Principles of Shadow Cast

Question 1

SOD should be as ____ as possible. FOD (object receptor dist) should be as _____ as possible.

Answer 1

long, short

Question 2

long axis object should be ____ to receptor. Central ray should be ____ to receptor.

Answer 2

parallel, perpendicular

Question 3

focal spots that are ____ produce sharper image

Answer 3

smaller

Question 4

Long x-ray to object dist because?

Answer 4

xrays less divergent and less magnification

Question 5

short object-receptor bc?

Answer 5

less mag, sharper

Question 6

Parallel object-film b/c?

Answer 6

decreases distortion, improves sharpness

Question 7

Too short = beam ___ angulation? Too long = beam ____ angulation

Answer 7

over, under

Question 8

Parallel vs bisecting angle method?

Answer 8

parallel - less distortion

Question 9

Detail means (2)

Answer 9

sharpness and resolution

Question 10

factors affecting detail?

6

Answer 10

focal spot size
SOD
FOD
movement of patient
film speed
density

Question 11

Density effect?

Thickness
Density of anatomy
Atomic #

filtration
collimation
distance

artifacts

Answer 11

LOWER density

…more obstacles

Question 12

Density means?

Answer 12

lighter image is decreased Optical Density (less xrays)

darker image is increased OD

Question 13

Density effect?

kVp increase
mA increase
exposure time
faster film

Processing: time, temp, concentration

Answer 13

HIGHER density

…more power, more processing, longer exposure

Question 14

How does thickness, density of material, and its atomic # affect contrast?
Beam quantity (mA)

Answer 14

greater contrast - more information

Question 15

How does kVP affect contrast?
filtration
mean energy?

Answer 15

All lower contrast - because everything passes through at high energies

Question 16

How can processing effect contrast?

Answer 16

improper time, temp, chemical comcentration

Question 17

What is the right angle technique?

Answer 17

2 radiographs 90 degrees to each other at area of interest

Question 18

SLOB rule?

Answer 18

same lingual opposite buccal

object moves in same direction as tube (entire thing, NOT which way its pointing) –> lingual (axis rotates between buccal and lingual objects)

Question 19

Buccal object rule (BOR) -

Answer 19

in a pair of objects image, image of buccal object moves in the same direction that x-ray beam is directed

If the camera is shooting to the left, the buccal object will “move” to the left. Opposite of SLOB rule–the way its POINTING not the way it moves (which are opposites). If the camera moves right it points more left.