6. CT, CBCT, MRI

what are the three possible tomographic projections of 3D imaging?

• axial

• coronal

• sagittal

what is the projection image of 3D imaging?

posterior-anterior view of skull

Which view divides the skull into inferior and superior parts?

axial

Which view divides the skull into an interior and posterior part

Coronal

Which view divides the school into right and left

Sagittal

Horizontal plane

Axial

Frontal plane

Coronal

Medium plane, parallel to suture of skull

Sagittal

axial

axial

coronal

coronal

sagittal

sagittal

which advanced imaging modality?

Cone beam computed tomography

Computed tomography

Magnetic resonance imaging

what shape is CT x-ray beam?

fan

which advanced imaging modality is like pre-cut load? which is like loaf uncut?

CT vs CBCT

what is 3D imaging version of the pixel?

voxel, each is only one shade of gray

the CT number is proportional to what?

the degree of attenuation of x-rays caused by the material w/in that voxel

Bone Hounsfield number

+1000

soft tissue Hounsfield number

+40 - +80

water Hounsfield number

0

fat Hounsfield number

-60 to -100

lung Hounsfield number

-400 to -600

air Hounsfield number

-1000

what do Hounsfield numbers/CT numbers depend on?

density of anatomic structure in the image

explain bone window vs soft tissue window

These are two different settings of CT, which is a major part of the scan. For bone window you can see the details of the bone for soft tissue window. You can see the details of soft tissues. This happens because you can change box content and soft tissues, and all Vauxhall within the bone look the same and vice versa The Hounsfield number is the same despite the visual changes.

Which advanced imaging technique has these advantages:

• Uniform magnification

• Lateral coronal and axial views available

• Post acquisition reformatting may provide additional views

CT

Which advanced imaging technique has these disadvantages:

• Limited availability

• Expensive

• Results and relatively high dose of radiation

• Radiologist required for acquisition and interpretation/read and evaluate

CT

Which advanced imaging technique has these uses:

• Investigation of severe trauma

• Evaluation of neoplasia

• Assessment of chronic inflammation or infection

• used to be standard treatment planning for the edentulous mouth

CT

edentulous

lacking teeth

Definition for which advanced imaging technique: uses x-ray beam that is cone shaped as opposed to fan shaped x-ray be of traditional multi slice CT

CBCT (cone beam computed tomography)

For which advance imaging technique was accessibility addressed in lecture?

CBCT

For which advanced imaging technique is image acquisition:

• Rotating platform/gantry is fixed to x-ray source and image detector

• Source and detector rotate around a fulcrum fixed within the center of ROI

CBCT

ROI

region of interest

Which advanced imaging technique flow is as follows:

• Image acquisition → raw data → image volume

• software needed

CBCT

CT or CBCT:

Multiple rotations of the gantry

CT

CT or CBCT:

More dose

CT

CT or CBCT:

Good contrast resolution good soft tissue detail

CT

CT or CBCT:

Little scatter, due to a narrow beam

CT

CT or CBCT:

More expensive

CT

CT or CBCT:

Single rotation of the gantry

CBCT

CT or CBCT:

Less dose

CBCT

CT or CBCT:

Poor contrast resolution, poor soft tissue detail (good bone)

CBCT

CT or CBCT:

More scatter, due to a wide conical beam

CBCT

CT or CBCT:

Less expensive

CBCT

what is spatial resolution dependent on?

primarily voxel size

smaller voxel = higher resolution

what voxel sixes are available for CBCT?

0.076 mm - 0.6 mm

scout view

a low-resolution, preliminary radiographic image taken during a CT or MRI exam to localize the region of interest and guide the acquisition of the detailed, diagnostic images

what are five reconstructed images from CBCT data?

• MPR

• reconstructed panoramic

• cross-sections (PA)

• reconstructed lateral ephalometrc radiograph

  • ray sum

  • MIP

• volume rendering

  • airway measurement

  • image fusion

  • artifacts

  • metallic beam hardening

  • pt motion

what are the seven visual techniques that can be used for CBCT?

