Radiology

Introduction to Radiography

Radiology is a vital tool in veterinary dentistry that can be used to assist in the diagnosis, treatment planning and monitoring of oral disease.  It can be utilized to confirm missing teeth; diagnose diseases, such as periodontal and endodontic conditions; and confirm treatment procedures, such as complete tooth extraction.

Dental radiology in small animal veterinary practice has traditionally been performed using a stationary radiograph machine with a choice of kilo-voltage (kVp), milli-amperes (mA) and time (milliseconds).  It makes use of standard veterinary radiographic film and cassettes.  Whilst these machines, film and cassettes are suitable and reliable for taking radiographs of general veterinary practice cases, they can be cumbersome and difficult to use when taking radiographs of the oral cavity.

This can be improved by introducing dental intra-oral film, which allowed dental radiographs to be taken of all teeth, without superimposition and using an intra-oral radiographic technique.  It can be further improved by purchasing a dental radiograph machine, as well as, a digital sensor.

I found this out first hand when I started working at Sydney University Veterinary Teaching Hospital.  In our practice, I had been privileged with the use of a human dental radiograph machine and intra-oral film.  At SUVTH, we had a traditional stationary machine and film cassettes in the veterinary radiology department and the dental wet-table was in the treatment room, approximately 20 metres apart and through two doorways.  To take a radiograph, the patient had to be transported to the radiology room.  Once we got there, we had to position the patient and the cassette.  Obtaining an intra-oral radiograph without superimposition of the teeth was almost impossible, the standard plate just doesn’t fit into a mouth, especially a feline mouth. It was cumbersome and a great time waster.

We changed this partly by introducing dental intra-oral film, which allowed dental radiographs to be taken of all teeth, without superimposition and using an intra-oral radiographic technique.  We followed this up by purchasing a dental radiograph machine, which changed our whole technique.  In my current hospital, we have a mobile ACTEON XMIND dental radiograph machine adjacent to the dental treatment table, so when a radiograph is required, I place the Acteon Sopix2 sensor in the mouth, pull down the xray tube head, position it next to the patient, and ZAP, a radiograph is produced.  As will be apparent as you read through this module, all of the problems associated with the traditional stationery veterinary radiograph machine and cassette can be overcome by using a mobile dental radiograph machine and intra-oral radiograph film or a digital sensor.

Radiation Physics

X-rays were discovered on November 8, 1895, by Wilhelm Conrad Roentgen, a German physicist.  An x-ray is a type of electromagnetic radiation, produced by electron energy transitions outside the atom nucleus.  X-rays are produced by a cathode and an anode within an x-ray tube when a high-speed electron strikes metal.  The initial step in producing x-rays is passage of an electric current through a filament, termed the cathode.  The electrical current produces heat and allows electrons to separate from and leave the filament.  The number of electrons produced is proportional to the current (mA).

The electrons produced from the cathode are stationary and initially form a cloud around the cathode.  Therefore, in order to get them to strike the anode, termed the target, a voltage differential is applied across the cathode and anode.  The electrons are then attracted towards the positively charged anode, which they strike, and on doing so, produce x-rays.  The energy of the x-rays produced is proportional to the energy of the electrons striking the anode, which is controlled by the voltage (kVp).  The higher the kVp, the faster the electrons strike the anode and the greater the energy of the x-rays produced.  The current and voltage can both be chosen on a standard stationery machine used for veterinary radiology.  On the smaller or older radiograph machines the kVp is often linked to the mA.  On the larger and newer machines, the kVp and mA are separate and can be independently determined.  On a mobile dental radiograph machine the kVp and mA are pre-set, often at 70 kVp and 8 mA respectively.

The electrical current that is supplied to the machine is an alternating type supplied by the power company.  This results in the cathode being positive in relation to the anode on each half cycle.  Thus, the electrical circuit inside the radiographic machine converts the alternating current into direct rectified current, which changes the negative part of the cycle into positive.  This ensures the anode is always positive with relation to the cathode preventing electrons being attracted back to the cathode each half cycle and causing damage to it.  Therefore, a constant stream of electrons, move towards and strike the anode.  As most of the electron energy that strikes the anode results in heat production, anodes are usually made of tungsten, which has a high melting point.  To reduce the heat generated, some machines utilize a rotating anode, effectively increasing the surface area of the target, prevents it from becoming pitted from the constant barrage of electrons, as well as reducing the heat generated.  The site of x-ray production is termed the ‘focal spot’.

