2-hydroxyglutarate peak: resonates at 2.25 ppm.arterial spin labeling (ASL) MR perfusion.dynamic contrast enhanced (DCE) MR perfusion.dynamic susceptibility contrast (DSC) MR perfusion.metal artifact reduction sequence (MARS).turbo inversion recovery magnitude (TIRM).fluid attenuation inversion recovery (FLAIR).diffusion tensor imaging and fiber tractography.MRI pulse sequences ( basics | abbreviations | parameters).iodinated contrast-induced thyrotoxicosis.iodinated contrast media adverse reactions.clinical applications of dual-energy CT.as low as reasonably achievable (ALARA).The values below are written as width and level (W:x L:y) in Hounsfield units (HU). Typical window width and level valuesĪlthough this varies somewhat from institution to institution and vendor to vendor, window width and centers are generally fairly similar. the lower grey level (y) is calculated via WL - (WW ÷ 2)įor example, a brain is W:80 L:40, therefore, all values above +80 will be white and all values below 0 are black.the upper grey level (x) is calculated via WL + (WW ÷ 2).values over x will be white and values below y will be black. When presented with a WW and WL one can calculate the upper and lower grey levels i.e.
When the window level is decreased the CT image will be brighter and vice versa. The window level (WL), often also referred to as window center, is the midpoint of the range of the CT numbers displayed. Narrow windowĭefined as 50-350 HU are excellent when examining areas of similar attenuation, for example, soft tissue. Wide windowĭefined as 400-2000 HU best used in areas of acute differing attenuation values, a good example is lungs or cortical tissue, where air and vessels will sit side by side. Consequently, the transition of dark to light structures will occur over a larger transition area to that of a narrow window width (<1000 HU).Īccordingly, it is important to note, that a significantly wide window displaying all the CT numbers will result in different attenuations between soft tissues to become obscured 1. The window width (WW) as the name suggests is the measure of the range of CT numbers that an image contains.Ī wider window width (2000 HU), therefore, will display a wider range of CT numbers.
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