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Cone Beam CT
An alternative approach to extremity imaging?
Peter Sharpe Roisin Dobbin-Stacey
Chief Executive PET/CT – CT Manager
Medical charity
Providing MRI , PET/CT, CBCT & DXR
65,000 patients annually
Research – Fund and participate
Provide - Training & education.
Cobalt – Who are we?
Objectives – to innovate
First:
1.5T Mobile MRI
High-field Open MRI
Open PET/CT
3.0T Mobile MRI
ISAS accreditation
Wide bore digital mobile MRI
Flow PET/CT technology
Carestream - MyVue & VueMotion.
Cobalt – Who are we?
Why CBCT for Cobalt?
Good fit – Innovation and research
Good partnership with Carestream
Very positive reviews from a range of international ‘trade sites’
One stop orthopaedic clinics – DXR weight bearing
Research opportunity.
What is Cone Beam CT Traditional CT
Cone Beam CT
A narrow slice of the patient is imaged
with a fan-beam of x-rays and multiple
rotations; z direction typically has
lower resolution
A large-area flat panel detector images
an extended volume of the patient in a
single rotation; same (isotropic)
resolution in all 3 directions
What is Cone Beam CT
Single
Source
3 Source
Increases reconstruction volume by ~50%
Reduces “cone beam” artifact
Enables future advanced acquisition
protocols
o Dual energy
Why did Carestream develop CBCT?
OnSight Extremity CBCT
Designed specifically for imaging of extremities
Hand, wrist, elbow, knee, ankle, foot
Benefits
Weight bearing imaging for knee / foot / ankle
Comfort features - low dose
Improved visualization over 2D or standard 3D imaging
o Isotropic resolution
o Advanced Iterative image reconstruction
o Good soft tissue visualization
o Advanced Scatter and Metal Artifact Reduction
Large field of view – 21cm x 22cm
Compact design and reduced shielding requirements – Low cost
Fraction of MDCT cost
Imaging right at the point of care - faster diagnosis and treatment
Installation - Requirements
Small system and footprint
Standard ceiling height
Room shielding typically not
required*
*consult local regulations
Installation
Room pre-installation and post installation
OnSight Extremity CBCT
Designed to provide the lowest level of patient
and operator exposure
Patient exposure is reduced - compared to
traditional Multi-Detector CT
Only exposes joint under examination
Minimises scattered radiation - integrated lead
curtain and well shielded
OnSight Extremity CBCT – Bore volume
Large
field of view
Reconstruction volume
Bore opening
Applications
Motorised movements - auto-positions
for height, tilt and rotation
Stepstool and positioning guides
Patient monitor for imaging status
Patient support handles
Touch-screen monitor - intuitive user
interface
Specific patient chair
Applications
One stop orthopaedic clinics
DXR weight bearing studies
Demand for MDCT increasing
Ease of access
Applications
Potential to replace DXR and MDCT
More diagnostic confidence - Rreduction in repeat examinations
Occult and non-displaced fractures
Scaphoid fracture detection and healing evaluation
Non-unions and growth plate fractures in children, follow-up / fusion healing
Impingement (under load)
Evaluation of disease progression, for RA , OA and Gout
Post operative and follow up joint replacement
Design joint replacement
Initial Experience – Hand & Wrist
• 3D weight-bearing
• Accurate determination of the relative placement and
orientation of the bones while under realistic load
conditions
Investigational: Not Available for Commercial Sale
• Fracture Trapezium and
distal radius
Hand and Wrist
Initial Experience – Foot and Ankle
3D weight-bearing
Accurate determination of the relative placement and
orientation of the bones while under realistic load
conditions
Investigational: Not Available for Commercial Sale
Large Field of View Image the Tripod of the foot
Weight–Bearing 3D Exams - Ankle
Sc
Weight–Bearing 3D Exams - Ankle
Non weight-bearing Weight-bearing Non weight-bearing Weight-bearing
Investigational: Not Available for Commercial Sale
? Impingement MRI vs CBCT & DXR
Investigational: Not Available for Commercial Sale
Impingement
Investigational: Not Available for Commercial Sale
Ankle MRI vs. CBCT & DXR – Posterior impingement
Investigational: Not Available for Commercial Sale
Ankle – post surgery ? union
Investigational: Not Available for Commercial Sale
Trauma – Metal Artifact Reduction
Initial Experience – Knee
Investigational: Not Available for Commercial Sale
Knee - OA
Investigational: Not Available for Commercial Sale
Knee post KR fracture or loose component
Investigational: Not Available for Commercial Sale
3D surface rendering
Effective Dose
References:
Assessment of Effective Radiation Dose od An Extremity CBCT, MDCT and Conventional X-Ray for Knee
Using Mosfet Dosimeters – Juha Kivisto et al Department of Physics, University of Helsinki, Finland., 2013
Imaging of the knee
Modality Effective Dose
MDCT 27 - 48µSv.
CBCT 12.6µSv.
DXR (4 view) 6.0µSv.
Effective Dose
Modality Effective Dose
Chest MDCT ~7000 µSv (1,2)
Head MDCT ~2000 µSv (1)
Extremity MDCT ~30 to 160 µSv depending on anatomy and study details (4)
Chest radiograph ~20 to 100 µSv depending on study details (3)
OnSight CBCT Extremity scan ~5 to 40 µSv depending on anatomy and study details
2D Radiographic study of an extremity ~0.2 to 3 µSv depending on anatomy and study details (3)
1 day natural background exposure ~17 µSv (1)
1 trans-continental flight from NY to LA ~25 µSv (5)
References:
(1) www.epa.gov/radiation/radiation-sources-and-doses
(2) McCollough et.al. “Answers to common questions about the use and safety of
CT scans.” Mayo Clin Proc. (2015) 90(10):1380-92
(3) Huda W. et.al. “Radiation Dosimetry for Extremity Radiographs” Health Physics
(1998) 75(5):492-499
(4) Biswas et.al. “Radiation Exposure from Musculoskeletal Computerized
Tomographic Scans” J. Bone Joint Surg. Am. (2009) 91:1882-9
(5) http://jag.cami.jccbi.gov/cariprofile.asp
Conclusion
Initial experience positive
User friendly
Adoption rate typical
Higher resolution images than MDCT and DXR*
Lower dose than MDCT
Quicker than MDCT and DXR*
Good patient acceptance - Weight bearing
Metal Artefact Reduction – Works well
Competes with MDCT – Compliments DXR.
*Using Cone Beam CT as a low-does 3D imaging technique for extremities: initial experience in 50 subjects
Skeletal Radiology June 2015 Huang AJ, Chang CY Thomas BJ;
Future – Research Project
CBCT with MAR - Assessment of total knee replacement
Potential to deliver high image data with quantifiable
measurement of 3D position, fixation and bone density
Replacing 2D radiographs
Post surgery – assess position , exclude any bone damage
Early years – loosening, infection
End of life- loosening, bone loss, fractures in bone or metal
work
Results – better pre-op assessment, possible personalised
prediction of implant survival.