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Contrast resolution or contrast-detail is an approach to describing the image quality in terms of both the image contrast and resolution. Contrast resolution is usually measured by generating a pattern from a test object that depicts how image contrast changes as the structures being imaged get smaller and closer together.
In contrast-enhanced imaging, high-atomic-number contrast agents with K absorption edges in the diagnostic energy range may be present in the body. K-edge energies are material specific, which means that the energy dependence of the photo-electric effect is no longer separable from the material properties, and an additional term can be added to Eq.
Projectional radiography, also known as conventional radiography, [1] is a form of radiography and medical imaging that produces two-dimensional images by X-ray radiation. The image acquisition is generally performed by radiographers , and the images are often examined by radiologists .
In contrast to neuroimaging, neuroradiology is qualitative (based on subjective impressions and extensive clinical training) but sometimes uses basic quantitative methods. Functional brain imaging techniques, such as functional magnetic resonance imaging , are common in neuroimaging but rarely used in neuroradiology. Neuroimaging falls into two ...
The maximum contrast of an image is termed the contrast ratio or dynamic range. In images where the contrast ratio approaches the maximum possible for the medium, there is a conservation of contrast. In such cases, increasing contrast in certain parts of the image will necessarily result in a decrease in contrast elsewhere.
Two forms of radiographic images are in use in medical imaging. Projection radiography and fluoroscopy, with the latter being useful for catheter guidance. These 2D techniques are still in wide use despite the advance of 3D tomography due to the low cost, high resolution, and depending on the application, lower radiation dosages with 2D technique.
Carbon dioxide is a negative contrast medium and it has a low radiopacity (while iodinated contrast media are defined as positive contrast media due to their high radiopacity). Contrast is caused by the different X-ray absorption coefficients between the tissue and the contrast agent.
4DCT has started to be used for diagnostic radiology procedures, for example looking at joint problems, the cardiac cycle and parathyroid washout of contrast.Downsides of 4DCT for diagnostic purposes include large and complex datasets, and increased radiation dose to the patient.