Instrumental basis for an MRI/MRS center dedicated to animal studies

1. Colóquio IFSC -Março/2011 Instrumental basis for an MRI/MRS center dedicated to animal studies A. Tannús – 03/2011 IFSC - USP

2. Basic Principles; Some methodologies for fast imaging; NMR probes; Digital NMR spectrometer Major items of this talk: Basics

3. Basic Principles; Some methodologies for fast imaging; NMR probes; Digital NMR spectrometer Major items of this talk:

4. Diversity of anatomies – no single probe for all studies; Studies at the limit of sensitivity; Large number of nuclei of interest; Methodologies requiring dedicated hardware (e. g. split transmit coil ASL – avoid MT); Flexibility of studies – would you touch a US$35k probe to configure it for a new experiment? Better build your own!! Probes: why focus on them?

5. Transmit/receive x split coils: • Compromise between uniformity and sensitivity: • We can’t get everything with a single coil! • Uniform (transmit) coils require more power, consequently are less sensitive (uniform flip angle); • Efficient anatomic coils show poor RF field homogeneity – must be used as receive-only – since they present good sensitivity.

6. 5 6 4 7 3 8 2 1 6  2 1 3 7  5  Potential 5 6 4 4 8  7  3 8 4 8 2 1 3 5 1 7 2 6 The problem in Electromagnetism to be solved: surface current in a cylinder. Possible resonant structure

7. Transmit RF coils Tune & match rods RF reference potential RF coil

8. Our best approach: Double Crossed Saddle Tune & match circuit “Double crosses” (outperforms) the equivalent Birdcage structure

9. Other structures developed and tested: 8-leg transmit birdcage 16-leg transmit birdcage

10. Latest developed probe:Receiving coils for rodents – surface coils C CM C C CT RFout Tune & match circuit on reception

11. Rodents brain surface coils*: Anesthetics mask Motion restriction * Tested also as transmit/receive

12. Results: Double Crossed Saddle Actually a 20/30 system for now

13. Results: Rodents surface coil Actually a 20/30 system for now

14. A B C Is Manganese contrast possible at 2 T? Coronal images of: control (A, animal 7), 36 h after 60 mg/kg of manganese chloride (B, animal 4,) and after 30 minutes in SE (C, animal 8) – 3D Flash enhances the hippocampus. Answer: YES

15. YES, of course!! And more! 3 consecutive slices of a control animal showing hippocampus anatomy Same 3 slices of an animal with 9 months of epileptic life: Notice the size of the ventricles, due to a downsizing hippocampus and other structures not yet associated to the SE. Open field of investigation.

16. Featuring: active transmit decoupling allows use of any sort of Adiabatic Pulses Passive TF Signal RF pulse Active “Cross-over” effect TF Signal RF pulse

17. To come soon: phased array reception coils Preamp Low Z Preamp Low Z Preamp Low Z Preamp Low Z To the 4 BRUKER RECEIVERS

18. Basic Principles; Some methodologies for fast imaging; NMR probes; Digital NMR spectrometer Major items of this talk:

19. “Old fashioned electronics” systems could be home made up to the early 90’s: Limiting factor: Bus speed. Old fashioned experimental researchers (and newcoming) moved to software development; Electronic devices became highly specific: You can’t build what you want, only what the functionality of the devices would allow you!! Digital MR Spectrometer

20. Commercial systems are expensive and sometimes poor in flexibility; Our “Dream System” should be something like waking up with a new problem, implementing it at morning, perform the experiments in the afternoon and having the paper ready at night! Our experience with existing systems was a series of frustrations. Digital MR Spectrometer: Driving forces

21. Reached speed, density and programmability friendship to allow “mere mortals” to use them. Modern FPGAs (Statix IV family, Altera and Virtex 6, Xilinx) can accommodate few 4-core Intel CPU (code for that is somewhere over the internet). Development kits come on all flavors, just choose the one that fits your problem (from US$40 to US$9k)! Good news from Field Programmable Array Logics devices (FPGAs):

22. Using ALTERA’s embedded NIOS DSPs (Intellectual Property of ALTERA, we have a working University Agreement); Using our own proprietary MR State Machine instantiated and adapted for all needed spectrometer subsystem modules Our proposal: develop a Digital MRI/MRS Spectrometer in two independent approaches:

23. To all modules Sequencer D/A D/A D/A D/A Loader To all modules . . . RF Synthesis Time Base MR State Machine approach High Speed BUS (10 GB) Receiver demodulation 1 or more receivers RF (NMR) P C FIFO A/D PreCompensation (preemphasys) X Generation of Logical Gradients Conversion to physical Gradientes P C Y BUS Z B0 Modulation AM FM Phase RF D/A Different instances of the same concept of our State Machine 1 or more Modulators To all receivers and modulators FPGA

24. Development workstation

25. Stratix III development kit

26. System peripherals Low speed external bus for Gradients High speed external bus/ external SDRAM Fast A/D and D/A converters (85/125 MHz, 2 Transmit/ receivers for now) Gradients DACs (1us/point, 4 units)

30. Old fashioned experimentalists are now free again!! Please join us on learning, using, teaching your students and convincing others that this new concept of doing electronics is excitingly feasible! Students: Daniel Papoti (DOU) Jackeline Malheiros (DOU) Felipe Coelho (IC) ChristoferBertonha (IC) Tiago Martins (IC) Cintia Silva (DTI) Our team: Edson Vidoto Mateus Martins Alberto Tannús Rafael Martins (ITI) Jorge Sampaio (DTI) Mario Gazziro (DTI) Diogo Queiroz (MES) Cristina Torres (MES) Gustavo Frigieri (PD)

31. Thank you!