Panoramic Radiography

Question 1

what is the principle of panoramic/ OPT

Answer 1

the x-ray source and film are connected together and they rotate simultaneously around the patient to produce an image. that image shows the whole dentition.

Question 2

what is the focal trough

Answer 2

within the image there is a focal trough which represents the sharpest part of the image (it is horse shoe shaped/curved). everything outside of this focal trough is blurry/ not clear.

Question 3

what are the patient positioning requirements in opt?

Answer 3

the patient needs to be aligned so that their head lies within the focal trough

Question 4

what is a ghost image and how is it generated

what is the opposite of the ghost image

Answer 4

a ghost image is larger/ distorted, higher, blurred, and on the opposite side of the image.

generated by anything between the centre of rotation and the x-ray source. e.g. –> earrings, tongue studs. why?

because the x-ray will rotate around therefore everything will be imaged twice: once when the receptor is close to the object (real image) and once when the receptor is further away from object you are trying to image (ghost image)

Question 5

what are possible positioning errors relating to focal trough?

Answer 5

1. chin too down = distorted occlusal plane= lower incisors out of focus= smiley face
2. chin too up= distorted occlusal plane= upper incisors out of focus= grumpy face
3. too close to image receptor (aka too far from the x-ray source)= narrow, out of focus anterior teeth, will see cervical spine.
4. too far from image receptor (aka too close to the x-ray source)= magnified, out of focus anterior teeth
5. off centre (one side is too forward and the other is too back)= the molars closest to the image receptor will be smaller and those further away will be enlarged/ magnified

Question 6

what are the advantages of opt

Answer 6

shows the whole dentition

lower dose

quick

well tolerated by pts.

really good if pt. has gag reflex or cant fully open mouth/tmj condition

Question 7

what are the disadvantages of opt

Answer 7

pt. positioning- need to ensure their head is within the focal trough.

superimposition of soft tissue and air shadows can cause mis-interpretation/ difficult to interpret.

resolution of detail not as good as intral oral techniques like bitewing or periapical.

Question 8

what are the clinical indications for using a opt

Answer 8

when bone loss/ bony lesions etc. is not being shown on intra-orals.

grossly neglected dentition

assessment of 8’s

orthodontics

mandibular fractures

Question 9

what are the 4 white lines you should always see in your opt?

Answer 9

1, zygomatic buttress

2. posterior wall of maxillary sinus.
3. floor of maxillary sinus
4. hard palate