1. Holographic reconstruction of NMR images in Fresnel transform technique
- Author
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Kunio Tanaka, Satoshi Ito, and Yoshifumi Yamada
- Subjects
Physics ,Computer Networks and Communications ,business.industry ,Dynamic range ,Holography ,Physics::Optics ,General Physics and Astronomy ,Pulse sequence ,law.invention ,Quantization (physics) ,symbols.namesake ,Nonlinear system ,Computer Science::Graphics ,Optics ,Quadratic equation ,Fourier transform ,law ,symbols ,Electrical and Electronic Engineering ,business ,Fresnel diffraction - Abstract
Since the signal obtained in the NMR Fresnel transform technique is given by an equation similar to that of the Fresnel diffraction equation in light, a technique in which the NMR signal in the Fresnel transform technique is recorded on a transparent film as a hologram and an image is reconstructed from such a hologram by using coherent laser light. Theoretical and experimental studies on such a technique are made in conjunction with the comparison between this technique and another technique in which the hologram is made from the NMR signal in the conventional Fourier imaging technique. The experiments show that considerably good quality images are reconstructed from the holograms in 16 shades of gray made from the signals in the NMR Fresnel transform technique since the dynamic range of the signal in this technique is small. This results in a quantization of the signal with little loss of the information, and the fringe pattern of the hologram is distributed widely over the hologram plane. The experiments show also that it is difficult to reconstruct good quality images from the holograms in 16 shades of gray made from the signals in the NMR Fourier transform technique. This is because most of the information of the image is lost by a quantization of the signal in such a small number of shades of gray since the dynamic range of the signal in the NMR Fourier transform technique is extremely large. It is shown also that the dynamic range of the signal can be decreased using a quadratic nonlinear field gradient in the pulse sequence in the NMR Fourier transform technique, and great improvement in the quality of the optically reconstructed image is obtained. more...
- Published
- 1990
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