Apart from increasing the mA, another way of increasing the number of x-rays produced is to increase the length of time the x-ray tube is energized.  X-rays are only produced when there is a source of electrons striking the anode.  Therefore, increasing the time the x-ray tube is energized, by changing the length of time current is applied to the cathode, produces more electrons and in turn, results in a greater number of x-rays.  To set the time the x-ray tube is energized, a standard machine uses a timer (usually in milliseconds) whilst a mobile dental machine has a control pad with push buttons.

Radiation Safety

The same safety requirements that are recommended when using a standard veterinary radiograph machine should be followed for the dental radiograph machine.  This includes protection against the primary beam, secondary scatter and leakage.  The majority, if not all, patients will be under general anaesthesia and therefore the operator should be able to leave the room.  If this is not possible, then position yourself at least two metres behind the tube head at 135 degrees behind the direction of the primary beam, will result in the minimum exposure to radiation.  Radiation badges, or monitors, should be worn by all persons using the machine.  There are radiation dose standards available from the Department of Human Services in each state in Australia.  Most countries would have similar government organizations.  In Australia, radiation monitor badges are required to be worn by each person taking radiographs.  The badges are sent to the Department of Health every three months and each person receives a letter informing them of the effective dose exposure reading for both the three month period and their overall lifetime.  A license is also required to operate the xray machine in many countries.

Basic Radiographic Equipment Requirements

To produce a radiograph, the necessary equipment includes a radiograph machine, a film and a processor.

Essentially, the two types of radiograph machine include: a standard stationary machine commonly used for veterinary radiographs and a mobile machine commonly used by human dentists.

Broadly speaking there are four types of radiographic film which include: a traditional sheet of radiographic film in standard veterinary size, i.e. 24cm x 30cm and 30cm x 40cm; a non-screen intra-oral dental film manufactured for human dentists; a phosphor plate; and a digital sensor that is able to detect x-rays and using a computer program to convert them into a digital radiographic image.

The processing of the radiograph can be performed manually or automatically.

Manual processing can be performed using wet chemistry within a dark-room (a room which has light blocked from entering it) or in a light proof chamber in daylight (termed a chair-side developer).  These methods require the operator to place the film into tanks containing developer and fixer for a pre-determined time.  The result is a wet film.

Processing can also be performed automatically, using a machine, termed an automatic processor, which still utilizes wet chemistry, but internal rollers to move the film through the developer and fixer bathes at a set rate, and the film produced is dry.

Processing can also be performed using a computer software program that transmit the x-rays detected on a plate or sensor to a radiographic image on a computer screen.

Principle of producing a radiograph

A radiograph is a visible image of the internal contents of an object.  X-ray film is essentially photographic film coated in a light sensitive emulsion containing silver halide crystals.  When the crystals are exposed to x-rays or light, the crystals precipitate as neutral silver deposits, which appear black to the naked eye.  Thus, the number of x-rays that contact the film is directly responsible for the degree of blackness (or black/white/grey) of the film.

The patient’s mouth (tooth/tongue/bone etc.) is placed between the radiograph machine and the radiograph film/sensor.  When the x-rays are produced they exit the machine, travel towards the patient and either pass through or remain within the soft and hard tissues.  The denser a tissue is, the less x-rays will pass through it and contact the film, thus resulting in a whiter image.  The less dense a tissue is, the more x-rays will pass through the tissue and therefore contact the film, resulting in a blacker image.

Veterinary xray generator

On a standard veterinary xray generator, the tube-head can be regarded as being semi-rigid.  Although it can actually move in 3 planes, it is often easier and quicker to position the patient and the film, rather than trying to get the tube-head at the correct angle and distance from the film.  The kVp, mA and time can often be chosen by the operator of a standard machine making the exposures very flexible.

The exposures you require depend on whether you’re using standard cassettes, intra-oral film or a sensor.  Intra-oral film can be used with a standard radiograph machine.  It is ideal to reduce the film-focal distance to 40cm when using intra-oral film, compared to a standard veterinary film-focal distance of 100cm for a standard cassette.  The kVp recommended, but is primarily determined by your own machine is: 65 (small/toy breed dog and cats), 70 (15kg dog), 75 (25kg dog) and 85 (large breed dogs) and a mA of 100. You may need to adjust these figures slightly depending on the type of machine and film you are using.

