Dental X-Ray Machine Components – Chapter 3

A comprehensive set of Q&A flashcards covering the main topics from the lecture notes on dental x-ray machine components, circuits, and beam physics.

What are the external components of a dental x-ray machine and their primary functions?

The external components include the:

• master switch and exposure buttons (control exposure),

• regulators that manage machine operation

• the tube head that contains the x-ray tube and enables positioning of the tube head.

What does the control panel provide, and how is it typically configured?

It provides:

• electrical current connection and control

• dental clinics are often remote from the unit

• controls are usually pre-set by the manufacturer.

What does the milliampere selector (mA) measure?

The amount (rate) of current passing through the circuit, which determines the amount of x-rays produced.

What does the kilovolt peak selector (kVp) determine?

The difference in voltage across the x-ray tube, which determines the speed of electrons and their penetrating ability.

What is the function of the timer on the control panel?

It regulates the duration of the interval (how long) that the current will pass through the x-ray tube.

What is the purpose of the exposure button?

To activate the x-ray production process.

What is the extension arm and what does it do?

It allows:

• moving and positioning the tube head so the x-ray source is brought to the imaging area;

• it also contains wires connecting the base to the tube head.

What does the tube head contain and what are its protective and cooling roles?

Contains:

• the x-ray tube,

• insulating oil,

• and transformers;

  Protective and cooling roles:

• protects the x-ray tube,

• grounds high-voltage components,

• prevents overheating,

• absorbs non-contributing x-rays.

What are the two circuits used in producing dental x-rays and what are their roles?

Filament circuit provides low-voltage to the filament to generate electrons;

High-voltage circuit provides high-voltage to accelerate electrons from the cathode to the anode.

Where are transformers located and what is their purpose?

• Located in the tube head;

• they decrease or increase the current entering the x-ray machine,

  • step-down for the filament (low voltage) and

  • step-up for accelerating electrons toward the target (high voltage).

What does amperage measure and what is its common unit in dental x-ray machines?

Amperage Measures the rate (amount) of electrons that move through a conductor;

The unit is the ampere,

Dental machines typically operate from: 4 to 15 mA

How does voltage relate to x-ray production? What kV range do dental machines typically use?

Voltage= speed of electrons and their penetrating power;

dental x-ray machines typically operate at 50 kVp to 100 kVp.

What are cathode and anode in the x-ray tube and their roles?

Cathode is the negative electrode that supplies electrons (thermionic emission);

Anode is the positive electrode with a tungsten target that stops electrons and produces x-rays.

What is the tungsten target angle in the anode and why is it significant?

Tungsten Target= 20-degree angle to the cathode;

Significance= directs most x-rays through the window toward the port opening and helps form the primary beam.

What is the focal spot and how does its size affect radiographic images?

A small rectangular area on the anode target where the electron beam is focused; its size influences the sharpness of the radiographic image

What are the primary beam and central ray?

• The primary beam is the useful x-rays originating at the focal spot;

• the central ray is the x-ray at the center of the primary beam.

What are the three conditions that must exist for X-rays to be produced in the x-ray tube?

1. A vacuum (glass bulb evacuated),

2. A source of electrons at the cathode (thermionic emission),

3. A target at the anode (tungsten) for X-ray production.

What defines X-ray beam quantity and quality, and what factors affect intensity?

• Quantity is the number of photons; (mA) Amount

• Quality is the energy/penetration; (KV) How fast?

  Intensity is the product of quantity and quality.

• Intensity is affected by mA, kV, exposure time, and distance.