principles of cone beam volumetric tomography. planmeca promax 3d models planmeca promax 3d family...

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 applicationsUnique 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

X-ray source

object

Line detector

Movement of translation and axis of rotation

X-ray source

object

axis of rotation

Flat panel detector

CBCT volume capture

CBCT volume capture

Z

Y

X

Medical CT vs. CBVTMedical CT:

Slices are acquired then reconstructed to create the volume

Medical CT vs. CBVTCBCT:

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

• 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.

X-ray Tube – Patient – Image Intensifier – TV Camera – Digital Image

X-ray Tube – Patient – Flat Panel- Digital Image

Modern Flat Panel Technology for maximum performance

3D Technology –Flat PanelPlanmeca ProMax 3D flat panel imaging chain

Conventional imaging chain with Image Intensifier

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

more

less

ComparisonPlanmecaProMax 3D s

Planmeca ProMax 3D

Planmeca ProMax 3D Mid

Planmeca ProMax 3D Max

Voxel size 100 / 200 µm * 100 / 200 / 400 µm

100 / 200 / 400 / 600 µm

100 / 200 / 400 / 600 µm

Max. 3D volume (diam. x height )

Ø50 x 80 mm Ø80 x 80 mm Ø160 x 90 mm Ø230 x 160 mm

Max. 3D volume withstitching, (diam. x height)

Ø90 x 130 mm 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

Motorised patient supportfor vertical movement

No No Yes Yes

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 µSvDr Stuart White, UCLA

Dig. Pan ca 7 µSvFMS 90 uSvDr Sharon Brooks, O of Michigan, ICRP 1990

Dig. Pan 6,7 µSvFMS 84 uSvDr Stuart White 1992, ICRP 1990

Typical panoramic dose 24.5 µSvDr Ludlow, ICRP 2007

Radiation doseThe estimated effective patient dose, Planmeca ProMax 3D software version 1.21.4, Dr. Mika Kortesniemi:

IMAGING PROTOCOL High and Normal Resolution modes

Low Dose mode

IMAGING OBJECT Left 3rd molar Left 3

rd molar

FOV [d cm x h cm] 8 x 8 8 x 8

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• Radiation dose of CBCT 20-

250 µSv• Same level as 2-10 panoramic

images• Same level as full mouth series

with film • Essentially lower than medical

CT

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

ec.europa.eu/energy/nuclear/

radioprotection/publication/doc/136_en.pdf

Age:<10 *310-20 *220-30 *1,530-50 *0,550-80 *0,380+ negligible

Modality: Risk of fatal cancer (per million):Intraoral 0,02 – 0,6Occlusal 0,4Panoramic 0,21 – 1,9Ceph 0,34CT mandible 18,2 – 88CT maxilla 8 – 242

The EndMore information:Erkki HiltunenProduct Manager, X-raystel: +358 20 7795 456 erkki.hiltunen@planmeca.com

Mark NiemiProduct Manager, X-raystel: +358 20 7795 743 mark.niemi@planmeca.com

More information:Osku SundqvistProduct Manager, Softwaretel: +358 20 7795 793osku.sundqvist@planmeca.com

4/2011