Radioisotope Safety Guide 2025 – Health Physics & Radiation
Protection, Regulatory-Compliant Safety Manual
Annual average effective dose to the United States population from all sources of radiation
including background - correct answer 500-600 mrem (5-6 mSv)
ALARA - correct answer As Low As Reasonably Achievable
highest dose to the public should not exceed this much per year - correct answer 100
mrem/year (1 mSv/yr)
3 main measures to decrease radiation exposure - correct answer time, shielding, distance
Planned auditss must be carried out at least every ______ to ensure compliance of the
radiation protection program - correct answer 12 months
radiation area - correct answer a region where the effective dose could result in excess of 5
mrem (0.05 mSv) in 1 hour at 30 cm from a radiation source
high radiation area - correct answer area where the effective dose is up to 100 mrem (1 mSv) in
1 hour at 30 cm from the source. Audible or visible alarm is required to control access to this
region
very high radiation area - correct answer area where the absorb dose levels could exceed 500
rad (5 Gy) in 1 hour at 1 m from the source
caution radioactive materials - correct answer areas where sources of radiation are used and/or
stored must have this sign
unrestricted areas - correct answer reception, waiting areas, office spaces, reading rooms. Must
have dose rates less than 2 mrem in any one hour (20 microSv/h) or less than 100 mrem/yr (1
mSv/yr) excluding does contributions from patient's administered radioactive material
a room or area is not required to be posted with the caution sign if the sealed source radiation
level at 30 cm from the surface container or housing does not exceed - correct answer 5 mrem
(0.05 mSv) per hour
radio activity - correct answer unstable atomic nucleus transitions to a stable configuration by
emitting radiation
units of measure of radio activity - correct answer Curie or becquerel (Bq)
1 mCi = - correct answer 37 MBq
Alpha particles - correct answer positively charge particles consisting of 2 protons and 2
neutrons (a helium nucleus); doesn't travel far in tissues, have high linear energy transfer (LET)
, beta particles - correct answer electron or positron emitted from a decaying nucleus. Greater
penetration ability than alpha but can be stopped by plastic. Moderate linear energy transfer
(LET). Positron annihilation event generates two 511 keV gamma rays in opposite directions.
PET imaging
Gamma Rays - correct answer Electromagnetic waves emitted from the nucleus with low linear
energy, have high penetration ability and can pass through several centimeters of lead
X rays - correct answer Electromagnetic waves created by beta minus particles that interact
with atomic nuclei and undergo Brehmssgrahlung radiation
Neutron radiation - correct answer Free neutrons emitted from the breaking apart of an atomic
nucleus they can penetrate most materials and can cause chain nuclear reactions
Physical half-life (Tp) - correct answer The time it takes for 50% of the radionuclide nuclei to
decay
Biological half-life (Tb) - correct answer The time it takes for the radionuclide or
radiopharmaceutical concentration to reduce to 50% of the original concentration
Effective half-life (Te) - correct answer Takes them to account the physical and biological half-
life values represents the combined effects of physical nuclear decay and biological excretion
Exposure - correct answer The amount of radiation present in the air with units of Roentgen (R)
or coulomb/kilogram (C/kg)
Typical measuring instruments of exposure - correct answer Geiger Mueller counters or
ionization chambers
Absorbed dose - correct answer Amount of radiation, absorbed by tissue, which is scaled by the
mass of the tissue. Units Gray (Gy) or rad
100 rads = - correct answer 1 Gy
Linear energy transfer - correct answer Rate of energy transferred by radiation to a medium per
unit of length, the higher this is the higher rate of energy released to tissue. Highest is alpha or
neutron.
