Treatment Prescription Flashcards
Prescription
T/F:
Total doses change depending on the location of the tumor and the organs at risk (OARs) surrounding the tumor
TRUE
what are 2 reasons listed in Laura Nappi book total doses may change?
- depending on location of tumor
- organs at risk surrounding the tumor
the following doses are example of Curative or Palliative?
180-200 cGy to a total dose of 5400-6000 cGy
Curative
the following doses are example of Curative or Palliative?
300 cGy to a total dose of 3000 cGy
Palliative
define a “boost” and or “cone-down field”
a smaller field, that can give a higher dose
what is the most common fractionation schedule?
once a day, for five days a week, for several weeks
T/F:
the amount of fractions DOES NOT vary with the total tumor dose
FALSE
the total amount of fractions DOES vary with the total tumor dose… it would have to, since dose is delivered each fraction
what does BID mean?
twice a day
what is the shorthand verbiage for “twice a day”?
BID
what is MINIMUM number of hours that must occur between each radiation fraction delivered to any patient?
6 hours
how is beam energy selected for treatments?
it is chosen depending on the thickness of the patient and depth of the tumor
tumors in areas of the BODY that are THICKER use __lower//higher__ beam energies?
higher
most treatments of pelvic tumors use what energy?
15x
most treatments of brain tumors use what energy?
6x
tumors in areas of the BODY that are not really thick use __higher//lower__ energies?
lower
different beam energies have differnt depths for _______
dmax
what is dmax?
depth of maximum dose
T/F:
different beam energies DO NOT have different depths for dmax
FALSE
they very much do have different depths for dmax depending on beam energy level
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“two protons and two neutrons, also known as a helium nuclei, is released from an unstable heavy nuclei as it decays”
alpha particles
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
-no mass and no charge
-manmade
-interaction occurs near nucleus
xrays
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“electromagnetic radiation, known as photons”
xrays
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
-negatively charged (negatron) or positively charged (positron)
-travel further and penetrate farther than others
beta particles
which penetrate farther? - beta or alpha particles
what about when compared to gamma rays and xrays?
BETA
– gamma and xrays penetrate farther than beta (..thus farther than alpha too)
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
-has a charge, a heavy mass, and a high LET
-travels short distances but creates a lot of damage in that distance
-common in atomic numbers greater than 82
alpha particles
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“electrons released by the nucleus”
beta particles
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“photons naturally emitted from a nucleus”
gamma
-why there is live source in gamma pods, etc
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
-cosmic rays
-terrestrial radiation
-radionuclides in the human body
natural background radiation
what does GTV stand for?
Gross Tumor Volume
what does CTV stand for?
Clinical Target Volume
what does PTV stand for?
Planning Target Volume
what does ITV stand for?
Internal Target Volume
what does OAR(s) stand for? - what are some examples
Organs at Risk
- heart
- lens of eye
- bladder
- rectum
- femoral head
the following is describing what treatment volume?
(ie. GTV, PTV, etc…)
“accounts for the CTV, plus motion of the tumor caused by breathing or involuntary motions”
ITV
Internal Target Volume
the following is describing what treatment volume?
(ie. GTV, PTV, etc…)
“is the tumor volume that is visible or can be palpated”
GTV
Gross Tumor Volume
the following is describing what treatment volume?
(ie. GTV, PTV, etc…)
“is the CTV, and an area around CTV to give a margin for uncertainties”
–> what are examples of said uncertainties?
PTV
Planning Target Volume
–> uncertain examples = patient motion, penumbra, variations of trt setup
the following is describing what treatment volume?
(ie. GTV, PTV, etc…)
-“is the GTV and the area around it that may have microscopic disease”
-“visible or palpable tumor plus any margin of subclinical disease”
CTV
Clinical Target Volume
the following is describing what treatment volume?
(ie. GTV, PTV, etc…)
hint - __________ volume
-“the area that is contained within the isodose curve”
-“generally larger than the target volume, encompasses the additional margins around the target volume to allow for limitations of the treatment technique”
Treated Volume (TV)
the following is describing what treatment volume?
(ie. GTV, PTV, etc…)
hint - __________ volume
-“the volume of tissue(s) that is given a large portion of the dose”
-“volume of tissues receiving a significant dose of the specified target dose”
Irradiated Volume (IV)
-_________ are organs close to the irradiated area that may effect or limit the dosage delivered
-normal issues in which _______ sensitive to radiation damage may influence treatment planning and/or delivery of a prescribed dose radiation
Organs at Risk (OARs)
in the image - label (1) and label (2)
(1) PTV
(2) GTV
according to Laura Nappi, what 2 reasons are treatment fields established?
