6. X-ray Production Flashcards
(148 cards)
1
Q
During the 1870s and 1880s, many university physics laboratories were investigating the
conduction of cathode rays through a large, partially evacuated glass tube known as a
A
Crookes tube
2
Q
was the forerunner of
modern fluorescent lamps and x-ray tubes
A
Crookes tube
3
Q
was experimenting with a type of Crookes tube when he discovered x-rays
A
Wilhelm Conrad Roentgen
4
Q
The date x-rays were discovered
A
November 8, 1895
5
Q
On November 8, 1895, Roentgen was working in his physics laboratory at
A
Würzburg University in Germany
6
Q
He had darkened his laboratory and completely enclosed his Crookes tube with black photographic paper so he could better visualize the effects of the cathode rays in the tube. A plate coated with ________, a
fluorescent material, happened to be lying on a bench
top several meters from the Crookes tube.
A
Barium Platinocyanide
7
Q
No visible light escaped from the Crookes tube
because of the black paper that enclosed it, but Roentgen noted that the barium platinocyanide glowed. This glow is called
A
fluorescence
8
Q
First Clinical Application of x-rays was conducted at
A
Dartmouth College in February 1896
9
Q
X-rays are also called
A
Roentgen rays
10
Q
Roentgen was able to capture a radiograph
of the hand of his wife:
A
Anna Bertha Ludwig
11
Q
was primarily used to study the nature of electrons
A
Crookes tube
12
Q
Crookes tube was primarily used to study
the nature of electrons. In contrast, X-ray
tube now is primarily for _____
A
Xray production
13
Q
By making sure that electrons are directed
to one direction only (cathode to anode),
Quality of x-rays is ___ quality and generation of x-rays is _____. Unlike in
Crookes tube.
A
high,
efficient
14
Q
is the source of electrons
A
Cathode
15
Q
the target, where electrons are bombarded
A
Anode
16
Q
is composed of Tungsten
A
Anode
17
Q
When electrons hit anode, tungsten is said
to be _____, creating electrons that will used to penetrate patients
A
ionized
18
Q
come from the electrons outside nucleus
A
X-rays
19
Q
come from the nucleus
A
Gamma rays
20
Q
is what encloses the internal components
A
Pyrex glass
21
Q
This kind of glass is able to withstand tremendous amount of heat during
the process of x-ray production
A
Pyrex glass
22
Q
not all x-rays (1% ) are useful, some are
______ x-rays that only add radiation
dose of patient
A
low energy
23
Q
is the area of the glass or metal enclosure, approximately 5 cm^2, that is thin and through which the useful beam
of x-rays is emitted
A
X-ray tube window
24
Q
thinnest part of the x-ray tube glass
A
X-ray tube window
25
it is thin so that it will not decrease the
| energy of the x-rays that will pass through it
X-ray tube window
26
Other parts of the glass is ____, nonetheless
thick
27
is not immediately visible
| because it is contained within the protective housing which is made up of lead
X-ray tube
28
has a hole where x-rays
| could escape
Protective housing
29
Inside the x-ray tube is a ______ no air; this
is important so that no molecules/air will
interfere with the flow of electrons from cathode to anode
vacuum
30
Within the protective housing and x-ray
| tube, there is ___ for insulation
Oil
31
will help to remove away heat during x-ray
| production
Oil
32
One that holds target anode is
rotor
33
Heat from the target will be conducted
| away by the
rotor
34
Oil will then transfer heat to the protective
| housing through
convection
35
Protective housing will then release heat in
| the form of
infrared radiation= environment radiation
36
X-rays emitted through the window is called the
useful beam
37
X-rays that escaped through the tube housing are called
Leakage radiation
38
Leakage radiation should not exceed _____ at 1 m when operated at maximum condition
100 mR/hr
39
The protective housing around some x-ray tubes contains oil that serves as both an _____ against electric shock and _____ to dissipate heat
insulator,
| thermal cushion
40
Xrays that don’t pass through the x-ray tube
| window is called
Leakage radiation
41
Direction of x-rays is
divergent
42
X rays goes to all directions from point source. Thus _____
leakage radiation
43
absorb low energy x-rays. Usually made up of aluminum that has an atomic number of 13
Filters
44
enables one to see the field of exposure
Collimator
45
is the negative side of the x-ray tube
Cathode
46
Cathode has 2 primary parts
filament and focusing cup
47
must be pressed to start
| rotation of rotor
rotor button
48
while rotor is rotating, ______
(tungsten) will be heated until it boils off
electrons
cathode filament
49
boiling of electrons
Thermionic emission
50
accumulation of electrons
| after thermionic emission
Space charge
51
Space charge also called
electron cloud
52
light indicator will turn
on if it is ready for exposure (if boiling off of
electrons is sufficient already)
Exposure button
53
Once exposure button is pushed, _____ will be administered that will push electrons to the anode
voltage
54
If x-ray/exposure button is pushed without pushing the ______ first there will be no exposure that will occur
rotor button
55
must be pushed first so that electrons will be accumulated at the right
amount
Rotor button
56
determine amount of electrons.
