27 Questions
What is the process that occurs when a photon with energy exceeding 1.02 MeV interacts with the electric field of the nucleus?
Photon interacts with the nucleus, exciting it and causing it to emit a nuclear fragment
What happens when a high energy photon interacts with the nucleus at energies above 10 MeV?
Photon undergoes photodisintegration, causing the nucleus to emit a nucleon or other nuclear fragments
How does the difference in optical densities on the image, leading to different shades of grey, occur?
Photon undergoes differential absorption, causing differences in optical densities on the image
What is the process in which electrons are boiled off at the cathode?
Thermionic emission
What is the typical size of the bombarded spot on the anode?
1mm^2
What does EFS stand for in the context of x-ray tubes?
Effective Focal Spot
What causes the effective focal spot length to be smaller than the actual focal spot length?
Anode angle
What is the function of the induction motor of the anode?
To rotate the anode disk to provide a larger total area for bombardment
What are the main technical factors mentioned in Lecture 4?
kVp, mA, and mAs
What does the mA setting control in an x-ray tube?
The quantity of current flow from cathode to anode per unit time
What is the conventional unit for quantity of electrical charge liberated by ionizing electromagnetic energy per unit mass of air?
Roentgen
What is the goal of the AEC (Automatic Exposure Control) in an x-ray system?
To obtain consistent quantity of remnant beam radiation to the image receptor for a standard quality image
What does the kVp setting control in an x-ray tube?
The maximum energy of a photon in the beam
What is the process in which changing magnetic field in stator coils induces current and magnetic fields in the rotor of the induction motor?
Induction motor
What is the average energy of the beam controlled by?
kVp setting
What material is the x-ray tube envelop typically made of?
Pyrex glass
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?
Shapes the electron beam and keeps the electrons together
What is the typical material of the target in the x-ray tube?
Tungsten 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 material connects the anode disk to the rotor assembly in rotating designs?
Molybdenum
What is the material of the rotor in the x-ray tube?
Copper and iron
What powers the induction motor outside the tube around the rotor?
Electromagnets
What has limitations as only certain parts of the remnant beam are measured?
Automatic exposure control (AEC)
What does the emission spectrum graph plot?
Photon energy vs. the number of photons emitted
What affects contrast in x-ray images?
Scatter radiation
Study Notes
X-ray Tube Components and Operation
- The x-ray tube envelop is made of pyrex glass or metal, designed to maintain vacuum and withstand high levels of heat.
- The filament, made of thoriated tungsten, is part of the cathode, producing electrons via thermionic emission.
- The focusing cup, made of metal, shapes the electron beam and keeps the electrons together.
- The target, typically made of tungsten and rhenium, is part of the anode and is struck by the electron beam for x-ray production.
- The stationary anode, made up of tungsten in a copper block, is a simple design suitable for low volume environments.
- 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 disk to the rotor assembly in rotating designs.
- The rotor, made of copper and iron, rotates the anode disk and is 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) has limitations as only certain parts of the remnant beam are measured.
- The emission spectrum is a graph plotting photon energy vs. the number of photons emitted from the x-ray tube.
- Contrast in x-ray images is affected by scatter radiation, which increases with tissue thickness and decreases with better collimation.
Test your knowledge of x-ray tube components and operation with this quiz. From the filament and focusing cup to the anode and rotor, see how well you understand the key elements and functions of x-ray tubes.
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