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The Hounsfield unit (HU) scale is a linear transformation of the original linear attenuation coefficient measurement into one in which the radiodensity of distilled water at standard pressure and temperature is defined as 0 Hounsfield units (HU), while the radiodensity of air at STP is defined as −1000 HU.
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] Quantitative CT scans are primarily used to evaluate bone mineral density ...
The Agatston score, named after its developer Arthur Agatston, is a measure of calcium on a coronary CT calcium scan. [7] The original work, published in 1990, [8] was based on electron beam computed tomography (also known as ultrafast CT or EBCT). The score is calculated using a weighted value assigned to the highest density of calcification ...
Radiolucency or hypodensity indicates greater passage (greater transradiancy) to X-ray photons [1] and is the analogue of transparency and translucency with visible light. Materials that inhibit the passage of electromagnetic radiation are called radiodense or radiopaque , while those that allow radiation to pass more freely are referred to as ...
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.
Non-contrast CT (at left) showing peripelvic fluid accumulations, which may be hydronephrosis. CT urography (at right) reveals non-dilated calyces and pelvises. The fluid accumulations are thus peripelvic cysts. Parapelvic cysts originate from around the kidney at the adjacent renal parenchyma, and plunge into the renal sinus. Peripelvic cysts ...
The Haller index, created in 1987 by J. Alex Haller, S. S. Kramer, and S. A. Lietman, [1] is a mathematical relationship that exists in a human chest section observed with a CT scan. It is defined as the ratio of the transverse diameter (the horizontal distance of the inside of the ribcage ) and the anteroposterior diameter (the shortest ...
A uniqueness theorem (Hu [1962]) states that if f(x,y) is piecewise continuous and has nonzero values only in a finite part of the xy plane, moments of all orders exist, and the moment sequence (M pq) is uniquely determined by f(x,y). [1] Conversely, (M pq) uniquely determines f(x,y). In practice, the image is summarized with functions of a few ...