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The Hounsfield scale (/ ˈ h aʊ n z f iː l d / HOWNZ-feeld), named after Sir Godfrey Hounsfield, is a quantitative scale for describing radiodensity. It is frequently used in CT scans , where its value is also termed CT number .
Though the term radiodensity is more commonly used in the context of qualitative comparison, radiodensity can also be quantified according to the Hounsfield scale, a principle which is central to X-ray computed tomography (CT scan) applications. On the Hounsfield scale, distilled water has a value of 0 Hounsfield units (HU), while air is ...
Hounsfield built a prototype head scanner and tested it first on a preserved human brain, then on a fresh cow brain from a butcher’s shop, and later on himself. On 1 October 1971, CT scanning was introduced into medical practice with a successful scan on a cerebral cyst patient at Atkinson Morley Hospital in Wimbledon, London, United Kingdom ...
The radiodensity, measured in Hounsfield Units (HU, also known as CT number) is inaccurate in CBCT scans because different areas in the scan appear with different greyscale values depending on their relative positions in the organ being scanned, despite possessing identical densities, because the image value of a voxel of an organ depends on ...
Quantitative CT scans are primarily used to evaluate bone mineral density at the lumbar spine and hip. In general, solid phantoms placed in a pad under the patient during CT image acquisition are used for calibration. These phantoms contain materials that represent a number of different equivalent bone mineral densities.
In medicine, the dense artery sign or hyperdense artery sign is an increased radiodensity of an artery as seen on computer tomography (CT) scans, and is a radiologic sign of early ischemic stroke. [1] In earlier studies of medical imaging in patients with strokes, it was the earliest sign of ischemic stroke in a significant minority of cases. [2]
Portable CT scanners can be brought to the patient's bedside and do a scan without getting the patient out of bed. Some portable scanners are limited by their bore size and therefore mainly used for head scans. They do not have image viewing capabilities directly on the scanner. The portable CT scanner does not replace the fixed CT suite.
This makes CT scan the most appropriate term, which is used by radiologists in common vernacular as well as in textbooks and scientific papers. [218] [219] [220] In Medical Subject Headings (MeSH), computed axial tomography was used from 1977 to 1979, but the current indexing explicitly includes X-ray in the title. [221]