History_of_x_ray in the medical field.pptx

1
DR REJO JOHN
JR 1
DEPARTMENT OF RADIOLOGY
ARMCH
History of X-rays
Basics of Radiation

08/28/2024 2
1ST
PART-
HISTORY
OF
X-RAYS

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Coverage:
 Brief background
 How Xrays were discovered
 How Xrays work
 Events before discovery and shortly
after discovery
 How Xray discovery changed society
and a new discipline was born…..

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Brief Background
 X-rays were first
discovered accidentally
by Wilhelm Conrad
Röntgen in 1895.
 X-rays are waves of
electromagnetic
energy that have a
shorter wavelength
than normal light

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 He discovered that these new invisible
rays could pass through most objects
that casted shadows including human
tissue but not human bones and
metals.
 Within a year of the discovery many
scientists replicated the experiment
Röntgen performed and began using it
in clinical settings
 In 1901 Röntgen won the first Nobel
Prize in Physics

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How They Were Discovered
 Röntgen discovered the
new ray while working with
a cathode tube in his
laboratory.
 The tube was a glass bulb
that had positive and
negative electrodes inside.
 When the air was removed
from the tube, and a high
voltage was applied it
produced a florescent
glow.

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How Were They Discovered
 To further observe the rays he
positioned a screen in front of
the tube. He began placing
various objects between the
screen and the tube that was
emitting the X-rays.
 He discovered that the rays or
“invisible light” passed right
through pieces of black paper
and thin sheets of aluminum
and copper.
 but that the light did not pass
through blocks of lead and his
bones, and instead these
objects casted shadows on the
screen. This is because these
objects have higher density so
there is less space between
their atoms for the rays to pass
through.
This is a representation of the lead block
experiment.

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How X-Rays Work
 When electrons are emitted from the cathode
and move towards a piece of metal inside the
tube. The electrons will collide with the atoms of
the metal target and decelerate rapidly. If the
electrons have enough energy they can knock an
electron from an inner shell to outer shell. When
the electron drops back down to the inner shell ,
X-rays are emitted.
 Just incase if we could visualize it, to make more
sense here is a representation: -------

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Before X-Rays were
discovered
 Before they were discovered no such thing existed in
the physical world.
 When doctor’s diagnosed broken bones, tumors, and
bullet locations it was all based on their best guess, and
physical examinations.
 This could be very painful for patients. Think about
somebody just squeezing your broken leg until they
could find the place of the break.
 Rumor has said that an Italian Surgeon, Guido Lanfranc
used to check for breaks in a skull by placing a string
between patients teeth and plucking it out. If it made a
musical note the skull was in tact. If was dim or of toned
it showed a broken bone.

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Shortly After the Discovery
 Röntgen began using his discovery
to do his own X-rays on things
such as his wife Bertha’s hand with
ring on her finger, and weights in a
box.
 Other scientists began to replicate
the experiment because it was
easy using a cathode tube.
 Interest in the rays began to
increase and many magazines,
and newspapers began reporting
on them. People were very
fascinated by the discovery
although a few feared it, and that
it would allow strangers to see
through walls, which is now known
to be inaccurate.
Röntgen’s first x-ray of his
wife’s hand

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How X-Rays Changed
Society
 The most important and obvious
impact of the x-ray is its use in
medicine. They are used for
broken bones, teeth, internal
organs, tumors, etc. They have
become the most reliable and
widely spread tool for
diagnosing internal problems.
 Hard x-rays, which have very
high frequency rays, are used for
radiotherapy for cancer patients.
 X-ray machines have also helped
greatly with security, like the
security scanners used to
examine bags at airports.

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How X-rays Changed
Society
 They are used to inspect
canned foods on a conveyor
belt in factories. X-rays will
beam into the can and if it is
not properly filled or has a
foreign substance in it an
alarm will be set off and the
can will be removed. Similar
technique is used in many
factories for various products.
 They have also been used in
science to learn about the
different structures of matter,
especially crystals

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Cntnd…..
A new medical specialty was born:
Radiology
Traditionally, radiology was divided into two
disciplines:
Diagnostic
Therapeutic.
As each field continued to develop and grow in
complexity, it became apparent that separation
of MULTIPLE specialties was needed. Today, one
trains in diagnostic radiology , interventional
radiology, radiation oncology and so on.