Dental xray generator

A dental radiograph machine is principally the same as a stationary machine but with a couple of differences.  Firstly, the tube head is much more flexible and can be positioned at any angle quickly and easily without the need to move the patient.  Secondly, there is less flexibility with regard to choosing the kVp, mA and time.

A mobile dental machine has a tube-head that is highly flexible in all three planes, is often attached to an extendable arm, which allows for easy positioning of the machine so that the patient can often remain in dorsal or ventral recumbency.  They have a ‘long’ hollow tube attached to the tube head, called the collimating cone, which encourages parallel x-rays, and ensuring a film-focal distance of approximately 40cm.  The cone minimises x-ray scatter and allows the operator to direct the x-ray beam directly at the area of interest.

Dental xray generator

The tube head showing a long cone (in the red circle) of my current radiograph machine.

Xmind

The Acteon XMind xray generator is available as either a mobile unit or wall mounted.

The kVp and mA are pre-set, therefore the only setting that can be adjusted is the time, which is chosen when the tooth to be radiographed is chosen on the keypad. With the latest machines, individual times are pre-set based on the tooth that is being radiographed and the size of the patient.  The control pad has a diagrammatic picture of teeth: the incisors, canine, premolars and molars represented in an open mouth type view and three figures; a cat; small dog and large dog. The tooth type is chosen, followed by a cat, small dog (<15kg) or large dog.

The veterinary control panel.

The veterinary control panel.

 

Intra-oral radiograph film

Dental radiographic film is similar to photographic film.  It is composed of a flexible transparent polyester sheet coated with a silver halide crystal emulsion in a gelatin matrix.  The emulsion is over-coated with a protective layer to protect it during handling and processing.  Intra-oral film does not use intensifying screens.  Intra-oral films have a raised dot imprinted in the corner on the film and packet.  The film is placed in the mouth with the raised dot facing towards the X-ray tube.  Post-developing, the raised dot can be used to orientate the film and determine where the film was positioned in the patient’s mouth.

Intra-oral film is available in different speeds and sizes.  The speed is directly related to the size of the silver halide crystals.  The larger the crystal size, the faster the film, and thus the decrease in detail of the image produced.  Film speed is designated by a letter.  The most common speed throughout the 1990s was ‘D’ speed, termed ‘ultra-speed’.  In the late 1990s, ‘E’ speed, termed, ‘ekta-speed’ was made available.

Dental film has four main components: the film, an inner paper wrapping, a lead foil and an outer plastic or paper covering.  The sheet of radiographic film, inner wrapper, lead foil are enclosed within the outer plastic envelope to protect them from light and moisture, such as saliva.  Within the envelope the film is covered by a piece of black paper.  There is also a layer of lead foil on the reverse side of the film to reduce x-ray scatter from the deeper tissues, which causes fogging. Each film packet is available with either a single or double sheet of film.  Dental film should be stored in a dry cool place between 10 and 20 degrees Celcius and less than 65% humidity.  They can be stored in the refrigerator to prolong their life.

An opened packet of periapical film

An opened packet of periapical film showing the plastic cover, lead foil, paper cover and film.

An opened packet of occlusal film

An opened packet of occlusal film showing the outer paper cover, inner black cover, lead foil and film.

Intra-oral film is manufactured for human dentistry and is available in many sizes, of which most can be adapted for small animal use.  Film sizes are designated by a number – ‘0’, ‘1’, ‘2’, ‘3’ and ‘4’.  An ‘0’ sized film is the smallest and is thought of as a paediatric size, ‘1’ is slightly larger than ‘0’.  The most common size for cats and small dogs is a ‘2’ or ‘periapical’ size.  A ‘3’ is termed a bite-wing as it has a small tag positioned in the centre of the film envelope, which lies perpendicular to the film. The ‘4’ film, termed ’occlusal’ is the largest film and can be used to take radiographs of multiple teeth simultaneously.

Comparison of intra-oral film sizes 2, 3 and 4

Comparison of intra-oral film sizes 2, 3 and 4

The films may be held in the mouth by closing the occlusion, or with the help of plastic holders, haemostats, rubber bands, or malleable materials (modelling clay/cotton wool).  The relatively technique friendly and low cost films make them an easy addition to any practice, and a necessary one for those practices involved in more advanced dental procedures.  Occlusal films can even be used for radiology of birds, small mammals and appendages of small pets.

