Exam 2 Flashcards
as the Bucky factor increases, the rad technique & pt dose ________ proportionately
increases
what is the formula for calculating contrast improvement factor?
k = rad contrast w grid/rad contrast w/o grid
high ratio grid has _______ contrast improvement factor
higher
How do you calculate Bucky Factor?
B = Incident remnant XRs/Transmitted Img-forming XRs = pt dose w grid/pt dose w/o grid
what does contrast improvement factor measure?
improvement in img quality when grids are used
what does Bucky factor measure?
how much of an increase in technique will be required compared w non grid exposure; or how large an + in pt dose will accompany the use of particular grid
the higher the grid ratio, the ______ the Bucky factor
higher
Bucky factor increases with _______ kVp
increasing
purpose of moving grid?
to get rid of grid lines
what are the different types of grid motions used?
reciprocating (back & forth) and oscillating (circular)
how will the img appear if the grid is off-level?
overall - in density
how will the img appear if the grid is off-center?
overall - in density
how will the img appear if the grid is off-focus?
loss of density along the edges
how will the img appear if the grid is upside-down?
loss of density along the edges
List the layers of radiographic film
- supercoat
- emulsion
- adhesive layer
- film base
What is the thickness of the film base
150-300 µm
Film base is made of what material?
polyester (plastic)
The emulsion is made of what materials?
Ag Halide Crystals (w 90-99% of Ag bromide + 1-10% Ag iodide) suspended in gelatin
Which film gives better detail? Why? A) Single emulsion film B) Double emulsion film
Single Emulsion Film; less loss of transmitted light, so better detail
Which film is faster? Why? A) Single emulsion film B) Double emulsion film
Double Emulsion Film; More SHC —> more speed
Which film causes more radiation dose to patients? Why? A) Single emulsion film B) Double emulsion film
Single Emulsion; less speed, more exposure T required
What is a sensitivity center or sensitivity speck?
physical imperfections in the crystal lattice of the emulsion layers from the manufacturing process; serves as an e- trap from the bromide —> they are neg. charged
What is spectral matching?
matching the spectral sensitivity of the film w the spectral emission of the IS to increase speed of IR
What filter is best for blue sensitive film?
amber color filter - transmits wavelengths longer than 550 nanometer (red also suitable)