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Principles of Cone Beam Volumetric Tomography

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Presentation on theme: "Principles of Cone Beam Volumetric Tomography"— Presentation transcript:

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’ 4

5 Medical CT

6 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

7 CBCT volume capture 7

8 CBCT volume capture Z Y X

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

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

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 sec for 18 sec scan Enhanced clarity of the images Reduced radiation dose

12 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

13 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

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 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. 18

19 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

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. 21

22 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

23 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

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


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

27 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 µSv Dr Stuart White, UCLA 27

28 Radiation dose Radiation dose of CBCT 20- 250 µSv
The estimated effective patient dose, Planmeca ProMax 3D software version , 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 µSv Same level as 2-10 panoramic images Same level as full mouth series with film Essentially lower than medical CT 28

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 29

30 Dose – Flight 30

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 31

32 The End More information: Erkki Hiltunen Product Manager, X-rays
tel: Mark Niemi tel: More information: Osku Sundqvist Product Manager, Software tel: 4/2011 32

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