X-rays can interact with matter through various processes. The most common interactions in diagnostic radiology are the photoelectric effect, Compton scattering, and coherent scattering. In the photoelectric effect, an incoming x-ray photon ejects an inner shell electron, leaving behind characteristic radiation. Compton scattering involves x-ray photon deflection by a free electron, producing scatter radiation. Coherent scattering changes a photon's direction but not its energy. These interactions have different probabilities depending on the photon energy and the electron binding energy.
Interactions of X-ray & matter & Attenuation - Dr. Sayak DattaSayakDatta
Slideshow on Radio-physics covering different interactions between X-ray and matter along with Attenuation. It includes Photo-electric effect, Compton scatter, Coherent scatter, Attenuation of Monochromatic & Polychromatic radiation, Diagnostic Xray applications, Scatter radiations.
Interactions of X-ray & matter & Attenuation - Dr. Sayak DattaSayakDatta
Slideshow on Radio-physics covering different interactions between X-ray and matter along with Attenuation. It includes Photo-electric effect, Compton scatter, Coherent scatter, Attenuation of Monochromatic & Polychromatic radiation, Diagnostic Xray applications, Scatter radiations.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
2. X-ray Interactions with Matter
For understanding the interactions of ionizing radiation and
matter we must review a few points about atomic physics.
The atom consists of a central nucleus and orbital
electrons.
The positively charged nucleus exerts an electric force of
attraction and holds the negatively charged electrons in
specific orbits or shells. The innermost shell is called the
K shell and more the peripheral shells are named
consecutively L, M, N, and so forth.
They have a limited electron capacity.
The K shell can hold 2 electrons and L shell has capacity
of 8 electrons.
3. Basic structure of an ATOM :
PROTON ( +ve charge )
An atom is made up of NUCLEUS
NEUTRON ( neutral )
ORBITAL ELECTRONS ( -ve charge )
ORBITS / SHELLS ( K, L, M, N etc. )
4. Each shell has specific binding energy. The closer the
shell is to nucleus, the tighter the electrons are ‘bound’ to
the nucleus.
The electrons in the outer most shell are loosely bound.
They are essentially free and are called ‘free’ or ‘valence’
electrons.
5. There are 5 basic ways that an x-ray photon can interact
with matter. These are:
1. Photoelectric effect
2. Coherent or unmodified scattering
3. Compton interaction with modified scattering
4. Pair production
5. Photodisintegration
6. 1. Photoelectric effect
The photoelectric effect always yields three end products:
1) Characteristic radiation
2) A negative ion ( the photoelectron)
3) A positive ion ( an atom deficient with one electron)
7.
8. Characteristic radiation generated by the photoelectric effect
is exactly the same as production of x-rays
The only difference in the method used to eject the inner
shell electron.
In x ray tube a high speed electron ejects the bound
electron.
While in photoelectric effect an X ray photon does the trick.
In both cases the atom is left with an excess of energy =
the binding energy of an ejected electron.
It is usually referred to as ‘Secondary Radiation’ and is to be
differentiated from scatter radiation.
CHARACTERISTIC RADIATION
9. How does this happen ?
After the electron has been ejected, the atom is left with a
void in the K shell & an excess of energy equivalent to the
binding energy.
This state of the atom is highly unstable & to achieve a
low energy stable state ( as all physical systems seek the
lowest possible energy state ) an electron immediately
drops in to fill the void.
As the electron drops into the K shell, it gives up its
excess energy in the form of an x-ray photon. The amount
of energy released is characteristic of each element &
hence the radiation produced is called Characteristic
radiation.
10. Photoelectric Effect
This type of interaction is most likely to occur when the energy
(hv) of an incident/ incoming photon with slightly greater energy
than the binding energy of the electrons in one of the inner shells.
The incident photon looses all its energy on entering an atom
being absorbed in this process.
Immediately, the atom responds by ejecting an electron, usually
from K or L shell, leaving a hole in that shell.
Now the atom is ionized positively and in an excited state.
Electron from higher energy level fills the hole in the K shell, a
‘characteristic x-ray photon’ is being emitted.
Note: that the energy of the incident photon ultimately went to free
the electron from its shell and set it motion as ‘photoelectron’
11. Summary: The energy of the incoming photon in the photoelectric
interaction involving the K shell has the following fate:
a) The photon enters atom and completely disappears.
b) A K-shell electron is ejected, leaving a hole.
c) Atom has excess energy – is in a excited state.
d) A part of photon’s energy was used to liberate electron and the
rest to give it kinetic energy; ejected electron is a photoelectron.
e) Hole in K shell is filled by electron transition from a shell father
out, accompanied by emission of a characteristic x-ray photon.
f) Holes in successive shells are filled by electron transitions from
shells still farther out, each transition accompanied by a
corresponding characteristic x-ray photon.
g) Sum of the energies of all the characteristic photons equals to
binding energy of shell from which the photoelectron originated,
in this case, the K shell.
