Chapter 8 X Ray Production Flashcards by Melissa Unknown

X-rays versus gamma rays

-X-rays are man made process
-originate from electron cloud of atoms
-gamma rays are a natural process
-originate from atomic nucleus through radioactive decay

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Velocity of accelerate electrons

Speed of light

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Increase kinetic energy of incident electrons also increases :

-quality and quantity
- number of target interactions

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The three target interactions are

heat production
-Bremsstrahlung
-characteristic

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-high atomic number
-high melting points
-similar binding electrons

Tungsten and rhenium

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Molybdenum
-lower atomic number
-ideal for soft tissues of breast

Mammography

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Bremsstrahlung is the German term for :

“Breaking or slowing radiation”

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Bremsstrahlung is responsible for how much percentage of the X-rays produced in the X-ray tube

85%

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Incident electron interacts with electrostatic force field of nucleus (nucleus of tungsten)

Bremsstrahlung

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The closer the incident electron passes to the nucleus

The higher energy of the photon

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Further away to the nucleus

The lower energy of the photon

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A Brem photon is the result of

The energy difference between the incident electron as it passes (slows) near the nucleus

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Brem radiation involves

An incident electron and the nucleus of an atom

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The inner shell of an atom

K shell

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Brem radiation is produced

By the slowing of an incident electron

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Incoming electrons =

Incident electrons

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Brems responsible for wide variety of energies

-produces a continuous spectrum of X-rays
-heterogenous X-ray beam

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Brems process at atomic level :

-high speed electron is attracted to the positively charged nucleus
- interaction with nuclear force fields causes electron to slow down and lose energy
-lost kinetic energy converted to X-ray energy

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Brems energy produced dependent on

-how close to the incident photon gets to the nucleus (closer creates increased energy)
- the degree of deceleration of the electron (greater deceleration created increased energy)

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Increased wavelength and decreased frequency =

Decreased energy

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Decreased wavelength and increased frequency =

Increased energy

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Results of Brems :

-deceleration yields X-ray photon energies
-X-ray production is continuous during deceleration
-accounts for largest portion of total X-ray beam
-photon energy dependent on how close electron comes to nucleus and rate of deceleration

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Two interactions part of X-ray production

Bremmstruhlung interactions and characteristic interactions

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As incident electron gets closer to nucleus, the following occurs,

-photon energy increases due to rate of deceleration
- larger deflection of incident electron
-electrons with small amount of residual kinetic energy, become part of electrical current flow

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Less of a turn=

Less energy of a photon

True or false Electron interacts directly with nucleus

False : slim chance an electron will hit or interact with nucleus directly and if that happens all energy will be lost

Characteristic X-ray production involves

Incident electron and inner shell electron

The process of adding or removing electrons from an atom is

Ionization

Responsible for 15% of X-rays produced in the X-ray tube

Characteristic

Cherecteristics responsoble for specific level of energies :

Produces a discrete level of energies

Characteristic process at atomic level

-high speed incident electron interacts with an inner shell (k or l) shell electron or a target atom -k or l shell electron is ejected , leaving a vacancy -electron vacancy filled by another electron from an outer shell (characteristic cascade) -electron transition responsible for producing a characteristic X-ray photon

Binding energy of kshell is

69.5

Characteristic can be produced at what amount of keV

70 or higher

What kind of energy spectrum does Brem produce

Continuous

Characteristic cascade

The process of an outer shell electron filling a vacancy left in an inner shell

-hole in inner shell and must be filled by electron from any outer shell - electron energy difference -secondary photon produced

Characteristic cascade

What shell is of diagnostic value

K shell

Brems is produced at what keV

Anything less than 70

Changing (blank) will change the maximum energy of the photons in the X-ray emission spectrum

KVp

The cascade process is associated with:

Characteristic radiation production

A technologist can control the quantity of the X-rays striking the patient by adjusting the

The maximum kinetic energy of a projectile electron accelerated across an X-ray tube depends on the

Kilovoltage

Beam quantity if primarily determined by

mAs

What can be determined from an X-ray emission spectrum

Maximum photon energy and average photon energy

Characteristic radiation is produced when:

A vacancy in an electron orbit is filled

X-ray tube filtration filters out

Low energy X-rays

When an incident electron approaches a positive charged nucleus of a tungsten atom

The incident electron slows down due to electrostatic attraction

Controls the projectile electron energy , intensity, maximum energy and the average energy of the X-ray beam

kVp

Controls the number of projectile electrons striking the anode and the intensity of the X-ray beam

-Brems and characteristic emissions combined - consists of “Brems hump” and characteristic peak -selected KVp will determine maximum keV for any photon

Emission spectrum

Less than 70 KVp is what % is Brems

100%

90 KVp average energy what is your keV

30 keV

Approximately 30-40% of selected KVp

Average keV

Higher KVp =

Higher average energy

KVp is your …

Energy (quality)

mA is your

Quantity

Changes in mA and KVp

Characteristic peak energy levels remain unchanged

Change in KVp

-changes beam amplitude and average energy

Change in generator type

Produce a beam with higher average energy

Characteristic energy produced dependent on

- binding energy of the k shell -binding energy of a k shell tungsten atom is 69.5 keV

Value of the photon energy equals to :

The difference of the binding energy of the ionized shell and the transitioning electron

Penetrating ability of the X-ray beam

X-ray beam quality

Amount of material required to reduce the X-ray beam intensity to one half its original value

Half value layer

Factors which affect beam quality

-KVp -filtration

Changes the beam quality by changing photon wavelength and an increase causes both the average and maximum energy to increase

Kvp

Graph which plots the number of X-rays produced as a function of their energies

X-ray spectrum

Amount or number of X-ray photons in the X-ray beam

X-ray beam quantity

Information that can be obtained from the graph

-continuous curve =Brems -individual spikes=characteristic -Maximum beam energy -average bean energy

Factors which affect beam quality and quantity

KVp, mA , time, filtration, X-ray circuit waveform

-Changes the beam quality -causes both the average and maximum energy to increase

Kvp

-changes the beam quantity -causes the total number of X-rays to increase or decrease

Changes the beam quantity causes the total of number of photons to increase Proportional relationship

time

Brems interaction in order :

1. High speed incident electron comes close to the nucleus of a tungsten atom 2. Positive nuclear force field causes the incident electron to change direction 3. The high speed electron decelerates 4. The lost kinetic energy is converted to an X-ray photon

Characteristic intersection in order :

1. High speed projectile electron passes near a K or L shell electron or a tungsten atom 2. The incident electron ejects the inner shell electron 3. A vacancy is created in the orbital shell 4. The unstable atom attempts to return to the normal state by filling the vacancy with the outer shell electrons 5. The movement of outer shell electrons creates a characteristic cascade 6. The potential energy of each orbital electrons movement is converted to a characteristic photon

Energy or motion, type of energy exhibited by incident electrons

Kinetic