03/01/17 Extraoral Imaging

Question 1

What is a ghost image?

Answer 1

-Objects that are located between xray source and center of rotation cast

Question 2

If the patient is to far forward in a pano radiograph what does the image look like?

Answer 2

• The central teeth are slightly blurry because they are out of the focal point
• The spine if covering the TMJ

Question 3

If the chin is tipped down what happens to the lower teeth in a pano?

Answer 3

-They get fore shortened

Question 4

If the chin is to high in a pano what does the slight smile of the teeth look like?

Answer 4

-The slight smile isn’t there, it is more flattened

Question 5

If the head is twisted in the pano how might you know?

Answer 5

-The widths of the rami on the mandible will be different

Question 6

What does a cephalometric feature on a pano machine show you?

Answer 6

-Lateral skull film

Question 7

What dental specialty uses cephalometric features most commonly?

Answer 7

-Orthodontists

Question 8

What is a scanning technique that produces detailed images of organs and structures in the body that produces no ionizing radiation?

Answer 8

-MRI

Question 9

What is a PET scan?

Answer 9

-Detects gamma rays emitted by a tracer that is introduced into the body

Question 10

What type of image combines the use of x-rays with computer technology to produce cross-sectional images of the body?

Answer 10

-CT scan

Question 11

What are three views that CBCT allows you to see?

Answer 11

• Coronal
• Axial
• Sagital

Question 12

What angle does a pano take the radiograph at?

Answer 12

-30 degrees

Question 13

What do objects that are located between the xray source and center of rotation cast?

Answer 13

-Ghost image

Question 14

Where do you typically see ghost images?

Answer 14

-Opposite side of the anatomic level at a higher level

Question 15

What is the area of sharpest area of focus called when taking a pano?

Answer 15

-Focal trough

Question 16

If you don’t see the spine framing the edge in the pano what is wrong with patient positioning?

Answer 16

-To far back

Question 17

If you see a little bit of spine framing the edge, and the center of the pano is washed out by the spine what is wrong with the patient positioning?

Answer 17

-Slumped

Question 18

If you see a big smile in the pano radiograph and the mandibular centrals are obliterated, what is wrong with patient positioning?

Answer 18

-Chin is tipped down

Question 19

If you have a really flat image of the teeth and can see the hard palate covering the roots of the teeth, what is wrong with the positioning of the patient?

Answer 19

-Chin too high

Question 20

How can you tell if the patients head was twisted during the pano?

Answer 20

-Asymmetrical image

Question 21

What is a voxel?

Answer 21

-Volume pixel

Question 22

Where do you get resolution with a CBCT?

Answer 22

-Voxels

Question 23

-More radiation is required to get a higher resolution in CBCT

Answer 23

True

Question 24

Does a larger (.4) or smaller (.1) voxel give you higher/better resolution?

Answer 24

-smaller

Question 25

Does a larger (.4) or smaller (.1) voxel give you less radiation?

Answer 25

-Larger

Question 26

T/F When taking a CBCT you should select only as much volume as you need to view

Answer 26

True

Question 27

T/F The larger the volume that higher the dose to the patient

Answer 27

True

Question 28

What gives you the least amount of radiation when determining volume and voxel size?

Answer 28

Smallest volume with largest voxel size