Ch. 10 X-ray Imaging

As the x-ray energy increases, the wavelength of the x-rays becomes shorter. This is because energy and wavelength are inversely proportional. Higher energy means shorter wavelength, while lower energy means longer wavelength. Therefore, the correct answer is "shorter".

Lungs are imaged on a chest radiograph primarily because of differences in mass density. This is because the lungs have a lower mass density compared to other structures in the chest, such as the bones and organs. X-rays are able to differentiate between tissues of different mass densities, allowing the lungs to be visualized on the radiograph. Image quality and image quantity are not the primary reasons for imaging the lungs on a chest radiograph.

The given statement describes the photoelectric effect. In the photoelectric effect, an x-ray photon interacts with an inner-shell electron, transferring all its energy to the electron. This causes the electron to be ejected from the atom, and the x-ray photon is completely absorbed. This process is characterized by the total absorption of the x-ray photon and the ejection of an electron from the atom.

Based on the attenuation rule, which states that the intensity of x-rays decreases exponentially as they pass through an absorber, it can be concluded that the number of x-rays emerging from any thickness of absorber will never reach 0. This is because even though the intensity decreases, there will always be some x-rays that manage to pass through the absorber. Therefore, the statement "True" is correct.

Attenuation refers to the total reduction in the number of x-rays remaining in an x-ray beam after passing through a certain thickness of tissue. As x-rays pass through the body, they are absorbed by the tissues they encounter, resulting in a decrease in the intensity of the beam. Attenuation is influenced by factors such as tissue density, atomic number, and thickness. Therefore, attenuation is the correct term to describe the reduction in the number of x-rays after penetration through a given thickness of tissue.

Coherent scattering refers to the process in which an X-ray undergoes a change in direction without any change in its energy. This occurs when the X-ray interacts with an atom or molecule and is scattered in a way that the wavefronts of the scattered X-ray remain in phase with each other. Unlike other processes like photodisintegration or the Compton effect, coherent scattering does not involve a transfer of energy to the scattering particle. Therefore, the correct answer for this question is coherent scattering.

X-rays with 5 keV of energy are most likely to undergo coherent scattering. Coherent scattering occurs when X-rays interact with the electrons in an atom and are scattered without losing energy. This type of scattering is more likely to occur at lower energy levels, such as 5 keV, where the X-rays are not energetic enough to cause ionization or excitation of the electrons. In coherent scattering, the X-rays maintain their wavelength and phase, resulting in a scattered pattern that is similar to the original X-ray beam.

When an electron drops from an outer-shell to an inner-shell, the type of radiation emitted is characteristic. This refers to the emission of X-rays that are specific to the element involved in the electron transition. Each element has a unique set of energy levels, and when an electron moves from a higher energy level to a lower one, it releases energy in the form of X-rays that are characteristic to that element.

The photoelectric effect is the correct answer because it explains the phenomenon where X-ray photons are absorbed by the atoms in the material being imaged, resulting in low optical density or dark areas on the radiograph. This effect is particularly prominent in areas corresponding to bone, as bone has a higher atomic number and therefore a higher probability of absorbing X-ray photons through the photoelectric effect.

After a Compton interaction, the Compton secondary electron drops into a vacancy in an electron shell previously created by some other ionizing event.

The Compton effect refers to the scattering of x-rays by electrons. In this process, a photon interacts with an electron, causing it to recoil and the photon to lose some of its energy. The scattered x-ray is the result of this interaction, with the majority of the incident photon energy being retained by the scattered x-ray. Therefore, the correct answer is "scattered x-ray".

In order for a photoelectric interaction to occur, the incident x-ray must have enough energy to dislodge an electron from its bound state in the target atom. This energy is known as the electron binding energy. If the incident x-ray has less energy than the electron binding energy, it will not be able to overcome the binding forces and dislodge an electron. Therefore, the correct answer is "electron binding energy".

The given answer, "dependence on mass density of matter," best defines the quantity of matter per unit volume. Mass density is a measure of how much mass is contained within a given volume of a substance. It is usually expressed in units of kilograms per cubic meter (kg/m^3). The concept of mass density is important in various fields such as physics, chemistry, and engineering, as it helps in understanding the behavior and properties of different substances.

During Compton scattering, the interaction between a photon and an electron is more likely to occur when the photon has low energy. This is because the probability of scattering increases as the energy of the photon decreases. When a low-energy photon interacts with an electron, it transfers some of its energy to the electron, causing it to scatter. Therefore, low-energy photons are more likely to undergo Compton scattering compared to high-energy photons.

Only 5% of the x-ray incident on a patient actually reach the image receptor. This means that a large portion of the x-ray is absorbed or scattered within the patient's body and does not contribute to the formation of the image. Therefore, the statement is false as it implies that a higher percentage of the x-ray reaches the image receptor.

In a Compton interaction, at a deflection of zero (0) degrees from the incident photon, no energy is transferred. This is because at zero degrees, the incident photon and the scattered photon have the same energy and direction. Therefore, there is no loss or transfer of energy between the two photons.

