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Production Of Ray

Important Notes

• The X-ray machine has an X-ray tube, which consists of
  • Cathode, which serves as a source of electrons.
  • Anode (target) at which beam of high-speed electrons are directed
• The cathode has filaments and a focusing cup.
  • Filaments are coils of Tungsten, which is the source of electrons within the X-ray tubes.
  • The Molybdenum Focusing Cup focused the electrons within the X-ray tubes.
• The anode is composed of a Tungsten Target and Copper Steam.
  • The target serves the purpose of converting the kinetic energy of electrons emitted from the cathode source into X-ray photons.
  • Tungsten is selected because of its properties such as high atomic number, high melting point, and low vapor pressure.
  • Copper Stem dissipates heat thereby reducing the risk of target melting.

Production Of Ray Long Essays

Question 1. What are the parts of an X-ray tube? Describe the working of the X-ray tube and add a note on Bremmstrahlung radiation.
Answer.

Apparatus:

• Cathode:
  • Filaments
  • Focussing cup
• Anode
  • Tungsten target
  • Copper stem
• Glass tube:
  • It encloses the above apparatus
  • Cathode:
    • Filaments
      • Made up of tungsten wire
      • It is connected to electric current
      • On passage of electric current through this filament, it gets heated and emits electrons
      • A milliampere current controls the number of electrons
    • Focussing cup
      • It is made up of molybdenum
      • It is a concave reflector cup
      • The electrons emitted from the filament are received by it
      • These electrons are then focused toward the focal spot which is the anode
  • Anode:
    •  Tungsten target
      • This converts the kinetic energy of electrons into X-ray photons
    • Copper stem
      • It is a good thermal conductor

Electric current → heats the filament → Electrons are emitted from it → Electrons get collected towards the focusing cup → this focusing cup reflects the electrons to the tungsten target → this tungsten target converts electrons to X-ray photons

Bremmstrahlung Radiation:

• These are produced due to high-speed electrons
• These electrons pass just near the nucleus
• These are attracted by the positively charged nucleus
• This leads to the loss of some of its kinetic energy
• Further results in deflected and decelerated electron and low energy photons

Read And Learn More: Oral Radiology Question and Answers

When an electron comes close to the nucleus of a tungsten atom and is slowed down, an X-ray photo of lower energy known as general radiation results

An electron that dislodges an inner shell electron from the tungsten atom results in the rearrangement of the remaining orbiting electrons and the production of an X-ray photon known as characteristic radiation

Production of Ray Short Essays

Question 1. X-ray machine/Working of X-ray tube.
Answer.

Apparatus:

• Cathode:
  • Filaments
  • Focussing cup
• Anode
  • Tungsten target
  • Copper stem
• Glass tube:
  • It encloses the above apparatus
  • Cathode:
    • Filaments
      • Made up of tungsten wire
      • It is connected to electric current
      • On passage of electric current through this filament, it gets heated and emits electrons
      • A milliampere current controls the number of electrons
    • Focussing cup
      • It is made up of molybdenum
      • It is a concave reflector cup
      • The electrons emitted from the filament are received by it
      • These electrons are then focused toward the focal spot which is the anode
  • Anode:
    • Tungsten target
      • This converts the kinetic energy of electrons into X-ray photons
    • Copper stem
      • It is a good thermal conductor

Electric current → heats the filament → Electrons are emitted from it → Electrons get collected towards the focusing cup → this focusing cup reflects the electrons to the tungsten target → this tungsten target converts electrons to X-ray photons

Question 2. Position indicating device [PID].
Answer.

Position indicating device [PID]

It is an open-ended lead cylinder that extends from the opening of the metal housing of the tube head also called the “cone”

It appears as an extension of the tube head

Position Indicating Device Types:

• Conical
• Rectangular
• Round

Position Indicating Device Significance:

• Long PID results in less divergent X-ray beam
• This minimizes the irradiation of tissues
• Causes increase in target film distance
• This further improves the quality of the image

Question 3. Production of X-ray
Answer.

