RAD 354 Chapt 11 Radiographic Film/Receptor Image forming rays: remnant beam/exit radiation – scattered radiation (partially absorbed/attenuated) and non-interacting.

RAD 354 Chapt 11Radiographic Film/Receptor

• Image forming rays: remnant beam/exit radiation – scattered radiation (partially absorbed/attenuated) and non-interacting

X-ray beam

RAD Film – 2 main parts: emulsion and base

• Base: rigid, non-shrinking base to support the emulsion – now made of plyester

• Emulsion: Silver halide and gelatin. 98% is silver bromide, the rest is usually silver iodide

Latent Image

• Produced when the exit beam (remnant beam) exists the patient and interacts with the emulsion/image receptor

• Takes place at the sensitivity spec (center) due to liberated charges traveling in the development center (spec or receptor)

Film/Receptor Types

• Digital – – Computed Radiography (CR) = Photostimulable

Phosphor (PSP)– Direct Radiography (DR/DDR) = Solid State X-ray

Detector (SSXD)

– Film: Screen, Direct Exposure, Mammo, Laser, Duplication, Spot Film, Subtraction and Cine

Direct Exposure

• Non-screen film – sensitive to x-rays– Like “bite wings” at the dentist

Screen Film – sensitive to both light and radiation

• Comes in a variety of contrast, latitude, spee and light color sensitivity– Larger silver halide crystals = faster speed and

LESS DETAIL– Thick emulsion layer = faster speed and LESS

DETAIL– Double emulsion layer – faster speed – prone to

“CROSSOVER”

COLOR SENSITIVITY

• Spectral matching = matching the color spectrum of light given off by screens to that of the emulsion– Calcium Tungstate Crystals (atomic #’s 60/70’s)– Rare Earth – AMU’s mainly in the 50’s (57-71)– Orthochromatic = green sensitive film– Panchromatic = sensitive to all color (photographic

film)– Laser = sensitive to red light

Other type films

• Mammo/routine films = some mammo is single emulsion and single screen film and some double/double

• Duplicating film – single emulsion, solaraized film

• Cine = Dynamic motion (heart caths, etc.) 35mm

• Spot film camera film = 70mm, 105mm

Darkroom Safelights

• Filter is spectral matched to filter out the light spectrum the film is SENSITIVE to (wratten 6-B = red safelight filter)

• Usually 15 watt bulb• Should be no closer than 5 feet from work

surface (some “feed trays” have a safelight that turns on after the film has progressed into the processor and out when a film begins to enter the processor)

Film Storage

• Boxes to be stored on end – NEVER flat!• 68F (20C) best at 50F (1-C) AND low humidity

(40% or LESS)• Unexposed film is MUCH less sensitive to light,

radiation, chemicals, heat, etc., than EXPOSED FILM!

• Shelf life – limited (film begins to develop as soon as it is made)

RAD 354 Chapt. 12 Processing the LATENT Image

• Basics / Dates:– Universal time and temp: 5 min. @ 68 F– Each MAJOR step is 2X longer than the previous

(manual processing)• 1942 = First “Automatic Processor by Pako

(some 20 ft. long and required film to be placed on “hanger racks” for transport)

• 1956 – First “ROLLER” transport processor by Kodak (5 minute)

Basics/dates, con’t.

• 1965 = First 90 sec. processor by Kodak• 1987 = First 45/90 sec variable processor by

Konica

• Development = conversion of latent image to manifest image (black metallic silver)

• Fixation– Removes the UNEXPOSED and Undeveloped silver

halide crystals– PRESERVES the MANIFEST (visible) image

90 Sec. Processor Items of Importance

• Time for devel and fix = 22 seconds for EACH• Developing/Reducing agents: Hydroquinone,

phenidone/ metol/ elan• Fixing agents: Acetic acid, ammonium

thiosulfate

Developing Agents

• Hydroquinone – SLOW acting build up of “blackest blacks” (also know as the reducing agent)

• Phenidone/metol/elan = act RAPIDLY to build up GRAYS

• “Buffering agents” (to maintain alkalinity) = sodium carbonate/sodium hydroxide (Lye)

• Restrainer = “Potass”ium bromide/iodide = prevents UNEXPOSED silver halide conversion to black metallic silver

Developer Con’t.

• Preservative = sodium sulfite• Hardener = Gluteraldehyde/potassium

alum/aluminum chloride/chrome alum

Fixing Agents

• Same hardener and preservatives as devel.• Acetic acid = “activator “- STOPS action of

developer• Ammonium thiosulfate – FIXING AGENT• Acetate – “Buffering agent” – helps maintain

acidic pH

Washing

• Universal solvent = WATER

• “Hypo retention” = residual fixing chemicals on the film– Will turn the film brown over time– MUST BE CHECKED FOR MAMMO!!!

Automatic Processing

• Six total SYSTEMSTransportTemperatureCirculationReplenishmentDryerElectrical

Transport

• Rollers and transport “racks,” drive gears– TRANSPORT ROLLERS are 1” in diameter (3.14”

circum.) “Pi lines” are a common artifact– “Guide shoes” also can cause artifacts (especially

with NEW processors and racks/cross over assemblies

– Cross over rollers/racks– Time guidelines (time spent in devel/fixer) = +/-

2% of required time (22 sec. each in a 90 processor for fix and devel)

5 “Other” systems

• Temperature = proper temps for developer (95F), wash and dryer (110F)

• Circulation = agitates chemicals, FILTERS DEVELOPER

• Replenishment = meters and replaces chemistry (MICROSWITCH on feed tray)

• Dryer = Dries film (know diff. between “wet” and “tacky”

• Electrical = All electrical areas

Other/Special Processing

• Daylight = Enables one to place a cassette/receptor in the daylight processor and the processor opens/processes/reloads cassette/receptor

• Dry Porcessing:– Photothermic – Used laser to form a latent image

and HEAT to make it visible– Thermographic – Uses heat to DIRECTLY produce

the image