1 X-ray Production

Question 1

The mass

Answer 1

–The mass of a body is a measure of its resistance to acceleration.
–Mass is measured in kilograms (kg).

Question 2

Velocity

Answer 2

–Velocity is the speed of a body moving in a given direction.
–Velocity is measured in meters per second (m/s).

Question 3

Acceleration

Answer 3

–Acceleration is the rate of change of velocity.

–Acceleration is measured in meters per second squared (m/s2).

Question 4

Force

Answer 4

–A force causes a body to deviate from a state of rest or constant velocity (push or pull).
–Force = mass × acceleration, measured in newtons (N).
–The four physical forces in the universe are gravitational, electrostatic, strong, and weak.

Question 5

The electrostatic force

Answer 5

–The electrostatic force causes protons and electrons to attract each other.
–Electrostatic forces hold atoms together.

Question 6

Strong forces

Answer 6

–Strong forces hold the nucleus together.

Question 7

Weak forces

Answer 7

–Weak forces are involved in beta decay.

Question 8

Energy

Answer 8

–Energy is the ability to do work.
–Energy is measured in joules (J).
–Energy (joule) = power (watt) × time (second)

Question 9

Einstein formula

Answer 9

–E = mc2 where E is energy, m is mass, and c is the velocity of light.

Question 10

Electric charge

Answer 10

–Electric charge of an electron (or proton) is 1.6 × 10–19 coulomb (C).

Question 11

Electric current

Answer 11

–Electric current, measured in amperes (A), is the flow of electrons through a circuit.
–An ampere is the amount of charge that flows divided by time.
–1 ampere = 1 coulomb per second

Question 12

Power

Answer 12

–Power is the rate of performing work.
–Power is the energy used divided by time, measured in watts (W).
–1 watt = 1 joule per second
–Power (watt) = current (ampere) × voltage (volt)

Question 13

A wave

Answer 13

–A wave is an entity that varies in space and time.

–Waves are characterized by a wavelength, frequency, and velocity.

Question 14

Wavelength (λ)

Answer 14

–Wavelength (λ) is the distance between successive crests of waves.
–Wavelengths are measured in meters (m).

Question 15

Frequency (f)

Answer 15

–Frequency (f) is the number of wave oscillations per unit of time.
–Frequencies are measured in cycles per second, where one cycle per second is equal
to one hertz (Hz).

Question 16

The wave period

Answer 16

–The wave period is the time required for one wavelength to pass.
–Wave period is 1/f.

Question 17

The wave velocity (v)

Answer 17

–The wave velocity (v) is the product of the wavelength and frequency, and measured in
meters per second (m/s).
–Velocity (m/s) = frequency (Hz) × wavelength (m)

Question 18

Electromagnetic radiation

Answer 18

–Electromagnetic radiation is a wave that is associated with oscillating electric and magnetic fields.
–The product of the wavelength (λ) and frequency (f) of electromagnetic radiation is equal to the speed of light (c = fλ).

Question 19

X-rays

Answer 19

–X-rays are a form of electromagnetic radiation.
–Low-frequency electromagnetic radiation has a long wavelength.
–High-frequency electromagnetic radiation has a short wavelength.

Question 20

Photons

Answer 20

–Electromagnetic radiation is quantized, meaning that it exists in discrete quantities called photons.
–Photons may behave as waves or particles but have no mass.
–Photon energy is E = h f = h (c/λ), where h is Plank’s constant.

Question 21

Generators consist of

Answer 21

–Generators consist of an input power supply, transformer, and rectification circuit.

Question 22

Single-phase generators used in

Answer 22

–Dental radiography where teeth are relatively thin and longer exposure times are tolerable (no moving parts).

Question 23

A transformer

Answer 23

–A transformer changes the size of the input voltage and is capable of producing high and low voltages.
–Np/Ns = Vp/Vs,

Question 24

Rectification

Answer 24

–Rectification changes the AC voltage into a DC voltage across the x-ray tube.
–Rectification is achieved using diodes, which permit current to flow in only one direction.

Question 25

Full-wave rectification

Answer 25

–Rectification for single-phase power supply normally uses four diodes.
–There are two pulses per cycle of 1/60 second.
–Each pulse ranges from zero volts to a peak (maximum) voltage.
–The maximum voltage is known as the kVp (p stands for peak).

Question 26

Voltage waveform

Answer 26

–Voltage waveform is a plot of voltage over time.

Question 27

The voltage waveform ripple

Answer 27

–The voltage waveform ripple is the maximum voltage minus the minimum voltage per cycle expressed as a percentage of the maximum voltage.
–Single-phase systems have 100% ripple.
–Three-phase 6-pulse systems have ∼13% ripple.
–Three-phase 12-pulse systems have ∼4% ripple.

Question 28

Excitation

Answer 28

–Excitation occurs when atomic electrons are energized to higher energy states.

Question 29

Ionization

Answer 29

–Ionization occurs when an atomic electron is removed from an atom.

Question 30

Bremsstrahlung

Answer 30

–Bremsstrahlung x-rays are produced when energetic electrons interact with nuclear electric fields.
–Bremsstrahlung means braking radiation.
–Bremsstrahlung x-ray production increases with increases in both the accelerating voltage (kV) and the atomic number (Z) of the target.

Question 31

Characteristic radiation

Answer 31

–Characteristic radiation is produced when target electrons are ejected by the incident energetic electrons.
–Only K-shell characteristic x-rays are important in diagnostic radiology.

Question 32

X-ray intensity increase by

Answer 32

–The number of x-ray photons.
– X-ray tube current.
– Exposure time.
– The tube current (mA) and exposure time (s) is known as the mAs.
– The x-ray tube voltage (kV)

Question 33

The filament

Answer 33

–The filament is the source of electrons that are accelerated toward the anode to produce x-rays.

Question 34

Space charge

Answer 34

–Electrons emitted from a heated filament form a negative cloud around the filament called a space charge, which prevents further emission of electrons.

Question 35

The tube current

Answer 35

–The tube current is the flow of electrons from the filament to the target embedded in the anode.

Question 36

Focal spots

Answer 36

–The area of the target struck by the electrons is determined by the filament size and focusing cup.
–The focal spot is the size of the source of x-rays as viewed by the patient.

Question 37

The anode angle

Answer 37

–The anode angle is the angle between the target surface and the central beam.
–Typical anode angles range from 7 degrees to 20 degrees.

Question 38

Anodes

Answer 38

–Electrons striking the target produce heat and x-rays.

–The target is embedded in an anode material, which temporarily stores the heat energy deposited into the target.