Phosphor plates (CR technology)

Phosphor plates are flexible polyester films that  support photostimulable phosphor deposited in a resin on the surface. After the initial exposure, excited electrons in the phosphor material remain ‘trapped’ in centers in the crystal lattice until stimulated by the second illumination. These mobilized electrons release a blue-violet 400 nm luminescence produced in proportion to the number of trapped electrons and thus in proportion to the original X-ray signal. It is then collected enabling the resulting signal to be converted into a digital image. Phosphorus plates are available in many sizes: from 0 to 4, are reusable and quite affordable.

The Acteon PSPix CR machine

 

Digital sensors (DR technology)

Any radiographic machine can be used to take digital films.  A periapical sized sensor is currently available. The sensor is used in exactly the same technique as intra-oral film and picks up x-rays from the radiograph machine.  A computer software program then interprets the densities and converts them into an image that can be viewed on a screen.  This saves time and cost (no need for developer and fixer).  The image can be manipulated in many ways: contrasts, densities, negative/positive – changing black to white and vice versa, the image can be enlarged, rotated and flipped.  The manipulation that is possible is truly amazing, if you have never used digital imaging before.

The Acteon digital sensor uses CMOS + scintillator + optic fibre technology. CMOS is short for Complementary Metal-Oxide Semiconductor. CMOS is an on-board, battery powered semiconductor chip inside computers that stores information. A scintillator is a material that exhibits scintillation — the property of luminescence when excited by ionizing radiation, as such in that it absorbs its energy and re-emits the absorbed energy in the form of light, which can be transformed into an image in the software computer program.

The Acteon DR #2 sensor

The Acteon DR #2 sensor

Film Processing

Standard veterinary film is processed manually in darkroom tanks or using an automatic processor.  Intra-oral dental film can be processed in the same fashion.  Automatic processing can be performed in a specially designed processor for intra-oral films, or they can be taped to a larger ‘leader’ film and put through the standard veterinary automatic processor.  Occasionally the film will appear underdeveloped though, due to the lower temperature of the chemicals or the less time the film is in contact with them.  Tape can be purchased from Kodak (Pakor Tape).  If normal sticking tape is used, it usually allows the intra-oral film to separate from the leader film.  Manual processing can be performed by sequentially dipping the film into developer, water, fixer and then finally rinsing in water.  The developer, water and fixer can be placed in tanks or smaller pots in the standard dark room.

The most cost effective method is to place 4 containers with developer, initial water wash, fixer and final water wash in the standard darkroom.  The containers should be 5cm diameter and 10 cm tall.  The film is removed from the envelope, placed onto a metal clip and consecutively placed in the containers starting with the developer and progressing to the water for a wash, fixing for 5 minutes and finally in the water for a wash prior to examination, similar to the way veterinarians would process a standard film, but this time in smaller containers.

Intra-oral film can be processed in the chair-side processor using rapid developer and fixer in under two minutes.  The chair-side developer contains 4 containers – one developer, one fixer and two water washes that can be visualised through the see-through lid.  The film packet is placed in the chair-side processor, the operator’s hands are pushed through the holes in the front of the processor and the film packet is opened and the film placed on a metal film clip/hanger.

Internal view of the chair-side processor unit

Internal view of the chair-side processor unit with the four containers – D = developer, WI = initial water wash, F = fixer, WF = final water wash.  Note the metal clip/hangers (black arrow) hanging from the bar that is used to place the film into the containers.

Radiographic film and metal clip used for processing film

Radiographic film and metal clip used for processing film.

After immersing the film in water for five seconds to hydrate the emulsion, the film is placed in the developer with initial agitation for 15-60 seconds (depending on the temperature and solution).  Following a water rinse, the film is then placed in the fixer solution with intermittent agitation for approximately one minute.  It is then possible to remove the film from the chair-side processor for viewing.   The film packet is opened

The film packet is opened (in the darkness of the container with the lid closed, in this picture the lid is open for demonstration purposes).

The film is exposed from the packet

The film is exposed from the packet.

The film is attached to the clip and removed from the packet

The film is attached to the clip and removed from the packet.

The film and clip and ready for processing

The film and clip and ready for processing

Once a diagnosis has been made, the film should be fixed for a further 4 minutes if the film is to be kept.  After fixing, the film needs to be thoroughly rinsed in a circulating water bath or under the tap for 5 minutes otherwise a slimy fixer residue will remain on the film and discolour it.  Kodak Rapid Developer and Fixer is best used were available. Films may be dried and stored in cardboard or plastic mounts, or stored in dental envelopes.  The developer oxidizes rapidly and needs to be changed every few days, depending on your caseload.

