Oral Radiology

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