Radiation Production and Characteristics: Particle Interactions with Matter

EXCITATION

It is the transfer of some of the incident particle’s energy to electrons in the absorbing material, promoting them to electron orbitals farther from the nucleus

Approximately 70%

______________ of charged particle energy deposition leads to nonionizing excitation

interacting with orbital electrons

Excitation occurs when charged particles lose energy by

Ionization

• It is the process of removing an orbital electron from an atom

• Occurs when charged particles lose energy by interacting with orbital electrons

Coulombic Repulsion/Attraction

The force pulling between the opposite charges that removes the electron

DE-EXCITATION

The electron will return to a lower energy level, with the emission of the excitation energy in the form of low-energy electromagnetic radiation

• Ejected Electrons

• Positively Charged Atom (Cation)

What results an ion pair?

DELTA RAYS

Sometimes the ejected electron ____________ possess sufficient energy

SECONDARY IONIZATIONS

produce further ionizations

SPECIFIC IONIZATION

It is the number of primary and secondary ion pairs produced per unit length of the charged particle’s path

IP/mm

What is the unit of Specific Ionization?

Linear Energy Transfer

LET

keV/um

The rate at which energy is locally transferred or deposited into a medium as a charged particle travels through it

DIRECTLY PROPORTIONAL

Linear Energy Transfer is a _____________ to specific ionizations, linked by the average energy expended per ionization event

• Xrays

• Gamma rays

Alpha particles have a higher LET than photons

Low Penetrability

• HIGH LET

• High dose from a single track

High Penetrability

• LOW LET

• Very low dose from a single track

COULOMBIC DEFLECTIONS

Are electrons follow tortuous paths in matter as the result of multiple scattering events caused by?

TRUE

Bremsstrahlung Interactions and Characteristic Interactions both produce xray photons?

ANODE

1?

ROTOR (+)

2?

PORT

3?

FILAMENT IN FOCUSING CUP

4?

GLASS ENVELOPE

5?

CATHODE

6?

NEGATIVE (-)

7?

BREMSSTRAHLUNG INTERACTION

A projectile electron that completely avoids the orbital electrons as it passes through may come sufficiently close to the nucleus

Slowed-down Radiation

A German word meaning?

Bremsstrahlung x-rays

• can be produced at any cathode electron energy

• are produced when a projectile electron is slowed by the nuclear field of a target atom nucleus

TRUE

Most xrays interactions in the diagnostic energy range are bremsstrahlung

HIGH ENERGY BREMSSTRAHLUNG XRAYS

LOW ENERGY BREMSSTRAHLUNG XRAYS

CHARACTERISTIC INTERACTION

Occurs when the interaction results in ionization of the target atom with the removal of an inner-shell electron

Characteristic x-rays

When the electron interacts with an inner-shell electron, ____________ are produced

K-Characteristic

Only the _____________ xrays of tungsten are useful for imaging

• CHARACTERISTIC XRAYS

• 70 keV

• 69.5 keV

_______________ can produced in tungsten target only when the kvp is set at _____ or greater because the binding energy of K-shell electron is _______

• PRODUCTION OF CHARACTERISTIC XRAYS

• AUGER ELECTRONS

During characteristic interactions, two possible outcomes can occur:

AUGER ELECTRONS

are secondary electrons ejected from an atom, releasing energy through a radiationless transition

It means there is no electromagnetic radiation like xrays, is emitted instead of the transition energy is transferred directly to the ejected Auger Electron

Define Radiationless transition?

K = 57.4

L-Shell

K = 66.7

L = 9.3

M-Shell

K = 68.9

L = 11.5

M = 2.2

N-Shell

K = 69.4

L = 12.0

M = 2.7

N = 0.52

O-Shell

K = 69.5

L = 12.1

M = 2.8

N = 0.6

O = 0.08

P-Shell

K = 69.5

L = 12

M = 3

N = 0.6

P = 0.1

Effective Energy of Xrays