WordNet

not transparent to X-rays or other forms of radiation; "barium sulfate is radiopaque" (同)radio-opaque
opacity to X-rays or other radiation (同)radio-opacity
dye that does not allow the passage of X rays or other radiation; used to outline certain organs during X-ray examination

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/06/03 21:01:31」(JST)

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Radiodensity (or radiopacity) refers to the relative inability of electromagnetic radiation, particularly X-rays, to pass through a particular material. Radiolucency indicates greater transparency or "transradiancy" to X-ray photons.^[1] Materials that inhibit the passage of electromagnetic radiation are called radiodense, while those that allow radiation to pass more freely are referred to as radiolucent. The term refers to the relatively opaque white appearance of dense materials or substances on radiographic imaging studies, compared with the relatively darker appearance of less dense materials.

X-rays are part of the electromagnetic spectrum, with photon energies above those of visible (and ultraviolet) light. X-rays are distinguished from gamma rays in that they are produced not by transitions within the atomic nucleus, but either by deceleration of a charged particle or by the transition of state of orbital electrons. Diagnostic X-rays are produced using X-ray tubes. The radio waves portion of the electromagnetic spectrum represents much lower energy/frequency photons than visible light. Thus, referring to the property of X-ray density as radiodensity appears contradictory by current knowledge, but is still used as a historical artifact.

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, and zirconium oxide. 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."

References

^ Novelline, Robert. Squire's Fundamentals of Radiology. Harvard University Press. 5th edition. 1997. ISBN 0-674-83339-2.

External References

Application note on measuring radiopacity

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English Journal

X-ray Visible and Uniform Alginate Microspheres Loaded with in situ Synthesized BaSO4 Nanoparticles for in vivo Transcatheter Arterial Embolization.

Wang Q, Qian K, Liu S, Yang Y, Liang B, Zheng C, Yang XL, Xu HB, Shen AQ.
Biomacromolecules.Biomacromolecules.2015 Mar 2. [Epub ahead of print]
The lack of non-invasive tracking and mapping the fate of embolic agents has restricted the development and further applications of the transcatheter arterial embolization (TAE) therapy. In this work, inherent radiopaque embolic material, barium alginate (ALG) microspheres loaded with in situ synthe
PMID 25728288

Comparative cell attachment, cytotoxicity and antibacterial activity of radiopaque dicalcium silicate cement and white-coloured mineral trioxide aggregate.

Wu BC1, Wei CK, Hsueh NS, Ding SJ.
International endodontic journal.Int Endod J.2015 Mar;48(3):268-76. doi: 10.1111/iej.12310. Epub 2014 Jun 25.
AIM: To comparatively examine the cell attachment, cytotoxicity, and antibacterial activity of radiopaque dicalcium silicate cement (RDSC) and ProRoot white-coloured mineral trioxide aggregate (WMTA).METHODOLOGY: AlamarBlue was used for real-time and repeated monitoring of MG63 cell attachment on fr
PMID 24802368

Infusion of iodine-based contrast agents into poly(p-dioxanone) as a radiopaque resorbable IVC filter.

Singhana B1, Chen A, Slattery P, Yazdi IK, Qiao Y, Tasciotti E, Wallace M, Huang S, Eggers M, Melancon MP.
Journal of materials science. Materials in medicine.J Mater Sci Mater Med.2015 Mar;26(3):5460. doi: 10.1007/s10856-015-5460-0. Epub 2015 Feb 18.
To determine the feasibility of infusing resorbable inferior vena cava (IVC) filter with iodine-based contrast agents to produce a radiopaque, computed tomography (CT)-visible IVC filter. Infused poly(p-dioxanone) (PPDO) was obtained by incubating PPDO in different concentrations of 4-iodobenzoyl ch
PMID 25690619

Japanese Journal

大建中湯の腸管運動に対する効果

菅隼人,内田英二,松本智司,山田岳史,小泉岐博,進士誠一,佐々木順平,谷杏彌,原敬介,古川清憲
日本外科系連合学会誌 37(4), 719-723, 2012-08-30
NAID 10031033218

P-48 歯科用CT用口腔内皮質骨骨密度測定ファントムの開発(器械・技術,一般講演(ポスター発表),第59回日本歯科理工学会学術講演会)

青柳裕仁,吉田みどり,高橋英和,楳本貢三
日本歯科理工学会誌 31(2), 129, 2012-03-25
… A reference phantom was composed of urethane dimethacrylate and triethylene glycol dimethacrylate, hydroxyapatite for radiopaque filler, and poly(methyl methacrylate) for dispersant. …
NAID 110009358524

Influence of inorganic filler content on the radiopacity of dental resin cements

FURTOS Gabriel,BALDEA Bogdan,SILAGHI-DUMITRESCU Laura,MOLDOVAN Marioara,PREJMEREAN Cristina,NICA Luminita
Dental materials journal 31(2), 266-272, 2012-03-01
… All materials were more radiopaque than dentin and 12 materials were more radiopaque than enamel. …
NAID 10030129104

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