Film Processing Robert Metzger, Ph.D. Roland Wong, Sc.M

Film Processing

Robert Metzger, Ph.D.

Roland Wong, Sc.M.

Film Emulsion

Film consists of emulsion supported by a thick polyester base.Film consists of emulsion supported by a thick polyester base.

Film emulsion consists of silver halide (95% AgFilm emulsion consists of silver halide (95% Ag++BrBr-- and 5% and 5%

AgAg++II--).).

The silver halide grains can be sensitized by radiation or The silver halide grains can be sensitized by radiation or

light to hold a latent image. light to hold a latent image.

Silver halide grains are about 1 Silver halide grains are about 1 m in diameter and contain m in diameter and contain

between 10between 1066 and 10 and 1077 silver atoms (10 silver atoms (1099 grains per cm grains per cm33). ).

Film Exposure – Latent Image Absorbed light photons liberate electrons in the emulsion, which Absorbed light photons liberate electrons in the emulsion, which

combine with the positively charged silver ions to form a latent combine with the positively charged silver ions to form a latent image of silver (Agimage of silver (Ag++ + e + e- - →→ Ag). Ag).

3 to 5 silver atoms are needed to produce a latent image 3 to 5 silver atoms are needed to produce a latent image

center. center. Few silver atoms along with AgFew silver atoms along with Ag++ ions exist in the emulsion ions exist in the emulsion

after exposure. after exposure. A film that has been exposed but not yet developed is said A film that has been exposed but not yet developed is said

to possess a latent image. to possess a latent image.

Development

Development is a chemical process that converts the invisible latent image Development is a chemical process that converts the invisible latent image to a permanent image. to a permanent image.

During the development process, the latent image center catalyzes the During the development process, the latent image center catalyzes the

reaction, which reduces the remaining silver ions in that silver halide reaction, which reduces the remaining silver ions in that silver halide crystal into a grain of metallic silver. crystal into a grain of metallic silver.

A developed grain results in a speck of silver that appears black on the A developed grain results in a speck of silver that appears black on the

film. film. Darker areas of the film have a higher concentration of grains and Darker areas of the film have a higher concentration of grains and

lighter areas have fewer grains. lighter areas have fewer grains.

Development Each blackened grain contributes very slightly to the optical density Each blackened grain contributes very slightly to the optical density

of the film at that location. of the film at that location.

The unexposed grains with no latent image are washed out of the The unexposed grains with no latent image are washed out of the emulsion. emulsion.

Film speed, contrast, and base and fog levels are all affected by Film speed, contrast, and base and fog levels are all affected by developer chemistry and temperature. developer chemistry and temperature. Increasing the developer temperature or time increases the film Increasing the developer temperature or time increases the film

contrast and density and also fog.contrast and density and also fog.

The Film Processor Developer tank Developer tank

temperature is temperature is typically 35typically 35°°C (95C (95°°C) C) (31-35 range) (31-35 range)

Automatic Automatic replenishment of replenishment of chemicals take place.chemicals take place.

Flooded Flooded replenishment for low replenishment for low film rates.film rates.

Developer is Developer is circulated in a closed circulated in a closed loop to equilibrate loop to equilibrate temperatures.temperatures.

c.f. Bushberg, et al. c.f. Bushberg, et al. The Essential Physics The Essential Physics of Medical Imaging, of Medical Imaging, 22ndnd ed., p. 179. ed., p. 179.

The Film Processor DevelopmentDevelopment

The film is pushed into the entrance rollers, which direct the film The film is pushed into the entrance rollers, which direct the film into the developer tank. into the developer tank.

The developer solution wets the film The developer solution wets the film The activator (sodium hydroxide) expands the emulsion to allow The activator (sodium hydroxide) expands the emulsion to allow

chemical access to halide crystals deep in the emulsion.chemical access to halide crystals deep in the emulsion. Developing agents (hydroquinone / phenidone) reduce the ionic Developing agents (hydroquinone / phenidone) reduce the ionic

silver to free silver. They act as sources of electrons to initiate silver to free silver. They act as sources of electrons to initiate the reaction. the reaction.

Restrainers (KBr / KI) limits development to exposed halide Restrainers (KBr / KI) limits development to exposed halide crystals.crystals.

Hardener (glutaraldehyde) controls the emulsion swelling.Hardener (glutaraldehyde) controls the emulsion swelling. Time in the developer is typically 25 seconds at 92 degrees F for Time in the developer is typically 25 seconds at 92 degrees F for

“Standard” cycle processing.“Standard” cycle processing.


The developing agents (hydroquinone / phenidone) act on The developing agents (hydroquinone / phenidone) act on different areas of exposed halide concentrations. different areas of exposed halide concentrations.

