black and yellow Flashcards
1 mSv is equal to ___ rem
0.1 rem
if the total body is exposed to a dose of 4500 cGy in a single exposure, the most likely cause of death would be
cerebral edema
by what factor does the intensity decrease when someone moved from 10 meters to 20 meters away from a radioactive source
4
what is the allowable cumulative exposure for a radiation worker
one rem times the worker’s age in years
what is a interaction between an incident photon and a atomic nucleus
pair production
a star shot on a linear accelerator is performed to test the rotational axis of the :
collimator, couch, gantry
the average photon beam energy produced by a 6 MV linear accelerator is approximately ___
2 Mv
which tissues arise from mesenchymal stem cells
blood, cartilage, bone
in bremsstrahlung radiation, the incoming electron
is deflected by the nucleus of the atom
exposure is
measure of ionization in air
which does not ionize directly
neutron
the half life of cobalt is
5.3 years
linear accelerators have which of the following type of target
transmission
klystrons and magnetrons are
microwave sources
lead alone could be used in room shielding when the following interactions predominate
photoelectric
the angle of the mandible is generally located at which cervical vertabrae
c3
monitoring of dose rate and field symmetry is best accomplished by using a
ion chamber
in the pancreas where do most tumors originate
head
effects for which the severity of the effect in the individual varies with the radiation dose, and a threshold usually exists is called
deterministic
what devices are used for area surveys
ionization chambers and parallel-plate chambers
according to the NRC regulations, what is the MPD for those who are NOT trained radiation workers
0.1 rem/year
what is the largest paranasal sinus cavity
maxillary
what is purpose of the scattering foil in a linear accelerator?
provide uniform electron fluence
photoelectric interactions of a 60 keV beam are greatest in
bone
which of the following structures is most radiosensitive (susceptible to long term damage at the lowest dose)?
lung
where is sarcoma most likely to metastasize?
lung
with breast cancer which of the following patterns of lymph node drainage occurs most often
axillary
the most common site for metastatic spread of carcinoma of the penis is the
inguinal nodes
hypo fractionation is
treatment given in fewer fractions than standard
the epiglottis is a flap of cartilage that folds back to cover the entrance of the
larynx
the inguinal lymph nodes are generally included in which of the following treatment sites
vulva
nasopharyngeal tumors drain through what lymph node group first
posterior cervical
what is the most common site of spinal cord compression
thoracic spine
the tolerance dose of the whole liver using standard fractionation is
2500-3000 cGy
the degree of cellular differentiation and rate of tumor growth is the
grade
a multiple field technique is generally utilized when treating pituitary tumors, opposed to two lateral fields, to avoid an excessive dose to which of the following structures
temporal lobes
the common iliac nodes are generally found around the level of
L5
what external landmark can be used to localize the top of the larynx
thyroid prominence
when treating the maxillary antrum, which neighboring structure is most sensitive
eye
the trachea bifurcates at the level of
T4/T5
what external landmark can be used to locate the carina
angle of louis
the vallecula is located at the level of which of the following anatomical structures
hyoid bone
the inferior border of the larynx port for a vocal cord carcinoma should anatomically correspond to
cricoid cartilage
if you are using a gonad shield when treating a patient with seminoma on a 6 MV linear accelerator, why can’t all of the scatter to the testicles be eliminated
internal scatter from the patient cannot be eliminated
the patient’s chin is tilted down when treating a pituitary gland to avoid the
eyes
what areas are generally encompassed in a German helmet radiation port when treating acute lymphocytic leukemia
cribiform plate, meninges, posterior retina
a strontium 90 applicator may be useful in the treatment of which of the following diseases of the eye
pterygium
the tolerance dose for the whole brain using standard fractionation is approximately
4500 cGy
which of the fooling is the most radiosensitive structure
liver
a non osseous tumor of the bone marrow is
multiple myeloma
the false vocal cords are located __ to the glottis
superior
what fraction would you multiply an electron energy by to estimate the 90% isodose range
1/4
