Oral Radiology Image Characteristics Part 2 Lecture Notes PDF

Oral Radiology IMAGE CHARACTERISTICS Part 2 OMD-711n Radiography in Dental Clinic  Objectives of Lecture By the end of the lecture ,the student should be able to :- 1-Choose and purchase the best X-ray machine suitable for a specific workload. 2-Identify the best e...

Oral Radiology IMAGE CHARACTERISTICS Part 2 OMD-711n Radiography in Dental Clinic  Objectives of Lecture By the end of the lecture ,the student should be able to :- 1-Choose and purchase the best X-ray machine suitable for a specific workload. 2-Identify the best exposure parameters during conventional imaging. 3- Demonstrate the significance of linking the chosen exposure parameters to yield an ideal diagnostic image Benefits of Dental Radiography in a Dental Clinic  Detection and diagnosis of diseases, lesions& conditions of teeth & bone that can not be detected clinically.  Confirming suspected diseases, and assisting in localization & treatment planning of lesions and foreign bodies.  Essential information during routine dental work as in R/C treatment.  Status of teeth and bone during dental development, during surgeries ,extraction ,removal of impactions, performing fixed prosthodontics,and implant insertion.  Patient records& documentation of the condition, follow-up of treatment and disease progress.  Beneficial for the patient as it minimizes troubles and problems during treatment. Equipments Needed to Implement Oral Radiography in Dental Clinic The equipments required for producing dental radiographs include :- A wall-mounted or mobile dental X-ray machine, Dental X-ray film/ or filmless system, and A method to develop the film (or a digital dry system).  Let’s start with the x-ray unit !!!!!!!! How to buy an x-ray machine? What to look for when purchasing an x- ray unit? Brands Shape Costs Color No  Durability  Quality  Reasonable costs  Let’s review the components of an X-ray Equipment 2 1 3 X-ray equipment has three basic components: (1) the x-ray tubehead, which produces the x-rays, (2) support arms, which allow you to move the tubehead around the patient’s head and (3) the control panel, which allows you to alter the duration of the x-ray beam (exposure time) and, on some x-ray machines, the intensity (energy) of the x-ray beam.  mA control exposure time kVp control The control panel, like the one above left, allows you to change exposure time but nothing else. Some machines, like the one above right, have controls for changing the mA and kVp settings in addition to exposure time. The individual controls will be discussed more later.  Types of X-ray Machines Mobile (portable) Fixed (Mounted and Fixed to a Certain Object) Hand-held (Handy)  Mobile Fixed Hand-held Valuable in University Wall mounted or Valuable during pandemics as it hospital dental clinics to mounted to dental unit is convenient for home radiology serve multiple rooms examinations More suitable for teaching Does not need Sustainability of its power supply and training means. capacity is via a rechargeable battery and space which could subject results to variations because of battery power if not regularly charged. Convenient for private Radiation protection is not totally offices with just one fulfilled. dental unit in one operating room It is mainly used in industrial With or without a stool researches and forensic medical work What is meant by Quality of a Unit???? A unit capable of producing images with optimum diagnostic qualities (ideal images) should be chosen by all clinicians. An ideal image = a diagnostic radiograph with optimum visual and geometric characteristics that yields superior diagnostic information. Most of geoemetric characteristics are controlled by factors related to the radiologist;proper film placement, and proper adjustment of film-object distance , and focal spot-object distance.Only one geometric character is related to the x-ray unit (sharpness ) and will be included in this presentation.  Therefore; IMAGE CHARACTERISTICS are : I-Visual II-Geometric Sharpness Density (Definition) Size Contrast Shape  Ideal Radiograph 1. Image same size as object. 2. Image same shape as object. 3. Image has good detail. 4. Image has good density and contrast.  How does selection of a dental film affects the density and contrast of an image. Dental Films are supplied in different sizes , types and speeds. Dental films may be extra-oral (large-sized to be used outside the oral cavity for imaging jaw and skull) or intra-oral (small-sized to be used inside the oral cavity for revealing teeth and supporting structures.  