27 Questions
What happens when a photon with energy exceeding 1.02 MeV interacts with the electric field of the nucleus?
It imparts any excess energy to the electrons as kinetic energy
At what energy level does photodisintegration of the nucleus occur?
Above 10 MeV
What is the relationship between contrast and dose in diagnostic imaging?
Dose increases as kVp decreases
What is the process by which electrons are boiled off at the cathode?
Electron emission
What is the typical size of the bombarded spot on the anode in x-ray production?
1mm^2
What is the function of the induction motor of the anode in x-ray tube operations?
To rotate the anode disk to provide a larger total area for bombardment
What is the main factor for controlling the average energy of the x-ray beam?
kVp
What does the mA setting control in x-ray tube operations?
The quantity of current flow from cathode to anode per unit time
What is the typical range for the anode angle in diagnostic x-ray tubes?
7-20 degrees
What is the function of the AEC (automatic exposure control) in x-ray tube operations?
To stop the exposure as soon as a predetermined quantity of remnant beam has reached the image receptor
What is the conventional unit for the quantity of electrical charge liberated by ionizing electromagnetic energy per unit mass of air?
Roentgen
What is the main factor for controlling the total quantity of radiation produced during an exposure?
mAs setting
What is the process by which electrons are accepted by the anode in x-ray tube operations?
Electron absorption
What is the typical speed of rotation for the induction motor in x-ray tube operations?
3000 rotations/min
What does the effective focal spot (EFS) represent in x-ray tube operations?
The length and width of the focal spot as projected down by the central ray in the x-ray field
What is the material of the envelope of the x-ray tube?
Pyrex glass or metal
What is the filament made of in the x-ray tube?
Thoriated tungsten
What is the purpose of the focusing cup in the x-ray tube?
To shape the electron beam
What is the material of the target in the x-ray tube for x-ray production?
Tungsten 74 and rhenium
What is the material of the stationary anode in the x-ray tube?
Tungsten in a copper block
What is the purpose of the rotating anode disc in the x-ray tube?
Increases heat loading ability
What is the material of the anode stem in the x-ray tube?
Molybdenum
What is the material of the rotor in the x-ray tube?
Copper and iron
What is the material of the stator in the x-ray tube?
Electromagnets
What does the Automatic Exposure Control (AEC) measure in the x-ray tube?
Certain parts of the remnant beam
What are some types of radiation production discussed in the text?
Characteristic radiation, bremsstrahlung production, and the emission spectrum
What interactions are focused on in the text?
Coherent, Thompson and Rayleigh scattering, Compton scattering, and the photoelectric effect
Study Notes
X-ray Tube Components and Operation
- The x-ray tube has an envelope made of pyrex glass or metal to maintain vacuum and withstand high heat levels.
- The filament, made of thoriated tungsten, is part of the cathode and produces electrons via thermionic emission.
- The focusing cup, made of metal, surrounds the filament and shapes the electron beam to keep electrons together.
- The target, made of tungsten 74 and rhenium in most modalities, is struck by the electron beam for x-ray production.
- The stationary anode, made of tungsten in a copper block, is suitable for low volume environments and conducts heat away from the tungsten target.
- The rotating anode disc, made of tungsten and sometimes layered with graphite, increases heat loading ability.
- The anode stem, made of molybdenum, connects the anode disc to the rotor assembly in rotating designs.
- The rotor, made of copper and iron, rotates the anode disc as part of the induction motor inside the tube.
- The stator, made of electromagnets, powers the induction motor outside the tube around the rotor.
- The Automatic Exposure Control (AEC) measures certain parts of the remnant beam and allows technologists to select ionization chambers and energy levels.
- Different types of radiation production including characteristic radiation, bremsstrahlung production, and the emission spectrum are discussed.
- The text also covers contrast, scatter radiation, grid construction parameters, and attenuation, with a focus on interactions like coherent, Thompson and Rayleigh scattering, Compton scattering, and the photoelectric effect.
Test your knowledge of x-ray tube components and operation with this quiz. Explore topics such as filament, focusing cup, target, anode, rotor, AEC, radiation production, and scatter radiation. Perfect for radiology students and professionals looking to brush up on their understanding of x-ray technology.
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