Chapter 9 Flashcards
interact with the whole atom.
Low energy X-rays
interact with electrons
Moderate energy X-rays
interact with nuclei.
High energy X-rays
the incident x-ray interacts with a target atom, causing it to become excited.
Coherent scattering
Other name for coherent scattering
Classical Scattering or
Thompson Scattering.
general graying of an image; reduces image contrast.
IMAGE NOISE
• occurs between moderate-energy x-rays and outer-shell electrons.
• interaction with outer-shell electrons that not only scatters the x-ray but reduces its energy and ionizes the atom as well.
COMPTON SCATTERING
the ejected electron from the atom.
COMPTON/SECONDARY ELECTRON
X-ray scattered back in the direction of the incident x-ray beam.
BACKSCATTER RADIATION
reduces image contrast.”
Compton scattering
• x-rays undergo ionizing interactions with inner-shell electrons.
• result: the x-ray is not scattered, but it is totally absorbed
• characteristic radiation is produced.
Photo electric effect
• the interaction between the x-ray and the
nuclear field (causes the x-ray to disappear)
• result: two electrons appear, with opposite charge (neutrons)
PAIR PRODUCTION
• very important for positron emission tomography imaging in nuclear medicine.
PAIR PRODUCTION
when a positron unites with a free electron, and the mass of both particles is converted to energy in a process.
ANNAHILATION RADIATION
does not occur during x-ray imaging.”
Pair production
• incident x-rays can escape interaction with electrons and the nuclear field and be absorbed directly by the nucleus.
• the nucleus is raised to an excited state and instantly emits a nucleon or other nuclear fragment.
PHOTO DISINTEGRATION and PAIR PRODUCTION
an x-ray image results from the difference between those x-rays absorbed photoelectrically in the patient and those transmitted to the image receptor.
Differential absorption
a generalized dulling of the image by x-rays not representing diagnostic information.
IMAGE NOISE
• results from approximately 0.5% of the x-rays emitted by the x-ray tube.
RADIOGRAPHIC IMAGE
compounds used as an aid for imaging internal organs with x-rays.
CONTRAST AGENT
produces excellent, high-contrast radiographs of the organs of the gastrointestinal tract.
LOW-KVp TECHNIQUE
examinations not only to outline the organ under investigation but also to penetrate the contrast medium so the lumen of the organ can be visualized more clearly.
HIGH-KVp TECHNIQUE
uses air for contrast in some examinations of the colon along with barium.
DOUBLE CONTRAST EXAMINATION
•an interaction wherein the x-ray disappears
ABSORPTION PROCESS
• the removal of an x-ray from a beam through a photoelectric effect.
• all-or-none condition for x-ray interaction.
ABSORPTION
• total reduction in the number of x-rays remaining in an x-ray beam after penetration through a given thickness of tissue.
ATTENUATION
•when a broad beam of x-rays is incident on any tissue, some of the x-rays are absorbed, and some are scattered.
• result: reduced number of x-rays
X-RAY ATTENUATION
