Physics of X-ray Production

X-rays are produced when highly energetic electrons interact with matter, converting their kinetic energy into electromagnetic radiation.

The energy of an X-ray photon is inversely proportional to its wavelength, described by the equation E = h c / λ.

The main components are a cathode (source of electrons), an evacuated glass envelope, a high positive potential anode, and the target.

<p>A higher atomic number increases the intensity of the X-ray beam produced, with tungsten (Z = 74) being a common anode material.</p> Signup and view all the answers

<p>Increasing the tube current (mAs) increases the number of electrons, which in turn increases the number of produced X-ray photons.</p> Signup and view all the answers

<p>The anode material must have a high melting point to withstand the intense heat generated during electron impact.</p> Signup and view all the answers

<p>Approximately 1% of the accelerated electrons' energy is converted into X-ray photons.</p> Signup and view all the answers

<p>Increasing kilovoltage (kV) accelerates electrons to higher speeds, resulting in higher energy X-ray photons.</p> Signup and view all the answers

<p>High Z elements have a greater probability of interacting with X-ray photons due to their larger atomic number and density.</p> Signup and view all the answers

<p>At 30 keV, bone absorbs X-rays about 8 times better than tissue due to the photoelectric effect.</p> Signup and view all the answers

<p>The electron receives part of the photon energy, while the remaining energy is transferred to a Compton photon.</p> Signup and view all the answers

<p>Compton Effect interactions are more probable than photoelectric interactions at energies ≥ 30 keV.</p> Signup and view all the answers

<p>The minimum energy required for pair production is 1.02 MeV, leading to the creation of an electron and a positron from a high-energy photon.</p> Signup and view all the answers

<p>Barium and iodine compounds are used as contrast agents due to their high atomic numbers, enhancing the photoelectric effect.</p> Signup and view all the answers

<p>They are injected or ingested to enhance the visibility of specific organs or blood vessels during imaging.</p> Signup and view all the answers

<p>The basic components required are an X-ray source and an image receptor.</p> Signup and view all the answers

<p>1 keV.</p> Signup and view all the answers

<p>Mammography uses 25 to 50 kVp, while chest x-ray studies use approximately 350 kVp.</p> Signup and view all the answers

<p>99% of the power appears as heat, which can damage the anodes.</p> Signup and view all the answers

<p>The linear attenuation coefficient (μ) measures the probability of photon interaction (absorption or scattering) per unit length traveled in a specified material.</p> Signup and view all the answers

<p>Half-value thickness (HVT) is the thickness of a material that reduces the intensity of radiation to half of its initial value.</p> Signup and view all the answers

<p>In the photoelectric effect, an incoming x-ray photon transfers all its energy to an electron, overcoming binding energy and causing ionization of surrounding atoms.</p> Signup and view all the answers

<p>I = I₀ e^{-μx}.</p> Signup and view all the answers

<ol> <li>Energy of x-rays, 2. Atomic number (Z), 3. Density (ρ) of the material.</li> </ol> Signup and view all the answers

<p>The two types are Bremsstrahlung Spectrum and Characteristic X-ray. Bremsstrahlung involves the deceleration of electrons near atomic nuclei while Characteristic X-ray involves an electron knocking out an inner-shell electron and filling the vacancy with emission of radiation specific to the atom.</p> Signup and view all the answers

<p>Smaller focal spots produce less image blurring but concentrate heat on a small area. Larger focal spots allow for greater heat distribution but may result in more blurring in the image.</p> Signup and view all the answers

<p>The line-focus principle allows for increasing the area struck by electrons on the anode while reducing image blurring by angling the anode by 10° to 20°. This technique helps balance heat management and image quality.</p> Signup and view all the answers

<p>A higher atomic number results in a greater acceleration of electrons towards the nucleus, leading to increased bremsstrahlung radiation. This is because more protons in the nucleus create a stronger positive electric field.</p> Signup and view all the answers

<p>The temperature of the filament determines the number of electrons that are accelerated toward the anode. A higher temperature increases the electron emission and thereby the X-ray production.</p> Signup and view all the answers

<p>Diagnostic X-rays typically have energies ranging from 15 to 150 keV, while visible light photons have energies of only 2 to 4 eV. This significant difference in energy levels allows X-rays to penetrate matter effectively.</p> Signup and view all the answers

