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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 .
His name is immortalised in the Hounsfield scale, a quantitative measure of radiodensity used in evaluating CT scans. The scale is defined in Hounsfield units (symbol HU), running from air at −1000 HU, through water at 0 HU, and up to dense cortical bone at +1000 HU [12] [13] and more.
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 ...
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 ...
Quantitative computed tomography (QCT) is a medical technique that measures bone mineral density (BMD) using a standard X-ray computed tomography (CT) scanner with a calibration standard to convert Hounsfield units (HU) of the CT image to bone mineral density values. [1]
The first clinical CT scan was performed in a London hospital in 1971 using a scanner invented by Sir Godfrey Hounsfield. [14] The first commercial installation of a CT scanner, an EMI-Scanner Mark I took place at the Mayo Clinic in the U.S. in 1973.
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]
In conventional CT machines, an X-ray tube and detector are physically rotated behind a circular shroud (see the image above right). An alternative, short lived design, known as electron beam tomography (EBT), used electromagnetic deflection of an electron beam within a very large conical X-ray tube and a stationary array of detectors to achieve very high temporal resolution, for imaging of ...