Dose equivalent - correct answer Quantifies the relative biological effectiveness of different
types of emitted radiation on human tissue. Radiation with higher linear energy transfer causes
greater tissue damage than lower, and therefore correlates with higher relative biological
effectiveness. Units Sieverts (Sv) or Roentgen equivalent man (rem)
Weighing factor for x-rays, gamma rays, beta particles - correct answer One
Does equivalent calculation - correct answer Absorbed dose multiplied by quality factor
Weighing factor for slow neutrons when calculating dose equivalent - correct answer Five
Protection, Regulatory-Compliant Safety Manual
Annual average effective dose to the United States population from all sources of radiation
including background - correct answer 500-600 mrem (5-6 mSv)
ALARA - correct answer As Low As Reasonably Achievable
highest dose to the public should not exceed this much per year - correct answer 100
mrem/year (1 mSv/yr)
3 main measures to decrease radiation exposure - correct answer time, shielding, distance
Planned auditss must be carried out at least every ______ to ensure compliance of the
radiation protection program - correct answer 12 months
radiation area - correct answer a region where the effective dose could result in excess of 5
mrem (0.05 mSv) in 1 hour at 30 cm from a radiation source
high radiation area - correct answer area where the effective dose is up to 100 mrem (1 mSv) in
1 hour at 30 cm from the source. Audible or visible alarm is required to control access to this
region
very high radiation area - correct answer area where the absorb dose levels could exceed 500
rad (5 Gy) in 1 hour at 1 m from the source
caution radioactive materials - correct answer areas where sources of radiation are used and/or
stored must have this sign
unrestricted areas - correct answer reception, waiting areas, office spaces, reading rooms. Must
have dose rates less than 2 mrem in any one hour (20 microSv/h) or less than 100 mrem/yr (1
mSv/yr) excluding does contributions from patient's administered radioactive material
a room or area is not required to be posted with the caution sign if the sealed source radiation
level at 30 cm from the surface container or housing does not exceed - correct answer 5 mrem
(0.05 mSv) per hour
radio activity - correct answer unstable atomic nucleus transitions to a stable configuration by
emitting radiation
units of measure of radio activity - correct answer Curie or becquerel (Bq)
1 mCi = - correct answer 37 MBq
Alpha particles - correct answer positively charge particles consisting of 2 protons and 2
neutrons (a helium nucleus); doesn't travel far in tissues, have high linear energy transfer (LET)
, beta particles - correct answer electron or positron emitted from a decaying nucleus. Greater
penetration ability than alpha but can be stopped by plastic. Moderate linear energy transfer
(LET). Positron annihilation event generates two 511 keV gamma rays in opposite directions.
PET imaging
Gamma Rays - correct answer Electromagnetic waves emitted from the nucleus with low linear
energy, have high penetration ability and can pass through several centimeters of lead
X rays - correct answer Electromagnetic waves created by beta minus particles that interact
with atomic nuclei and undergo Brehmssgrahlung radiation
Neutron radiation - correct answer Free neutrons emitted from the breaking apart of an atomic
nucleus they can penetrate most materials and can cause chain nuclear reactions
Physical half-life (Tp) - correct answer The time it takes for 50% of the radionuclide nuclei to
decay
Biological half-life (Tb) - correct answer The time it takes for the radionuclide or
radiopharmaceutical concentration to reduce to 50% of the original concentration
Effective half-life (Te) - correct answer Takes them to account the physical and biological half-
life values represents the combined effects of physical nuclear decay and biological excretion
Exposure - correct answer The amount of radiation present in the air with units of Roentgen (R)
or coulomb/kilogram (C/kg)
Typical measuring instruments of exposure - correct answer Geiger Mueller counters or
ionization chambers
Absorbed dose - correct answer Amount of radiation, absorbed by tissue, which is scaled by the
mass of the tissue. Units Gray (Gy) or rad
100 rads = - correct answer 1 Gy
Linear energy transfer - correct answer Rate of energy transferred by radiation to a medium per
unit of length, the higher this is the higher rate of energy released to tissue. Highest is alpha or
neutron.
Dose equivalent - correct answer Quantifies the relative biological effectiveness of different
types of emitted radiation on human tissue. Radiation with higher linear energy transfer causes
greater tissue damage than lower, and therefore correlates with higher relative biological
effectiveness. Units Sieverts (Sv) or Roentgen equivalent man (rem)
Weighing factor for x-rays, gamma rays, beta particles - correct answer One
Does equivalent calculation - correct answer Absorbed dose multiplied by quality factor
Weighing factor for slow neutrons when calculating dose equivalent - correct answer Five
