Advanced SPION enhanced MRI in experimental research

Lindsey Crowe, PhD

Hopitaux Universitaires de Genève, Switzerland

Current Challenges Facing Inorganic Nanoparticles in Medicine and Industry

Conference + Working Session 27–28 September 2013

Inselspital, Bern

Summary

• MRI • Nanoparticles for MRI • SPION MRI Techniques:

– Signal loss – Positive contrast – Dual contrast agent

• Applications including: – Cardiac – Labelled cell transplantation – Cell tracking

• Conclusions

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MRI

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MRI

• MRI non-invasive - serial observation

• 3D Isotropic High Resolution

• Flexible contrast

• More than just anatomy – Function

– Flow and perfusion

– Metabolism

– Dynamics

– Cells

Experimental MRI Pre-clinical animal studies on a clinical type MRI – ‘Translational Research’ validated clinical sequences available for comparison any newly developed methods are directly transferable to the clinic

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MRI non-invasive monitoring for longitudinal study

Magnetic Resonance • Certain atomic nuclei including 1H exhibit nuclear

magnetic resonance.

• Nuclear “spins” are like magnetic dipoles.

1H

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Polarization

• Spins are normally oriented randomly.

• In an applied magnetic field, the spins align with the applied field in their equilibrium state.

• Excess along B0 results in net magnetization.

No Applied Field Applied Field

B0 7

The Whole Process

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T1 and T2 • Recovery of T1 during TR 'repetition time' determines the signal available

for the next echo. If partial, less signal.

• T2 will determine the signal available for acquisition at the echo time TE.

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TR = time between taking each set of datapoints. TE = time after the pulse at which the data is recorded. Interplay affects image contrast

Contrast agents for MRI

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Contrast Agents • Contrast agents are chemical substances introduced to the

anatomical or functional region being imaged to increase the differences between different tissues or between normal and abnormal tissue, by altering the relaxation times.

• MRI contrast agents are classified by the different changes in relaxation times after their injection.

Magnetic properties

Weakly repel: water and tissue

Weakly attract: Gd T1 and T2 Reducing agents

Interact strongly: Fe susceptibility agents (T2*)

SPIONs are much more effective in MR relaxation than paramagnetic agents

Diamagnetic Paramagnetic Superparamagnetic

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T1 and T2 with contrast agents • Improve or modify the signal in specific regions of tissue

• Gd will shorten T1 to improve the signal with better recovery before the next RF pulse

• Iron shortens T2 by giving local field inhomogeneity signal loss due to the rapid decay of the signal before the signal acquisition TE

TR

TE

T1

T2

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Nanoparticle design for MRI

• Common iron oxides forms used in nanoparticle preparations are magnetite (Fe3O4) and maghemite (γFe2O3)

• Insoluble in water • Superparamagnetic - only exhibit magnetic properties when in a magnetic field • T2-weighted imaging opportunities Several advantages over common T1 / gadolinium based contrast agents • Lower toxicity. • Improved diagnosis in a variety of pathologies and biological activities such as

inflammation, infarction and tissue repair. • Tailored therapeutic functions, in particular with tumour treatment. • Attach antibodies, drugs, enzymes and proteins. • Can be directed to specific organs or tissues and can also be guided with

magnetic fields to target tumours and induce hyperthermic effects.

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Nanoparticle design for MRI

• Suitable iron core and monolayer

• Uniform particle size

• Uniform and high superparamagnetic moment

• High colloidal stability

• Low toxicity and high biocompatibility •Known pathway for breakdown and excretion from the human body •Degradation causes iron to enter plasma, where it is processed by the body •Risk of iron overload is minimal

• Production method has an influence on all of the above properties

• Determines the overall effectiveness of the contrast agent

J Lodhia et al. Biomed Imaging Interv J 2010; 6(2):e12 G Mandarano et al. Biomed Imaging Interv J 2010; 6(2):e13

Molecular imaging definition

• Molecular imaging can be broadly defined as the ‘non-invasive and repetitive imaging of targeted macromolecules and biological processes in living organisms.’

• Cellular imaging, on the other hand, can be defined similarly as the ‘non-invasive and repetitive imaging of targeted cells and cellular processes in living organisms.’

Bulte JW, Kraitchman DL. NMR Biomed. Nov 2004;17(7):484-499 16

SPION MRI Techniques - T2 signal loss

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Conventional MR of SPION

• Short T2* species appear dark on conventional images where the minimum TE is of the order of milliseconds.