| However, rough estimate only
mAs
57
are enclosed in a focusing cup
Filaments
58
focuses electrons so that
| electron will not scatter
Focusing cup
59
is negatively charged to repel electrons, otherwise, it will attract
electrons if it is positive making it difficult to
bombard electrons to the anode
Focusing cup
60
area in the anode where
| electrons will hit. Part of tungsten target
Focal spot
61
is held by rotor
Target
62
Filament is usually approximately __ in diameter and ___ long
2 mm,
| 1 or 2 cm
63
2 types of filaments
small and large
64
Filaments are usually made of
thoriated tungsten
65
Tungsten have high melting point of
3410 degrees Celsius
66
Does not vaporize easily
Filament (Tungsten)
67
Addition of 1% to 2% thorium to tungsten increases the efficiency of
thermionic emission
68
Filaments are not purely tungsten. They are
| alloyed with
thorium
69
Majority of filament is still made of
tungsten
70
When the current through the filament is sufficiently high, the outer-shell electrons of the filament atoms are
“boiled off” and ejected from the filament
Thermionic emission
71
Focuses the electrons towards the target
Focusing Cup
72
a concept in which excess electric charge is treated as a continuum of charge distributed over a
region of space (either a volume or an area) rather than distinct point-like charges
Space charge
73
is the positive side of the x-ray tube
Anode
74
Functions of anode assembly
- Electrical conductor
- Mechanical support
- Thermal dissipator
75
Process of releasing of charged particles through the use of heat.
Thermionic emission
76
Where the filaments are embedded
Focusing Cup
77
Negatively charged focusing cup > _____
| electrons
repel
78
it conducts electricity and radiates heat and contains the target
Anode
79
has a different texture since it has been hit frequently by electrons coming from the cathode and there is pitting
Focal Spot
80
conduct the electricity that is needed to operate the xray tube
Electrical conductor
81
rotor holds the target
| in place
Mechanical support
82
rotor (made up of
copper which is a good heat conductor)
conducts the heat away from the target
Thermal dissipator
83
Area of the anode struck by the electrons from the cathode
Target
84
Is the actual x-ray source
Focal Spot
85
Specific area in the target that is struck by electrons
Focal Spot
86
is used when better spatial resolution is required. Ranges from 0.1 to 1 mm
Small focal spot
87
is used when large body parts are imaged and when other techniques that produce high are
required
Large focal spot
88
The _____ the focal spot, the more it is
easier to heat up and increase mas and
produce more electrons. However, more prone to breakage.
smaller
89
has high heat capacity and less prone to breakage
Large focal spot
90
Are used in dental x-ray imaging systems, some portable imaging systems, and other purpose units in which high tube current and power are not required
Stationary anode
91
Capable of producing high intensity x-ray beam
Rotating anode
92
Rotating anode rotates to
3400 rpm and 10,000 rpm
93
Heat capacity can be further improved by ______ the speed of anode rotation
increasing
94
the target is consists of tungsten alloy embedded in a copper anode
Stationary anode tubes
95
the entire rotating disc is the target
Rotating anode tubes
96
Stationary anode tubes size
About 4 mm^2
97
Rotating anode tubes size
About 3159 mm^2
98
heat is distributed
| across different areas
Rotating anode
99
is powered by an electromagnetic induction motor
Rotating anode
100
is consist of 2 parts: the stator and the rotor
Induction motor
101
fixed electromagnet. Become magnetized once they are administered
with electricity
Stator
102
is surrounded by stator
Rotor
103
is wrapped around Ferromagnetic material. Will be attracted once stator is given electricity
Copper
104
Tungsten is the material of choice for the target for general radiography for 3 main reasons:
- Atomic number
- Thermal conductivity
- High melting point
105
Tungsten atomic number
74
106
K shell Electron Binding Energy is high about
69.5 keV
107
Does not store heat for a long term.
