2 - Introduction to X-ray Principles

What is matter?

- anything that takes up space and has mass

- Can be solid, liquid, gas, and plasma

- Cannot be created or destroyed

- Smallest unique unit is the atom.

What are cells and molecules made up of?

Atoms, the basic building blocks of matter.

What are the three main subatomic particles that make up an atom?

Protons, neutrons, and electrons.

How are elements grouped?

Based on their number of protons.

What is the typical electrical charge of an atom?

Normally electrically neutral.

Bohr model of atomic structure

- Electrons orbit the nucleus (which contains protons and neutrons) in fixed energy levels (shells)

How to determine maximum number of electrons per shell

Use the formula 2n², where n is the shell number.

What is electron binding energy?

It's the strength of attachment of an electron to the nucleus.

Do inner shell electrons have higher or lower binding energies than outer shell electrons?

Higher binding energies.

What happens when electrons move to a higher shell?

It requires energy.

What occurs when electrons move to a lower shell?

It emits energy, often as electromagnetic photons.

What types of electromagnetic photons can be emitted when electrons move to a lower shell?

X-rays or gamma rays.

Ionization

It's the process where energy ejects an orbital electron, forming an ion pair: a positively charged atom and a free electron.

What is energy?

Energy is the ability to do work.

What are the different forms of energy?

Potential, kinetic, thermal, chemical, electromagnetic, and nuclear.

What is the smallest unit of energy?

A quantum.

What are the 3 ways to produce of electromagnetic (EM) energy

- Incandescence (excitation of electrical charges)

- Bremsstrahlung (sudden deceleration of electrical charges)

- Radioactive decay (disintegration of an atomic nucleus).

Photons

The smallest unit of EM energy. They have no mass, travel at the speed of light, and display wave-particle duality.

What is the speed of light?

Velocity (v): Speed of light

What is wavelength (λ) in wave parameters?

Distance between identical points on a wave

What is frequency (f) in wave parameters?

Number of wave cycles per second

What is the relationship between velocity, wavelength, and frequency?

v = λ × f

How are wavelength and frequency related?

Wavelength and frequency are inversely related

Radiation

Energy that travels through space. Matter exposed to it absorbs or is affected by the radiation.

Ionizing radiation

Ionizing radiation can damage tissue by ionizing atoms. It includes X-rays, gamma rays, and some UV light.

What are the properties of X-ray photons regarding visibility and penetration?

Invisible, highly penetrating

Do X-ray photons have mass or charge?

No mass, no charge

What determines the peak energy of X-ray photons?

Set by kVp

What effect can X-ray photons have on tissues?

Can cause ionization and tissue damage

How do X-ray photons travel and interact with matter?

Travel straight and scatter with matter

What phenomenon do X-ray photons cause in phosphors?

Cause phosphor fluorescence

Are X-ray photons affected by magnetic fields?

Not affected by magnetic fields

Can X-ray photons be focused with a lens?

Cannot be focused with a lens

What factors affect the absorption of X-ray photons?

Differentially absorbed by mass density, atomic number, and thickness of material

Voltage (V) in electricity

Voltage represents electric potential—the 'pressure' pushing electrons to flow. Higher voltage = more energy per electron.

Current (I) in electricity

Current is the flow of electrons through a conductor. Measured in amperes (A).

What is Direct Current (DC)?

Electrons flow in one direction, steady or fluctuating.

What is Alternating Current (AC)?

Electrons oscillate, reversing direction regularly.

How often does Alternating Current (AC) reverse direction in North America?

60 times per second.

Transformer

A transformer changes voltage and current in AC circuits.

Types of transformers

Step-up: Increases voltage, decreases current; Step-down: Decreases voltage, increases current.

Main components of an X-ray system

Wall Switch, Control Panel, Generator, X-ray Tube, Beam Modifiers (Collimation), Collimator, Bucky.