Presentation on theme: "Principles of Cone Beam Volumetric Tomography. Planmeca ProMax 3D Models Planmeca ProMax 3D family offers a solution for the most demanding imaging needs,"— Presentation transcript:
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 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
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 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
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 Panel Planmeca ProMax 3D flat panel imaging chain Conventional imaging chain with 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
Comparison Planmeca ProMax 3D s Planmeca ProMax 3D Planmeca ProMax 3D Mid Planmeca ProMax 3D Max Voxel size100 / 200 µm *100 / 200 / 400 µm 100 / 200 / 400 / 600 µm Max. 3D volume (diam. x height ) Ø50 x 80 mmØ80 x 80 mmØ160 x 90 mmØ230 x 160 mm Max. 3D volume with stitching, (diam. x height) Ø90 x 130 mmØ150 x 130 mmØ160 x 160 mmØ230 x 260 mm Stitching, verticalYes Stitching, horizontalYes No SmartPan imagingYes No Dimax Panoramic imaging Optional No Dimax CephalostatOptional No Motorised patient support for vertical movement No 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 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 , Dr. Mika Kortesniemi: IMAGING PROTOCOLHigh and Normal Resolution modes Low Dose mode IMAGING OBJECTLeft 3 rd molar FOV [d cm x h cm]8 x 8 TUBE VOLTAGE [kV]84 TUBE CURRENT [mA]128 EXPOSURETIME [s]122.8 CURRENT TIME PRODUCT [mAs] CURRENT TIME PROFILE [MIN(mAs) / MAX(mAs)] Effective dose [mSv] (ICRP 1990) Effective dose [mSv] (ICRP 2007) 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
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