Chapter 5 X-ray Tube

Of all the energy involved in x-ray production, ___________ % is converted to x-ray energy. 1 10 50 99

1%

The induction motor turns the rotor of a specialty x-ray tube________ revolutions per minute. 1400 3400 6000 10,000

10,000

By regulation, x-ray tube leakage radiation can be no more than: 100 R per hour 100 R per minute 100 mR per hour 100 mR per minute

100 mR per hour

How many heat units are produced with five consecutive exposures using a three-phase, 12-pulse x-ray unit; 85 kVp; and 20 mAs? 1700 HU 2295 HU 2397 HU 11,985 HU

11,985 HU

The most common x-ray tube target angle is: 2 degrees 8 degrees 12 degrees 18 degrees

12 degrees

The induction motor turns the rotor of a standard x-ray tube__________ revolutions per minute. 1400 3400 6000 10,000

3400

The melting point of tungsten is: 400 (degrees)C 1400 C 2400 C 3400 C

3400 degrees Celsius

How many heat units are produced with an exposure using a single phase x-ray unit, 75 kVp, and 50 mAs? 3750 HU 5063 HU 5288 HU 5438 HU

3750 HU

The target window is usually approximately: 1 mm squared 5 mm squared 2 1 cm 5 cm squared

5 cm squared

Each cathode filament is approximately: 1-3 mm long 5-7 mm long 7-15 mm long 20-35 mm long

7-15 mm long

Most x-ray tube target angles range between: 2-5 degrees 7-18 degrees 20-28 degrees 35-45 degrees

7-18 degrees

The atomic number of tungsten is: 14 34 74 104

74

Cooling charts are available for the: tube housing anode cathode A and B

A and B

Molybdenum is found in the_________ of the rotating anode. shaft disc target area A and B

A and B

The anode includes the: target induction motor envelope A and B

A and B

To keep the electrons together, the focusing cup: has a negative charge has a positive charge physically surrounds the electron cloud A and C

A and C

The cathode includes the: envelope filaments focusing cup B and C

B and C

When the exposure switch at the operating console is first depressed: high voltage creates a large potential difference between the anode and the cathode the anode starts rotating thermionic emission is achieved B and C

B and C

Modern x-ray equipment is so safe that it is all right to handle the high-voltage cables. T/F

False

Prepping the rotor but not making an exposure on a regular basis is unrelated to tube damage or failure. T/F

False

The oil surrounding the x-ray tube serves only to provide electrical insulation. T/F

False

The physical area of the target where electrons strike is the effective focal spot. T/F

False

To take advantage of the anode heel effect, the thicker part of the anatomy being imaged should be placed under the anode end of the tube. T/F

False

To take advantage of the anode heel effect, the thinner part of the anatomy being imaged should be placed under the cathode end of the tube. T/F

False

Tungsten is used in the cathode filament because it is able to vaporize very easily. T/F

False

When the electrons strike the anode target, they all produce x-rays T/F

False

In addition to the oil surrounding the tube, mechanical fans help to eliminate the heat produced during x-ray production T/F

True

Many newer x-ray units do not need the radiographer to go through a warm up procedure. T/F

True

The effective focal spot is smaller than the actual focal spot because the face of the anode is angled. T/F

True

The stator is made up of electromagnets. T/F

True

To get the rotor to move, each pair of stators are energized sequentially. T/F

True

Using very long exposures can lead to tube damage or failure. T/F

True

When x-rays are produced inside the tube they travel in all directions T/F

True

The stationary anode includes an area of tungsten embedded in: a copper rod a tungsten rod a molybdenum disc a copper disc

a copper rod

If the anode angle becomes too small, which of the following may result? x-ray beam size may start to be limited the intensity of the beam near the anode may be reduced the anode heel effect may be seen all of the above

all of the above

The anode serves as a(n): target to stop the electrons traveling from the cathode electrical conductor heat conductor all of the above

all of the above

The cathode: includes a focusing cup provides electrons for x-ray production includes filaments all of the above

all of the above

The protective tube housing helps to: keep the tube cool prevent electrical shocks to the radiographer limit leakage radiation all of the above

all of the above

Tube rating charts: are no longer used to select safe exposures have been replaced by protective circuits are useful today as quality control tools all of the above

all of the above

An issue with using glass envelopes is that they: lose their resistance to heat over time are very expensive to purchase break into small pieces of glass when they break allow vaporized tungsten to coat the inside of the glass

