Contrast resolution

To evaluate the image quality of the processing system, one can determine classical parameters like spatial resolution, contrast resolution, dynamic range, local and global distortion. Guidelines for film digitization procedures have been well described now. Furthermore, a physical standard film for both equipment assessment and digitization calibration and control, will be available in a next future (4). 

Increasing spatial and to some extent also contrast resolution of X-ray equipment and advances in the understanding of disease processes are in favor of improved X-ray contrast agents which provide important additional information. 

Flying Spot Microscope, A television-type scanner illuminates specimen in compound microscope to obtn pictures superior in size, brightness, contrast resolution to those of normal microscope. Discrete particles are automatically oounted and sized Ref F. Roberts, J.Z. Young D. Causley, Electronics 26, 137—39 (July 1953)... 

To accommodate the diverse needs of lithographic processes and device design specifications, resist properties vary. However, a few primary characteristics common to all resists can be used to gauge their performance. These characteristics include sensitivity, contrast, resolution, and etching resistance. Because resist performance is strongly operation dependent, comparison between materials must be made under identical conditions. 

Even if spatial and contrast resolution of these imaging modalities will increase in the future, it might be difficult to differentiate the artery from the vein on the anterior surface of the cord. The anterior spinal artery and vein run very close together. The branching of a radicular artery or vein has a very similar hairpin-configuration, and the level at which a segmental in- or outflow occurs cannot be predicted in a given case. 

An imaging mode called "wet-STEM" recently developed in ESEM, and schematically presented in Figure 3.17, allows the observation of nano-objects suspended in a liquid phase, with a few nanometers resolution (87). The idea behind this technique is simply to perform STEM-in-SEM, that is SEM in transmission mode, in an environmental SEM, in the wet state. The ESEM is interesting for the ability to keep samples wet or liquid, and the STEM mode results in high contrast, resolution and thickness of transparency. 

Compared with cut-film selective intra-arterial catheter angiography recorded directly on to X-ray film, intra-arterial digital subtraction angiography (DSA) (Fig. 12.1) is quicker the images are easier to manipulate and store and contrast resolution is better although spatial resolution is less. However, there is no evidence that less contrast is used or that it is much safer (Warnock et al. 1993). Even for imaging only as far as the carotid bifurcation. 

The increase in density in HUs or CT numbers is linearly dependent on the iodine concentration (mgl/mL) of the injected contrast medium. CT has two advantages over projection radiography. One is the significant increase in contrast resolution and sensitivity, which reduces the contrast detection threshold, thereby allowing a lower level of concentration of contrast media to be administered the other is the cross-sectional imaging, which permits successive visualization of structures without the superposition of other tissues to affect the image quality (632). 

Increasing administered activity increases the contrast resolution True... 

The older established resists were generally slower, but also exhibit good RPL and highest contrast/resolution. Of the resists evaluated, the two resists with the best overall combination of RPL, contrast and sensitivity were the AZ-4110 and Dynachem OFPR-800 systems. The newest resist, Allied P-5019, bears watching also due to its very high contrast performance. 

CT has a superior contrast resolution compared with that achieved on conventional radiographs. Optimal bowel filling and distension of the lumen with water or contrast media is essential to evaluate bowel loops and its surroundings. We must keep in mind that CT implies an increased radiation exposure. The information gained must justify the increased radiation burden. Indications for CT use include trauma, intestinal wall and liver/spleen parenchymal evaluation, abscesses and tumor staging (Devos and Meradji 2003 Nicolaou et al. 2005 Boudiaf et al. 2001). 

Even if the difference between the diagnostic value of CT and MRI has become smaller due to the introduction of MDCT, MRI with liver-specific contrast agents has to be considered the modality of choice for dedicated liver examinations. MRI has an excellent contrast resolution which allows for sensitive detection of intrahepatic lesions. 3D dynamic gadolinium chelate-enhanced scans enable the as-... 

In the last decade there has been great interest in the development of macromolecular contrast agents to be used in Magnetic Resonance Imaging (MRI), a new diagnostic technique which provides a better contrast resolution of the tissues than others techniques, such as X-ray, ultrasound and scintigraphy. 

Increase in temperature usually improves resolution and solubiUty and decreases the viscosity of the mobile phase. Consequently, the production rate increases, provided that the selectivity of separation or stability of the separated compounds and stationary phases is not compromised. In contrast, resolution in chiral chromatography often improves at lower temperatures. 

In patients with cancer, the demonstration or exclusion of lymph node metastases is an important component of tumor staging besides evaluation of local tumor extent and has crucial implications for the patient s prognosis and therapeutic strategy, especially when deciding on curative versus palliative treatment. CT, with its limited contrast resolution, cannot differentiate metastasis from normal lymph node tissue. Unfortunately, MRI is also not able to distinguish between benign and malignant lymph... 

Image quality in CT is determined both by spatial resolution and contrast. It is the tube current (mA) that primarily affects spatial resolution, whilst the peak tube potential (kVp) affects both spatial and contrast resolution. Other factors influencing spatial resolution - the ability to observe small details - include in the imaging plane the collimation (in SDCT) - or section collimation (in MDCT) and the focal spot size of the tube. The slice (section) thickness and the choice of pitch influence spatial resolution along the Z-(long) axis of the patient - thinner slices and a lower pitch leading to an improvement in spatial resolution (Huda et al. 2002). 

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