Film Image Characteristics Processing Radiology Chapter 7,8,9 Film Image Characteristics Processing

Dental X-ray Film What is X-ray Film Photographic film that has been adapted for dental use Photographic image – produced when exposed to x-rays

Film Composition Film Base – actual film Emphasize contrast of image Flexible plastic Withstands: Heat, moisture, chemical exposure Transparent with blue tint: Emphasize contrast of image Enhance image quality Purpose of film base: provide support for the emulsion

Film Composition Cont. Adhesive layer Thin layer of adhesive material Covers both sides of film base Attaches the emulsion to the base – allows emulsion to adhere

Film Composition Cont. Film emulsion Coating attached to both sides of film base Gives film greater sensitivity to x-radiation – shortens exposure time

Film emulsion Made of: Gelatin Used to suspend and evenly disperse silver halide crystals over the film base It absorbs processing solutions and allows the chemicals to react with silver halide crystals RHS – may ask what type of material is in emulsion – silver halide or silver bromide

Film emulsion cont. Made of: Silver halide crystals Silver bromide and silver iodide Absorb radiation during x-ray exposure and store energy from the radiation Small crystals require more radiation (better resolution) Large crystals require less radiation

Film Composition Cont. Protective layer Thin layer over emulsion to protect film during handling

Latent Image Formation Silver halide crystals absorb x-radiation during exposure and stores energy from radiation Energy is stored at different levels based on density of objects exposed Stored energy within silver halide crystals form a pattern & creates an invisible image within emulsion of exposed film – latent image

Latent Image Formation Cont. Denser object – more energy absorbed by object – lighter it appears on film Film positioned behind amalgam restoration receives almost no radiation Amalgam is dense & absorbs x-ray energy Silver halide crystals are not energized – fall off film leaving area opaque Appear white on film

Latent Image Formation Cont. Less dense objects appear darker on film Correspond to airspace Little or no density (tissue, sinus, carious tissue) Film receives more radiation Silver halide crystals are highly energized

Types of Films Intraoral film Placed INSIDE the mouth Used to examine teeth & supporting structures Film packet: Soft vinyl Protects film from light and saliva

Types of Films Intraoral film Labeled with: Type of film Film speed Film size Amount per packet (single or double) Expiration date

Types of Films Intraoral film Black paper Lead foil – behind film Shields from light Lead foil – behind film “herringbone or tire track” effect – may appear lighter Blocks radiation – helps with fogging Protects from some scatter radiation

Types of Films Intraoral film: Small raised bump Identification dot Small raised bump Raised bump on solid white side of film – faces PID On one corner of film Placed in slot of bite block – makes dot go – Toward the occlusal/incisal surface of teeth

Types of Intraoral Exposures Periapical – PA Entire tooth 2 – 3 mm around end of root PDL & Lamina Dura Bitewing – BWX Examine interproximal – cavities – usually taken once a year – maybe taken twice depending on Pt Crowns – Max & Man occl. – bone & gum height

Types of Intraoral Exposures Occlusal - #4 film – usually on children Film size 0 – children, referred to as Pedo Film 1 – anterior adult – pedo 2 – Standard (most common) 3 – posterior (BW, longer narrower than #2) 4 - occlusal

Film Speed Refers to the amount of radiation to produce a radiograph A speed (slowest) to F speed (fastest) Only D speed film and E speed film are used for intraoral radiography E speed requires one-half the exposure time of D speed – has comparable image contrast & resolution (less radiation for patient) F speed requires one-third the exposure time of E speed film

Extraoral Film = 2-4 PA’s Placed outside mouth during exposure Used to examine large areas of skull or jaws More sensitive to light/radiation than intraoral film Films are placed in a cassette with intensifying screens Intensifying screens step up/accelerate radiation – reducing amount to pt

Extraoral Film Panoramic Film aka Pano aka Panorex Shows wide view of Max & Man – teeth 15% larger Radiation level for a pano equivalent approx 4 PA’s Used for TMJ or wisdom teeth

Extraoral Film Cephalometric Film aka Ceph Shows bony & soft tissue areas of facial profile Side profile – TMJ, spine, neck, skull, Used for ortho to measure growth

Duplicating Film Makes identical copy of a film Used for insurance claims or transferring patients

Chapter 8 DIAGNOSTIC Ideal radiograph is neither too light or too dark A diagnostic radiograph is: Clear – crisp, clear image, like analog TV vs. HD TV Undistorted Low Contrast – many varying shades of gray

HIGH QUALITY FILMS To fully understand why things appear dark or light on film we need to examine the characteristics of the objects RHS – KNOWING WHETHER YOU ARE DESCRIBING THE OBJECT OR OBJECT AS IT APPEARS ON THE FILM IS CRUCIAL TO YOUR UNDERSTANDING QUESTIONS ON RHS EXAM

TRANSLUCENT Objects that allow light to pass through easily Windows / glass Air When related to dentistry and radiographic film it would be termed radiolucent

RADIOLUCENT Dark allows more x-rays to pass through Portion of processed film that is dark or black Silver Halide Crystals are energized Structure that lacks density & allows x-ray to pass with little or no resistance Structures do not appear or if they do they are quite dark, even black, ex.: air space, gingiva, mucosa, tongue, cheek

OPAQUE Objects that do not allow light to pass through them easily Wall Rocks Metals When related to dentistry and radiographic film it would be termed Radiopaque

RADIOPAQUE Portion of a processed film that is light or white Silver Halide Crystals have NOT been energized Structures are dense & absorb or resist the passage of the x-ray The more dense or thick the structure the lighter it appears, ex.: enamel, bone, amalgam, restorative metals

