[Module 7] Ionizing Radiation and Life
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79 Terms
Who discovered radioactivity and how?
Sir Henry Becquerel discovered radioactivity from uranium salts on photographic plates
What are photographic plates?
These are compounds that form structures changed by exposure to light.
What accidental discovery did Sir Rothschild make?
He accidentally generated an X-ray image of his wife's hands after noticing that barium platinum cyanide emitted flickering lights near a Crookes tube.
What is a Crookes tube?
A Crookes tube is a partially evacuated glass enclosure with an anode, cathode, and a high voltage source, typically 10 kilovolts.
What happens inside a Crookes tube?
Accelerated charged particles create electromagnetic waves, causing the gases inside to light up in various colors.
What did J.J. Thomson discover?
J.J. Thomson discovered that electrons are responsible for the phenomenon observed in Crookes tubes, leading to the generation of X-rays.
What is a Geiger-Muller tube?
A device that detects ionizing radiation by producing a charge in a sparse space within the tube.
How does the Geiger-Muller tube work? (Steps)
The Geiger-Muller tube consists of an anode (central wire) and a cathode (outer cylinder) with a high voltage applied.
Ionizing radiation enters the tube and produces a charge trap in a sparse space within the gas.
High voltage creates an electric field between anode and cathode, causing ions and electrons to accelerate in opposite directions.
As the accelerated particles move, they collide with other gas atoms.
Collisions cause a cascading effect, leading to further ionization and a measurable current loss between the anode and cathode.
Resulting ionization event generates a signal that is recorded to indicate the presence of radiation.
How does the Photon Multiplier tube work? (Steps)
Photons enter the system at the photocathode.
Photons pass into an electron-focusing grid.
EFG allows the photons to accelerate, then it causes knockouts of electrons within the system.
Knocked-out electrons amplify the signal as they move through dynodes.
Amplification continues until a current flows due to the acceleration caused by knocking out electrons.
Subsequent reactions from knocking out electrons produce a signal that can be used to detect the radiation in the system.
What are dosimeters used for?
Dosimeters are used to measure exposure to radiation.
What type of dosimeters use passive electroscopes?
Film-badged dosimeters use passive electroscopes.
What is an example of a dosimeter setup?
A sealed chamber with charged polyethylene balls.
What are scintillation detectors?
Scintillation detectors are a combination of a photocell and a counter.
How do scintillation detectors work? (Steps)
A radioactive molecule inside the tube produces radiation.
The radiation causes a scintillant molecule inside a sample to emit electrons.
The emitted electrons are collected by the photocell.
The photocell responds to the radiation nearby and is connected to a photosensitive semiconductor or a photon multiplier.
The photocell has its signal amplified.
The amplified signal is recorded by a counter.
This process produces a signal that can be used to detect the radiation in the system.
What is radioactivity?
The number of radioactive disintegrations per minute.
What is 1 Curie equivalent to?
One gram of radium, equal to 3.7 x 10^10 disintegrations per second.
What is 1 Becquerel?
One disintegration per second.
What does the formula for radioactivity include?
The formula includes variables for the derivative (rate of change), number of particles (N), and time (T).
How is the number of particles related to time?
The number of particles is proportional to the change in time.
What are the 5 types of Radiation?
Alpha Rays
Beta Rays
Gamma Rays
X-rays
Neutron Rays
What are alpha rays?
Alpha rays cannot penetrate paper, are more naturally occurring, and have two positive charges, leaving a dense trail of ionization.
What are beta rays?
Beta rays can penetrate paper but not aluminum, are more naturally occurring, can kick out other electrons, and produce gamma rays as Bremsstrahlung.
What are gamma rays?
Gamma rays can penetrate paper and aluminum but cannot penetrate lead, can be produced by radioactive materials, penetrate deeply, and leave a shorter ionization trail than alpha rays.
What are X-rays?
X-rays can penetrate paper and aluminum but cannot penetrate lead, can be produced by radioactive materials, and are associated with Bremsstrahlung.
What are neutron rays?
Neutron rays can penetrate paper, aluminum, thick lead, but not water, require a special procedure to be produced, and are more commonly seen in outer space.
How is ultraviolet (UV) light produced?
UV light is produced through high-energy reactions, such as atomic transitions in atoms (e.g., mercury) and heating gases to temperatures of 4000 degrees Celsius.
Where can UV light be found?
