Radioactivity

Question 1

Radionuclide

Answer 1

• radioactive nucleus

Question 2

Radioactivity

Answer 2

• spontaneous transformation of an unstable isotope of a chemical element into an isotope of another element
• accompanied by the emission of particles, photons or both, resulting in a change of mass, electrical charge, energy state or a combo

Question 3

Alpha decay

Answer 3

• radionuclides emit heavy charged alpha particles composed of two protons and two neutrons

Question 4

Beta Decay

Answer 4

B-, B+ and e- capture

Question 5

B- decay

Answer 5

• emitted particle is an e-
• electron-beta-radioactive transformation
• electron appears during the spontaneous transformation of a neutron into a proton inside the nucleus
• simultaneous emission of a particle called antineutrino (e-)
• proton number increases by 1

Question 6

B+ decay

Answer 6

• emitted particle is a positron
• appears during the spontaneous transformation of a proton into a neutron inside the nucleus and the simultaneous emission of a particle called neutrino
• number of protons decreases by one

Question 7

Gamma radioactive transformation

Answer 7

• typical for nuclei after beta or alpha decay are in an excited state
• release excess energy by emitting one or two gamma particles (high energy photons)
• emission of excitation energy occuring within 1 us
• later than that, isomer transition
• excited state which lasts longer than 1 us is called metastable and it is denoted by a symbol ‘m’ after mass number

Question 8

Important characteristics of radionuclides used in nuclear medicine

Answer 8

• only beta and gamma used
• max energy E_β^max of beta-emission spectrum and energies E_γ1, E_γ2 of gamma rays
• half-life T_1/2 - short half-life used
• activity, A, rate of decay of substance
• A= -λN - where n is number of radioactive atoms and λ is the decay constant

Question 9

Radiopharmaceutics

Answer 9

• chemical compounds in which one of the chemical elements participates with its radioactive isotope
• technetium-99 is included in a big number of radio-pharmaceuticals
• inserted via intravenous injection and more rarely orally
• they are accumulated selectively in different tissues, organs and systems