Mosbys chapter 6 questions: radiation therapy equipment and quality assurance
during a split field test for longitudinal displacement of the collimator for jaw symmetry, the collimator is rotated through an angle of: a.) 360 degrees b.) 270 degrees c.) 180 degrees d.) 90 degrees
180 degrees split field testing for longitudinal displacement can be achieved by exposing film allowing on half of the field set at a set collimator angle and then rotating 180 degrees and exposing the other half of the field.
the common acceptable value for field flatness is about ___% over the central 80% of the largest field size at ioscenter.
3% field flatness across the central 80% of the beam should not vary outside of 3%
a long cylinder loaded with radioisotopes and placed in the vaginal space could be used to treat the: a.) vaginal vault b.) endometrium c.) pelvic side wall d.) vulva
A ( vaginal vault) long cylinders loaded with isotopes may be positioned in the vagina to deliver dose to the vaginal cavity. applicators such as Heyman's capsules or tandem and ovoids would deliver dose to endometrium and pelvis side wall. therapy to the vuvla could be delivered using teletherapy beams
which of the following checks must be carried out daily on the cobalt machine: (circle all that are correct): a.) function of radiation room monitor b.) function of door interlocks c.) beam output d.) time error
a and b function of the radiation room monitor function of door interlocks beam output is checked monthly and timer error is checked yearly
44. *****the important QA test(s) associated with the light field are (circle all that are correct:) a.) field size accuracy b.) beam output c.) light and radiation field coincidence d.) none of the above
a and c field size accuracy and light and radiation field coincidence the light field indicates the field size is relied upon as an indicator of where the radiation field is projected
the protective housing around the cobalt source in the cobalt machine should only allow transmission of ____ of the output a.) 0.1% b.) 1% c.) 2% d.) 5%
a.) 0.1%
OBI is an acronym for: a.) onboard imaging b.) off beam indicator c.) optical beam indicator d.) off baseline measurement indicator
a.) onboard imaging OBI devices can take on many forms from simple detectors and video cameras to complexed cone beam CT attachments
functional performance of radiation therapy equipment can (circle all correct): a.) not vary with time b.) change due to malfunction of system electronics or component fault c.) change due to wear and tear of the ewuipment d.) change due to environmental conditions
b and c change due to the malfunction of system electronics or component fault and change due to wear and tear of the equipment
. the purpose of positioning devices is to: a.) make the patient comfortable b.) accommodate the most appropriate position for accurate treatment delivery c.) prevent or limit patient motion during treatment d.) limit the setup time
b.) accomodate the most appropriate psoition for accurate treatment delivery
. a high energy photon unit will require daily quality checks for the determination of: a.) light and radiation field coincidence b.) dose rate constancy c.) field symmetry and flatness d.) crosshair centering
b.) dose rate constancy dose rate constancy should be verified daily and also monthly. the other quality checks are recommended to be performed monthly
. heyman capsules may be used to treat the: a.) vaginal vault b.) endometrium c.) vulva d.) prostate
b.) endometrium heyman capsules looks like a small tampon and is inserted into the uterine cavity delivery dose to the endometrium
the fletchers suite application is an example of: a.) interstital low dose rate brachytherapy b.) intracavitary low dose rate brachytherapy c.) permanent implant brachytherapy d.) injected, unsealed source brachytherapy
b.) intracavitary low dose rate brachytherapy fletcher's suite consists of tandem and ovoids loaded with low output sources into the female pelvis. this is an example of intra-cavitary brachytherapy. dose is delivered over a few days
brahcytherapy sources must be calibrated (circle all correct): a.) by the manufracturer only b.) by the accredited dosimetry calibration laboratory only c.) before being used for clinical dosimetry d.) by a user using a chamber with calibration traceable to an accredited dosimetry calibration laboratory
c and d before being used for clinical dosimetry and by a user using a chamber with calibration trace- able to an accredited dosimetry calibration laboratory
the linear scales on the treatment table are useful as an aid for: 1. daily treatment setup 2. translation of patient positions from simulation to treatment 3. providing information regarding filament voltage a.) 1 b.) 3 c.) 1,2 d.) 1,2,3
