Noise image

I. Cespedes and J. Ophir, Reduction of image noise in elastography, Ultrason. Imaging, 1993, 15, 89-102. 

Even if strong A -way methods are used to reduce image noise, compress data, and improve data cube visualization, weak multiway methods are more often used as they facilitate classification using classical single-point spectra. 

Similar to all scanning microscopies, the resolution in SFM depends on the effective size of the probe and its modifications which arise from sample-probe interactions. Theoretically, the effective size is determined by the probe geometry and the force-distance dependence between the tip and sample. In addition, the aperture increases because of the tip-sample deformation, surface roughness, capillary forces, and various sources of noise. Experimentally, the resolution is limited by the sensitivity of the force detection system, the image noise, and the scanner precision. 

Both OSEM and MLEM methods reduce image noise compared to... 

The image noise is characterized by a parameter called the noise equivalent count rate (NECR) which is given by... 

Another type of image noise arises from nonrandom or systematic addition of counts due to imaging devices or procedural artifacts. For example, bladder uptake of 18F-FDG may obscure the lesions in the pelvic area. Various streak type artifacts introduced during reconstruction may be present as noise in the image. 

The daily QC check of CT scanner includes (a) laser alignment (b) CT number of water (c) tomographic uniformity (d) tomographic image noise. 

In film-based mammography systems, another important noise source is the random fluctuation contributed by the granularity of the film itself The film emulsion is composed of grains of silver halide and their random structure increases the total noise. The overall image noise can be estimated by treating noise sources as being statistically independent, giving ... 

MDCT can be regarded as helpful and advantageous per se. As mentioned above, modern scanners allow for submillimeter collimations, so that slices with <1 mm can be obtained without problems. Our own experience and the data from the literature, however, showed that such thin slices are not superior in the detection of liver metastases. On the contrary, the large number of slices to be reviewed and the strong increase in image noise are rather disadvantageous [17,25]. 

The patient should he positioned as comfortably as possible for any examination. For this purpose,special headrests, arm supports (particularly for supporting the arms in the above-head position), and cushionlike supports for the knees are available. The patient must be positioned on a soft surface, which should in addition be heat-insulated. Because most CT scanners are no longer water-cooled but dissipate their heat directly into the room air and because the scanner rooms must normally be fully air-conditioned for this reason, the patient should be covered with a protective sheet. None of the materials employed should contain silicate, glass or other absorbing substances, since the presence of these substances in the scan field can lead to artifacts or increased image noise as a result of beam hardening. 

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