• Conventional imaging sequences

– Tissues with T2 shorter than TE give hypointense signal

• Other hypointense species

• Non uniform background

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SPION MR Imaging

Normal liver Liver with islets and iron Conventional MRI

High sensitivity, easy detection

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Cardiac

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Macrophages imaging using iron oxide

• Non specific uptake (depends on the size and charge)

• Large field of application:

– Cardiac

– Plaque imaging

– Kidney transplant rejection

– Arthritis.....

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Macrophage tracking in myocardial Infarction

Montet-Abou, K, et al. Eur. Heart J. 2010;31(11):1410-1420

• In vivo pre-loading of monocytes by USPIO

• injection 2 days before any injury

• Occlusion reperfusion to induced a myocardial infarct

• Serial MRI to follow the arrival of iron loaded monocytes

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Monocyte Tracking in Myocardial Infarction

Montet-Abou, K, et al. Eur. Heart J. 2010;31(11):1410-1420 23

Also Fluoresence

Montet-Abou, K, et al. Eur. Heart J. 2010;31(11):1410-1420

Monocyte Tracking in Myocardial Infarction

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Histological validation CD68 only with MI Prussian Blue only with SPION MRI only with SPION + MI

Appearance on Images

Am J. Transplant 2011;11(6):1158-68. A novel method for quantitative monitoring of transplanted islets of Langerhans by positive contrast magnetic resonance imaging. LA Crowe, F Ris, S Nielles-Vallespin, P Speier, S Masson, M Armanet, P Morel, C Toso, D Bosco, T Berney, J-P Vallée Circulation. 2001 Jan 23;103(3):415-22. Magnetic resonance imaging of atherosclerotic plaque with ultrasmall superparamagnetic particles of iron oxide in hyperlipidemic rabbits. Ruehm SG, Corot C, Vogt P, Kolb S, Debatin JF.

Signal loss from iron labelled structures Problems with ambiguity and artifacts Difficult if adjacent structure is also black Signal void is larger than physical size of label Quantification of black?

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Cell tracking with SPION

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Stem cells tracking using SPIO

• In vitro loading (incubation, magnetoporation, transfection agents)

• Injection (in the ‘injury’ or iv at distance)

• Serial T2* imaging

• Demonstrated in numerous applications

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MSC tracking in the brain after iv inj

Photochemical lesion in the rat cortex Iv injection of endorem loaded MSC

Sykova, E, Jendelova, P. Prog. Brain Res. 2007;161:367-383 28

Iron loaded MSC in the heart

24h 1 week

Kraitchman, Circulation. 2003;107:2290-2293 29

Stem Cells on patch - rat heart

MRI over time of fibrin cardiopatches containing either superparamagnetic iron oxide (SPIO) nanoparticles alone or SPIO-loaded mouse ESCs, after grafting onto the left ventricles. Scale bars 1 cm. indicates center of the infarcted area; arrowheads show the limits of the patch extension.

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Vallée et al. STEM CELLS TRANSLATIONAL MEDICINE 2012;1:248–260

Stem Cells on patch - rat heart

7-10 slices FFE cine sequence (acquired pixel size= 0.4 x 0.4 mm2, slice thickness= 2mm, over 2 RR intervals) A C-SPAMM TAG preparation segmented cine FFE sequence (interTAG spacing= 1.25 mm, acquired pixel size= 0.6 x 1.8 mm2, slice thickness= 3mm, over 3 RR intervals) Patch seen on cine… Function not affected - tag

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Limitations of conventional SPIO MRI

• Disadvantages of Negative contrast:

- depends critically on image resolution

- partial volume effects obscure signal void

- other signal voids

(motion artifacts, calcifications, other susceptibilty)

- void volume challenging to quantify

• Alternative techniques/strategies are needed !!!

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SPION MRI Techniques - Positive contrast

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Stuber M et al, Magn Reson Med 2007;58:1072–1077

I.R.O.N. Quantifiable or positive iron contrast methods often lose anatomical reality…for example

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presence of superparamagnetic/ferrom

agnetic particles introduces magnetic field

inhomogeneities

3*106 cells

1*106 cells 0.5*106 cells

Offresonance Imaging

on-resonance projection Off-resonance projection (-800 Hz @ 1.5T) signal correlates with the number of cells

Reference: gradient-echo

Cunningham CH et al, Magn Reson Med 2005;53: 999–1005

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presence of superparamagnetic