Production of X-ray

• Potential differences develop between cathode and anode
• This results in the emission of electrons from the tungsten filament
• The emitted electrons are stopped suddenly at the focal spot
• This sudden stoppage causes the conversion of electrons into X-ray photons
• The heat generated during the process is absorbed by the oil circulated in the glass of the X-ray tube

Production of X-ray Mechanism:

• Bremmstrahlung Radiation:
  • These are produced due to high-speed electrons
  • These electrons pass just near the nucleus
  • These are attracted by the positively charged nucleus
  • This leads to the loss of some of its kinetic energy
  • Further results in deflected and decelerated electron and low energy photons
• Characteristic radiation:
  • The high-energy electrons hit the target atom
  • Electrons are ejected from the inner orbit
  • This leads to a vacancy that is filled with electrons from the outer orbit

This results in the emission of a photon whose energy is equivalent to the difference in the energy levels of two orbits

When an electron comes close to the nucleus of a tungsten atom and is slowed down, an X-ray photo of lower energy known as general radiation results

An electron that dislodges an inner shell electron from the tungsten atom results in the rearrangement of the remaining orbiting electrons and the production of an X-ray photon known as characteristic radiation

Production Of Ray Short Answers

Question 1. Bremmstrahlung radiation.
Answer.

Bremmstrahlung radiation

• These are produced due to high-speed electrons
• These electrons pass just near the nucleus
• These are attracted by the positively charged nucleus
• This leads to the loss of some of its kinetic energy
• Further results in deflected and decelerated electron and low energy photons

When an electron comes close to the nucleus of a tungsten atom and is slowed down, an X-ray photo of lower energy known as general radiation results

An electron that dislodges an inner shell electron from the tungsten atom results in the rearrangement of the remaining orbiting electrons and the production of an X-ray photon known as characteristic radiation

Question 2. Characteristic radiation.
Answer.

Characteristic radiation

• The high-energy electrons hit the target atom
• Electrons are ejected from the inner orbit
• This leads to vacancy that is filled with electrons from the outer orbit

This results in the emission of a photon whose energy is equivalent to the difference in the energy levels of two orbits

X-ray tube with a rotating anode, which allows the head at the focal spot to spread out across a large surface area

Question 3. Focal spot.
Answer.

Focal spot

• The area of the target at which the electrons are absorbed and X-rays are generated is called the focal spot
• The size and shape of the focal spot is determined by the size and shape of the electron stream when it hits the anode

Focal spot Types:

• Actual focal spot
  • It is the area on the anode that is struck by the electrons
• Effective focal spot
  • It is the length and width of the emitted X-ray beam as projected down the central axis of the X-ray tube

Production Of X-Ray Viva Voce

• The cathode of the X-ray tube is made up of tungsten
• Anode is made up of tungsten embedded in copper stem
• The target is kept at an angle of 20°
• Radiations produced from focal spots are primary radiations
• Radiations that are reflected from objects are secondary
• Factors necessary for the production of X-rays are a source of electrons, an accelerator, and the target
• 0.2 – 0.8% of cathode rays are transformed into X-rays after striking the anode target.
• The average wavelengths of X-rays used in dentistry is 0.6 – 1 A.U.
• X-rays

