Download Radiographers

Basic X-ray Physics for
Radiographers
By Teacher:
Nourah M. Al-Ruwais
Chapter #1
MATTER AND ENERGY
Matter: It is the material of which all things
including ourselves are made.
 It has a mass, size and occupies space.
 Matter is made of molecules. Molecules are
made of atoms. Atoms are made of electrons (ve) and nucleus (proton +ve and neutron).
 Atom is the unit of matter.
 Matter is of three physical states:
Solid- liquid- gas.
Basic Uni ts/ Fundament al units:
MKS



SYSTEM;
Mass
Length
Time
K= kilograms
m= meter
s= Seconds
Velocity (speed): The distance that has been
crossed in a period of time.
Velocity = distance/ time
m/s
Stationary= no motion.
Acceleration: The rate of change in velocity.
A= Velocity/ time
m/sec
Force: The tendency to cause motion. Or to move
a stationary object.
F= mxa
(m=mass, a=acceleration)
Newton = Kg.m/s
Work: It is the magnitude of force that makes a
body move to a distance.
W=Fxd
(d=distance, F=force)
Joule= Newton.m
Power: It is the rate of doing work.
P= work/time
= Fxd/t
Watt= joule/sec.
Law of co nservation of Matter or E nergy:
(Matter/Energy) cannot be created nor destroyed
but can only be changed from one form to another.
Energy: It is the ability to do work.
(Joule)
Forms of Energy: Electrical E.- Heat E. – Light
E. – Atomic E. – Sound E. – Mechanical
E.(Potential or Kinetic).
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CHA PTER #2
Heat
It is a form of energy.
It is the average vibration energy of the
molecules.
Heat  motion  Kinetic Energy
States of matter:
Solid: Kinetic Energy of the molecules  heat.
Ex: ice
Liquid & Gases: Particles move fast kinetic
energy  heat.
Ex: water & steam.
Temperature: It is the indication of the degree
of hotness or coldness.
It also represents the average speed of the
particles.
 temp. solids melt & liquid changes into
gas
(Substance expands).
 temp. liquid becomes solid & gas becomes
liquid. (Substance contracts).
How is temperature measured?
By a Thermometer.
It ranges between the melting point of ice and
the boiling point of water.
Thermometers are of three types:
 Centigrade 0c – 100c .
 Fahrenheit 32F - 212F .
 Kelvin
273K - 373K .
Normal body temperature: 37c - 96F - 310K.
Units of Heat: Joule and calorie.
Calorie:The amount of heat required to raise the
temperature of 1gm of H2O to 1c .
1 calorie = 4.2 Joules
Specific Heat: The amount of heat required to
raise the temperature of 1gram of a substance to
1c.
The specific heat of H2O = 1.
3
Heat Capacity: It
which is required
by 1K.
is
to
the heat energy
raise the temp.
in
of
joules,
the body
Heat law: Heat gained by one body must be equal
to heat lost by another body.
Heat transmission in matter:
 Conduction: In solids (metal “good”- wood
“bad”).
 Convection: In liquid and gases.
 Radiation: In vacuum.
Radiation: It is the flow of heat in a vacuum.
It is the method by which energy reaches us from
the sun.
C HAPTER #3
Elec tricity
It is an electrical energy, which is transported
from one location to another by electrons.
Types of electricity:
Static Electricity
Current Electricity
“Electrostatics”
o The charge is
The charge is moving in
stationary
a conductor due to
o Production of
difference in potential
charge by friction
across its two ends.
o Ex: clothes, hands,
battery..
Charge: When two bodies are rubbed together there
is transference of electrons from one body to
another.
 The body that loses electrons will be +ve
positively charged.
 The body that gains electrons will be –ve
negatively charged.
Two types of charge: +ve
and
–ve.
How are they produced?
1. By friction.
2. By ionization of an atom.
What are the properties of charge?
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1. Like charge repel each other.
2. Unlike charge attract each other.
3. There is a force (F) of attraction or
repulsion between the two charges.
4. The charge cannot be created nor destroyed
Electrical field: It is the field around the
charge which can experience a force of attraction
or repulsion.
Columbs law of electrostatics:
 The force of attraction or repulsion (F) is
directly proportional to the product of the
charge (Q).
 And inversely proportional to the square of
the distance (d ).
