Opacity to the radio wave and X-ray portion of the electromagnetic spectrum
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Radiodensity (or radiopacity) is opacity to the radio wave and X-ray portion of the electromagnetic spectrum: that is, the relative inability of those kinds of electromagnetic radiation to pass through a particular material. 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 radiolucent. Radiopaque volumes of material have white appearance on radiographs, compared with the relatively darker appearance of radiolucent volumes. For example, on typical radiographs, bones look white or light gray (radiopaque), whereas muscle and skin look black or dark gray, being mostly invisible (radiolucent).
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 specified as -1000 HU.
In modern medicine, radiodense substances are those that will not allow X-rays or similar radiation to pass. Radiographic imaging has been revolutionized by radiodense contrast media, which can be passed through the bloodstream, the gastrointestinal tract, or into the cerebral spinal fluid and utilized to highlight CT scan or X-ray images. Radiopacity is one of the key considerations in the design of various devices such as guidewires or stents that are used during radiological intervention. The radiopacity of a given endovascular device is important since it allows the device to be tracked during the interventional procedure.
The two main factors contributing to a material's radiopacity are density and atomic number. Two common radiodense elements used in medical imagery are barium and iodine.
Medical devices often contain a radiopacifier to enhance visualization during implantation for temporary implantation devices, such as catheters or guidewires, or for monitoring the position of permanently implanted medical devices, such as stents, hip and knee implants, and screws. Metal implants usually have sufficient radiocontrast that additional radiopacifier is not necessary. Polymer-based devices, however, usually incorporate materials with high electron density contrast compared to the surrounding tissue. Examples of radiocontrast materials include titanium, tungsten, barium sulfate,[2] bismuth oxide[3] and zirconium oxide. Some solutions involve direct binding of heavy elements, for instance iodine, to polymeric chains in order to obtain a more homogeneous material which has lower interface criticalities.[4] When testing a new medical device for regulatory submission, device manufacturers will usually evaluate the radiocontrast according to ASTM F640 "Standard Test Methods for Determining Radiopacity for Medical Use."
^Novelline, Robert. Squire's Fundamentals of Radiology. Harvard University Press. 5th edition. 1997. ISBN 0-674-83339-2.
^Lopresti, Mattia; Alberto, Gabriele; Cantamessa, Simone; Cantino, Giorgio; Conterosito, Eleonora; Palin, Luca; Milanesio, Marco (28 January 2020). "Light Weight, Easy Formable and Non-Toxic Polymer-Based Composites for Hard X-ray Shielding: A Theoretical and Experimental Study". International Journal of Molecular Sciences. 21 (3): 833. doi:10.3390/ijms21030833. PMC 7037949. PMID 32012889.
^Lopresti, Mattia; Palin, Luca; Alberto, Gabriele; Cantamessa, Simone; Milanesio, Marco (20 November 2020). "Epoxy resins composites for X-ray shielding materials additivated by coated barium sulfate with improved dispersibility". Materials Today Communications. 26: 101888. doi:10.1016/j.mtcomm.2020.101888. S2CID 229492978.
^Nisha, V. S; Rani Joseph (15 July 2007). "Preparation and properties of iodine-doped radiopaque natural rubber". Journal of Applied Polymer Science. 105 (2): 429–434. doi:10.1002/app.26040.
(radiolucent). Though the term radiodensity is more commonly used in the context of qualitative comparison, radiodensity can also be quantified according...
which the radiodensity of distilled water at standard pressure and temperature (STP) is defined as 0 Hounsfield units (HU), while the radiodensity of air...
They are typically very small and do not cause any symptoms. Their radiodensity is generally similar to cortical bone. No treatment is necessary. Multiple...
an image obtained by CT scanning are displayed in terms of relative radiodensity. The pixel itself is displayed according to the mean attenuation of the...
radiation themselves. In x-ray imaging, contrast agents enhance the radiodensity in a target tissue or structure. In magnetic resonance imaging, contrast...
name is immortalised in the Hounsfield scale, a quantitative measure of radiodensity used in evaluating CT scans. The scale is defined in Hounsfield units...
associated with the root the periodontal ligament space is preserved. Focal radiodensity of the jaw which is not inflammatory, dysplastic, neoplastic or a manifestation...
the collapse of subchondral bone (crescent sign) and ringed regions of radiodensity resulting from saponification and calcification of marrow fat following...
secretions have a radiodensity of 10 to 25 Hounsfield units (HU), but in a more chronic state they become more viscous, with a radiodensity of 30 to 60 HU...
be diagnosed based on signs on the skin. On CT scans, seromas have a radiodensity of 0–20 Hounsfield units, generally in the lower part of this range,...
Lesions may also be sclerotic, which is seen as radiodense. Overall, the radiodensity of myeloma is between −30 and 120 Hounsfield units (HU). Magnetic resonance...
have particularly improved visibility with iodinated contrast. The radiodensity of iodinated contrast is 25–30 Hounsfield units (HU) per milligram of...
order to create better quality motion picture images, having sharper radiodensity contrast, typically at 30 frames per second. The physician controls both...
pennies, they would be difficult to detect using X-ray imaging because the radiodensity of the metal inside the respiratory and gastrointestinal tracts was similar...
(1910–1994), English cricketer Hounsfield scale, a quantitative measure of radiodensity used in evaluating CT scans This disambiguation page lists articles associated...
Average intensity projection - Maximum intensity projection - Thin slice (median plane) - Volume rendering by high and low threshold for radiodensity....
are grounds for a diagnosis of Cushing's syndrome or pheochromocytoma. Radiodensity gives a clue in estimating malignancy risk, wherein a tumor with 10 Hounsfield...
S (October 2021). "Prostatic calcifications: Quantifying occurrence, radiodensity, and spatial distribution in prostate cancer patients". Urologic Oncology...
measure radiodensity and, in reference to CT scans, can provide an accurate absolute density for the type of tissue depicted. The radiodensity, measured...
liquid (moves to lowest point when changing position) Thick, nodular If radiodensity > 20 HU without radiocontrast Sharp margin, < 3 cm, not completely intrarenal...
On CT scan, benign adenomas typically are of low radiodensity (due to fat content). A radiodensity equal to or below 10 Hounsfield units (HU) is considered...
atheroma, with extensive calcification within the wall, a halo-like ring of radiodensity can be seen in most older humans, especially when arterial lumens are...
through a transmitted beam of X-rays, and being able to reconstruct the radiodensity patterns of a plane through the head" after watching an automated apparatus...
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