Term
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Definition
| Imaging modality that useds x-ray film and usually an x-ray tube mounted from a ceiling track that allows tube movement in any direction; provides fixed images. |
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Term
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Definition
| A processed film, recording the aerial image or exit radiation of an anatomic part. |
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Term
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Definition
| Radiologic technologist who deals specifically with x-ray imaging. |
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Term
| DESCRIBE THE CONSTRUCTION AND FUNCTION OF AN X-RAY TUBE |
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Definition
Construction & function of an x-ray tube:
An x-ray tube usually consists of a SOURCE OF ELECTRON, a way to MOVE ELECTRONS FAST, and a way to STOP ELECTRONS FAST; it functions to produce x-ray photons which are transformed into an x-ray beam. |
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Term
| BRIEFLY DESCRIBE THE PRODUCTION OF AN X-RAY BEAM IN AN X-RAY TUBE |
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Definition
| An x-ray beam is formed when electrons are converted via heat into x-ray photons that are manipulated to create an x-ray image. |
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Term
| DEFINE THERMIONIC EMISSION |
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Definition
| The boiling-off of electrons. |
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Term
| DEFINE MILLIAMPERAGE (mA) |
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Definition
| A measurement of x-ray tube current; the # of electrons crossing the tube from cathode to anode per second. |
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Term
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Definition
| Time required to end an exposure |
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Term
| DEFINE MILLIAMPERAGE/SECOND (mAs) |
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Definition
| The product of exposure time and x-ray tube current; measure of the total # of electrons |
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Term
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Definition
| The measurement of electrical potential across an x-ray tube |
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Term
| DEFINE SOURCE-IMAGE-DISTANCE (SID) |
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Definition
| Distance from the target/focal spot to the image receptor |
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Term
| DEFINE SOURCE-OBJECT-DISTANCE (SOD) |
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Definition
| Distance from the target/focal spot to the object being imaged. |
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Term
| DEFINE OBJECT-IMAGE-DISTANCE (OID) |
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Definition
| Distance between the object being imaged and the image receptor |
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Term
DESCRIBE THE INFLUENCE OF kVp ON:
A. THE ELECTRONS MOVING FROM THE CATHODE TO THE ANODE
B. THE BEAM OF X-RAYS EMITTED FROM THE TUBE
C. THE EXPOSURE RATE |
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Definition
A. kVp affects the speed & energy of the electrons moving from
the cathode to the anode (+ kVp = + speed & energy)
B. kVp affects the penetrating ability of the beam
(+ kVP = + penetrating ability of the beam)
C. + kvp = + patient dose (exposure rate) |
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Term
DESCRIBE THE INFLUENCE OF mA ON:
A. THE ELECTRONS MOVING FROM THE CATHODE TO THE ANODE
B. THE BEAM OF X-RAYS EMITTED FROM THE TUBE
C. THE EXPOSURE RATE |
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Definition
A. mA affects the amount of electrons moving from the cathode
to the anode (+ mA = + in # of E)
B. mA influences the beam of x-rays because it determines the
amount of electrons. The # of electrons that strike the
anode determine how many x-rays are made.
C. mA directly controls the exposure rate |
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Term
| DESCRIBE THE EFFECTS OF FREQUENCY, CONTRAST, AND NOISE ON DIGITAL IMAGE QUALITY |
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Definition
Frequency is the number of crests passing a point per second; the higher the frequency, the higher the intensity of the beam (# of photons).
Contrast makes details visible and can be manipulated post-processing of the image.