 F= K. Q1 X Q
d
CHAPTER #4
Atomic S tructure
Elements: Chemical substances that cannot be
broken down into simpler chemical forms.
There are 108 chemical elements in nature.
Ex: Hydrogen, Carbon, Oxygen, Nitrogen…
Atoms: It is the smallest part of an element
which retain the chemical properties of the
element.
Bohr’s theory of Atoms:
An Atom has two parts
Nucleus (+ve)
Electrons (ve)
Protons
Neutrons
Move around the
nucleus
“+ve”
“neutral”
In a fixed orbit
or shell.
 Protons are equal and opposite to the
charge of an electron.
 Protons and neutrons have the same mass.
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 An electron is 2000 times lighter than a
proton.
 Electrons have kinetic energy.
The electron distribution in an Atom:
K=2e
L=8e
M=18e
N=32e
Atomic number: It is the number of protons in the
nucleus “Z”.
Determines the chemical properties of the atom.
Atomic mass: It is the total number of protons
and neutrons in the nucleus “A”.
Ex:
H
Z=1
A=1
C
Z=6
A=12
O
Z=8
A=16
Isotope: Atoms having the same atomic number “Z”
but different atomic mass “A”.
 All Isotopes have the same chemical
properties because they have the same number
of protons.
 Ex: I
, I
, I
, I
. Iodine
Isotopes.
Types of Isotopes:
 Radioactive Isotopes: they emit radiation.
Such as Alpha, beta and gamma rays.
 Non radioactive Isotopes: they do not emit
radiation.
Ionization: It is the process by which a pair of
ions are formed.
 When the force of attraction between the
electron and the nucleus of an atom is
balanced then the atom is neutral.
 When an electron is removed from a neutral
atom it becomes positively charged.
 Ionization is lost by heat, friction or by
radiation.
Binding Energy: It
remove an electron
Depends on:
is the energy required to
from the shell.
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1. The type of shell. Inner shell electrons
have higher binding energy than outer shell
electrons.
2. The atomic number “z” the number of protons
in the nucleus.
Z   binding energy.
Ionizing Radiation: It is the process of removing
an electron from an atom by exposing it to a
certain type of radiation.
Such as: x-ray, gamma ray, cosmic ray…
CH APTER# 5
Electrical Charge and Potential Energy
o When there are excessive electrons -ve
charge
o When there is deficiency of electrons+ve .
Charge.
o Unit of charge is Coulomb.
o 1coulomb= 6x10 e .
Electric Potential Energy: The amount of work
done in bringing a unit positive charge from
infinity to that point.
Potential difference: The potential difference
between 2points is the work done in moving a unit
positive charge from one point to another.
Work done= electrical charge x potential
difference
1coulomb x 100volt = 100Joule
o unit of potential difference is Volt.
o Volt= joule / coulmb
Electro volt (ev): It is the work done in moving
an electron when the potential difference is
1volt.
ev . Kev= 1000ev , Mev= 1000000ev.
1ev= 16x 10 joule
ex: light= 3.5ev,
x-ray= 20kev- 500kev,
gamma ray=100kev- 2Mev.
Earth Potential: It is the baseline from which an
electric potential is measured.
o Earths potential is constant.
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o
o
o
Earth potential equals zero.
Electrons travel from high to
Any leakage of charge will go
earth because earth has lower
low potential.
immediately to
potential.
CHAPTER#6
Capacity
Movement of charge in a material:
1. Conductor: The movement of charge is fast
when potential difference is applied.
Ex: silver, iron, copper, aluminum.
 The electrons in the conductor are free.
2. Insulator: (bad conductor) the movement of
charge is minimum even if there is potential
difference.
Ex: wood, plastic, paper, glass, rubber…
 The electrons are tightly bonded. Not free.
3. Semiconductor: they allow flow of charge when
the potential difference is very high.
Ex: silicon, germanium…
Used in x-ray equipment.
4. Superconductor: substances, which offer no
resistance to the flow of current.
Capacitance: It is the storage ability of the
conductor at a fixed potential. Or how much
charge it can store.
Capacitance of conductor=storage of charge/
potential
Q=C.V
“C has constant capacity”
Q is directly proportional to the potential.
Unit of capacitance is “FARAD”.