• MPR

  • linear oblique

  • cross-sectional

• ray sum

• volumetric rendering

  • volume rendering

  • MIP

Which reconstructed image from CBCT data describes the following:

• CBCT produces isotropic voxels directly from the data set

• Excellent spatial resolution in all three panels

• Are axial, coronal, sagittal

MPR

from which reconstructed image would one create and change focal trough?

reconstructed panoramic

which reconstructed mage would provide info on:

• osseous morphology of edentulous site

• anatomic quantification

• preexisting pathology

• bone pattern

cross-sectional images of teeth and periapical areas/edentulous areas

can evaluate quality and size of bone, ideal for implant Tx planning

which reconstruction is ideal for implant Tx planing?

cross-sectional imaging of teeth and periapical areas/edentulous areas

CBCT

reconstructed vs normal lateral cephalometric radiograph

reconstructed: made of ray sum and MIP images

regular: magnification, require ruler in image

ray sum imaging CBCT technique

a post-processing technique where rays are cast through the 3D CT dataset, and the attenuation values along these paths are summed to create a 2D image resembling a digital radiograph

slice of orthogonal/MPR image thickened by increasing the number of adjacent voxels included in the display

MIP CBCT technique

maximum intensity projection

involves projecting the voxel with the highest attenuation value onto every view throughout the volume onto a 2D image

clearer view of dense areas like bone and teeth, making it easier to visualize structures; what’s going on

which visualizing technique:

• Achieved by evaluating each voxel value among an imaginary projection ray from observers eyes with a particular volume of interest and representing only the highest value at the display value

• voxel intensities that are below an arbitrary threshold our eliminated

MIP

which CBCT reconstruction?

• allows visualization of volumetric data by selective display of voxels w/in a data set

volume rendering (remove content = better view)

what are four things you can see through volume rendering CBCT reconstruction?

• airway measurement

• image fusion

• artifacts

• pt motion

how many panoramic scans are equal to one CBCT scan?

9.4

large FOV (field of view) avg CBCT effective dose

131

medium FOV (field of view) avg CBCT effective dose

88

small FOV (field of view) avg CBCT effective dose

34

voxel size changes with dose how? low dose mode?

smaller voxel size (better) = higher dose

there is a “low dose mode”

• 96kV

• 2.5 mA

• 4.5

what are the seven relevant CBCT applications?

• dental implant planning - cross-sectional imaging

• TMJ assessment

• evaluation of osseous and dental pathology

• endo: root canals

• ortho: unerupted tooth position

• position of impacted supernumerary teeth - small FOV

• locating impacted third molar & proximity to IAN canal (inferior alveolar nerve)

why is buccal lingual thickness important?

• dental implants

• tooth extraction

• endo - max sinus, IAN canal

• ortho movement

what are the four anatomic landmarks that need to be avoided/prevent injury of?

• Floor of the maxillary sinus

• Nasopalatine canal

• Inferior alveolar nerve canal

  • Anterior extension of inferior alveolar canal

  • accessory neurovascular canals

• Mental neurovascular canal and foreman

what are these morphology of?

• Knife edge ridges

• Submandibular fossa

• Developmental variation

• Post extraction irregularity

• Enlarged marrow spaces

osseous morphology of edentulous spaces

what are some anatomic quentifiaions of CBCT?

• Dimensions for implant

• Placement: height, width, and edentulous span

• Orientation access of viola Ridge height

can site of CBCT have preexisting pathology?

no site should be pathology free

what is the relevant anatomy for area of #13?

L max sinus (floor, buccal cortical plate, crest of ridge)

how does one assess TMJ?

panoramic radiograph and MRI

what are panoramics useful for concerning TMJ?

gross osseous changes of condyles

what are cross-sectional images useful for concernin TMJ?

• Allows thorough assessment of TMJs

  • Articular surface of the condoles

  • Glenoid fossa

  • Articular eminence

    • corticated borders (thinning, missing)

• Position of condyles within the fossa

• Assess relationship of condo to the Glenoid fossa

measure degen changes

what are MRIs useful for concerning TMJ?

evaluation of soft tissue structures, specifically articular disc which lies between the mandibular condyle and the mandibular fossa of the temporal bone

Assessing buccal-lingual expansion caused by the lesion

Association of the lesion and its effect on inferior alveolar canal

osseous eval

what can CBCT detect or endo treatments?

missed canal

describe location of nasopalatine canal

what is this?

labial undercut

a triangular indentation in the maxilla or tissue in the area of the lip. more common in edentulous (toothless) individuals, can cause problems when a patient receives a complete denture, as it may interfere with the denture's stability, cause tissue trauma, or lead to poor facial aesthetics due to excessive flange thickness. 

what are these characteristics of?

• These are smooth depressions on the facial surface of the anterior maxilla

• Dental implants could perforate through the undercut during placement

labial undercut

what are these characteristics of?

• mandibular posterior

• dental implants could perforate through the undercut during placement

lingual undercut