Noise makes a digital image appear blotchy. |
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Term
| LIST & DESCRIBE THE BASIC PROPERTIES OF X-RAYS |
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Definition
DENSITY - degree of blackening of the film
CONTRAST - difference between adjacent densities (makes details visible)
RECORDED DETAIL - degree of definition/sharpeness
DISTORTION - misrepresentation of size & shape |
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Term
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Definition
| The useful beam that leaves the x-ray tube |
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Term
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Definition
| The thin, straight column of x-rays that is located at the center of the primary beam |
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Term
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Definition
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Term
| DEFINE OFF-FOCUS RADIATION |
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Definition
| X-rays that stray from the focal spot |
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Term
| DEFINE REMNANT (EXIT) RADIATION |
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Definition
| Radiation that exits the patient |
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Term
| DEFINE SECONDARY/SCATTER RADIATION |
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Definition
| The primary photons that change direction after interacting with the patient's tissues. |
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Term
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Definition
| X-rays that escape from the housing of the tube (other than through the window) |
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Term
| DESCRIBE THE RADIOGRAPHIC APPEARANCE OF MOTION AND OF POOR SCREEN-FILM CONTACT. |
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Definition
| Motion usually appears as a blurring of structures on a radiograph; poor screen-film contact will show localized areas of blur on a finished image. |
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Term
| DEFINE NOISE AS IT APPLIES TO RADIOGRAPHIC IMAGES |
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Definition
| Noise is a blotchy appearance on an image |
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Term
| LIST AND DEFINE THE THREE MOST COMMON FORMS OF NOISE/MOTTLE |
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Definition
FILM MOTTLE - when density is not uniform on the image due to the distribution & concentration of silver halide crystals, and the image possesses a blotchy appearance (more common when fast films are used)
SCREEN MOTTLE - the irregular distribution of the phosphor in the screen can lead to irregular brightness in the light emitted and could cause a blotchy appearance on an image
QUANTUM MOTTLE - the blotchy appearance of a radiograph due to the random/irregular distribution of the x-ray photons striking the film to produce the image |
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Term
| DEFINE FOG AND DESCRIBE ITS RADIOGRAPHIC APPEARANCE |
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Definition
FOG - any unwanted density on an image that does not contribute useful information
Density on the film is increased when fog is present. |
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Term
| LIST SOME COMMON SOURCES OF RADIOGRAPHIC FOG AND EXPLAIN THE IMPORTANCE OF CONTROLLING THE PRODUCTION OF THE AMOUNT OF S/S REACHING THE FILM DURING THE RADIOGRAPHIC PRODUCTION |
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Definition
COMMON SOURCES - radiation, light, chemicals, temperature, & emulsion time
S/S radiation must be reduced to provide an image of diagnostic quality and to reduce exposure to patient & technologist. |
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Term
| DEFINE ARTIFACT AS APPLIED TO RADIOGRAPHS AND DESCRIBE COMMON TYPES OF RADIOGRAPHIC ARTIFACTS |
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Definition
An artifact is an area on an image where the transmission of light was blocked between the screen & film, or when the ionizing radiation was prohibited from activating the intensifying screen.
Common types: screen dirt, jewelry, medical equipment (tubes/lines), medical hardware (pins, screws), gown snaps, pathologies, and foreign objects |
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Term
| DESCRIBE AND EXPLAIN THE USE OF PROPER IDENTIFICATION AND MARKING OF RADIOGRAPHS |
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Definition
| Proper identification and marking of radiographs reduces errors by showing which image belongs to which patient, & which side is being imaged (or to define patient's direction); it also assists the radiologist in determining a diagnosis. |
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Term
| EXPLAIN THE IMPORTANCE OF AND DESCRIBE BASIC METHODS OF RADIATION PROTECTION |
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Definition
| Radiation protection is key to reducing unnecessary exposure to patient & technologist. Use of lead gloves, aprons, goggles, and shields are examples of protection. |
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Term
| DESCRIBE THE SYSTEMATIC PROCESS OF RADIOGRAPHIC EVALUATION IN LAB & IN CLINICAL (7 STEPS) |
