CBCT – 2 Flashcards
CBCT Basis-image Capture
Two basis-image capture sequences as the machine
rotates counterclockwise from Position 1 to Position 2
scans routinely capture in the range of 100 to 600 basis
images per rotational scan.
CBCT Image Production
Multiple — projections form the —
basis image
projection data.
CBCT Image Production
A volumetric data set is then the
package of images constructed by an imaging
software program which then displays various image reconstructions
CBCT Image Production
The — reconstruction is the primary reconstruction when volumetric data
is first accessed by a viewing software program
multiplanar
CBCT Image Production
●The number and types of reconstructions (images) are 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
File Formats
2. Scanner software can either store the
volumetric data in either the
(2)
a. proprietary format (unique to vendor)
b. universal format – DICOM
(Digital Imaging andCommunications
in Medicine)
proprietary format (unique to vendor)
InVivo format
universal format – DICOM
(Digital Imaging and Communications
in Medicine)
EggViewer format
DICOM
- standard information transfer method
(file format) for transferring images
and associated information between
devices manufactured by various
vendors
DICOM
stands for
Digital Imaging and Communications
in Medicine
Multiple third-party software available for
imaging DICOM Compatible CBCT
volumetric data
- Anatomage InVivo 3D
- CareStream 3D
- Cybermed 3D
- Dolphin 3D
- (Infinitt) Xelis Dental, Xelis 3D
- Keystone EasyGuide 3D
- NobelClinician
- OnDemand 3D
- OsiriX DICOM viewer
OsiriX DICOM Viewer
most widely used DICOM viewer because
of
global recognition and longevity
OsiriX DICOM Viewer
One of first to fully support the
DICOM
standard for easy integration
Non-DICOM Compatible 3D software
(4)
- Materialise SurgiCase CMF
- Simplant (Materialise)
- Sirona – SICAT ($~400/kit)
- Morita – i-Dixel
Only— data files
aretransferred to and stored in the UMKCSoD MiPACS server
DICOM projection
Proprietary (Native) files are stored in the
capture CPU or its server
skipped
Why are multiple forms of
datasets a problem?
(3)
- 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
Why is this a problem?
It inhibits access to health care by:
(3)
- limiting the access to the
patient’s information - increasing cost and
- delaying time of treatment
Why is this a problem?
* Image transfer is not as simple
as transferring one or a series
of intraoral images
* One transfers …
an entire data
set so the user may access the
image files to construct the
selected images needed. The
images needed will vary
between different practitioners
Why is this a problem?
* CBCT image reconstruction capacity — the ranges of
intraoral, panoramic and skull images
dwarfs
Why is this a problem?
* 2D image reconstructions are not typically stored and
transferred
* Entire volumetric data sets are transferred so practitioners
(2)
– 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 Artifact
(2)
- Beam Hardening
- Streaking
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
backprojection algorithm and these areas will be
“burned out” thus creating dark areas
streak artifact creates the outline of a
“ghost” implant (as
well as other radiopaque streak outlines) in the crosssectional 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
Streak Artifact
* 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 — structures
low density (soft
tissue)
CBCT:
Image Reconstruction
Applications
(5)
- MPR
- Panoramic
- Volume rendering (3D)
- TMJ
- Implant Planning
CBCT Image Capture
and
Data Management:
* Basis Image(s)
* Projection Data –
* Volumetric Data Set –
total set of basis images
image files
managed by image software
- Volumetric Data Set
– image files managed by image software
– Types
(2)
a. proprietary (property of a vendor)
b. universal – DICOM
2D Panoramic Reconstruction
● Imaging software packages can reconstruct panoramic
images from the
● CBCT scan is not indicated solely for
storage data
panoramic
imaging
