X-RAYS INTRODUCTION
Discovery of X-rays
• Wilhelm Conrad Roentgen, a German physicist, discovered X-rays on November 8,
1895.
• The Experiment: Roentgen was investigating cathode rays (electrons) in a high-
energy vacuum tube. He had the tube enclosed in black cardboard, and the room was
dark to prevent light leaks.
• He noticed a faint glow on a piece of paper coated with barium platinocyanide about 3
feet away. He realized this fluorescence was not caused by light or electrons from the
tube.
• The First Radiograph: Roentgen concluded that a new, unknown type of ray was
being produced. He tested its properties by placing objects between the tube and the
fluorescent screen. When he placed his hand, he saw the outline of his bones. This led
him to create the first medical X-ray image on December 22, 1895, of his wife,
Bertha Roentgen's, hand. The image clearly showed the bones of her hand and her
wedding ring, solidifying the immense potential of this new technology for medicine.
• Roentgen published his findings and was awarded the first Nobel Prize for Physics in
1901.
Nature of X-rays
Electromagnetic Radiation: X-rays are a form of electromagnetic (EM) radiation, which is
the transport of energy through space via electric and magnetic fields. Other examples
include visible light, radio waves, and gamma rays.
Dual Nature: EM radiation, including X-rays, exhibits a dual nature: it can behave as both a
wave and a particle.
✓ Wave Concept: As a wave, EM radiation is described by its wavelength (λ) and
frequency (v). All EM waves travel at the speed of light (c) (c=λv).
✓ Particle Concept: As a particle, EM radiation is composed of discrete bundles of
energy called photons. The energy (E) of a photon is directly proportional to its
frequency and is calculated using Planck's constant (h) (E=hv).
Ionizing Radiation:X- X-rays are a type of ionizing radiation because their photons carry
enough energy (typically greater than 15 eV) to knock electrons out of atoms, which can be
used to form images and also has biological effects.
,Photon Energy–Wavelength Relationship
The energy (E) of an X-ray photon is inversely proportional to its wavelength (λ). This
means, as the energy of the X-ray increases, its wavelength decreases.
This relationship is expressed by the equation:
E(keV) = 12.4 / λ(Å)
E = photon energy in kiloelectron volts (keV).
λ = wavelength in angstroms (Å).
12.4 = constant (Planck's constant (h) x speed of light (c), with units converted from
standard physics to kiloelectron volts (keV) and angstroms (Å).
Significance: This fundamental relationship is crucial for understanding the penetrating
power of X-rays. Higher-energy photons (with shorter wavelengths) can pass through denser
materials more easily, making them ideal for imaging bones and other thick body parts.
Conversely, lower-energy photons (with longer wavelengths) are more easily absorbed and
are used for imaging softer tissues, such as in mammography.
Radiation Units:
Kiloelectron Volt (keV): A unit of energy for photons; 1 keV=1000 eV.
Angstrom (Å): A unit of length used for very short wavelengths; 1 A˚=10−10 m.
Roentgen (R): A unit of radiation exposure in air.
Gray (Gy): The SI unit for absorbed radiation dose, which measures the energy deposited in
a material; 1 Gy=1 J/kg.
Sievert (Sv): The SI unit for dose equivalent, which accounts for the biological effect of
different types of radiation on tissue.
, APPLICATIONS OF X-RAYS
Medical Applications
• Diagnostic Imaging: This is the most common use of X-rays in medicine.
❖ Radiography (Plain X-rays): Used to see dense structures like bones to detect
fractures, as well as tumors and foreign objects.
❖ Computed Tomography (CT scan): Uses multiple X-rays to create detailed,
cross-sectional images of the body, which is excellent for visualizing soft
tissues and diagnosing complex conditions.
❖ Mammography: A specific type of low-dose X-ray used for breast cancer
screening.
❖ Fluoroscopy: Provides real-time, moving X-ray images, used in procedures like
barium studies and angiography to see internal organs in motion.
• Therapeutic Applications: High-energy X-rays are used in radiation therapy to kill
cancer cells and shrink tumors.
Industrial Applications
• Non-Destructive Testing (NDT): This involves using X-rays to inspect materials and
components for flaws without damaging them. It's used for checking welds, castings,
and pipelines for cracks or corrosion.
• Material Analysis: X-ray techniques are used to analyze the composition and
structure of materials.
o X-ray Diffraction (XRD): Analyzes the crystal structure of materials.
o X-ray Fluorescence (XRF): Determines the elemental composition of
materials.
• Food Inspection: Detects foreign objects (metal, glass) in food products.
• Art and Archaeology: Examines internal structures of artifacts and paintings
Security Applications
• Baggage Scanners: Screen luggage for weapons, explosives, and contraband.
• Body Scanners: Used for personal security checks.
• Mail Scanners: Inspect packages for suspicious contents.
• Cargo Inspection: Screens large containers for illicit materials.
