Physics Ch 7

Front 1

What is the most common used support system in x-ray?

Back 1

ceiling support system

Front 2

The __________ support system has a single column with rollers at each end, one attached to a ceiling mounted rail and the other attached to a floor-mounted rail.

Back 2

floor-to-ceiling support

Front 3

Angiointerventioal radiology suites often are equipped with _________ support systems, so called because the system is shaped like a _____.

Back 3

C-arm support system, "C"

Front 4

When x-rays are produced, they are emitted ____________, that is, with equal intensity in all directions.

Back 4

isotropically

Front 5

We use x-rays that are emitted through the special section of the x-ray tube called the ___________.

Back 5

window

Front 6

Those x-rays emitted through the window are called the _____________.

Back 6

useful beam

Front 7

X-rays that excape through the protective housing are _________________;they contribute nothing in the way of diagnostic information and result in unnecessary exposure of the patient and radiologic technologist.

Back 7

Leakage radiation

Front 8

Properly designed protecctive housing reduces the level of leakage radiation to less than ___________ at ________, when operated at maximum condtions.

Back 8

100 mR/hr, 1 m

Front 9

Protective housing gaurds against _______________ and ______________.

Back 9

excessive radiation and electric shock

Front 10

The protective housing around some x-ray tubes contains oil that serves as both an __________ against electric shock and as a _____________ to dissipate heat.

Back 10

insulator; thermal cushion

Front 11

An x-ray tube is an electronic vacuum tube with components contained within a _______ or _________ enclosure.

Back 11

glass; metal

Front 12

The enclosure maintains a ________ inside the tube.

Back 12

vacuum

Front 13

Early x-ray tubes, modifications of the ________ tube, were not _________ tubes but rather contained controlled quanitites of _______ within the enclosure.

Back 13

cookes; vacuum; gas

Front 14

___________ maintain a constant electric potential between the electrons of the tube current and the enclosure.

Back 14

Metal enclosure tube

Front 15

X-ray tubes are designed with a ________ or a ________ enclosure.

Back 15

glass; metal

Front 16

The x-ray tube window is an area of the glass or metal enclosure, approoximately ________, that is thin and through which the _______ of x-rays is emitted.

Back 16

5 cm2 (squared); useful beam

Front 17

The _____ is the negative side of the x-ray tube; it has two primary parts: a _________ and a _______________.

Back 17

cathode; filament; focusing cup

Front 18

The __________ is a coil of wire similar to that in a kitchen toaster, except much smaller.

Back 18

filament

Front 19

The filament is approximately ______ in diameter and ___ or ___ cm long.

Back 19

2 mm; 1 or 2 cm

Front 20

An x-ray tube __________ emits _________ when it is heated.

Back 20

filament; electrons

Front 21

When the current throguh the filament is sufficiently high, the __________ electrons of the filament atosm are ________ and ejected from the filament.This phenomenon is known as ______________.

Back 21

outer-shell; "boiled off"; Thermionic emission.

Front 22

Filaments are usually made of ____________.

Back 22

thoriated tungsten

Front 23

Tungsten provides for higher ___________ than other metals.

Back 23

thermionic emission

Front 24

Tungsten's melting point is ___________; therefore it is not likely to burn out like the filament of a light bulb.

Back 24

3410 degrees c

Front 25

______________ with deposition on the inside of the glass enclosure is the most common cause of tube failure.

Back 25

Tungsten vaporization

Front 26

The filament is embedded in a metal cup called the ____________.

Back 26

focusing cup

Front 27

Because all the electrons accelerated from ________ to _________ are electrically negative, the electron beam tends to spread out owing to _________________.

Back 27

cathode to anode; electrostatic repulsion

Front 28

T/F some electrons can even miss the anode completely.

Back 28

True

Front 29

The focusing cup is __________ charged so that it electrostatically confines the electron beam to a small area of the anode.

Back 29

negatively

Front 30

Most rotating anode x-ray tubes have ______ filametns mounted in the ______ assemble "side by side," creating large and small focal spot sizes.

Back 30

two; cathode

Front 31

When the x-ray imaging system is first turned on, a low current passes through the __________ to warm it and prepare it for the _________ necessary for x-ray production.

Back 31

filament; thermal jolt

Front 32

At _______________, there is no tube current because the filament does not get hot enough for ___________.

Back 32

low filament current; thermionic emission

Front 33

The x-ray tube current is adjusted by controlling the _____________.

Back 33

filament current

Front 34

The cloud of electrons, called a ________________, makes it difficult for subsequent electrons to be emitted by the filament because of ___________. This phenomenon is called the _________________.

Back 34

space charge; electrostatic repulsion; space charge effect

Front 35

______________ at low kVp and high mA can be space charge limited.

Back 35

therminonic emission

Front 36

The __________ is the positive side of the x-ray tube.

Back 36

anode

Front 37

There are two types of anodes ________ and ___________.

Back 37

stationary and rotating

Front 38

_____________ x-ray tubes are used in dental x-ray imaging systems, some portable imaging systems, and other special purpose units in which high tube current and power are not required.

Back 38

Stationary anode

Front 39

General purpose x-ray tubes use the _______________ because they must be capable of producing high intensity x-ray beams in a short time.

Back 39

rotating anode

Front 40

The __________ is the positive side of the x-ray tubel it conducts electricity and radiates heat and contains the target.

Back 40

anode

Front 41

The anode serves three functions in an x-ray tube _________, ________________, and _______________.