Properties Of X-Ray

Important Notes

• Properties of X-rays
  • Travel at the rate of speed of light
  • Invisible
  • Cannot be focused, reflected or reflected
  • Effected by magnetic and electrical fields
  • They effect photographic plates
  • They cast shadows of the object in their paths
• The three mechanisms that explains the interactions of X-rays with matter are
  • Coherent scattering
  • Photoelectrical absorption
  • Compton scattering
• Thomson Effect/Classical Scattering/Coherent Scattering
  • It occurs when a low – energy incident photon passes near an outer electron of an atom
  • The incident photon is non absorbed but scattered without loss of energy.
  • Energy of scattered photon = Energy of incident photon
  • It accounts for about 8% of the total number of interactions
• Photoelectric Absorption.
  • It occurs when an incident photon collides with a bound electron in an atom.
  • The incident photon is absorbed and the electron is expelled from its shell and becomes a photoelectron
  • Energy of photoelectron = Energy of incident photon – blinding energy of electron.
  • It accounts for about 30% of interactions.
• Compton Scattering.
  • It occurs when a photon interacts with an outer electron of an atom.
  • The electron receives kinetic energy and recoils from the point of impact.
  • The incident photon is scattered from the site of collision, making the atom ionized.
  • Approximately 62% of photon undergo Compton scattering.
  • Compton scattering is the major source of secondary radiation.
• Inverse square law.
  • It states that the intensity of the X-ray beam is inversely proportional to the square of the distance from the source to the film
  • Increased distance leads to the divergence of the X-ray beam

Properties Of X-Ray Short Essays:

Question 1. Properties of X-ray.
Answer.

Properties of X-ray

• Physical Properties:
  • It is electromagnetic radiation
  • It travel through space
  • They travel in a straight line
  • X-ray travel with the speed of light
  • They cannot be reflected, refracted or deflected
  • They show properties of interference, diffraction
  • They do not have any mass or weight
  • They obey inverse square law
  • These are produced by collision of electrons
• Chemical Properties:
  • These induce color changes of several substances
  • Example: Methylene blue gets bleached
  • Cause oxidation of ferrous sulphate to ferric sulphite
  • Causes destruction of the fermenting of enzymes

Read And Learn More: Oral Radiology Question and Answers

• Biological Properties:
  • Excitation – this property is used in the treatment of malignant tumor
  • Germicidal property – This property is used for sterilization oand preservation of food
• Physiochemical Property:
  • Causes blackening of photographic paper on paper
  • This property is known as photographic effect

Question 2. Interaction of X-ray with matter.
Answer.

Interaction of X-ray with matter

• Coherent scattering:
  • Low energy photon passing near atom of outer electron gets scattered without loss of energy
  • Incident photon causes vibration of electrons
  • This electron radiates energy in the form of another X-ray photon
    Significance:
    • 8% of total X-ray interaction are consist of it
    • Effect of it in producing film fog is negligible
• Photoelectric effect:
  • When the incident photon strikes inner orbital electron, it is ejected as photoelectron
  • Vacancy of ineer orbit is filled by electron from higher energy level
  • The ejected electrons travel only a short distance
  • All of the energy of photons is deposited in the absorber
    Significance:
    • Consists of 30% of total interaction
    • It is good for dentist
    • But it is bad for patients due to increased absorption
• Compton effect:
  • Photon interacts with the outer free electron
  • It results in formation of scattered photon of low energy
  • As well as ejection of recoil electron
    Significance:
    • Consists of 62% of total interactions
    • It is good for patients
    • But it is bad for dentist as it causes film fog

Properties Of X-Ray Short Answers

Question 1. Inverse Square law.
Answer.

Inverse Square law

• It states that the intensity of the X-ray beam is inversely proportional to the square of the distance from the source to the film
• Increased distance leads to the divergence of the X-ray beam
• Thus number of photons decreases
• As a result, intensity of the X-ray beam diminishes
  1 ∝ 1/d²
  1 = k/d², where k is constant

Question 2. Compton effect.
Answer.

Compton effect

• Photon interacts with the outer free electron
• It results in formation of scattered photon of low energy
• As well as ejection of recoil electron

Compton Effect Significance:

• Consists of 62% of total interactions

• It is good for patient
• But it is bad for dentist as it causes film fog

Question 3. Uses of X-ray
Answer.

Uses of X-ray

• Used for diagnostic purposes
• Medicolegal use
• For treatment of tumours
• For treatment of skin diseases
• To improve the quality of oil paints
• For crystallography
• For sterilization of instruments
• As detective measure
• Used in the field of engineering
• As spectroscopy
• As photochemistry
• In the field of radiobiology

Question 4. Coherent scattering.
Answer.

