the processing of radiographs

8/10/2019 The Processing of Radiographs

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Film processing

Latent image: an invisible image produced in a film emulsion after it has been exposed to the

X-ray beam. It requires exposure to a developer and fixer before the image is visible and

permanent.

Image formation : exposure of the film to the x-ray beam X-ray radiation or forms causes

ionic changes in the silver bromide crystals in the film emulsion so that it acquires a silver

atom. It is the deposition of reduced silver atoms in particles or zones that causes the black

zones or foci on the film. he amount of silver deposited depends on the intensity of the initial

radiation x-ray exposure.

Image intensification : a technique used to increase the brightness of the image !hile

maintaining its sharpness. "sed particularly in fluoroscopy and vie!ing directly or indirectly

through a television camera and monitor# cineradiography# videotape or split-film device.

he processing of radiographs involves a number of chemical reactions and changes#

!hich mu st take place under carefully controlled conditions if a satisfactory

radiograph is to be produced. $uch factors as:%. location and construction of th e processing room

&. good organization of th e materials to be used

'. efficient u se of the room an d th e x-ray specialist(s skills

). satisfactory ad*ustment to adverse environmental conditions

+ust as the military pilot ha s long since ceased to ,fly by the seat of his pants#, th e

profic ient x-ray specialist no longer processes film by means of ,a lit tle bit of this a

little bit of that and !ait (til it looks right., iven properly exposed film a nd

!orkable facilities a nd supplies# t he proficient x-ray specialist can be depended upon

to produce radiographs of a quality a nd uniformity that are desired by th e radiologists.he follo!ing processing of the film are:

eveloper process

/ixer

Developer process

evelopment i s essent ia l ly a chemical r educt ion in !hich s i lver hal ide i s

reduced or conver ted to metal l ic s i lver . here are t!o methods for

developer process are:

0anual developer

1utomat ic developer

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MANUAL DEVELOPER SOLUTION

he chemistry of th e solutions in automatic an d manual processing is basically th e

same. here are a fe ! variations bet!een th e t! o an d these occur in the developer.

2ecause of these variations# th e developer solution !ill be addressed in detail from

both manual and automatic processing. he manual developer solut ion is composed

of four basic agents: an activator# reducers# a restrainer# and a preservative.

3ach of th e agents is mixed !ith !ater# !hich acts as a solvent. 2ecause each of theagents has its o!n specific function# each o ne !ill be dealt !ith in a separate

paragraph.

a.Activator. he activator 4or alkali5# sodium carbonate# softens t he gelatin of t he

emulsion and provides th e necessary alkaline medium to th e solution so that the

reducing agents ca n diffuse into th e emulsion a nd attack th e exposed silver

bromide crystals. In general# the more alkal ine the developer# the more po!erful

and rapid is its action. 1 disadvantage of sodium carbonate is that !hen a film is

processed in an x-ray developer containing it and then transferred to a !arm acid-

fixing bath# tiny bubbles of carbon dioxide gas may form in the soft gelatin. 1s th ebubbles escape# they form tiny craters or pi ts in the emulsion# thereby breaking up

the normal character of the silver image. he finished film or radiograph is blistered.

o overcome this effect# t he temperature of th e developer# rinse# an d fixer solutions

should be approximately t he same.

. Re!"cers.

4%5 6eduction process.the latent image si te is a speck of silver capable of initiating

development. he latent image site provides a place !here the reducers accomplish

th e process of breaking do !n th e silver bromide crystal to black metallic silver. he

reducing agents act as electron donors to the la tent image site# giving it a negativecharge. hu s# th e positively charged silver ions may mo ve into th e areas of th e

sensitivity speck and become attracted to it. 1s this process continues# more silver

ions are attracted a nd deposited as atoms of silver. he final result is the

breakdo!n of the ent ire crysta l to black metall ic silver.