allow vaporized tungsten to coat the inside of the glass

The rotor is made of: an iron core a molybdenum core tungsten rhenium

an iron core

The positive end of the x-ray tube is the: anode cathode filament envelope

anode

The electrons in the tube current travel: at the speed of light approximately half the speed of light approximately one-fouth the speed of light none of the above

approximately half the speed of light

After lengthy exposures, the x-ray tube on a mobile fluoroscopic unit may: be very hot produce large electric shocks exceed leakage radiation limits none of the above

be very hot

The negative end of the x-ray tube is the: anode cathode target envelope

cathode

Tungsten is used to coat the anode disc because it: has a low melting point has a low atomic number conducts heat well does not conduct heat well

conducts heat well

Electrons from the cathode that do not produce x-rays will: be absorbed in the envelope return to the cathode filament be absorbed in the air in the tube continue on through the circuit

continue on through the circuit

The _________ is used to calculate the length of time needed between exposures to that the tube's heat loading capacity is not exceeded. tube rating chart exposure factor chart cooling chart heating chart

cooling chart

Which of the following occurs first during x-ray production? thermionic emission voltage is transformed to kilovoltage current passes through the rheostat kilovoltage is applied to anode and cathode

current passes though the rheostat

Based on the anode heel effect, an image taken at 40 inches SID may demonstrate: decreased exposure toward the anode end of the beam decreased exposure toward the cathode end of the beam decreased exposure toward the left side of the beam decreased exposure to the right side of the beam

decreased exposure toward the anode end of the beam

An x-ray tube with two filaments is called a: two-focus tube dual-focus tube trifocal tube highly specialized tube

dual-focus tube

The tube rating chart plots mA, kVp, and: amperage voltage exposure time resistance

exposure time

The filaments are part of the: filament circuit primary circuit secondary circuit none of the above

filament circuit

In terms of the x-ray tube, envelope is another name for the: anode cathode glass or metal enclosure induction motor

glass of metal enclosure

The primary advantage of a rotating anode is that it allows: greater heat capacity at the anode less heat capacity at the anode greater heat capacity at the cathode less heat capacity at the cathode

greater heat capacity at the anode

Tungsten is used to coat the anode disc because it: has a low melting point has a low atomic number has a high atomic number does not conduct heat well

has a high atomic number

Tungsten is used to coat the anode disc because it: has a high melting point has a low melting point has a low atomic number does not conduct heat well

has a high melting point

Of all the energy involved in x-ray production, 99% is converted to: x-rays electrons heat none of the above

heat

The formula kVp X mA X s X c is used to calculate: heat units cooling time heating time all of the above

heat units

Thermionic emission is: heating the filament heating the filament until electrons are boiled off using the focusing cup to create a space charge the space charge that travels from cathode to anode

heating the filament until electrons are boiled off

The primary disadvantage to the stationary anode is that it: is too expensive heats up too quickly during x-ray production uses tungsten all of the above

heats up too quickly during x-ray production

Pitting the anode is the result of: very long exposure times high exposures failure to warm up the tube all of the above

high exposures

X-ray tubes with a stationary anode design may be found today: in small x-ray departments in small x-ray tubes in medical areas that only need small x-ray exposures in medical areas that only image the head and teeth

in medical areas that only need small x-ray exposures

Copper can be found __________ of the rotating anode. in the shaft in the target area surrounding the tungsten in the base

in the shaft

The rotor is found: near the tube window outside the envelope inside the envelope towards the cathode end of the tube

inside the envelope

Molybdenum: is an excellent conductor of electricity is a poor conductor of electricity is an excellent thermal conductor is a poor thermal conductor

is a poor thermal conductor

Arcing: is a problem associated with glass envelopes is a problem associated with metal envelopes is another name for the flow of electrons from cathode to anode is another name for the flow of electrons from anode to cathode

is a problem associated with glass envelopes

Copper is used in the rotating anode because: it is an excellent conductor it is an excellent insulator it has a high atomic number it has a low atomic number

it is an excellent conductor

Glass enclosures are typically made of borosilicate glass (Pyrex) because; it is an inexpensive material it is an expensive material it is very heat-resistant none of the above

it is very heat-resistant

The purpose of the focusing cup is to: produce thermionic emission from the filament prevent thermionic emission from the filament allow the electrons to spread out keep the electrons together

keep the electrons together

Which of the following occurs last during x-ray production? kilovoltage is applied to anode and cathode thermionic emission AC is converted to DC the rotor starts turning