FARAD= coulomb/ volt.
mF, F, nF, pF.
Capacitor: It is a device which stores charge.
Two types:
1. Spherical capacitor
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2. Parallel plate capacitors
Charging the capacitor: The time taken to charge
the capacitor.
Charge is added
in an
Exponential
rate.
“Exponential
growth”
Discharging the capacitor: Time taken to empty
the charge from the capacitor.
Charge is removed
from
The capacitor at
an
Exponential rate.
“exponential
decay”
Capacity symbol:
Law of capacitance in series: When the capacitors
are connected in series, the total capacity (c)
is increased.
c1
c2
c3
c4
C=c1+c+c3+c4…
Law of capacitance in parallel: When the
capacitors are connected in parallel, the total
capacity (c) is decreased.
C=1/c1+1/c+1/c3+1/c4…
Capacitors in Radiography:
1. Capacitor discharge in mobile units.
2. Electronic timer.
3. Voltage stabilizer.
4. Induction motor.
Symbols:
Mains
kev
Battery
Ammeter
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Voltammeter
Coil
Resistance
Variable resistance
Ohmmeter
Ohm
Transformer
Conductor
Earth
c hapter# 7
Elec tric current
What is a circuit? It is a simple wiring
diagram, where varies electrical components are
connected represented by there symbols.
Simple circuit
Current: It is the movement of an electrical
charge in a conductor.
Or, it is the flow of electrons from higher to
lower potential.
Current (I)= flow of charge (Q)/ time (t)
Ampere= coulomb/ sec.
6x10 electrons/1 sec.
charge (Q)= I X T.
Ex: How much charge is there if the current is
20mA, in 1sec.?
Coulomb= mAs
Resistance: (R) It is the opposition to the
flow of current in a conductor.
 When the current passes through the
resistance it loses its energy and is
converted into heat.
 The unit of resistance is ohm (
).
Ohms law: The current (I) flowing in the
conductor is directly proportional to the
potential difference (v) across the two ends
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while the temperature and pressure are
constant.
I  v
R=v/I
ohm(
)=volt/ampere
Ohm: If the current flowing in a conductor is
1A and the P.D. is 1v then the resistance of
the conductor is 1ohm.
What are the factors effecting resistance?
RL (length),
R1/a (area of cross
section)
R=k.L/a
(k=constant of a material, called
resistivity) resistivity is opposite to
conductivity.
What causes resistance?
The interaction of electrons with the electrons
in the conductor causing opposition in the
flow.
 Material which has large number of free
electrons has less resistance.
 More heat  more resistance.
Law of resistance in series:
When 2 or more resistances are connected in
series then the total resistances are equal to
the sum of individual resistances.
R= r1 + r2 + r3 + … R= 1+2+3+…
Law of resistance in parallel:
When 2 or more resistances are connected in
parallel then the reciprocal of the total
resistances is equal to the reciprocal of
individual resistances.
1/R= 1/r+1/r2+1/r3+… = 1/1+1/2+1/3+…
 Resistances connected in parallel is
always less than any of the individual
resistances.
Electromotive force (e.m.f): It is the force
that moves electrons in a conductor.
Electrical energy: It is the amount of work
done by electricity.
EE= P.D. X charge
EE= v x Q
(joule)
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Q= I x t ,
EE= v x I x t , joule= watt x
sec.
 If the current given in an x-ray tube is
2mA in 1sec and the P.D. is 100kv . then
calculate the electrical energy in the xray tube?
Electrical power: It is the rate of doing work
by electricity.
EP= EE/time
EP= vxIxt/t
EP= Ixv
Watt = ampere x volt
 Electrical energy is used in the
production of x-ray.
 In each chest x-ray, 100watt is required
of electrical power.
 Electricity is also required for heating
of the filament for thermion emission of
electros.
CH APTER# 8
Magne ts
Properties of magnets:
1. Always point in a north – south direction.
2. Has 2poles (north and south poles).
3. It attracts faro magnetic substances such as
iron, nickel, cobalt…
4. Like poles repel each other, unlike poles
attract each other.
5. There is a force of attraction or repultion
between two poles.
6. No separation between north and south poles.
7. Pole strength is always equal.
8. Magnetism is produced by magnetic induction
or by electrical current flowing in a coil.
