Arrival time corrected

Unlike Klyshko, who said that the advanced wave is a -function pulse, we consider it to be a continuous, partially incoherent wave. The duration of the advanced wave is in fact determined by the uncertainty of the photon arrival time measurement. With modern detectors, it amounts to at least tens of picoseconds. If the down-conversion experiment is performed in an ultrashort pulsed setting, this uncertainty substantially exceeds the pump pulse width, so the advanced wave can be considered continuous. On the other hand, if the pump laser is continuous, the situation is more complicated and the timing uncertainty must be taken into account more rigorously in order to determine the correct correlation function of the DFG wave and the density matrix of the conditional single photon. 

Figure 4.10 demonstrates the limited utility of a scan when the delay is not chosen correctly. Both mathematical and animal models have demonstrated that, when there is reduced cardiac output, intravenous injection will result in a delayed intra-arterial arrival time and a greater peak arterial enhancement [65]. In patients with reduced cardiac output, therefore, once again, a 35- to 40-s prep delay is typically employed. Increasing the degree of arterial opacification can be accomplished simply by utilizing either a larger injection volume or a faster injection rate. With a test bolus, the time density curve generally has a slightly different geometry from that of the main bolus, as shown in Fig. 4.11. This is likely due to injection of a smaller...

Several approaches have been used to minimize the effects of delay and dispersion in SVD methods [148-151]. A detailed description is beyond the scope of this text for a review of the methods used for correcting for delay, see ref. [78]. Of note, SVD with block circulant decomposition matrix is a tracer-arrival timing-insensitive technique that removes the causality assumption built into SVD (i.e., that the tissue-of-interest signal intensity cannot arrive before the AIF) [148]. This can be the case if the AIF is measured from a diseased vessel. 

Indirect or summary parameters, such as bolus arrival time, time-to-peak (TTP), and full-width at half maximum concentration, are easy to calculate, but are thought to be less accurate than parameters derived from deconvolution with an arterial input function (AIF). Deconvolution corrects for bolus delay and dispersion up to the level of the AIF [114], However, recent studies suggest that both approaches provide quahtatively similar results [115-117] and may be vaUd for clinical purposes [112,118,119],... 

The individual signals from every Pmt, the sum signal the duration of the light burst and the arrival time are available for the successive elaboration.The individual signals of the Pmts are used to reconstruct the position of the scintillation and then to correct by means of an algorithm the Sum signal, in order to take into account the total solid angles subtended by the seven Pmts. 

FIGURE 8.4 Normalized cross-sections vs corrected arrival times for myoglobin. Plot used to create a cross-section calibration for the Synapt instrument. The sample analyzed was equine myoglobin and charge states [M-h8H] +-[M-h 16H] + were used. 

FIGURE 25.10 Beam steering in a phased-anay system during reception. A linearly increasing time delay diffeientiai is introduced for each of the delay lines to correct for the linear time difference in the arrival times. 

This method to correct for a spread of initial ion position was first described by Wiley and McLaren in the 1950s. The acceleration fields are arranged so that ions (of the same m/z) that are further from the detector are accelerated through a longer distance (si) and reach a higher velocity than their counterparts that are initially closer to the detector. The faster ions catch up with the slower ions at the detector and arrive simultaneously. The residual arrival-time spread from spatial spread can be kept insignificant for typical spatial dispersions of 2mm. 

An error analysis is necessary for assessing the accuracy and reliability of any localization result. There are different sources of errors that are not clearly separated. Uncertainties in the determination of the arrival times generally depend on data quality, and how impulsive onsets are. In the presence of noise, low amplitude onsets are easily overlooked. Estimated onset times then are too late or even according to wrong phases. Moreover, the widely used assumption of a homogeneous behavior of the wave propagation may not be correct for a tested structure. 

To perform the calculations as described in Section 1.2.1 (e.g., equation [4]) the arrival time distribution must be corrected for time spent in regions outside of the drift cell (i.e., time spent traversing from the MALDI plate into the drift cell, in skimming and differential pumping regions, and ion optic regions prior to the source of the TOFMS). This will result in the drift time (ta) of the ions within the IM drift cell used in the calculation of collision cross section ... 

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. 

This type of dead time correction is described as nonextending. However, there will be situations, especially at high count rate, where a second pulse might arrive during the dead time period of the first (Figure 14.13). If... 

The equation deployed for dead time correction depends on whether the multiplier behaves as non-paralyzable or as paralyzable. In the former case, the arrival of a second ion at the detector during the time that the detector needs for handling the first ion does not lead to an extension of the dead time. This behavior is often assumed, at least if the count rate is 1 /r. 

Simultaneous analysis of arrival times that are associated with many events provides information that can help to constrain unknowns beyond those of the event locations. Unknowns such as corrections to travel-time predictions, arrival-time measurement precision, and phase names may be inferred if the data set contains sufficient information. Because the unknown parameters include travel-time prediction corrections, uncertainties for each datum, and hypocenters, it is clear that the number of unknowns in the most general formulation of the multiple-event inversion will always outnumber the data. Therefore, the most general formulation will always be underdetermined. The choice of parameters to be included in the inversion and the approaches to constrain the inversion distinguish the various multiple-event applications. 

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