/ferromagnetic particles

introduces off resonance frequencies

Labelled Cell Transplantation

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Goals Rejection in islet transplantation can not be monitored directly Insulin requirements and blood glucose changes are observed too late after rejection has already occurred MRI and labeling pre-transplant with SPION is relatively simple, long lasting and does not affect cells viability or function. Develop a reliable and automatic quantification of small changes – how to exploit ‘positive contrast‘ signal from SPION

Apply these protocols to pre-clinical trials in rat and transplant patients

•Shapiro AM, Ricordi C, Hering BJ et al. N Engl J Med 2006; 355: 1318–1330. •Ris F, Lepetit-Coiffe M, Meda P, et al. Cell Transplant 2010; 19:1573–1585. •Toso C, Vallee JP, Morel P, Ris F, et al. Am J Transplant 2008; 8: 701–706. •Borot S, Crowe LA, Toso C, Vallée JP, Berney T. Curr Diab Rep. 2011; 11(5):375-83.

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Dual Echo and Difference (dUTE) • A UTE image will include all of the species, including very short T2*.

• A second echo image subtracted (only short T2* decayed) = positive contrast from the short T2* species and nulled uniform background signal (d-UTE).

•Gatehouse PD, Bydder GM. Clin Radiol 2003;58(1):1-19.

•Robson MD, Gatehouse PD, Bydder M, Bydder GM. J Comput Assist Tomogr 2003;27(6):825-846.

•Crowe LA, Wang YX, Gatehouse PD, et al. Proc Intl Soc Mag Reson Med 2005:115.

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dUTE : Quantification explained

Positive, quantifiable islet cells on a suppressed background and anatomical information in the individual echoes

L. A. Crowe, F. Ris et. al. American Journal of Transplantation 2011; 11: 1158–1168 40

Longitudinal Study

Persistent signal same 5 islet clusters seen over 100 days Easy registration and recognition from ‘any plane reconstruction’ of 3D images and anatomical landmarks

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Molecular Imaging with SPION

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Molecular imaging using SPION

43 Ajay Kumar Gupta, Mona Gupta Biomaterials 26 (2005) 3995–4021

Uncoated Magnetic Nanoparticle

Functionalised Magnetic Particle

Target cells have receptors expressed on their surface for targeting

Nanoparticles bind to the receptors on the cell surface

Clinical Cell Tracking with SPION

• Personalized diagnosis and treatment with allogenic or autologous cells

• Promising findings in preclinical studies, the clinical results to date have been limited

• How to monitor the migration, homing, survival, and function of the transplanted cells in vivo

• Solution: SPION MRI

• Most MRI cell tracking studies are currently still limited to in vivo visualization of the labeled cells

Essential Elements to Consider for MRI Cell Tracking Studies with Iron Oxide-based Labeling

Agents. Paul C. Wang, Liang Shan. Journal of Basic & Clinical Medicine 2012, 1(1):1-6

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Clinical Cell Tracking with SPION • Recommendations:

Essential Elements to Consider for MRI Cell Tracking Studies with Iron Oxide-based Labeling

Agents. Paul C. Wang, Liang Shan. Journal of Basic & Clinical Medicine 2012, 1(1):1-6

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Magnetite nanoparticles for medical MR imaging - Review article 08 July 2011

Zachary R. Stephen, Forrest M. Kievit, and Miqin Zhang Materials Today (2011) 14(7-8), 330-338

• Nanotechnology has given us new tools for the development of advanced materials for the detection, diagnosis and treatment of disease.

• Superparamagnetic iron oxide nanoparticles have been extensively investigated as a novel MRI contrast agent due to a combination of favorable superparamagnetic properties, biodegradability, and surface properties.

• An extensive range of animal models, treatments and diseases can be studied to optimise imaging properties, drug delivery and cellular interactions.

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Acknowledgements

• Jean-Paul Vallée, Azza Gramoun,

• Iris Friedli, Kerstin Grosdemange

• UNIGE

• HUG

• NanoDiaRA – Development of Novel Nanotechnology Based Diagnostic Systems for Rheumatoid

Arthritis and Osteoarthritis (NanoDiaRA). The European Commission is funding the collaborative project through the 7th Framework Programme for Research (NMP4-LA-2009-228929 "Nanosciences, Nanotechnologies, Materials and new Production Technologies").

• CIBM – This work was supported in part by the Centre for Biomedical Imaging (CIBM) of

the Geneva and Lausanne, as well as the Leenaards, Louis-Jeantet and Insuleman foundations.