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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