identifies treatment borders and isocenter

Answer 52

virtual

Question 53

what scans are useful for soft tissue?

Answer 53

MRI -commonly used for prostate

Question 54

what scans are useful for showing tumor activity?

Answer 54

PET -commonly fused for lung and HN

Question 55

T/F: multiple different scans can be fused together to provide for better visualization of the patient's anatomy

Answer 55

TRUE

Question 56

abutting fields meet at a determined depth within the patient because of what?

Answer 56

beam divergence

Question 57

for abutting fields, gap is calculated to avoid what? (2)

Answer 57

hot and cold spots

Question 58

abutting fields and gap calcs are commonly used for what treatment?

Answer 58

CSI - Craniospinal

Question 59

_______ ________ causes overlap between the cranium and spine fields and - between the multiple spine fields

Answer 59

beam divergence

Question 60

techniques such as - half-beam block, beam spoilers, or couch kicks/rotations are used to avoid what?

Answer 60

overlap and hot spots