- based on tolerance doses of the nearby organs at risk
- dose distributions
field orientations are arranged depending on the ______ and ______________ near the tumor
on the -location
and -organs at risk near the tumor
T/F:
MLCs and other beam modifiers can be used to further shape the beam
TRUE
T/F:
Adequate dose distributions usually require multiple fields
TRUE
what type of fields are usually used for a posterior spine field?
single fields
Parallel Opposed Portals (POPs) have a hinge angle of what?
180 degrees
what are some examples of POPs (Parallel Opposed Portals)
- RT and LT lats
- AP and a PA
_______ field technique is commonly used for structures within the abdomen, such as the pancreas, bladder, rectum, etc.
three-field technique
_____ field technique is commonly used for deep tumors within the pelvis or abdomen
four-field technique/four field box
for a four-field box/four field technique, how far apart are the fields from one another
hint - in degrees
each is 90 degrees apart
a wedge pair technique has a hinge angle LESS THAN ______ between two fields
LESS than 180
- so example, an AP and a LT lat –> 90 degrees
thick ends of wedges are also known as ____
heels
the heels of wedges DO or DO NOT face each other for a wedge pair field?
wedge heels face each other
–heels together, toes apart
a wedge pair technique is commonly used for what type of tumor(s)?
superficial tumors
a wedge-pair technique requires a wedge to have more/a more even ________________
a more even dose distribution
rotational fields can also be called ____ therapy
ARC therapy
the following is describing what type of treatment technique?
“radiation is delivered while the gantry is moving in an arc from one set point to another”
-VMAT
-ARC therapy
-Rotational fields
for arcs LESS than 360 degrees, what is the treatment planning method called?
hint - starts with a “p”
past pointing
why would there be an arc treatment that does not go a full 360 degrees/a partial arc?
the treatment plans for the beam to trt to a depth FARTHER THAN THE CENTER OF THE TUMOR
for arcs that ARE 360 degrees, the beam is set to treat where in regards to the tumor
at an exact depth of the center of the tumor
how is ARC speed calculated?
MU/degree
MU/degree calculates what?
ARC speed
T/F:
before treating with an ARC, the therapist DOES NOT HAVE TO do a dry run of the gantry rotation to ensure there will be no collisions between the gantry and the patient or table
FALSE
- must do dry run, think back to QAs at Kyle and ACC *VMATs
-would do a dry run for new starts or if they got a boost, change in plan etc.
what does VMAT stand for?
Volumetric-Modulated Arc Therapy
describe main difference between VMAT and IMRT
IMRT - MLCs move, gantry does not rotate while beam is on
VMAT - MLCs move AND gantry is on continuous rotation while beam is on
T/F:
For fixed fields, the gantry DOES move while the radiation beam is delivered
FALSE
Gantry DOES NOT move for fixed field; FIXED
-the gantry moves between each field while the beam is off
-the gantry is stationary while the beam is being delivered
T/F:
doses from multiple fields ARE always equal
FALSE
-doses from different fields CAN BE weighted differently
when would one want/use an unequal weighted field?
usually used when the tumor dose not lie at mid-depth/mid-line
or when one beam may be going through/obstructing critical structure(s)
T/F:
Beam angles can contribute different doses toward the total dose
TRUE
the following could be an example of what?
AP:PA with weights 2:1 respectfully,
–the AP would deliver 2/3 of dose
–the PA field would deliver 1/3 of dose
weighted fields
Scenario:
AP:PA with weights 2:1 respectfully.
Answer the following questions
–the AP would deliver how much?
–the PA field would deliver how much?
AP = 2/3 of dose
PA = 1/3 of dose
isocenter is at ___ cm
100
we treat electrons to ___ cm
100 cm
100 SSD
*SSD = SOURCE TO SKIN DISTANCE!
*TSD = TARGET TO SKIN DISTANCE!
what is the max field size of a LINAC?
40x40 cm at 100 SSD
Photon therapy energies range from about ___ to ___ MV
4-35 MV
Electron therapy energies range from about ___ to ___ MeV
4-22 MeV
Photon energy is measured in ___ whereas Electron energy is measured in ______
Photon = MV (Megavolt)
Electron = MeV (Mega electron volt)
treatment tables can hold up to ____ pounds (lbs)
350 lbs
T/F:
any changes in a patient’s trt plan must be recognized PRIOR to the patient’s next trt
TRUE
If a patient’s trt plan is changed, and the change includes a change in field size or shape, must happen?
