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Physics
Bushong Ch 10
| Question | Answer |
|---|---|
| x-rays interact with matter in the following five ways. | 1) by coherent scattering, 2) through the Compton effect, 3) through the photoelectric effect, 4) by pair production, and 5) by photodisintegration. |
| What effects are important in making an x-ray image? | Compton effect and photoelectric effect. |
| Eletromagnetic radiation interacts with structures that are similar in size to? | The wavelength of the radiation |
| True or False: X-rays have very short wavelengths. | True |
| The higher the energy of an x-ray, the (shorter or longer) is it's wavelength. | shorter |
| moderate energy x-rays generally interact with what part of the atom and high energy x-rays generally interact with what part of the atom? | electrons; nuclei. |
| Coherent scattering is sometimes called what? Coherent scattering is an interaction between what? | Classical scattering or Thompsons scattering. Low energy x-rays (below 10 keV) and atoms |
| In Coherent Scattering the incident x-ray interacts with a target atom causing it to become? | excited. Low energy x-rays cannot ionize an atom. |
| (Coherent Scattering) The excited atom immediately releases this excess energy as a scattered x-ray with a wavelength equal to the incident x-ray. True or Fase | True. Because the atom is just excited instead of ionized the incident x-ray and the scattered x-ray have the same wavelength and energy. |
| (Coherent Scattering) The incident x-ray and the scattered x-ray have the equal wavelength and equal energy but the scattered x-ray moves in what direction? | A slightly different direction. |
| The result of coherent scattering is a change in direction of the x-ray without a change in its? | energy |
| (Coherent Scattering) There is no energy transfer, and therefore no? | ionization. |
| Most coherent scattered x-rays are scattered in what direction? | The forward direction. |
| Coherent scattering is of little importance to? | Diagnostic radiology |
| (Compton Effect) The interaction of an incident x-ray with an outer-shell electron that scatters the x-ray and also reduces its energy and ionizes the atom is called? | The compton effect or compton scattering. |
| (Compton Effect) The x-ray interacts with an outer shell electron and ejects it from the atom. This is called | ionization |
| (Compton Effect) The ejected electron is called? | A Compton electron or a secondary electron. |
| (Compton Effect) The x-ray continues in a what direction with how much energy? | different; less |
| (Compton Effect) True or False. The energy of the Compton scattered x-ray is equal to the difference between the energy of the incident x-ray and the energy of the ejected electron. | True |
| (Compton Effect) The energy of the ejected electron is equal to? | Its binding energy plus the kinetic energy with which it leaves the atom. |
| The mathematical formula for the Compton Effect is? | Ei=Es (Eb+Eke) Ei is the energy of the incident x-ray Es is the energy of the scattered x-ray Eb is the electron binding energy Eke is the kinetic energy of the electron. |
| During a Compton interaction, most of the energy is divided between? | Scattered x-ray and the Compton electron. |
| Compton scattered x-rays can be deflected in any direction, including 180 degrees from the incident x-ray. True of False | True |
| (Compton Effect) At a defelction of 0 degrees, how much energy is transferred? | none |
| (Compton Effect) As the angle of defelction increases to 180 degrees, more energy is transferred to? | The compton electron |
| (Compton Effect) Even at 180 degrees of deflection, the scattered x-ray retains at least approximately how much of it's original energy? | Two-thirds |
| (Compton Effect) x-rays scattered back in the direction of the incident x-ray beam is called? | Backscatter radiation |
| (Compton Effect) The probability of the Compton effect decreases as x-ray energy? | Increases |
| The probability of the Compton effect is inversely proportional to x-ray energy (1/E) and independent of? | atomic number |
| Compton scattering reduces? | image contrast |
| Compton scattering in tissue can occur with all x-rays and therefore is of considerable importance in? | x-ray imaging |
| Scattered x-rays provide what kind of information on the radiograph? | No useful information |
| The photoelectric effect occurs when an incident x-ray is totally absorbed during the ionization of an inner shell electron. True or False? | True |
| (Photoelectric Effect) The electon removed from the atom is called? | a photoelectron |
| What happens to the incident x-ray during the photoelctric effect? | The x-ray is totally absorbed. |
| (Photoelectric Effect) Photoelectric interaction produces what type of x-ray? | a characteristic x-ray. |
| (Photoelectric Effect) Ejection of a K-shell photoelectron by the incident x-ray results in? | A vacancy in the K shell |
| A photoelectric interaction CANNOT occur unless the incident x-ray has energy how much energy? | equal to or greater than the eletron binding energy. |
| True or false. The probability of photoelectric effects is inversely proportional to the third power of the atomic number of the absorbing material. | False. It is directly proportionalx-ray to the third power of the x-ray energy and inversely proportional to the third power of the absorbing material. |
| True or False: The probability of the photoelectric effect is inversely proportional to the third power of the x-ray energy. | True |
