physics cluster 1

RADIATION

-       Emission or transmission of energy in the form of wave or practice through space or medium.

-       Energy that travel as wave/particle.

IONIZING RADIATION

-       A type of radiation capable of ejecting/removing an orbital electron from the orbit of an atom with which interacts.

-       It should be a high energy radiation to remove an electron to its orbit. This is what we called the Electron Binding Energy.

Ionic Binding

Gaining of electron

Covalent Binding

Sharing

NON-IONIZING RADIATION

-       A type of radiation that doesn’t have enough energy to remove an orbital electron.

X-RAYS

Symbol: “X”

Mass: 0

Charge: 0

Origin: electron cloud

Energy: 0-25 MeV

Useful in Radiologic interest

Can’t penetrate Lead(Pb)

GAMMA RAYS

Symbol: “Y”

Mass: 0

Charge: 0

Origin: nucleus/radioactive nuclei

Energy: 0-5 MeV

Useful in Radiologic interest

Can’t penetrate Lead(Pb)

ALPHA PARTICLES

Equivalent to a helium atom

2 protons, 2 neutrons

Symbol: “a”

Mass: 4 amu

Charge: +2

Origin: nucleus of heavy radioactive nuclei

Energy: 4-7 MeV

Can’t penetrate paper

BETA PARTICLE

Light particles

Symbol: “B”

Mass: 0 amu

Charge: -1 or +1

Origin: nucleus of radioactive nuclei

Energy: 0-7 MeV

Product: position (+) and negatron (-)

ATOM

-       Smallest unit of an element

NEUTRON

-       An UNCHARGED ATOMIC PARTICLE that has a mass nearly equal to that proton that is present in all known atomic nuclei except hydrogen nucleus.

-       No charge/neutral

-       Discovered by JAMES CHADWICK in the Year 1932.

PROTON

-       POSITIVELY CHARGED SUB ATOMIC PARTICLE found in the nucleus together with neutron.

-       Discovered by ERNEST RUTHERFORD in the Year 1919 by BOMBARDING NITROGEN NUCLEI with ALPHA PARTICLES.

ELECTRON

-       NEGATIVELY CHARGED SUBATOMIC PARTICLE that is essential in ionization.

-       Discovered by J.J. THOMPSON in the Year 1897 by using CATHODE RAYS IN A HIGH-VACUUM TUBE.

Cosmic ray

29 mRem) - sun and star

Internal deposited radionuclides

39 mRem) - Potassium 40

Radon

198 mRem) - concrete, bricks, gypsum wallboard

Terrestrial radiation

29 mRem)

Uranium

thorium

Radionuclide (geology)

MAN-MADE/ARTIFICIAL RADIATION

(60-65 mRem)

Diagnostic/medical x-ray

(39 mRem)

Nuclear medicine/Radiation therapy

14 mRem)

Consumer product

(10 mRem)

Industrial source/powerplant

(2 mREm

COHERENT SCATTERING

●      Also known as RAYLEIGH/CLASSICAL/THOMPSON SCATTERING

●      The target atom immediately releases this excess energy as a scattered x-ray with wavelength equal to that of the incident x-ray, therefore; equal energy.

●      First described by J.J. THOMPSON.

●      X-ray loses no energy but slightly changes direction.

●      Produces scatter as a result of vibration of orbital electrons.

●      There is no energy transfer, therefore; no ionization.

●      Slightly contributes in film fog but little importance in diagnostic imaging.

●      Occurs at BELOW 10 keV X-RAYS.

●      PRODUCT: HEAT

COMPTON EFFECT/SCATTERING

●      Incident X-ray interacts with the loosely bound outer-shell electrons and ejects it from its orbit.

●      Causes ionization

●      Discovered by ARTHUR HOLLY COMPTON in 1923.

●      Produces scatter radiation that exits the patient and produces fog in the radiograph.

●      Results in occupational exposure for a radiographer.

●      Compton effect reduces contrast in x-ray images.

●      PRODUCT: SCATTERED RADIATION

●      Occurs at ABOVE 26 keV X-RAYS.

PHOTOELECTRIC EFFECT

●      Incident X-ray interacts with the inner shell electron.

●      Total absorption of X-ray photons.

●      Discovered by HEINRICH HERTZ in 1887 but ALBERT EINSTEIN provided a theoretical explanation using the CONCEPT OF PHOTONS.

●      PHOTON-TISSUE interactions primarily involves K-SHELL ELECTRONS.

●      Responsible for producing contrast on the radiograph.

●      Useful in diagnostic imaging.

●      PRODUCT: PHOTOELECTRONS

●      At BELOW 50 keV, PHOTOELECTRIC effect plays an important role in imaging soft tissue.

PAIR PRODUCTION

●      Occurs at energies of incident photons exceed greater than or equal to 1.02 MeV.

●      Interacts with the electric field of the nucleus of the target atom.

●      Interaction between photons and nuclear electrostatic force field causes the photon to disappear.

●      Photon’s energy is transformed into electron-positron pair.

 

PHOTODISINTEGRATION

●      High energy x-ray photons, those with energies ABOVE 10 MeV.

●      Interacts and absorbed directly to the excited nucleus of the target atom.

●      PRODUCT: NUCLEONS AND NUCLEAR FRAGMENTS.

●      Discovered by JAMES CHADWICK and MAURICE GOLDHABER in 1934.

●      Mostly observed in megavoltage therapy and high energy accelerator physics.