Unit 4 Exam

The most widely used support structure for the x-ray tube is the:

Ceiling support system

The external structure of the x-ray tube includes:

Protective housing, glass envelope, support structure

Which tube structure reduces leakage radiation, guards against excessive radiation exposure, and electric shock?

Protective housing

Leakage radiation must not exceed?

1 mGy/hr measured at 1 meter

The negative side of the x-ray tube holds the:

Filament

The function of the cathode is to produce a

Thermionic cloud

Filament materials are chosen primarily for their:

high melting points

A filament may break due to:

vaporization

The filament is made of?

Tungsten

Thermionic emission at the filament creates a:

Space charge

The rotating anode is turned by a _____.

magnetic field

When electrons bombard the target, _________ % of their kinetic energy is converted into heat

99

The target of the rotating anode is usually coated with a __________ alloy

Tungsten

X-ray photon production occurs at the:

Anode

The _________ of the x-ray conducts electricity, radiates heat, and contains the target

Anode

As an x-ray tube ages, the inside can become coated with tungsten, which can cause _____ in the tube.

Arcing

Tungsten is the metal of choice for the source of x-ray photons because of its

High melting point and high atomic number

What is the most common cause of tube failure?

tungsten vaporization

Electrons accelerate from the cathode and are focused to a small area on the anode called the:

Actual focal spot

Because of the line focus principle, the effective focal spot size decreases with decreasing:

Target angle

High capacity tube rotors revolve at?

10,000 rpm

The area of the focal spot that is projected out of the tube and onto the patient and IR is called the?

Effective focal spot

The line focus principle results in an _____________ much smaller than the _____________

effective focal spot size, actual focal spot size

As more and more electrons build up in the area of the filament, their negative charges oppose the emission of additional electrons. This phenomenon is known as

Space charge effect

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

Heel effect

When referring to the "heel" effect, the cathode side of the tube should be directed toward the ___________ part of the patient

Thicker

What kind of radiographic study would best benefit applying the anode heel effect?

thoracic spine

When referring to the "heel" effect , the effective focal spot is smaller on the cathode end

False

__________ is produced because some of the electrons may bounce off the focal spot and land on other areas of the target

off-focus radiation

Cracking of the anode typically occurs

When a cold anode is hit with a high kVp exposure

Pitting of the anode commonly occurs:

with extended use

What is the source of radiation in the x-ray tube?

Focal spot

What is the formula for heat units for a high frequency x-ray machine?

1.4 x kVp x mA x seconds

Bearing damage is a cause of tube failure because of heat conducted to the bearings located in the:

Rotor

A dual focus tube has two

filaments

Tube failure can occur from:

long exposure times

Each tube has its own tube rating chart to show:

maximum exposure times

The only portion of the anode assembly placed outside the vacuum of the envelope is the

Stator

What is the total number of heat units produced with a single-phase imaging system when using 98 kVp, 180 mAs for a lateral lumbar spine?

17,640

The heel effect is caused by the:

anode angle

Projectile electrons travel from the:

cathode to anode

During an exposure, most of the _____ energy of the projectile electrons is converted to _____.

Kinetic; heat

At the target, the projectile electrons interact with:

outer and inner shell electrons

The efficiency of x-ray production is _____________ of tube current.

independent

Most of the heat generated at the target is due to:

outer-shell electrons

The production of heat at the anode is directly proportional to:

tube current

The efficiency of x-ray production increases as _____ increases.

kVp

Approximately ____________ & of kinetic energy of the projectile electrons is converted to x-rays at the target

1

Electron interactions at the inner-shell of the target atoms produce _______ radiation

characteristic

The useful characteristic x-rays from tungsten targets are ________ x-rays

k-shell

Characteristic K-shell x-rays have an effective energy of ______ keV

69

Most of the x-rays produced at the target are:

Bremsstrahlung

At 62 kVp, _________ of the x-rays produced are Bremsstrahlung

100%

Bremsstrahlung x-rays are produced by _______ at the target

slowing electrons

Characteristic x-rays are produced by:

released binding energy

The quantity of bremsstrahlung radiation increases proportionally with increased:

mAs

During a characteristic interaction, the kinetic energy of the incident electron must be _______ the electron it knocks from its orbit

greater than that of

During a characteristic interaction, the dropping of a higher-energy state electron into a lower-energy state hole results in the emission of?

A photon of electromagnetic energy

Characteristic interactions may occur only when the incident electron interacts with:

An inner-shell electron

The energy of characteristic photon is:

the difference between the binding energy of the outer and inner shells between which the electron dropped

At the end of the characteristic cascade, the __________ shell is missing an electron

Outer

AN exposure taken at 100 kVp would have a continuous emission spectrum with a maximum energy of ______

100

The _______ of an x-ray beam is higher when the peal of the emission spectrum is further to the ___________

Quality; right

An increase in mAs would _____ the _____ of the emission spectrum.

Increase, amplitude alone

Changes in __________ results in directly proportional changes in amplitude of the emission spectrum

Both mA and mAs

The discrete portion of the x-ray spectrum would change position with a change in?

Both kVp and target material

The amplitude of the emission spectrum with a ________ generator is ___________ it is with a three-phase generator

Single-phase; lower than

A 15% increase in kVp is equivalent to:

doubling the mAs

How does added filtration affect the emission spectrum?

increase in the average energy of the x-ray beam with an accompanying reduction in x-ray intensity

As the actual focal spot increases, the effective focal spot size:

Increases

The function of the stator and rotor assembly is to:

Rotate the anode

The most common diagnostic radiology target angle is:

12 degrees

Electrons traveling from the cathode filament to the anode are called?

tube current

Radiographic examination of the lumbar spine with a single-phase imaging system requires 90 kVp, 150 mAs. How many heat units are generated by the exposure?

13,500