Back 41

electrical conductor, mechanical support, and thermal dissipator.

Front 42

_________, _________, and ________ are the most common anode materials.

Back 42

Copper, molybdenum, and graphite.

Front 43

Adequate ______________ is the major engineering hurdle in designing higher-capacity x-ray tubes.

Back 43

heat dissipation

Front 44

The _______ is the area of the anode struck by the electrons from the cathode.

Back 44

target

Front 45

In ____________ tubes, the target consists of a tungsten alloy embedded in the copper anode.

Back 45

stationary anode

Front 46

In ______________ tubes the enitre rotating disc is the target.

Back 46

rotating anode

Front 47

Tungsten is the material of choice for the target for general radiography for three main reasons _____________, ________________, and _______________.

Back 47

Atomic number, thermal conductivity, and high melting point.

Front 48

Specialty x-ray tubes for mammography have molybdenum or rhodium targets principally because of thier ________________ and _________________________.

Back 48

low atomic number and low k-characterisitc x-ray energy

Front 49

The ___________ x-ray tube allows the electron beam to interact with a much larger target area; therefore, the heating of the anode is not confined to one small spot, as in a stationary anode tube.

Back 49

rotating anode

Front 50

Most rotating anodes revolve at ________.

Back 50

3600 rpm

Front 51

The anodes of high-capacity tubes rotate at up to ___________.

Back 51

10,000 rpm

Front 52

An ________________________ is used to turn the anode.

Back 52

electromagnetic induction motor

Front 53

The part outside the enclosure, called the ________, consists of a series of electromagnets equally spaced around the neck of the tube.

Back 53

stator

Front 54

The rotating anode is powered by an _____________________.

Back 54

electromagnetic induction motor

Front 55

The ________ is the actual x-ray source.

Back 55

focal spot

Front 56

The _______________ results in an effective focal spot size much less than the acutal focal spot size.

Back 56

line-focus principle

Front 57

As the target angle ___________, so does the effective focal spot size.

Back 57

decreases

Front 58

The _________ the anode angle, the larger is the heel effect.

Back 58

smaller

Front 59

The __________ results in reduced x-ray intensity on the anode side of the useful beam caused by absorption in the "heel" of the target.

Back 59

heel effect

Front 60

The _________ results in smaller effective focal spot and less radiation intensity on the anode side of the x-ray beam.

Back 60

heel effect

Front 61

X-ray tubes are designed so that ___________ from the cathode interact with the target only at the focal spot.

Back 61

projectile electrons

Front 62

However, some of the electrons bounce off the __________ and then land on other areas of the target, causing x-rays to be produced from outside of the focal spot. These x-rays are called ______________.

Back 62

focal spot; off-focus radiation

Front 63

T/F With careful use, x-ray tubes can provide many years of service.

Back 63

True

Front 64

T/F With inconsiderate use, x-ray tube life may be shortened substantially.

Back 64

Ture

Front 65

The length of x-ray tube life is primarily under the control of the radiologic __________.

Back 65

technologist

Front 66

Basically, x-ray tube life is extended by using the minimum radiographic factors of ______, _______, and ______________ that are appropriate for each examination.

Back 66

mA, kVp, and exposure time

Front 67

The use of ________ image receptors results in longer tube life.

Back 67

faster

Front 68

X-ray tube failure has several causes, most of which are realated to the ____________ of the x-ray tube.

Back 68

thermal characteristics

Front 69

Enormous heat is generated in the _______ of the x-ray tube during the x-ray exposure.

Back 69

anode

Front 70

This heat can be dissipated in one of three ways ___________, ___________, or ___________.

Back 70

radiation, conduction, or convection

Front 71

_________ is the transfer of heat by the emission of infrared radiation.

Back 71

Radiation

Front 72

________ is the transfer of energy from one area of an object to another.

Back 72

Conduction

Front 73

___________ is the transfer of heat by the movement of heat by the movement of a heated substance from one place to another.

Back 73

Convection

Front 74

Excessive heat results in _________ x-ray tube life.

Back 74

reduced

Front 75

When the temperature of the anode is excessive during a single exposure, localized surface _________ and ______ of the anode can occur.

Back 75

melting; pitting

Front 76

If ______________ is sufficiently severe the tungsten can be vaporized and can plate the inside of the glass enclosure. This can cause filtering of the x-ray beam and interference with electron flow from ________ to __________.

Back 76

surface melting; cathode; anode

Front 77

Maximum radiographic techniques should never be applied to a _________ anode.

Back 77

cold

Front 78

The most frequent cause of abrupt tube failure is ___________ from filament to enclosure due to vaporized tungsten.

Back 78

electron arcing

Front 79

The radiologic technologist is guided in the use of x-ray tubes by ____________.

Back 79

x-ray tube rating charts

Front 80

Three types of x-ray tube rating charts are particularly significant to the radiologic technologist: _______________, ____________, and ____________.

Back 80

the radiographic rating chart, the anode cooling chart, and the housing cooling chart.

Front 81

Of the three rating charts, the ______________ is the most important because it conveys which radiographic techniques are safe and which techniques are unsafe for x-ray tube operation.

Back 81

radiographic rating chart

Front 82

Formula for Single Phase

Back 82

HU= kVp X mA x s

Front 83

Formual for Three-Phase/ High frequency

Back 83

HU= 1.4 X kVp X mA x s

Front 84

Formula for Three-phase six pulse

Back 84

1.35 X kVp X mA X s