Term
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Definition
Penetrating wounds
FB tracts
Determining communication w/ near by structures
Use- dilute non ionic iodine |
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Term
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Definition
Id lesion in spinal cord
Use- non ionic iodine |
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Term
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Definition
Id subcondral bone irregularity, evaluate margins of soft tissue, define synovial soft tissue swelling
Use- dilute non ionic iodine |
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Term
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Definition
Obstruction, renal size, trauma
Use- ionic or non ionic iodine
NO BARIUM |
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Term
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Definition
Swallowing disorders, obstruction, mucosal dx, displacement by mass
Use- barium susp., non ionic iodine (safer than ionic) |
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Term
| Exams using contrast media |
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Definition
| Esopgram, gastrogram, upper GI, excretory urogram, cysogram, urethrogram, arthrogram, myelogram, fistulogram |
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Term
| Use of barium/ organic iodine mix |
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Definition
To accelerate a GI study
Disadvantages: suspect GI perf., potential for dehydration and nausea, unable to evaluate GI transit time. |
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Term
| Characteristics of organic (non ionic) iodine |
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Definition
No dissociation of ions
Very safe if aspirated
Less hypertonic/ hyperosmolar
Use for: meylogram, arthrogram, fistulogram, |
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Term
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Definition
Particles dissociate into ions
Hypertonic/ hyperosmolar
Uses: suspect GI perf., gastrogram, upper GI, excretory urogram, cystogram, urethogram.
Can cause pulmonary edema if aspirated, will pull fluid. |
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Term
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Definition
| Adv: safer if aspirated, inexpensive, excellent mucosal detail, good contrast, |
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Term
Barium susp.
Disadvantages |
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Definition
| Poor coating, cause fibrosis or granuloma if perf., bronchoesophageal fistula can lead to direct aspiration. |
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Term
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Definition
Good coating, used for espogram (with food)
Due to high viscosity can have serious problems if aspirated |
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Term
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Definition
High Z number
Increase opacity (white)
Ex: barium |
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Term
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Definition
Low Z number
Decreased opacity (black)
Ex: air, CO2 |
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Term
| Advantages of digital radiography |
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Definition
| Greater latitude, eliminate dark room and film, electronic distribution (consult, dx, electronic med record), computer optimization, cost savings (elimination of film, chems, dark room ect. |
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Term
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Definition
| Rectangular table of uniformly sized squares (pixels). The matrix is the image. |
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Term
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Definition
The smallest unit in an image with a specific coordinates corresponding to a location in the patient.
High resolution= lots of pixels |
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Term
Spatial resolution
Higher in what type of radiography? |
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Definition
How closely lines can be resolved in an image. High spatial resolution allows small object differentiation.
Higher in film radiography |
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Term
| Disadvantages in digital radiography |
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Definition
| Requires computer skills, computer tech support, systems are more expensive. Image detail (spatial resolution) less than high quality film |
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Term
| What affects the resolution of digital radiography |
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Definition
Acquisition device
Number of pixels
Pixel size
Spatial resolution |
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Term
| What affects contrast of a digital image |
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Definition
Brightness and quality of commuter monitor
Number of colors per pixel (bits)
More bits= more shades of gray
Gray scale images
Quality of video card |
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Term
| How does computed radiography (CR) work? |
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Definition
Digital image is produced from scanning a reusable radiation sensitive imaging plate. Cassette contains photostimulatory phosphor (barium florohalide and europium crystals) that trap electrons and store the image.
A laser then excites them causing them to release stored energy in the form of a photon proportional to the captured image. Photomultiplier then detect these images and convert to a electrical signal that is displayed on the computer screen. |
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Term
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Definition
| Digital radiography, instead of using photostumulable phosphore detectors, has detectors in the cassette that detect x-rays directly and transmit that signal digitally. This is a direct method that uses photoconductors vs. an indirect method that requires scintillators. The flat panel detector itself sits where the cassette would normally be and is comprised of a large number of individual detector elements, each capable of storing a charge. Each region also has a light sensitive region and a region for electronics |
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Term
| Explain how direct DR differs from indirect DR |
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Definition
| Direct type: uses x-ray sensitive transistor chip. Indirect type: uses X-ray intensifying screen/scintillator coupled to large area light detector |
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Term
Purpose of filtration
Most common filtering substance |
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Definition
Purpose: preferentially absorbs lower energy photons which would be absorbed by the patient and increase radiation exposure but not enhance the image.
