Rad Bio

Question 1

Which particles have direct DNA damage?

Answer 1

High LET radiation = alpha, neutrons and protons

Question 2

Which particles have indirect DNA damage?

Answer 2

Low LET radiation = x-rays, gamma rays, electrons They cause DNA damage via OH (free radicals)

Question 3

Which particles ar directly ionizing?

Answer 3

charged particles - alpha, beta, protons, electrons

Question 4

Whoch particles are indirectly ionizing?

Answer 4

neutrons, xrays and gamma rays

Question 5

What are the decay equations?

Answer 5

N = N₀2ⁿ

A_t = A₀e^{-0.693t/T_1/2}

Question 6

When does Beta decay occur?

Answer 6

Too many neutrons: neutron converted into a proton

Neutron → p⁺ +ß- + antineutrino + E(energy)

The mass remains constant but Z + 1

Question 7

What are example of pure beta emission and beta-gamma emission?

Answer 7

pure beta = ²³P

gamma-beta = ¹³¹I

Question 8

When does alpha decay occur? What is an example?

Answer 8

Large unstable nucleus → emits stable nucleus equiv to He atom

ex: ²²⁶Ra

Question 9

When does electron capture occur? How does it occur?

Answer 9

• too many protons but not enough energy to undergoe positron decay (<1.022 MeV)
• K-skell electron captured by nucleus → proton becomes neutron and neutrino (decreases Z) → electrons down move to K-shell and characteristic x-ray emitted but no particles emmited
• ex: ²⁰¹₈₁Tl₁₂₀ → ²⁰¹₈₀Hg₁₂₁

Question 10

When does positron decay (annihilation reaction) occur? What is an example?

Answer 10

• Too many protons and energey > 1.022 MeV
• proton → neutron + ß⁺ + neurtrino
  
  • positron annihilates with an electron → two 511 keV photons emitted 180 degrees apart
• Z -1
• ¹⁸₉F₉ → ¹⁸₈O₁₀ + ß⁺

Question 11

When does isomeric conversion occur?

Answer 11

Too much energy, no change in A or Z - associated with metastable species

Ex: ^99mTc → ⁹⁹Tc

Question 12

What is effective half life?

Answer 12

used to determine how long the radiopharmaceutical will be effective in a particular organ when considering its rate of disappearance from the body, (i.e., biological half-life) and its rate of decay (i.e., physical half-life)

1 ₌ 1 ₊ 1

t_eff t_b t_p

Question 13

what is the effective decay constant?

Answer 13

• l_eff = l_b+l_p

(l is supposed to be lambda but no lambda in this program )

Question 14

What is specific activity?

Answer 14

concentration of radioactivity per unit mass or volume of a pure radionuclide

Question 15

What is the SI unit of absorbed dose? What is the old unit and how do they relate?

Answer 15

• Gray = J/kg
• 1 Gy = 100 Rad or 1 Rad = 1 cGy

Question 16

What is the equivalent dose? What is the SI unit?

Answer 16

• Equal absorbed doses of different types of radiation produce different amounts of biologic damage, thus need a weighting factor: Ed = W_R x Absorbed dose
• SI unit = Sv
  
  • Sv = Gy x W_{<span>R</span>}

Question 17

What are lethal chromasome/chromatid abberations?

Answer 17

• Chromosome:
  
  • Dicentric abberation
  • Rings abberation
• Chromatid
  
  • anaphase bridge