Chapter 6: X-Ray Tube (Test 1)

Ceiling Support

What x-ray support system consists of two perpendicular sets of ceiling-mounted rails that allow for both longitudinal and transverse travel of the x-ray tube?

Floor-To-Ceiling Support

What x-ray support system has a single column with rollers at each end, one attached to a ceiling-mounted rail and the other attached to a floor-mounted rail?

C-Arm Support

What X-ray support system is shaped like a C and has an image receptor attached to one end and the X-ray tube on the other end?

Fluoroscopy Support

What refers to the equipment and components that facilitate a fluoroscopy procedure, including the C-arm, R/F table, and image processing hardware and software that provide real-time X-ray images for diagnostic and guided procedures?

Ceiling Support System

What is the most frequently used X-ray support system?

Isotropic

What refers to x-rays emitted with equal intensity in all directions?

To protect against and reduce leakage radiation

What is the main purpose of the metal tube housing?

- Prevent electrical shock

- Provide mechanical support

- Contains oil as an insulator and coolant

What are some other properties of the metal tube housing?

Maintain a vacuum

What is the purpose of the glass envelope?

Pyrex glass to withstand extreme heat

What is the glass envelope made of and why?

Metal enclosures (less likely to fail)

What kind of envelope do some modern X-ray tubes have?

Cathode; filament and focusing cup

What is the negative side of the X-ray tube, and what are its two primary parts?

Filament

What is the thoriated tungsten coil of wire on the cathode side of the X-ray tube, which, once heated, emits electrons through thermionic emission?

Filament Current

What refers to the mA that warms up the filament?

Space Charge

What refers to a cloud of electrons around the filament that prevents the release of additional electrons?

Saturation Point

What refers to the point when no more electrons can be released?

Focusing Cup

What is the negatively charged metal shroud that compresses the electron stream and is where the thoriated tungsten filament is located?

Anode

What is the positive side of the X-ray tube that provides mechanical support for the target and is a good thermal conductor?

Anode Focal Track

What is the actual area on the anode target that is being bombarded by incoming electrons?

Rotating

What type of anode do X-ray machines use?

- Better heat dissipation

- Producing high-intensity x-ray beams in a short time

Why are rotating anodes used in X-ray machines?

3,400-10,000 rpm

How fast does a rotating anode spin?

1 min

What is the coast time of the anode?

Electromagnetic induction motor

What is used to turn the anode?

Stator

What consists of a series of electromagnets around the neck of the X-ray tube that creates a magnetic field?

Outside the glass envelope

Where is the stator located?

Rotor

What refers to a shaft made of bars of copper that reacts to the magnetic field, causing it to spin?

Inside the glass envelope

Where is the rotor located?

Anode Target

What refers to the front surface of the anode (round disc)?

Tungsten because of its high melting point (3400°c) and high atomic number (74)

What is the anode target made up of and why?

Alloying tungsten and rhenium

What metals make the anode target stronger, and are mainly located in the back of the target?

Molybdenum

What metal is layered with the anode target that makes it lighter?

Thermal conductivity (dissipating heat)

What is the anode target good at doing?

- Small filament (.5 to 1 cm)

- High spatial resolution

Small Focal Spot = ?

- Large Filament (1 to 2 cm)

- ↑ Heat

Large Focal Spot = ?

Line Focus Principle

What states that angling the target makes the effective focal spot size much smaller than the actual focal spot?

Effective Focal Spot

What refers to the area projected onto the patient and the image receptor?

- Smaller effective focal spot size

- Better heat dissipation

What are the advantages of a steep anode angle?

Anode Heel Effect

What refers to the intensity of the beam being greater on the cathode side of the X-ray tube due to photon absorption in the heel of the anode?

- Larger field sizes

- Short SID

- Steep anode angle

What could cause the anode heel effect to be more evident?

Decreases IR coverage

What does the anode heel effect do to the amount of IR coverage?

Biangular Tubes

What type of x-ray tubes use two areas on the target for the focal track (one small and one big) and provide two anode angles that result in two focal spot sizes?

Extrafocal Radiation or Off Focus Radiation

What type of radiation is created on parts of the anode target other than the focal track?

- Melting, cracking, or pitting of anode from excessive heat

- bronzing of tube

- glowing anode

- cracking of glass envelope

- broken filament (vaporization)

What are the causes of X-ray tube failure?

Broken filament

What is the #1 cause of x-ray tube failure?

- rotor

- rating charts

- warm

- overheating

- stopped

- technique

Steps To Extend Tube Life

- Do not _________ for a long time period

- Follow tube ________ ________

- ________ up anode before using tube

- Avoid ___________ the tube

- Wait until rotor has __________ before turning off unit

- Never change ____________ while rotor is activated

ma x time x kvp x constant x # of images

What is the heat units formula?

- 1

- 1.35

- 1.40

- 1.40

- Single phase HU = ?

- 3 phase 6 pulse HU = ?

- 3 phase 12 pulse HU = ?

- High frequency = ?