14 Darkrooms – Still Necessary? Darkrooms are necessary for manually fed processorsAnd daylight processors.-Loading automatic (daylight) film processor magazines.Necessary for conducting certain quality control tests (daily sensitometric strip).To check consistency of processing
15 Darkrooms 4 Basic Functions Number 1 FunctionStorageUnexposed film
17 Darkroom Contents Loading Bench Film Bin Film I.D. Printer Safelights Pass BoxLight-tight RoomAmple ventilationWarning Light outside roomLockable DoorWall Shielding if adjacent to x-ray roomWalls painted with light color to reflect safelight
20 Purpose of Film Processing DARKROOM FUNCTION # 2Purpose of 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.
33 Basic Recommendations Now done by Processor Co. Follow mfg. recommendations:-strength of chemicals-temperature of chemicals-time requirements in each chemicalSolutions should be replenished as necessary & changed regularlySolutions must be monitored (Daily QC strip).
34 CHEMICAL FOG strength of chemicals in DEVELOPER DILUTE – Under Processed (light films)OXIDIZED - over processed (films dark)temperature of chemicalsToo Hot - films darktime requirements in each chemicalToo long in tanks – films dark
39 Processor Chemistry Overview Developer – converts latent image into manifest imageFixer – clear the film of unexposed, undeveloped silver bromide crystals, promotes archival qualityWash – rid the film of residual chemicalsDry - sets the film for handling
40 Developer Solution (6 Ingredients) Reducing Agent: reduce exposed silver halide to black metallic silver-Hydroquinone (Blacks) SLOW-Phenidone (Grays) FAST(Metol or Elon)2. Activator: softens gelatin, maintains alkaline pH (increase pH)-Sodium Carbonate
41 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
42 Developer Solution5. Restrainer: prevents chemical fog in new developer – antifogging agent-Potassium Bromide(In starter solution)6. Solvent: dissolves & ionizes the developer chemicals-Water
43 Fixer Solution (5 Ingredients) Clearing Agent: dissolves /removesundeveloped silver halide crystals-Ammonium Thiosulfate(Fixer retention – film turns brown if not washed off)Activator: stops reduction, acidic pHACETIC ACID
44 FIXER SOLUTION Hardener: harden emulsion POTASSIUM ALUM (if films come out “sticky” this is depleted – it is not because of the dry not drying the films)4. Preservative - maintains pH levelsSODIUM SULFITE5. Solvent: dissolves chemicals
45 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
47 Transport System Components Feed TrayRollers (Different Assemblies):1. Entrance2. Deep Racks3. Turnaround4. Crossover5. Squeegee6. DryerReceiving Bin
48 Transport System (Rollers) EntranceCrossoverFeed TraySqueegeeDeep RacksDryerTurnaround
49 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 edgeCrosswise not lenghtwise (except 8x10) to not use up extra replensher
50 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
52 Temperature Regulation Main function: To control the temperature of each section of the processor.Developer – most important solution to regulateUsually between 92 degrees and 95 degreesThermostatically controlledWater circulation helps to control temp – if water is not turned on – processor temp will rise
53 Recirculation SystemProvides agitation necessary for uniform solution concentration
54 Wash & Dryer SystemsWash: Provide thorough removal of chemical solutions from the film.-Archival film qualityDryer: Removes water from film by blowing warm, dry air-Between 120 degrees & 130 degrees F.
57 ARTIFACTS – An unwanted density on a film can appear as a dark or light mark on the film (image)Caused by: Improper: Handling, Processing or Storage
58 Artifact are undesirable an unwanted density on film is the term for markings or images that appear on the finished film that did not result from the attenuation of the x-ray beam passing through the patient.They may appear because of poor conditions related to the film, mishandling, or processing problems.Artifacts can cause an image to be misinterpreted, can make interpretation difficult or impossible (as in the images shown in the illustration), and may require a repeat procedure resulting in unnecessary additional patient exposure.
59 Different kinds of artifacts can occur, but virtually all can be prevented. Fog artifacts can be caused by high temperatures, bright light, high humidity, or ionizing radiation. Scratches or pressure on the film can cause white or dark areas. Poor contact between the screen and film can cause localized blurring or darker areas. Dirt on the screen or film can cause white spots. Damaged cassettes or screens can cause a range of artifacts, as can improperly functioning automatic processors. Shown in the illustration are films marred by a variety of artifacts. Only by following accepted and safe procedures for handling and storing film, and for processing exposed film, can artifacts be prevented.
