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’ 4

Medical CT

Medical CT vs CBVT Movement of translation and axis of rotation Flat panel detector axis of rotation Line detector object object X-ray source X-ray source

CBCT volume capture 7

CBCT volume capture Z Y X

Medical CT vs. CBVT Medical CT: Slices are acquired then reconstructed to create the volume 9

Medical CT vs. CBVT CBCT: The volume is acquired then slices are reconstructed from the volume 10

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 SCARA! 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. 18

3D Technology –Flat Panel Planmeca ProMax 3D flat panel imaging chain Conventional imaging chain with Image Intensifier X-ray Tube – Patient – Flat Panel - Digital Image X-ray Tube – Patient – Image Intensifier – TV Camera – Digital Image Modern Flat Panel Technology for maximum performance 19

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. 21

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 22

Comparison Planmeca ProMax 3D s ProMax 3D ProMax 3D Mid ProMax 3D Max Voxel size 100 / 200 µm * 100 / 200 / 400 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 with stitching, (diam. x height) Ø90 x 130 mm Ø150 x 130 mm Ø160 x 160 mm Ø230 x 260 mm Stitching, vertical Yes Stitching, horizontal No SmartPan imaging Dimax Panoramic imaging Optional Dimax Cephalostat Motorised patient support 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 26

Radiation dose Dig. Pan ca 7 µSv Medical CT 1200-3300 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 Medical CT 1200-3300 µSv Dr Stuart White, UCLA 27

Radiation dose Radiation dose of CBCT 20- 250 µSv The 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 FOV [d cm x h cm] 8 x 8 TUBE VOLTAGE [kV] 84 TUBE CURRENT [mA] 12 8 EXPOSURETIME [s] 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 (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 28

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 29

Dose – Flight www.gsf.de/epcard 30

Dose – Risks Modality: Risk of fatal cancer (per million): Intraoral 0,02 – 0,6 Occlusal 0,4 Panoramic 0,21 – 1,9 Ceph 0,34 CT mandible 18,2 – 88 CT maxilla 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 31

The End More information: Erkki Hiltunen Product Manager, X-rays tel: +358 20 7795 456 erkki.hiltunen@planmeca.com Mark Niemi tel: +358 20 7795 743 mark.niemi@planmeca.com More information: Osku Sundqvist Product Manager, Software tel: +358 20 7795 793 osku.sundqvist@planmeca.com 4/2011 32