Discovery of X-rays
• Wilhelm Conrad Roentgen, a German physicist, discovered X-rays on November 8,
1895.
• The Experiment: Roentgen was investigating cathode rays (electrons) in a high-
energy vacuum tube. He had the tube enclosed in black cardboard, and the room was
dark to prevent light leaks.
• He noticed a faint glow on a piece of paper coated with barium platinocyanide about 3
feet away. He realized this fluorescence was not caused by light or electrons from the
tube.
• The First Radiograph: Roentgen concluded that a new, unknown type of ray was
being produced. He tested its properties by placing objects between the tube and the
fluorescent screen. When he placed his hand, he saw the outline of his bones. This led
him to create the first medical X-ray image on December 22, 1895, of his wife,
Bertha Roentgen's, hand. The image clearly showed the bones of her hand and her
wedding ring, solidifying the immense potential of this new technology for medicine.
• Roentgen published his findings and was awarded the first Nobel Prize for Physics in
1901.
Nature of X-rays
Electromagnetic Radiation: X-rays are a form of electromagnetic (EM) radiation, which is
the transport of energy through space via electric and magnetic fields. Other examples
include visible light, radio waves, and gamma rays.
Dual Nature: EM radiation, including X-rays, exhibits a dual nature: it can behave as both a
wave and a particle.
✓ Wave Concept: As a wave, EM radiation is described by its wavelength (λ) and
frequency (v). All EM waves travel at the speed of light (c) (c=λv).
✓ Particle Concept: As a particle, EM radiation is composed of discrete bundles of
energy called photons. The energy (E) of a photon is directly proportional to its
frequency and is calculated using Planck's constant (h) (E=hv).
Ionizing Radiation:X- X-rays are a type of ionizing radiation because their photons carry
enough energy (typically greater than 15 eV) to knock electrons out of atoms, which can be
used to form images and also has biological effects.
,Photon Energy–Wavelength Relationship
The energy (E) of an X-ray photon is inversely proportional to its wavelength (λ). This
means, as the energy of the X-ray increases, its wavelength decreases.
This relationship is expressed by the equation:
E(keV) = 12.4 / λ(Å)
E = photon energy in kiloelectron volts (keV).
λ = wavelength in angstroms (Å).
12.4 = constant (Planck's constant (h) x speed of light (c), with units converted from
standard physics to kiloelectron volts (keV) and angstroms (Å).
Significance: This fundamental relationship is crucial for understanding the penetrating
power of X-rays. Higher-energy photons (with shorter wavelengths) can pass through denser
materials more easily, making them ideal for imaging bones and other thick body parts.
Conversely, lower-energy photons (with longer wavelengths) are more easily absorbed and
are used for imaging softer tissues, such as in mammography.
Radiation Units:
Kiloelectron Volt (keV): A unit of energy for photons; 1 keV=1000 eV.
Angstrom (Å): A unit of length used for very short wavelengths; 1 A˚=10−10 m.
Roentgen (R): A unit of radiation exposure in air.
Gray (Gy): The SI unit for absorbed radiation dose, which measures the energy deposited in
a material; 1 Gy=1 J/kg.
Sievert (Sv): The SI unit for dose equivalent, which accounts for the biological effect of
different types of radiation on tissue.
, APPLICATIONS OF X-RAYS
Medical Applications
• Diagnostic Imaging: This is the most common use of X-rays in medicine.
❖ Radiography (Plain X-rays): Used to see dense structures like bones to detect
fractures, as well as tumors and foreign objects.
❖ Computed Tomography (CT scan): Uses multiple X-rays to create detailed,
cross-sectional images of the body, which is excellent for visualizing soft
tissues and diagnosing complex conditions.
❖ Mammography: A specific type of low-dose X-ray used for breast cancer
screening.
❖ Fluoroscopy: Provides real-time, moving X-ray images, used in procedures like
barium studies and angiography to see internal organs in motion.
• Therapeutic Applications: High-energy X-rays are used in radiation therapy to kill
cancer cells and shrink tumors.
Industrial Applications
• Non-Destructive Testing (NDT): This involves using X-rays to inspect materials and
components for flaws without damaging them. It's used for checking welds, castings,
and pipelines for cracks or corrosion.
• Material Analysis: X-ray techniques are used to analyze the composition and
structure of materials.
o X-ray Diffraction (XRD): Analyzes the crystal structure of materials.
o X-ray Fluorescence (XRF): Determines the elemental composition of
materials.
• Food Inspection: Detects foreign objects (metal, glass) in food products.
• Art and Archaeology: Examines internal structures of artifacts and paintings
Security Applications
• Baggage Scanners: Screen luggage for weapons, explosives, and contraband.
• Body Scanners: Used for personal security checks.
• Mail Scanners: Inspect packages for suspicious contents.
• Cargo Inspection: Screens large containers for illicit materials.
