production of X rays pt 2 Flashcards

1
Q

mA (milliamperage):
controls

A

heating of the
filament

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2
Q

Exposure time: controls

A

the
time in which x-rays are
produced

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3
Q

kV (kilovoltage): controls

A

the acceleration of
electrons from cathode to
anode

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4
Q

Electricity:

A

Flow of electrons through an electrical conductor.

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5
Q

Current:

A

Amount of electrons flowing through a conductor per second. Measured in amperes (A).

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6
Q

Circuit:

A

Path of electrical current

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7
Q

Voltage (Potential difference) :

A

Difference in electrical potential energy between two points in an
electric circuit. Measured in volts (V).

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8
Q

During each half-cycle (1/120 of a second),

A

anode is positive and attracts the electrons from
the cathode (x-radiation is produced).

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9
Q

During each alternate half-cycle (1/120 of a second),

A

anode is negative, therefore, no
attraction for electrons exists and no x-radiation is produced (inverse voltage).

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10
Q

USA: – cycles per second

A

60

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11
Q

Full wave rectification (4)

A
  1. Changing alternating current into
    direct current
  2. Full-waive rectification, high frequency
    power supply
  3. Essentially constant potential between
    cathode and anode.
  4. Higher mean energy of beam
    compared to AC.
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12
Q

Constant potential and direct current
(4)

A
  1. Shorter exposure times
  2. More consistent beam intensity
  3. Higher mean energy of beam
  4. Decreased radiation dose
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13
Q

How are x-ray produced?

A

X-rays are produced whenever
high-speed electrons are
suddenly decelerated or
brought to a stop when they
pass close to the nuclei of a high
Z # absorbing material (in this
case tungsten 74W)

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14
Q

1.Bremsstrahlung radiation
(3)

A

◦ AKA Breaking radiation
◦ Electron to nucleus interaction
◦ The fast-moving electrons either slow down
or stop when they come close to the nucleus
of the atoms and part of their energy is
transferred as X-rays.

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15
Q
  1. Characteristic radiation
    (3)
A

◦ Electron to electron interaction
◦ A few electrons interact with tungsten target orbital
electrons, imparting enough energy to ionize the
tungsten target.
◦ When electrons displace inner shell electrons,
characteristic radiation is produced.

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16
Q

Bremsstrahlung radiation
 —- electrons directed
toward the target material.

A

High-velocity

17
Q

Bremsstrahlung radiation
All electrons do not attain the same
velocity. Some move at

A

higher
velocity(ies) than others (depending
on kV)

18
Q

Bremsstrahlung radiation
equation

A

KE = ½ mV^2. The higher the velocity,
the greater the KE of electrons.

19
Q

Bremsstrahlung radiation increases
with (2)

A

increasing the voltage (kV) and
the atomic number of the target ( Z#)

20
Q

Bremsstrahlung radiation
steps (2)

A
  1. Impinging electron is deflected
    and decelerated. Kinetic energy
    lost is emitted as an x-ray photon.
  2. Head-on collision with nucleus:
    Electron brought to rest producing
    a maximum energy photon.
21
Q

Bremsstrahlung radiation
This type of radiation has a wide distribution
of

A

wavelengths (heterogeneous).

22
Q

Bremsstrahlung radiation
Electrons lose their energies in

A

random
fashion when they interact with tungsten
atoms.

23
Q

Bremsstrahlung radiation
Multiple interactions between (2)

A

electrons and
tungsten atoms.

24
Q

Summary of Bremsstrahlung (3)

A

Electrons (with different
Velocities) are
accelerated towards the
anode under the
influence of high
kilovoltage.
At the anode they either
interact with the nucleus
or rapidly decelerate and
get deflected (change of
direction).
The process results in
the release of
energy in the form of
x-ray photons (eV)

25
Characteristic Radiation steps (4)
. Arises when cathode electron collides with inner orbital electron of tungsten atom (target) and removes it from orbit. 2. Atom is now ionized and unstable. 3. Immediately, the hole left by the electron is filled by an electron from an outer shell, and energy is emitted from this electron in the form of x- radiation characteristic of tungsten and the involved shell. 4. The energy emitted by the electron is equivalent to the difference in the binding energies of the two shells/orbitals
26
Characteristic Radiation K=69,500 L=12,100 M=2,800 L to K transition → M to K transition →
69,500 – 12,100 ev = 57,400 ev 69,500 – 2,800 ev = 66,700 ev
27
Summary of Characteristic Radiation ◦ ---% of diagnostic x-ray beam is characteristic radiation
30
28
Summary of Characteristic Radiation Electron strikes and ejects an inner shell electron of a tungsten atom. ◦ This creates a
hole or vacancy in the atom that makes it unstable.
29
Summary of Characteristic Radiation The atom responds by
shifting electrons inward to fill the vacancy. Whenever an outer shell electron is shifted inward it must give up some of its energy in the form of radiation called a characteristic photon.
30
Summary of Characteristic Radiation In this manner discrete energy is imparted to the --- which is "characteristic" of the atom type and orbital from which it came, thus the name characteristic radiation.
newly formed radiation
31
Bremsstrahlung radiation makes up the majority of the
x-ray beam and produces a heterogeneous beam of varying photon energies.
32
Characteristic radiation is only a minor source of radiation from the
x-ray tube and produces photon energies specific for the target material.