Aluminum is most common filtering substance. Filters are placed between the x-ray generating device and the patient. |
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Term
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Definition
| Scatter that reduces film quality and results in increased film density with decreased contrast b/w tissues. |
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Term
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Definition
Increase in kVp
Increase in field size
Increase in patient thickness (more secondary reactions because there is more matter to interact with). |
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Term
| Explain cullimation and how it reduces scatter |
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Definition
It restricts the beam of x-rays thus reducing the amount of matter that the x-ray can interact with and produce secondary scatter reactions. This is normally accomplished using any number of different techniques including diaphrams, cones (dental x-rays), and beam limiting device (most common).
The device used to collimate is between the filter and the patient. |
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Term
| What is the grid and how does it work? |
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Definition
| A grid is a carefully fabricated series of radiopaque material (stops x-rays), like lead, alternated with strips of radiolucent (lets x-rays pass) material. This then only allows those x-rays on a straight line from the source to the image receptor. When a grid is placed between the patient and the film, it removes scatter production by the interactions of the primary beam with the patient. |
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Term
|
Definition
Stationary vs moving
Focused and parallel |
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Term
| Grid ratios and what they do? |
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Definition
| Grid ratio is the relation of the height of the lead strips to the distance between them. i.e. if the ratio is 5:1 then the foil is 5 times higher than the space between them. The higher the ratio, the more effective the grid is at absorbing scatter, but more difficult it is for the primary x-ray beam to pass through it. Therefore there is more exposure to patients with high grid ratios. |
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Term
| When to use a grid? Adjustment of settings. |
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Definition
Use a grid any time the tissue thickness is greater than 9cm.
Add 10-12 kVp when using a grid. |
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Term
| Advantages of using a grid |
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Definition
| It improves the film quality by reducing the scatter that reaches the film |
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Term
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Definition
One is the Increases in exposure to compensate for removal of part of the photons in the beam.
The other is grid cutoff. |
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Term
| What is grid cutoff and how is it caused? |
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Definition
It is the loss of primary beam (not scatter) that occurs when the lead strips are not parallel to the primary beam. This can be caused by:
Improper focus to film distance (off-focus)
Tilted grid
Off-centered focused grid
Upside-down focused grid
Note that all parallel grids will have some cutoff |
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Term
| Because of the overall shape and nature of what a grid is, what must the person taking the x-ray take into consideration? |
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Definition
That there needs to be a precise distances between the different machine parts (FFD).
Grids require accurate centering and leveling.
Grids require more exposure. |
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Term
|
Definition
Developing:
This converts the Ag to Ag (reduction of silver halide crystals into metallic silver). Metallic silver is black and are associated with the black areas on the radiograph. These black areas are the ones in which the photons passed through the patient and reached the image recoding system.
Fixing:
Removes the unexposed silver halide crystals. This process produces the clear areas of the radiograph which are the areas where no photons reached the image receptor.
Washing or Rinsing:
This occurs after both development and fixing has occurred. This process removes any excess chemicals from the film which can eventually damage the storage and quality of the film.
**Note that the dip tank or hand processing methods use the same steps to develop the image. |
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Term
What are the time and temp restrictions in hand processing?
Important points to remember |
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Definition
Affix films to hanger
Developer - 68° F for 5 minutes
Rinse bath – 30 seconds
Fixer – 60-80° F for 2-4 times the length of development
Wash – 60-85° F for 5-30 minutes
Careful hanging and positioning of films
Stir chemicals
Use fresh chemicals
Monitor temperature (this determines time of processing) |
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Term
| Differences b/w automatic and manual film processing |
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Definition
Processing times – 90 seconds most common
Temperature 77-96° F
Tabletop (within darkroom) or extend through wall of darkroom
Chemicals
Differ in composition from manual processing chemicals
“Rapid X-Ray Developer”
Automatically replenished |
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Term
| Dark room procedures that lead to high quality rads |
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Definition
Handle film and intensifying screens carefully in the dry area
Mix solutions carefully according to directions
Stir solutions daily
Use an accurate thermometer
Agitate films in solutions
Avoid splashing solutions
Keep hands and work areas dry |
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Term
| What factors affect the final image quality of rads? |
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Definition
Technical factors-kVp, mA, time
Patient factors-composition of body and thickness of part=>differential absorption
Film/screen factors
Film Processing |
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Term
| Common causes of artifacts |
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Definition
Static electricity (appears as black tree branches/star burst)
Pressure marks (black crescent shaped marks)
Dirty Screens (white mark in the shape of the debris) |
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Term
| What is fog and what does it cause? |
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Definition
Fog is the unwanted exposure of part or all of the radiograph. It results in poor contrast.
