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calcium tungstate screens recycling

Tungsten Recycling in the United States in 2000

Because of tungsten’s many diverse uses, numerous types of scrap were available for recycling by a wide variety of processes. In 2000, an estimated 46 percent of U.S. tungsten supply was derived from scrap. The ratio of tungsten consumed from new scrap to that consumed from old scrap was estimated to

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Rare earth screens and silver

andcalcium tungstate screens, found thatXDfilm,afine grained filmusedwitharareearthsystem (Trirnax, 3M Co.,St.Paul,Minn.), contained approximately 23%less silver than XMand Kodak RPfilms. Thelowsilver film was useful because oftheincreased brightness rare earth phosphors. These phosphors operate with increased detection efficiency permitting anexposure

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Rare earth screens for panoramic radiography

Abstract. Six panoramic radiographs, each made with a different screen/film combination, were compared for "periapical visibility" by fourteen dentists. Two combinations (a par-speed and a high-speed) used calcium tungstate screens, and three used rare earth screen systems four times faster than par-speed. One other combination consisted of a ...

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Physical Properties of Calcium Tungstate X‐Ray Screens ...

Apr 15, 2004  Abstract. The absolute energy of the light from a fluorescent calcium tungstate x‐ray screen, its spectral distribution, and the efficiency of conversion from x‐rays to light have been determined. The absolute energy and its spectral distribution were obtained spectrographically by comparison with a standard tungsten filament lamp.

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Rare-Earth Screens Versus Calcium Tungstate Screens ...

If one excludes the the correlahumerus from appeared in the May 1982 issue of RDIoLocn that rare-earth screens give inherently inferior with their calcium conclusions tungstate were screens. limited Although to the particulr the could convince one images compared authors state described that conditions consideration, then only 3/ 14 lesions recurred, and hence the bone involved may be as important or

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Rare earth screens for panoramic radiography - ScienceDirect

Apr 01, 1984  The radiographs produced by the faster rare earth screen/film combinations were found to be similar in quality to those produced by calcium tungstate screens. Rare earth screens could be used for panoramic radiography while maintaining quality and

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Calcium tungstate definition of calcium tungstate by ...

Blue-emitting screens use materials such as calcium tungstate and have been in use since the 19th century. His laboratory tested 8000 substances for fluorescence and found calcium tungstate to be superior. The intensifying screen was designed by Edison, who used calcium tungstate as a phosphor.

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X-ray intensifying screens greatly enhance the detection ...

May 01, 1978  Using the best film-screen combination, a calcium tungstate phosphor screen (Dupont, Cronex Lighting Plus) with Kodak RP ROYAL X-OMAT film, and exposure at -70°C, we find a 30- to 40-fold increase in the detection of 1251 and an 8- to 10-fold increase in the detection of 32 P. MATERIALS AND METHODS Preparation of test strips.

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CASSETTES INTENSIFYING SCREENS FILMS

SCREENS 1) BASE –This acts as a support for all other layers of intensifying screen. –Made of polyester plastic 1mm thick. –Characteristics:-a) Must be flexible yet tough –good contact b) Rigid –stay in place c) Chemically inert –not react with phosphor d) Radiolucent –transmission of x-ray photons KAAB (C)

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Intensifying screens Flashcards Quizlet

how much better are rare earths than calcium tungstate when it comes to x-ray to light conversion efficiency 3-4 times better since rare earth phosphors absorb 50% more x-rays than calcium tungstate, and convert 3-4 times as much absorbed x-ray energy into light energy, which type of phosphor is faster (more film density per mAs)

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Tungsten Recycling in the United States in 2000

Tungsten Recycling in the United States in 2000 By Kim B. Shedd ... referred to as “white ore,” is calcium tungstate (CaWO: 4). Wolframite, which is sometimes referred to as “black ore,” is the name for a mineral and the mineral group to which it belongs. The wolframite group is a solid solution series of

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Rare earth screens and silver

Compared toconventional calcium tungstate intensify-ingscreens, rareearth screens havethedisadvantages ofhigher cost and unfamiliar exposure characteristics. Buttheyhaveimportant advantages aswell:theirability toreduce radiation exposure hasbeenemphasized [1], while their potential toconserve silver hasbeenlargely ignored.

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Evaluation of rare earth intensifying screens in ...

