Download Functional computed tomography using energy resolved photon

Functional computed tomography
using 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 Imaging
American 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
Anatomical imaging is now really good
Very little benefit in more speed or resolution
Anatomical imaging is now really good
Functional imaging is the future
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
MARS spectral CT project
Goals

To obtain novel information about tissues
Compositional information
Functional information

To have a route to human imaging
The Team
Technical team
University of Canterbury
Clinical team
University of Otago
International Partners
Incl. CERN, Mayo Clinic, etc
The company
MARS Bioimaging Ltd
History
Ernest Rutherford
Early work at University of Canterbury
Bates and Peters
1971 First use of Fourier transform in CT
1972 First CT of biological tissue
CT of sheep bone, 1972
Single
energy CT
Single- , dual-, and spectral CT
Xray source
B/W
Patient
Grey scale
detector
Hounsfield Units
Single
energy CT
Single- , dual-, and spectral CT
Xray source
B/W
Dual energy
CT
Patient
Grey scale
detector
Xray source
B/W
Xray source
B/W
Two grey
scale detectors
Hounsfield Units
Single
energy CT
Single- , dual-, and spectral CT
Xray source
B/W
MARS
spectral CT
Dual energy
CT
Patient
Grey scale
detector
Xray source
B/W
Xray source
B/W
Two grey
scale detectors
Xray source
Medipix
Color
detectors
Hounsfield Units
Spectral CT is now possible
Medipix All Resolution System
Energy 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
Medipix 2/3 Collaborations
Transferring high energy physics technology into medicine
NZ provides

Test-bed for technology

Application development

First (pre-) clinical experiments
Software control

GUI with full control

Scriptable with Python
Image recovery and viewer



Pre-processing (clean data)

Flatfield, stitch, denoise, ring-filter

Export sinograms or projection data
Reconstruction (2d images to 3d volume)

Filtered back projection (Octopus from Ghent)

In house Algebraic Reconstruction
Visualisation (explore the data)

In house 3D spectral viewer with linear transforms

including real-time iterative PCA
Image recovery and viewer
Measure individual materials
Iodine: Pulmonary circulation
Barium: Lung
Calcium: normal bone
Traditional “broad spectrum” CT
Pharmaceuticals identified by
spectral information
Iodine: Pulmonary circulation
Barium: Lung
Calcium: normal bone
Multiple pharmaceuticals
Clinical applications:

CT

Spectral-CT

Non-contrast scan

Contrast1 outside room

Contrast scan

Contrast2 on scanner

Delayed scan

Scan

3 scans

1 scan

Twice on table

Once on table
Functional cartilage imaging
Histology and spectral CT to demonstrate GAG content
•
Low GAG
•
High hexabrix
Cartilage
Bone
- Volume rendering
- Energy gradient by PCA
•
High GAG
•
Low hexabrix
Funded by NZ Arthritis Foundation
Quantification of fat and water
Spectral CT of a mouse
10-35keV
“Fat-like”
“Calcium-like”
Initial work funded by Health Research Council
“Water-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
•Complex physiological markers can be made
•These often have unique spectral response
(contain heavy atoms)
We can measure the spectral response of
nano-particle that target aggregated
platelets.
Today we are measuring them in human
tissue…
Conclusion

Functional imaging is the future of radiology

Spectral CT is able provide this information

Christchurch is one of the world leaders
This is:
Technology transfer from physics to medicine