The hydroquinone acts more on the areas of film that have high The hydroquinone acts more on the areas of film that have high concentrations of exposed silver halides. (The linear portion concentrations of exposed silver halides. (The linear portion and shoulder portion of the H&d curve.) and shoulder portion of the H&d curve.)

The phenidone acts more on the areas of film that have low The phenidone acts more on the areas of film that have low concentrations of exposed silver halides. (The toe of the H&D concentrations of exposed silver halides. (The toe of the H&D curve.)curve.)


Preservative helps prevent the developer solution from Preservative helps prevent the developer solution from oxidation with atmospheric oxygen. oxidation with atmospheric oxygen.

The released bromides and halides temper the chemical activity The released bromides and halides temper the chemical activity of the developer solution. of the developer solution.

A dynamic equilibrium is established to maintain a constant A dynamic equilibrium is established to maintain a constant chemical activity of the developer solution. The solution is said chemical activity of the developer solution. The solution is said to be aged.to be aged.

As the various agents in the solution are used, the developer As the various agents in the solution are used, the developer solution is replenished by pumping in new solution. solution is replenished by pumping in new solution.

Fresh chemistry is artificially aged by the addition of “Starter” Fresh chemistry is artificially aged by the addition of “Starter” solution.solution.

Starter solution is added to replenishment solution for flooded Starter solution is added to replenishment solution for flooded replenishment.replenishment.

The Film Processor Film is squeegeed of developer solution before it is passed on into Film is squeegeed of developer solution before it is passed on into

the fixer tank.the fixer tank. Fixing Fixing

The fixer is acidic (acetic acid) which stops the development The fixer is acidic (acetic acid) which stops the development reactions. reactions.

Fixing stabilizes the image against further sensitivity to light.Fixing stabilizes the image against further sensitivity to light. Fixing removes unexposed silver halide atoms.Fixing removes unexposed silver halide atoms. Inadequate fixing can lead to milky residue in the film emulsion. Fixer is replenished by the same timing cycle.

Fixer time: typically 21 seconds.Fixer time: typically 21 seconds.

The Film Processor Film is squeegeed before being put into the wash tank.Film is squeegeed before being put into the wash tank. Washing Washing

The water bath simply washes residual chemicals out of the film The water bath simply washes residual chemicals out of the film emulsion emulsion

Incomplete removal of the fixer causes the film to turn brown Incomplete removal of the fixer causes the film to turn brown

Drying Drying A thermostatically regulated coil heats air blown from a powerful A thermostatically regulated coil heats air blown from a powerful

fan, and this warm air blows across both surfaces of the film fan, and this warm air blows across both surfaces of the film

The whole process will typically take 90 seconds (developer time, The whole process will typically take 90 seconds (developer time,

25 seconds, fixer time, 21 seconds, washing & drying is 44 25 seconds, fixer time, 21 seconds, washing & drying is 44 seconds)seconds)

Processor Artifacts Overdevelopment Overdevelopment

Concentration of Concentration of developer too high developer too high

Primarily affects the Primarily affects the low OD part of the low OD part of the curve where silver curve where silver halide crystals not halide crystals not exposed to light exposed to light become developedbecome developed

c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 181. ed., p. 181.

Processor Artifacts Underdevelopment Underdevelopment

Concentration of Concentration of developer too low or developer too low or

If the temperature of If the temperature of developer too low developer too low

Reduction in OD at Reduction in OD at high exposure end high exposure end

Curve will appear flat Curve will appear flat and lack contrast and lack contrast


Artifacts

See slides 16-23 for See slides 16-23 for explanation of artifacts explanation of artifacts

Water spots Water spots Slap line Slap line Pick-off Pick-off Wet pressure marks Wet pressure marks Shoe marks Shoe marks Runback Runback Chatter Chatter


Artifacts

Shadow images: typically Shadow images: typically caused by dust between caused by dust between the film and the screen. the film and the screen. Appearance is that of Appearance is that of small, clear areas of the small, clear areas of the film.film.

Seen only on single Seen only on single emulsion films. Artifact that emulsion films. Artifact that occurs most often. occurs most often.


Artifacts

Shadow images: typically Shadow images: typically caused by dust between caused by dust between the film and the screen. the film and the screen. Appearance is that of Appearance is that of small, clear areas of the small, clear areas of the film.film.

Seen only on single Seen only on single emulsion films. Artifact that emulsion films. Artifact that occurs most often. occurs most often.


Artifacts

Pick-off artifacts are small, Pick-off artifacts are small, clear areas of the film clear areas of the film where emulsion has where emulsion has flecked off from the film flecked off from the film base.base.

