Permanent magnet desktop magnetic resonance imaging system with microfabricated multiturn gradient coils for microflow imaging in capillary tubes
Publication Type:Journal Article
Source:Review of Scientific Instruments , American Institute of Physics, Volume 81, Issue 2, p.9 (2010)
A prototype for a desktop high-resolution MRI velocimetry instrument to characterize flow fields in a capillary tube is demonstrated. This inexpensive compact system is achieved with 0.6 T permanent magnetic configuration (Larmor frequency of 25 MHz) and temperature compensation using off-the-shelf NdFeB permanent magnets. A triaxial gradient module with micro-fabricated copper coils using a lithographic fabrication process has been developed. This gradient module is capable of generating fast switching gradients (< 50 µs) with sensitivities up to 1.7 T/m using custom made current amplifiers, and was optimized for microflow imaging. The RF probe is integrated with the gradient module and is driven by custom electronics. A 2D cross-sectional static image of the inside of a capillary tube with an inner diameter of 1.67 mm is acquired at an in-plane spatial resolution of better than 40 µm. Time-of-flight flow measurements were also obtained using this MRI system to measure the velocity profile of water flowing at
average velocities of above 40 mm/s. The flow profile for slower flow velocities was obtained using phase-encoded techniques, which provides quantitative velocity information in 2D.