Tomography

Question 1

what does tomography uses motion to show

Answer 1

anatomical structure in plane of interest while blurring / eliminating details of structures above & below

Question 2

what lead to discovery of conventional tomography

Answer 2

limits of 2D images where structures are partially / completely obscured by shadow cast by overlying / underlying structures

Question 3

what happens to structures & tissues outside tomographic section

Answer 3

not visible due to blurring & out of focus

Question 4

the ___ the structure is to x-ray tube / IR, the faster the image will move

Answer 4

nearer

Question 5

The tube is linked to the cassette tray such that the
cassette moves at the same velocity as images of
structures only at the ____

Answer 5

level of the pivot

Question 6

Images of structures at or in all other layers move at a
different velocity from that of the cassette are ____

Answer 6

blurred

Question 7

types of tomographic movement

Answer 7

CLESH
- circular
- linear
- elliptical
- spiral
- hypocycloidal

Question 8

what factors influence blurring

Answer 8

• amplitude of tube travel
• distance from focal plane & film
• tube travel orientation

Question 9

the wider the angle used in tomography, the ___ the section

Answer 9

thinner

Question 10

the narrower the angle used in tomography, the ___ the section

Answer 10

thicker

Question 11

how does amplitude of tube travel affect blurring

Answer 11

more blur w/ wider angle motion

Question 12

how does distance from focal plane affect blurring

Answer 12

more blur at long object-focal plane distances

Question 13

how does distance from film affect blurring

Answer 13

more blur at long object film distances

Question 14

how does orientation of tube travel affect blurring

Answer 14

objects oriented perpendicular to motion

Question 15

how can the cut height be adjusted

Answer 15

by lowering / raising the pivot

Question 16

disadvantages of linear tomography

Answer 16

• high dose
• high cost
• long exposure times
• increased risk of motion artifacts due to increased exposure times

Question 17

conventional tomography is used when ___

Answer 17

plane of interest distinct from surrounding anatomical structures

Question 18

objects closer to x-ray tube moving in opposite direction of receptor will appear ___ on IR

Answer 18

blurry

Question 19

how does panoramic tomography capture the unique horseshoe shaped focal trough of the dental arch

Answer 19

narrow beam rotational tomography but uses 2 or more centers of rotation

Question 20

thickness can be controlled by

Answer 20

tomographic angle & pivot height

Question 21

what is the movement of CR with cassette carrier and film

Answer 21

cassette carrier = opposite to exposure
film = same direction as exposure ensure different part of film exposed

Question 22

contrast lesser than conventional radiography due to tissue blurring

Answer 22

true