4&5 6educing agents. he agents commonly used are 3lon0 4another trade name is

0e to l 05 and hydroquinone. he activity of these chemicals requires their

presence in an alkal ine solution. 7hemical functions differently in at tacking the

emulsion. he 3lon0 starts development by attacking t he exposed silver bromide

crystals s!iftly !ith resultant production of gray tones in the image. 3lon0 is

unpredictable above 89/ a nd hydroquinone ceases its activity belo! ;


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reducers !ill override the restrainer and chemical fog !ill result. 1lso# th e bromide

released from th e crystals into the solution !ill gradually restrain the action of th e

reducing agents to a point !here t hey no longer function efficiently. herefore# !hen

a replenisher solution is mixed# it should not include th e restrainer.

!.Preservative. he preservative 4sodium sulfate5 retards th e activity of the

reducing agents to !ithin controlled limits so that t he ,life, of th e developing solution

is maintained over a reasonable period of time. $ince the reducing agents reactquickly !ith oxygen# this reaction must be controlled or the developing solution !ill

no t last very long. $odium sulfate !orks very !ell as a preservative because it

retards oxidation of t he reducing agents an d prevents th e formation of stains on th e

film.AUTOMATI# DEVELOPER SOLUTION

2ecause of th e increased speed an d temperatures used for automatic processing# the

chemicals used in th e manual developer are not adequate. herefore# although th e

functions of th e chemicals are basically the same# some of th e chemicals used are

different. he automatic developer consists of five chemicals: an activator# reducers #a restrainer# a preservative# a nd a hardener.

a.Activator. he activator is the same chemical 4potassium hydroxide5 used in

manual developer solution an d it serves th e same purpose. It s!ells and softens t he

emulsion so that th e reducing agents ca n enter an d act upo n t he silver bromide

crystals. It also provides th e necessary alkaline medium for th e solution.

.Re!"cer. he reducer 4phenidone and hydroquinone5 reduces th e exposed silver

bromide crystal to black metall ic silver. 3lon0# used in manual developing# is

unpredictable above 89/ and is replaced by phenidone in automatic processors.

=henidone# !hich functions effectively at temperatures of >


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FI&ER SOLUTION

1lthough the concentration of th e fixer solution varies for th e t !o methods of

processing# the chemicals used are basical ly the same. he fixer has four chemical

agents: an acidifier# a clearing agent# a hardener# and a preservative. 1ll of the

chemicals are mixed !ith !ater# !hich serves as the solvent.

a.Aci!i%ier. he acidifier 4acetic acid5 neutralizes any alkaline developer that may be

carried over from th e developing solution and provides t he required acidity for th eother chemicals to function. he acidifying action quickly stops development and

prevents formation of stains.

. #learing Agent. he clearing agent 4sodium thiosulfate or ammonium thiosulfate5

dissolves the residual unexposed silver bromide crystals in th e emulsion !ithout

damage to the silver image. he unexposed crystals h av e of course# been unchanged

by the developer. If t he fi lm is not properly cleared# t he remaining unexposed silver

bromide crystals !il l darken on exposure to light a nd obscure the radiographic

image. hese chemicals are commonly kno!n as ,hypo., he clearing action of

hy po involves a chemical reaction bet!een th e sodium or ammonium thiosulfatean d t he silver bromide in th e emulsion# !herein silver thiosulfate is formed an d

remains in solution.

c.$ar!ener. he hardening agent 4platinum alum# chrome alum# or aluminum

chloride5 decreases the possibility of physical in*ury to th e gelatin emulsion. 1

s!ollen emulsion is easily scratched or distorted during the !ashing an d drying

process. he hardener restrains s!el ling of the gelatin and hardens it so that it can

!ithstand the normal effects of processing.

!.Preservative. he preservative 4sodium sulfite5 prevents decomposition of th e

clearing agent by th e acid !ith a resultant precipitation of sulfur# as long as normaldeveloping temperatures are maintained. It assists in clearing the film and prevents

th e residual developer carried over in th e film from oxidizing an d discoloring the

fixing bath.

Electron micrograp' o% a !evelope! silver romi!e grain.

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the processing of radiographs

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