12. Probability of occurrence:
3 simple rules govern the probability of occurrence
1) The incident photon must have sufficient energy to overcome
the binding energy of the electron.
2) A photoelectric reaction is most likely to occur when the photon
energy and electron binding energy are nearly the same.
3) The tighter an electron is bound in its orbit, the most likely it is to
be involved in the photoelectric reaction.
Application to diagnostic radiology:
Advantage:
It produces radiological images of excellent quality.
Does not produce scatter radiation.
It enhances natural tissue contrast (as some tissues absorb more
x-rays than other tissues.
Disadvantage:
Patients receive more radiation.
All the energy of incident photon is absorbed by the patient.
13. Coherent or unmodified
scattering
Radiation undergoes a change in direction without change in
wavelength, thus sometimes it is called as “ unmodified
scattering”
There are two types of coherent scattering:
Both the types are described in terms of wave-particle
Interaction and therefore also called as ‘Classical
scattering’
i. Thomson scattering: Single electron involved in the
interaction.
ii. Rayleigh scattering: there is Co-operative interaction of
all the electrons.
14.
15. What happens in coherent scattering ?
Low energy radiation encounters electrons
Electrons are set into vibration
Vibrating electron, emits radiation.
Atom returns to its undisturbed state
16. • No energy is transferred and no ionization occurs.
• Its only effect is to change direction of incident
radiation.
• It occurs less than 5% and is not important in
diagnostic radiology. It produces scattered
radiation but of negligible quantity.
17. Compton interaction
The Compton effect occurs when an incident x-ray photon with
relatively high energy strikes a free outer shell electron, ejecting
it from its orbit.
The photon is deflected by the electron so that it travels in new
direction as scatter radiation.
The reaction produces an ion pair
A +ve atom
A –ve electron ( recoil electron )
18. Almost all the scatter radiation that we encounter in diagnostic radiology
comes from Compton Scattering.
Energy of photon distributed in two ways:
Part of it goes to recoil electron as Kinetic energy.
And the rest is retained by the deflected photon.
Two factors determine the amount of energy the photon transmits:
The initial energy of the photon.
Its angle of deflection.
1.Initial energy :- Higher the energy more difficult to deflect.
High energy : Travel straight retaining most of the energy.
Low energy : Most scatter back at angle of 180º
2. Angle of deflection :- Greater the angle, lesser the energy
transmitted. With a direct hit, maximum energy is transferred to the
recoil electron. The photon retains some energy & deflects back
along its original path at an angle of 180º.
19. The formula for calculating the change in wavelength of a scattered photon
is :
Δλ = 0.024 ( 1 – cos θ ) ,
where Δλ = change in wavelength
θ = angle of photon deflection
20. Disadvantages of Compton reaction :
Scatter radiation : Almost all the scatter radiation that we
encounter in diagnostic Radiology comes from Compton scattering. In
the diagnostic energy range, the photon retains most of its original
energy. This creates a serious problem, because photons that are
scattered at narrow angles have an excellent chance of reaching an x-
ray film & producing fog.
Exceedingly difficult to remove –
• cannot be removed by filters; because they are too energetic
• cannot be removed by grids; because of narrow angles of deflection.
It is also a major safety hazard. Even after 90˚ deflection most of its original
energy is retained.
Scatter radiation as energetic as the primary radiation.
Safety hazard for the radiologist, personnel and the patient.
21. Pair Production
What happens in Pair production ?
A high energy photon interacts with the nucleus of an atom.
The photon disappears & its energy is converted into matter in
the form of two particles
An electron
A positron (particle with same mass as electron, but with
+ve charge.)
Mass of one electron is 0.51 MeV.
2 electron masses are produced.
So the interaction cannot take place with photon energy less
than 1.02 MeV.
It has no importance in diagnostic radiology.
22. Annihilation reaction:
The Positron, as it comes to rest, combines with a negative electron-it
disappears giving rise to two photons with an energy of 0.51 Mev, moving in
opposite direction.
This is annihilation reaction.
23. Photodisintegration
A photon with extremely high energy ( 7-15 MeV), interacts
directly with the nucleus of an atom. It does not occur with
energies less than 7 Mev,
which may eject a neutron, proton or on rare occasions even an
alpha particle.
What happens in Photodisintegration ?
A high energy photon encounters the nucleus of an atom.
Part of the nucleus which may be a neutron, a proton, an alpha
particle or a cluster of particles, is ejected.
It has no diagnostic importance. As we rarely use radiation>150
KeV in diagnostic radiology.
24. To Note:
The photoelectric effect accounts for 75% of
interaction.
Compton scattering for 20%, and
Coherent scattering for 5%,
the total 100%.
26. Ans. The photoelectric effect
always yields three end products:
Characteristic radiation
A negative ion ( the
photoelectron)
A positive ion ( an atom deficient
with one electron)
28. Ans. Annihilation reaction:
The Positron, as it comes to rest,
combines with a negative
electron- it disappears giving rise
to two photons with an energy of
0.51 Mev, moving in opposite
direction.
This is annihilation reaction.