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TD 5/5 indicates the dose required to cause 5% chance of injury to people irradiated within ______ of exposure
- Better definition:
- The radiation dose that would likely cause
- 5 % of an exposed population to realize a adverse late effect in the 5 years following exposure
*LD 50/30 indicates the dose likely to cause DEATH in 50% of the population within______following exposure.
Whole kidney TD 5/5
*TD 5/5 Whole brain:
The period of organogenisis normally occurs during weeks______of fetal development.
*The radiosensitivity in tissue may be enhanced by:
increasing the oxygen in tissue
The most radioresistant phase of cellular division:
*The immediate symptoms that appear after an acute radiation exposure are called:
The laws of B & T state that ionizing radiation is more effective against cells that are(name 3):
- 1)actively mitotic
- 3)Have a long mitotic future
*The development of radiation induced cancer is known as a (deterministic/stochastic) effect.
Nausea is associated with the ______syndrome.
*Radiation interacts with tissue (uniformly, randomly).
*Cells are most sensitive during the ____phase of division.
The fraction of cells actually progressing through cycles of division is known as the (growth/surviving) fraction.
*The period over which radiation is delivered is referred to as the:
*Cells that are undifferentiated and have high mitotic rate are (radiosensitive, radioresistant). Name 2 examples:
- blood cells, germ cells
*Cells that are moderately differentiated and have a moderate mitotic rate have ______sensitivity. Name 3 examples:
- intestinal cells, myelocytes, skin
*Cells that are moderately differentiated and have low mitotic rate are (radiosensitive, radioresistant). Name 2 examples:
- liver mature bone cells
*Cells that have a low to a nonexistent mitotic rate, are well diferentiated, and are (radiosensitive, radioresistant). Name 2 examples:
- nerves, adult brain
Survival curves: low LET and high LET:
*Erythematous skin reactions during fractionated radiation therapy are seen as a result of:
Vascular dilation in the area
Epilation initially observed during standard fractionation schemes at an aprx dose of:
(1 1/2-2 weeks)
*The production of free radicals most often occurs from the irradiation of_____.
Fractionated doses are better tolerated than single doses because:
tissue repair occurs between exposures
*Which of the following is an effect of radiation on DNA:
b. increased viscosity
c. free radical formation
d. Hydroxyl formation
- a. cross-linking
- b. increased viscosity
- c. free radical formation
- d. Hydroxyl formation
As the dose of radiation increases, tissue recovery time(increases, decreases).
*In linear or nonlinear threshold dose response curves, the following is true of the response:
Response may not occur at low doses
*The average energy deposited per unit path length in a medium by ionizing radiation as it passes through that medium best describes:
The most radiosensitive tissue group among the following sites is:
a. central nervous system
b. alimentary tract
d. cardiovascular system
- a. central nervous system
- b. alimentary tract
- c. muscle
- d. cardiovascular system
*The 4 R's of radiobiology:
The whole body syndrome likely to be observed following a single dose of 1-10 Gy is the _____syndrome.
Whole body irradiation syndromes:
dose range: ____
Time until death without rescue:______
Whole body irradiation syndromes
dose range: ____
Time until death without rescue:______
Whole body irradiation syndromes:
dose range: ____
Time until death without rescue:______
*Which of the following would be a late or stochastic radiation response?
b. bone marrow suppression
c. skin erythema
d. lung cancer
- a. sterility
- b. bone marrow suppression
- c. skin erythema
- d. lung cancer
Which of the following is a more accurate representation of cell radiosensitivity?
c. LD 50/30
*The standard radiation used to determine RBE is:
250 keV x-ray
*Without medical intervention, a person exposed to a single whole body dose of ___ will die within 10 days.
a. 10 Gy
b. 0.25 Gy
c. 1.0 Gy
d. 1.0 cGy
- a. 10 Gy
- b. 0.25 Gy
- c. 1.0 Gy
- d. 1.0 cGy
*Irradiation of the salivary glands my lead to permanent xerostomia above doses of _____with typical 2 Gy/5 per week fractions
(??I have 50 Gy for salivary gland TD 5/5)
*Tissue injury ____as the volume of tissue irradiated increases.
Which is lower-the TD 5/5 or the TD 50/5 for the colon?
*The TD 5/5 is (higher, lower) for immature bone than mature bone.
The TD 5/5 is (higher, lower) for bone marrow irradiation in a single dose than in a fractionated dose.
