Deck 24: Diagnostic X-Ray Imaging

Question 1

As the angle in Compton scattering increases, what happens to the frequency of a scattered X-ray photon?

A)It increases.
B)It decreases.
C)It remains the same.
D)This depends on the atom.

Answer 1

It increases.

Question 2

What happens to the energy of an X-ray photon in the photoelectric effect?

A)The entire energy of the incident photon is transferred to an electron, and the electron is ejected from the atom.
B)A fraction of the incident photon's energy is transferred to an electron, and the photon scatters with lower energy.
C)There is no change in energy of the incident X-ray photon.
D)The entire energy of the incident photon is transferred to an atom, and all its electrons start to oscillate together.

Answer 2

The entire energy of the incident photon is transferred to an electron, and the electron is ejected from the atom.

Question 3

Which of the following processes is exclusively a scattering process?

A)Rayleigh scattering
B)photoelectric effect
C)Compton scattering
D)interaction of an X-ray with a valence electron

Answer 3

Rayleigh scattering

Question 4

The half-value layer (HVL) is the thickness of a tissue that absorbs 50% of an incident beam of X-rays. How much of the incident beam is absorbed in two HVL?

A)60%
B)75%
C)85%
D)100%

Question 5

In medical diagnostics, the energies of X-rays are less than 1 MeV. Which of these pairs of effects contribute most to the total attenuation of an X-ray beam that penetrates tissue?

A)the photoelectric effect and Compton scattering
B)pair production and the photoelectric effect
C)pair production and Compton scattering
D)Compton scattering and Rayleigh scattering

Question 6

If the thickness of tissue needed to absorb 75% of an incident X-ray beam is 0.8 cm, what is the linear attenuation coefficient in the tissue?

A)0.9 cm^-1
B)1.2 cm^-1
C)1.4 cm^-1
D)1.7 cm^-1

Question 7

The bremsstrahlung spectrum is the range of X-ray energies from 1 keV to 100 keV. Which of the following is the relationship between X-rays and energy?

A)The shortest wavelength of X-rays in this range correspond to 1 keV energy.
B)The longest wavelength of X-rays in this range correspond to 1 keV energy.
C)The highest frequency of X-rays in this range correspond to 1 keV energy.
D)The highest speed of X-rays in this range correspond to 1 keV energy.

Question 8

In which of these ways do X-rays compare with other waves in the electromagnetic spectrum?

A)They have a longer wavelength than ultraviolet light.
B)They have a higher frequency than ã-rays.
C)They have lower energy than radio waves.
D)They have higher energy than ultraviolet light.

Question 9

The bremsstrahlung spectrum is the range of X-ray energies from 1 keV to 100 keV. What is the ratio of the wavelength corresponding to 1 keV to the wavelength corresponding to 100 keV?

A)100
B)10
C)1/10
D)1/100

Question 10

Assume that the equation E_{photon, f} = (E_{photon, i})/[ 1 + (E_{photon, i}/m_ec²)(1 - cosè)] can be applied to all scattering angles è. When Compton scattering occurs, what is the E_{photon, i} scattering angle when the final energy of a scattered photon differs the most from the photon's initial energy?

A)0°
B)90°
C)180°
D)270°

Question 11

The Bremsstrahlung spectrum is the range of X-ray energies from 1 keV to 100 keV. What is the ratio of the lowest to the highest frequency of that spectrum?

A)100
B)10
C)1/10
D)1/100

Question 12

As the angle in Compton scattering increases, what happens to the energy of a scattered X-ray photon?

A)It increases.
B)It decreases.
C)It remains the same.
D)This depends on the atom.

Question 13

How do X-rays behave in Rayleigh scattering?

A)like photons
B)like waves
C)like photons or waves, depending on the energy level
D)like particles

Question 14

The gamma rays used in radiation treatment of cancer have a frequency of 2.83 × 10²⁰ Hz. What is their wavelength?

A)1.06 × 10^-12 m
B)1.06 × 10^-15 m
C)8.21 × 10^-25 m
D)8.21 × 10^-28 m

Question 15

In which of the following events are X-rays regarded as waves?

A)Rayleigh scattering
B)photoelectric effect
C)Compton scattering
D)interaction with a valence electron

Question 16

As the angle in Compton scattering increases, what happens to the wavelength of a scattered X-ray photon?

A)It increases.
B)It decreases.
C)It remains the same.
D)This depends on the atom.

Question 17

Which of the following processes is exclusively an absorption process?

A)Rayleigh scattering
B)photoelectric effect
C)Compton scattering
D)interaction of an X-ray with an entire atom

Question 18

Assume that the equation E_{photon, f} = [E_{photon, i})/[1 + (E_{photon, i}/m_ec²)(1 - cosè)] can be applied to all scattering angles è. When Compton scattering occurs, what is the scattering angle when the final frequency of a scattered photon differs the least from the initial frequency?