Each pair had one film taken with a conventional (calcium tungstate) intensifying screen system and one taken with a rare earth system. Statistically significant differences in accuracy were found in only six of the 36 measurements. Three of the differences favored the accuracy of the rare earth system (Pogonion Y, S Pogonion X and Y), while ...

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Rare earth screens for panoramic radiography - ScienceDirect

Apr 01, 1984  The radiographs produced by the faster rare earth screen/film combinations were found to be similar in quality to those produced by calcium tungstate screens. Rare earth screens could be used for panoramic radiography while maintaining quality and

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Calcium tungstate screens Article about calcium ...

Calcium is produced industrially by two methods: (1) by heating a briquetted mixture of CaO and powdered aluminum at 1200°C in a vacuum of 0.01-0.02 mm Hg; the calcium vapors, evolved according to the equation 6CaO + 2A1 = 3CaO ⋅ A1 2 O 3 + 3Ca, condense on a cold surface; (2) by electrolyzing a melt of CaCl 2 and KCl, using a liquid copper ...

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Physical Properties of Calcium Tungstate X-Ray Screens ...

The absolute energy of the light from a fluorescent calcium tungstate x-ray screen, its spectral distribution, and the efficiency of conversion from x-rays to light have been determined. The absolute energy and its spectral distribution were obtained spectrographically by comparison with a standard tungsten filament lamp. Equations are given for determining the distribution of light in the ...

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2: Film—Screen Radiography Musculoskeletal Key

Calcium tungstate screens emit light in the blue/blue–violet portion of the visible light spectrum; rare-earth screens primarily emit green light, although a few emit blue light. Green-sensitive (orthochromatic) film must be used with green-emitting intensifying screens and blue-sensitive film with blue-emitting intensifying screens.

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Calcium Tungstate - Rubamin

Calcium Tungstate. Chemistry books will describe calcium tungstate as a compound that contains an oxoanion of tungsten. Technically, all useful tungsten ores are tungstates and most of these tend to occur along with molybdates.

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Calcium tungstate Article about calcium tungstate by The ...

Scheelite calcium tungstate is well known for their interesting luminescence and structural particularities and therefore has been extensively studied during the past century. Luminescent property of CaW[O.sub.4] powders prepared with aqueous reactions

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Intensifying screens Flashcards Quizlet

reduced patient/operator radiation dose (advantages or rare earth over calcium tungstate screens) 75% reduction w/ 800 speed rare earth system compared to 200 speed tungstate system. T/F magnification radiography benefits from smaller focal spot sizes. T.

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US Patent for X-Ray image intensifying screens comprising ...

Suited X-ray image intensifying screens of the present invention contain in one screen layer in addition to the non-phosphor substance(s) that yield hydroxyl ions in aqueous medium calcium tungstate phosphor particles and rare-earth oxyhalide phosphor particles in a

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Clinical comparison of high-speed rare-earth screen and ...

One hundred patients underwent excretory urography and a comparison was made of ten-minute, well-collimated images that were obtained with both par-speed and rare-earth screens, the latter being 6.5 times faster than the par-speed calcium tungstate screens. Radiation dose was greatly reduced with the rare-earth screens.

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Screen Radiography - AAPM HQ

1896: Paper used for media -based radiography. Calcium tungstate intensifying screens discovered. Relative speeds unknown (VERY low). 1912: Glass plate radiography. VERY low speed. 1918 -1970s: Double emulsion films, calcium tungstate screens improved, relative system speeds 25 -200. 1970s – present: Rare earth screens and appropriate films

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Intensifying Screens - Quia

Screen Speed Classifications. Intensification factor. Related to the conversion efficiency of the phosphor. Descriptive rating. Par speed, high speed etc. Screen Speed Classifications. Relative-speed number. Par speed = 100 RS. High speed = 200 – 1200 RS. Fine/detail = 20 – 80 RS. Beam Absorption. Calcium tungstate. Absorb 20 – 40% of the ...

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Rare earth screens and silver

Compared toconventional calcium tungstate intensify-ingscreens, rareearth screens havethedisadvantages ofhigher cost and unfamiliar exposure characteristics. Buttheyhaveimportant advantages aswell:theirability toreduce radiation exposure hasbeenemphasized [1], while their potential toconserve silver hasbeenlargely ignored.

