CBCT

Question 1

what are the 2 main parts of CBCT?

Answer 1

x-ray beam cone on one side and pyramidal/cone shaped beam on other side

Question 2

how should pt be positioned during CBCT?

Answer 2

head upright with frankfort horizontal to floor

Question 3

list benefits of CBCT over plain radiographs

Answer 3

no superimposition
can view the subject from any angle
no magnification/distortion
allows for volumetric 3D reconstruction

Question 4

list disadvantages of CBCT compared to plain radiographs

Answer 4

inc radiation dose to pt
lower spatial resolution - not as sharp
more expensive
images more complicated to manipulate and interpret
requires additional training

Question 5

benefits of CBCT over CT

Answer 5

lower radiation dose
sharper - higher resolution
cheaper
smaller footprint

Question 6

benefits of CT over CBCT

Answer 6

can differentiate soft tissues better
cleaner images - less noise/fuzziness
larger FOV possible

Question 7

list common uses of CBCT in dentistry

Answer 7

assessing proximity of lower wisdom teeth to ID canal
implant planning
endo
ortho - assessing external root resorption next to impacted teeth
assessing large cystic jaw lesions

Question 8

name 3 orthoganol planes to view CBCT

Answer 8

axial - from above/below
sagittal - side on
coronal - face on

Question 9

list 3 image factors/variable set prior to taking CBCT

Answer 9

FOV - inc FOV inc dose
voxel size - lower voxel inc dose and scan time
acquisition time - 5-10 seconds (not instantaneous)

Question 10

FOV & voxels size for endo and implant planning

Answer 10

endo = smallest FOV and small voxel size
implant planning = larger voxel size, FOV depends

Question 11

how do doses compare between CBCT, CT, DPT and intraoral?
how much higher is CBCT compared to DPT?

Answer 11

CT largest>CBCT>DPT>intraoral
CBCT 2-3x the dose of DPT

Question 12

what are movement and streak artefacts?

Answer 12

movement - blurriness cause by pt moving during exposure
streak - occurs around high attenuation objects i.e. metals

Question 13

are CBCTs useful for caries diagnosis? why?

Answer 13

no - due to streak artefacts from heavily restored dentitions/appliances
the radiolucencies produced mimic caries

Question 14

list contraindications for CBCT

Answer 14

if plain radiographs sufficient
if we require soft tissue imaging - looking for malignancies of infection spreading through soft tissues
if high risk of artefacts - heavily restored, post crowns
pt factors - cant stay still, unable to fit into machine

Question 15

what training & refresher is required for CBCT?

Answer 15

post grad
refresher every 5 years