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Imaging modalities in diagnostic
Imaging
1. Plain film radiography
2. Fluoroscopy
3. Contrast-enhanced radiography
4. Conventional Tomography
5. Computerized tomography
6. Nuclear imaging (scintigraphy)
7. Magnetic resonance imaging
8. Diagnostic ultrasound and so on…

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2nd
part -BASICS OF
Radiations
 Electromagnetic radiations
 Electromagnetic spectrum
 Classification of EMR
 General properties
 Xrays

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What are electromagnetic
radiation?
 EMR are a family of radiation, which
differ one from the other by their
wavelengths and their effects. They are:
 Radio waves, microwaves, visible light,
gamma and x rays are all examples of
electromagnetic waves.
 Their effects:
shorter wavelength=> greater energy =>
greater ability to penetrate.

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Classification of EMR
 Non-Ionizing Radiation:
ultraviolet (UV), visible light, infrared (IR),
microwave (MW), radio frequency (RF),
and extremely low frequency (ELF).
 Ionizing Radiation
 ultraviolet, X-ray, gamma rays

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General properties of EMR
1. It travels in straight lines
2. Its intensity obeys the inverse
square law.
3. It is not deflected by a magnetic
field.
4. It can be transmitted through a
vacuum.
5. It is subject to diffraction and
interference.

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Inverse Square Law.
The intensity of radiation at different distances is represented by the
formula:
This is the Inverse Square Law.

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TheInverseSquareLaw.
Inverse Square Law - double the
distance from the source of
radiation - reduce dose by a factor
of 4
 Inverse Square Law - double the distance
from the source of radiation - reduce
dose by a factor of 4

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What are X-Rays?
 A form of electromagnetic radiation (EMR)
 Their frequency and energy is being much
greater than visible light attributable to its
extremely short wavelength.
 X-radiation has a wavelength in the region of
10-10
meters or a frequency of 1018
Hz.
No weight - No charge
 The energy of X-Ray is “PHOTONS”
 Photon energy is measured in eV or Kev
 Diagnostic X-Rays range from 20-150 Kev
 Penetration in materials

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Basic structure of Atom

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Production of X-rays:
Bremsstrahlung radiation
X-ray
Projectile electrons originating from the cathode filament impinge on
atoms in the anode and will often pass close by the nucleus of these
atoms.
As the electrons pass through the target atom they slow down,
with a loss in kinetic energy. This energy is emitted as x-rays.
The process is known as bremsstrahlung or “braking energy”.

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 Bremsstrahlung X-rays form a continuous
energy spectra. The frequency
distribution is continuous and shows that
the Bremsstrahlung process produces
more low energy than higher energy x-
rays. The average energy is
approximately 1/3 of the Emax.
E max

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 The Emax or the maximum energy of the
X-rays measured as (keV) is equal to
voltage applied to the Xray tube (kilovolt
peak or kVp).
 For example:
 An applied voltage of 70 kVp produces an
x-ray spectra with Emax of 70 KeV and
average energy of about 23 keV.
70KeV
23keV

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Characteristic X-ray Radiation
• To produce characteristic x-rays the projectile electrons
must have sufficient energy to displace orbital electrons
• If the projectile electron has sufficient energy, it may cause the
ejection of an orbital electron (usually in the K shell) from an
atom in the anode.
• An outer shell electron (usually from the L or M shells) fills the
vacancy in the inner orbital and sheds energy as an x-ray of
characteristic energy.

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• The most common transition is from L
to K shell.
•Each shell transition has a characteristic energy
and this energy is dependent on the atomic
number of the atom.
•M-to-K transitions are less common and
are of higher energy.
•For tungsten the characteristic X-ray spectra are
represented by peaks at 58 and 69 keV
representing L-to-K and M-to-K shell transitions
respectively.

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X-ray
K Shell
L shell
M shell
Production of Characteristic X-rays

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X- Ray Tube
A review is made of:
 The main elements of the X- Rays tube:
cathode and anode structure
 The constraints of the anode and
cathode material used.
 The rating charts and X Ray tube heat
loading capacities

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Basic elements of an X -Ray source
assembly
 Generator : power circuit supplying the
required potential to the X Ray tube

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X- Ray tubes
X -Ray tube producing the X- Ray beam

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X- Ray tube components
 Cathode: heated filament which is the
source of the electron beam directed
towards the anode
 tungsten filament
 Anode (stationary or rotating): impacted
by electrons, emits X -Rays, > 99% of
electron energy is dissipated as heat
 Metal tube housing surrounding glass (or
metal) X -Ray tube (electrons are traveling
in vacuum)
 Shielding material (protection against
extra-focal spot radiation from anode)

