RTE 1401 CORE REVIEWS ANSWERS AND QUESTIONS
SET A+
✔✔Off-level grid error - ✔✔grid cutoff due to grid being off level with the central ray
-occurs with parallel and focus grids
✔✔How will an OFF-LEVEL grid error appear on a manifest image? - ✔✔decrease in
radiation exposure or too light
✔✔off-focus grid error - ✔✔when the grid is used outside of the SID or focal range
-occurs with focus grids
✔✔How will an OFF-FOCUS grid error appear on a manifest image? -
✔✔underexposed or too light along the edges of the image
✔✔off-center grid error - ✔✔grid is not centered to the central ray (perpendicular)
-occurs with focus grids
✔✔How will an OFF-CENTER grid error appear on a manifest image? - ✔✔decrease in
exposure across entire image
-occurs with focus grids
✔✔upside-down grid error - ✔✔when a focus grid is used upside-down
✔✔How will an UPSIDE-DOWN grid error appear on a manifest image? - ✔✔exposure
will be black and white in the center and underexposed on the lateral borders
✔✔Moire Effect - ✔✔artifact that can happen when the stationary grid is used during
computer radiography imaging (CR)
✔✔How will the Morie Effect appear on a manifest image? - ✔✔zebra or striped pattern
✔✔convergence - ✔✔distance recommended for grid use
, ✔✔grid radius - ✔✔distance from grid to convergence point= the focal range
✔✔When should a grid be used? - ✔✔When...
1. part thickness is 10 cm (4 inches)
2. kVp is 60 or more
✔✔Calipers - ✔✔device that measures part thickness
✔✔air-gap - ✔✔intentionally increasing OID in order to reduce scatter that reaches the
film.
6 inch OID approximately = to 8:1 grid
✔✔What method will give you the best detail: grid or air-gap? - ✔✔grid because a grid
helps to absorb some transmitted photons and air-gap does not
✔✔How does one compensate for the magnification loss due to increased OID? -
✔✔increase SID by 7" for every 1" of OID
✔✔parts of x-ray film - ✔✔super coat, emulsion layer, adhesive layer, base
(double layer has twice as many super coats, emulsion and adhesive layers)
✔✔What is the base made of? - ✔✔polyester-plastic that's radiolucent flexible, and
durable
✔✔Adhesive - ✔✔glues emulsion layer to base
✔✔Emulsion layer - ✔✔stores latent image, made of silver- halides (bromides, iodides)
that convert to black-metallic through processing
✔✔sensitivity specks - ✔✔specks of gold-silver sulfides which help to store the latent
image
✔✔super coat on film - ✔✔makes it difficult to burn and impossible to tear
✔✔Indirect digital radiography - ✔✔cassette-less 2-step process that converts x-rays to
light then to an electrical signal using scintillaters (CsI, GaO) and amorphous silicon (A-
si)
✔✔Direct digital radiography - ✔✔cassete-less process that conversts x-rays to an
electrical signal with amorphous selenium (A-se)
✔✔change coupled device (CCD) - ✔✔light sensitive device arranged in small squares
similar to pixels that collects, measures, and converts the light to electrical signals
SET A+
✔✔Off-level grid error - ✔✔grid cutoff due to grid being off level with the central ray
-occurs with parallel and focus grids
✔✔How will an OFF-LEVEL grid error appear on a manifest image? - ✔✔decrease in
radiation exposure or too light
✔✔off-focus grid error - ✔✔when the grid is used outside of the SID or focal range
-occurs with focus grids
✔✔How will an OFF-FOCUS grid error appear on a manifest image? -
✔✔underexposed or too light along the edges of the image
✔✔off-center grid error - ✔✔grid is not centered to the central ray (perpendicular)
-occurs with focus grids
✔✔How will an OFF-CENTER grid error appear on a manifest image? - ✔✔decrease in
exposure across entire image
-occurs with focus grids
✔✔upside-down grid error - ✔✔when a focus grid is used upside-down
✔✔How will an UPSIDE-DOWN grid error appear on a manifest image? - ✔✔exposure
will be black and white in the center and underexposed on the lateral borders
✔✔Moire Effect - ✔✔artifact that can happen when the stationary grid is used during
computer radiography imaging (CR)
✔✔How will the Morie Effect appear on a manifest image? - ✔✔zebra or striped pattern
✔✔convergence - ✔✔distance recommended for grid use
, ✔✔grid radius - ✔✔distance from grid to convergence point= the focal range
✔✔When should a grid be used? - ✔✔When...
1. part thickness is 10 cm (4 inches)
2. kVp is 60 or more
✔✔Calipers - ✔✔device that measures part thickness
✔✔air-gap - ✔✔intentionally increasing OID in order to reduce scatter that reaches the
film.
6 inch OID approximately = to 8:1 grid
✔✔What method will give you the best detail: grid or air-gap? - ✔✔grid because a grid
helps to absorb some transmitted photons and air-gap does not
✔✔How does one compensate for the magnification loss due to increased OID? -
✔✔increase SID by 7" for every 1" of OID
✔✔parts of x-ray film - ✔✔super coat, emulsion layer, adhesive layer, base
(double layer has twice as many super coats, emulsion and adhesive layers)
✔✔What is the base made of? - ✔✔polyester-plastic that's radiolucent flexible, and
durable
✔✔Adhesive - ✔✔glues emulsion layer to base
✔✔Emulsion layer - ✔✔stores latent image, made of silver- halides (bromides, iodides)
that convert to black-metallic through processing
✔✔sensitivity specks - ✔✔specks of gold-silver sulfides which help to store the latent
image
✔✔super coat on film - ✔✔makes it difficult to burn and impossible to tear
✔✔Indirect digital radiography - ✔✔cassette-less 2-step process that converts x-rays to
light then to an electrical signal using scintillaters (CsI, GaO) and amorphous silicon (A-
si)
✔✔Direct digital radiography - ✔✔cassete-less process that conversts x-rays to an
electrical signal with amorphous selenium (A-se)
✔✔change coupled device (CCD) - ✔✔light sensitive device arranged in small squares
similar to pixels that collects, measures, and converts the light to electrical signals
