Transverse spatial resolution

FIGURE 3.4 Performance of the fluorescence up-conversion microscope, (a) Evaluation of the time-resolution with the 100 x objective lens , up-converted fluorescence -F-, the first derivative. By the fitting analysis, the time-resolution of the microscope was evaluated as 520 fs. (b) Evaluation of the transverse (XY) spatial resolution with the 100 x objective lens. A CCD image of the excitation pulses (inset) and the beam profile along the lateral (X) direction. By the fitting analysis, the transverse resolution was evaluated as 0.34 pm. (c d) Evaluation of the axial (Z) spatial resolution with the 100 x objective lens , up-converted fluorescence -I-, the first derivative. By fitting analysis on the first derivative coefficient, the axial resolution was evaluated as 1.1 pm with the 50 pm pinhole (c) and 5.3 pm without pinhole (d). (Rhodamine B, 2 x 10" mol dm in methanol, 600 nm.) (Erom Eujino, T. and Tahara, T., Appl Phys. B 79 145-151, 2004. Used with permission.)... 

An ejected photoion can have nonzero transversal velocity, Autr, if a part of the excitation energy is converted to kinetic energy during the photodetachment from the surface. It is assumed that the average kinetic energy of the transverse motion of a photoion equals kin- Then, in a way similar to the above procedure, it is possible to estimate the spatial resolution due to this effect. To achieve the spatial resolution Ax of 3-5 A at Fmax = 0.2 eV/A and r - 103 A, it is necessary to realize a very precise MPI of the chro-mophore on the cooled tip with excess of transversal kinetic energy of only = 10-3 eV. 

Cross-link density and parameters relating to the network structure can be measured by NMR by analysis of the transverse relaxation decay (cf. Section 1.3) and the longitudinal relaxation in the rotating frame [67]. Combined with spatial resolution, the model-based analysis of relaxation yields maps of cross-link density and related parameters [68]. Often the statistical distribution of relaxation parameters over all pixels provides a reduced data set with sufficient information for sample characterization and discrimination [68]. 

The spatial resolution of FT-IR microspectroscopy, without sacrificing spectral quality and resolution, makes imaging possible. Shortly after the introduction of the first research-quality IR microscope by Messerschmidt and Sting in 1986, Wetzel, Messerschmidt and Fulcher reported spectra obtained from wheat kernel transverse sections in situ, and compared them with flour milling fractions [7]. This was achieved with an accessory IR-PLAN microscope optically interfaced to a Nicolet interferometer bench. Subsequently, at the Agriculture Canada laboratory the same model IR-PLAN was interfaced to a Bomen Michelson IR 100 spectrometer such that, over the period of a year, transverse sections of wheat kernels, vanilla beans, peppercorns and soybeans were manually line-mapped to reveal any differences in microchemical structural characteristics between their different botanical parts [8]. 

The spatial resolution of a PET scanner is determined by the FWHM of point-spread-functions (PSF) obtained from measurement of activity distribution from a point source. The spatial resolution can be transverse radial, transverse tangential, and axial, and these values are given in Table 6.1 for scanners from different manufacturers. 

Figure 6.4. Arrangement of six-point sources in the measurement of spatial resolution. Three sources are positioned at the center of the axial FOV and three sources are positioned at one-fourth of the axial FOB away from the center. At each position, sources are placed on the positions indicated in a transverse plane perpendicular to the scanner axis. (Reprinted with the permission of The Cleveland Clinic Center for Medical Art Photography 2009. All Rights Reserved)...

Describe the method of measuring transverse radial, transverse tangential, and axial spatial resolutions of a PET scanner. 

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