X-Ray Tube and Components

The space charge effect limits the functional milliamperage ( mA) of the x-ray tube to approximately :

1,000 mA The space charge effect limits the x-ray to a maximum of about 1,000 mA. Beyond 1,000 mA, the negative charge of electrons in the space outside the filament prevents additional electrons from leaving the filament.

Which of the following situations will require the use of the large filament within a dual focus x-ray tube?

Abdominal imaging on a bariatric patient The large filament will be required when a large exposure technique is necessary , such as abdominal imaging on a bariatric patient . All other situations listed use a much lower technique and allow for use of the small filament .

The bearings of the induction motor assembly are designed to do which of the following?

Allow for low-friction rotation of the anode The bearings of the induction motor assembly are designed to allow for low -friction rotation of the anode. Their spherical design allows the anode to spin rapidly with minimal wear and tear.

What component of the x-ray tube is the source of x- rays?

Anode The anode is the source of x-rays within the x-ray tube. When high-energy electrons from the cathode collide with tungsten atoms within the anode, these interactions create -ray photons and heat. The specific interactions that create x-ray photons are called Bremsstrahlung radiation and characteristic radiation.

Which characteristics of tungsten metal make it an ideal material for the construction of a radiographic anode ? (Select all that apply)

Atomic number, Thermal conductivity and Melting point Tungsten's high atomic number, thermal conductivity, and high melting point make it an ideal material for the construction of a radiographic anode. The high atomic number (74) results in high-efficiency and high-energy x-ray production. Tungsten's high thermal conductivity results in rapid heat dissipation way from the focal spot. With a melting point of 3,400C Tungsten can withstand high heat without pitting or bubbling.

What component of the x-ray tube is the source of free electrons ?

Cathode The cathode is the source of free electrons within the x-ray tube. The cathode also called the filament -creates free electrons in response to a high current through a phenomenon called thermionic emission .

Thermionic emissions occur within the x -ray tube at the:

Cathode Thermionic emission occurs at the cathode when the filament is heated . Thermionic emission is the creation of free electrons in response to heat .

Which component of the x-ray tube diagram below represents the electromagnets of the induction motor assembly ?

Component (A) Component A, the stators, is the electromagnets of the induction motor assembly. These electromagnets are positioned outside of the tube envelope to avoid physical contact with the charged components of the x-ray tube.

Which component of the x-ray tube diagram represents the rotor portion of the induction motor assembly?

Component (B) Component (B) represents the rotor portion of the induction motor assembly . The rotor is a metal shaft attached to the anode disc. The rotor spins the anode when activated by the electromagnets (stator ) outside the tube envelope .

Which component of the x-ray tube diagram represents the actual site of x-ray photon emission?

Component (D) Component (D), the anode, is the actual site of x-ray emission within the x-ray tube. Electrons from the cathode collide with the anode and create both heat and x-ray photons .

Which component of the diagram represents the negatively charged portion of the x- ray tube assembly ?

Component G Component (G) is the cathode, which is the negatively charged portion of the x-ray tube. Free electrons created by thermionic emission are repelled from the negative charge of the cathode and attracted to the positive charge of the anode when a kilovoltage is applied to the tube.

Stationary anodes are most appropriate for which of the following x-ray systems ?

Dental imaging Stationary anodes are most appropriate for x-ray systems designated for small exposure techniques, such as dental imaging. Stationary anodes have a lower heat capacity compared to rotating anode and cannot tolerate the large technical factors required for imaging large patients and thick body parts.

What component of the x-ray tube is responsible for creating a vacuum around the photon-producing components?

Glass envelope The glass envelope creates a vacuum (an air-free space) around the anode and cathode within the x-ray tube. This ensures there is no matter that might disrupt the flow of electrons from cathode to anode, and protects the anode and cathode from corrosion.

What is the principal advantage of using an x-ray tube equipped with a rotating anode?

Increased heat capacity The principal advantage of a rotating anode is increased heat capacity. As the anode rotates, the heat created by electron interactions at the anode is spread out over a much larger surface area compared to a stationary anode. This increased heat capacity allows for larger exposure techniques.

Which three of the following imaging modalities use an x-ray tube? ( Select three)

Mammography, Fluoroscopy and Computed Tomography (CT) Mammography, fluoroscopy, and computed tomography all use x-ray tubes. These tubes are substantially similar in their function , design , and components.

Failure of the focusing cup within the x-ray tube will result in which of the following?

decreased spatial resolution Failure of the focusing cup will result in decreased spatial resolution. The purpose of the focusing cup is to compress the electron beam and ensure a tightly aligned x-ray beam . Without the focusing cup, the electron beam will diverge, and strike a larger area on the anode surface which will create a poorly aligned x-ray beam with lower spatial resolution.

The term space charge" within the x-ray tube refers to which of the following ?

free electrons The term "space charge" refers to the collection of free electrons surrounding the filament. These free electrons are created in the space surrounding the cathode through the process of thermionic emission. The electrons surround the filament until a kilovoltage is applied .

Which of the following is required for the induction of thermionic emission within the x- ray tube?

high current Thermionic emission occurs when the filament is supplied with a high current. The type of current (alternating or direct) is not a determining factor. A high current creates the high heat necessary to free electrons from their orbits within the tungsten atom.

What is the principal advantage of using the large filament within a dual focus x-ray tube?

increased heat capacity The principal advantage of using the large filament is increased heat capacity. The large filament spreads out the electron beam over a larger area on the anode. Distributing the heat over a larger area allows the x-ray tube to tolerate larger exposures without the risk of overheating the cathode or anode .

What is the principal advantage of using the small filament within a dual focus x-ray tube?

increased spatial resolution The principal advantage of using the small filament is increased spatial resolution . The small filament creates a smaller actual focal spot, a smaller effective focal spot, and a more precisely aligned x-ray beam. The primary disadvantage of using the small filament is decreased heat capacity

In order to adequately compress the electron stream with the x-ray tube, the focusing cup must be:

negatively charged The focusing cup must be negatively charged. The negative charge of the focusing cup repels the negative charge of the electrons within the electron stream. This compresses the electron stream and creates a tightly aligned x-ray beam with higher spatial resolution.