Processing the Latent Processing the Latent ImageImage

Dr Mohamed El Safwany, MD.Dr Mohamed El Safwany, MD.

Intended Learning OutcomesIntended Learning Outcomes

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

Purpose of Conventional Purpose of Conventional Film ProcessingFilm Processing

Change silver halide crystals from film Change silver halide crystals from film emulsion (after exposure to x-ray or light emulsion (after exposure to x-ray or light

photons) to black metallic silver.photons) to black metallic silver. Latent imageLatent image (invisible until processed) is (invisible until processed) is

developed into a developed into a Manifest image.Manifest image. Improper or careless processing can Improper or careless processing can

cause poor diagnostic quality.cause poor diagnostic quality.

Processing SequenceProcessing Sequence

WettingWetting

DevelopingDeveloping

Rinsing in stop bathRinsing in stop bath

FixingFixing

WashingWashing

DryingDrying

Manual Feed ProcessorManual Feed Processor

Hand Processing in the Early yearsHand Processing in the Early years

•Strong smell of chemicals

•Messy

•Time comsuming

1956 – first roller transport1956 – first roller transport6 minute processing time6 minute processing time

Processing TimeProcessing Time

3 minutes 90 seconds3 minutes 90 seconds

Processing FilmProcessing FilmTable top ProcessorsTable top Processors

TABLE TOP PROCESSOR

Can process as fast as 60 seconds

Daylight ProcessorDaylight Processor

AUTOMATIC PROCESSINGAUTOMATIC PROCESSING

TRANSPORTATION TRANSPORTATION SYSTEMSYSTEM

DEVELOPERDEVELOPER

FIXERFIXER

WASHERWASHER

DRYERDRYER

REPLENISHMENT REPLENISHMENT SYSTEMSYSTEM

PROCSSING CHEMICALSPROCSSING CHEMICALS Solutions are PRE- MIXEDSolutions are PRE- MIXED Outside Company usually provides service- Outside Company usually provides service-

Weekly or monthlyWeekly or monthly Solutions should be Solutions should be replenishedreplenished as as

necessary & changed regularlynecessary & changed regularly Solutions must be monitored (Daily QC Solutions must be monitored (Daily QC

strip).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

FixingFixing

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

FixingFixing

First step of fixing is the stop bath – to First step of fixing is the stop bath – to stop the developer chemicalsstop 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 Acid4. 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 Racks3. Turnaround4. Crossover5. Squeegee6. Dryer

• Receiving Bin

Transport System (Rollers)

Turnaround

Entrance

Deep Racks

Crossover

Squeegee

Dryer

Feed Tray

Feed TrayFeed Tray

Engages a micro switch to start the Engages a micro switch to start the replenishment system.replenishment system.

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

Short side of film against the side rail for Short side of film against the side rail for proper replenishment.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 PRINTERName 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 DUPLICATORto MAKE COPIES OF FILMS

Digital Image Printing

• Dry processing – no chemistry

• No darkroom

• Less environmental impact

• Reduce costs

Dry ProcessingDry Processing

Uses a laser to form a latent image and Uses a laser to form a latent image and heat to process the imageheat to process the image

Two types:Two types: Photothermography (PTG) Uses a laser to Photothermography (PTG) Uses a laser to

record the image signal (latent image) then record the image signal (latent image) then film is heated to produce the manifest imagefilm is heated to produce the manifest image

Thermography (TG) Uses modulated heat Thermography (TG) Uses modulated heat source to produce the image directly source to produce the image directly

The Digital ReceptorThe Digital Receptor

The digital receptor is the device that intercepts The digital receptor is the device that intercepts the x-ray beam after it has passed through the the x-ray beam after it has passed through the patients body and produces an image in digital patients body and produces an image in digital form, that is, a matrix of pixels, each with a form, that is, a matrix of pixels, each with a numerical value. numerical value.

This replaces the cassette containing This replaces the cassette containing intensifying screens and film that is used in non-intensifying screens and film that is used in non-digital, film-screen radiography.digital, film-screen radiography.

There are several different types of digital There are several different types of digital radiography receptors.radiography receptors.

Image ProcessingImage Processing One of the major advantages of digital One of the major advantages of digital

radiography is the ability to process the images radiography is the ability to process the images after they are recorded. after they are recorded.

Various forms of digital processing can be Various forms of digital processing can be used to change the characteristics of the digital used to change the characteristics of the digital images.images.

For digital radiographs the ability to change For digital radiographs the ability to change and optimize the contrast is of great value.and optimize the contrast is of great value.

It is also possible to use digital processing to It is also possible to use digital processing to enhance visibility of detail in some radiographs.enhance visibility of detail in some radiographs.

Digital Image StorageDigital Image Storage

Digital radiographs, and other digital medical Digital radiographs, and other digital medical images, are stored as digital data.images, are stored as digital data.

Advantages (compared to images recorded on Advantages (compared to images recorded on film) include:film) include: Rapid storage and retrievalRapid storage and retrieval Less physical storage space requiredLess physical storage space required Ability to copy and duplicate without loss of image Ability to copy and duplicate without loss of image

qualityquality

Communications NetworkCommunications Network

Another advantage of digital images is the Another advantage of digital images is the ability to transfer them from one location to ability to transfer them from one location to another very rapidly. another very rapidly.

This can be:This can be: Within the imaging facility to the storage and Within the imaging facility to the storage and

display devices 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 The total network available for transferring digital images is made up of a variety of digital images is made up of a variety of integrated systemsintegrated systems

The Advantages:-

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

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

AssignmentAssignment

Two students will be selected for Two students will be selected for assignments.assignments.

Suggested ReadingsSuggested Readings

Clark’s Radiographic PositioningClark’s Radiographic Positioning David Sutton’s Radiology.David Sutton’s Radiology.

QuestionsQuestions

Identify Processing Sequences?Identify Processing Sequences?

Thank YouThank You