PubMed · 8246787
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J J Art, M B Goodman. 1993. Rapid scanning confocal microscopy.. https://doi.org/10.1016/s0091-679x(08)60999-1
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Using a set of coupled radiation transport equations, we derive image operators for luminescence optical tomography with which it is possible to reconstruct concentration and mean lifetime distribution from information obtained from dc and time-harmonic optical sources. Weight functions and detector readings were computed from analytic solutions of the diffusion equation and from numerical solutions of the transport equation by Monte Carlo methods. Detector readings were also obtained from experiments on vessels containing a balloon filled with dye embedded in an Intralipid suspension with dye in the background. Image reconstructions were performed by the conjugate gradient descent method and the simultaneous algebraic reconstruction technique with a positivity constraint. A concentration correction was developed in which the reconstructed concentration information is used in the mean-lifetime reconstruction. The results show that the target can be accurately located in both the simulated and the experimental cases, but quantitative inaccuracies are present. Observed errors include a shadowing effect in regions that have the lowest weight within the inclusion. Application of the concentration correction can significantly improve computational efficiency and reduce error in the mean-lifetime reconstructions.
Techniques have been developed for the routine reliable imaging of polysaccharides by atomic force microscopy (AFM). The polysaccharides are deposited from aqueous solution onto the surface of freshly cleaved mica, air dried, and then imaged under alcohols. The rationale behind the development of the methodology is described and data is presented for the bacterial polysaccharides xanthan, acetan, and the plant polysaccharides l-carrageenan and pectin. Studies on uncoated polysaccharides have demonstrated the improved resolution achievable when compared to more traditional metal-coated samples or replicas. For acetan the present methodology has permitted imaging of the helical structure. Finally, in addition to data obtained on individual polysaccharides, AFM images have also been obtained of the network structures formed by kappa-carrageenan and gellan gum.
Magnetic resonance imaging allows numerous k-space sampling schemes such as cartesian, polar, spherical, and other non-rectilinear trajectories. Non-rectilinear MR acquisitions permit fast scan times and can suppress motion artifacts. Still, these sampling schemes may adversely affect the image characteristics due to aliasing. Here, the Fourier aliasing effects of uniform polar sampling, i.e., equally spaced radial and azimuthal samples, are explained from the principal point spread function (PSF). The principal PSF is determined by assuming equally spaced concentric ring samples in k-space. The radial effects such as replication, smearing, truncation artifacts, and sampling requirements, are characterized based on the PSF.