92 Silver RecoveryAbout 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.
93 SILVER RECOVERY –Photography consumes approximately 30% of the worlds sliver - half of this is used in diagnostic imaging films3 reasons for Diagnostic Imaging Department to use silver recovery:1. Dwindling worldwide supply of silver2. $$ cash for silver ( school’s processing services donated for silver recovery)(About 10% of the films cost is recovered through silver recover)3. State and Federal pollution regulationsOne of the functions of the fixer solution is to remove the unexposed and undeveloped silver halide crystals from the film. These crystals are eliminated with the used fixer by the replenishment system.The dissolved silver averages about 50% of the silver that was originally on the film.
95 Three methods of recovery: 1. Metallic Replacement - Steel wool inside a canister collects the silver (most useful type of recovery for low volume processors)2. Electrolytic - cells pass an electric current through a cylinder, causing silver to be plated onto the cathode cylinder of the unit. Silver is removed by scraping it off the cathode. (For medium to high volume)3. Chemical Precipitation - (oldest form) Chemicals cause a separation of the silver form the fixer. The silver sinks to the bottom and forms a sludge where it can be removed. (This is the least desirable way - hazardous chemicals used with toxic fumes) ( Only used by very large institutions)SILVER RECOVERY FROM FILM:
96 Green film - contains most of the silver (should be separated from other film) this film is worth more than developed filmScrap Film & Archival Film - Silver can be removed by burning the film and removing silver from the ashes, or using chemical treatments.Usually paid on a price per pound of film
97 There are three types of silver recovery systems: metallic replacement units, electrolytic units, and chemical precipitation units. In metallic replacement units, the used fixer circulates through a tank in which iron molecules in steel screens break down and are replaced by metallic silver precipitates. This method is less efficient than other methods and is less commonly used. In electrolytic units, such as the one shown in the illustration, an electric current is passed through the fixer; ionized silver molecules in the fixer are attracted to, and form a plating on, the negatively-charged rotating cathode. Other units use a process of chemical precipitation in which other chemicals react with the silver in the fixer solution. Silver molecules are freed and precipitate out of the solution, falling to the bottom of the tank where they can be recovered from the silver sludge that forms.
98 silver recovery.A final consideration in film processing is silver recovery. This term is the process by which silver in the processing chemicals is reclaimed and recycled by a unit, such as the one shown in the illustration. This recycling is important for two reasons. Silver has economic value in its recycled form and helps recover some of the cost of the unexposed film, which is expensive, in part, because of the silver in it. Secondly, federal regulations require that heavy metals like silver be reclaimed from waste solutions before they are disposed of, to prevent pollution of the environment. Roughly half the silver in the film ends up dissolved in the fixer in the automatic processor. Different kinds of silver recovery units are used to process the used fixer to recover the silver.
99 First, the film is fed into the unit through a feed tray in a conventional unit or directly from the cassette in daylight systems. The film first enters the developer tank. The developer solution gives up electrons that neutralize the positively charged silver ions in the film in a process called reduction. The chemical in the developer solution responsible for this is called the reducing agent. Metallic silver builds up in visible black specks at the sensitivity specks. Other chemicals in the developer help control this process precisely and prevent overexposure. A hardener also prevents the film emulsion from becoming too soft or swollen during the processing. To obtain the best visible image, the development process depends on precise control of the concentration and temperature of the developer, as well as the length of time the film is in the developer. All these are controlled automatically by the film processor.
100 Why does x-ray film come out black? There are five possible reasons:The film is overexposured (exposures are too long or the setting is too high).The processing times are too long.The temperature is too warm.The film has been exposed to another light source.The safelight lens (filter) is cracked or damaged.