Coherent scattering

• Low energy photon passing near atom of outer electron gets scattered without loss of energy
• Incident photon causes vibration of electrons
• This electron radiates energy in the form of another X-ray photon

Coherent Scattering Significance:

• 8% of total X-ray interaction are consist of it
• Effect of it in producing film fog is negligible

Properties Of X-Ray Viva Voce

• X-ray have neutral charges
• Velocity of x-ray is equal to that of light

Radiation Physics Definitions

• Ionization
  • The conversion of an atom into an ion is called Ionization
• Ionizing radiation
  • It is defined as radiation that is capable of producing ions by removing or adding electrons to an atom
• Resolution
  • Resolution is the ability of a radiograph to record separate structures that are close together

Radiation Physics Important Notes

• The Conversion of an atom into an ion is called Ionization
  • The radiation, that brings about the ionization of atoms, is called ionizing radiation.
• Radiation is of two types
  • Particulate
    • Particulate radiation consists of atomic nuclei that transmit kinetic energy using their small masses moving at very high velocities Eg: Alpha rays, Beta rays, and Cathode rays
    • Alpha rays consist of a high-speed stream of doubly ionized helium nuclei.
    • Alpha rays have higher LET, thus they are more damaging to the biological systems than X-rays.
  • Non – particulate/electromagnetic
    • Electromagnetic radiation is produced when the velocity of an electrically charged particle is alerted Eg: Radio, TV, Microwaves, infrared, Visible, Ultraviolet, X-rays, Gamma, and Cosmic rays.
    • The above examples are in the increasing order of their energy and decreasing order of their wavelengths.
• Types of electromagnetic radiation
  • Ionizing radiation
  • Nonionizing radiation

Radiation Physics Short Essays

Question 1. Electromagnetic radiation.
Answer.

Electromagnetic radiation

• It is a combination of electric & magnetic fields
• Generated when the velocity of an electrically charged particle is altered.

Radiation Physics Types:

• Ionizing radiation
• Nonionizing radiation

Radiation Physics Properties:

• Travel in a straight line
• They travel at the speed of light
  • They neither have mass nor weight
  • They transfer energy from place to place in the form of photons
  • They obey the inverse square law
  • These are invisible radiations

Read And Learn More: Oral Radiology Question and Answers

Question 2. Electromagnetic Spectrum
Answer.

Electromagnetic Spectrum

It comprises of the following radiations

Short Answers

Question 1. Ionizing radiation
Answer.

Ionizing radiation

• It is defined as radiation that is capable of producing ions by removing or adding electrons to an atom

Ionizing radiation Classification:

• Particulate radiation.
  • This transmits kinetic energy by extremely fast-moving small masses
  • Types are electron, alpha, protons & neutrons
• Electromagnetic radiation
  • It is the propagation of wave-like energy through space or matter

Question 2. Timer
Answer.

Timer

• A timer is built into high high-voltage circuit to control the duration of the X-ray exposure
• The electronic timer controls the length of time that high voltage is applied to the tube and the time during which tube current flows and x-rays are produced
• Some X-ray machine timers are calibrated in fractions of a second whereas others are expressed as the number of pulses in an exposure
• The number of pulses divided by 60 gives the exposure time in seconds

Question 3. Exposure time
Answer.

Exposure time

• It is one of the factors controlling X-ray beam
• Changing the exposure time modifies the duration of the exposure and thus the number of photons generated
• When the exposure time is doubled, the number of photons generated at all energies in the X-ray emission spectrum is doubled
• The range of photon energies is unchanged.

Question 4. Resolution
Answer.

Resolution

• Resolution is the ability of a radiograph to record separate structures that are close together
• It is measured by radiographing an object made up of a series of thin lead strips with alternating radiolucent spaces of the same thickness
• The group of lines and spaces are arranged in test targets in order of increasing the number of lines and spaces per millimeter
• It is measured as the highest number of line pairs per millimeter that can be distinguished on the resultant radiograph when examined with low-power magnification

Viva Voice

• X-rays were discovered by Roentgen in 1895