Differential absorption refers to the difference in absorption of X-rays by different tissues or materials in the body. Increasing the kilovolt peak (kVp) in X-ray imaging increases the energy of the X-rays, which leads to greater penetration and decreased absorption by tissues. This results in increased differential absorption and improved contrast in the image. Therefore, increasing the kVp increases the differential absorption.

Barium and iodinated compounds are used as an aid for imaging internal organs primarily because of their high atomic number and high densities compared with soft tissue. This means that they are able to absorb X-rays more effectively, resulting in clearer and more detailed images of the internal organs.

Coherent scattering produces a uniform density of the radiograph called image noise. Coherent scattering occurs when the X-ray photons interact with the atoms of the patient's body and change direction without losing energy. This scattered radiation can contribute to the overall density of the radiograph, resulting in image noise. Unlike other options like image fog, filter, and photidisintegration, coherent scattering specifically refers to the scattering of X-ray photons without any energy loss, making it the correct answer in this context.

Backscatter refers to the phenomenon where scattered radiation from the patient or surrounding objects interacts with the cassette-hinge, causing a foggy appearance on the radiographic image. This occurs when the scattered x-rays bounce back towards the cassette, creating unwanted noise and reducing image quality. Therefore, backscatter is responsible for the cassette-hinge sometimes seen on a radiographic image.

The correct answer is "independent". The probability of a Compton interaction is not affected by the atomic number of the atom involved. This means that the likelihood of a Compton interaction occurring is the same regardless of the atomic number of the atom.

In the photoelectric effect, when an electron transitions from a higher energy level to a lower energy level, it creates a vacancy in the last shell. This vacancy can be filled by an electron from either the L-shell, inner shell, or outer shell. The correct answer is the outer shell because it is the farthest from the nucleus and has the highest energy level among the options given.

Low-energy x-rays (Thompson) tend to interact with the target atom. This is because low-energy x-rays have less energy and are less penetrating, so they are more likely to interact with the atoms in the target material. These interactions can lead to various processes such as photoelectric effect, Compton scattering, or coherent scattering, depending on the energy and properties of the x-rays and the target atoms.

The formula Ei : E, + (Eu + Ers) represents the Compton effect. The Compton effect is a phenomenon in which a photon scatters off an electron, resulting in a change in the photon's wavelength and energy. The formula represents the conservation of energy in this process, where Ei is the initial energy of the photon, E is the final energy of the photon, Eu is the energy transferred to the electron, and Ers is the energy transferred to the scattered photon.

The probability that an x-ray will undergo a photoelectric interaction is approximately 7 times greater in bone than in soft tissue. This means that when an x-ray interacts with bone, it is 7 times more likely to undergo a photoelectric interaction compared to when it interacts with soft tissue. The photoelectric effect is a process in which an x-ray photon interacts with an inner shell electron in an atom, causing the electron to be ejected and creating an ionization event. Bone has a higher density and higher atomic number compared to soft tissue, which increases the likelihood of photoelectric interactions occurring.

The correct answer is "patient, fluroscopy". Fluroscopy is a medical imaging technique that uses a continuous x-ray beam to create real-time images of the patient's internal structures. During a fluroscopy exam, the patient is exposed to radiation as the x-ray beam passes through their body to create the images. This makes the patient the source of most of the occupational exposure to radiation in this scenario.

Interactions occur with energies greater than approximately 10 MeV, which refers to the process of photodisintegration. Photodisintegration is a nuclear reaction in which a high-energy photon interacts with a nucleus, breaking it apart into smaller fragments. This process is responsible for the destruction of heavy nuclei and the production of lighter elements in stellar environments. Disintegration, on the other hand, is a more general term that can refer to any process of breaking apart or decay, but it does not specifically indicate the involvement of high-energy photons.

The probability of photoelectric interaction is inversely proportional to the third power of the atomic number of the absorbing material. This means that as the atomic number of the material increases, the probability of photoelectric interaction decreases. The relationship is not linear, but rather follows a cubic relationship.

Compton interaction is characterized by no energy transfer, therefore no ionization. In this process, an incident photon interacts with an outer shell electron, causing the photon to scatter and lose some of its energy. However, unlike in pair production or ionization processes, the electron is not ejected from the atom and no ionization occurs. This makes compton interaction distinct from the other options listed, which involve energy transfer and ionization to varying degrees.

The correct answer is "compton and photoelectric effect". In diagnostic radiology, these two types of interactions are of primary importance due to the levels of energy involved. The Compton effect occurs when an X-ray photon interacts with an outer shell electron, resulting in the scattering of the photon and the ejection of the electron. The photoelectric effect, on the other hand, involves the absorption of an X-ray photon by an inner shell electron, leading to the ejection of the electron and the production of a characteristic X-ray. Both of these interactions play a crucial role in the diagnostic process.

The formula Er.: Ki- Ku may be used to calculate the energy of the electron emitted during a photoelectron interaction.

The given answer is incorrect. The correct answer should include the photoelectric effect as one of the five basic x-ray interactions with matter. The photoelectric effect occurs when an x-ray photon interacts with an inner shell electron and is completely absorbed, causing the ejection of the electron from the atom.