Chapter 5: X-ray Production

Created when an incoming electron is suddenly slowed down, changes direction, and leaves the tungsten atom.

Bremsstrahlung radiation

Refers to the area on the target surface that is struck by the electron stream

Actual focal spot

The negative, filament end of the x-ray tube

cathode

Unit used to measure the voltage across the x-ray tube

kVp (kilovolt peak)

Refers to the length of time that the x-rays are turned on

Exposure time

Metal element used to make the filament and target in an x-ray tube

Tungsten

The process of removing long wavelength photons from the x-ray beam

Filtration

The tungsten focal area all around the beveled edge of the rotating anode

Focal track

Hollow area in the cathode where each filament is situated

Focusing cup

The vertical projection of the actual focal spot onto the patient and image receptor

Effective focal spot

Used to describe the sharpness of the structures recorded in the image

Spatial resolution

The source of electrons at one end of the x-ray tube and consists of a small coil of tungsten wire

Filament

Created when an incoming electron interacts with the k-shell electron and knocks it out of orbit

Characteristic radiation

Contains two filaments, one large and one small

Dual-focus tube

The uneven distribution of radiation intensity in the x-ray beam resulting in a higher intensity on the cathode side

Anode heel effect

The positive, target end of the x-ray tube

anode

A small bundle of electromagnetic energy

Photon

The slant of the anode surface

Target angle

The process in which heat speeds up the movement of the electrons in their orbit and increases their distance from the nucleus

Thermionic emission

The measure of the rate of current flow across the x-ray tube

Milliamperage (mA)

The precise area on the target where the electrons from the filament are repelled onto

Focal spot

This means that the x-ray beam is made up of photons that have different wavelengths and energies

Heterogeneous

Used to indicate the quantity of exposure

Milliampere-seconds (mAs).

Filtration that is built into the x-ray tube and includes the tube glass and its surrounding oil

Inherent filtration

Equal to the inherent filtration plus the added filtration

Total filtration

Also called space charge, is the source of free electrons for x-ray production

Electron cloud

The x-ray tube inside the protective housing is made of:

Pyrex glass

What are the four essential elements required for x-ray production?

A target, a vacuum, an electron source, and a high potential difference

The filament of an x-ray tube is made of:

a coil of tungsten wire

The target of the x-ray tube is made of:

Tungsten

A device for removing long wavelength radiation from the primary x-ray beam is a:

filter

Free electrons at the cathode that are used for x-ray production come from the:

filament

When tungsten atoms are heated, their outermost electrons are moved out of the atom in space. This principle is called:

thermionic emission

The anode, or target, of the x-ray tube is _____________ charged.

positively

The cathode end of the x-ray tube is ____________ charged.

negatively

Most x-ray tubes in use today have a standard rotation speed of ___________ rpm.

3,600

What is the principal advantage of a high-speed rotating anode?

More efficient heat dissipation

The greatest portion of the x-ray beam is made up of:

bremsstrahlung-produced radiation

Below what kVp level is characteristic radiation no longer produced?

Below 70 kVp

What is required to move the electron stream rapidly across the x-ray tube?

High potential difference

More than 99% of the energy applied to an x-ray tube is converted into:

heat, not x-rays.

What percentage of the total energy applied to an x-ray tube target is converted into x-rays?

Less than 1%

Which of the following are the types of radiation produced in the anode?

A.     Thermionic emission and heat

B.     Electromagnetic and thermal

C.     Characteristic and bremsstrahlung

D.     Remnant and scatter

C. Characteristic and bremsstrahlung

What type of radiation is produced in the anode by the sudden slowing and directional change of an incoming electron?

Bremsstrahlung radiation

What type of radiation is produced when an incoming electron interacts with the K-shell electron in the tungsten atom?

