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Questions and Answers
In an atom, the electrons in the outermost shell are tightly bound to the nucleus.
In an atom, the electrons in the outermost shell are tightly bound to the nucleus.
False
In the diagnostic energy range, x-ray photons interact with the orbital electrons as well as with the nucleus.
In the diagnostic energy range, x-ray photons interact with the orbital electrons as well as with the nucleus.
False
The most important factor in x-ray interaction with a tissue is its molecular structure.
The most important factor in x-ray interaction with a tissue is its molecular structure.
False
The energy value of electronic shells is solely determined by the molecular structure of the atom.
The energy value of electronic shells is solely determined by the molecular structure of the atom.
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Electrons in the K-shell are more tightly bound in elements of high atomic number than in elements of low atomic number.
Electrons in the K-shell are more tightly bound in elements of high atomic number than in elements of low atomic number.
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The energy debt of inner shell electrons is greatest when they are close to the nucleus in an element with a low atomic number.
The energy debt of inner shell electrons is greatest when they are close to the nucleus in an element with a low atomic number.
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The heart of an X-ray machine consists of a cathode and an anode.
The heart of an X-ray machine consists of a cathode and an anode.
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The material for the anode is selected based on its ability to convert electronic energy into x-radiation and to dissipate the heat created in the process.
The material for the anode is selected based on its ability to convert electronic energy into x-radiation and to dissipate the heat created in the process.
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Tungsten is used as the material for the filament in the cathode of X-ray tubes.
Tungsten is used as the material for the filament in the cathode of X-ray tubes.
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The dimensions of the focal spot on the surface of the anode are determined by the dimensions of the electron beam arriving from the anode.
The dimensions of the focal spot on the surface of the anode are determined by the dimensions of the electron beam arriving from the anode.
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Most x-ray tubes have two focal spot sizes (small and large), which can be selected by the operator according to the imaging procedure.
Most x-ray tubes have two focal spot sizes (small and large), which can be selected by the operator according to the imaging procedure.
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The anode rotation during the x-ray production process is primarily for adjusting the focal spot size.
The anode rotation during the x-ray production process is primarily for adjusting the focal spot size.
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X-ray tubes with small focal spots produce more blurring and less visibility of detail compared to large focal spots.
X-ray tubes with small focal spots produce more blurring and less visibility of detail compared to large focal spots.
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The density of the target material in the anode does not matter for electron interaction and x-ray generation.
The density of the target material in the anode does not matter for electron interaction and x-ray generation.
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The tungsten-rhenium alloy has been used as the target material on some anodes for x-ray tubes.
The tungsten-rhenium alloy has been used as the target material on some anodes for x-ray tubes.
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The target material must be of high atomic mass for electron interaction and x-ray generation.
The target material must be of high atomic mass for electron interaction and x-ray generation.
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Characteristic x-rays are produced by which process?
Characteristic x-rays are produced by which process?
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What is the probability of bremsstrahlung radiation dependent on?
What is the probability of bremsstrahlung radiation dependent on?
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What is the average energy of the bremsstrahlung x-rays?
What is the average energy of the bremsstrahlung x-rays?
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What is the relationship between wavelength, frequency, and the velocity of light for electromagnetic radiation?
What is the relationship between wavelength, frequency, and the velocity of light for electromagnetic radiation?
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What happens in coherent scattering?
What happens in coherent scattering?
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What percentage of photoelectric reactions occur in compact bone for radiation with an energy of 20 Kev?
What percentage of photoelectric reactions occur in compact bone for radiation with an energy of 20 Kev?
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What controls the number of X-rays that the tube is generating?
What controls the number of X-rays that the tube is generating?
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What is used to expel the electrons from the cathode in a process known as thermionic emission?
What is used to expel the electrons from the cathode in a process known as thermionic emission?
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What is the primary function of the envelope in the x-ray tube?
What is the primary function of the envelope in the x-ray tube?
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What does the x-ray tube housing do in addition to enclosing and supporting the other components?
What does the x-ray tube housing do in addition to enclosing and supporting the other components?
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What device is used to minimize the field of view and avoid unnecessary exposure using lead plates?
What device is used to minimize the field of view and avoid unnecessary exposure using lead plates?
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What is used to eliminate scattered light in an x-ray machine?
What is used to eliminate scattered light in an x-ray machine?
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What happens to the X-ray film when X-rays interact with it?
What happens to the X-ray film when X-rays interact with it?
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What are some examples of medical applications of X-ray?
What are some examples of medical applications of X-ray?
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How are X-rays produced in an x-ray tube?
How are X-rays produced in an x-ray tube?
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What makes up approximately 80% of the x-ray beam keV?
What makes up approximately 80% of the x-ray beam keV?
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Scatter radiation is composed of photons of higher energy than the photons that produced them.
Scatter radiation is composed of photons of higher energy than the photons that produced them.
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At low energies, Compton scattering is more common than Photoelectric reaction.
At low energies, Compton scattering is more common than Photoelectric reaction.
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A small x-ray field irradiates more tissue and generates more scattered photons.
A small x-ray field irradiates more tissue and generates more scattered photons.
