treatment volume, tx field and techniques, rotational fields and fixed fields, field weighting (tx dose and prescription)

the tumor volume that is visible or can be palpated

gross tumor volume

it is GTV and the area around it that may have microscopic disease

clinical target volume CTV

what accounts for the FTV plus motion of the tumor caused by breathing or involuntary motions

internal target volume ITV

what scans are required to determine the ITV

4D CT sim

what is considered the CTV (or ITV available) and an area around it to give a margin for uncertainties

planning target volume PTV

the area that is contained within the isodose curve

treated volume

the volume of tissues that is given a large portion of the dose and includes tissues that reveives more than 50 percent of the target dose

irradiated volume

there organs close to the irradiated area that may affect or limit the dosage delivered

organs at risk OAR

multiple treatment fields are more commonly used for ? treatment

curative

single fields are more commonly used for ? treatment

palliative

single fields are usually used for what type of field

posterior spine

parallel opposed portals POP have what

hinge angle of 180 degrees

hinge angle refers to what

the degrees btw each gantry angle

which field technique is commonly used for structures within the abdomen, such as the pancreas, bladder, rectum, etc

• when an odd number of fields are used, it is common for wedges to be used to even out dose distribution

three field technique

what field is commonly used for deep tumor within the pelvis or abdomen

four field technique/four field box

four field box have what type of angle and at what degree

hinge angles of 90 degrees

what has a hinge angle that is less than 180 degrees btw 2 fields

• requires wedges to have a more even dose distribution

• the thick ends of the wedges, aka as the heel face each other

• commonly used for more superficial tumors

wedge pair technique

what is it called when the radiation is delivered while the gantry is moving in an arc from one set point to another

rotational field aka acr therapy

for partial arcs or arcs less than 360 degrees, the treatment planning method is called what?

• the treatment plans for the beam to treat to a depth farther than the center of the tumor

past pointing

(T/F) for fixed fields, the gantry does not move while the radiation beam is delivered

T

arc speed is calculated how

degree/MU

what is it called when different fields can deliver different percentages of the total dose

field weighting

when can field weighting be used?

tumor does not lie at mid depth

one beam may be going through a critical structure