Radiation Numbers Flashcards
What dose equivalent rate defines a radiation area?
Radiation area means an area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 5 mrem (0.05 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.
What is the maximal dose rate limit for unrestricted areas?
The Nuclear Regulatory Commission (NRC) defines that the dose in any unrestricted area from external sources, exclusive of the dose contributions from patients administered radioactive material and released, does not exceed 2 mrem (0.02 millisievert) in any 1 hour. Unrestricted areas would include waiting rooms, hallways, file space, and secretarial areas.
An individual who has been administered unsealed by-product material may be released if the total effective dose equivalent to any other individual from exposure is not likely to exceed which of the following?
A licensee may authorize the release from its control of any individual who has been administered unsealed by-product material or implants containing by-product material if the total effective dose equivalent to any other individual from exposure to the released individual is not likely to exceed 0.5 rem (5 mSv).
What are considered major spills?
- Tc-99m and TI-201 = 100 mCi
- In-111, Ga-67, I-123 = 10 mCi
- I-131 = 1 mCi
What is the SI unit for absorbed dose?
The Gy
The SI unit of dose is the Gy. Dose is defined as the energy deposited per unit mass. The unit Gy is defined as 1 J/kg.
What is the threshold for permanent sterility in males from an acute exposure, approximately?
6 Gy
Which equipment should be used to test for Mo-99 breakthrough?
What ratio of Mo-99 to Tc-99m is required to pass the Mo-99 breakthrough test?
When eluting a Tc-99m generator, the mother isotope Mo-99 can contaminate the eluate. It is required to test for Mo-99 breakthrough in each eluate. This is done by placing the eluate in a special lead pig and placing it in the dose calibrator for a reading. The lead pig is then removed and the eluate is placed in a plastic sleeve for a reading in the dose calibrator. A ratio of Mo-99 to Tc-99m of less than 0.15 uCi Mo-99/mCi Tc-99m is required to pass the Mo-99 breakthrough test.
Regarding pregnant patients, how does CTPA radiation exposure to the mother compare to VQ scans?
Fetal dose in CTPA ranges between 0.013 and 0.026 mGy in early and 0.06-0.1 mGy in late pregnancy compared with perfusion scintigraphy with a fetal dose of 0.1-0.6 mGy in early and 0.6-0.8 mGy in late pregnancy. Aerosol ventilation scintigraphy results in 0.1-0.3 mGy. However, the breast radiation from CTPA is much higher to the mother than VQ scans. Use of shielding and automated exposure controls can help reduce CT radiation dose.
The unit of equivalent dose is given the special name of Sievert (Sv). What are the units of equivalent dose?
Equivalent dose has units of J/kg. In radiation protection, the quantity is given the special name of Sievert (Sv).
1 Sv = 1 J/kg, 1 Sv = 100 rem
In the SI system, exposure is indicated using which of the following units?
What is the historical unit of exposure?
Exposure is the quantity of charge in air due to ionization from x- or gamma rays. The unit of charge is the Coulomb, C. In the SI system, exposure is simply represented by the units C/kg. The historical unit of exposure is the roentgen (R).
What is the threshold for cataracts caused from an acute exposure to the eye (onset > 20 years)?
The threshold for cataracts from an acute exposure is ~ 0.5 Gy (50 rads).
Cataracts will develop over 20 years after acute exposure.
What is the limit to a general member of the public from activities performed involving the use of radiation?
What is the maximum dose an individual member of the public may receive from the release of patients injected with radioactive materials (e.g., thyroid ablation patients)?
The dose limit to a general member of the public from activities performed involving the use of radiation is 1 mSv (100 mrem).
5 mSv (500 mrem) is the maximum dose an individual member of the public may receive from the release of patients injected with radioactive materials.
What is the maximal permissible radioactivity ratio of Mo-99 to Tc-99m allowed in an elution from a Mo-99/Tc-99m generator?
The maximal permissible radioactivity ratio of Mo-99 to Tc-99m allowed in an elution from a Mo-99/Tc-99m generator is 0.15 uCi/mCi. This type of impurity is referred to as radionuclidic.
What is the unit of radioactivity?
The unit of radioactivity is the becquerel (Bq) or the curie (Ci), where 1 Ci = 3.7 x 10^10 Bq and 1 Bq = 1 disintegration per second. Activity is a measure of the number of transformations (decays) that a mass of radioactive atoms will undergo per unit time.
According to 10 CFR 20, the maximum dose a worker may receive to his or her whole body in a year is which of the following?
What is the dose limit for a pregnant worker?
How many rem in 1 Sv?
5 rem is the annual occupational dose limit to the whole body.
The dose limit for a pregnant worker is 500 mrem.
1 Sv = 100 rem, therefore 5 Sv = 500 rem, and 0.5 Sv = 50 rem.