- patient’s trt plan must be recognized PRIOR to the patient’s next trt
- NEW FIELD MUST BE IMAGED FOR CONFIRMATION
what is being described below -
- ____ is placed between the radiation source and the patient’s skin
- it brings dose closer to the skin’s surface and decreases skin sparing
- will attenuate some of the beam
bolus
____________ and ___________ are used to alter the isodose distribution based on the patient’s skin contour
wedges and compensators
____________ are made of a high-density material, like Cerrobend or “poly lead” and are rarely used nowadays and have been replaced by IMRT
compensators
like compensators, wedges are made of ___high//low__ density material
high
wedges can be made of ___ or ____ commonly
lead or steel
newer machines use _______________ to replace the use of physical wedges
EDW (Enhanced Dynamic Wedges)
- internal wedges; dynamic wedges
instead of a physical wedge that is placed into the treatment head, an EDW (Enhanced Dynamic Wedge) uses the motion of the ______ to mimic a wedge
Y-jaw
EDWs change the _______, just like a wedge
isodose distribution
when are EDWs added to patient’s treatment profile/techniques..?
planned in the treatment planning process
a ____________ is used in larger fields like TBI (Total Body Irradiation) and eliminates skin sparing
beam spoiler
describe a “beam spoiler”
-solid plastic tray
-increases dose to skin! without decreasing the penetration of beam!!
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“high LET particulate radiation, positively charged, which consists of 2 protons & 2 neutrons (helium nuclei) released during nuclei decay”
alpha particles
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“electrons released by the nucleus”
beta particles
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“electromagnetic radiation (photons) produced when a fast electron stream hits a target”
xrays
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
“high energy, electromagnetic radiation emitted from decaying isotopes, used in brachytherapy”
gamma rays
the following is describing what radiation type?
hint - choose from xrays, beta particles, alpha particles, gamma rays, or natural background radiation
-no mass, no charge, emitted during nuclear decay
gamma rays
T/F:
gamma rays and xrays penetrate FURTHER THAN alpha particles and beta particles
TRUE
label the tumor volumes in the image below -
- GTV
- CTV
- PTV
- TV (Tumor volume)
- IV (Irradiated volume)
for any LIVE source (ex. brachy, or Colbalt) we set ____ NOT MU.
set Time for LIVE sources … cause half-lives
field size is determined where?
AT ISOCENTER
extended distance is Isocentric OR Non-isocentric
NON-ISOCENTRIC
label the angles -
- LAO
- Left lat
- LPO
- RPO
- Right lat
- RAO
when a jaw is closed at 0, and the other jaw is not… what is this called?
Half Beam Block
draw how a HINGE angle should be -
illustrate the WEDGE angle -
T/F:
you CAN have a LT medial tangent and a RT lateral tangent
FALSE
you can only have a LT medial tangent and a LT lateral tangent … depends on side your treating… so RT would go with RT
*breast usually
label which is medial tangent and which is lateral tangent -
- medial tang
- lateral tang
out of the following - which are included on the prescription and which are included on the treatment plan
-bolus
-bolus thickness
-wedges
-blocks
-MLCs
prescription –> bolus and bolus thickness
treatment plan –> wedges, MLCs, blocks
TBI treatments have large or small fields? - that typically require what?
LARGE
- a beam spoiler
field size is created by what?
2 pairs of secondary asymm. collimator jaws (X and Y)
and further shaped using MLCs or custom blocks
____ document field parameters
DRRS
the physical radiation field size is delineated at the ___% isodose line
50%
target depth is establish using ___ imaging
3D
target ____ determines the energy of the beam and the type of treatment
depth
______ tumors are typically treated with electrons and ____ tumors with photons
-superficial tumors
-deeper tumors
______ _______ can also be called,
-patient separation
-intra-field distance
-inner-field distance (IFD)
patient thickness
patient thickness is measured how?
with calipers
…a ruler with one sliding leg and the other stationary is called __________
calipers
T/F:
SSD changes at different gantry angles when using SAD technique
TRUE
which technique has more room for error?
SAD or SSD
SSD
Low energy beams have what type of scatter?
What about High energy beams?
Low energy beams = back scatter
High energy beams = peak scatter