*An anticipated response to radition dose above 55 Gy to the colon is:
*Regarding nonstochastic effects(choose any or all):
1)the effects are never seen in the one exposed
2) the effects are never seen in future generation
3)The probability of occurring is related to the dose
4)The severity of effects is related to the dose
- 1)the effects are never seen in the one exposed
- 2) the effects are never seen in future generation
- 3)The probability of occurring is related to the dose
- 4)The severity of effects is related to the dose
The most radiosensitive tissue group is:
a. plasma membrane
b. alimentary tract
- a. plasma membrane
- b. alimentary tract
- c. lens
- d. urinary
*The part of the cell between the membrane and the nucleus is known as the:
The effect of radiation is influence by(pick any or all):
2)volume of tissue irradiated
- 1)radiation type
- 2)volume of tissue irradiated
- 4)total dose
*The primary function of the cell nucleus is:
housing DNA and RNA
*Redness of the skin caused by permeability of the capillaries:
Grade 1 toxicity for the skin caused by depopulation of clonogenc cells in the epidermis.
*Division of total dose into smaller doses given at intervals:
*Liberated constituent of a molecule:
*The main objective of radiation protection is the:
prevention of radiation induced stochastic and deterministic effects
A grade 1 morbidity for the colon would indicate:
change in frequency of bowel movements
*A grade 3 morbidity for the skin would indicate:
confluent moist desquamation
*Somatic effects are:
the effects limited to the exposed individual
Ellis' formula did not accommodate:
different tissue types with varying sensitivites
Conventional fractionation was based on experiments performed to:
*When irradiating the spleen for metastatic disease, hypofractionation may be employed, whereas with primary H&N cancers may employ hyperfractionation. What is the rationale for this difference?
H&N cancers originating in the mucosa have a high mitotic activity and short intervals between mitotic events. Hyperfractionation attempts to delay mitotic activity and synchronizw cells to most sensitive phases of division to increase cell kill. Hypofractionation provides the opportunity to cause cell death to any malignant cell infiltrating the organ and at the same time giving sensitive cells time to repair.
*There is a patient scheduled for 6 wks of RT with standard fractionation. After wk 2 he informs you that he will be taking a 3 wk cruise and plans to complete therapy when he returns. What would your counseling include?
The 3 wk break gives abnormal and normal cells adequate time to repopulate. An adjustment in his total dose and fraction size may need to be made using the BED formula due to his prolonged absence. The original 6 wks may need to be adjusted.
*Regarding tolerance of tissue, as the volume of tissue increases, the tolerance dose_____.
The standard proposed unit for "rets" in Ellis' formula held the value of:
*Lethal damage is
irreparable and leads to cell death
At doses of ___Gy, you may see latent stricture in the esophagus during standard fractionation
*Ionizing radiation can disrupt chemical _____ in important biologic materials.
What are the DNA nitrogenous bases?
adenine, thymine, guinine, cytosine
(uracil replaces cytosine in RNA)
*The structure of DNA is referred to as a:
Somatic cellular division takes place through the process of:
*(germ cell replicate through meiosis)
*Which phase of the cell cycle occurs between the two gap phases, G1 and G2?
What is the proper order of the steps of cellular division?
G1, S, G2, M
*A cell survival curve usually has:
shoulder and a straight portion
*What dose effect curve implies that if radiation is doubled, the biologic effect is doubled?
*Cellular growth and development is called:
The key target in the human cell is the :
*Cells are about ___% water.
On the cell survival curve, the "n" number denote:
the extrapolation number
*Radiation would have less effect on a cell if given:
over a longer period of time
According to the current recommendations, which of the following would have the highest dose limit:
a. lens of the eye
b. the hands of a member of the general public
c. the embryo-fetus
d. the hands of a pregnant therapist
- a. lens of the eye
- b. the hands of a member of the general public
- c. the embryo-fetus
- d. the hands of a pregnant therapist
*According to the current recommendations, the guidelines levels for cumulative exposures for a 30 yr old occupational worker with three yrs experience:
300 mSv (30 rem)
*It is recommended that radiation exposure to the fetus should not exceed___for the entire gestation.
Which of the following would not normally be used to monitor radiation dose exposure:
a. film badge
c. cutie pie
d. pocket dosimeter
- a. film badge
- b. TLD
- c. cutie pie
- d. pocket dosimeter
*The roentgen is a unit of measurement that specifies the ____of air by x-rays or gamma radiation.
*The term quality factor(Q):
varies with different types of radiation
Any container in which radionuclides are transferred, stored, or used must have a label saying:
*The organization in the US that is principally responsible for recommending radiation dose limits is the ___.
The annual dose limit for occupational worker's lens is ___.
15 rem (150 mSv)
*The annual dose limit for the occupational worker's skin is____.
50 rem (500 mSv)
The fraction of time that a radiation beam is directed at a specific barrier is the ____.
