Transcript CBCT principles presentation

Principles of Cone Beam
Volumetric Tomography
Planmeca ProMax 3D Models
Planmeca ProMax 3D family offers a solution for the most
demanding imaging needs, producing various imaging sizes
with one concept – an ideal imaging size for different
maxillofacial applications.
Extended applications
Unique new imaging
capabilities for:
•Implant planning
•Oral surgery
•Impacted teeth
•3rd molar extractions
•Occlusion analysis
•TMJ analysis
•Periodontics
•Airway studies
Emerging new diagnostic
applications
3D technology
•CBCT - Cone Beam
Computed Tomography
•CBVT - Cone Beam
Volumetric Tomography
•DVT – Digital Volume
Tomography
•A technological advance
from traditional ‘CAT Scan’,
‘medical CT’ or ‘fan beam
CT’
Medical CT
Medical CT vs CBVT
Movement of translation
and axis of rotation
axis of rotation
Line detector
object
object
X-ray source
X-ray source
Flat panel
detector
CBCT volume capture
CBCT volume capture
Z
Y
X
Medical CT vs. CBVT
Medical CT:
Slices are acquired then reconstructed to
create the volume
Medical CT vs. CBVT
CBCT:
The volume is acquired then slices are
reconstructed from the volume
ProMax 3D technology
•Stroboscopic effect, images
taken using short X-ray pulses
during the scan
•300/450 images taken during
the scan
•Cumulative exposure time 2.8
-12 sec for 18 sec scan
•Enhanced clarity of the
images
•Reduced radiation dose
ProMax 3D Max & Mid Scanning
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Symmetric scanning
C-arm rotates
Magnification 1.8x
Scan angle 200 deg
300 frames
Max. volume Ø100 x 130
mm
• Asymmetric off-set
scanning
• Elbow arm rotates
• Magnification 1.44x
• Scan angle 360 deg
• 450 frames
• Max. volume Ø230 x 160
mm
Asymmetric off-set scanning
Sensor shift changes the
acquisition geometry and
reduces the final image
quality
The shift of whole c-arm
remains the acquisition
geometry constant and
produces better final
image
Back projection – basic images
Back projection
ProMax 3D Technology
3D image volume is a
cylinder
 Cylinder consists of
more than 120 million
voxels
 Voxel size
0.1 x 0.1 x 0.1 mm,
0.2 x 0.2 x 0.2 mm,
0.4 x 0.4 x 0.4 mm or
0.6 x 0.6 x 0.6 mm

Isotropic voxel
• CBVT has always an isotropic voxel
• The reconstruction can produce any
size of voxel
• The voxel is always perfect cube
• The measurements are exact
• Voxel size is typically 0.1 – 0.5 mm
• CT has an anisotropic voxel
• The voxel is always a “brick”
• The pitch (= distance between spiral
rounds = layer thickness) varies and
causes distortion in the 3D
measurements.
• The layer thickness is typically 0.5 –
0.8 mm
Pulsed X-ray
Pulsed X-ray produces sharp images with less dose.
3D Technology –Flat Panel
Planmeca ProMax 3D flat panel
imaging chain
X-ray Tube – Patient – Flat Panel
- Digital Image
Conventional imaging chain with
Image Intensifier
X-ray Tube – Patient – Image Intensifier – TV Camera –
Digital Image
Modern Flat Panel Technology for maximum performance
Image intensifier
3D Technology – Flat Panel
• Image intensifier has both
distortion and brightness
non-uniformity which is
absent from the flat panel
detector
• Image intensifier needs
periodical maintenance. It
has limited life span 3-6
years.
• It is sensitive to magnetic
or electrical fields.
• It is over 60 years old
technology.
