Radiation Protection and Safety(Ch. 5)-Mosby Board Review Questions

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Radiation Protection and Safety(Ch. 5)-Mosby Board Review Questions
2014-03-08 17:28:46
Radiation Therapy
Mosby Board Review Questions,RTT Board Review
Radiation Protection and Safety(Ch. 5)-Mosby Board Review Questions
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  1. 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
  2. *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)
  3. *It is recommended that radiation exposure to the fetus should not exceed___for the entire gestation.
    0.5 rem
  4. Which of the following would not normally be used to monitor radiation dose exposure:
    a. film badge
    b. TLD
    c. cutie pie
    d. pocket dosimeter
    • a. film badge
    • b. TLD
    • c. cutie pie
    • d. pocket dosimeter
  5. *The roentgen is a unit of measurement that specifies the ____of air by x-rays or gamma radiation.
  6. *The term quality factor(Q):
    varies with different types of radiation
  7. Any container in which radionuclides are transferred, stored, or used must have a label saying:
    Caution-Radioactive Material
  8. *The organization in the US that is principally responsible for recommending radiation dose limits is the ___.
  9. The annual dose limit for occupational worker's lens is ___.
    15 rem (150 mSv)
  10. *The annual dose limit for the occupational worker's skin is____.
    50 rem (500 mSv)
  11. The fraction of time that a radiation beam is directed at a specific barrier is the ____.
    use factor
  12. *The annual radiation dose to the lung from radon gas is estimated to be ____
    0.2 rem/yr

    (2 mSv, 200 mrem)
  13. 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

    b) I2=30(3/2)2 =67.5 mrem
  14. *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

    • 4800 rem= 4,800,000 mrem
    • 4,800,000=0.000002
    • 0.1x =0.000002
    • Log(0.1x )= Log(0.000002)
    • -1x=-5.689
    • x=5.69

    5.7 tenth value layers
  15. 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

    315 Gy/wk
  16. *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?
    • 4.4/1.1=4 HVL
    • 0.54=0.0625

    6.25 %
  17. 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
  18. *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.
  19. Dose equivalent is measured in units of:
    Sievert (or rem)
  20. *T/F:
    Maximum exposure rate at a specific distance from the patient following the insertion of radioactive sources can be measured with TLDs

  21. *T/F
    The requirement for barrier protection in walls/ceiling for a given radiation is reduced when there is a beam stopper on the treatment unit.
  22. The agency that regulates the use of radiation producing machines is the:
  23. *An example of a deterministic effects is:(pick one or any)
    2)Genetic effects
    3)Birth Defects
    • 1)Carcinogenesis
    • 2)Genetic effects
    • 3)Birth Defects
    • 4)Cataracts
  24. The radiation detection device that would be useful in locating a lost radioactive source would be:
    Geiger-Muller counter
  25. *The largest dose from natural background  radiation comes from:
    • 1)Terrestrial
    • 2)Radon
    • 3)Cosmic
    • 4)Internal
  26. *The amount of energy absorbed in a medium is expressed in units of:
  27. *One major contributor of _____radiation is Potassium-40.
  28. *_____radiation varies according to the composition of the soil.
  29. The two main types of background radiation are:
    cosmic and terrestrial
  30. *The exposure from cosmic rays at sea level is lower than the exposure in Denver because:
    The altitude is higher in Denver
  31. *What quantity is measured directly by the TLD?
    absorbed dose
  32. *Appropriate disposal of radioactive sources include:(Pick any or all)
    1)Transfer to authorized recipient
  33. *The radioactive source inventory room should have a sign that reads:
    Caution:Radioactive Material
  34. The workload describes:
    How much the primary beam is in use
  35. *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.
  36. The HVL for a 6x beam is 22 mm of lead. It's linear attenuation coefficient is:
    • HVL=.693/μ
    • 22=.693/μ
    • 22μ=.693
    • μ=.693/22=0.0315 mm-1
  37. *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
  38. *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
  39. Internal radiation exposure comes from radioactive materials in our body such as:
  40. *Radioactive sources should be transported around the treatment facility in:
    shielded containers
  41. Nursing and other pt care staff caring for pt undergoing LDR brachy should:
    Use standard precautions and perform duties as quickly as possible
  42. *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
  43. *How many HVLs reduce the exposure to 2%?
    • 0.5x = 0.02
    • Log (0.5x )  = Log (0.02)
    • -0.301 x= -1.698
    • x=5.64
    • 5.6 HVL
  44. Three TVLs reduce transmission to ____%:
    • 0.13=0.001
    • 0.1 %
  45. *The shielding around stored radioisotopes must be adequete to radiation levels to less than ___mrem/hr at ___meter.
    2 mrem/hr at 1 meter.
  46. *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%
    • HVL=.693/0.089
    • 7.8 cm

    • 0.5=0.02
    • Log(0.5x) =Log(0.02)
    • -.301x=-1.69
    • x=5.64 HVLs  x 7.8 cm=43.79
    • 43.8 cm