some special imaging process
TRANSCRIPT
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1- Xeroradiography2- Copying Radiography3- Subtraction
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Xerography An image-recoding process in which the
sensitive material is a plate carrying an electrical charge on its surface. When light falls on the surface the charge is released. The plate is dusted with a special powder and image is formed by the powder being attracted and retained in charged area.
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1- XeroradographyXeroradiography is not a process requiring
any specialized x-ray equipment; it is only a different method of recording an x-ray image.
It depends upon the photoconductive behaviour of a selenium plate and substitutes a photoelectric process for photochemical one associated with the use of a film.
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Photoelectric and photochemical responses
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Selenium Plate Is an insulator in the dark, become
conductive when exposed to light or x-ray.If the plate is given a superficial electric
charge, it is capable of remaining of retaining this charge for a period of hours.
In charged condition, expos of the plate to light or x-rays effect conduction in exposed area.
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1- conditioner
Two machines are necessary for xergraphy
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The main features of the conditionerA – a storage box containing xergraphic plate.B, C- a plate (B) passes form storage box
through a small oven (C) which removes any residual charge; the plate then to storage elevator (D).
E- insertion of an empty cassette initiates the charging process.
F- an ionizing device which charges the surface of the plate after it leaves the storage elevator and before it enters the open cassette.
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2- processor
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•I – a rotating brush which cleans the plate before H- a third ionizing device which loosens any powder remaining on the plate after transfer.it enters a storage box.
•J – the paper passes through an oven (J) which fuses the power image to the paper
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The main features of the processor for xergraphyA- the cassette containing the exposed plate.B- the plate is transported to a development
chamber, where developer powder (toner) is sprayed on its surface.
C- D paper is removed from the paper tray (C) to a position (D) for contact with powder plate.
F- an ion- emitting device, the effect of which is to loosen the powder on the plate, preparatory to its transfer.
G- another ionizing device which gives the reverse side of the paper a charge of opposite polarity.
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Xeroradiograph of female breast
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Copying RadiographTo copy radiograph is produce a second from
the first;It may be Smaller in size than the first (miniaturized)The same size (facsimiles)large in size (enlargement)
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Duplicate film (copy film):
Is single emulsion film that is exposed to ultraviolet light or blue light through existing radiograph to produce a copy.
Duplicate film is direct positive film.
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Used in angiography, although with the increasing application of digital fluoroscopy, its use is declining.
Subtraction film single emulsion, and there are generally two types;
(a) One type to prepare the subtraction mask.(b) One to accommodates the superimposed
image of the original radiograph and subtraction mask.
Subtraction film has high contrast to enhance existing subject contrast
Subtraction film
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conventional subtraction
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The plain film
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The subtraction mask.
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The angiogram
The subtraction mask
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The plain film
The subtraction mask
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The angiogram
The subtracted image
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Digital subtraction angiography
Coronary artery
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Digital imaging technology (cont)
The technique of digital subtraction angiography (DSA), based on digital image processing, allows enhanced visualization of blood vessels by electronically subtracting unwanted parts of the image.
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Thank you