Scan duration

The velocity of the scanner V ax and the desired spectral resolution A > determine the scan duration At and thereby the time resolution ... 

With the advent of newer 16- to 64-slice MDCT scanners, no technical compromise is now needed since these systems are capable of using sub-millimeter collimation and sub-millimeter image reconstruction, with a subsequent shorter scan duration and longer scan ranges. 

In order to determine scan delays correctly, three factors have to be considered (1) contrast agent injection duration, (2) contrast arrival time (Carr) and (3) scan duration. 

Fig. 8.4. Simulated aortic contrast attenuation curve with different scan delays (AT) designated for multiple scanner generations. AT has to be lengthened with shorter scan durations provided by a CT scanner with increasing detector width and rotational speed. A faster scanner may utilize peak contrast enhancement more efficiently than a slower one...

Figure 10. Sequential images of sections through the short axis of the left ventricle generated after weighted subtraction processing of volume images. Each slice is 7.8 mm thick and 0.06 s scan duration (Sinak et al., 1984c).

When a smaller scan rate is considered, the A— anion radical formed upon reduction may evolve as in the sequence of eqns (2) + (3). Indeed when the scan duration is small enough as compared to the half... 

From an experimental point of view, the SVET measurements show it exits a stationary state of the galvanic cell itself The motion of the solution is confined in the vicinity of the tip and limited in time (short scanning duration) and consequently the homogenous and heterogeneous reactions involved in the self-heating of the steel sheet considered in the Nernst-Planck s model are not disturbed. 

Fig. 4 Perivascular distribution of multiple sclerosis lesions at 7 Tesla. T2 -weighted image with 0.5 mm x 0.5 mm x 1.0 mm resolution and scan duration equal to 4 minutes (a). Zoomed in region of signal enhancement around centrally coursing vein (b)...

The limits of transition region BC are not very distinct and depend on the experimental conditions. At high potential scan rates (short duration of the experiment), passivation will start later (i.e., potential will be somewhat more positive, and for a short time the currents may be higher than i ). 

Under conditions of p-PIXE, the beam can be scanned across the surface of the specimen and thus provide concentration data as a function of position. Since spectra have to be accumulated at many points on the specimen with this technique, the analysis duration may be hours rather than minutes. Concentration values at different points or concentration profiles for selected elements can be determined by... 

In Fig. 2.13 the mass intensities for carbon dioxide (m/e = 44) and methyl formate (m/e = 60) during a potential scan are given. While the signal for C02 follows the current pattern in the whole potential range that for HCOOCH3 does not. This indicates the existence of parallel pathways. Methyl formate was also detected as an electrolysis product in long duration experiments [66],... 

Waves I and II in Figure 2.81(b) are due to the formation of Cu(I) and Cu(II) surface oxides. Subsequent reduction of these films occurs during the cathodic sweep to give waves III and IV. The points A to D represent the potentials at which reflectivity data were collected during the voltammetric scan. The potential was ramped at lOmV/s until one of these potentials was reached, at which the scan was stopped for the duration of the data acquisition. The spectrum collected at A represents the condition of the electrode surface... 

In subprograms for operating scanning devices, the primary algorithm may include a do and wait operation (for a stepper motor) or a do and look operation (for a servo system). Try to avoid problems that could arise if you move your software to a faster, newer PC. With a new PC running at a faster clock speed than an old one, the faster do operation will require a longer wait if the scanner operation is matched to the duration of do + wait. Thus, the CAM should be treated as three separate units the microscope, the interface, and the PC. The PC will become obsolete before the microscope. 

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