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Project 2: Part 1 Technology Development for MR Assessment of Small Animal Physiology Brian Rutt, PhD

Project 2: Part 1 Technology Development for MR Assessment of Small Animal Physiology Brian Rutt, PhD. MR Gradient Coil Insert Design and Construction Andrew Alejski, PhD Carl Gazdzinski, BSc Yuteng Chen, MSc. 300 mT/m 3-layer rabbit coil (“Rcoil”). Micro-Imaging. 7T, 3D Spin Echo

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Project 2: Part 1 Technology Development for MR Assessment of Small Animal Physiology Brian Rutt, PhD

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  1. Project 2: Part 1 Technology Development for MR Assessment of Small Animal PhysiologyBrian Rutt, PhD

  2. MR Gradient Coil Insert Design and ConstructionAndrew Alejski, PhDCarl Gazdzinski, BSc Yuteng Chen, MSc

  3. 300 mT/m 3-layer rabbit coil (“Rcoil”)

  4. Micro-Imaging 7T, 3D Spin Echo 100 micron isotropic 7 hour scan 1.5T, 3D FIESTA 100 micron in-plane 200 micron slices 30 minute scan

  5. Next Generation Insert Coil (“Scoil”) • 18 cm inner diameter • Designed specifically for ultra-high-performance mouse, rat, rabbit imaging using GE Signa Lx and EXCITE at 1.5T and 3T • Gmax: 500 mT/m, SlewRate: 2400 T/m/s • Completed manufacturing of three identical Scoil prototypes: • 1) GE-ASLW / Stanford Research Institute • 2) GE-GRC / Albany Medical Center • 3) Robarts

  6. Installation and Early Results from GE-ASLW / SRIYuteng Chen, MScElfar Adalsteinsson, PhDDolf Pfefferbaum, MD

  7. Sunday Feb. 22 2004 Cable cutting & crimping

  8. Monday Feb. 23 2004 Twin switch installation

  9. Monday Feb. 23 2004 Twin filter installation

  10. Tuesday Feb. 24 2004: Magnet room custom cable installation

  11. Wednesday Feb. 25 2004 Insert coil calibration

  12. Completed / Installed Scoil (3T @ GE-ASLW) Clinical Insert Peak gradient 40 mT/m 500 mT/m Slew rate 150 T/m/s 2000 T/m/s Resolution 0.8mm 50-100 microns

  13. Thursday Feb. 26 2004: First imaging by Dr. Pfefferbaum

  14. Thiamine-deficiency induced lesion in rat thalamus

  15. Thermal Engineering of Gradient Insert CoilsYuteng Chen, MSc

  16. Model Actual Fig.3 - The electro-thermal circuit

  17. Temperature sensor: Thermocouples were attached to the hotspot at each wire pattern. 40mm Cooling tube Thermocouple 2~2.5mm 1.0mm Wire pattern Zigzap cooling line (copper tube) design

  18. Teflon tube Z-axis direction D D Wire pattern Helical cooling line (Teflon tube) design

  19. Novel Design Concepts for Gradient CoilsCarl Gazdzinski, BSc

  20. harmonics = winding layers   1   f ( x ) a a cos( nx ) b sin( nx ) = + + o n n 2 n 1 n 1 = = coefficients = driving currents Concept: The Harmonic Gradient Coil • A multilayered gradient coil with each layer contributing a spatial harmonic of field • Drive layers in variable proportions to obtain variable resulting fields/DSVs • Amounts to a Fourier Series approximation of the desired field:

  21. Continuously Variable DSVs DSV 17cm G= 80 mT/m DSV 33cm G= 39 mT/m DSV 48cm G= 29 mT/m Coil Specs: ID= 40cm Inductance= 300 H/layer Max Current= 300 Amps Unshielded

  22. Conclusions To Date • High performance insertable gradient coils feasible on clinical 1.5T and 3T GE scanners • 10 minute, simple switch-over • Performance increase: 10 - 20 fold over best whole-body gradients • Spatial resolution < 100µm isotropic • Advanced clinical pulse sequences (eg. 3DFIESTA, FSE, DTI) immediately available • Advanced hardware (eg. 8-16 fast receivers) immediately available

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