9. The force of attraction or repulsion (f)
between 2poles is directly proportional to
the pole strength (m).
10. The force of attraction or repulsion(f)
between 2poles is inversely proportional to the
square of the distance (d ).
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11. F= 1/ m1 x m2 / d
= constant
 Any magnetic substance consists of
domains.
 In an unmagnetized material the domains
are bipolar.
 In a magnetized material the domains are
arranged. The north pole pointing in one
direction and the south pole pointing in
the opposite direction.
Types of magnets:
1. Bar magnet (permanent magnet)
2. Horse shoe magnet (permanent magnet)
3. Electromagnet (temporary magnet)
Horse shoe magnet is the type used in x-ray
equipment.
Magnetic field: It is the field around the
magnet which attracts or repels other
magnets.
 Magnetic field strength increases with
the increase in number of coil turns.
 Magnetic field strength increases with
incretion of iron core.
 Magnetic field strength increases with
increase in current in the coil. But
only to a certain level.
Application of electromagnets in radiology:
1. Breaks. To hold the x-ray tube &
table.
2. Relays. A switch which controls the
pass of electrical current.
3. Meter (voltameter, ammeter) a device
which measures the mA, s & kv on the
control panel.
Types of meters:
I. Moving iron meter
II. Moving coil meter
CHAPTER #9
13
Current electricity
Alternating current
Direct
current
-The direction changes
-one direction
for
for the flow of current.
The flow of
current
number of cycles/sec.
one cycle is one complete
waveform.
Frequency: it is the number of cycles/sec.
unit is Hertz (Hz).
1Hz= 1cycle/sec.
Frequency of current is (50Hz or60Hz).
Transformer: A device or an equipment which can
increase or decrease the voltage and current.
Types of transformers used in x-ray units:
1. Autotransformer.
2. Voltage stabilizer.
3. High tension transformers.
4. Filament transformer.
CHAPTER #10
Electromagnetic Radiation
A steam of photons traveling at the speed of
light in an electrostatic and magnetic field.
Properties of EMR:
1. Cosmic rays: stars, high energy,
background radiation.
2. Gamma rays: radioactive isotopes, NM, high
energy, coblat60…
3. X-ray: (soft=low energy), (hard= high
energy).
4. Ultraviolet: Sun, causes cancer.
5. Light: sun, fire, lamps.
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6.
7.
8.
Infrared: sun, hot objects , used for
muscular pain.
Microwave: communication, oven.
Radio waves: radar, radio,TV.
Intensity: Amount of x-ray in a unit time or a
unit area.
Factors affecting Intensity:
1. mA  Intensity.
2. time   “.
3. Kv   “.
4. Distance 
“.
5. filtration   “.
6. Atomic number (z) of target  
“.
Factors effecting quality of x-ray:
1. mA  No effect on quality.
2. time  “.
3. distance 
“.
4. Kv


quality.
5. Filtration
  quality.
Inverse square law:
Intensity: amount of x-ray in a unit time or a
unit time.
Law: The intensity from a source is inversely
proportional to the square of the distance.
I (intensity)  1/d (distance)
I
15
=1/4 I
CHAPTER #11
Mechanism of X-ray Production
Interaction of electrons at the target (the
target is made of ---------.
 MECHANISM 1:
When an incoming electron hits the
electron of the tungsten atom, It will
give energy to the tungsten electron which
will go into higher energy state. When it
goes back to its normal energy level ,It
will release heat and x-ray.
 MECHANISM 2:
When an incoming electron hits the bound
electron in the tungsten atom, It gives
some of the energy to the bound electron
and will change in direction and interact
with another bond electron until it loses
all its energy as heat.
 MECHANISM 3:
(Formation of Characteristic x-ray)
When an incoming electron hits a bond
electron of the tungsten atom, it losses
all its energy and produces PHOTOELECTRON.
If the bound electron is knocked out of
the inner shell then an electron from an
outer shell will move to fill the space.
In doing so it losses energy as
CHARACTERISTIC X-RAY…
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 MECHANISM 4:
(Bremsstrahlung Radiation)
When an incoming electron interacts with
the tungsten atom and has sufficient
energy and passes next to the nucleus
(which has a +ve charge), it will attract
the electron and change its direction
without hitting the nucleus. In doing so
the energy is converted into heat and xray.
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