| True of False: Pair production occurs during x-ray imaging. | False. It does NOT occur during x-ray imaging. |
| If an incident x-ray has sufficient energy, it may escape interaction with electrons and come close enough to the nucleus of the atom to be influenced by the? | Strong nuclear force field. |
| The interaction between the x-ray and the nuclear field causes the x-ray to???? and in it's place, ???? electrons appear, one ??? charged (positron) and one ????? charged. This is called | disappear; two; positively; negatively; pair production |
| Pair production occurs with x-rays that have energies greater than? | 1.02 MeV. |
| (Pair Production) The x-ray interacts with? | the nuclear force field |
| (Pair Production) How many electrons that have opposite electrostatic charges are created. | Two |
| (Pair Production) The energy equivalence of the mass of an electron has been calculated to be | 0.51 MeV |
| Because two electrons are formed in pair production interaction with 0.51 MeV, the incident photon must have at least how much energy? | 1.02 MeV |
| (Photodisintegration) X-rays with energy above approximately 10 MeV can escape interaction with electrons and the nuclear force field and will be absorbed by what? | The nucleus. |
| (Photodisintegration) When the high energy x-ray is completely absorbed by the nucleus, the nucleus is raised to an excited state and instantly emits a nucleon or other nuclear fragment. This process is called what? | Photodisintigration |
| True or False: Photodisintegration does NOT occur in diagnostic radiology. | True |
| Photodisintegration is an interaction between what type of x-ray energy (high, moderate or low) and what part of the atom? | high energy; nucleus |
| (Photodisintegration) The x-ray is absorbed by the nucleus, and the nuclear fragment is emitted. True or False? | True |
| (Differential Absorption) More important than the interaction of the x-ray by Compton or photoelectric effect is the x-ray transmitted through the body without interacting. | True |
| (Differential absorption) occurs because of Compton scattering, photoelectric effect and x-rays transmitted through the patient. | True |
| (Differential Absorption) Of the five ways an x-ray can interact with tissue, how many are important to radiology? | Two, Compton effect and photoelectric effect. |
| (Differential Absorption) Compton scatter results in image noise. True of False? | True |
| (Differential absorption) increases as kVp is increased or reduced? | reduced. |
| (Differential Absorption)Approximately what percent of the x-rays incident on a patient reach the image receptor? | 1% |
| (Differential Absorption) An x-ray image results from the difference between x-rays absorbed photoelectrically in the patient & those transmitted to the image receptor. This difference in x-ray interaction is called? | Differential absorption |
| (Differential Absorption) The relative probability of interaction between bone and soft tissue (differential absorption) remains constant, whereas the absolute probability of each decreases with increasing energy. True or False | True |
| (Differential Absorption) X-rays that undergo photoelectric interaction are absorbed and produce what areas of the radiograph? | the absorbed x-rays produce the white images on the radiograph, such as bones. |
| (differential Absorption) At low energies, most x-ray interactions with tissue are photoelectric. At high energies, Compton scattering predominates. True of False. | True |
| (Differential Absorbtion) The interaction of x-rays with tissue has what type of relationship to the mass density of the tissue regardless of the type of interaction? | proportional. When mass density is doubled, the chance for x-ray interaction is doubled because twice as many electrons are available for interaction. |
| (Contrast Examinations)What compounds are needed as an aid for imaging internal organs with x-rays? When used in this fashion they are called? | Barium and iodine compounds. Contrast agents. |
| Air is still used for contrast in some examinations of the colon along with barium; this is called? (Contrast Examinations) When used in this fashion, air is what type of contrast agent? | A double-contrast examination. negative |
| (Exponential Attenuation) When x-rays are incident on any type of tissue, they can interact with the atoms of that tissue through any of these five mechanisms. | Coherent scattering, Compton effect, photoelectric effect, pair production, and photodisintegration. |
| (Exponential Attenuation) The relative frequency of interaction through each of the five interactions with matter depends on what? | The atomic number of the tissue atoms, the mass density, and the x-ray energy. |
| (Exponential Attenuation) An interaction such as the photoelectric effect is called an absorption process because the x-ray disappears. ABSORPTION is an all-or-none condition for x-ray interaction. | True |
| (Exponential Attenuation) The total reduction in the number of x-rays remaining in an x-ray beam after penetration through a given thickness of tissue is called? | Attenuation |
| (Exponential Attenuation) Attenuation is the product of? | absorption and scattering |
| (Exponential Attenuation) X-rays are attenuated exponentially which means what? | They do not have a fixed range in tissue. |
| (Exponential Attenuation) Attenuated x-rays are reduced in number by a given percentage for each incremental thickness of tissue they go through. | True. |
Created by:
Baker RAD 2012
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