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The Anode
 THE ANODE IS THE +++++ SIDE OF THE
X-RAY TUBE

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FUNCTIONS OF ANODE
Target For Projectile Electrons.
Conductor Of High Voltage From The
Cathode Back To X-ray Generator.
Primary Thermal Conductor

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Tungsten Is The Material Of Choice
For The Target Of General Use X-
ray Tubes.
Reasons Are:
High Atomic Number ( Z#) 74.
High Z# Increased Efficiency Of X-ray
Production.
High Melting Point 3422 C (Cathode)
High Thermal Conductivity
A tungsten-rhenium alloy used now(90:10)

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Types of Anode
 X-ray tubes are classified by the type of
anode:
 Stationary ( top)
 Rotating (bottom)

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The Stationary Anode
 Stationary anodes are used in
dental x-ray and some portable x-ray
machine where high tube current
and power are not required.

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The Rotating Anode
 The rotating anode allows the
electron beam to interact with a
much larger target area.
 The heat is not confined to a small
area.

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Contd….
 The Anode must also be a good thermal
conductor.
 When the electron beam strikes the
anode more than 99% of the kinetic
energy is converted to heat.
 Tungsten-rhenium is used as the target for the
electron beam .
 Tungsten is used for three reasons
 High atomic number
 Heat conductivity
 High melting point..

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THE CATHODE
 The Cathode Is A Complex Device And
Can Be Referred To As The Cathode
Assembly. This Assembly Consists Of
The :
Filaments,
 Focusing Cup, And
Associated Wiring.

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Cathode
 Made up of: tungsten material : preferred
because of its high melting point (3422°C)
 Slow filament evaporation
 No arcing
 Minimum deposit of W on glass envelope
To reduce evaporation the emission
temperature of the cathode is reached
just before the exposure
 in stand-by, temperature is kept at ± 1500°C
so that 2700°C emission temperature can
be reached within a second

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TUBE OPERATION

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Production of images
X Ray tube
Collimator
Beam
Soft
tissue
Bone
Air
Patient
Table
Grid
Cassette
AEC detectors

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 A round or rectangular device attached to the
tube head.
 Serves to shape the x-ray beam.
 Help the operator aim the beam at the
structures of interest.

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III. X-Ray beam
The beam emerging from the collimator is
called the primary, or useful beam.
A. Energy composition: heterogeneous
B. X-ray quality:
Refers to its energy=>affects its
penetrability
Determines the contrast of the
radiographic image.
• It has also influence on density at a
lesser degree.
Set by KVp control.

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c. X-Ray quantity/intensity:
Refers to the number of x-rays.
Determines the radiographic density.
Controlled by mA and exposure time (mAs).
Factors that affect intensity:
Inherent and added filter
Distance: the inverse square law
Attenuation=>absorption and scatter
IV. Control panel:
used for selection of exposure factors:
Kv, mA & time

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V. Object /patient
 Image production by X-Rays results
from attenuation of those x-rays by
the material through which they
pass.
 Factors that affect
absorption:
The thickness of the substance in the direction
of x-rays.
The density or concentration of the substance.
The atomic number of the substance (Z)
The nature of the radiation energy: wavelength

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VI. Recording media
 1. X-ray film( earlier):
Composition:
Base: plastic sheet coated with:
• adhesive layer
• Emulsion that contains silver bromide and a
small amount of silver iodide. This emulsion is
sensitive to light and radiation.
• Super coat: a protective coating.
When the film is exposed to light or to
ionizing radiation and developed, chemical
changes takes place within the emulsion,
resulting in the deposition of metallic
silver, which is black.

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15.1: Optimization of protection in radiography:
technical aspects 57
Radiographic film structure
Emulsion
Base
Supercoat
Emulsion
Adhesive layer
Double Emulsion Film
Adhesive layer
Supercoat

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Contd….
2. fluoroscopic screen/image
intensification system.
3. Photoelectric detector
crystals
4. Xenon detector systems and
5.Computer-linked detectors

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Radiographic densities
 Physical density vs radiographic
density
 Radiographic density is a term that
refers to the degree of blackness of a
film.
Radiolucent
Radiopaque
the increasing order of physical density:
air,fat water/soft tissue and bone/metal
radiographic density: black, gray-black,
gray and white, respectively.

History_of_x_ray in the medical field.pptx

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History_of_x_ray in the medical field.pptx