Causes:
Radiation over-exposure
Light leak
Exposure to light during loading/unloading
Safelight in the dark room is defective/the wrong type
Chemical discrepancies
Scatter radiation
Aging of film |
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Term
| What is a technique chart |
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Definition
| A table with predetermined x-ray machine settings that will allow a diagnostic quality image ~80% of the time. These can be variable or fixed kVp charts and are sometimes used for digital imaging as well. |
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Term
| What factors do not affect technique chart? |
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Definition
| Cassette size and focal spot |
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Term
| Sante's rule to determine kVp for a variable kVp TC |
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Definition
| A table with predetermined x-ray machine settings that will allow a diagnostic quality image ~80% of the time. These can be variable or fixed kVp charts and are sometimes used for digital imaging as well. |
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Term
| For fixed mAs TC, what is desired for fewer shades of gray? |
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Definition
| Low kVp. Good for bone. High Contrast |
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Term
| Explain the basis of a fixed kVp TC |
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Definition
kVp is selected as the optimum required for penetration of the anatomic part
mAs is changed according to the thickness
Often see small, medium, large => with 30% change in mAs between
Longer scale of contrast—more shades of gray
Less dose to patient |
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Term
| When creating a TC, what factors must be considered? |
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Definition
Speed of x-ray film
Speed of intensifying screens
Focal-film distance
Amount of inherent and added filtration
Type and quality of developer solution
Time and temp of developer
Use of grid
Type of grid
Character of incoming line voltage (i.e. same room, same x-ray machine) |
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Term
| What is the 10% rule for kVp and mAs? |
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Definition
Reduce (or increase) the kVp by 10% and double (or half) the mAs will result in essentially the same diagnostic quality radiograph
Example: Note that kVp and mAs are inversely related
77 kVp @ 10 mAs
70 kVp @ 20 mAs
84 kVp @ 5 mAs |
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Term
| How do you determine the mAs if you have a tissue greater than 10 cm |
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Definition
| Take the mAs times the bucky factor and use the above rules to change the kVp. |
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Term
| Technique for bone and extremities |
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Definition
| High contrast/short scale. This is done using high mAs and low kVp. When given a set of useful techniques that are good for extremities, use the 10% rule to adjust the settings. |
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Term
| Technique for soft tissue |
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Definition
| A long scale of contrast using high kVp and low mAs. |
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Term
| What are the different factors of involving radiographic quality |
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Definition
Radiographic density (opacity and exposure)
Radiographic contrast (patient)
Radiographic detail (geometric factors)
The presence of artifacts
Technical factors-kVp, mA, time
Patient factors-composition of body and thickness of part=>differential absorption
Patient motion
Patient positioning
Distortion
Film/screen factors
Film Processing |
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Term
| Rules of thumb used when encountering different anomalies? |
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Definition
Decrease kVp by 5-10% when
Destructive bone dz
Pneumothorax
Cachexia
Increase kVp by 5-10%
Pleural or peritoneal effusion
Soft tissue masses
Positive contrast studies |
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Term
|
Definition
Measurement error
Incorrect film/screen combination
Stale chemicals
Aging screens
Pathology |
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Term
| General rules for influencing exposure |
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Definition
mA
↑ mA =>↑ film blackness
Exposure time
↑ time => ↑ film blackness
Focal film distance (FFD)
↑FFD => ↓ film blackness (inverse to square of distance)
kVp
Low kVp will produce films with high contrast (black and white)
High kVp will produce films with low contrast (shades of gray) |
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