magnetic particle imaging
TRANSCRIPT
Magnetic Particle ImagingA Novel Fast 3D In Vivo Imaging Modality
based on Magnetic Nano Particle contrast agents
Dr. Nicoleta Baxan
Innovation with Integrity
Magnetic Particle Imaging (MPI)A New Imaging Modality at Bruker
• Bruker has introduced the first commercial MPI scanner
for Preclinical Research.
• MPI complements Bruker’s palette of other Preclinical
Imaging modalities.
MPIMRI MRI X-Ray OpticalµCTPET/SPECT
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Introduction to MPI
• New tracer-based 3D imaging modality
• Uses non-linear magnetization behaviour of clinically approved MRI contrast agents (Super Paramagnetic Iron Oxides, SPIOs)
• High Speed, High Sensitivity
• Quantitative
• Invented at Philips Research Laboratories, Hamburg [1]
• First demonstration of live mouse imaging in 2009 [2]
• Applications:• High speed: Bolus tracking, Angiography, Organ Perfusion
• High sensitivity: Stem cell tracking
• Quantitative: Organ Perfusion (Coronary deseases)
• Functionalized particles: cell targetting
[1] B. Gleich, J. Weizenecker, Nature 2005, 435, 1214-1217
[2] J. Weizenecker, B. Gleich, J. Rahmer, H. Dahnke, J. Borgert, Phys. Med. Biol. 2009, 54, L1-L10
12.02.2014 Magnetic Particle Imaging 3
4
Principles of MPI
• Particles exhibit a non-linear magnetization response to an applied magnetic field.
• The magnetization response to an oscillating excitation field contains harmonics of the excitation frequency.
• The harmonics can be detected in the presence of the excitation signal.
• Their intensity is proportional to the particle concentration.
• A bias field saturates the magnetization and suppresses the generation of harmonics.
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Spatial Selection (I)
5
• A gradient field (Selection Field, SF) saturates the particle magnetization everywhere except for a small region in the center (field free point, FFP)
• Only particles in the FFP vicinity respond to a field oscillation generated by an excitation field (Drive Field, DF)
• An image may be generated by mechanically moving the object through the FFP.
FFP
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Spatial Selection (II)
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• Insight: Drive Field actually moves
FFP.
• By three orthogonal DF coils, the
FFP can be moved magnetically
over the object.
• FFP passage causes local
magnetization flip.
• The response for a particle
distribution is the concentration-
weighted sum of the single-site
responses.
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Tracer Material
• Super-Paramagnetic Iron Oxide (SPIO)
nanoparticles
• Clinically approved, non-toxic MR contrast
agent
• Magnetite core (5-30 nm), biocompatible
coating (dextran, carboxydextran)
• Can be functionalized for targeting purposes
• Most experiments so far carried out with
ResoVist™ (Bayer-Schering)
• Large potential in tracer improvementsCore
Diameter
Hydrodynamic
Diameter
Core
Fe3
O4
Coating
(Dextran / Carboxydextran)
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Visions for MPIMedical Applications
Cardio-Vascular
• Cardiac ejection fraction, wall motion, flow dynamics
• Coronary blood supply
• Quantitative Myocardial perfusion
• Vulnerable plaque detection
Interventional Radiology (3D)
• Stent placement
• Device & disposal tracking (catheter, stents, …)
• Catheter navigation
Neuro-Vascular
• Bleeding detection
• Lung perfusion
• Functional brain imaging
Organ Perfusion Imaging
• Liver perfusion
• Lung perfusion (incl. therapy response assessment)
• Lung ventilation
Oncology
• Micro-vascularization (blood volume)
• Inflow-outflow kinetic (Pharmacokinetics)
• Interventional oncology
• Ablation monitoring
• Highly localized heating for therapy and thermally trigger local
drug release
Breast Imaging
• Sentinel lymph node detection
• Screening
Cell Tracking
• Bleeding detection
• White blood cell tracking – inflammation detection
• Therapeutic (stem) cell tracking
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Visions for MPIMolecular Imaging in Comparison to other Modalities
Radiation
used
Spatial
Resolution
Temporal
Resolution
Sensitivity Quantity of
Contrast Agent
used
Summary / Comments
