Processing the Latent Image Dr Mohamed El Safwany, MD.

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

Purpose of Conventional Film Processing  Change 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 Sequence  Wetting  Developing  Rinsing in stop bath  Fixing  Washing  Drying

Manual Feed Processor

Hand Processing in the Early years Strong smell of chemicals Messy Time comsuming

1956 – first roller transport 6 minute processing time

Processing Time 3 minutes 90 seconds

Processing Film Table top Processors TABLE TOP PROCESSOR Can process as fast as 60 seconds

Daylight Processor

AUTOMATIC PROCESSING  TRANSPORTATION SYSTEM  DEVELOPER  FIXER  WASHER  DRYER  REPLENISHMENT SYSTEM

PROCSSING CHEMICALS  Solutions are PRE- MIXED  Outside Company usually provides service- Weekly or monthly Weekly or monthly  Solutions should be replenished as necessary & changed regularly  Solutions must be monitored (Daily QC strip).

Automatic Processor

Processor Chemistry Overview Developer – converts latent image into manifest image Fixer – clear the film of unexposed, undeveloped silver bromide crystals, promotes archival quality Wash – rid the film of residual chemicals

First Step Wetting the film to swell the emulsion

Developer Solution (6 Ingredients) 1.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 Solution 3. Hardener: prevents damage to the film from over swelling of gelatin in automatic processors. -Gluteraldehyde 4. Preservative: Antioxidant that prevents oxidation of developer -Sodium Sulfite

Developer Solution 5. Restrainer: prevents chemical fog protects crystals from chemicals -Potassium Bromide 6. Solvent: dissolves & ionizes the developer chemicals -Water

Fixing  Once 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) 1.Clearing Agent: dissolves undeveloped silver halide -Ammonium Thiosulfate 2. Tanning Agent: shrinks, hardens, preserves emulsion -Aluminum Salt

Fixer Solution 3. Activator: neutralizes developer, maintains acidic pH (decrease pH) -Acetic Acid 4. Preservative: prevents oxidation, prolongs solution life -Sodium Sulfite 5. Solvent: dissolves other ingredients -Water

Wash Rid the film of residual chemicals Residual 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 Systems Wash: Provide thorough removal of chemical solutions from the film. Dryer: Removes water from film by blowing warm, dry air

Transport System in Automatic Processors Conveys 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 Components Feed Tray Rollers (Different Assemblies): 1. Entrance 2. Deep Racks 3. Turnaround 4. Crossover 5. Squeegee 6. Dryer Receiving Bin

Transport System (Rollers) Turnaround Entrance Deep Racks Crossover Squeegee Dryer Feed Tray

 Engages 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 System Main function: Keep solution tanks full and assure proper solution concentration. As film is introduced into processor, sensor initiates solution replenishment Right & 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 regulate Thermostatically controlled

Silver Recovery About ½ of the film’s silver remains in the emulsion after exposure & processing. Other ½ (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 Storage Clean, dry location 40 – 60 % Humidity 70 º Fahrenheit Away from chemical fumes Safe from radiation exposure Standing on edge Expiration date clearly visible

Safe Light 15 Watts Red filter Must be 3-6 feet from counter top or feed tray of processor Used to be amber or orange filter

Film Identification Pt name Exam date & time Pt x-ray number Pt Birthday/DOB Rt or Lt marker Optional –Exam type –Dr. Name

FILM ID PRINTER Name of patient place on top Cassette is “flashed” with name – can be done before or after image is taken Must be done BEFORE PROCESSING FILM

TABLE TOP FILM DUPLICATOR to MAKE COPIES OF FILMS

Digital Image Printing Dry processing – no chemistry No darkroom Less environmental impact Reduce costs

Dry Processing  Uses a laser to form a latent image and heat to process the image  Two types: Photothermography (PTG) Uses a laser to record the image signal (latent image) then film is heated to produce the manifest image Photothermography (PTG) Uses a laser to record the image signal (latent image) then film is heated to produce the manifest image Thermography (TG) Uses modulated heat source to produce the image directly Thermography (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 Processing  One 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 Storage  Digital radiographs, and other digital medical images, are stored as digital data.  Advantages (compared to images recorded on film) include: Rapid storage and retrieval Rapid storage and retrieval Less physical storage space required Less physical storage space required Ability to copy and duplicate without loss of image quality Ability to copy and duplicate without loss of image quality

Communications Network  Another 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 Within the imaging facility to the storage and display devices To other locations (Teleradiology) To other locations (Teleradiology) Anywhere in the world (by means of the internet) 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.

Assignment  Two students will be selected for assignments.

Suggested Readings  Clark’s Radiographic Positioning  David Sutton’s Radiology.

Questions  Identify Processing Sequences?

 Thank You