Properties of a Radiographic Image

Question 1

Density:

Answer 1

the overall degree of blackness on the film

high density (overexposed) = too dark

Question 2

primary controlling factors of Density:

Answer 2

1.) Milliamperage (mA)
2.) Exposure time (sec)

mA x sec = mAs = total exposure.

Question 3

On final: will ask an “inverse square law” problem:

Answer 3

As long as mAs is equal, film density will also be equal

Question 4

exposure latitude:

Answer 4

how much dose u can give and still get an acceptable image

Question 5

great test questions:

what factors influence density?

Answer 5

kilovoltage
object size
developing time
developing temp
fixing time
TFD (inverse square law)

Question 6

If I increase my kilovoltage, how will this affect density?

Answer 6

increase it

Question 7

factors that increase density:

Answer 7

more Kilovoltage
longer Developing time
higher Developing Temp

Question 8

factors that decrease density:

Answer 8

object size (the thicker, the less)
longer fixing time
longer tube-film distance (decreases exponentially, inverse square law)

Question 9

Contrast:

Answer 9

ability to tell difference between 2 shades of colors.

Difference in densities between adjacent areas of a radiograph.

Question 10

primary controlling factor for contrast:

Answer 10

kVp

Question 11

when is high contrast ideal in radiographs:

Answer 11

caries, decay

Question 12

how to get low contrast:

when u wanna do this

Answer 12

higher kVp. more shades of gray. better for perio, subtle changes in bone, etc.

Question 13

kVp:

short-scale contrast vs longer-scale contrast:

Answer 13

short-scale: low kVp (more contrast)
longer-scale: high kVp

Question 14

what causes fog:

Answer 14

compton scatter

Question 15

how to eliminate / lower fog:

Answer 15

column down image, instead of 2.75 inch diameter maybe do 1 inch.

Question 16

how long can ur cone be:

Answer 16

2.75 inch diameter.

Question 17

aluminum filtration:

Answer 17

if I have a voltage under 50 KV to my unit, I need to have .5 mm aluminum. if it’s from 50 to 65, its gonna be a 1.5 mm and if it’s over 65 or 70, then it’s going to be 2.5 mm

Make sure you know those.

Question 18

Resolution:

Answer 18

ability to distinguish between 2 closely spaced points

units: line pairs / millimeter

Question 19

primary controlling factors of resolution:

Answer 19

how big focal spot is
how big anode
object film distance
tube film distance

Question 20

Which has best spacial resolution out of all our imaging modalities:

Answer 20

film has best
PSP has worst

Question 21

small focal spot does what to resolution:

Answer 21

increases resolution. prob with going too small, heat occurs.

Question 22

short TFD (short cone technique) : affect on penumbra:

Answer 22

larger penumbra

Question 23

increased OFD (paralleling technique): affect on penumbra:

Answer 23

larger penumbra. lose a bit of resolution.

Question 24

D-speed film vs E-speed film:

Answer 24

E: larger crystals, less radiation, but bc of larger crystals, not as much resolution
D: smaller crystals, more radiation.

Question 25

intensifying screens:

Answer 25

results in unsharpness

Question 26

distortion:

magnification: primary controlling factors

Answer 26

OFD, TFD

shorter TFD will increase magnification, Longer TFD will decrease. For paralleling technique, u always wanna do long TFD. This makes it so u dont cut off root apex that often.

Question 27

distortion:

elongation:

maxillary tooth root is not on radiograph. how to fix this?

Answer 27

tube head go positive.

Question 28

bisecting line technique:

Answer 28

tube head goes perpendicular to bisecting line.