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Tungsten Recycling in the United States in 2000

Tungsten Recycling in the United States in 2000 By Kim B. Shedd ... referred to as “white ore,” is calcium tungstate (CaWO: 4). Wolframite, which is sometimes referred to as “black ore,” is the name for a mineral and the mineral group to which it belongs. The wolframite group is a solid solution series of

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Calcium tungstate screens Article about calcium ...

Calcium is produced industrially by two methods: (1) by heating a briquetted mixture of CaO and powdered aluminum at 1200°C in a vacuum of 0.01-0.02 mm Hg; the calcium vapors, evolved according to the equation 6CaO + 2A1 = 3CaO ⋅ A1 2 O 3 + 3Ca, condense on a cold surface; (2) by electrolyzing a melt of CaCl 2 and KCl, using a liquid copper ...

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Rare earth screens for panoramic radiography - ScienceDirect

Apr 01, 1984  The radiographs produced by the faster rare earth screen/film combinations were found to be similar in quality to those produced by calcium tungstate screens. Rare earth screens could be used for panoramic radiography while maintaining quality and

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Calcium Tungstate - Rubamin

Calcium Tungstate. Chemistry books will describe calcium tungstate as a compound that contains an oxoanion of tungsten. Technically, all useful tungsten ores are tungstates and most of these tend to occur along with molybdates.

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Intensifying Screens - Quia

Screen Speed Classifications. Intensification factor. Related to the conversion efficiency of the phosphor. Descriptive rating. Par speed, high speed etc. Screen Speed Classifications. Relative-speed number. Par speed = 100 RS. High speed = 200 – 1200 RS. Fine/detail = 20 – 80 RS. Beam Absorption. Calcium tungstate. Absorb 20 – 40% of the ...

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Rare-earth screens versus calcium tungstate screens ...

Plain radiography with a rare-earth screen: comparison with calcium tungstate screen. Picus D, McAlister WH, Smith E, Rodewald S, Jost RG, Evens RG. AJR Am J Roentgenol, 143(6):1335-1338, 01 Dec 1984 Cited by: 3 articles PMID: 6333800

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US Patent for X-Ray image intensifying screens comprising ...

Suited X-ray image intensifying screens of the present invention contain in one screen layer in addition to the non-phosphor substance(s) that yield hydroxyl ions in aqueous medium calcium tungstate phosphor particles and rare-earth oxyhalide phosphor particles in a

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Calcium tungstate phosphor and radiographic intensifying ...

The present invention relates to a calcium tungstate phosphor. Such a calcium tungstate phosphor is known from US-A-3 940 347 on which the preamble of claim 1 is based. The calcium tungstate phosphor of the invention exhibits an emission of high luminance under X-ray excitation and a

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Intensifying screen avinesh shrestha - SlideShare

Apr 08, 2016  Although Ca tungstate seldom are used anymore, they serve as the basis for comparison of all other screens. Par speed Ca tungstate-100 High speed rare earth screens-1200 Detail screens-50 to 80 The image detail or the visibility of detail combines the quantitative measures of spatial resolution and contrast resolution.

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X-Ray Exposure Reduction Using Rare-Earth Oxysulfide ...

Oct 01, 1972  Despite this disadvantage, gadolinium oxysulfide screens allow a significant x-ray exposure reduction relative to calcium tungstate screens providing equivalent resolution. An additional exposure reduction is anticipated when faster green-sensitive x-ray film becomes available. Article History Published in print: Oct 1972.

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Calcium tungstate CaWO4 - PubChem

Calcium tungstate. MFCD00010913. Calcium tungsten oxide. Calcium Tungstate Powder. Ca.WO4

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Energy absorbed in calcium tungstate x‐ray screens ...

Energy absorbed in calcium tungstate x‐ray screens. Ralph E. Shuping. Medical Physics Branch, Division of Electronic Products, Bureau of Radiological Health, Food and Drug Administration, Rockville, Maryland 20817. Search for more papers by this author. Philip F. Judy.

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Intensifying screens films - SlideShare

Apr 12, 2015  6 intensifying screens what is an intensifying screen? -it’s a part of cassette -converts x ray energy into visible light spectrum. history: •first developed by thomas edison in 1897 •initial screens used cawo4 advantages: •reduces x ray dose to the pateint •short exposure times- reduced motion blur 6.

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