GEOMETRIC CHARACTERISTICS Problems that can occur on film Deals with size & shape of the image (tooth) as it appears on the film Includes three characteristics: Sharpness Magnification Distortion

SHARPNESS Refers to the clarity of the image Detail, resolution, & definition How crisp and sharp a picture Seen by the amount of silver halide crystals Small crystals but lots of them = better resolution yet requires more radiation to the patient

SHARPNESS Penumbra When image on the radiograph looks fuzzy or blurry Caused by movement of patient or PID Clarity is not as good in F speed films but are good enough to diagnose FYI – sharpness is one factor that is usually outside the control of the DA

MAGNIFICATION When image of the object appears larger than actual size Very important in Endodontics Influencing factors include: Target to film distance – Source of x-rays to film 16” PID = less image magnification 8” PID = more image magnification

MAGNIFICATION Influencing factors include cont.: Object to film distance – tooth to film Closer the film is to the tooth the less image enlargement there will be on the film One area where bisecting the angle is better – will have more magnification w/paralleling technique

DISTORTION Shape & Size of object Any variation in the shape of an image on film Caused by improper angulation of the PID or improper film alignment

IMPROPER ANGULATION Improper Horizontal Angulation Can result in “fat images” The angle of x-ray beam (left to right) Causes overlapping Mesial of one tooth on the distal of another PID should be at a 90 degree angle to film

IMPROPER ANGULATION Improper Vertical angulation Results in either (short) Foreshortening or (long) Elongation Foreshortening Angulation is to steep Too positive Excessive vertical angulation Image produced is shorter than its actual size

IMPROPER ANGULATION Elongation Angulation is to low Too negative Insufficient vertical angulation Image produced is longer that it’s actual size

STEPWEDGE Stepwedge: Aluminum of varied thickness Used to check short and long scale contrast Placed on top of film – Expose Absorbs varying amounts of x-rays Different densities & contrasts will appear – Ch.10

Chapter 9 DENTAL X-RAY PROCESSING Film Processing – converting a latent image (invisible) on the film into a visible image and preserving it permanently Latent Image – Invisible pattern Silver halide crystals absorb x-ray Energy is stored & forms an invisible image Pattern not seen until developed

REDUCTION Reduction: During processing a chemical reaction occurs and halide portion of exposed silver halide crystal are removed Selective Reduction Exposed or energized Silver Halide Crystals become black metallic silver– stay on film (behind radiolucent structures) Unexposed or un-energized Silver Halide Crystals are removed from film – fall off film (behind radiopaque structures)

DEVELOPER Developer – Black bottle, Black lid, Black label First solution to touch dental radiograph Temperate determines total time it takes to complete x-ray Creates the dark or black areas Softens emulsion – so picture will appear

DEVELOPER CONTAINS Hydroquinone Elon Creates the black tones & sharp contrast Temperature sensitive Inactive below 60 degrees Very active above 80 degrees Elon Acts quickly to produce visible image

DEVELOPER CONTAINS Preservatives Accelerators Restrainer Prevent solution from oxidizing in the - Accelerators Activates solution Soften Restrainer Potassium bromide Stops development of both exposed & unexposed silver halide crystals

FIXER Red bottle, red lid, red label Removes the unexposed silver halide crystals Silver stays in fixer making it TOXIC Creates the white or light areas on dental radiograph Black metallic silver is not removed & remains on film Films can be left in the fixer for an indefinite time without any effect on film

FIXER Films cannot be left in developer or water Approximately 2 minutes in fixer the film may be viewed in light Ingredients include: Fixing agent – removes or clears all unexposed & undeveloped silver halide crystals from emulsions

FIXER Cont. Ingredients include: Preservative – prevents chemical deterioration of the fixing agent Hardening agent – harden & shrink the gelatin in the film emulsion after it has been softened by accelerator in the developing solution. Acidifier – stops the developing process

5 STEPS TO MANUAL PROCESSING Develop Rinse Fixer Water Wash Drying

5 STEPS TO MANUAL PROCESSING Developer First step in film processing Temp. of developer determines time 68 degrees is optimum temp. for 4 ½ to 5 mins Range 68 – 74 optimun – Check temp. daily Below 60 – react slow & film appears light Above 80 – react fast & film appears dark Warmer solution – shorter time Cooler solution – longer time

5 STEPS TO MANUAL PROCESSING Rinse To remove the developer from the film and stop the development process Usually about 30 seconds Fixer Usually double the time to spend in Fixer If 5 minutes in developer then 10 mins in fix

5 STEPS TO MANUAL PROCESSING Water wash Always for 20 – 30 minutes Removes all excess chemicals from emulsion Drying Hang films on film hanger to Dry

AUTOMATIC PROCESSING Special machine – works through rollers Developer – still the first solution to touch film & optimum temp 80 degrees Fixer – second solution to touch film Rinse – rinses films Dryer – dries films quickly Replenisher pump – automatically replenishes chemicals – maintain adequate freshness, strength & solution levels

Darkroom Provides a completely dark environment where x-ray film can be handled and processed Location & Size Large enough for all equipment and a person Should be at least 16-20 square ft (4x4,4x5) Ventilation system Temperature – approx. 70 degrees – if exceeds 90 film fogging may occur

Darkroom Lighting Should be completely dark – light tight Any visible white light will be bad for film & cause film fogging Safelight Red – orange spectrum Low intensity light (15 watt) or regular white bulb w/light filter GBX2 best with extra-oral film Must be placed a minimum of 4 ft away from working area

Film Storage Film is adversely affected by: To prevent film fog: Heat Humidity Radiation To prevent film fog: Keep film in cool dry place Temp ranges from 50 – 70 degrees Shield from radiation sources Watch expiration date

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