<p>When a fast electron strikes a K-electron, it knocks it out of its orbit, creating a vacancy. An electron from an outer shell then falls into this vacancy, emitting a characteristic K X-ray photon.</p> Signup and view all the answers

<p>The kV peak determines the maximum energy of the X-ray photons produced, as it influences the speed at which electrons are accelerated toward the anode. Higher kVp values result in more energetic X-rays with greater penetrating ability.</p> Signup and view all the answers

<p>Grids are used to reduce scatter radiation reaching the film and improve image quality.</p> Signup and view all the answers

<p>Thicker body parts, like the abdomen or pelvis, produce more scatter radiation.</p> Signup and view all the answers

<p>Grids can increase the patient's radiation dose by absorbing some primary beam photons.</p> Signup and view all the answers

<p>Filtration removes low-energy X-rays that do not penetrate the body effectively, reducing patient radiation dose.</p> Signup and view all the answers

<p>EAP is the product of radiation exposure in roentgens and the area in square centimeters.</p> Signup and view all the answers

<p>Direct interactions involve radiation energy transferring to DNA directly, while indirect interactions involve forming free radicals in water molecules that damage DNA.</p> Signup and view all the answers

<p>The unit for measuring X-ray radiation exposure is the roentgen (R).</p> Signup and view all the answers

<p>Low-energy radiation can increase the patient radiation dose without improving image quality.</p> Signup and view all the answers

<p>Deterministic effects and stochastic effects.</p> Signup and view all the answers

<p>At least 5 years, possibly reaching 10 or 20 years.</p> Signup and view all the answers

<p>Fluoroscopy is a real-time X-ray imaging technique used for procedures like catheter positioning and visualizing contrast agents.</p> Signup and view all the answers

<p>CT scans use X-rays passed through the body from multiple angles, detected by a detector array, and synthesized into tomographic images.</p> Signup and view all the answers

<p>MRI utilizes the magnetic resonance properties of protons in hydrogen nuclei of water molecules in the body.</p> Signup and view all the answers

<p>CT provides three-dimensional slices of the body, eliminating superposition of anatomical structures.</p> Signup and view all the answers

<p>Deterministic effects are caused by high radiation doses.</p> Signup and view all the answers

<p>The rotation of the X-ray tube around the patient's body collects transmission projection data.</p> Signup and view all the answers

X-rays are a form of electromagnetic radiation (EMR) with very short wavelengths (1-0.1 angstroms) and high penetrating power. They are used in medical imaging and therapy.

X-ray production involves converting the kinetic energy of high-speed electrons into electromagnetic radiation. When electrons collide with matter, they release X-ray photons.

The energy carried by each X-ray photon is directly proportional to its frequency. Higher frequency means higher energy. This relationship is described by the equation E = hν.

The main components of an X-ray tube are a cathode (electron source), an evacuated space (for electron acceleration), a high positive potential (to accelerate electrons), and an anode (target for collision).

The cathode filament emits electrons, and the number of electrons is controlled by the tube current (mA) and exposure time (s). Increasing mAs results in more electrons and more X-ray photons.

The high voltage (kV) applied across the tube accelerates electrons, determining their energy. Higher kV results in higher electron speed and, therefore, higher energy X-ray photons.

The anode material should have a high melting point to withstand the heat generated by the collision of electrons. Tungsten is typically used as the anode material due to its high melting point (3400°C).

Anode material with a higher atomic number (Z) produces a more intense X-ray beam. For example, tungsten (Z = 74) is preferred because of its higher atomic number.

The area on an X-ray tube's target where electrons strike. A smaller focal spot reduces image blurring, but concentrates heat in a smaller area.

A technique used to reduce image blurring by angling the anode, allowing a larger focal spot without increasing the apparent size on the image.

A type of X-ray radiation produced when fast electrons are decelerated by the atomic nucleus within the target material. This results in the electron losing kinetic energy, which is released as an X-ray photon.

The energy of Bremsstrahlung radiation depends on the atomic number of the target material. Higher atomic numbers result in stronger interactions between electrons and the nucleus, leading to more intense radiation.

The energy of Bremsstrahlung radiation also depends on the voltage applied to accelerate the electrons. Higher voltage leads to faster electrons that penetrate deeper into the nucleus, resulting in higher energy X-rays.

A type of X-ray radiation produced when an electron dislodges a core K-shell electron from a target atom. When an electron from a higher shell fills the vacancy, a characteristic x-ray photon is emitted with an energy specific to the target element.