Rapid developer and fixer from Kodak

Rapid developer and fixer from Kodak

A dry processed film attached to the metal hanger clip adjacent to the storage envelope on a viewing light box.

A dry processed film attached to the metal hanger clip adjacent to the storage envelope on a viewing light box.

Radiographic Techniques and Positioning

Size ‘2’ periapical intra-oral film may be used to radiograph all feline teeth; and incisors, premolars and molar teeth of small dog’s on a single view. In large breed dogs the canine tooth may need the crown and root to be radiographed separately. Size ‘3’ bite-wing intra-oral film can be used for radiographing canine teeth. Size ‘4’ occlusal intra-oral film can be used for radiographing both mandibular and maxillary incisal areas and for canine teeth. One of the major issues that arise with #4 films is superimposition, elongation or shortening due to too many teeth being on the one film.

The real challenge in veterinary dental radiography is obtaining a linear and dimensionally correct image.  To achieve this, the parallel and bisecting angle techniques have been developed. Parallel techniques (object and film parallel to each other with the x-ray beam aimed perpendicular to them) can be used for taking the mandibular premolar and molar teeth. A bisecting angle technique can be used for all other applications.

Parallel technique

Parallel technique – diagrammatic representation

Parallel technique – diagrammatic representation.

Parallel technique – positioning of tube-head perpendicular to the intra-oral film

Parallel technique – positioning of tube-head perpendicular to the intra-oral film.  The film has been positioned on the lingual side of the right mandible to take a radiograph of the first molar tooth.

Parallel technique – positioning of tube-head perpendicular to the intra-oral film. The film has been positioned on the lingual side of the right mandible to take a radiograph of the first molar tooth

Parallel technique – positioning of tube-head perpendicular to the intra-oral film.  The film has been positioned on the lingual side of the right mandible to take a radiograph of the first molar tooth.

Bisecting angle technique

The bisecting angle technique overcomes the problem of the palatal vault and difficulty placing the film parallel to the tooth.  This process involves placing the intra-oral film in a position as close to parallel to the tooth as possible.  Two imaginary lines are then drawn through the plane of the film and the plane of the tooth.  At the point where these two lines join, an angle is formed. If the tooth is parallel to the film, the lines will never meet, whereas if the tooth is perpendicular to the film, the angle will be 90 degrees.  After determining the angle formed by the film and the long axis of the tooth, a third imaginary line that bisects these two angles equally is drawn.  This is known as the bisecting line. The x-ray tube head and thus the xray beam is positioned perpendicular to this imaginary bisecting line.  This provides an image of the tooth on the film that is both linearly and dimensionally correct.

Bisecting angle technique – diagrammatic representation

Bisecting angle technique – diagrammatic representation.

 

Radiographic technique for incisor teeth

Bisecting angle technique – positioning of tube-head. The film has been positioned on the palatal surface caudal to the maxillary incisors to take a radiograph of the incisor teeth

Bisecting angle technique – positioning of tube-head.  The film has been positioned on the palatal surface caudal to the maxillary incisors to take a radiograph of the incisor teeth.

Bisecting angle technique – positioning of tube-head. The film has been positioned on the palatal surface caudal to the maxillary incisors to take a radiograph of the incisor teeth2

Bisecting angle technique – positioning of tube-head.  The film has been positioned on the palatal surface caudal to the maxillary incisors to take a radiograph of the incisor teeth.

Radiographic technique for canine teeth

Bisecting angle technique – positioning of tube-head. The film has been positioned at the cranio-dorsal edge of the nose adjacent to the right maxillary canine to take a radiograph of the canine tooth

Bisecting angle technique – positioning of tube-head.  The film has been positioned at the cranio-dorsal edge of the nose adjacent to the right maxillary canine to take a radiograph of the canine tooth.

Bisecting angle technique – positioning of tube-head. The film has been positioned at the cranio-dorsal edge of the nose adjacent to the right maxillary canine to take a radiograph of the canine tooth2

Radiographic technique for maxillary premolar and molar teeth

Bisecting angle technique – positioning of tube-head. The film has been positioned towards the maxillary premolar teeth to take a radiograph of the maxillary left fourth premolar tooth

Bisecting angle technique – positioning of tube-head. The film has been positioned towards the maxillary premolar teeth to take a radiograph of the maxillary left fourth premolar tooth2

Bisecting angle technique – positioning of tube-head.  The film has been positioned towards the maxillary premolar teeth to take a radiograph of the maxillary left fourth premolar tooth.