UV light is produced by hot bodies like the sun and in high-energy reactors, not only from outer space.
What is an example of a man-made UV light?
Man-made UV is produced from carbon arcs used in welding, where two metal-coated carbon rods touch together, allowing a large current to pass through.
What happens when the current vaporizes carbon in welding?
The vaporized carbon becomes hot enough to emit a significant fraction of its thermal radiation in the visible part of the electromagnetic spectrum, including UV.
How do black lights produce UV light?
Black lights produce UV in the UV-A range by passing a current through mercury vapor in an inert gas within a quartz tube.
Why is quartz used in black lights?
The quartz tube allows UV-A to pass through, unlike ordinary glass.
What happens when the current passes through mercury vapor in black lights?
This reaction is enough to produce UV rays as electrons collide and excite the gas atoms, resulting in UV emission.
What is a primary danger of UV radiation?
The formation of thymine dimers, also known as pyrimidine dimers.
How does UV radiation contribute to the formation of thymine dimers?
UV radiation produces free radicals, which lead to the generation of thymine dimers in DNA.
Why are thymine dimers problematic for DNA replication?
Thymine dimers, when bonded together, are not recognized by the DNA replication machinery.
What can happen to thymine dimers in the body?
The body has mechanisms to repair thymine dimers, but if the body is in poor condition or if there are too many dimers, some may go unrepaired.
What can result from the replication of unrepaired thymine dimers?
The replication of these dimers can cause frameshift mutations.
Why are frameshift mutations dangerous?
They can cause a loss of track of the protein that is supposed to be produced, leading to potential dysfunction.
In which areas is UVC frequently used?
UVC is frequently used in food sterilization, water purification, air purification, and in biosafety cabinets.
How does sterilization occur when UVC hits the air?
Sterilization occurs due to the production of ozone when UVC radiation interacts with the air.
What is one biological application of UV?
Deep UV excitation fluorescence microscopy, which allows for rapid diagnosis compared to conventional histopathology.
What advantage does deep UV excitation fluorescence microscopy provide?
It enables clear discrimination of nucleoplasm, nucleus, and cytoplasm through a fluorescence staining protocol.
What are some other applications of UVC besides biological applications? (6)
Other applications include:
disinfection
forensic analysis
protein analysis
cell imaging
polymer curing
light therapy in medicine
Who discovered X-rays and how?
X-rays were discovered by Wilhelm Röntgen when he developed a photographic plate that had never been exposed to light, near a high voltage vacuum tube.
What type of wave are X-rays classified as?
X-rays are classified as electromagnetic waves.
What misconception about X-rays existed in the early 1950s?
Many believed X-rays were particles and used them in various applications, including cathode ray tubes in televisions and in shops for fitting clothes and shoes.
What unusual use of X-rays contributed to increased cancer rates?
Phosphor containing radiation X-rays was used in art, where it was often licked, leading to increased cancer rates.
Who helped clarify the nature of X-rays as electromagnetic waves?
Max von Laue, William Bragg, and Lawrence Bragg contributed to the understanding that X-rays are electromagnetic waves and can exhibit diffraction.
How did researchers demonstrate the properties of X-rays?
They showed that X-rays can be diffracted in salt crystals.
Medical Practices
What are the primary modern applications of X-rays?
How are X-rays produced?
X-rays are produced by electron transitions in elements such as copper, gallium, and molybdenum.
What is Bremsstrahlung?
Bremsstrahlung, or "breaking radiation," refers to the radiation emitted when electrons are deflected by the nucleus of heavy metals during high-energy collisions.
How are X-rays produced via Bremsstrahlung? (Short Steps)
High kinetic energy electrons are accelerated from the cathode to the anode.
During collisions with tungsten, some electrons bend around the tungsten nucleus due to Coulomb attraction.
This bending produces radiation known as Bremsstrahlung, or "breaking radiation."
How are X-rays produced via Bremsstrahlung? (Long Steps) I DONT UNDERSTAND THIS PLS EDIT IF NEEDED
Accelerate a stream of electrons to several hundred kilovolts.
High-energy electrons collide with a heavy target material, usually tungsten due to its effective electron interactions.
This collision generates Bremsstrahlung photons (radiation).
The radiation has a continuous spectrum of energies, ranging from a few keV to the maximum energy of the electron beam.
Inherent filtration of the X-ray tube is calculated based on:
Electron penetration into the target.