why is a tumor of the parotid gland frequently treated with a ipsilateral beam arrangement
to avoid the other parotid
what is the therapeutic ratio if the normal tissue tolerance is 5000 cGy and the lethal dose for the tumor is 4000 cGy
1.25
backscatter factors are independent of
SSD
the largest salivary gland in the head and neck is the
parotid
the practical range for 18 MeV electrons is
9 cm
the most common presentation of superior vena cava syndrome is
distended veins in the head and neck
the rapid fall off of dose around a cesium 137 source in a 5 cm radius of tissue is primarily due to
the inverse square law
when manipulating a CT image, increasing the width of the window:
decreases contrast and increases latitude
the amount of energy transferred to a material per unit length of travel
LET
what is the dose at which you generally reduce the field off cord when treating a head and neck cancer
4500-5000 cGy
RBE is dependent on which of the following
radiation quality, radiation dose per fraction, tissue irradiated
when dealing with OER and anoxic tissue which would be the most effective
protons
what normal organ would be at most risk when treating a maxillary sinus tumor
eye
what is the most potent chemical modifier of radiosensitivity to X and gamma rays
oxygen
which of the following is required for fabricating custom cut blocks
source image distance and source to block tray distance
two wedges are used to treat a maxillary antrum tumor through an anterior and lateral port. what part of the wedges should be adjacent
thick side anterior to thick side laterally
to verify that the radiation field and the light field are aligned on a 10 Mv linear accelerator you could use the following
readi-pak xray film, a pen, and a ruler
for photon energies between 0.150 MeV and 10 Mev the predominant type of interaction is
compton
what is the main advantage of using cerrobend over lead in custom blocking
it has lower melting point
portal verification is defined as the documentation of
the actual treatment using film or electronic imaging devices
you have an extremely large patient and you must treat two lateral pelvic fields. what technique will give you the most even dose distribution through out the treatment fields
SSD technique, moving the treatment table as far away from the source as possible
the standard amount of time that should elapse between two radiation therapy treatments given in the same day to the same site is
6 hours
MV portal films taken on a mega voltage machine have less contrast than kV films because the MV image results principally from
Compton interaction
after what time period would fibrosis generally appear following standard external beam therapy
one year
when treating the parotid gland with standard fractionation what is the tolerance dose that patients will develop xerostemia
2500-3500 cGy
when treating a patient with glioblastoma, he begins to experience nausea, dizziness, and blurred vision. which is the most likely reason
cerebral edema
deodorants should not be used on the skin within a radiation treatment field because the deodorants will
irritate sensitive skin
written defamation of character is best known as
libel
the normal platelet count is approximately
300,000 cc
bone marrow depression is most likely to occur when you are treating which part of the body
pelvic bones
the purpose of protective reverse isolation is
to protect in uninfected patient with lowered resistance
the two major energies associated with cobalt 60 beta decay are gamma energies of
1.17 and 1.33 MeV
the 80% isodose line can be estimated for electrons by dividing the energy by
3
if you compare the penumbra of a 6 mv linear accelerator operating in photon mode to the penumbra of a co60 teletherapy machine using the same ssd, what is true
the 6 mv linear accelerator has less penumbra than the co 60
percentage depth dose increases with
field size, ssd, and energy
for radiation workers the occupational dose is usually reported in
rem
which has the least radiosensitivity
mature cartilage
where are pan coast tumors located
mediastinum
the most radiosensitive stage of the cell cycle is
mitosis
the most common presenting signs of Wilms tumor is
non tender mass
in general when treating with radiation the proximal and distal margin around a soft tissue sarcoma should be at least
5 cm
the practical range of an electron beam
increases with increasing electron energy, about 1 cm for every 2 Mev, and about one half of the electron energy
mayneord’s factor is a correction for which of the following
distance
in a 120 degree arc rotation technique, the center of the high dose zone would be
displaced towards the surface