kilovoltage is applied to anode and cathode

The best situation is to have a __________ actual focal spot and a __________ effective focal spot. large; large small; small large; small small; large

large; small

The protective tube housing is lined with: aluminum copper lead glass

lead

One of the reasons that molybdenum is used in rotating anodes is because it is: light heavy dense an excellent conductor

light

The focusing cup is able to keep the electrons together because: opposite charges repel opposite charges attract like charges repel like charges attract

like charges repel

To allow x-rays to leave the tube, the glass or metal enclosure in the area of the target window is: removed made thicker made thinner hinged to allow the window to open

made thinner

The primary purpose of the glass or metal enclosure is to: insulate against electrical shock maintain a vacuum allow the heat to dissipate none of the above

maintain a vacuum

The rotating anode design uses a disc whose core is made of: copper tungsten aluminum molybdenum

molybdenum

The motor that turns the anode operates through: the use of a transformer the physical connection between rotor and the stator self-induction mutual induction

mutual induction

The focusing cup is made of: tungsten nickel thorium molybdenum

nickel

Which of the following practices extend tube life? press the prep and exposure switch at almost the same time warm up the tube just before turning the equipment off use high exposures none of the above

press the prep and exposure switch at almost the same time

For the covering of the rotating anode disc, _________ may be added to tungsten to increase thermal capacity. molybdenum rhenium copper none of the above

rhenium

The two types of anode designs are stationary and: traveling rotating dynamic all of the above

rotating

The focusing cup is part of the: filament circuit primary circuit secondary circuit none of the above

secondary circuit

The effective focal spot is the: same as the actual focal spot actual area where the electrons hit the target actual size of the origin of the x-ray beam size of the origin of the x-ray beam as seen from below the tube

size of origin of the x-ray beam as seen from below the tube

The cloud of electrons produced through thermionic emission is more accurately called a(n): space cloud electron cloud electron charge space charge

space charge

The portion of the induction motor that is outside the tube enclosure is the: rotor stator disc bearings

stator

Part of the useful x-ray beam gets absorbed in the anode when: the anode angel is too large the anode angle is too small the actual focal spot is too large the actual focal spot is too small

the anode angle is too small

Excessive heat may be transferred to the rotor bearings, resulting in: the anode rotating faster than it should the anode rotating slower than it should the anode rotating unevenly all of the above

the anode rotating unevenly

The space charge effect describes: -how the space charge is created -the effect the cloud of electrons has on the voltage across the tube -the effect the cloud of electrons has on limiting additional electrons being emitted -the effect of the heat of the filament on the size of the space charge

the effect the cloud of electrons has on limiting additional electrons being emitted

The advantage to using a small effective focal spot is: the image is sharper the image is less sharp less exposure can be used it is safe for the patient

the image is sharper

The relationship between the actual focal spot size, effective focal spot size, and the anode target angle is called: the anode heel effect the line-focus principle Roentgen's principle all of the above

the line-focus principle

The size of the actual focal spot depends on: the size of the anode the size of the cathode filament being used the size of the effective focal spot the size of the tube

the size of the cathode filament being used

The smaller the anode angle: the smaller the actual focal spot the larger the actual focal spot the smaller the effective focal spot the larger the effective focal spot

the smaller the effective focal spot

Heat from x-ray production is removed through conduction by the heat traveling from: the tube to the room by cooling fans the tube to heat tolerant materials the tube to the oil bath none of the above

the tube to heat tolerant materials

Heat from the x-ray production is removed though radiation by the heat traveling from: the tube to the room by cooling fans the tube to heat tolerant materials the tube to the oil bath none of the above

the tube to the oil bath

Heat from x-ray production is removed through convection by the heat traveling from: the tube to the room by cooling fans the tube to heat tolerant materials the tube to the oil bath none of the above

the tube to the room by cooling fans

There is a small amount of _________ added to the filament to increase thermionic emission. thorium rhenium tungsten copper

thorium

With a rotating anode, the focal spot becomes a focal: path stripe track circle

track

The filament is primarily made of: rhenium copper molybdenum tungsten

tungsten

The stationary anode includes an area of _________ embedded in a copper rod: copper molybdenum tungsten glass

tungsten

Which of the following occurs first during x-ray production? voltage is transformed to kilovoltage kilovoltage is applied to anode and cathode alternating current is changed to direct current voltage level is adjusted at autotransformer

voltage level is adjusted at autotransformer

The area of the envelope where x-rays should exit the tube is the: door window trap gate

window