How does selection of a dental film affects the density and contrast of an image. Intra-oral films are classified according to their uses into : periapical , bite-wing ,or occlusal films. Hence, your first selection is based on the reason you are using this film for ; let’s shift to the next slide to understand this statement!!! This is a Bitewing Film Paper loop 16 tab This is the image produced by a Bitewing Film These are the Indicationsof a bite- wing Film Interproximal Caries Alveolar Bone Involvement Pulp chamber  This is a Periapical film The film is held in the proper position using the thumb, or index finger, or else use a film holder These are Indications of a periapical film : Widely used technique Periapical involvement Endodontics Periodontal evaluation Caries detection Impaction Fixed prosthodontics Implants Dr Gihan Omar  Occlusal Film Identify large lesions bucco-lingual dimension assessment SG stones fracture trismus patients Localization of impactions and foreign bodies.  After deciding which type of film you need according to your case ,your second selection will be based on which size of periapical/bite-wing/or occlusal film do you need. Dental Intra-oral Films are supplied in different Sizes;let’s shift to the next slide to know more about film sizes!!!!!!  Film Sizes (Intra oral) # 0: Children (PA & BW) # 1: Adult anterior (PA) # 2: Adult posterior (PA & BW); also used for children as an occlusal film (called standard size) # 3: Extra long (BW) # 4: Occlusal and Occlusal pediatric size  I.O. FILM SIZES #2 #3 B.W 0,1,2,3 PER. #1 0,1,2 OCC. #0 #4 4 After deciding which type and size of film you need according to your case ,your third selection will be based on the speed of the film. What is Film Speed??? Speed :Represents the amount of radiation required to produce a radiograph of acceptable density.  Speed Films are made of crystals, the larger the size of these crystals,the higher is the speed of the film. The higher the speed of the film,the less the exposure time required to produce optimum density on such film. The higher the speed of the film,the less is the sharpness of the image. Too light Proper density Too dark  Hence during exposure of a dental film ,the exposure time should be set according to the speed of the chosen film or else the density of the image will be altered ,putting in mind that the appropriate sharpness is not altered. To apply this complex selection, we must know the speeds of films ,the exposure time required for each speed and the sharpness accompanying each speed as follows Most Commonly Used Intra-Oral Film Speeds D-speed (Ultraspeed) E-speed (Ectaspeed): ½ exposure time than D / Less sharpness than D E+- speed(Ectaspeed +):Same exposure time as E / Better sharpness than E. F-speed (Insight): Needs very little ET↓(decrease of ET to 20%) / Less sharpness than E+  Film storage Heat Humidity Radiation Chemical fumes Expired date First in first out rule  Store at 10 – 21 degrees C (refrigerated), storage at high temperatures may result in film fogging. Opened boxes of extraoral films need to be kept in light-tight area (darkroom); need to be cool. Do not store film in rooms where radiographs are taken.  How does selection of the method of processing affects the density and contrast of an image? After the films are exposed to radiation, they need to be processed in order to see the information on the film. This processing is done using special chemicals and takes place in a darkroom or a daylight loader (manual processing). The darkroom should have the following attributes: It must be light-tight. Since the film crystals are sensitive to both x-rays and light, the area where films are processed must be completely dark, except for a safelight. It must have hot and cold water available; a mixing valve, which regulates temperature, is recommended. It should have an adequate size and must be kept very clean (no spilled chemicals)  Processing Room When processing films manually, it is important to check the solution levels at least once each day. If the solution level is too low, the films at the top of the film hanger may not be covered and will not be developed and/or fixed properly. The solution should be stirred frequently; the chemicals tend to settle to the bottom and need to be recirculated for optimum performance. You should check the solution temperatures often. The amount of time needed to develop the films is dependent on the temperature of the solutions. If With manual processnig in a darkroom, the temperature is too low, more two tanks, one containing developer and development time is needed. Too one fixer, are placed in a larger tank filled high a temperature requires less with water. time in the developer.  Manual Processing For manual processing, films are clipped to some type of film hanger (see below). The film should be handled only by the edges to avoid damage. The film hanger, with films attached, is then placed in the processing solutions, developer first. If the film is accidently placed in the fixer first, the film will come out completely clear (no image) (blank image); the fixer removes all crystals that have not been converted to black metallic silver by the developer.  Safelight Safelights are used in the darkroom to provide adequate light so that you can see what you are doing when you unwrap films for processing. The safelights have special filters that produce light that does not expose the film.  