A)0°
B)90°
C)180°
D)270°

Question 19

Which of these changes occurs in X-rays due to Rayleigh scattering?

A)increase in wavelength
B)increase in frequency
C)increase in energy
D)no change in energy, frequency, or wavelength

Question 20

If the thickness of tissue needed to transmit 25% of an incident X-ray beam is 0.8 cm, what is the linear attenuation coefficient in the tissue?

A)0.9 cm^-1
B)1.2 cm^-1
C)1.4 cm^-1
D)1.7 cm^-1

Question 21

Iodine is used as a contrast agent in angiography because it has much higher photoelectric absorption probability than tissues surrounding blood vessels.

Question 22

In high kilovoltage radiography, X-rays of f = 3.6 × 10¹⁹ Hz are used. What is the energy in electronvolts?

Question 23

Compared to UV radiation, X-rays are

A)more hazardous for living tissue because of higher energy and higher penetration depth.
B)more hazardous for living tissue because of higher amplitude of the wave.
C)less hazardous for living tissue because of lower energy and shorter penetration depth.
D)our greater concern because Earth's atmosphere absorbs most of the UV coming from the Sun, but not X-rays.

Question 24

The electron volt is a unit of voltage.

Question 25

As the energy of incoming X-rays increases, the probability of the photoelectric effect and Compton scattering decreases. However, at energies above 1.02 MeV, another effect, pair production, takes place. Briefly explain the process of pair production.

Question 26

Compton scattering of a photon and an electron can be regarded as an elastic collision.

Question 27

Contrast in X-ray images is the difference between the number of X-ray photons from the initial beam and the number that reach the film.

Question 28

What is the unit that shows the amount of radiation energy deposited per kilogram of matter?

A)gray
B)curie
C)becquerel
D)joule

Question 29

Contrast in X-ray imaging does NOT depend on

A)the sample thickness.
B)the sample density.
C)the mass attenuation coefficient.
D)the frequency of the X-ray photons.

Question 30

Atomic structure can be probed with electromagnetic waves that have wavelengths of the order of the size of an atom. If Bohr's radius of the hydrogen atom is 0.05 nm, what is the frequency and energy (in electronvolts) of a wave suitable for exploring the atom? What kind of electromagnetic waves are those?

Question 31

In the photoelectric effect, the kinetic energy of ejected electrons depends on the intensity of the electromagnetic beam.

Question 32

The photoelectric effect is regarded as an elastic collision of a photon and an electron.

Question 33

X-rays are photons of energy e > 1 keV that originate from atomic transitions of electrons in inner shells.

Question 34

In Rayleigh scattering, the X-ray is regarded as a particle.

Question 35

X-ray photons have the highest energies in the electromagnetic spectrum.

Question 36

In mammography, X-ray photons of energy 25 keV are used. What is the wavelength of the corresponding wave?

Question 37

X-rays are electric and magnetic fields oscillating perpendicular to each other.

Question 38

In Compton scattering, the X-ray is regarded as a particle.

Question 39

A beam of X-rays of wavelength ë = 5.0 × 10^-11 m is scattered off valence electrons at an angle of 18° with respect to the incident beam. What is the final energy of the beam?

Question 40

The photoelectric effect, combined with Rayleigh scattering and Compton scattering, contributes to loss of image quality.

Question 41

Figure 24.1 Anterior chest X-ray of a normal, middle-aged, female subject.
Discuss briefly the dependence of the colour of various media in Fig. 24.1 on photoelectric absorption.

Question 42

Angiography is a technique of visualizing the structure of blood vessels by intravenously administering a contrast agent. Discuss briefly the use of iodine (atomic number Z = 53) as a contrast agent in angiography.

Question 43

What thickness of muscle will stop 75% of an incident 500 keV X-ray beam with a mass attenuation coefficient of ì = 0.224 cm^-1?

Question 44

X-ray photons of energy 25 keV are used in mammography. If the linear attenuation coefficient in a soft tissue is ì = 0.4 cm^-1, what fraction of an initial X-ray beam is absorbed by tissue that is 3 cm thick?

Question 45

Discuss briefly the exposure of humans to X-rays from the Sun considering Earth's surface and the upper atmosphere.

Question 46

What thickness of bone will stop half an incident 30 keV X-ray beam with a mass attenuation coefficient of ì = 0.953 cm^-1?

Question 47

If X-ray photons of energy 50 keV are used, and the linear attenuation coefficient in fat tissue is ì = 0.193 cm^-1, what fraction of an initial X-ray beam is transmitted in tissue that is 4 cm thick?

Question 48

As the energy of incoming X-rays increases, the probability of the photoelectric effect and Compton scattering decreases. However, at energies above 1.02 MeV another effect, pair production, takes place. Why does pair production NOT play any role in X-ray diagnostics, but only in radiotherapy?