Can be confused with dust Can be confused with dust artifact. artifact.

Can be caused by rough Can be caused by rough rollers, non-uniform film rollers, non-uniform film transport, or a mismatch transport, or a mismatch between the film emulsion between the film emulsion and chemicals and chemicals


Artifacts

Pick-off artifacts are small, Pick-off artifacts are small, clear areas of the film clear areas of the film where emulsion has flecked where emulsion has flecked off from the film base.off from the film base.

Often confused with dust Often confused with dust artifact.artifact.

Can be caused by rough Can be caused by rough rollers, non-uniform film rollers, non-uniform film transport, or a mismatch transport, or a mismatch between the film emulsion between the film emulsion and chemicals.and chemicals.


Artifacts

Wet pressure marks occur Wet pressure marks occur When the pinch rollers When the pinch rollers

apply too much or apply too much or inconsistent pressure to inconsistent pressure to the film in the developer the film in the developer or or

in the developer-to-fixer in the developer-to-fixer crossover racks crossover racks


Artifacts

Wet pressure marks occur Wet pressure marks occur When the pinch rollers When the pinch rollers

apply too much or apply too much or inconsistent pressure to inconsistent pressure to the film in the developer the film in the developer or or

in the developer-to-fixer in the developer-to-fixer crossover racks crossover racks


Artifacts Chatter is a periodic set Chatter is a periodic set

of lines perpendicular to of lines perpendicular to the film transport the film transport direction that is caused direction that is caused by binding of the roller by binding of the roller assembly in the assembly in the developer tank or developer tank or

in the developer-to-fixer in the developer-to-fixer crossover assembly crossover assembly

Static discharge will Static discharge will show up black on the show up black on the film film


Artifacts Chatter is a periodic set Chatter is a periodic set

of lines perpendicular to of lines perpendicular to the film transport the film transport direction that is caused direction that is caused by binding of the roller by binding of the roller assembly in the assembly in the developer tank or developer tank or

in the developer-to-fixer in the developer-to-fixer crossover assembly crossover assembly

Static discharge will Static discharge will show up black on the show up black on the film film


Artifacts

A slap line is a plus-A slap line is a plus-density line perpendicular density line perpendicular to the direction of film to the direction of film travel that occurs near the travel that occurs near the trailing edge of the film trailing edge of the film

This is caused by the This is caused by the abrupt release of the back abrupt release of the back edge of the film as it edge of the film as it passes through the passes through the developer-to-fixer developer-to-fixer crossover assembly crossover assembly


Artifacts

A slap line is a plus-A slap line is a plus-density line perpendicular density line perpendicular to the direction of film to the direction of film travel that occurs near the travel that occurs near the trailing edge of the film trailing edge of the film

This is caused by the This is caused by the abrupt release of the back abrupt release of the back edge of the film as it edge of the film as it passes through the passes through the developer-to-fixer developer-to-fixer crossover assembly crossover assembly


Artifacts Guide shoe marks result Guide shoe marks result

When the film rubs When the film rubs against the guide shoes against the guide shoes during transport during transport

The artifact manifests as The artifact manifests as a series of evenly a series of evenly spaced lines parallel to spaced lines parallel to the direction of film the direction of film transport transport

Plus-density shoe marks Plus-density shoe marks caused by the guide caused by the guide shoes in the developer shoes in the developer tank tank


Artifacts

Guide shoe marks result Guide shoe marks result Minus-density shoe Minus-density shoe

marks occur in the fixer-marks occur in the fixer-to-washer crossover to-washer crossover

If emulsion surface If emulsion surface damage is present, the damage is present, the problem can be problem can be anywhere along the anywhere along the transport path transport path


Artifacts

Guide shoe marksGuide shoe marks


Artifacts Runback artifacts look like Runback artifacts look like

fluid drips and occur at the fluid drips and occur at the trailing edge of a film trailing edge of a film when developer from the when developer from the

film surface not film surface not removed, as the film removed, as the film descends into the fixer descends into the fixer the excess developer the excess developer “runs back” at the trailing “runs back” at the trailing edge of film edge of film

Developer on the Developer on the developer-to-fixer developer-to-fixer crossover assembly crossover assembly becomes oxidized and becomes oxidized and can cause this artifact can cause this artifact


Artifacts Runback artifactsRunback artifacts when developer from when developer from

the film surface not the film surface not removed, as the film removed, as the film descends into the fixer descends into the fixer the excess developer the excess developer “runs back” at the “runs back” at the trailing edge of filmtrailing edge of film


Artifacts Flame artifact looks like a Flame artifact looks like a

gas flame when the film is gas flame when the film is oriented with the direction of oriented with the direction of travel horizontal.travel horizontal. when developer is re-when developer is re-

circulated through the circulated through the fixer and wash tanks, it fixer and wash tanks, it picks up heat and is picks up heat and is more chemically active. more chemically active.