Safelight Filters There are two filters currently available: an orange one and a red one. The orange one can only be used for D-speed film. The red one can be used for all film types (D-speed, F-speed, extraoral, and duplicating). D-speed Intraoral, extraoral  Safelighting (continued) 15 W 15 watt bulb The safelight should have a 15-watt bulb and be mounted to the wall or ceiling at least 125 cm red filter from the area where the films are unwrapped and 125 cm loaded into the film processor. Basic Steps of Manual Processing After taking the films on the patient, they are taken to the darkroom for processing. The steps involved in processing are: 1. Development: the crystals of the exposed film are converted to black metallic silver 2. Rinsing: Used with manual processing only; developer solution removed from film before fixing 3. Fixing: unexposed silver halide crystals removed from film 4. Washing: all chemicals removed from film 5. Drying: after removing moisture, films can be handled for mounting  Manual Processing Times Develop 5 minutes at 20°C degrees Rinse 30 seconds (agitate continuously) Fix 4 minutes (Agitate intermittently) Wash 10 minutes in clean running water Hang films to dry  Replenishment Solutions tend to become depleted as more films are processed. This leads to inadequate developing and/or fixing and film quality will be decreased. To prevent this, it is important to replenish the solutions by adding 240 ml of chemical (both developer and fixer) each day. This will maintain the quality of the solutions for up to 30 films processed during the day. If more than 30 films are processed, additional solution must be added at a rate of 30 ml for every 4 films over 30.  Daylight Loader A daylight loader may be used if there is not enough room in the dental office for a darkroom. It can be used for intraoral films only and should be located in an area with reduced lighting. The unopened film packets are placed in the loader through the lid in the top and, after closing the lid, the operator reaches through the rubber cuffs, opens the films and puts them in the processor. Inside the box are small containers of developer, fixer, and water. lid Daylight Loader rubber cuffs  Automatic Processing Automatic processors come in various shapes and sizes, but they all function the same. The film is inserted in the inlet slot where it is fed into a series of rollers. These rollers transport the film through the developer, fixer, wash and dryer and the film exits the processor ready to mount. The rollers “squeeze” the excess chemicals off of the film as it exits each solution; no rinse is needed between the developer and fixer. The wash section is located below the drying rack. wash  Automatic Processing The manufacturer’s of automatic processors identify the ideal temperature to be used in processing. You should follow their recommendations. As with manual processing, the solutions should be replenished daily. Add 240 ml of developer and fixer for up to 30 films. Add 30 ml of chemical for every four films over 30. The above information pertains to intraoral films. If panoramic films are processed, they will deplete the chemicals more quickly, because of their size, and more frequent replenishment is needed. Relation between Processing and Film Density The density of the film can be affected by problems in the darkroom, resulting in a film that is too light (below right) or too dark (below left). too dark correct density too light  Dark Film A dark film can result from any of the following: Developer too hot Too much time in the developer Exposure to light (opening door, turning on light, light leaks around door, incorrect or cracked filters)  Developer too hot If the films are kept in the developer for the correct amount of time but the developer is too hot, the film will get darker as the temperature increases (see below). 20°C 26.5°C 32°C 35°C 5 minutes development time for all films  Too much time in the developer If the films are kept in the developer too long, even though the temperature is correct, the film will get darker as the time increases (see below). Notice that the effects are less pronounced with changes in time than they are with a change in temperature as seen on previous slide. 5 min. 10 min. 15 min. 20 min. All films processed at 20° C  Exposure to light The completely black area on the right side of the film below is caused by light exposing the film when the darkroom light (not safelight) was inadvertently turned on before the film was completely in the automatic processor. (The tightness of the rollers against the film prevented light from reaching the front part of the film). Opening the door during processing could also create this problem. Light leaks or faulty safelighting would result in an overall darkening of the film, similar to too high a temperature.  Light Film and low Contrast Both can result from any of the following: Developer too cold Not enough time in the developer Under replenishment (developer gets weak) Contaminated developer Excessive fixation (RESULTS IN LIGHT FILM ONLY) Questions