CBCT storage, artifacts and applications Flashcards
how many basis images can be captured per rotational scan?
100-600
CBCT image production
multiple basis image projections are used to create the projection data which can then used to form the volumetric data set
volumetric data set
the package of images constructed by an imaging software program which then displays various image reconstructions
multiplanar reconstruction
●The multiplanar reconstruction is the primary reconstruction when volumetric data is first accessed by a viewing software program
number and types of reconstructions are dependent on?
Dependent on the power of the program as specified by the software manufacturer(s).
file formats
- Original scan data (projection data) forms the volumetric data set
- 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)
- Scanner software can either store the volumetric data in either the
DICOM
- standard information transfer method (file format) for transferring images and associated information between devices manufactured by various vendors
- Digital Imaging and Communications in Medicine
suffix of volumetric data set that indicates it is DICOM format
.dcm, without this likely in proprietery format
software available to image DICOM volumetric data
many possible, 4 at school
* Anatomage InVivo 3D
* CareStream 3D
* NobelClinician
* OsiriX DICOM viewer (FREE)
OsiriX DICOM Viewer
- most widely used DICOM viewer because of global recognition and longevity
- One of first to fully support the DICOM standard for easy integration
● Only (format) projection data files are transferred to and stored in the UMKC-SoD MiPACS server
DICOM
where are Proprietary (Native) files stored?
● Proprietary (Native) files are stored in the
capture CPU or its server
DICOM vs pro
Why are multiple forms of datasets a problem?
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
image transfer of CBCT
- 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
CBCT image reconstruction capacity and the ranges of intraoral, panoramic and skull images?
CBCT image reconstruction capacity dwarfs the ranges of intraoral, panoramic and skull images
are the 2D image reconstructions ever transferred/stored?
- 2D image reconstructions are not typically stored and
transferred
why are entired volumetric sets typically transferred?
– are not limited to a limited number of reconstructions
– can determine their own preferred range of images needed for their diagnostic and treatment needs
inherent artifacts of CBCT
- Beam Hardening
- Streaking
what are the red and green arrows?
beam hardening (red) and streaking (green) due to metal prothesis
Beam Hardening
- 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
beam hardening can simulate:
Effect of beam hardening simulating peri-implantitis and alveolar bone defects in the cross-sectional and parasagittal reconstructions.
RCT fillers and CBCT
can cause burnout artifacts and simulate dx
complication of this?
streak artifacts form what in reconstructions?
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.
streak artifact
- 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
CBCT image reconstruction applications
- MPR: primary reconstruction
- Panoramic
- Volume rendering (3D)
- TMJ
- Implant Planning
CBCT Image Capture and Data Management( data sets)
- Basis Image(s)
- Projection Data – total set of basis images
- Volumetric Data Set – image files managed by image software
smaller FOV resolution
higher due to smaller voxels however this also increases grain
2D pano reconstruction
● Imaging software packages can reconstruct panoramic images from the storage data
● CBCT scan is not indicated solely for panoramic imaging,
2D pano reconstruction and focal trough adjustments
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
2d reconstructions can trace what structure
mandibular nn
volume rendering
captures surface datda to create 3D images, not very useful to diagnosis mostly a wow factor
volume rendering can be used for:
3d implant planning reconstruction or when there are multiple supernumerary teeth
airway measurement tool
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
CBCT use for TMJ
can reconstruct the TMJ in different planes for examination, can be done bilaterally
CBCT and implant planning
often uses pano reconstructed images and can section the mandbile to trace the path of man nn
danger zone of implants
should avoid placing within 2mm of man nn/canal
virtual implant placement
can be done with CBCT before actual implant placement to assess prognosis of success (distance from danger zone, length)