*The annual radiation dose to the lung from radon gas is estimated to be ____
(2 mSv, 200 mrem)
a)The survey meter shows an exposure rate of 300 mrem/hr at 3 ft from the source during the loading of a Fletcher intraacavitary applicator, and the duration of the procedure is expected to be 6 minutes, what would the exposure be for person standing 3 ft form the sources?
b)What would the exposure be for the same person if the where 2 ft from the source?
- a) 6 min =0.1 hr
- 0.1 x 300 mrem= 30 mrem
*The dose rate is 0.5 rem/min at 40 ft away from a source. An office will be constructed 20 ft away the source. An individual will occupy this office 8 hrs/day 5 days/wk and is allowed to receive 10 mrem/wk. How many 10th value layers of material will be needed?
- 40 hrs x 60 min =2400 min
- I2 =0.5(40/20)2=2 rem/min x 2400 min=4800 rem/wk at 2 ft
5.7 tenth value layers
- 4800 rem= 4,800,000 mrem
- 0.1x =0.000002
- Log(0.1x )= Log(0.000002)
A linac accomodates 35 patients/day, 5 days a week. The average number of fields per patient is 4 and the average dose per field is 45 cGy. Calculate the workload:
35 x 5 x 4 x 45 cGy=31500
*If the HVL for Co-60 is 1.1 cm of lead, what percent of transmission is expected using 4.4 cm of lead as a barrier?
Compare how dose is measure using a film badge and a TLD:
- Film Badge: Crystals in the emulsion on the film badge are transformed, film is processed-density is measured with a densitometer to measure dose
- TLD: Lithium fluoride crystals trap electrons when exposed in the TLD. When the TLD is heated, trapped electrons are released in the form of light.Light photons are proportional to dose
*Compare how exposure is measured in using an ion chamber and a Fricke dosimeter:
- Ion chamber measure ionization of air, or migration of charges between charged plates by the liberation of electrons.
- Fricke dosimeter relies on chemical reactions. Ferrous sulfate(Fe2+) is oxidized when exposed to radiation and becomes Fe3+ ions.
Dose equivalent is measured in units of:
Sievert (or rem)
Maximum exposure rate at a specific distance from the patient following the insertion of radioactive sources can be measured with TLDs
(ION CHAMBER USED)
The requirement for barrier protection in walls/ceiling for a given radiation is reduced when there is a beam stopper on the treatment unit.
The agency that regulates the use of radiation producing machines is the:
*An example of a deterministic effects is:(pick one or any)
- 2)Genetic effects
- 3)Birth Defects
The radiation detection device that would be useful in locating a lost radioactive source would be:
*The largest dose from natural background radiation comes from:
*The amount of energy absorbed in a medium is expressed in units of:
*One major contributor of _____radiation is Potassium-40.
*_____radiation varies according to the composition of the soil.
The two main types of background radiation are:
cosmic and terrestrial
*The exposure from cosmic rays at sea level is lower than the exposure in Denver because:
The altitude is higher in Denver
*What quantity is measured directly by the TLD?
*Appropriate disposal of radioactive sources include:(Pick any or all)
1)Transfer to authorized recipient
*The radioactive source inventory room should have a sign that reads:
The workload describes:
How much the primary beam is in use
*In the construction of a new RT center, the choices for primary barriers include concrete, lead, and iron. Measure for measure, I would need more_______for adequate absorption.
The HVL for a 6x beam is 22 mm of lead. It's linear attenuation coefficient is:
- μ=.693/22=0.0315 mm-1
*When a radiation worker is away from work, it is best to store his film badge:
In a safe place away from the source of radiation
*Patients undergoing I131 thyroid ablation should not be released from the facility until survey meters read less than ___mrem/hr at ___ m
5 mrem/hr at 1 m
Internal radiation exposure comes from radioactive materials in our body such as:
*Radioactive sources should be transported around the treatment facility in:
Nursing and other pt care staff caring for pt undergoing LDR brachy should:
Use standard precautions and perform duties as quickly as possible
*A monthly radiation exposure report says an employee received 0.5 Sv. If the source of exposure was gamma radiation, the translation to absorbed dose would be:
0.5 Sv=0.5 Gy
*How many HVLs reduce the exposure to 2%?
- 0.5x = 0.02
- Log (0.5x ) = Log (0.02)
- -0.301 x= -1.698
- 5.6 HVL
Three TVLs reduce transmission to ____%:
*The shielding around stored radioisotopes must be adequete to radiation levels to less than ___mrem/hr at ___meter.
2 mrem/hr at 1 meter.
