Ch6 LET and RBE Flashcards
Electromagnetic waves can break ___
Chemical bonds
What is particulate radiation
Emission of energized particles from the nucleus during radio active decay
What is excitation
Raising of a electron WITHOUT the ejection of an orbital electron
What is Ionization
Removal of an electron resulting in a ion pair
In ionization what charge is the newly freed electron
Negative
What energy does modern equipment use (Mv)
4-25 MV energy
Ionizatioan results in the ___ ___ of a radiation beam
biological effictiveness
Electromagnetic and particulate both (2)
- Propel energy through space
- Travel at the speed of light
Electromagnetic particles consists of
Photons
Electromagnetic have a ___ penetrability
Higher
Electromagnetic examples (3)
- Radiowaves
- Microwaves
- Infrared
Photons have no (2)
- Mass
- Charge
Particulate particles can be
can be charged or uncharged
Particulate have a ___ penetrability
Lower
Examples of Particulate particles (2)
- Alpha particles
- Beat particles
What does LET measure?
The rate at which energy is transformed from souce to tissue
Densely ionizing has ___ LET
High
Sparsely ionizing has ___ LET
Low
Examples of densely ionizing particles
Alpha particles and neutrons
Examples of low LET rays
- Xray
- Gamma ray
LET Alpha particle
- Charge
- AMN
- LET
- 2
- 4
- Highest
LET Neutron
- Charge
- AMN
- LET
- 0
- 1
- High
Direct interatction is more likely with ___ LET radaition
High
What is the principle interaction in the body
Radiolysis of water
Alpha particles consists of
2 protons and 2 neutrons
LET Proton
- Charge
- AMN
- LET
- 1
- 1
- High
Alpha particles are emmitted during the
Decay of radionuclides
Direct interactions provide kinetic energy that can (2)
- Disrupt the atomic structure
- Produce biological change
Direct interactions results from
Ionization or excitation of the target
Examples of high LET particles (3)
- Protons
- Electrons
- Neutrons
Direct action produces damage by
Direct ionization of the critical target
X-rays and gamma rays produce ___ ionization
Indirect
X-rays and gamma rays do not produce ___ and ___ damage
themselves
- Chemical
- Biological
Ionization of water and the formation of __ and __ ion pair. AND the formation of __/__ free radicals are extremely reactive
- H+ and OH-
- OH/H
The major factor of damage is the ___, Via ___
OH radical via indirect action
in the cell**.
Does indirect action or direct action have a greater probability of radiation damage?
Why?
- Indirect action
- there is more water in the body than any other components. body is 80% water & chances of spreading is more.
what does LET stand for?
linear energy transfer
Indirect interactions primarily occure through ionization of ___
water
Indirect interactions produce
Free radicals
Define Ion
Atom or molecule that is electrically charged because it has lost an electron
Define free radical
Fragment of an atom or molecule that has a unpaired electron in the outer shell making it highly reactive
Define LET
Rate at energy is deposited, as a charged particle travels through matter, by a particular type of radiation
LET is dependant on (2)
- Mass
- Charge
Relative biologic effect is based on
differing rates of energy loss
Equal ___ of radiation differing in LET, produces ___ ___ of the same ___ ___
- Doses
- Varying degree
- Biologic responce
What is “Relative” Biological Effect
The ability of different types of radiation to produce the same biological responce
RBE= the comparison of a dose of __ ___ to the
dose of ___ kev x-ray that produces the ___ ___
response
- Test radiation
- 250
- Same biologic
Different “doses” of differing LET radiation will produce the
SAME DEGREE of a biologic effect.
different LET type radiation will produce the same
degree of biologic effect but
at different doses
RBE formula
(Dose) of 250 Kev / (Dose) of test radiation
Standard formula
(Dose) of 250 Kev / 1.0
RBE geater than 1.0 indicates
Higher LET
RBE
- 1.0
- 1.5
- 2.0
- Same effect
-50% higher RBT - 100% higher RBT (Double effect)
