Institut Fresnel Aix Marseille Université CNRS Centrale Marseille OUTLINE MRI BASICS B 1 inhomogeneity at Ultra High Field MCube objectives Shaping B 1 with metamaterial ID: 1012359
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1. MetaMaterials for ultra-high field MRI. M-Cube project: objectives and some results Institut FresnelAix Marseille Université, CNRS, Centrale Marseille
2. OUTLINE MRI BASICS B1+ inhomogeneity at Ultra High FieldM-Cube objectivesShaping B1+ with metamaterial
3. 1H 3He 13C, 23Na 31Poriented with static field randomly oriented B0oriented with angle B0B1ZYXZYXB0Relaxation Time T2ZYXB0Relaxation Time T1MRI BASIS
4. MAGNETIC RESONANCE IMAGING Principles, Methods, and Techniques - Perry Sprawls http://www.sprawls.org/mripmt/index.htmlA transmit-receive radiofrequency system at the Larmor frequency fL = g.B0MRI BASIS
5. https://static.healthcare.siemens.com/siemens_hwem-hwem_ssxa_websites-context-root/wcm/idc/groups/public/@global/@imaging/@mri/documents/download/mda3/mzk0/~edisp/magnetom-flash_whole-body-mri-at-1-5t-step-by-step_mcguire-04414926.pdfWHOLE BODY MRI AT 1.5T
6. Increasing the static magnetic field improves SNRhigher resolutions and/or shorter scan times,X-Nuclei Imaging (lower abundance than proton),Spectroscopy,Functionnal MRI …Drawbacks : inhomogeneity, SARUltra High Field MRI
7. Brain Imaging at 7T :Dark areaContrast lossCourtesy to Alexandre Vignaud Inhomogeneity at Ultra High Field
8. Inhomogeneity at Ultra High FieldB0 = 0.3 Tesla fL ~ 12.8 MHz for 1H λ ~ 265 cm B0 = 0.5 Tesla fL ~ 21.3 MHz for 1H λ ~ 160 cm B0 = 1 Tesla fL ~ 42.6 MHz for 1H λ ~ 80 cm B0 = 1.5 Tesla fL ~ 63.9 MHz for 1H λ ~ 53 cm B0 = 3Tesla fL ~ 127.2 MHz for 1H λ ~ 26 cm B0 = 7 Tesla fL ~ 300 MHz for 1H λ ~ 11 cm
9. Webb A. Concepts in Magnetic Resonance Part A, 2011; 38A:148-184The higher the static field the higher the Larmor frequency : field inhomogeneities appears.Need for local RF field control in MRI volume coil In addition, SAR increases with the square of the magnetic field strength & local SAR (hot spots)
10. M-Cube objectivesOur main objective is to go beyond the limits of MRI clinical imaging and radically improve spatial and temporal resolutions.M-Cube consortium will develop a disruptive metamaterial antenna technology. This we will able us to tackle both the lack of homogeneity and SAR barriers. This technological breakthrough will be validated by preclinical and clinical tests with healthy volunteers.Physicists, medical doctors and industrial actors will work closely all along the implementation of the project to guarantee the success this novel approach, a “patient-centered” solution which will pave the way for a more accurate diagnosis in the context of personalized medicine and will enable to detect a disease much earlier that is currently possible.
11. M-Cube objectives
12. M-Cube partnersMetamaterials groupsAix-Marseille Université / Institut FresnelCNRS / Institut LangevinUCL / ICTEAMAalto University / Theoretical and Applied Electromagnetics of Complex MediaITMO University / META LABANU / Nonlinear Physics CenterMRI centers Aix-Marseille Université / CRMBM (Siemens)CEA / Neurospin (Siemens)UMC Utrecht / Center for Images Sciences (Philips)CompaniesMRCoilsMutliwave Technologies
13. B1+ inhomogeneity at Ultra High FieldNOVA
14. Inhomogeneity at UHF depend on the coils ? Simulation of the B1+ of empty bird cage CST model of 7 Tesla bid cage B1+ inhomogeneity at Ultra High Field
15. B1+ inhomogeneity at Ultra High Field
16. rf shimming strategiesActive shimmingActive shimming requires multiple emitting elements driven independently.Optimization procedures are able to reduce the inhomogeneities.Very expensive, compliance to safety guidelines challenging. Transmit arrayCourtesy of ELH institute for MRI, Essen GER Passive shimmingInsertion of high permittivity pads between coil and subjectAble to enhance RF amplitude locally thanks to displacement current in the padWater suspensions performances drop with time.Several dielectric materials present toxicity risksPadsWebb A. CMR, 2011; 38A:148-184
17. Kerker effectKerker, M et al, J. Opt. Soc. Am. 73, 765–767 (1983) : “When ε = µ, the back-scatter gain is zero” Interactions between electric and magnetic dipolar modes of a dielectric sphere allows similar effects.Geffrin, J. M. et al Nature communications, 3, 1171. (2012)However, dielectric spheres are not very well suited for MRI applications in RF range. M. Dubois et al. « Kerker effect in Ultra High Field Magnetic Resonnance Imaging » to be published in PRX
18. hybridized meta atom1 - Abdeddaim et al, Patent no. 16 52700, 2 - Jouvaud, C., Abdeddaim, R., Larrat, B., & De Rosny, J.Applied Physics Letters, 108(2), 023503 (2016)Hybridization scheme of coupled half-wavelength resonators dL
19. Kerker effect with HMAScattering Cross Section as a function of the length of the HMA for an incident plane wave at the Larmor frequency at 7 Tesla (297.2 MHz). The upper left inset shows a sketch of HMA and the electric (E), magnetic (H) fields and wave-vector (k) orientations. kHE2 cmr= 0.5mm42 cm47.7 cm46.7 cm
20. hybridized meta atomFarfield Kerker scattering conditions
21. hybridized meta atomNear field Kerker effect Feed dipoleHMA↑ ↑ Birdcage legHMA
22. hybridized meta atomNear field Kerker effect in 7T MRI 16 cm diameter Oil phantomHMA1Tx/1Rx Invivo CorpXFL B1+ mapping TR 20sTE 3msFA 7°4mm isoSpecial regards to Z. Raolison, L. Leroi and A. Vignaud (CEA, Saclay)
23. hybridized meta atomNear field Kerker effect EXPERIMENTS Normalized B1+ AmplitudeTHEORY
24. hybridized meta atomNear field Kerker effect Flip angle in degreesWire length in cm
25. With 1 MA, 2cm away from phantom: With 1 BaTiO3 pad : Reference : TeslaAPRLAPAPRLAPMetamaterial and MRI coils
26. SNR enhancement map in percentage : strong SNR enhancement close to the HMA but also a slight improvement on a relatively large part of the phantom volume.
27. Next steps :An antenna is developped by Multiwave Innovation and will be tested soon on human volunteers1.Many other example of usefulness of metamaterials for MRI imaging on mcube-project.eu (UHF MRI)1Method for controlling the distribution of the rf magnetic field in a magnetic resonance imaging system, WO2017198914A1
28. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 736937CEA SACLAY NeurospinLisa LeroiZo RaolisonBenoit LarratAlexandre VignaudCyril PouponAlexis AmadonDenis LeBihan Institut FresnelMarc DuboisRedha AbdeddaimGérard TayebPierre SabourouxNicolas BonodStefan EnochMultiwave InnovationElodie GeogetTryfon AntonakakisSiemens HealthineersFranck Mauconduit