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Radiation Protection > Week 3 > Flashcards

Week 3 Flashcards

1
Q

What are the consequences of x-ray interactions with human tissue?

A

X-ray interactions can lead to absorption, scattering, and potential biological damage.

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2
Q

Explain the Auger effect in x-ray interactions.

A

The Auger effect involves the emission of an electron from an atom after internal photoelectric absorption.

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3
Q

Define peak kilovoltage (kVp) and its influence on x-ray imaging.

A

kVp is the highest energy level of photons in the x-ray beam, controlling the beams penetrating power.

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4
Q

How does beam energy affect x-ray imaging?

A

Beam energy affects the penetration ability of x-rays. Higher energy increases penetration; lower energy leads to more absorption.

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5
Q

What are the different processes of x-ray interaction with matter?

A

Coherent scattering, photoelectric absorption, Compton scattering, pair production, and photodisintegration.

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6
Q

What is milliampere-seconds (mAs) and how does it control x-ray quantity?

A

mAs is the product of tube current (mA) and exposure time (seconds), controlling the total amount of radiation used.

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7
Q

How does attenuation affect an x-ray beam?

A

Attenuation is the reduction in intensity of the x-ray beam due to absorption and scattering.

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8
Q

What happens during pair production in x-ray interactions?

A

Pair production occurs when a high-energy photon converts into an electron-positron pair near a nucleus.

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9
Q

Why is absorption important for creating diagnostic images?

A

Absorption differences allow for contrast between various body structures, essential for diagnostic images.

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10
Q

How can a radiographer control patient dose during imaging?

A

By selecting appropriate exposure factors such as kVp and mAs to minimize patient dose while maintaining image quality.

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11
Q

What is photodisintegration and in what scenarios does it occur?

A

Photodisintegration involves a photon causing atomic nucleus disintegration, occurring at very high photon energies.

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12
Q

Describe direct transmission of x-ray photons in imaging.

A

Direct transmission occurs when photons pass through the patient without interacting and reach the image receptor.

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13
Q

What is the photoelectric interaction and its significance?

A

Photoelectric interaction involves photon absorption by an atom, resulting in electron ejection. Its significant for image contrast.

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14
Q

What is coherent scattering and when does it occur?

A

Coherent scattering involves low-energy photons scattering without energy loss, occurring typically under 10 KeV.

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15
Q

What is absorption in the context of x-ray interaction with matter?

A

Absorption is the transfer of photon energy to the atoms of the tissue, where the photon ceases to exist.

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16
Q

How can scatter radiation be minimized in x-ray imaging?

A

Using collimators and grids can reduce scatter radiation, minimizing fog and improving image quality.

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17
Q

What is the process of x-ray beam production?

A

A diagnostic x-ray beam is produced when high-speed electrons bombard a positively charged target in an x-ray tube.

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18
Q

What factors determine the probability of x-ray interaction with matter?

A

Factors include photon energy and the atomic composition of the material.

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19
Q

How do different materials affect x-ray beam attenuation?

A

Materials with higher atomic numbers have greater attenuation, influencing image contrast and quality.

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20
Q

How do primary, exit, and attenuated photons differ during an x-ray procedure?

A

Primary photons originate from the x-ray source, exit photons pass through the patient and reach the receptor, and attenuated photons are absorbed or scattered.

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21
Q

How does Compton scattering differ from coherent scattering?

A

Compton scattering involves energy loss and occurs with higher energy photons compared to coherent scattering.

22
Q

How does x-ray interaction affect image quality?

A

X-ray interactions like absorption and scattering affect image contrast and sharpness.

23
Q

What role does scattering play in radiographic fog?

A

Scattering, especially small-angle scatter, contributes to radiographic fog, reducing image clarity.

24
Q

Define primary radiation in the context of x-ray production.

A

Primary radiation consists of photons emitted directly from the x-ray tube target, having a range of energies.

25
Q

What is the importance of understanding beam energy in radiology?

A

Understanding beam energy helps in selecting exposure factors for optimal image quality and minimal patient dose.

26
Q

What is the impact of body part thickness on photoelectric absorption?

A

Thicker body parts result in more absorption; however, thickness inversely affects absorption when comparing tissues of different densities.

27
Q

What is beta positive emission and how is it related to antimatter?

A

Beta positive emission is the emission of a positron, which is the antimatter counterpart of an electron. Positrons are used in PET scanning.