Conduct heat easily. We don’t want heat to
accumulate in the target so that it won’t
crack
Tungsten
108
Specialty x-ray tubes for mammography have ___________ targets principally because of their low atomic number and low K characteristics x-ray energy
Molybdenum or Rhodium
109
Alloying ________ gives it added mechanical strength to withstand the stresses of high
speed rotation
Tungsten (usually with rhenium )
110
have lower mass density than tungsten, thus allowing the target easier to rotate
Molybedum and graphite
111
Molybdenum atomic number
42
112
Rhodium atomic number
45
113
Molybdenum k-shell electron binding energy:
19 keV
114
Rhodium k-shell electron binding energy:
23 keV
115
____ energy is required for breasts because
the breast is a soft tissue. If ____ energy will
be used, all will penetrate through the
breast resulting to a dark radiograph
Low,
| high
116
is needed
| to visualize the soft tissues.
Differential absorption of x-rays
117
Results in an effective focal spot size much less than the actual focal spot size
Line-Focus Principle
118
Line-Focus Principle is also known as
Goetze Principle
119
Diagnostic x-ray tubes have target angles that vary from approximately ______ degrees
5 to 20
120
allows high anode heating with small effective focal spots. As the target decreases, so does the focal spot size
Line-Focus Principle
121
Radiation intensity is greater on the cathode side of the x-ray field than that on the anode side.
Anode Heel Effect
122
is made possible with
| the angulation of the target
Line-Focus Principle
123
The bigger the anode angulation the ____ the
| effective focal spot size
larger
124
Intensity of xrays is greater on the _____
| side (Anode Heel Effect)
cathode (Fat Cat)
125
In greater anode angulations, changes in
intensity from cathode to anode is _____
and not abrupt, unlike in smaller anode angle that has abrupt changes
gradual
126
To correct heel effect, ______ are used
wedge filters
127
If wedge filters are not available, thicker
parts must be placed near the _____ side
and less thicker parts on the ____ side.
cathode (thicker),
| anode (thinner)
128
Electrons bounce off the focal spot and then land on other areas of the target, causing x-rays to be produced
from outside of the focal spot
Off Focus Radiation
129
is the energy of motion
Kinetic Energy
130
Electrons travelling from cathode to anode
Projectile Electrons
131
interacts with orbital electron of the target atom
Projectile Electrons
132
Projectile electron interacts with orbital electron of the target atom. This interaction results in the conversion of electron kinetic energy into ______ and electromagnetic energy in the form of ______
KE- thermal energy (heat),
| EME- infrared radiation (also heat) and x-ray
133
Approximately ____ of kinetic energy of projectile electrons is converted to heat
99%
134
Only approximately ___ of projectile electrons is converted to x-ray
1%
135
X-rays produced
| outside of the focal spot
Off Focus Radiation
136
electrons ejected from
| the outer shell
Compton electron
137
In 1% , ___ is characteristic radiation but
| only those with 69 kev where k shell electron vacancy is filled is useful
15%
138
characteristic radiation
from them usually do not penetrate patient
and reach IR
LMNOP shells
139
The slowing of nucleus and loss of kinetic energy produces
X-rays
140
The efficiency of x-ray production is independent of the tube current.
o At 60 kVp, ___ conversion
o At 100 kVp, ___ conversion
o At 20 MV, ___ conversion
0.5%,
1%,
70%
141
are emitted when an outer-shell electron fills an inner-shell void
Characteristic x-rays
142
At 100 kVp, approximately ____ of the x-ray beam is characteristic
15%
143
Are produced when a projectile electron is slowed by the electric field of a target atom nucleus
Bremsstrahlung Radiation
144
“Slowed down radiation”
Bremsstrahlung Radiation
145
German word which means “braking radiation” or “deceleration radiation”
Bremsstrahlung Radiation
146
to brake
bremsen
147
radiation
Strahlung
148
In characteristic radiation, About _____ are Bremsstrahlung. But
large portion of bremsstrahlung radiation
produced is not useful
75- 85%