3D technology – Tube Current
Modulation
• Different attenuation
properties across and
along the patient's head
• Tube current (mAs) can
be dynamically adjusted
• Reduces patient dose
and improves image
quality
less
more
Comparison
Planmeca
ProMax 3D s
Planmeca
ProMax 3D
Planmeca
ProMax 3D Mid
Planmeca
ProMax 3D Max
100 / 200 µm *
100 / 200 / 400
µm
100 / 200 / 400 /
600 µm
100 / 200 / 400 /
600 µm
Max. 3D volume (diam. x Ø50 x 80 mm
height )
Ø80 x 80 mm
Ø160 x 90 mm
Ø230 x 160 mm
Max. 3D volume with
Ø90 x 130 mm
stitching, (diam. x height)
Ø150 x 130 mm Ø160 x 160 mm
Ø230 x 260 mm
Stitching, vertical
Yes
Yes
Yes
Yes
Stitching, horizontal
Yes
Yes
No
No
SmartPan imaging
Yes
Yes
Yes
No
Dimax Panoramic
imaging
Optional
Optional
Optional
No
Dimax Cephalostat
Optional
Optional
Optional
No
No
Yes
Yes
Voxel size
Motorised patient support No
for vertical movement
CBCT vs. Medical CT
Cone Beam Imaging is:
• Faster
• Smaller
• Safer (lower dose)
• Less expensive
• More convenient
• Dentally specific
• Higher resolution
• Better image quality
WHAT ARE THE DOSES?
Radiation dose
International Commision on Radiological
Protection, Standards for absorbed dose from
1990 and 2007
Radiation dose
Medical CT 1200-3300 µSv
Dr Stuart White, UCLA
Dig. Pan ca 7 µSv
FMS 90 uSv
Dr Sharon Brooks, O of Michigan, ICRP 1990
Dig. Pan 6,7 µSv
FMS 84 uSv
Dr Stuart White 1992, ICRP 1990
Typical panoramic dose 24.5 µSv
Dr Ludlow, ICRP 2007
Radiation dose
The estimated effective patient dose, Planmeca ProMax 3D software version
1.21.4, Dr. Mika Kortesniemi:
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Radiation dose of CBCT 20250 µSv
Same level as 2-10 panoramic
images
Same level as full mouth series
with film
Essentially lower than medical
CT
IMAGING PROTOCOL
High and Normal
Resolution modes
Low Dose
mode
IMAGING OBJECT
Left 3rd molar
Left 3rd molar
FOV [d cm x h cm]
8x8
8x8
TUBE VOLTAGE [kV]
84
84
TUBE CURRENT [mA]
12
8
EXPOSURETIME [s]
12
2.8
CURRENT TIME PRODUCT
[mAs]
144
22.4
CURRENT TIME PROFILE
[MIN(mAs) / MAX(mAs)]
1.0
0.3
Effective dose [mSv]
(ICRP 1990)
0.122
0.021
Effective dose [mSv]
(ICRP 2007)
0.252
0.045
Dose – Radon, background,
smoking
US Study:
• Average yearly dose of 2070 µSv from
radon
• Average yearly dose of 320 µSv from
smoking
• Average yearly dose of 4000 µSv from
background radiation in Denmark
Dose – Flight
www.gsf.de/epcard
Dose – Risks
Modality:
Intraoral
Occlusal
Panoramic
Ceph
CT mandible
CT maxilla
Risk of fatal cancer (per million):
0,02 – 0,6
0,4
0,21 – 1,9
0,34
18,2 – 88
8 – 242
Age:
<10 *3
10-20
*2
20-30
*1,5
30-50
*0,5
50-80
*0,3
80+ negligible
ec.europa.eu/energy/nuclear/radioprotection
/publication/doc/136_en.pdf
The End
More information:
Erkki Hiltunen
Product Manager, X-rays
tel: +358 20 7795 456
[email protected]
More information:
Osku Sundqvist
Product Manager, Software
tel: +358 20 7795 793
[email protected]
Mark Niemi
Product Manager, X-rays
tel: +358 20 7795 743
[email protected]
4/2011