production of X rays pt 2

Question 1

mA (milliamperage):
controls

Answer 1

heating of the
filament

Question 2

Exposure time: controls

Answer 2

the
time in which x-rays are
produced

Question 3

kV (kilovoltage): controls

Answer 3

the acceleration of
electrons from cathode to
anode

Question 4

Electricity:

Answer 4

Flow of electrons through an electrical conductor.

Question 5

Current:

Answer 5

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

Question 6

Circuit:

Answer 6

Path of electrical current

Question 7

Voltage (Potential difference) :

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

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

Question 10

USA: – cycles per second

Answer 10

60

Question 11

Full wave rectification (4)

Answer 11

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.

Question 12

Constant potential and direct current
(4)

Answer 12

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

Question 13

How are x-ray produced?

Answer 13

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)

Question 14

1.Bremsstrahlung radiation
(3)

Answer 14

◦ 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.

Question 15

2. Characteristic radiation
   (3)

Answer 15

◦ 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.

Question 16

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

Answer 16

High-velocity

Question 17

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

Answer 17

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

Question 18

Bremsstrahlung radiation
equation

Answer 18

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

Question 19

Bremsstrahlung radiation increases
with (2)

Answer 19

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

Question 20

Bremsstrahlung radiation
steps (2)

Answer 20

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.

Question 21

Bremsstrahlung radiation
This type of radiation has a wide distribution
of

Answer 21

wavelengths (heterogeneous).

Question 22

Bremsstrahlung radiation
Electrons lose their energies in

Answer 22

random
fashion when they interact with tungsten
atoms.

Question 23

Bremsstrahlung radiation
Multiple interactions between (2)

Answer 23

electrons and
tungsten atoms.

Question 24

Summary of Bremsstrahlung (3)

Answer 24

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)

Question 25

Characteristic Radiation
steps (4)

Answer 25

. 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

Question 26

Characteristic Radiation
K=69,500
L=12,100
M=2,800
L to K transition →
M to K transition →

Answer 26

69,500 – 12,100 ev = 57,400 ev
69,500 – 2,800 ev = 66,700 ev

Question 27

Summary of Characteristic Radiation
◦ —% of diagnostic x-ray beam is characteristic radiation

Answer 27

30

Question 28

Summary of Characteristic Radiation
Electron strikes and ejects an inner shell electron of a tungsten
atom.
◦ This creates a

Answer 28

hole or vacancy in the atom that makes it
unstable.

Question 29

Summary of Characteristic Radiation
The atom responds by

Answer 29

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.

Question 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.

Answer 30

newly formed
radiation

Question 31

Bremsstrahlung radiation makes up the majority of the

Answer 31

x-ray beam and produces a heterogeneous
beam of varying photon energies.

Question 32

Characteristic radiation is only a minor source of radiation from the

Answer 32

x-ray tube and produces photon
energies specific for the target material.