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Scattered photons contribute to film blackness (film fog).
Scattered photons contribute to film blackness (film fog).
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Increasing the patient dose is a benefit of reducing scatter radiation.
Increasing the patient dose is a benefit of reducing scatter radiation.
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Using ray filters and X-ray beam restrictors is a technique for promoting scatter radiation.
Using ray filters and X-ray beam restrictors is a technique for promoting scatter radiation.
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The contrast improvement can be achieved by reducing X-ray effects of scatter radiation.
The contrast improvement can be achieved by reducing X-ray effects of scatter radiation.
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Good radiography requires minimal contrast difference between different tissues.
Good radiography requires minimal contrast difference between different tissues.
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Bone attenuates radiation less than air in the lungs.
Bone attenuates radiation less than air in the lungs.
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Photoelectric reaction is usually seen in the contrast agents due to their low atomic numbers.
Photoelectric reaction is usually seen in the contrast agents due to their low atomic numbers.
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After the electron has been ejected, the atom is left with avoid in the K shell.
After the electron has been ejected, the atom is left with avoid in the K shell.
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The amount of energy released in the form of an x-ray photon as the electron drops into the K shell is characteristic of each element, hence the radiation produced is called _______ radiation.
The amount of energy released in the form of an x-ray photon as the electron drops into the K shell is characteristic of each element, hence the radiation produced is called _______ radiation.
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The probability of a photoelectric reaction increases sharply as the ________ increases.
The probability of a photoelectric reaction increases sharply as the ________ increases.
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The Compton effect occurs when the incident x-ray photon with relatively high energy ejects an electron from an atom and a _______ x-ray photon is scattered from the atom.
The Compton effect occurs when the incident x-ray photon with relatively high energy ejects an electron from an atom and a _______ x-ray photon is scattered from the atom.
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The amount of energy a photon transmits in a Compton effect reaction depends on its initial energy and its ________.
The amount of energy a photon transmits in a Compton effect reaction depends on its initial energy and its ________.
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The number of Compton reactions is independent of the atomic number of the absorber but depends on the ________ of electrons per gram of the absorber.
The number of Compton reactions is independent of the atomic number of the absorber but depends on the ________ of electrons per gram of the absorber.
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The photoelectron can cause ionizations along its track, and X-ray emission can occur when the vacancy left by the photoelectron is filled by an electron from an ________ shell of the atom.
The photoelectron can cause ionizations along its track, and X-ray emission can occur when the vacancy left by the photoelectron is filled by an electron from an ________ shell of the atom.
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Almost all the scatter radiation encountered in diagnostic radiology comes from ________ scattering.
Almost all the scatter radiation encountered in diagnostic radiology comes from ________ scattering.
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Pair production occurs when a high energy photon interacts with the nucleus of an atom and its energy is converted into matter in the form of two particles, an electron and a ________.
Pair production occurs when a high energy photon interacts with the nucleus of an atom and its energy is converted into matter in the form of two particles, an electron and a ________.
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Pair production interaction cannot take place with photon energy less than ________ MeV.
Pair production interaction cannot take place with photon energy less than ________ MeV.
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Photodisintegration occurs when a photon with extremely high energy interacts directly with the ________ of an atom.
Photodisintegration occurs when a photon with extremely high energy interacts directly with the ________ of an atom.
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Coherent scattering plays a minor role throughout the diagnostic energy range and accounts for about ________% of interactions.
Coherent scattering plays a minor role throughout the diagnostic energy range and accounts for about ________% of interactions.
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Study Notes
- Atom structure: An atom consists of a nucleus, which contains protons and neutrons, and electrons in outer shells. The electrons are arranged in shells, with the K shell having 2 electrons and the L shell having 8.
- X-ray interaction with atom: X-rays interact with the orbital electrons in diagnostic energy range, not molecular bonding energies. Atomic make-up of a tissue is the key factor, not molecular structure.
- X-ray definition: X-rays are produced through electron shell interactions, with wavelengths between 10-10 and 10-12 m.
- X-ray emission: X-ray radiation is emitted as bremsstrahlung (about 80%) and characteristic radiation. Energy and amount are determined by voltage (kVp) and current (mA).
- X-ray device: X-ray machine consists of an X-ray tube, operating console, high frequency generator, collimator, grid, and X-ray film.
- X-ray tube: Anode and cathode are the main components. Cathode is the negative terminal with a filament made from tungsten, which provides electrons for acceleration to the anode. The anode is made of high-melting-point materials like tungsten or molybdenum, which can withstand high temperatures during x-ray production.
- Focal spot: A small area on the anode surface where radiation is produced. X-ray tubes are designed with specific focal spot sizes, ranging from 0.1 mm to 2 mm, to balance blurring and heat dissipation.
- Cathode: Negative terminal of the tube assembly with a filament made from tungsten. The filament provides electrons for acceleration to the anode and can be heated for thermionic emission.
- Envelope: The anode and cathode are enclosed in an airtight enclosure to provide support, electrical insulation, and maintain vacuum.
- X-ray circuit: The energy to produce x-radiation is supplied by an electrical circuit.
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