The temperature of the filament in an X-ray tube controls how many electrons are emitted. This determines the intensity of the X-ray beam.

The voltage applied to the X-ray tube determines the maximum energy of the X-ray photons produced. This is the peak voltage (kVp) and influences the penetrating ability of the X-rays.

The energy gained or lost by an electron when moving across a potential difference of 1000 volts. It is equal to 1.6 x 10^-9 ergs or 1.6 x 10^-16 joules.

The peak voltage applied across the X-ray tube during an X-ray exposure. It determines the maximum energy of the X-rays produced.

The reduction in intensity of an X-ray beam as it passes through matter due to absorption and scattering of photons.

The probability that an X-ray photon will interact (be absorbed or scattered) per unit length of travel through a specific material.

The thickness of a material that reduces the intensity of an X-ray beam to half its original value. It is inversely proportional to the linear attenuation coefficient.

An interaction where an X-ray photon transfers its energy to an electron bound within an atom, liberating the electron and potentially ionizing surrounding atoms.

A spectrum of energies up to a maximum value, rather than a single fixed energy.

The strength of the X-ray beam measured in watts, calculated by multiplying the electron current in amps by the voltage in volts.

The probability of the photoelectric effect occurring increases with the atomic number (Z) of an element. This means heavier elements, like those found in bone, are more likely to absorb X-rays via the photoelectric effect.

X-rays with lower energies are more likely to be absorbed by atoms through the photoelectric effect. This is because lower energy X-rays are more likely to be absorbed by the electrons in the atom.

Compton scattering occurs when an X-ray photon collides with a loosely bound outer shell electron, transferring some of its energy to the electron and changing direction. It is more likely to occur in materials with lower atomic numbers.

Compton scattering is more likely to occur in materials with low atomic numbers (Z) because the electrons are loosely bound and more easily interacted with by the X-ray photons.

Contrast agents, typically materials with high atomic numbers (Z), are used in medical imaging to enhance the visibility of specific organs or tissues. These agents increase localized X-ray absorption through the photoelectric effect, creating distinct contrasts in the images.

Barium and iodine compounds are commonly used as contrast agents in medical imaging due to their high atomic numbers (Z). They are used in different parts of the body to improve the visibility of organs and structures during X-ray examinations.

Pair production is a phenomenon that occurs when a high-energy photon interacts with the electric field of an atomic nucleus, creating an electron and a positron. It is less likely to occur at the energy levels typically used in diagnostic medical imaging.

In pair production, the high-energy photon disappears (its energy is absorbed) and creates two particles: an electron and a positron. The mass-energy of these particles is then released as two photons called annihilation radiation.

Motion during X-ray exposure leads to blurry images. This is because the moving subject causes the X-rays to hit the detector at different angles, resulting in a blurred image.

Scatter radiation is unwanted radiation that travels in different directions after interacting with the patient's body. It can degrade image quality by adding unwanted noise.

Grids are devices used in X-ray imaging to reduce scatter radiation. They consist of alternating lead and plastic strips that absorb the scattered radiation while allowing the primary X-ray beam to pass through.

Thicker body parts, like the abdomen or pelvis, produce more scatter radiation because X-rays interact more with the denser tissue.

X-ray beam filtration removes low-energy X-rays that contribute to patient dose without improving image quality.

The Roentgen (R) is the unit of exposure, measuring the ionizing ability of X-rays. It quantifies the electrical charge produced when X-rays ionize air.

The exposure-area product (EAP) considers the total exposure received by the patient based on both the exposure dose and the irradiated area.

Radiation risk refers to the potential damage caused by ionizing radiation to the body's tissues. This damage can result from direct interactions with DNA or indirect interactions via free radicals.

These effects happen immediately after exposure to high radiation doses, causing visible damage within days or even weeks.

These effects appear gradually over years due to low radiation doses, potentially leading to cancer development.

A continuous X-ray imaging technique that shows moving images in real-time, like an X-ray movie.

A medical imaging technique that uses X-rays and a computer to create cross-sectional images of the body.

A medical imaging technique that uses powerful magnets and radio waves to create detailed images of the body's organs and tissues.

The property of protons in water molecules within the body that allows them to absorb and release energy when exposed to a magnetic field and radio waves.

The process of using a series of X-rays taken from different angles to create a 3D image of the body.

The ability of CT imaging to show three-dimensional slices of the body, avoiding the overlap of different structures.