CBCT storage, artifacts and applications

Question 1

how many basis images can be captured per rotational scan?

Answer 1

100-600

Question 2

CBCT image production

Answer 2

multiple basis image projections are used to create the projection data which can then used to form the volumetric data set

Question 3

volumetric data set

Answer 3

the package of images constructed by an imaging software program which then displays various image reconstructions

Question 4

multiplanar reconstruction

Answer 4

●The multiplanar reconstruction is the primary reconstruction when volumetric data is first accessed by a viewing software program

Question 5

number and types of reconstructions are dependent on?

Answer 5

Dependent on the power of the program as specified by the software manufacturer(s).

Question 6

file formats

Answer 6

1. Original scan data (projection data) forms the volumetric data set
2. 2. Scanner software can either store the volumetric data in either the
      a. proprietary format (unique to vendor)
      b. universal format – DICOM
      (Digital Imaging andCommunications in Medicine)

Question 7

DICOM

Answer 7

• standard information transfer method (file format) for transferring images and associated information between devices manufactured by various vendors
• Digital Imaging and Communications in Medicine

Question 8

suffix of volumetric data set that indicates it is DICOM format

Answer 8

.dcm, without this likely in proprietery format

Question 9

software available to image DICOM volumetric data

Answer 9

many possible, 4 at school
* Anatomage InVivo 3D
* CareStream 3D
* NobelClinician
* OsiriX DICOM viewer (FREE)

Question 10

OsiriX DICOM Viewer

Answer 10

• most widely used DICOM viewer because of global recognition and longevity
• One of first to fully support the DICOM standard for easy integration

Question 11

● Only (format) projection data files are transferred to and stored in the UMKC-SoD MiPACS server

Answer 11

DICOM

Question 12

where are Proprietary (Native) files stored?

Answer 12

● Proprietary (Native) files are stored in the
capture CPU or its server

Question 13

DICOM vs pro

Why are multiple forms of datasets a problem?

Answer 13

For final storage, proprietary volumetric data sets were used by 26% of respondents (n =
68)
* Of the 74% storing in a DICOM format, 66% also stored in the proprietary format
* 26 % + [74% x 0.66], 26 % + 48.9% = 74.8% of
respondents save the proprietary format

It inhibits access to health care by:
* limiting the access to the patient’s information with proprietery formats being sent
* increasing cost and delaying time of treatment

Question 14

image transfer of CBCT

Answer 14

• Image transfer is not as simple as transferring one or a series of intraoral images
• One transfers an entire volumetric data set so the user may access the image files to construct the selected images needed. The images needed will vary between different practitioners

Question 15

CBCT image reconstruction capacity and the ranges of intraoral, panoramic and skull images?

Answer 15

CBCT image reconstruction capacity dwarfs the ranges of intraoral, panoramic and skull images

Question 16

are the 2D image reconstructions ever transferred/stored?

Answer 16

• 2D image reconstructions are not typically stored and
  transferred

Question 17

why are entired volumetric sets typically transferred?

Answer 17

– are not limited to a limited number of reconstructions
– can determine their own preferred range of images needed for their diagnostic and treatment needs

Question 18

inherent artifacts of CBCT

Answer 18

• Beam Hardening
• Streaking

Question 19

what are the red and green arrows?

Answer 19

beam hardening (red) and streaking (green) due to metal prothesis

Question 20

Beam Hardening

Answer 20

• is a reconstruction artifact in CT due to the total absorption of low energy photons by metal objects
• however, high energy photons in the heterogenous x-ray beam will create a signal in tissues adjacent the metal structure in the back projection algorithm and these areas will be “burned out” thus creating dark areas

Question 21

beam hardening can simulate:

Answer 21

Effect of beam hardening simulating peri-implantitis and alveolar bone defects in the cross-sectional and parasagittal reconstructions.

Question 22

RCT fillers and CBCT

Answer 22

can cause burnout artifacts and simulate dx

Question 23

complication of this?

streak artifacts form what in reconstructions?

Answer 23

streak artifact creates the outline of a “ghost” implant (as well as other radiopaque streak outlines) in the cross-sectional reconstruction.
The streak artifact makes it more difficult to discern the validity of the cortical bone outlines.

Question 24

streak artifact

Answer 24

• X-rays are heavily attenuated after passing through metal objects which results in very weak signals reaching the detector
• metal shadows in the raw projection data will then introduce streak artifact in the backprojection algorithm reconstructions which introduces the metal streak artifact primarily in low density (soft tissue) structures

Question 25

CBCT image reconstruction applications

Answer 25

• MPR: primary reconstruction
• Panoramic
• Volume rendering (3D)
• TMJ
• Implant Planning

Question 26

CBCT Image Capture and Data Management( data sets)

Answer 26

• Basis Image(s)
• Projection Data – total set of basis images
• Volumetric Data Set – image files managed by image software

Question 27

smaller FOV resolution

Answer 27

higher due to smaller voxels however this also increases grain

Question 28

2D pano reconstruction

Answer 28

● Imaging software packages can reconstruct panoramic images from the storage data
● CBCT scan is not indicated solely for panoramic imaging,

Question 29

2D pano reconstruction and focal trough adjustments

Answer 29

can change the size of the focal trough to sharpen images,
sharper image with smaller trough but less info
less sharp images with larger trough but more info present

Question 30

2d reconstructions can trace what structure

Answer 30

mandibular nn

Question 31

volume rendering

Answer 31

captures surface datda to create 3D images, not very useful to diagnosis mostly a wow factor

Question 32

volume rendering can be used for:

Answer 32

3d implant planning reconstruction or when there are multiple supernumerary teeth

Question 33

airway measurement tool

Answer 33

can measure the V of the airway with Sagittal reconstruction Airway Measurement tool
Program wizard computes the volume of the airway space. Threshold values for compromised airway volumes have not yet been determined for

Question 34

CBCT use for TMJ

Answer 34

can reconstruct the TMJ in different planes for examination, can be done bilaterally

Question 35

CBCT and implant planning

Answer 35

often uses pano reconstructed images and can section the mandbile to trace the path of man nn

Question 36

danger zone of implants

Answer 36

should avoid placing within 2mm of man nn/canal

Question 37

virtual implant placement

Answer 37

can be done with CBCT before actual implant placement to assess prognosis of success (distance from danger zone, length)