Quantitation between-image

BRET [31, 32]), lock-in detection techniques exploiting optical switches [33], and schemes for alternating D/A excitation (ALEX [34]). The increased attention to quantitative FRET imaging encompasses the use of polarization [35-39], the perennial issue of calibration and standards [40-44], and practical guides to operational principles and protocols ([45, 46] and other references above). The fundamental distinctions between the requirements for live and fixed cell imaging cannot be overemphasized, as is exemplified in a report of erroneous FRET determinations with visible fluorescent proteins (VFPs) in fixed cells [47],... 

Atomic Force Microscopy (AFM). The AFM provides quantitative morpholographic images of solid surfaces at a nanometer scale. It uses a sharp tip scanned over the sample surface to sense attractive or repulsive forces between the tip and the surface. The microscopic image of the surface is obtained as a surface, representing the locus of points of constant force between the tip and the sample. 

A positive consequence of multi-image analysis is the recovery of quantitative information. At this point, it should be taken into account that quantitation from images measured in reflection is never as accurate and precise as from images measured in transmission. The more representative the surface scarmed is from the rest of the sample, then the more reliable the quantitative information will be. When referring to quantitative information, it is possible to differentiate between within-image and between-image quantitation. 

Ramanathan and Ackerman (1999) have shown that solid-state 31P NMR imaging can be used to measure quantitatively the mass of hydroxyapatite in the presence of bone hence to follow non-invasively the resorption and remodeling of calcium phosphate implants in vivo. A three-dimensional projection reconstruction technique has been used to record NMR images in the presence of a fixed amplitude field gradient, the direction of which was varied uniformly over the unit sphere. Chemical selection was achieved using differences in T1 relaxation time of neighbouring protons as the synthetic hydroxyapatite has a shorter T1 (1.8 s at 4.7 T) compared to bone (approximately 15 s at 4.7 T in vivo, 42 s ex vivo). The experimental results demonstrated that a linear relationship exists between image intensity and HAp density. 

Figure 2.16 (a) Scheme followed to obtain within-image "quantitative" information (percent of signal contribution) (b) scheme followed to obtain between-image quantitative information in image analysis. 

In many cases, the methods used to solve identification problems are based on an iterative minimization of some performance criterion measuring the dissimilarity between the experimental and the synthetic data (generated by the current estimate of the direct model). In our case, direct quantitative comparison of two Bscan images at the pixels level is a very difficult task and involves the solution of a very difficult optimization problem, which can be also ill-behaved. Moreover, it would lead to a tremendous amount of computational burden. Segmented Bscan images may be used as concentrated representations of the useful... 

Quantitative analyses ean be aehieved by using the seattering and reeoiling imaging eode (SARIC) simulation and minimization of the R-faetor [33] (seetion B 1.23.4.4) between the experimental and simulated images as a... 

Interpretation of the images is still not straightforward even when there seems to be a simple one-to-one correspondence between black (or white) dots in the image and atom positions. Especially when quantitative data on interatomic distances is to be derived, detailed calculations based on many-beam dynamical theory ( ) must be applied to derive calculated images for comparison with experiment. For this purpose the experimental parameters describing the imaging conditions and the specimen thickness and orientation must be known with high accuracy. 

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