Type of vacuum window present.
Bremsstrahlung photons are attenuated as they pass through about 50 microns of tungsten.
The beam is further reduced by the aluminum or beryllium vacuum window.
Low-energy photons (1 keV to 15 keV) are eliminated, and there’s significant reduction in photons from 15 keV to 50 keV.
The spectrum is further modified by additional filters to enhance high-energy X-ray output.
What is the energy range of the X-ray radiation produced?
X-ray radiation produced has a continuous spectrum of energies, typically ranging from a few keV to the maximum energy of the electron beam.
Why is tungsten commonly used as a target material in X-ray tubes?
Tungsten is used because the wave functions of its bound electrons are required for effective X-ray production during electron collisions.
What is the significance of X-ray tubes in producing X-rays?
X-ray tubes produce X-ray photons, which is why X-rays can be generated via the Bremsstrahlung process during electron collisions with heavy materials like tungsten.
What is inherent filtration in an X-ray tube?
Inherent filtration refers to the filtration of X-rays that occurs based on:
The amount of electron penetration into the target surface.
The types of vacuum window present in the tube.
What is a synchrotron?
A synchrotron is a device used to accelerate charged particles in a vacuum along a cyclic path. They can vary in size, spanning from a room to a building, depending on the desired resolution.
How are X-rays utilized in a synchrotron?
X-rays are accelerated around the synchrotron and then it hits a certain material that you want to characterize. Ex. DNA was characterized to X-ray diffraction.
What role do magnetic fields play in synchrotrons?
Magnetic fields are used to detect the motion of charged particles and to generate diffraction patterns.
What is X-ray diffraction?
X-ray diffraction is a technique used to characterize the structures of materials, such as proteins and DNA. When high-energy X-rays strike a material (e.g., DNA or protein), they generate diffraction patterns. Its patterns are recorded through photographs.
What can be reconstructed from the diffraction pattern of DNA?
The 3D structure of DNA can be reconstructed from its diffraction pattern photograph.
What is the primary medical use of X-rays?
X-rays are used to visualize bones and internal structures in the body.
What distinguishes X-rays from visible light?
X-rays are a form of electromagnetic radiation with higher energy than visible light, allowing them to pass through most objects, including the human body.
What is a CT scan?
A CT scan, or computer-assisted tomography scan, is a detailed imaging technique that creates 3D images of the body, functioning as a more advanced version of traditional X-rays.
How does electron density affect X-ray imaging?
The absorption and scattering of X-rays depend on the electron density of body organs, tissues, and bones, which influences the resulting image quality.
How can resolution be improved in CT scans?
Heavy elements may be administered to certain organs to enhance the resolution of images for specific areas.
What is the process by which a CT scan creates a 3D image?
A CT scan works by rotating the X-ray source around the body to capture multiple images from different angles, which are then processed to create a 3D representation.
How are gamma rays naturally produced?
Gamma rays are made naturally by radioactive materials and cosmic rays hitting atoms in the upper atmosphere.
How can gamma rays be artificially produced?
Gamma rays can be produced by humans in particle accelerators through:
Synchrotron radiation
Scattering of high-energy nuclear particles
Nuclear reactors
Particle-antiparticle annihilation
What is a PET scan?
A Positron Emission Tomography (PET) scan is a medical imaging technique used to discover information about body functions, such as specific metabolic processes.
How are positrons generated in PET scans?
Positrons are generated from nuclear decay in isotopes and are the antimatter counterparts of electrons.
What happens when positrons collide with electrons in PET scans?
When positrons collide with local electrons, they undergo annihilation, producing two gamma rays with an energy of 0.511 MeV that radiate in opposite directions.
How do gamma rays assist in PET scans?
Gamma rays radiate through the body, providing information about body functions as they heat cells, prompting a response that is visualized in the scan.
What are some applications of PET scans?
Tracer studies
Mapping brain physiology
Detection of cancer
Heart studies
Iron and sulfur tracing
Monitoring thyroid uptake
What are the long-term effects of radiation on cells?
Long-term radiation exposure can affect DNA, leading to complications such as cancer, increased malignancy with higher exposure, and immunosuppression.
What is radiation therapy?
Radiation therapy uses radiation to kill cancer cells, typically using a linear accelerator to focus radiation on tumor sites.
What types of radiation are used in radiation therapy?
X-rays or proton radiation.