28
Q

How does the effective atomic number (Z) affect photoelectric absorption?

A

Photoelectric absorption increases with the cube of the effective atomic number (Z^3), making it more likely in tissues with higher Z.

29
Q

How does photoelectric absorption contribute to radiographic contrast?

A

Greater differences in photoelectric absorption cause greater contrast in radiographic images due to differential absorption based on effective atomic number.

30
Q

What is pair production and at what photon energy does it occur?

A

Pair production occurs when a photon with energy greater than 1.022 MeV interacts with an atomic nucleus to produce a positron and a negatron.

31
Q

What is coherent scattering and at what photon energy range does it occur?

A

Coherent scattering is a type of interaction where the photon excites the entire atom, causing the emitted photon to have the same energy as the incident photon. It occurs in the photon energy range of 1-50 kVp.

32
Q

Explain the role of contrast media in enhancing radiographic images.

A

Contrast media are used to increase differences in effective atomic number and mass density between tissues for better visualization in radiographic images.

33
Q

Explain the interaction process involved in pair production.

A

A photon with over 1.02 MeV energy is completely absorbed, creating an electron-positron pair. The positron subsequently annihilates with an electron, releasing two 0.511 MeV photons.

34
Q

Describe the importance and effects of Compton scattering on imaging.

A

Compton scattering can reduce image quality by producing scatter fog. It occurs when an x-ray photon interacts with an outer shell electron, imparting energy and changing direction.

35
Q

How does photon energy influence the probability of different interaction types?

A

Higher photon energy decreases the likelihood of coherent and photoelectric interactions, but increases Compton scattering, pair production, and photodisintegration probabilities.

36
Q

What factors influence the likelihood of coherent scattering?

A

The likelihood of coherent scattering depends on photon energy (decreases with increasing energy) and mass density (increases with increasing mass density).

37
Q

What are the primary considerations for ensuring patient safety in radiographic imaging?

A

To ensure safety, use the highest-energy x-ray beam that provides adequate contrast while minimizing patient exposure.

38
Q

Why is pair production not significant in diagnostic imaging?

A

Pair production occurs at energy levels higher than those used in diagnostic imaging, as it requires photon energies greater than 1.022 MeV.

39
Q

What is annihilation radiation and how is it related to positron emission tomography (PET)?

A

Annihilation radiation arises when a positron and an electron annihilate, producing two 0.511 MeV photons. PET scans detect these photons to image metabolic processes.

40
Q

Describe the process of positron decay used in PET scanning.

A

In PET scanning, radioactive isotopes decay by emitting positrons, which then interact with electrons to produce detectable annihilation radiation for imaging.

41
Q

What is the significance of using both positive and negative contrast media?

A

Positive contrast media (white) and negative contrast media (black) enhance the differences in tissue density and effective atomic number, aiding in visualization.

42
Q

Explain the conditions and importance of photodisintegration in medical physics.

A

Photodisintegration occurs with photon energies above 10 MeV in high-energy radiation therapy, changing or breaking apart atomic nuclei.

43
Q

Describe the conditions under which the Auger effect occurs.

A

The Auger effect occurs when a photoelectron ejection creates an inner shell vacancy that is filled without releasing a characteristic photon, instead ejecting an Auger electron.

44
Q

Why is the emitted photons energy the same as the incident photon in coherent scattering?

A

In coherent scattering, no energy is absorbed by the atom, so the emitted photons energy remains the same as the incident photon.

45
Q

Describe the process of photoelectric absorption in diagnostic radiology.

A

In photoelectric absorption, an x-ray photon completely transfers its energy to an inner-shell electron, causing its ejection as a photoelectron and leading to ionization.

46
Q

In which circumstances is photodisintegration significant, if at all?

A

Photodisintegration is not significant in diagnostic imaging, but relevant in high-energy situations like radiation therapy.

47
Q

What is the process of Compton scattering in relation to photon energy?

A

Compton scattering occurs with moderate to high photon energies, involving interaction with outer orbital electrons and producing scattered photons with lower energy.

48
Q

What is the relationship between photon energy and the probability of photoelectric absorption?

A

Photoelectric absorption probability is inversely proportional to the cube of the photon energy (1/keV^3).

49
Q

What are the by-products of photoelectric absorption?

A

The by-products are a photoelectron and one or more characteristic photons.

50
Q

How does mass density affect Compton scattering probability?

A

Compton scattering probability increases with mass density.

Radiation Protection (15 decks)

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