panoramic radiography: principles and technique

Question 1

What is the definition of panorama?

Answer 1

An unbroken view of the whole region surrounding an observer

Question 2

What is tomography?

Answer 2

• “Slice image”
• Image of structures lying in a predetermined plane of tissue, blurring detail in images in other planes

Question 3

What happens when a panoramic image is taken?

Answer 3

X-ray source and receptor rotate synchronously around the stationary patient

Question 3

To capture the curve of the jaw, what must the X-ray tube and receptor do?

Answer 3

Have to rotate sequentially about three pivot points, called fixed rotation

Question 4

What is the pivotal point or axis around which the receptor and x-ray tube rotates?

Answer 4

Rotation center

Question 5

What is the function of the collimator?

Answer 5

Restrict x-ray beam to reduce exposure

Question 5

Does a fixed center of rotation have a high or low radiation dose?

Answer 5

High

Question 5

What does a continuously moving center of rotation mean?

Answer 5

X-ray source moves behind the patient, the center of rotation moves along the arc

Question 6

What X-ray tube head is used in a panoramic unit?

Answer 6

IO tube head

Question 7

Where is the beam collimated in a panoramic machine? 2 answers.

Answer 7

X-ray tube
Detector

Question 8

How do structures appear outside of the focal trough?

Answer 8

Blurred, magnified, or reduced in size

Question 8

What does the shape of the focal trough vary with? 2 answers.

Answer 8

Brand of equipment
Image protocol/what type of image you are taking

Question 9

Does the basic principles of image formation change when using films or digital CCD/PSP?

Answer 9

NO

Question 9

Is the image formed sequentially?

Answer 9

Yes

Question 9

The purpose of laser lights on a panoramic unit is to position the patient’s dentition where?

Answer 9

In the focal trough

Question 10

What is the focal trough?

Answer 10

Wide, 3D curved zone where structures in the center of it will be sharp well defined images

Question 11

What are structures between the receptor and center of rotation called?

Answer 11

Real images

Question 12

What are structures between the center of rotation and the x-ray source called?

Answer 12

Ghost images

Question 13

How can ghost images appear? 3 answers.

Answer 13

• Higher level
• Contralateral
• Blurred/significantly magnified

Question 14

How do you decrease magnification? 2 answers.

Answer 14

• Increase source to object distance
• Decrease in object to image receptor distance

Question 15

How do you increase magnification?

Answer 15

• Decrease source to object distance
• Increase in object and image receptor distance

Question 16

What are many ghost images from?

Answer 16

Normal anatomic structures

Question 17

Can ghost images of normal anatomic structures be a normal finding?

Answer 17

yes

Question 18

When are double images created?

Answer 18

Occurs when objects lie posterior to the center of rotation and are intercepted twice by the x-ray beam

Question 19

What are 3 anatomic structures that create double images?

Answer 19

- C-spine - Hyoid - Epiglottis

Question 20

What are four image distortion factors that can occur in pan images?

Answer 20

- X-ray beam angulation - X-ray source to object distance - Path of rotational center - Position of the object within the focal trough

Question 21

What does horizontal magnification depend on?

Answer 21

Position of the object within the focal trough

Question 22

What are a few disadvantages of a pan? 4 answers.

Answer 22

- Lower resolution - Unequal magnification, no linear measurements - Real, ghost, and double images - Patient position can lead to errors/artifacts

Question 23

What causes vertical projection angles?

Answer 23

Negative angulation, objects closer to the source are at a higher level

Question 24

What are a few advantages of a pan? 4 answers.

Answer 24

- Broad coverage of face/teeth - Low radiation dose - Good for patients who are intolerant to intraoral radiography - Patient education and case presentation

Question 25

How should a patient be positioned for a pan? 3 answers.

Answer 25

- Upright - All metal items removed - Stay still

Question 26

What are the 5 major positioning criteria?

Answer 26

- Mid-sagittal plane - Occlusal plane/Frankfort plane - Anterior posterior jaw on bite block - Cervical spine - Tongue and lips

Question 27

What is the mid-sagittal plane of a pan?

Answer 27

Plane should be perpendicular to the floor

Question 28

What is the occlusal or Frankfort plane of a pan?

Answer 28

Imaginary line connecting the infraorbital margin and the external auditory meatus, should be parallel to the floor

Question 29

What is the canine lines of a pan?

Answer 29

Imaginary line connecting the inner cactus of the eye and canine

Question 30

What is the anterior-posterior plane of a pan?

Answer 30

Bite block position, anterior teeth should be in groove to maintain the focal trough

Question 31

What is the cervical spine/neck position of a pan?

Answer 31

Proper neck extension, using dental upward force on the mastoid eminences

Question 32

What does slumping cause in a pan image?

Answer 32

Ghost image

Question 33

What is the lip and tongue position of a pan?

Answer 33

Patient should swallow and hold the tongue against the roof of the mouth

Question 34

What are the 7 diagnostically acceptable pan image requirements?

Answer 34

- Condyles are completely captured and are perpendicular to the inferior aspect of image - Hard palate is flat and parallel to floor - No asymmetry between left and right rami - Even and minimal distortion of teeth - No palatoglossal air shadow - Spinal shadow not obscuring - Aur shadow not obscuring

Question 35

What must all operators wear when using a hand held x-ray device, according to the VA Department of Health?

Answer 35

Protective lead apron

Question 36

How should you hold a NOMAD PID?

Answer 36

With both hands and have backscatter shield parallel to floor

Question 37

Image quality will ____ as you move the PID and ring away from the patient.

Answer 37

Degrade

Question 38

When is the backscatter shield most effective? 3 answers.

Answer 38

- Shield is at outer edge of cone - Close to subject - Parallel to operator

Question 39

What does the inverse square law state?

Answer 39

Intensity of beam is inversely proportional to the square of distance from source