106 Film Sizes Standard “inches”: 8” x 10” 10” x 12” 11” x 14” 14” x 17” Metric:18cm x 24cm24cm x 30cm30cm x 35cm35cm x 43cm
107 X-Ray Film Film is a media that makes a permanent record of the image. Image recorded on film is caused by exposure to energy:-X-ray energy converted to light energy-Image before processing= Latent image-Made visible by chemical processing
108 X-ray Film cont’d Radiographic film is/was most common image receptor Two parts:1. Base2. Emulsion
109 Film Construction Made of a polyester plastic Must be clear, strong, consistent thicknessTinted pale blue or blue-gray (reduces eye strain)Photographic emulsion can be on one side or both sides of base (single emulsion / double emulsion)Protective overcoat layered on top of emulsion
110 FILM COMPOSTION SINGLE OR DOUBLE EMULSION EMULSION : GELATIN COATED ON A BASEEMULSION : GELATINWITH SILVER HALIDE CRYSTALSBASE: SUPPORTPOLYESTER
112 Film EmulsionMade of mixture of gelatin & silver halide crystals (fluorine, chlorine, bromine, & iodine)Most x-ray film emulsions made of :silver bromide (90%) silver iodide (10%)Photographically active layer – activated by light & radiation to create image
117 Film CharacteristicsSize of silver halide crystals & emulsion thickness determine speed of film and degree of resolutionLarger crystals / thicker crystal layer=Faster response, less detail, less exposure (chest x-ray)Finer crystals / thinner crystal layer=Slower response, greater detail, more exposure (extremity)
127 Spectral SensitivityFilm is designed to be sensitive to the color of light emitted by the intensifying screens.Blue LIGHT– Conventional Calcium Tungstate screenGreen, Yellow-Green LIGHT– Rare Earth screen
128 Cassettes Cassettes serve 3 important functions: Protect film from exposure to lightProtect film from bending and scratching during use.Contain intensifying screens, keeps film in close contact to screen during exposure.
129 CASSETTE or FILM HOLDER The CASSETTE is used to hold the film during examinations. It consist of front and back intensifying screens, and has a lead (Pb) backing. The cassette is light tight
130 Cassette Features - Front Exposure side of cassette is the “front”.Has the ID blocker (patient identification)Made of radiolucent material – easily penetrated by x-rays, lightweight metal alloy or plastic material made of resin.Intensifying screen mounted to inside of front.
132 Cassette Features - Back Back made of metal or plasticInside back is a layer of lead foil – prevents backscatter that could fog the filmInside foil layer is a layer of padding – maintains good film/screen contactBack intensifying screen mounted on padding
133 Intensifying ScreensFlat surface coated with fluorescent crystals called phosphors that glow, giving off light when exposed to x-rays.
134 Intensifying Screens Reduce patient exposure Increase x-ray tube life Direct x-ray exposure to film requires 25 to 400 times more radiation than film/screen.Two advantages to using intensifying screens:Reduce patient exposureIncrease x-ray tube life
135 Screen Construction Polyester plastic base – support layer Phosphor layer – active layerReflective layer – increases screen efficiency by redirecting light headed in other directionsProtective coating
136 Phosphor Layer Active layer – x-ray photons converted to light photons *Photoelectric EffectType must correlate with film:-Calcium Tungstate = blue to purple light-Rare Earth = green & ultraviolet lightNAMES 3 ?
137 Rare Earth Screens Gadolinium Lanthanum Yttrium Found in low abundance in nature
174 Densitometer Reads on a scale of 0-4 0 meaning that all light is transmitted4 meaning that no light transmits through the filmTypical diagnostic densities range between 0.25 to 2.5
175 Parts of the Curve Base + fog Toe-Dmin Straight line portion Where the density becomes lightStraight line portionUsed to demonstrate the relationship to the film’s exposure vs. the density transmitted
176 Parts of the CurveShoulder-DmaxWhere the density becomes dark
177 Film Properties Base density Fog Density Inherent in a piece of film due to dyes etc.Value is usually 0.1 ODFog DensityInadvertent exposure during storage handling etc.Fog density should not exceed 0.2 OD
178 Base + Fog Cannot separate base and fog density measurements Typical range of OD for Base + fog0.18 to 0.23Should not exceed 0.25
179 Toe Dmin Controlled by phenidone Fast acting reducing agent in developerProduces gray tones on film
180 Straight Line Portion Area of curve between toe and shoulder Contains range of useful densitiesTypically 0.25 – 2.5 or 3.0
181 Shoulder Dmax Controlled by hydroquinone Slow acting reducing agent in developerProduces blacks in image
182 Reversal or Solarization Once a film has been exposed to Dmax, it will begin to lose density after further exposureDuplication film has been solarized
183 Film CharacteristicsResolutionSpeedContrastLatitude
184 Resolution Ability to accurately image an object AKA Detail Sharpness DefinitionResolving power
185 ResolutionInversely related to size of silver halide crystals
186 SpeedAbility of an IR to respond to low exposure measures its sensitivity or speedSpeed indexSpecified by base + fog
187 SpeedFaster film will have a curve closer to y-axis of graph
188 Speed Film sensitivity is affected by: Size of silver halide crystalsNumber of sensitivity specksThickness of the emulsionAll of the above are directly related to film speed
189 Speed Affected by processing Immersion time Solution temperature Chemical activity