Holographic reconstruction of NMR images in Fresnel transform technique

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.

Real-time holographic reconstruction of NMR images using a liquid crystal-spatial light modulator

“…Then, a satisfactory holographic reconstruction image is obtained [4,5]. From such a viewpoint, the above phase-scrambling Fourier transform imaging is assumed in this study, and the real-time reconstruction of the NMR image is investigated.…”

“…By appropriately setting the imaging parameter JbW that determines the spin phase scrambling, it is easy to contain the NMR signal obtained by phase-scrambling Fourier transform imaging in the linear recording range of the incident light amplitudelight transmission ratio char-acteristics of the hologram recording medium. Then, a satisfactory holographic reconstruction image is obtained [4,5]. From such a viewpoint, the above phase-scrambling Fourier transform imaging is assumed in this study, and the real-time reconstruction of the NMR image is investigated.…”

“…The authors noted that the description of the NMR signal is of the same form as the diffraction of the light or the sound wave, and investigated the method for the holographic reconstruction of the NMR image [4,5]. Holography can be considered as a kind of optical information processing.…”

Fast reconstruction of three‐dimensional images in Fresnel transform imaging technique using optical imaging system

“…As a means of remedying the problem of reconstruction time, this study applies holographic reconstruction [5] to three-dimensional image reconstruction. It is noted that the expression for the NMR signal obtained by Fresnel transform imaging has the same form as the expression for light diffraction.…”