Signal difference-to-noise ratio

For characterizing the quality of the image in terms of the potential detectability of structures in the breast, it is useful to introduce the signal difference-to-noise ratio (SDNR). The SDNR is simply the ratio of the signal difference,SD,from (1.3) (but using the detected... 

In Chap. 1, the basic concepts of noise in X-ray imaging were introduced and the dependence of one source, referred to as X-ray quantum noise, on the number of X-rays used to form the image, was discussed. In addition, several quantities used to describe imaging performance, namely the signal-to-noise ratio (SNR), the signal-difference-to-noise ratio (SDNR), the detective quantum efficiency (DQE), and the noise equivalent quanta (NEQ) were reviewed. 

Although measurements of threshold object thickness are difficult to conduct reliably, one may take advantage of the fact that on a given system, they are simply related to the contrast-to-noise ratio (CNR) of alarge area object (sometimes called signal-difference-to-noise-ratio SDNR) as shown in (3.1). 

The base of this estimation is the signal to noise ratio. The lowest signal to noise ratio S/N which is necessary as a minimum to discern a signal from noise is S/N = 2 1 (4). Referring to the limiting values for the granularity Oj, of the film system classes the smallest density difference AD of an defect which would just be visible should be at least two times greater than On. 

Fig.5 shows the noise influence on CCF for both types of pulses and different b values. This influence is weak, especially for q(t) type of signals. For s(t) signals growth of 2-factor critically increases the signal to noise ratio. For q(t) signals this effect is much weaker and depends on quantity of periods in pulses. 

The locations of the maxima of the -field and the E-field are different depending on the mode chosen for the EPR experuuent. It is desirable to design the cavity in such a way that the B field is perpendicular to the external field B, as required by the nature of the resonance condition. Ideally, the sample is located at a position of maxuuum B, because below saturation the signal-to-noise ratio is proportional to Simultaneously, the sample should be placed at a position where the E-field is a minimum in order to minimize dielectric power losses which have a detrimental effect on the signal-to-noise ratio. 

Fig. 16. Maximum achievable signal-to-noise ratio (SNR) on read-out of different writable optical data storage systems as a function of the writing energy (laser power) (121). SQS = Organic dye system (WORM) PC = phase change system (TeSeSb) MO = magnetooptical system (GbTbFe). See text.

Nitrophenyl groups covalently bonded to classy carbon and graphite surfaces have been detected and characterized by unenhanced Raman spectroscopy in combination with voltammetry and XPS [4.292]. Difference spectra from glassy carbon with and without nitrophenyl modification contained several Raman bands from the nitrophenyl group with a comparatively large signal-to-noise ratio (Fig. 4.58). Electrochemical modification of the adsorbed monolayer was observed spectrally, because this led to clear changes in the Raman spectrum. 

It can be seen from Equation 3.38 that unknown variation in gpl20 levels can lead to differences in the correction factor between the experimentally observed IC50 and the desired quantity K4. However, this variation is minimal if low levels of control signal are used for screening (i.e., minimal concentration of CD4 is used to gain an acceptable signal to noise ratio). 

Myopic deconvolution has enough flexibility to account for different cases depending on the signal-to-noise ratio of the measurements ... 

It is not possible to obtain exactly identical flow conditions for the configurations explored. The level of velocity fluctuation at the burner outlet also differs in the various cases. This level was adjusted to get an acceptable signal-to-noise ratio. In the results presented here, the specific heat ratio was taken as equal to y= 1.4, the sound speed Cq = 343 m/s corresponds to a room temperature T = 293 K. The air density is taken equal to = 1.205 kg/m. Laminar burning velocities are... 

The most popular, and also a very accurate, experimental method for measuring nonselective spin-lattice relaxation-rates is the inversion recovery (180°-r-90°-AT-PD)NT pulse sequence. Here, t is the variable parameter, the little t between pulses, AT is the acquisition time, PD is the pulse delay, set such that AT-I- PD s 5 x T, and NT is the total number of transients required for an acceptable signal-to-noise ratio. Sequential application of a series of two-pulse sequences, each using a different pulsespacing, t, gives a series of partially relaxed spectra. Values of Rj can... 

The phase-twisted peak shapes (or mixed absorption-dispersion peak shape) is shown in Fig. 3.9. Such peak shapes arise by the overlapping of the absorptive and dispersive contributions in the peak. The center of the peak contains mainly the absorptive component, while as we move away from the center there is an increasing dispersive component. Such mixed phases in peaks reduce the signal-to-noise ratio complicated interference effects can arise when such lines lie close to one another. Overlap between positive regions of two different peaks can mutually reinforce the lines (constructive interference), while overlap between positive and negative lobes can mutually cancel the signals in the region of overlap (destructive interference). 

The sine-bell, sine-bell squared, phase-shifted sine-bell, and phase-shifted sine-bell squared window functions are generally used in 2D NMR spectroscopy. Each of these has a different effect on the appearance of the peak shape. For all these functions, a certain price may have to be paid in terms of the signal-to-noise ratio, since they remove the dispersive components of the magnitude spectrum. This is illustrated in the following COSY spectra ... 

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