Processing the Latent ImageDr Mohamed El Safwany, MD.

Intended Learning OutcomesThe student should be able to understand principles of radiological image processing at the end of this lecture.

Purpose of Conventional Film ProcessingChange silver halide crystals from film emulsion (after exposure to x-ray or light photons) to black metallic silver.Latent image (invisible until processed) is developed into a Manifest image.Improper or careless processing can cause poor diagnostic quality.

Processing SequenceWetting

Developing

Rinsing in stop bath

Fixing

Washing

Drying

Manual Feed Processor

Hand Processing in the Early yearsStrong smell of chemicalsMessy Time comsuming

1956 first roller transport6 minute processing time

Processing Time3 minutes 90 seconds

Processing FilmTable top ProcessorsTABLE TOP PROCESSORCan process as fast as 60 seconds

Daylight Processor

AUTOMATIC PROCESSINGTRANSPORTATION SYSTEM

DEVELOPER

FIXER

WASHER

DRYER

REPLENISHMENT SYSTEM

PROCSSING CHEMICALSSolutions are PRE- MIXEDOutside Company usually provides service- Weekly or monthlySolutions should be replenished as necessary & changed regularlySolutions must be monitored (Daily QC strip).

Automatic Processor

Processor Chemistry OverviewDeveloper converts latent image into manifest image

Fixer clear the film of unexposed, undeveloped silver bromide crystals, promotes archival qualityWash rid the film of residual chemicals

First Step Wetting the film to swell the emulsion

Developer Solution(6 Ingredients)Reducing Agent: reduce exposed silver halide to black metallic silver-Hydroquinone (Blacks)-Phenidone (Grays)2. Activator: softens gelatin, maintains alkaline pH (increase pH)-Sodium Carbonate

Developer Solution3. Hardener: prevents damage to the film from over swelling of gelatin in automatic processors.-Gluteraldehyde4. Preservative: Antioxidant that prevents oxidation of developer-Sodium Sulfite

Developer Solution5. Restrainer: prevents chemical fog protects crystals from chemicals-Potassium Bromide6. Solvent: dissolves & ionizes the developer chemicals-Water

FixingOnce development is complete, the film must be treated so that the image will not fade but will remain permanently.

Fixing

First step of fixing is the stop bath to stop the developer chemicals

Fixer Solution(5 Ingredients)Clearing Agent: dissolves undeveloped silver halide-Ammonium Thiosulfate2. Tanning Agent: shrinks, hardens, preserves emulsion-Aluminum Salt

Fixer Solution3. Activator: neutralizes developer, maintains acidic pH (decrease pH)-Acetic Acid4. Preservative: prevents oxidation, prolongs solution life-Sodium Sulfite5. Solvent: dissolves other ingredients-Water

WashRid the film of residual chemicalsResidual chemicals on the film will discolor radiograph over time.Cold water processors are less efficient in removing chemicals Warm water processors much better.Agitation during wash process is essential

Fixer or Hypo Retention(Not Washed Off)

Wash & Dryer SystemsWash: Provide thorough removal of chemical solutions from the film.

Dryer: Removes water from film by blowing warm, dry air

Transport System in Automatic ProcessorsConveys the film through different solutions (sections) by a series of rollers driven by gears, chains & sprockets.

Done at a prescribed speed determines length of time the film is in each solution

Transport System ComponentsFeed TrayRollers (Different Assemblies):1. Entrance 2. Deep Racks3. Turnaround4. Crossover5. Squeegee6. DryerReceiving Bin

Transport System (Rollers)TurnaroundEntrance

Deep RacksCrossoverSqueegeeDryerFeed Tray

Feed TrayEngages a micro switch to start the replenishment system.

Always feed the film evenly, using the side rails of the feed tray. Alternate sides from film to film.

Short side of film against the side rail for proper replenishment.

Replenishment SystemMain function: Keep solution tanks full and assure proper solution concentration.As film is introduced into processor, sensor initiates solution replenishmentRight & wrong way to feed in film-Feed in along short edge

Replenishment tanks

Temperature Regulation

Main function: To control the temperature of each section of the processor.Developer most important solution to regulateThermostatically controlled

Silver RecoveryAbout of the films silver remains in the emulsion after exposure & processing.Other (unexposed silver) is removed from the film during fixing process.Silver is toxic to public water supply must have proper disposal.

Darkrooms Still Necessary?

Darkrooms are necessary for manually fed processors and daylight processors.-Loading automatic film processor magazines.

Film StorageClean, dry location40 60 % Humidity 70 FahrenheitAway from chemical fumesSafe from radiation exposureStanding on edgeExpiration date clearly visible

Safe Light15 WattsRed filterMust be 3-6 feet from counter top or feed tray of processorUsed to be amber or orange filter

Film IdentificationPt nameExam date & timePt x-ray numberPt Birthday/DOBRt or Lt markerOptionalExam typeDr. Name

FILM ID PRINTERName of patient place on top

Cassette is flashed with name can be done before or after image is taken

Must be done BEFOREPROCESSINGFILM

TABLE TOP FILM DUPLICATORto MAKE COPIES OF FILMS

Digital Image PrintingDry processing no chemistryNo darkroomLess environmental impact Reduce costs

Dry ProcessingUses a laser to form a latent image and heat to process the imageTwo types:Photothermography (PTG) Uses a laser to record the image signal (latent image) then film is heated to produce the manifest imageThermography (TG) Uses modulated heat source to produce the image directly

The Digital Receptor The digital receptor is the device that intercepts the x-ray beam after it has passed through the patients body and produces an image in digital form, that is, a matrix of pixels, each with a numerical value. This replaces the cassette containing intensifying screens and film that is used in non-digital, film-screen radiography.There are several different types of digital radiography receptors.

Image ProcessingOne of the major advantages of digital radiography is the ability to process the images after they are recorded. Various forms of digital processing can be used to change the characteristics of the digital images.For digital radiographs the ability to change and optimize the contrast is of great value.It is also possible to use digital processing to enhance visibility of detail in some radiographs.

Digital Image StorageDigital radiographs, and other digital medical images, are stored as digital data.Advantages (compared to images recorded on film) include:Rapid storage and retrievalLess physical storage space requiredAbility to copy and duplicate without loss of image quality

Communications NetworkAnother advantage of digital images is the ability to transfer them from one location to another very rapidly. This can be:Within the imaging facility to the storage and display devices To other locations (Teleradiology)Anywhere in the world (by means of the internet) The total network available for transferring digital images is made up of a variety of integrated systems

The Advantages:- Minimal Space demand.Reduces radiation dose.Facility of post-processing. Simultaneous availability of image.Cost savings.Enhanced teaching and research opportunity.

Cost savings:-Elimination of films.Elimination of chemical and processors.Reduction in maintenance cost.Less requirement of staff.Reduction in space.

AssignmentTwo students will be selected for assignments.

Suggested ReadingsClarks Radiographic PositioningDavid Suttons Radiology.

QuestionsIdentify Processing Sequences?

Thank You

The Advantages*The Advantages*