Chapter 23 Localization techniques, Chapter 8 Digital Imaging, Chapter 27 Three-dimensional digital imaging

can tell us how forward how far back or how inferior or superior

can tell us anterior or posterior

but cant like us inferior or superior

Purpose of localization

foreign bodies, impacted, unerupted teeth, retained roots, root positions, salivary stones, jaw fractures, broken needles and instruments, restorative materials

buccal object rule

expose 1st image (PA or bw)

take a second image with a different H or V angulation aka same area different angle

compare images to see how the object shifted in the image

SLOB

lingual

right angle technique

buccal

lingual

lingual

buccal

Digital

Scintillating layer

stars sparkling glowing

converts x-ray photons to light photons

Charge-coupled device

pixels abut each other

complementary metal oxide semiconductor/ active pixel sensor (CMOS/APS)

each pixel surrounded by amplifiers

contrast resolution (range of grays)

8- bit (2^8) is 256 shades

superior to human eye

spatial resolution (line pairs/ millimeter)

digital - 6-22 lp/mm

film - 20 lp/mm

human eye 6-8 lp/mm w/out mag

Types of digital imaging

direct digital imaging (CCD, CMOS)

or

indirect digital imaging ( Digitizing tradition film images, photostimulable phosphor imaging)

3-D imaging

CBCT scan - cone beam, computed tomography

cone-shaped x-ray beam, rotates around the patients head

scan time 7-30 seconds

contrast res > bit depth

spatial res - voxels 3-dimensional pixels

2D vs 3D

unable to assess from this single image the objects buccal-lingual position relative to the teeth

traditional medical CT

computed tomography

fan shaped x-ray beam rotates around pt

rotations move down the section of anatomy of interest

layers/ slices of images are stacked with software during image reconstruction

Coronal plane

axial plane

sagittal plane

anatomical/ orthogonal projections

multiplanar reconstruction/ reformation

volumetric rendering

commons uses of 3D imaging

improved interpretation diagnosis and treatment planning of dental care

implant placement

extraction or exposure of impacted teeth

definition of anatomic structures

endo assessment

airway and sinus analysis

eval of TMJ disorders

ortho eval

eval of lesions/ abnormalities

trauma eval

Training for CBCT

American academy of oral and maxillofacial radiology - CBCT interpreted by board certified oral and maxillofacial radiologist

intersocietal accreditation commission -min standards when using dental cbct

patient preparation

explain to pt

ensure glasses, jewelry, appliances etc, are removed

chin/ head support for pt comfort and stability

use lasers to align pt

advantages of CBCT

lower radiation dose than CT

easy to save and share date

brief scanning tim e

accurate anatomical images

disadvantages of CBCT

patient movement, small FOV could limit view, cost, training, exposure