Chapter 6: X-ray Circuit & Tube Heat Management

The subcircuit located between the AC power supply and the primary side of the high-voltage transformer

Low-volage circuit

A device that terminates the exposure and is set by the operator on the control console

Exposure Timer

Terminates the exposure when a certain quantity of radiation has been detected at the image receptor

An automatic exposure control (AEC) system.

Used to determine the maximum tube capacity for a single exposure

Tube rating chart

The subcircuit that includes the x-ray tube and the rectifier unit

High-voltage circuit

Is activated any time the operator adjusts the mA on the generator

Filament circuit

X-ray machines that are powered by three separate sources of AC current at the same time are called:

Three-phase generators.

An electronic device that permits current to flow in one direction only

Diode

Is wired into the building, providing electrical power from the local power company

AC power supply

unit used to measure the maximum heat capacity of the anode

Heat units

Controls the power to the control console

Main Switch

System in which manual selection of the body area and projection automatically selects kVp, mA, time, AEC detectors, body habitus, bucky, and SID

Anatomically Programed Radiography (APR)

Device used to convert alternating current into direct current

Rectifier

Type of rectification in which the negative phase of the electric cycle is totally eliminated and a gap remains

Half-wave rectification

Reduces voltage, providing an appropriate current to heat the filament

Step-down transformer

Controls amperage in the filament circuit

mA selector

A moving grid that is used for radiography of larger parts of the body

Bucky

Single coil transformer that provides the means for kVp selection

Autotransformer

Type of rectification in which the current is “redirected”, during the negative half of the electric cycle so that the current will flow in the same direction during the negative and positive halves of the electric cycle

Full-wave rectification

The process of converting alternating current into direct current

Rectification

Closes the circuit, allowing electric current to flow through the primary side of the step-up transformer

Exposure switch

Into what three sections (subcircuits) is the x-ray circuit divided?

High voltage, low voltage, and filament circuits.

The autotransformer is primarily used for

variable kVp selection

Which of the following is the function of the autotransformer?
1. Provides the means for variable kVp selection
2. Provides compensation for fluctuations in the incoming line voltage
3. Supplies power to the other parts of the x-ray circuit

All 3

The quantity of power to the x-ray room that is supplied by the utility company is usually?

220V

Which control on the x-ray generator is adjusted to heat the filament in the x-ray tube?

mA

What is the purpose of the filament circuit?

Supplies the heat required by the x-ray tube filament for thermionic emission of electrons

Which transformer reduces the voltage on the secondary side to provide an appropriate current to heat the filament?

Step-down transformer

The process of causing alternating (AC) current to flow in one direction (DC) only is called

rectification.

Which of the following is located on the high-voltage side of the x-ray circuit?

A.     Autotransformer

B.     Step-down transformer

C.     mA selector

D.     X-ray tube

D. X-ray tube

In which circuit is the step-up transformer located?

High-voltage

Which of the following are true concerning high-frequency (HF) generators, compared to 1-phase and 3-phase generators?
1. Produce x-rays more efficiently
2. Require less exposure time
3. Produce the greatest amount of x-rays for the same technique

All 3

A series of warm-up exposures is made on a cold x-ray tube to:

prevent damage to the anode from sudden heating

To prolong x-ray tube life, the tubes should be operated at about______ of capacity.

80%

The maximum heat capacity of the anode of the x-ray tube is rated in terms of

heat units or HU

What is the formula to calculate the heat produced by an exposure made on a high-frequency (HF) generator?

mA × time (seconds) × kVp x 1.40

Nearly all new x-ray machines manufactured today use ____________________ generators.

high-frequency

Which type of exposure timer is capable of shorter exposure times (1 msec or less)?

Electronic Timer

In a high-frequency generator, the incoming 60 Hz electrical frequency is raised to what level?

6,000 Hz

Which of the following x-ray generators produces the greatest amount of x-rays for the same exposure technique?

A.     1-phase

B.     3-phase, 6-pulse

C.     3-phase, 12-pulse

D.     High-frequency

D. High-frequency

X-ray exposure times that can be set on the generator can go up to as high as ____ seconds.

4

Every x-ray exposure that is made will have what technical factors set on the control panel?
1. mA
2. kVp
3. Exposure time

All 3

Some x-ray generators are programmable, and the exposure factors from the technique chart can be programmed into the generator. This system is called

Anatomically Programed Radiography (APR)

How many detectors are built in to the AEC system and can be activated to determine the exposure technique?

3

Which of the following must be absolutely accurate when using APR for exposure technique?

A.     Setting the central ray

B.     Patient positioning

C.     Collimation size

D.     Determining the correct kVp

B. Patient positioning

When using APR to set the exposure technique, which of the following will be automatically selected with the simple push of a button?
1. mA
2. kVp
3. Grid

1 and 2 only

For which exposure technique system would a technique chart not be necessary?

APR

How many x-ray exposures should be made to warm up the x-ray tube?

3

The x-ray tube capacity for a single exposure can be determined by consulting the:

Tube rating chart

Which of the following would be considered good practice for maintaining x-ray tube life?
1. Use the high-speed rotor.
2. Use low mA settings whenever possible.
3. Do not hold down the rotor switch for long periods.

2 and 3 only

True or False: The main switch provides power to the entire x-ray system

True

True or False: The autotransformer is responsible for selecting the appropriate exposure time

False, the timer circuit is responsible for selecting exposure time in an x-ray system.

True or False: The kVp selector determines the energy of the x-ray beam

True

True or False: The exposure switch activates the x-ray tube to start exposure

True

True or False: A step-down transformer increases the voltage for the filament circuit

False, a step-down transformer decreases the voltage for the filament circuit.

True or False: The mA selector controls the current sent to the x-ray tube filament

True

True or False: The rectifier converts AC to DC for x-ray production

True

True or False: Half-wave rectification allows both halves of the AC cycle to pass through the x-ray tube

False, half-wave rectification only allows one half of the AC cycle to pass through, blocking the other half.

True or False: High-frequency generators produce a nearly constant x-ray output

True

True or False: A single-phase generator results in a pulsating x-ray beam

True

True or False: The x-ray control panel allows technologists to adjust milliamperage and exposure time

True

True or False: Automatic exposure control (AEC) ensures consistent image quality by terminating exposure based on radiation detected

True

True or False: Phototimers are a type of AEC device

True

True or False: The bucky control adjusts the speed of the rotating anode

False: The bucky control manages the movement of the grid, not the speed of the rotating anode.

True or False: The tube rating chart is used to determine safe operating conditions for the x-ray tube

True

True or False: Heat units (HU) are a measure of the heat generated in the x-ray tube during exposure

True

True or False: Prolonging the rotor activation time can help extend the life of the x-ray tube

False: Prolonging the rotor activation time can lead to overheating and damage to the x-ray tube, reducing its lifespan.

True or False: Inherent filtration is built into the x-ray tube housing

True

True or False: Full-wave rectification allows for shorter exposure times compared to half-wave rectification

True

True or False: Proper cooling intervals between exposures can help prevent damage to the x-ray tube

True