Panoramic Radiography: Principles & 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 4

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

Answer 4

Rotation center

Question 5

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

Answer 5

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

Question 6

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

Answer 6

High

Question 7

Do we currently use a fixed center of rotation in clinic?

Answer 7

No, not a modern technique

Question 8

What does a continuously moving center of rotation mean?

Answer 8

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

Question 9

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

Answer 9

IO tube head

Question 10

What is the function of the collimator?

Answer 10

Restrict x-ray beam to reduce exposure

Question 11

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

Answer 11

• X-ray tube
• Detector

Question 12

Is the image formed sequentially?

Answer 12

Yes

Question 13

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

Answer 13

No

Question 14

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

Answer 14

In the focal trough

Question 15

What is the focal trough?

Answer 15

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

Question 16

How do structures appear outside of the focal trough?

Answer 16

Blurred, magnified, or reduced in size

Question 17

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

Answer 17

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

Question 18

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

Answer 18

Real images

Question 19

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

Answer 19

Ghost images

Question 20

How can ghost images appear? 3 answers.

Answer 20

• Higher level
• Contralateral
• Blurred/significantly magnified

Question 21

How do you decrease magnification? 2 answers.

Answer 21

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

Question 22

How do you increase magnification?

Answer 22

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

Question 23

What are many ghost images from?

Answer 23

Normal anatomic structures

Question 24

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

Answer 24

Yes

Question 25

When are double images created?

Answer 25

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

Question 26

What are 3 anatomic structures that create double images?

Answer 26

- C-spine - Hyoid - Epiglottis

Question 27

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

Answer 27

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

Question 28

What does horizontal magnification depend on?

Answer 28

Position of the object within the focal trough

Question 29

What causes vertical projection angles?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

- Upright - All metalic items removed - Stay still

Question 33

What are the 5 major positioning criteria?

Answer 33

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

Question 34

What is the mid-sagittal plane of a pan?

Answer 34

Plane should be perpendicular to the floor

Question 35

What is the occlusal or Frankfort plane of a pan?

Answer 35

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

Question 36

What is the canine lines of a pan?

Answer 36

Imaginary line connecting the inner cactus of the eye and canine

Question 37

What is the anterior-posterior plane of a pan?

Answer 37

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

Question 38

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

Answer 38

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

Question 39

What does slumping cause in a pan image?

Answer 39

Ghost image

Question 40

What is the lip and tongue position of a pan?

Answer 40

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

Question 41

What are the 7 diagnostically acceptable pan image requirements?

Answer 41

- 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 shaddow - Spinal shadow not obscuring - Aur shadow not obscuring

Question 42

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

Answer 42

Protective lead apron

Question 43

How should you hold a NOMAD PID?

Answer 43

With both hands and have backscatter shield parallel to floor

Question 44

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

Answer 44

Degrade

Question 45

When is the backscatter shield most effective? 3 answers.

Answer 45

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

Question 46

What does the inverse square law state?

Answer 46

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