Principles of Cone Beam Volumetric Tomography

1. Principles of Cone Beam Volumetric Tomography

2. 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.

3. 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

4. 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’

5. Medical CT

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

7. CBCT volume capture

8. CBCT volume capture Z Y X

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

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

11. 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

12. 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 ProMax 3D Max & Mid Scanning

13. The shift of whole c-arm remains the acquisition geometry constant and produces better final image Asymmetric off-set scanning Sensor shift changes the acquisition geometry and reduces the final image quality SCARA!

14. Back projection – basic images

15. Back projection

16. 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

17. 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

18. Pulsed X-ray Pulsed X-ray produces sharp images with less dose.

19. Planmeca ProMax 3D flat panel imaging chain Conventional imaging chain with Image Intensifier 3D Technology –Flat Panel 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

20. Image intensifier

21. 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.

22. 3D technology – Tube Current Modulation less more • Different attenuation properties across and along the patient's head • Tube current (mAs) can be dynamically adjusted • Reduces patient dose and improves image quality

23. Comparison

24. CBCT vs. Medical CT Cone Beam Imaging is: • Faster • Smaller • Safer (lower dose) • Less expensive • More convenient • Dentally specific • Higher resolution • Better image quality

25. WHAT ARE THE DOSES?

26. Radiation dose International Commision on Radiological Protection, Standards for absorbed dose from 1990 and 2007

27. Radiation dose 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 Medical CT 1200-3300 µSv Dr Stuart White, UCLA

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

29. 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

30. Dose – Flight www.gsf.de/epcard

31. 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

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