Treatment Planning

Question 1

the following is describing INVERSE or FORWARD planning?

-3D trt plans
-trial and error method
-planner chooses beam energy, beam number & direction, beam size & shapes, beam modifiers, etc
-computer then calculates dose distribution

Answer 1

FORWARD planning

Question 2

the following is describing INVERSE or FORWARD planning?

-IMRT trt plans
-planner chooses dose & tolerances to organs
-computer generates trt plan w/ beam energy, beam shapes, beam direction, etc.

Answer 2

INVERSE planning

Question 3

describe “Plan Optimization”

Answer 3

computer generates a plan but the planner adjusts it, then the computer RE-adjusts once again, to achieve the best possible plan

Question 4

for INVERSE trt planning, a _____ dose is set

Answer 4

minimum dose is set

Question 5

describe what a “minimum dose” is

Answer 5

it is a dose that would NOT result in a known effect, like a max dose (TD 5/5; 3/3)
-it is a type of parameter

Question 6

Plan Optimization happens for only Forward planning, only Inverse planning, or both?

Answer 6

both!

Question 7

DVH stands for what?

Answer 7

Dose Volume Histogram

Question 8

a ______ provides information on the dose distributions to different organs, including the PTV and OARS w/i the radiation field

Answer 8

DVH

Question 9

on a DVH, when the curve intersects the horizontal axis, this typically is where ____ is at

Answer 9

max dose

Question 10

T/F: a DVH does NOT replace an isodose line distribution

Answer 10

TRUE they are separate things

Question 11

what does the vertical line (y) on a DVH show?

Answer 11

the vertical line (y) shows the percent of the organ or the volume of tissues

Question 12

what does the bottom horizontal line (x) show?

Answer 12

the bottom horizontal line (x) shows the dose and can be expressed in Gy, cGy, or percent %

Question 13

_____ are treatment planning tools used to evaluate doses to normal tissues and tumors

Answer 13

DVH’s

Question 14

what must happen in planning, for organs to be included on the DVH?

Answer 14

they must be contoured

Question 15

this is an example of what?

Answer 15

DVH (Dose Volume Histogram)

Question 16

when contouring we are assigning a ______ of the scan to a specific organ
*hint - pixel or voxel

Answer 16

voxel
–> a volume element

… the system then determines how much dose the specific voxel is getting and adds it up for the whole organ to express on the DVH

Question 17

reading a DVH example - what is the max dose of the stomach *according to this example –>

Answer 17

2200 cGy

Question 18

higher energy beams have ___more deep/less deep___ isodose charts and why?

Answer 18

more deep (deeper) isodose charts because more penetrating

Question 19

what graphs/charts/curves/etc. represent dose in the body; areas in body that receive dose?

Answer 19

isodose curves

Question 20

what are the intervals isodose curves are drawn at?

Answer 20

parallel and perpendicular directions of the radiation beam

Question 21

what factors effect isodose curves? (6)

Answer 21

1. beam energy
2. SSD
3. field weighting
4. beam modifiers
5. field size
6. beam type

Question 22

a _____ field size will cause more scatter, making for ___shallow/deeper___ isodose lines

Answer 22

a larger FS will cause more scatter, making for deeper isodose lines
*recall we can lower the MU to compensate

Question 23

isodose curves are expressed in _____ at specific depths

Answer 23

percents

Question 24

label the following isodose curves as –>
-electrons
-photons with wedge
-photons

Answer 24

1. photons
2. photons with wedge
3. electrons

Question 25

_______ are used to help reduce areas of overlap in trt plans with multiple fields and hinge angles less than 180 degrees
–also used for tissue compensation in areas OF SLOPING SURFACES, like breast

Answer 25

wedges
**to help not get bolus and wedges confused focus on how it says sloping surfaces = wedge

Question 26

a standard wedge, would be a physical wedge or dynamic?

Answer 26

physical

Question 27

where are physical wedges/standard wedges placed? and what is their typical material?

Answer 27

physical wedges are slipped into the collimator and are made of lead or steel

Question 28

how are dynamic wedges created?

Answer 28

by moving a jaw within the treatment head

-JAW!!!! not MLC

Question 29

the ___ of a wedge brings isodose curve up higher to surface within patient

Answer 29

heel
–decreases the penetration of beam due to attenuation happening within thicker part of wedge (heel)

Question 30

the _____ of a wedge allows for MORE transmission of the beam!!!

Answer 30

toe
-thinner part of wedge, less attenuation

Question 31

many say wedge depth definition/angle is at the _____% isodose curve or a ___cm depth for higher energies

Answer 31

50% isodose curve
or 10 cm depth

Question 32

label parts of this isodose curve diagram -

Answer 32

1. wedge’s toe
2. MORE dose getting into patient – going deeper – because more beam transmission
3. LESS dose getting into patient – more shallow – because less beam transmission due to increased attenuation
4. attenuation
5. wedge’s heel
6. patient’s surface

Question 33

dose is greatest where?

Answer 33

at central axis!!!

Question 34

_____ region is on the beam’s edge

Answer 34

penumbra

Question 35

field size is defined where/when? - for photon

Answer 35

at the 50% isodose line

Question 36

the following is an example of a ___________

Answer 36

beam profile

Question 37

if there is a flattening filter on a photon beam and we look at the beam prifile… what can we expect to see on it?

Answer 37

horns

Question 38

photons use what filter/foil? what about electrons?

Answer 38

photons = flattening filter
electrons = scattering foil

Question 39

________ = rapid fall of due to side scatter

Answer 39

penumbra

Question 40

where/when does penumbra occur?

Answer 40

between 90-20% isodose lines
…this is why beam flatness is only measured on inner 80% of beam