c.) 1 and 2 daily treatment setup and translation of patient positions from simulation to treatment
which of the following machines does not accelerate electrons? a.) microtron b.) betatron c.) cyclotron d.) X-ray tube
c.) cyclotron the cyclotron accelerates heavy particles like deutrons, neutrons and protons
all of the following might account for a beam's flattness deviating outside specifications, except: a.) flattening filter shift b.) target position shift c.) incorrect mirror angulations d.) fluctuation of current
c.) incorrect mirrow angulations flatness of the beam is influenced by correct position of the flattening filter or target and fluctuations in current. mirror angulation influences light field and radiation agreements NOT the flattening filter
in early generation kV therapy machines, the quality of the photon beam could be increased by: a.) increasing the mA b.) decreasing the half value layer of material c.) increasing the filtration d.) decreasing the kVp
c.) increasing the filtration low energy x-ray machines would use filters to harden the beam, filtering out low energy radiation. increasing the filtration would sift out more soft radiation therby increasing the overall quality and penetration power of the beam
cobalt beam output must be checked: a.) daily b.) weekly c.) monthly d.) annually
c.) monthly as a decaying source with a long half-life, output is recommended to be checked monthly; expected change is a decreas of 1.09% per month
which of the following radioisotopes is a pure emitter? a.) cesium -137 b.) cobalt-60 c.) phosphorus-32 d.) iodine-131
c.) phosphorus-32 phosphorus32 emits beta radiation strictly, cesium, cobalt, and iodine emit gamma radiation
the exact position of the source in the applicator can be checked by (circle all correct): a.) visual inspection b.) measuring the AKS strength of the source c.) taking a radiograph d.) none of the above
c.) taking a radiograph
. the teletherapy cobalt machine has a beam stopper. the purpose of the beam stopper is to: a.) prohibit the primary beam from penetrating adjacent wall and ceiling b.) prohibit scatter radiation in the tx room c.) act as a counter-balance to the heavy gantry head d.) a and c are correct
d.) a and c are correct prohibit the primary beam from penetrating adjacent wall and ceiling and act as a counter-balance to the heavy gantry head
the purpose of the flattening filter in the linac is to: a.) direct the stream of electrons out toward the collimator opening b.) prevent deflection of microwaves c.) evenly distribute and spread out the raw electron beam across a specified area d.) evenly distribute the energy of the photon beam across the specified area
d.) evenly distribute the energy of the photon beam across the specified area
the BAT system uses____ energy to localize the treatment target. a.) x-ray b.) microwave c.) radiofrequency d.) ultrasound
d.) ultrasound the BAT system is a bedside ultrasound unit used for daily target localization
as the SSD increases, penumbra (increases OR decreases.
decreases the size of penumbra and source to diaphragm distance are inversely proportional. as distance from the soruce and diaphragm increases, the penumbra region decreases
. true or false: the effective energy of a photon beam can be increased by: increasing the beam on time
false the effective energy of the photon beam is not influenced by how long the beam is on, or by the current (amount of electrons coming across the tube). the effective energy is infleunced by increasing the potential across the tube (voltage and supllemental energy boosts from alternating frequency waves).
true or false: the effective energy of a photon beam can be increased by: increasing the tube current
false the effective energy of the photon beam is not influenced by how long the beam is on, or by the current (amount of electrons coming across the tube). the effective energy is infleunced by increasing the potential across the tube (voltage and supllemental energy boosts from alternating frequency waves).
what three linac components monitors radiation beam uniformity by monitoring and controlling symmetry and flatness.
ion chamber, scattering foil, flattening filter
what component of the linac is responsible for the electron beam is spread out uniformly over the field size._____
scattering foil
what part of the linac produces high voltage and high power electrical pulses to generate microwave power?
the modulator
. true or false: the effective energy of a photon beam can be increased by: increasing the tube potential
true the effective energy is infleunced by increasing the potential across the tube (voltage and suplemental energy boosts from alternating frequency waves).
what 2 part of the linac has microwaves travel through those components and are prevented from reflecting backward?
waveguide and radiorequency driver