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Definition
ANATOMY & POSITIONING - pt. positioning, area of interest in profile
DENSITY & CONTRAST - proper technique used, details are visible
RADIATION PROTECTION - patient was shielded, tech collimated
MAG - presence of magnification, blur, artifacts, gridlines
IDENTIFICATION - correct marking and id of pt. on image
ACCEPT OR REJECT IMAGE
REVIEW - for completeness & accuracy for the procedure requested |
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Term
| EXPLAIN WHAT DETERMINES ACCEPTABLE LIMITS |
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Definition
| Image acceptance limits are determined by accuracy on the technologist's part (was the image of good diagnostic quality?) |
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Term
| IDENTIFY THE FIVE STEPS OF THE IMAGING PROCESS |
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Definition
1. image acquistion
2. image processing
3. image archiving
4. image display
5. image analysis |
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Term
| IDENTIFY FACTORS THAT INFLUENCE EACH OF THE FOUR RADIOGRAPHC PROPERTIES & ALSO THE FACTORS THAT INFLUENCE SUBJECT CONTRAST |
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Definition
PROPERTY FACTORS
Density- mAs, fog, grids, screen speed, OID,
filtration, beam restriction, processing,
power supply, patient, & pathology
Contrast- kVp, filtration, power, grids, screen
speed, OID, beam restriction
Resolution- SID, OID, FSS, pt. thickness, screen speed,
film/screen contact, motion
Distortion- SID, OID, pt. thickness, CR alignment, IR
alignment, direction/degree of CR angle
Subject contrast- atomic #, density, condition, kVp used, &
thickness of part |
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Term
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Definition
| Photons of varying energy; containing many different wavelengths and energies. |
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Term
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Definition
| Consisting of photons whose energies range from a minimum to the peak value; nonuniform in energy and wavelength because the amount of braking (Bremsstrahlung) or deceleration varies among electrons according to their speed and how closely they approach the nucleus. |
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Term
| LIST THE FIVE COMMON INTERACTIONS OF X-RAYS LEAVING THE TUBE |
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Definition
Pair Production
Photodisintegration
Coherent Scattering (a.k.a. Thompson, Classical, Unmodified)
PHOTOELECTRIC ABSORPTION
COMPTON SCATTERING |
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Term
| BRIEFLY EXPLAIN THE PAIR PRODUCTION INTERACTION |
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Definition
-High energy photon, enters body (1.02 MeV), loses energy, splits into a POSITRON and NEGATRON, ANNIHILATION REACTION, travel in opposite directions (each is .5 MeV)
-Unimportant in x-ray |
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Term
| EXPLAIN THE ANNIHILATION REACTION |
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Definition
| Matter being converted back into energy as a result of a positron combining with a negative electron, which creates two photons moving in opposite directions. |
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Term
| BRIEFLY EXPLAIN THE PHOTODISINTEGRATION INTERACTION |
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Definition
-High energy photon strikes nucleus, all energy is absorbed, high excitement, emits a NUCLEAR FRAGMENT. (x-ray energy above 10 MeV)
-not in diagnostic range; of no concern |
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Term
| LIST THREE OTHER NAMES FOR COHERENT SCATTERING & BRIEFLY EXPLAIN COHERENT SCATTERING |
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Definition
1. Thompson
2. Classical
3. Unmodified
-Incident x-ray photon (low energy) excites atom, releases secondary photon (SAME ENERGY/WAVELENGTH AS ORIGINAL PHOTON), it just CHANGES DIRECTION
-Contributes to fog
-Some occur throughout diagnostic range |
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Term
| EXPLAIN PHOTOELECTRIC ABSORPTION |
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Definition
-Photon comes into atom, STRIKES INNER SHELL ELECTRON out of orbit, energy is transferred to electron that was KICKED OUT, has less binding energy; CASCADE EFFECT occurs (secondary radiation)
-In x-ray diagnostic range |
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Term
| WHAT IS THE CASCADE EFFECT? |
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Definition
| When an outer shell electron moves into an inner shell vacancy, and as it does, it releases energy in the form of a characteristic photon - known as secondary radiation. |
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Term
| EXPLAIN COMPTON SCATTERING |
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Definition
-X-ray photon interacts with OUTER SHELL ELECTRON, EJECTS ELECTRON, & can ionize matter/loses energy; wants state of rest, looks for vacancy and:
CHANGES DIRECTION or
loses energy or
can be absorbed or
can have another interaction or
could produce fog/backscatter or
could be absorbed by technologist
-Throughout diagnostic range |
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