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RADT 311 Unit 3
Question | Answer |
---|---|
The x-ray beam is primarily divided into what 2 parts? | Primary beam and Remnant beam |
What is the primary beam? | Radiation emitted by tube but not yet passed through patient or object |
What is the remnant beam? | Radiation that emerges from body tissues behind the patient or object and it is the IMAGING-FORMING RADIATION |
Primary x-rays diverge isotropically (fan out) except the ___________. | central ray (CR) |
What are the six types of radiographic variables? | Technical, geometrical, patient status, IR systems, image processing, and viewing conditions |
What are the 3 interactions applicable to diagnostic radiography? | Photoelectric effect, Compton interaction, Coherent scattering (Thompson, Rayleigh) |
The photoelectric effect was first explained by: | Albert Einstein |
The Photoelectric effect: The patient's body __________ (completely/partially/momentarily) absorbs the x-ray photon. | completely |
The Photoelectric effect: A photon intersect an orbital electron in the _____________ shell. | innermost |
_____________ is primarily responsible for the production of subject contrast in the radiographic image. | The Photoelectric Effect |
The Photoelectric effect: Leaves a microscopic spot that is unexposed or ____________. | white |
What is another name for Compton Scatter? | Modified / Incoherent Scatter |
Who discovered Compton Scatter? | Arthur Compton |
Compton Scatter: _________ (complete/partial/momentary) absorption of the x-ray photon’s energy occurs and the energy left over is reemitted as a new x-ray photon. | Partial |
Compton Scatter: Occurs in the _______ electron shells of an atom. | outer |
T/F: Compton Effect: The recoil electron cannot reach the IR, but the scattered x-ray photon can reach the IR. | True |
A series of Compton interactions can occur, until, when the remaining energy is slightly above the binding energy of a shell, a __________ interaction may take place | photoelectric |
Scatter x-rays with ________ (higher/lower) energy are deflected less from the direction of the original x-ray. | higher |
T/F: Scatter x-rays with higher energy travel in a more forward direction and are more likely to reach the IR. | True |
Approximately _____ % of all scatter is caused by the Compton interaction. | 97% |
_____ % of all scatter is caused by Coherent Scatter. | 3% |
Coherent Scatter: __________ (complete/partial/momentary) absorption of the x-ray photon’s energy by an orbital electron or by the atom as a whole | Momentary |
Coherent Scatter: The emitted photon has _________ energy to the original | identical |
T/F: Coherent Scattering: The scattered photon may reach the IR and degrade contrast. | True |
Coherent scattering is also called ____________ scattering. | unmodified |
With a Thompson interaction, the photon energy is absorbed and re-emitted by a ______________. | single orbital electron |
With a Raleigh interaction, the photon energy is absorbed and re-emitted by the excited ______________. | atom as a whole |
For every 4 cm (1.5 in) increase in part thickness, increase technique by _________ | a factor of 2 (double the mAs or increase kVp by 15%) |
T/F: Any information missing from the remnant beam cannot be recovered later by computer processing nor by image manipulation at the display monitor. | True |
Photon energy is ______ dependent. | kVp |
__________ is produced by the differential absorption between various tissues of the body. | Subject Contrast |
__________ is defined as mass per volume in the patient. It may be thought of as the concentration of atoms or molecules packed into a given space. | Tissue Density |
The occurrence of all interactions, (both Photoelectric and Compton), is __________ proportional to the physical density of the tissue through which the x-rays pass. | directly (twice as many molecules per cubic cm causes twice as many interactions) |
Three main types of body tissues are distinguished primarily on the basis of their physical density: | Soft tissue, gases, fat |
Two types of body tissues are distinguished primarily on the basis of their atomic number: | Bone and metals, including all contrast agents |
_____________ is an average that takes into account the number and “size” of each type of atom. | Tissue atomic number |
The occurrence of the photoelectric effect is _________ (increased/reduced) as kVp is increased. | reduced |
The occurrence of the Photoelectric effect is ______ (increased/decreased) as kVp is increased. | decreased |
Penetrating x-rays produce the what shade in the image. | darker (black) areas |
Photoelectric interactions produce the what shade in the image. | lighter (white) areas |