Foreshortening and Elongation

An x-ray beam angle that is too acute would produce a shortened tooth image, whilst an increased x-ray beam angle would result in an elongated tooth image.  This is termed foreshortening and elongation respectively.  Foreshortening results in a short rooted tooth and usually reduces the chances of making a diagnosis, especially at the apex, as the periapical radiolucency is almost obscured.  Elongation results in a long rooted tooth, limiting the diagnostic qualities, and often resulting in the tooth image missing the film.

Radiograph of the normal length of the maxillary incisor teeth

Radiograph of the normal length of the maxillary incisor teeth – the length of the blue line is the length of the crown and root of the first incisor tooth, the length of the yellow line is the length of the crown and root of the second incisor tooth and the length of the red line is the length of the crown and root of the third incisor teeth.

Radiograph of the maxillary incisor teeth showing foreshortening

Radiograph of the maxillary incisor teeth showing foreshortening– the length of the blue line is the normal length of the crown and root of the first incisor tooth – note the tooth is shorter than the line, the length of the yellow line is the normal length of the crown and root of the second incisor tooth – note the tooth is shorter than the line and the length of the red line is the normal length of the crown and root of the third incisor teeth – note the tooth is shorter than the line.

Radiograph of the maxillary incisor teeth showing elongation

Radiograph of the maxillary incisor teeth showing elongation– the length of the blue line is the normal length of the crown and root of the first incisor tooth – note the tooth is longer than the line, the length of the yellow line is the normal length of the crown and root of the second incisor tooth – note the tooth is longer than the line and the length of the red line is the normal length of the crown and root of the third incisor teeth – note the tooth is longer than the line.

Radiographing three rooted teeth

Radiographing three rooted teeth such as the maxillary fourth premolar requires skill to separate the roots.  If the radiographic beam is directly perpendicular to the maxilla, the mesio-buccal root and the palatal root are often superimposed and the radiograph is of little diagnostic value.  To separate the roots, the angle of the x-ray beam must be adjusted mesially or distally.  If the tube-head is positioned so the x-ray beam comes from the mesial aspect of the patient’s head, then the mesio-buccal and palatal roots will be separated and the mesio-buccal root will appear between the palatal and the distal roots on the film, but the distal root may be superimposed over the roots of the first molar tooth.

If the tube head is positioned so the x-ray beam comes from the distal aspect of the patient’s head, the mesio-buccal and palatal roots will be separated and the palatal root will be positioned on the film between the mesiobuccal and the distal roots, but the mesio-buccal root may be superimposed over the third premolar tooth.

The shifting of the images or roots, as described, is referred to the ‘tube shift technique’, it has also been termed the SLOB rule or Clark’s rule.  SLOB stands for ‘Same Lingual Opposite Buccal’, which means – when the tube head is moved, the root that moves in the same direction is the lingual/palatal root, whereas the root that moves in the opposite direction of the tube-head is the buccal root.

Problems associated with intra-oral images

Image blurred

  • Cause: Film, machine or patient movement
  • Correction: Retake radiograph

Double image

  • Cause: Double exposure
  • Correction: Retake radiograph using fresh film and depress hand switch only once

Short, Stubby or Dense Teeth

  • Cause:X-ray beam aligned too close to the vertical aspect (foreshortening)
  • Correction:Realign x-ray beam

Image distortion

  • Cause:Excessive bending of film during positioning
  • Correction:Keep film as flat as possible

Blank film

  • Cause:Hand switch depressed incorrectly or x-ray machine malfunctioning
  • Correction:Depress switch completely for full exposure time

Inconsistent film density

  • Cause:Hand switch depressed incorrectly
  • Correction:Depress switch completely for full exposure

Partial image

  • Cause:Film not completely immersed in developer or head of x-ray cone misaligned (elongation)
  • Correction:Check alignment of x-ray cone and replenish fluid levels

Grainy appearance

  • Cause:Elevated developer temperature or low intensity x-ray beam
  • Correction:Check chemical temperature or alter exposure settings

Blurry, magnified image

  • Cause:Film too far from subject
  • Correction:Place film as close to subject as possible and use long x-ray cone

Fuzzy roots

  • Cause:Excessive angle of x-ray beam
  • Correction:Change angle

Superimposition

  • Cause:X-ray beam aligned too far in mesial or distal direction
  • Correction:Realign x-ray beam