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Functional computed tomographyusing energy resolved
photon counting detectors
Anthony Butler
Overview Why functional imaging
Recent trends in clinical imaging
Spectral CT and the MARS project
Medical applications Radiopharmaceutical imaging Soft tissue imaging
Conclusions
Change in radiology utilisation
1998-2005 => 4.5% /year
2006-2008 => 1.4% /year
Bending the Curve: The Recent Marked Slowdown in Growth of Noninvasive Diagnostic ImagingAmerican Journal of Roentgenology, Jan. 2011
Drivers of change
2000-2008 “CT Slice War” fan beam geometry to cone beam geometry
2000: acquire a single transverse slice per rotation 2012: acquire up to 64-500 slices per rotation
Current State
Very little benefit in more speed or resolution
Anatomical imaging is now really good
What is the tissue?
What is its behaviour?
Is the treatment working?
(not just size, shape, location)
What the diagnostician wants to know Constituents (fat, water, calcium, iron)
Cancer and pathogen labels
Physiological markers
etc
Functional imaging is the future
Anatomical imaging is now really good
MARS spectral CT project
Goals
To obtain novel information about tissues
Compositional information Functional information
To have a route to human imaging
The TeamTechnical team
University of Canterbury
Clinical teamUniversity of Otago
International PartnersIncl. CERN, Mayo Clinic, etc
The companyMARS Bioimaging Ltd
Sing
le
ener
gy C
T
Xray source B/W
Hounsfield Units
PatientGrey scaledetector
Single- , dual-, and spectral CT
Xray source
Sing
le
ener
gy C
TD
ual e
nerg
yCT
Xray source
Xray source B/W
B/W
B/W
Hounsfield Units
PatientGrey scaledetector
Two greyscale detectors
Single- , dual-, and spectral CT
Xray source
Xray source
Sing
le
ener
gy C
TD
ual e
nerg
yCT
MAR
S sp
ectr
al C
T
Xray source
Xray source B/W
B/W
B/W
Medipix
Hounsfield Units
PatientGrey scaledetector
Two greyscale detectors
Colordetectors
Single- , dual-, and spectral CT
Spectral CT is now possible
Medipix All Resolution SystemEnergy resolution
Spatial resolution
Temporal resolution
Current single-energy CT provides
Spatial resolution
Temporal resolution
Brightness only (grey scale)
X-ray camera
Medipix3 photon processing detector Quantum / counting detector(Film, CR, DR, CT are all integrating detectors)
Pixel detector Each pixel has its
own electronics
Spectral detector Measure energy of photons
0
0.05
0.1
0.15
Ca
FeIodine
Sunflower oil
AirWater
Reconstruction tailored to photon counting
Photon counting detectors poor in high flux
Medip
ix
x-raysource
0
0.05
0.1
0.15
Ca
FeIodine
Sunflower oil
AirWater
Reconstruction tailored to photon counting
Photon counting detectors poor in high flux
Medip
ix
High x-ray flux beam
x-raysource
High x-ray flux beam
Reconstruction tailored to photon counting
Reconstruct only from central detector elements
0
0.05
0.1
0.15
Ca
FeIodine
Sunflower oil
AirWater
Medip
ix
x-raysource
ROI
Highx-ray flux
Measure individual materials
Iodine: Pulmonary circulation
Barium: Lung
Calcium: normal bone
Pharmaceuticals identified by spectral information
Iodine: Pulmonary circulation
Barium: Lung
Calcium: normal bone
Histology and spectral CT to demonstrate GAG contentHistology and spectral CT to demonstrate GAG content
Cartilage
Bone
Functional cartilage imaging
- Volume rendering- Energy gradient by PCA
• Low GAG Low GAG
• High hexabrixHigh hexabrix
• High GAG High GAG
• Low hexabrixLow hexabrix
Funded by NZ Arthritis Foundation
Quantification of fat and water
Spectral CT of a mouse
10-35keV
Initial work funded by Health Research Council
“Water-like”“Calcium-like”“Fat-like”
Atheroma characterization
Aim to indentify plaque
components
Unstable plaques need
therapy
Next Steps:
Ca versus Fe
Inflammatory markers
Funded by National Heart Foundation
The future: Functional labels
We can measure the spectral response of nano-particle that target aggregated platelets.
•Complex physiological markers can be made
•These often have unique spectral response(contain heavy atoms)
Next step: Measure them in mice…
Conclusion
Recently radiology improvements have been speed and spatial resolution
Functional imaging is the future of radiology
Spectral CT is able provide this information
Anthony Butler, M Walsh, P Ronaldson, N Scott, R Zainon, S Geiseg, T Janmale, N Cook, A Opie, R Amir, R Doesburg, N de Ruiter,H Yu, J Bennett, G Wang, T Woodfield, N Cook, P Bones, J Mohr, N Anderson, P Butler
