Chapter 8 PP Flashcards
what are the two verify and record systems used at our clinical sites
aria & mosaiq
what are the two types of lasers
red or green helium (HeNE) neon lasers
which color laser projects more sharply
green
because they have a shorter wavelength causing less scatter on the skin
what is the type of couch currently used
carbon fiber
what was the previous couch that was used
mylar
which couch can you see through
mylar
POP field
parallel opposed portal
Lt/Rt lateral or AP/PA
tangents field
opposing field for supericial volumes on curved surfaces which has flash off of the patient
four field box field
fields are arranged 90 degrees from one another
arc therapy
radiation is delviered while the gantry moves through its arc of rotation
conformal treatment technique
delivers a uniform dose to structures in the beam path
IMRT treatment technique
delivers a nonuniform dose across the beam path
2 methods of IMRT
step and shoot
sliding window
VMAT (volumetric modulated arc therapy)
delivers IMRT vial rotational arc, multiple MLC positions and changing dose rate, further conforming dose delivery to the tumor volume and acoiding organs at risk
electron technique
superficial treatment
common prescription changes include change in: (4)
of factions
total dose
bolus
beam apertures
the rad therapist should review the prescription __________ each treatment as the oncologist may have made changes from the previous day
immediately before
what should be reviewed in the treatment plan? (5)
field sizes beam modifiers depths (SSD) dose measurement (diodes) gantry angles
examples of treatment techniques
IMRT 3D conformal POP four field box tangents
The point of intersection of three axes of machine rotation (gantry, collimator, and base of couch)
isocenter
Are any fixed reference points against which other objects can be measured.
fiducial markers
fiducial markers can be at the (3)
skins surface, fixed external to the patient, or internal
Two images taken perpendicular to one another, with a 90 degree angle between them.
Ex. AP and Rt. Lateral, AP and Lt. Lateral, PA and Rt. Lateral, PA and Lt. Lateral
orthogonal images
what imager is used for orthogonal images
KV
what are orthogonal images used for
to verify isocenter
__________ verify the BEV path, including the beam shape, position, and projection of the beams central axis
portal images
what treatment beam is used for portal images
MV
most sites do portal iamging _________
once a week
At clinic will often take two exposures:
planned one and an open one (double exposure)
______________ allows therapists to see surrounding anatomy, increasing the landmarks for interpretation
open exposure
open exposure is made after the removal of
the field-shaping devices and the collimator jaw retraction
When wedges are used, the _______ are typically positioned together.
heels
Wedges reduce the dose in areas of overlap between fields that have a hinge angle less than ____.
180 degrees
The thick end of the wedge is the heel and it attenuates the________ amount of radiation, drawing the isodose lines _______ to the surface.
greatest; closer
The thin end of the wedge is called the_____ which is where the dose delivered to the patient will be relatively ______ than the dose at the opposite side of the treatment field.
toe
greater
All beam-shaping and modification devices for photon beams must be secured a minimum of _____ from the surface of the patient.
why?
20 cm
The interaction of the photon beam with materials produces scatter electrons that contaminate the photon beam and produced increased skin does for patients. Low-energy electrons are absorbed in approximately 15cm of air.
rather than a physical wedge being used, dynamic jaws and MLCs can be used to configure for movement through beam delivery accomplishing what a physical wedge would have done.
dynamic wedge
the side of field at which the jaw starts its movement receives _______ exposure, correlating with the ________.
more
wedge toe
In general, if something is placed in the path of the beam, the number of MUs will need to be ______ to deliver the prescribed dose
increased
the _______ within the head of the gantry measures the radiation output
ion chamber