Positron Emission
Tomography
high-energy
g - rays
1-2 mm
10 Seconds to
Minutes
10
-11
– 10
-12
mole/liter
Nanograms
Sensitive
Quantitative
Needs Cyclotron
Single Photon
Emission
Tomography
low-energy
g - rays 1-2 mm Minutes
10
-10
– 10
-11
mole/liter Nanograms Many available probes
Computed
Tomography
X-rays 50-200 µm Minutes
Not well
characterized
Not applicable
Good for bone, tumors, not for
soft tissue
Magnetic
Resonance
Imaging
radio waves 25-100 µm
Minutes to
Hours
10
-3
– 10
-5
mole/liter
Micrograms to
Nanograms
Highest resolution
morphological and functional
imaging, low sensitivity, slow
Magnetic Particle
Imaging
Radio waves 200-500 µm
Seconds to
minutes
10
-11
– 10
-12
mole/liter Nanograms
Quantitative
Good sensitivity,
fast good resolution
no tissue contrast
From: K. Krishnan, IEEE Transactions on Magnetics 2010, 48, 2523-2558
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• Imaging volume 20.4 ×12 ×16.8 mm3
• Frame rate ~ 46 fps
• Bolus can be following through body
• Signal is modulated by heart beat (partial volume effect)
J. Weizenecker, B. Gleich, J. Rahmer, H. Dahnke, J. Borgert, Phys. Med. Biol. 2009, 54, L1-L10
3D mouse imaging
10Magnetic Particle Imaging12.02.2014
MPI
Open research areas
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� Radiologists and non-technical researchers need more access to MPI scanners.
� German Research Foundation (DFG) is funding the installation of MPI scanners for
application oriented research.
New contrast
agents
MPI application
protocols
Diagnostic and
Interventional
imaging
Comparison to
other modalities
Reconstruction
techniques
Sequence
design
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Current state of MPIToday’s MPI Scanners world wide
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Installed base of working home-
built research scanners:
• Berkeley
• Braunschweig
• Hamburg
• Lübeck
• Würzburg
All current scanners are installed in laboratories focused on MPI hardware design and
are operated by physicists and engineers.
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Bruker Preclinical MPI SystemTarget specifications
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• AVANCE III / MPI technology
• ParaVision Software
• Full 3D imaging, segmented acquisition capability
• 12 cm free access
• BioSpec™/ClinScan™ compatible Animal Handling
• Integrated calibration robot
• Interfaces for Animal Monitoring and Infusion Pump
Component Target Specs
Scalable Selection Field 0…2.5 T/m
Drive Field X/Y/Z 0…20 mT @ 25 kHz
Focus Field X/Y/Z 0…45/0…45/0…120 mT
Max. FOV Ø 10 cm×10 cm
Bandwidth 1.25 MHz
Speed 46 volumes per second
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Magnetic Particle Imaging 14
Scanner Details (I)
Field Generator Design
Drive Field X/Y/Z
• 3 ×20 mT
• Oil cooled
• 12 cm bore
diameter
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Focus Field X/Y
• 2 ×45 mT
• Oil cooled
Focus Field Z
• 120 mT
• Water cooled
Housing
• 50×50×50 cm
Selection Field
• 2.5 T/m
• Water cooled
Magnetic Particle Imaging
Scanner Details (II)
Control electronics
• 5 cabinets
• Room for extensions and upgrades
Animal Handling
• 12 VDC filtered power for infusion
pump and monitoring equipment
• RS-232, Trigger, FO Monitoring
Operating Console
• Turnkey operation
• Complete control from ParaVision
Avance-III-MPI Electronics
• Components reused from
MRI/FTMS
Tune/Match boxes
• Contain capacitor banks
for resonant circuit
System Views
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ParaVision
• Imaging platform for MRI/MPI
• Open for user-implemented MPI
acquisition and reconstruction
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Bruker MPI Research
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• Magnetic Particle Spectrometer
• Also commercially available from Bruker
• System design and manufacturing
• Optimized reconstruction algorithms
• Combination MRI/MPI
• Ongoing design study
• Magnet switchable between homogeneous and gradient configuration
• MRI reference image generation in same instrument with minimal time difference to MPI scan
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Innovation with Integrity
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