X-ray Tube, Circuit, & Tube Heat Management

What is 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

This terminates the exposure when a certain quantity of radiation has been detected at the image receptor:

An automatic exposure control (AEC) system.

What is 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

What 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 use:

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

The unit used to measure the maximum heat capacity of the anode:

Heat units

What controls the power to the control console?

Main Switch

What is the 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)

What is the device used to convert alternating current into direct current?

Rectifier

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

Half-wave rectification

Device that reduces voltage, providing an appropriate current to heat the filament:

Step-down transformer

What controls amperage in the filament circuit?

mA selector

What is a moving grid that is used for radiography of larger parts of the body called?

A bucky

A 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

Device that 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

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

mA

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

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

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 (HU)

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

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

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?

Three

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

The three main parts of the x-ray imaging system are the x-ray tube, ____________, and ____________.

operating console; high voltage generator

The operating console contains circuits that are ________________.

low voltage only

Variations in power distribution to the x-ray machine are corrected by the ____________.

line voltage compensator

The first component to receive power in the x-ray circuit is the ______________.

autotransformer

The autotransformer has _____ winding(s).

one

The _________ circuit provides electrons for the x-ray tube current.

filament

A step-down transformer is located in the _______ circuit.

filament

The most accurate type of timer is the ________ timer.

electronic

The automatic exposure control (AEC) terminates the exposure when ________________.

sufficient radiation reaches the image receptor

A diode allows electrons to flow from ___________.

cathode to anode

With half-wave rectification, the current flows through the x-ray tube during the ________ part of the cycle.

positive

Voltage across the x-ray tube is most constant with _________________.

high frequency generators

The negative side of the x-ray tube holds the ________.

filament

What is the most common cause of tube failure?

tungsten vaporization

Thermionic emission at the filament creates a __________.

space charge

When electrons bombard the target, ____% of their kinetic energy is converted to heat.

99

The ___________ is the source of radiation in the x-ray tube.

focal spot

Because of the line focus principal, the effective focal spot size decreases with decreasing _____________.

target angle

The x-ray intensity is lower on the anode side of the tube because of the _________.

heel effect

The cathode side of the tube should be directed toward the _____ part of the patient.

thicker

A dual focus tube has two _______.

filaments

Each tube has its own tube rating chart to show ___________.

maximum exposure times