When the solution is When the solution is squirted back into the squirted back into the developer tank, onto the developer tank, onto the film, then the more active film, then the more active solution will develop the solution will develop the film more, differentially. film more, differentially.


Other Considerations

Rapid processing Rapid processing Standard film process in radiology requires 90 Standard film process in radiology requires 90

seconds to process the film.seconds to process the film. In some areas like ER, a 45-sec processor time In some areas like ER, a 45-sec processor time

can be achieved. can be achieved. Activity of developer solution increased by Activity of developer solution increased by

increasing concentration of solution or by increasing concentration of solution or by increasing the solution temperature or both. increasing the solution temperature or both.

Typically, the processor temperature is increased Typically, the processor temperature is increased to about 38to about 38°°C (100C (100°°F) for a 45-second process.F) for a 45-second process.

Other Considerations Extended or push processing is the act of Extended or push processing is the act of

slowing down the film transport, typically slowing down the film transport, typically increasing the transport time to 120 increasing the transport time to 120 seconds.seconds.

Increases the speed of the film and Increases the speed of the film and reduces dose to the patient. reduces dose to the patient.

Was used in mammography .Was used in mammography . Daylight processors Daylight processors

Automatic unloading/loading film Automatic unloading/loading film systems connected to a film processorsystems connected to a film processor


Laser Cameras & Imagers

Typically used to produce films from CT and MRI.Typically used to produce films from CT and MRI. Use digital images as the source.Use digital images as the source. Light in the laser beam exposes the film.Light in the laser beam exposes the film.


Dry Processing Used for producing images from digital modalities such as MRI, Used for producing images from digital modalities such as MRI,

CT, Ultrasound and digital radiography.CT, Ultrasound and digital radiography.

No plumbing required, no chemical vats which produce fumes No plumbing required, no chemical vats which produce fumes

and less chemical waste.and less chemical waste.

Cost per sheet of film is higher compared to wet processing Cost per sheet of film is higher compared to wet processing

systems.systems.

Dry Processing One dry system makes use of carbon instead of silver grains to One dry system makes use of carbon instead of silver grains to

produce density on the film (adherographic) produce density on the film (adherographic) Raw film consists of a imaging layer and a laser-sensitive Raw film consists of a imaging layer and a laser-sensitive

adhesive layer, sandwiched between 2 polyester sheets adhesive layer, sandwiched between 2 polyester sheets The imaging layer is a matrix of carbon particles and polymer The imaging layer is a matrix of carbon particles and polymer Laser energy focused at the laser-sensitive adhesive layer Laser energy focused at the laser-sensitive adhesive layer Thermal sensitization by laser causes adhesion of the carbon Thermal sensitization by laser causes adhesion of the carbon

layer to the polyester film base layer to the polyester film base After laser exposure, the two outer polyester layers are After laser exposure, the two outer polyester layers are

separated, producing a positive and negative image separated, producing a positive and negative image The positive image is coated with a protective layer and becomes The positive image is coated with a protective layer and becomes

the readable film and the negative image is discarded the readable film and the negative image is discarded All these steps performed in a laser camera and finished film pops All these steps performed in a laser camera and finished film pops

out of the system out of the system

Processor Quality Control Quality control of film processors is Quality control of film processors is

required for mammography per required for mammography per MQSA and is a standard of practice MQSA and is a standard of practice that is scrutinized by the Joint that is scrutinized by the Joint Commission on the Accreditation of Commission on the Accreditation of Health Organizations (JCAHO) and Health Organizations (JCAHO) and regulatory bodies regulatory bodies

A sensitometer and densitometer A sensitometer and densitometer are neededare needed

Sensitometry


Quality Assurance Program

Base + Fog Base + Fog OD measured anywhere on the film away from OD measured anywhere on the film away from

exposed steps, usually <0.2.exposed steps, usually <0.2. Affected by film storage, developer temperature, Affected by film storage, developer temperature,

chemistry.chemistry. Mid-density (Speed) Mid-density (Speed)

Step corresponding to an OD of about 1.0 + base Step corresponding to an OD of about 1.0 + base + fog.+ fog.

Density Difference (Contrast) Density Difference (Contrast) Contrast index is the difference in OD between Contrast index is the difference in OD between

two of the steps near the mid-gray region of the two of the steps near the mid-gray region of the stepped exposures. stepped exposures.

QC Chart

QC Chart

Documents

Film Processing Robert Metzger, Ph.D. Roland Wong, Sc.M