*The linear coefficient for a certain megavoltage beam using concrete is
0.089 cm-1 , what is the HVL? How much concrete is required to reduce the beam to 2%
- 0.5x =0.02
- Log(0.5x) =Log(0.02)
- x=5.64 HVLs x 7.8 cm=43.79
- 43.8 cm
*The protective housing around the cobalt source in the cobalt machine should allow transmission of ____% of the output.
*The source of electrons in the linac is the:
*Trimmer bars are attached to the collimator of the cobalt machine to reduce the effect of the:
*Calculate the width of the penumbra with an 80 cm SAD cobalt unit. Source diameter is 3.0 cm and the SDD is 40 cm. Treatment SSD is 75 cm.
*Calculate the width of the penumbra with an 80 cm SAD cobalt unit.
Source diameter is 2.0 cm and the SDD is 40 cm. Treatment SSD is 77 cm.
*The purpose of the flattening filter in the linac is to:
Evenly distribute the energy of the photon beam across a specified area
*What is the purpose of the magnetron and klystron in the linac?
They produce microwaves to accelerate electrons
*Trimmer bars attached to the cobalt collimator system should not be allowed closer than 15 cm from the patients skin. Why?
The trimmer bars and radiation produces secondary scatter. 15 cm is required to reduce the scatter to the patient.
As the distance from the source increases, the penumbra_____.
*As SDD increases, the penumbra_____.
- *Read question carefully: it says SDD NOT SSD
*The target in the linac is typically made of ___.
*Why do we use tissue compensators and wedges instead of bolus to compensate for irregular contours?
Because they preserve skin-sparing
*Which radioisotope is used for bone mets?
*The field light on the linac is intended to represent the:
area of radiation exposure
*The scattering foil is used in the ___beam mode.
*The cyclotron may produce____beams.
*Energy range of early generation superficial therapy machines:
*The linc generates a high-energy photon or electron beam by:
accelerating charged particles in a linear path
*Geometric penumbra , characterictic of the cobalt beam increases with:
Increasing source size and increasing distance from the source
Half-life of Radium-226
*Half-life of Iodine-125
Half-life of Cesium-137
*Half-life of Gold-198
*the Fletcher's Suite application is an example of:
intracavitary LDR brachytherapy
*The important QA test(s) associated with the light field are(circle all that apply)
1)field size accuracy
3)light and radiation field coincidence
- 1)field size accuracy
- 2)beam output
- 3)light and radiation field coincidence
*The target to patient skin distance is measured using:
An ODI indicator
*The tolerance for the localizing laser and ODI is:
*The constancy of the linac, when compared with benchmark values established during commissioning must be within:
Output constancy for electron and photons must be checked____.
*The x-ray beam in a linac must exhibit flatness within about:
*Which out daily on the of the following checks must be carried out on the cobalt machine:
1)function of the radiation room monitor
- 1)function of the radiation room monitor
- 2)door inerlocks
- 3)beam output
- 4)timer error
*Full calibration and overhaul of treatment equipment must be carried out_____.
*Localizing lasers on simulators must be within ____of isocenter.
*Microwave power is directed towards the accelerator guide:
*Electrons are produced by the
*At the end of acceleration, high energy electrons are focused toward the collimator by the _____.
*The electron beam is spread out uniformly by the______.
*Monitors radiation output:
*Produces high voltage and high power electrical pulses to generate microwave power:
*Microwaves travel through these components and are prevented from reflecting backward:
waveguide, radiofrequency driver
*To check for accuracy of gantry digital readouts, one could use:
a spirit level at 45-degree angle increments
*The linear scales on the treatment table are useful for:
- daily treatment setup
- translation of patient positions from simulation to treatment
*which of the following verifies the accuracy of the treatment dose delivery:
backup timer, radiation off switch, door interlock, and emergency off switch
*The process for testing a new linac against manufacturer's specifications is called:
*Gantry and collimator indicators should be within ____degree(s).
*All of the following might account for a beam's flatness deviating outside of specifications, except for:
1)flattening filter shift
2)target position shift
3)Incorrect mirror angulation
4)Fluctuation of current
- 1)flattening filter shift
- 2)target position shift
- 3)Incorrect mirror angulation
- 4)Fluctuation of current
*A mechanical distance indicator is used to verify:
Accuracy of the optical distance indicator
*Which of the following has the shortest half-life?
*Superficial treatment machines used short treatment distances because:
Percent dose depth falls of rapidly
Increasing the beam on time can increase the effective energy of the photon beam.
Increasing the tube potential can increase the effective energy of the photon beam.
*The machine that consists of short metallic cylinders divided into two D-Shaped cavities is known as the: