AIM: Ch 6: X-ray Production, X-ray Tubes, and X-ray Generators

Question 1

It supplies the power and permits selection of tube voltage, tube current, and exposure time.

Answer 1

X-ray generator

Question 2

X-ray tube voltage set for:
a. Diagnostic imaging
b. Mammography

Answer 2

a. 40 to 150 kV
b. 25 to 40 kV

Question 3

It is measured in milliamperes (mA), and is proportional to the number of electrons per second flowing from the cathode to the anode, where 1 mA = 6.24 x10^15 electrons/s

Answer 3

X-ray tube current

Question 4

Give the three major selectable parameters on the x-ray generator control panel that determine the x-ray beam characteristics.

Answer 4

kV, mA, exposure time

Voltage, current, and exposure time

Question 5

It is the negative electrode in the x-ray tube, and comprised of a filament or filaments and a focusing cup

Answer 5

Cathode

Question 6

T/F: Electrons flow from the cathode to the anode only when the tube voltage is applied between these electrodes.

Answer 6

True

Question 7

Emission-limited output means that the ____ determines the x-ray tube current

Answer 7

Filament current

Question 8

When energized, the filament circuit heats the filament through electrical resistance, and the process of ____ releases electrons from the filament surface at a rate determined by the filament current and corresponding filament temperature.

Answer 8

Thermionic emission

Question 9

As a large voltage is applied between the cathode and anode in the correct polarity, electrons are accelerated into a tight distribution and travel to the anode, striking a small area called the

Answer 9

Focal spot

The focal spot dimensions are determined by the length of the filament in one direction and the width of electron distribution in the perpendicular direction.

Question 10

T/F: The focal spot dimensions are determined by the length of the filament in one direction and the width of electron distribution in the perpendicular direction.

Answer 10

True

Question 11

For tube voltages 40 kV and lower, a space charge cloud shields the electric field so that further increases in filament current do not increase the tube current. This is known as ____

Answer 11

Space charge-limited

Question 12

A metal target electrode that is maintained at a large positive potential difference relative to the cathode

Answer 12

Anode

Question 13

To avoid heat damage to the x-ray tube, two factors must be limited

Answer 13

1. Rate of x-ray production (proportional to the tube current)
2. At large tube currents, the duration of x-ray production

Question 14

It is the most widely used anode material because of its high melting point and high atomic number.

Answer 14

Tungsten

An alloy of 10% rhenium and 90% tungsten provides added resistance to surface damage. Tungsten provides greater bremsstrahlung production than elements with lower atomic numbers

Question 15

Two anode materials in mammographic x-ray tubes

Answer 15

Molybdenum
Rhodium

Question 16

It contains the electron source and target within an evacuated glass or metal envelope

Answer 16

X-ray tube insert

Question 17

It provides protective radiation shielding and cools the x-ray tube insert

Answer 17

Tube housing

Question 18

It supplies the voltage to accelerate the electrons

Answer 18

X-ray generator

Question 19

They shape the x-ray energy spectrum

Answer 19

X-ray beam filters

Question 20

They define the size and shape of the x-ray field incident on the patient.

Answer 20

Collimators

Question 21

SI unit of potential difference is the ____

Answer 21

Volt, V

Question 22

For diagnostic radiology, a large electric potential difference of ____ is applied between two electrodes (the cathode and the anode) in the vacuum

Answer 22

20,000 to 150,000 V (20 to 150 kV)

Question 23

The cathode is the ____ of electrons, and the anode, with a positive potential with respect to the cathode, is the ____ of electrons.

Answer 23

source, target

Positive is Always the Target

Question 24

A common unit of energy is the ____, equal to the energy attained by an electron accelerated across a potential difference of 1 V.

Answer 24

Electron volt (eV)

Question 25

The vast majority of interactions are ____, whereby energy exchanges with electrons in the target give rise to heat.

Answer 25

Collisional

Question 26

Electrical (Coulombic) forces attract and decelerate an electron and change its direction, causing a loss of kinetic energy, which is emitted as an x-ray photon of equal energy called a

Answer 26

Bremsstrahlung radiation

Question 27

T/F: The amount of energy lost by the electron and thus the energy of the resulting x-ray are determined by the distance between the incident electron and the target nucleus, since the Coulombic force is proportional to the inverse of the square of the distance

Answer 27

True

Question 28

T/F: The probability of electron interactions that result in production of x-ray energy E is dependent on the radial interaction distance, r, from the nucleus, which defines a circumference, 2(pi)r.

Answer 28

True

Question 29

The ____ bremsstrahlung spectrum (Fig. 6-3A) shows an inverse linear relationship between the number and the energy of the x-rays produced, with the highest x-ray energy determined by the peak voltage (kV) applied across the x-ray tube.

Answer 29

Unfiltered

Question 30

A typical ____ bremsstrahlung spectrum (Fig. 6-3B) has no x-rays below about 10 keV; the numbers increase to a maximum at about one third to one half the maximal x-ray energy and then decrease to zero as the x-ray energy increases to the maximal x-ray energy.

Answer 30

Filtered

Filtration in this context refers to the removal of x-rays by attenuation in materials that are inherent in the x-ray tube (e.g., the glass window of the tube insert), as well as by materials that are purposefully placed in the beam, such as thin aluminum and copper sheets, to remove lower energy x-rays and adjust the spectrum for optimal low-dose imaging

Question 31

Give 2 major factors that affect x-ray production efficiency

Answer 31

1. Atomic number of the target material
2. Kinetic energy of the incident electrons

Question 32

What determines the energy of the incident electron?

Answer 32

Voltage applied to the x-ray tube

Question 33

T/F: A Kb x-ray is more energetic than a Ka x-ray.

Answer 33

True

Question 34

T/F: K-shell transitions are the only relevant transition in the image formation process

Answer 34

True

Characteristic x-rays other than those generated by K-shell transitions are too low in energy for any useful contributions to the image formation process and are undesirable for diagnostic imaging.

Question 35

T/F: Characteristic K x-rays are produced only when the electrons impinging on the target exceed the binding energy of a K-shell electron.

Answer 35

True

X-ray tube voltages must therefore be greater than 69.5 kV for W targets, 20 kV for Mo targets, and 23 kV for Rh targets to produce K characteristic x-rays.

Question 36

T/F: In terms of intensity, as the x-ray tube voltage increases, so does the ratio of characteristic to bremsstrahlung x-rays.

Answer 36

True

Question 37

It provides an environment for the production of bremsstrahlung and characteristic x-rays

Answer 37

X-ray tube

Question 38

Give the usual tube current for the following studies:
a. Continuous fluoroscopy
b. Pulsed fluoroscopy
b. Projection radiography

Answer 38

a. 1 to 5 mA
b. 10 to 50 mA
c. 50 to 1,200 mA

Question 39

T/F: Often, the product of the tube current and exposure time are considered as one entity, the mAs (milliampere-second; technically, mAs is a product of two units but, in common usage, it serves as a quantity)

Answer 39

True

Question 40

It is made of tungsten wire wound in a helix, and is electrically connected to the filament circuit, which provides a voltage of approximately 10 V and variable current up to 7,000 mA (7 A)

Answer 40

Filament

Question 41

T/F: At any kV, the x-ray flux is proportional to the tube current.

Answer 41

True

Question 42

T/F: Higher tube voltages also produce slightly higher tube current for a much higher filament current.

Answer 42

False

Higher tube voltages also produce slightly higher tube current for the same filament current.

Question 43

A ____ x-ray tube has a focusing cup totally insulated from the filament wires so that its voltage is independent of the filament.

Answer 43

biased

Isolation of the focusing cup from the filament and application of a negative bias voltage (−100 V) reduces electron distribution further by increasing the repelling electric fields surrounding the filament and modifying the electron trajectories

Question 44

A tube with a capability of applying greater negative applied voltage (about −4,000 V) to the focusing cup to stop the flow of electrons, and providing a means to rapidly switch the x-ray beam on and off is called

Answer 44

Grid biased or grid pulsed tube

Grid-biased x-ray tube switching is used by more expensive fluoroscopy systems for pulsed fluoroscopy and angiography to rapidly and precisely turn on and turn off the x-ray beam. This eliminates the build-up delay and turnoff lag of x-ray tubes switched at the generator, which cause motion artifacts and produce lower average x-ray energies and unnecessary patient dose.

Question 45

T/F: Electrons striking the anode deposit most of their energy as x-rays, with only a small fraction emitted as heat.

Answer 45

False

Electrons striking the anode deposit most of their energy as heat, with only a small fraction emitted as x-rays.

Question 46

Two components of a stationary anode

Answer 46

Tungsten insert
Copper block

However, the small area of the focal spot on the stationary anode limits the tube current and x-ray output that can be sustained without damage from excessive temperature.

Question 47

Stationary versus Rotating Anodes:
a. Dental x-ray units and some low-output mobile x-ray machines
b. Interventional fluoroscopy and CT
c. Mobile fluoroscopy

Answer 47

a. Stationary
b. Rotating
c. Stationary

Question 48

This anode configuration is used for most diagnostic x-ray applications, mainly because of greater heat loading and higher x-ray intensity output.

Answer 48

Rotating anodes

Question 49

T/F: A large focal spot, which permits high x-ray output and short exposure times, should be used in situations where motion is expected to be a problem and geometric magnification is small (the object is close to the image receptor).

Answer 49

True

Question 50

It is defined as the angle of the target surface with respect to the central ray (central axis) in the x-ray field

Answer 50

Anode angle

Question 51

Anode angles in diagnostic x-ray tubes typically range from ____ degrees, with ____-degree angles being most common

Answer 51

7 to 20, 12- to 15

Question 52

Give 3 major factors affected by the anode angle

Answer 52

1. Effective focal spot size
2. Tube output intensity, and
3. X-ray field coverage provided at a given focal spot to detector distance

Question 53

It is the area on the anode that is struck by electrons, and is primarily determined by the length of the cathode filament and the width of the focusing cup slot.

Answer 53

Actual focal spot

Question 54

T/F: The projected length of the focal spot area at the x-ray field central ray is much smaller, because of geometric foreshortening of the distribution from the anode surface.

Answer 54

True

Question 55

Foreshortening of the focal spot length at the central ray is called the ____.

Answer 55

Line focus principle

An ability to have a smaller effective focal spot size for a large actual focal spot increases the power loadings for smaller effective focal spot sizes

Question 56

T/F: As the anode angle decreases (approaches 0 degrees), the effective focal spot becomes smaller for the same actual focal area, providing lesser spatial resolution of the object when there is geometric image magnification.

Answer 56

False.

As the anode angle decreases (approaches 0 degrees), the effective focal spot becomes smaller for the same actual focal area, providing BETTER spatial resolution of the object when there is geometric image magnification.

Question 57

T/F: For larger actual focal areas, greater x-ray output intensity with shorter exposure times is not possible.

Answer 57

False

For larger actual focal areas, greater x-ray output intensity with shorter exposure times IS possible.

Question 58

Given a large anode angle and long filament length, describe the following
a. Field coverage
b. Effective focal spot
c. Power loading
d. Disadvantages: (2)

Answer 58

a. Large
b. Large
c. Good
d. Geometric blurring and image degradation

Question 59

T/F: The effective focal spot length varies with the position in the image plane, in the anode-cathode (A–C) direction. Toward the anode side of the field, the projected length of the focal spot shortens, whereas it lengthens towards the cathode side of the field

Answer 59

True

Question 60

It uses a very small circular aperture (10 to 30 mm diameter) in a thin, highly attenuating metal (e.g., lead, tungsten, or gold) disk to project a magnified image of the focal spot onto an image receptor. Positioned on the central axis between the x-ray source and detector, an image of the focal spot is recorded.

Answer 60

Pinhole camera

Question 61

It consists of a highly attenuating metal (usually tungsten) plate with a thin slit, typically 10 mm wide. In use, this device is positioned above the image receptor, with the center of the slit on the central axis, and with the slit either parallel or perpendicular to the A-C axis.

Answer 61

Slit camera

Question 62

It contains a radial pattern of lead spokes of diminishing width and spacing on a thin plastic disk

Answer 62

Star pattern test tool

Question 63

It is a simple tool for evaluation of focal spot size wherein the images demonstrate the effective resolution parallel and perpendicular to the A-C axis for a given magnification geometry, determined from the number of the bar pattern that can be resolved.

Answer 63

Resolution bar pattern

Question 64

It is an increase in the size of the focal spot resulting from high tube current (mA), and is caused by electron repulsion in the electron beam between the cathode and anode.

Answer 64

Focal spot “blooming”

It is most pronounced at LOW kVs

Question 65

It is a slight decrease in the measured size with increasing kV (electron repulsion and spreading in the x-ray tube is reduced)

Answer 65

Focal spot “thinning”

Question 66

It refers to a reduction in the x-ray beam intensity toward the anode side of the x-ray field, caused by the greater attenuation of x-rays directed toward the anode side of the field by the anode itself

Answer 66

Heel effect

Question 67

T/F: The heel effect is less prominent with a shorter source-to-image distance (SID)

Answer 67

False

The heel effect is less prominent with a LONGER source-to-image distance (SID)

The L in HeeL is for less and longer

Question 68

It results from electrons that scatter from the anode, and are re-accelerated back to the anode, outside of the focal spot area. These electrons cause low-intensity x-ray emission over the entire face of the anode, increasing patient exposure, causing geometric blurring, reducing image contrast, and increasing random noise.

Answer 68

Off-focal radiation

Question 69

It contains the cathode, anode, rotor assembly, and support structures sealed in a glass or metal enclosure under a high vacuum.

Answer 69

X-ray tube insert

Question 70

This is used to trap gas in the insert and to maintain the vacuum.

Answer 70

“Getter” circuit

Question 71

Mammography tubes use ____ in the port to minimize absorption of the low-energy x-rays used in mammography.

Answer 71

Beryllium (Z = 4)

Question 72

This supports, insulates, and protects the x-ray tube insert from the environment.

Answer 72

X-ray tube housing

Question 73

Lead shielding inside the housing attenuates nearly all x-rays that are not directed to the tube port. A small fraction of these x-rays, known as ____, penetrates the housing.

Answer 73

Leakage radiation

Question 74

Federal regulations (21 CFR 1020.31) require that the light field and x-ray field be aligned so that the sum of the misalignments, along either the length or the width of the field, is within ____ of the SID.

Answer 74

2%

Question 75

This automatically limit the field size to the useful area of the detector.

Answer 75

Positive beam limitation (PBL) collimators

Adjustment to a smaller field area is possible; however, a larger field area requires disabling the PBL circuit

Question 76

It has a focusing cup that is electrically isolated from the cathode filament and maintained at a more negative voltage. When the bias voltage is sufficiently large, the resulting electric field stops the tube current.

Answer 76

Grid-biased tube

Question 77

Grid biasing requires approximately ____ applied to the focusing cup with respect to the filament to switch the x-ray tube current off

Answer 77

−4,000 V

Question 78

The following include the main differences between a dedicated mammography tube and a conventional x-ray tube:
a. Target materials (molybdenum, rhodium, and tungsten)
b. Output port (beryllium versus glass or metal insert material)
c. Smaller effective focal spot sizes (typically 0.3 and 0.1 mm nominal focal spot sizes)
d. Use of grounded anodes
e. All of the above

Answer 78

e. All of the above

Question 79

In an advanced CT x-ray tube, circulating oil rapidly removes excess heat from the anode. The electron beam can be rapidly deflected between two focal spots; this is known as a ____

Answer 79

Flying focal spot

Question 80

The following maximizes x-ray tube life, except:
a. Minimize filament boost “prep” time (the first detent of two on the x-ray exposure switch) especially when high mA is used
b. Use higher tube current with shorter exposure times to arrive at the desired mAs if possible
c. Avoid extended or repeated operation of the x-ray tube with high technique (kV and mAs) factors
d. Always follow the manufacturer’s recommended warm-up procedure.
e. Limit rotor start and stop operations
f. All of the above maximizes x-ray tube life

Answer 80

b. Use LOWER tube current with LONGER exposure times to arrive at the desired mAs if possible

Question 81

It is the removal of x-rays as the beam passes through a layer of material.

Answer 81

Filtration

Question 82

Inherent filtration includes the thickness of ____ of the glass or metal insert at the x-ray tube port.

Answer 82

1 to 2 mm

Question 83

Glass (primarily ____) and aluminum have similar attenuation properties and effectively attenuate all x-rays in the spectrum below about ____

Answer 83

Silicon dioxide, SiO2
15 keV

Question 84

Inherent filtration includes the following, except:
a. Inherent filtration includes the thickness (1 to 2 mm) of the glass or metal insert at the x-ray tube port.
b. Attenuation by housing oil
c. Field light mirror in the collimator assembly
d. All of the above
e. None of the above

Answer 84

d. All of the above are part of inherent filtration

Question 85

It refers to sheets of metal intentionally placed in the beam to change its effective energy

Answer 85

Added filtration

Question 86

It is the most commonly used added filter material

Answer 86

Aluminum (Al)

Question 87

They are used to change the spatial pattern of the x-ray intensity incident on the patient, so as to deliver a more uniform x-ray exposure to the detector.

Answer 87

Compensation (equalization) filters

Question 88

These are useful for lateral projections in cervical-thoracic spine imaging, where the incident fluence is increased to match the increased tissue thickness encountered (e.g., to provide a low incident flux to the thin neck area and a high incident flux to the thick shoulders)

Answer 88

Wedge filters

Question 89

These are used in CT to reduce dose to the periphery of the patient, where x-ray paths are shorter and fewer x-rays are required.

Answer 89

Bow-tie filters

Question 90

Transformers are principal components of x-ray generators; they convert low voltage into high voltage through a process called ____. It is a phenomenon in which a changing magnetic field induces an electrical potential difference (voltage) in a nearby conductor and also in which a voltage is induced in a conductor moving through a stationary magnetic field.

Answer 90

Electromagnetic induction

Electrical power available to a hospital or clinic provides up to about 480 V, much lower than the 20,000 to 150,000 V needed for x-ray production.

Question 91

T/F: The magnitude of the induced voltage is proportional to the rate of change of the magnetic field strength.

Answer 91

True

Question 92

T/F: Electrical current, such as the electrons flowing through a wire, produces a magnetic field whose magnitude (strength) is proportional to the magnitude of the current

Answer 92

True

Question 93

T/F: For a coiled wire geometry, superimposition of the magnetic fields from adjacent turns of the wire decreases the amplitude of the overall magnetic field (the magnetic fields penetrate the wire’s insulation), and therefore the magnetic field strength is inversely proportional to the number of wire turns.

Answer 93

False

For a coiled wire geometry, superimposition of the magnetic fields from adjacent turns of the wire increases the amplitude of the overall magnetic field (the magnetic fields penetrate the wire’s insulation), and therefore the magnetic field strength is proportional to the number of wire turns.

Question 94

What kind of transformer circuit is used in a diagnostic x-ray generator?

Answer 94

Step-up transformer circuit

Based on the Law of Transformers,
For Ns > Np, a “step-up” transformer increases the secondary voltage
For Ns < Np, a “step-down” transformer decreases the secondary voltage
For Ns = Np, an “isolation” transformer produces a secondary voltage equal to the primary voltage

Question 95

A basic electrical component known as a ____ will allow current to flow in one direction only

Answer 95

Rectifier

Question 96

A ____ is a device with two terminals. When a voltage is applied between the terminals with a specific polarity, there is very little resistance and a large current flows; when the same voltage is applied with the opposite polarity, little or no current flows.

Answer 96

Diode

Question 97

Clever use of diodes arranged in a ____ can route the flow of electrons through an AC circuit to create a direct current (DC), a unidirectional movement of electrons in which the voltage polarity never reverses.

Answer 97

Bridge rectifier circuit

Question 98

It is the rate of energy production or expenditure per unit time

Answer 98

Power

Question 99

SI unit of power

Answer 99

Watt = J/s

Question 100

For electrical devices, power is equal to the product of ____

Answer 100

Voltage and current

Question 101

In an operator console, if this is used, exposure time is not set

Answer 101

Automatic exposure control (AEC) circuit

Question 102

The focal spot size (i.e., large or small) is usually determined by the ____

Answer 102

mA setting

Question 103

Generator design which is now the contemporary state-of-the-art choice for diagnostic x-ray systems. This uses a high frequency alternating waveform (up to 50,000 Hz) for efficient conversion of low to high voltage by a step-up transformer.

Answer 103

High-frequency x-ray generator

Question 104

It measures the difference between the reference voltage (a calibrated value proportional to the requested kV) and the actual kV measured across the tube by a voltage divider (the kV sense circuit)

Answer 104

Voltage comparator

Question 105

The mA is regulated in an analogous manner to the kV, with a ____ sensing the actual mA (the voltage across a resistor is proportional to the current) and comparing it with a reference voltage.

Answer 105

Resistor circuit

Question 106

In an electronic waveform, ____ is defined as the difference between the peak voltage and the minimum voltage, divided by the peak voltage and multiplied by 100%:

Answer 106

Voltage ripple

High-frequency generators have a ripple that is kV and mA dependent

Question 107

It is used as a safety mechanism to terminate the exposure in the event of an exposure switch or timer failure.

Answer 107

Countdown or backup timer

Question 108

Fastest switching method, with minimal turn-on–turnoff “lag”

Answer 108

Grid-controlled x-ray tube

Question 109

It is often used instead of manual exposure time settings in radiography; which measures the actual amount of radiation incident on the image receptor (i.e., screen-film or digital radiography detector) and terminate x-ray production when the proper radiation exposure is obtained.

Answer 109

Phototimer, also known as the automatic exposure control (AEC) system

Question 110

It is the maximal power that an x-ray tube focal spot can accept or the generator can deliver.

Answer 110

Power rating of an x-ray tube or generator

Question 111

It is a traditional unit that provides a simple way of expressing the energy deposition on and dissipation from the anode of an x-ray tube

Answer 111

Heat unit

Question 112

For three-phase, high-frequency, and constantpotential generators, because of their lower voltage ripple and higher average voltage, a multiplicative factor of ____ compensates for this difference in the HU equation below

Answer 112

1.35 to 1.40

Question 113

It is the SI unit of energy

Answer 113

Joule (J)

The energy, in joules, deposited in the anode is calculated as follows:

Question 114

It is the constant voltage that would deliver the same power as a varying voltage waveform (e.g., for a single phase generator)

Answer 114

Root-mean-square voltage, VRMS

Question 115

It shows the anode heat loading for various input powers (kW or HU/s) as the x-ray tube is operating, taking into account the cooling that simultaneously occurs.

Answer 115

Anode heating and cooling chart

Question 116

With larger anode heat capacities, the anode cooling curve is steeper because higher temperatures result in more rapid cooling (also known as the ____, where the radiative cooling rate is proportional to T4, for absolute temperature T)

Answer 116

“Black-body” effect

Question 117

Quality, quantity, and exposure of x-ray tube output:

It describes the penetrability of an x-ray beam

Answer 117

Quality

With higher energy x-ray photons having a larger half-value layer (HVL) and higher “quality.”

Question 118

Quality, quantity, and exposure of x-ray tube output:

It refers to the number of photons comprising the beam

Answer 118

Quantity

Question 119

Quality, quantity, and exposure of x-ray tube output:

It is nearly proportional to the energy fluence of the x-ray beam.

Answer 119

Exposure

Question 120

Factors affecting x-ray emission:

It affects the efficiency of bremsstrahlung radiation production, with output exposure roughly proportional to atomic number. It also affects the quantity of bremsstrahlung photons and the quality of the characteristic radiation.

Answer 120

Anode target material

Question 121

Factors affecting x-ray emission:

It determines the maximum energy in the bremsstrahlung spectrum and affects the quality of the output spectrum. In addition, the efficiency of x-ray production is directly related to this factor.

Answer 121

Tube voltage (kV)

Exposure is approximately proportional to the square of the kV in the diagnostic energy range.

Question 122

Factors affecting x-ray emission:

T/F: An increase in kV increases the efficiency of x-ray production and the quantity and quality of the x-ray beam.

Answer 122

True

Changes in the kV must be compensated by corresponding changes in mAs to maintain the same exposure.

Question 123

Factors affecting x-ray emission:

It is proportional to the number of electrons flowing from the cathode to the anode per unit time.

Answer 123

Tube current (mA)

The quantity of x-rays is directly proportional to the product of tube current and exposure time (mAs), as shown in Figure 6-31.

Question 124

T/F: The exposure of the beam for a given kV and filtration is proportional to the tube current.

Answer 124

True

Question 125

Factors affecting x-ray emission:

This modifies the quantity and quality of the x-ray beam by preferentially removing the low-energy photons in the spectrum. This reduces the number of photons (quantity) and increases the average energy, also increasing the quality

Answer 125

Beam filtration

Question 126

T/F: It is not necessary to know the HVL of the beam and the normalized x-ray tube intensity per mAs (in addition to the geometry) to calculate the incident exposure and radiation dose to the patient. One simply uses kV and mAs for determining the “proper technique” or to estimate the dose to the patient without this information.

Answer 126

False

It is necessary to know the HVL of the beam and the normalized x-ray tube intensity per mAs (in addition to the geometry) to calculate the incident exposure and radiation dose to the patient. One cannot simply use kV and mAs for determining the “proper technique” or to estimate the dose to the patient without this information.

Question 127

Factors affecting x-ray emission:

It affects the quality of the emitted x-ray spectrum

Answer 127

Generator waveform

Both the quality and quantity of the x-ray spectrum are affected

Question 128

Factors affecting x-ray emission:

T/F: The x-ray quality is approximately proportional to Ztarget x kV^2 x mAs.

Answer 128

False

The x-ray QUANTITY is approximately proportional to Ztarget x kV^2 x mAs.

Question 129

T/F: The x-ray quality depends on the kV, the generator waveform, and the tube filtration.

Answer 129

True

Question 130

T/F: Exposure is independent from both the quantity and quality of the x-ray beam

Answer 130

False

Exposure depends on both the quantity and quality of the x-ray beam

Question 131

Compensation for changes in kV with radiographic techniques requires adjustments of mAs on the order of the fourth to fifth power of the kV ratio, because kV determines quantity, quality, and transmission through the object, whereas mAs determines ____ only.

Answer 131

Quantity