Characteristic radiation

The purpose of rotating the x-ray tube target is to:

increase the heat capacity of the anode

The degree of angulation of the x-ray tube target will determine the:

effective focal spot

A smaller effective focal spot produces?

greater image sharpness

A larger actual focal spot produces

A.     greater image sharpness.

B.     greater tube heat capacity.

C.     lower patient dose.

D.  more characteristic radiation

B. greater tube heat capacity.

Which of the following can be found on a dual-focus x-ray tube?
1. Two filaments
2. Two focal spot sizes
3. Two anodes

1 and 2 only

The anode heel effect is a phenomenon of x-ray production that results in:

uneven distribution of radiation within the field

Taking into account the anode heel effect when making a recumbent AP radiograph of the femur (thigh bone) on a 35 x 43 cm IR at 40 inches SID, the patient should be placed so that the:

head is toward the cathode end of the tube

The penetrating power of the x-ray beam is controlled by varying the:

kilovoltage (kVp)

The current across the x-ray tube is measured in units of

milliamperes (mA)

Which of the following occurs when the mA is doubled?
1. The number of x-ray photons decreases by 50%.
2. Radiographic density increases.
3. There are twice as many photons in the x-ray beam.

2 and 3 only

The mAs used for an exposure determines the

quantity of radiation in the exposure

An x-ray exposure is made using the following factors: 400 mA, 0.02 seconds, 80 kVp, 40 inches SID, and the large focal spot. What is the mAs for this exposure technique?

8 mAs

When exposure time is very short, the time is usually measured in

milliseconds

If an exposure time is measured as 35 milliseconds, what is the exposure time in seconds?

0.035 seconds

The x-ray beam is made up of many different energy x-rays. This beam is referred to as:

Heterogeneous

Which of the following statements is true regarding the characteristics of tungsten?

A.     Tungsten has a low melting point.

B.     Tungsten is a very soft metal.

C.     Tungsten is a very unstable element.

D.     Tungsten has a high melting point.

D. Tungsten has a high melting point.

X-ray equipment capable of producing 70 kVp or more must have how much equivalent aluminum filtration?

At least 2.5 mm Al equivalent

What is the primary advantage of x-ray beam filtration?

To reduce patient exposure and improve image quality by removing low-energy x-rays.

A steeper target angle provides

smaller effective focal spot

Filtration _______________ the average wavelength of the x-ray beam.

decreases

The precise area on the target where the x-rays strike is called the:

focal spot

How is the electromagnetic induction motor used in the x-ray machine?

To rotate the anode

The difference in x-ray intensity (or volume of x-rays) between the anode and the cathode side of the x-ray beam is:

45%

The density in the radiographic image is primarily controlled by the

mAs

The contrast in the radiographic image is controlled by the

kVp

Which of the following would be considered inherent filtration?
1. Oil
2. Mirror
3. Pyrex glass

all 3

Which of the following would be considered added filtration in the x-ray tube?

Aluminum sheet

What is the effect on the x-ray tube when the high-speed anode kicks in?

Enables the anode to dissipate heat

True or False: The filament in the x-ray tube is made of tungsten because of its high melting point.

True

True or False: Thermionic emission refers to the release of protons from the filament when heated.

False, thermionic emission is the release of electrons.

True or False: The space charge effect limits the number of electrons emitted by the filament

True

True or False: Bremsstrahlung radiation results in a continuous spectrum of x-ray energies

True

True or False: Characteristic radiation produces x-rays with discrete energy levels.

True

True or False: The cathode is the positive electrode of the x-ray tube.

False. The cathode is the negative electrode in an x-ray tube.

True or False: A focusing cup directs the electron cloud toward the anode.

True

True or False: A dual-focus tube contains two filaments for different focal spot sizes.

True

True or False: The rotating anode is used to distribute heat over a larger area.

True

True or False: The target angle on the anode affects the effective focal spot size.

True

True or False: The line focus principle balances image sharpness with heat dissipation.

True

True or False: The anode heel effect results in greater x-ray intensity on the anode side of the beam.

False. The anode heel effect results in greater intensity on the cathode side of the beam.

True or False: Kilovoltage (kV) controls the energy of the x-rays produced.

True

True or False: Milliamperage (mA) determines the quantity of x-rays emitted.

True

True or False: Decreasing exposure time increases the total number of x-rays produced.

False. Decreasing exposure time reduces the total number of x-rays produced because there is less time for exposure.

True or False: Milliamperage-seconds (mAs) represents the total x-ray quantity.

True

True or False: Inherent filtration is provided by the x-ray tube housing

True

True or False: Added filtration is not required in modern x-ray machines

False. Added filtration is often required to improve x-ray beam quality and reduce patient exposure.

True or False: Total filtration is the sum of inherent and added filtration.

True

True or False: X-ray beam filtration improves patient safety by removing low-energy x-rays.

True