T Inouye

NMR Flow Imaging

The present study describes a method for measuring a spatial distribution of flow velocity in fluid. This method employs two selective irradiation pulses; the first pulse is used for selective saturation and the second pulse is used for selective observation. To image flowing fluid correctly, images are reconstructed from a set of second echoes in a pulse sequence similar to Carr-Purcell-Meiboom-Gill sequence. The velocity image is computed using two images; one is that of the nuclear spin density and the other is that with 100 msec delay time between the two selective irradiation pulses. The obtained velocity distribution of water in a circular pipe is parabolic and agrees well with that of Poiseuille flow, which has proved the method developed here of great use in the study of fluid flow.

NMR imaging of advanced ceramics during the slip casting process

The slip casting process in advanced ceramics was observed using an NMR imaging system. After the Al2O3 water suspension (Al2O3 slip) was poured into the mould, cross section of the mould was imaged. In the sequentially taken NMR images the Al2O3 slip was clearly distinguishable from the deposit because of the difference in relaxation time T2 and an increase of the deposit thickness with time was observed. These results indicate that NMR imaging is useful in the nondestructive monitoring of the slip casting process.

An NQR imaging experiment on a disordered solid

This Communication reports the first NQR imaging experiment on quadrupolar nuclei in a powdered solid

Nonlinear amplitude compression in magnetic resonance imaging: quantization noise reduction and data memory saving

Dynamic range improvement in magnetic resonance imaging (MRI) by nonlinear amplitude compression is proposed. Quantization noise reduction by a factor of 10 to 20 is confirmed by a numerical simulation, provided an appropriate nonlinear transform is chosen. The piecewise-linear transform is the best nonlinear transform studied so far. Implementing amplitude compression requires no additional hardware in a usual MRI system if the low spatial frequency lines of the magnetic resonance (MR) signal are selectively prescanned through an attenuator. The method will be particularly effective in 3-D imaging of large objects. MR angiography, and imaging of solids.<<ETX>>

A real-time NMR image reconstruction system using echo-planar imaging and a digital signal processor

A real-time NMR image reconstruction system using echo-planar imaging (EPI) and a single-chip digital signal processor (TMS320C30) has been developed. The image reconstruction time for one 64*64-pixel image is about 50 ms. This system has achieved image refresh intervals of less than 100 ms for 64*64 pixel images using the EPI sequence with a data acquisition time of about 40 ms. An experiment performed using a sphere falling through static water has demonstrated that this system is a powerful tool for interactive observation of unsteady phenomena for long periods.

Fast imaging of the second moment using magic echo trains.

Approaches are discussed to imaging of the second moment of proton NMR dipolar spectra. Two methods are proposed using the peak shapes of the magic echo trains for evaluation of the second moment. One is a quasi-multidimensional FT approach where the peak shapes of the magic echoes are spatially resolved, and the other is the fast version of the former approach, collecting the same data in a much shorter measurement time. Preliminary results of spatially 2D, as well as 1D, experiments are reported.

Research and Development Activities towards Computer Assisted Radiology in Japan

Recent research and development activities in computer assisted radiology in Japan are briefly described. Medical and technical trends in X-ray computerized tomography, nuclear magnetic resonance imaging, digital radiography and some other CT related technologies are summarized.