1. Radioactivity. Basic physical characteristics in nuclear medicine.
Covers radioactive decay and the basic atomic structure behind it, then defines atomic number, mass number, nuclide, isotopes, isobars and isotones. Goes through alpha, beta minus, beta plus and gamma radiation with their properties and uses, and sets out half-life types including effective half-life with its formula. Also explains activity units, radiation energy, detection, attenuation, dose units and the three radiation protection principles. Includes a comparison table of gamma rays and X-rays and a summary table of common radionuclides.
Topic 1 of 50 in the MU Sofia syllabus for Nuclear Medicine (Medicine, Year 4). The free AceMed note covers it in 16 sections, about 704 words (6 min of reading), with 13 flashcards.
In this note
Topic 1: Radioactivity. Basic Physical Characteristics in Nuclear Medicine
Basic Atomic Structure
Important Definitions
Types of Radiation
Radioactive Decay
Half-life (Very Important)
Types of Half-life
Activity
Radiation Energy
Radiation Detection
Interaction of Radiation with Matter
Attenuation
Radiation Dose
Radiation Protection (Very Important)
Characteristics of an Ideal Diagnostic Radionuclide
Common Radionuclides to Remember
Topic 1: Radioactivity. Basic Physical Characteristics in Nuclear Medicine
Radioactivity is the spontaneous disintegration (decay) of an unstable atomic nucleus with emission of radiation in the form of alpha (α), beta (β), gamma (γ) rays or positrons to become more stable.
The process is random.
It cannot be accelerated or slowed by temperature, pressure or chemicals.
Every radionuclide has its own characteristic half-life.
Basic Atomic Structure
Every atom consists of:
1. Nucleus
Contains:
Protons (+ charge)
Neutrons (no charge)
Almost all atomic mass is here.
2. Electrons
Negative charge
Orbit around nucleus
Important Definitions
Atomic Number (Z)
Number of protons.
Example:
Hydrogen = 1
Carbon = 6
Iodine = 53
Determines the element.
Mass Number (A)
Total number of- Protons + Neutrons
Example- Carbon-14
6 protons 8 neutrons
Mass number =14
Nuclide
An atom with a definite number of
Protons
Neutrons
Energy state
Example- Technetium-99m
Isotopes
Same element
Same atomic number
Different number of neutrons
Example
I-123
I-125
I-131
All contain 53 protons.
Isobars
Different elements
Same mass number
Example
Carbon-14
Nitrogen-14
Isotones
Different elements
Same number of neutrons.
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