DIGITAL RADIOGRAPHY: A NEW ERA IN DENTAL RADIOLOGY

Updated: February 07, 2015 5:47 PM

Dr Aarti Sharma Kapila, GM – Quality and Dental Administration, Clove Dental, shares insights on the advent of digital radiography in dental radiology and its advantages

Dr Aarti Sharma Kapila, GM – Quality and Dental Administration, Clove Dental, shares insights on the advent of digital radiography in dental radiology and its advantages

201501inimage38Dr Aarti Sharma Kapila

Digital radiography is one of the most important advancements in dental radiology. The dawn of the digital era in dental radiography came in 1987, when the first digital radiography system called RadioVisioGraphy, was launched in Europe by the French company Trophy Radiologie. The inventor of this system was Dr Francis Mouyen. He invented a way to employ fibre optics to narrow down a large X-ray image onto a smaller size that could be sensed by a charge-coupled device (CCD) image sensor chip.

Even though digital radiography has been available in dentistry for more than 25 years, it has not been accepted by all dental practitioners due to various reasons. Some people are reluctant to make the change because they are unsure of what to expect during the change-over period and what type of problems they may encounter.

201501inimage39Digital radiography I : Bitewing X-ray image

The main difference in the digital radiography is that the film is replaced by an image receptor. Two major types of image receptors are available: charge-coupled device (CCD) and storage phosphor (SP) systems. Although the X-ray source used could be same, the dose is much lower than conventional film radiography because in digital imaging, the receptors are highly sensitive sensors that require considerably less radiation exposure than film.

Digital dental images are acquired through three methods: the direct method, indirect method and semi-indirect method. The direct method uses an electronic sensor placed in the mouth to record images. The indirect technique uses an X-ray film scanner to view traditional dental X-rays as digital images. The semi-indirect digital technique combines a sensor and scanner to convert dental X-rays into digital film. The most commonly used method is the direct method.

Types and uses of digital dental radiographs

Digital dental radiographs can be taken inside (intraoral) or outside (extraoral) the mouth. Intraoral X-rays, the most commonly taken dental X-ray, provide great detail and are used to detect cavities, check the status of developing teeth and monitor teeth and bone health. Extraoral X-rays do not provide the detail of intraoral X-rays and are not used to identify individual tooth problems. However, they are used to detect impacted teeth, monitor jaw growth and development, and identify potential problems between teeth, jaws and temporomandibular joints (TMJ), or other facial bones.

201501inimage40Digital radiography II : Colour contrast on digital X-ray images which helps in more definitive diagnosis

If we compare, a traditional radiographic image is composed of radiolucent (dark) areas in which the silver grains in the emulsion are densely packed and radiopaque areas in which the grains are more dispersed, having been washed out during the film processing. Although a digital image seen on the screen as a collection of brighter and darker areas very much resembles the traditional film-based image, the nature of a digital image is completely different. A digital image, on the other hand, is composed of a set of cells that are called ‘pixels’ arranged in rows and columns. Digital images can be altered after they have been produced. This is achieved by altering the pixel values, which can change certain characteristics of the image. This is called ‘image processing.’

201501inimage41Digital radiography III: X-ray image showing RC treated tooth with crown

As compared to conventional radiography, digital radiography has many additional advantages. The main advantage of digital radiography is that many tasks associated with film use are simplified or eliminated.

Decreased radiation dose: Digital radiography systems reduce radiation exposure to patients by up to 50 per cent compared to film-based systems. Although film-based radiography systems are indeed exceptionally safe, digital radiography conforms to the very important ALARA principle (as low as reasonably achievable) more precisely than film-based radiography. This is a radiation safety principle for minimising radiation exposure to both patient and operator by employing all reasonable means possible.

One of the advantages of digital imaging is that once acquired, the image can be changed and viewed in a variety of ways using image enhancement software. Common enhancements tools include:

  • Image processing
  • Black/ white reversal
  • Zoom
  • Digital substraction radiography

Image processing helps in the optimisation of contrast and brightness of an image. It can help to rescue an image in which exposure conditions were not optimal and thus prevent the need for a remake, saving the patient from an extra dose of radiation. It is also possible to adjust the contrast and density of an otherwise correctly exposed image to optimise the recognition of caries or the assessment of periodontal bone lesions. It is reasonable to assume that in the near future, software for digital radiography will include tools to optimise contrast and brightness automatically for specific diagnostic tasks.

201501inimage42Digital radiography IV: Orthopantomogram X-ray image-OPG

The black/ white reversal option allows one to view structures by inverting or reversing the image so that radiolucent structures appear radiopaque and vice versa. This tool may be useful in visualising the trabecular pattern of bone and pulp canal and chamber anatomy. Another simple but effective tool is the ability to zoom in an image. By using a two-fold or three-fold magnification, the user can recognise details more easily.

Digital substraction radiography is a technique used to determine qualitative changes that occur between two images taken at different points in time. This procedure allows us to distinguish small differences between subsequent radiographs that otherwise would have remained unnoticed because of over-projection of anatomical structures or differences in density that are too small to be recognised by the human eye. Applications of digital substraction radiography in general practice include diagnosis and follow-up of periodontal bone resorption, assessment of bone levels around implants and then progression of healing of periapical lesions.

Edge enhancement converts contrast gradients into a texture that is visible as a shape. The human eye recognises shapes better than it does small contrast gradients. This ability allows the practitioner to detect, for instance, the point of an endodontic file in an image more easily.

Other advantages

  • Eliminates the need for the darkroom and chemical processing: This is one of the biggest advantages of digital radiography. A dark room requires additional space in the dental clinic. So it adds to the expenses. The management of chemical waste that is produced in a dark room is a difficult task. The elimination of chemical processing helps the dentist to manage the dental clinic more efficiently and it also makes a digital imaging system more eco-friendly.
  • Time saving: Digital radiography is fast. The images we take are ready to view in less than one second after shooting. But in the case of conventional radiography it takes a minimum of five to eight minutes to develop the film. If a processing error occurs in the dark room (over- or under-developed radiograph), the radiograph will need to be repeated, as the faulty processing makes the film-based radiograph useless for a diagnostic procedure.
  • Teleradiography: The transfer of a digital image to a distant site is called teleradiography. In order to accomplish this task, the sender and receiver must be able to generate an image that can be read by various software programmes or have the same software. Teleradiography has the potential for off-site consultation, insurance submission and improved access to care for patients in remote locations.
  • Extreme importance of digital radiography in implantology: When accomplishing implant placement, using conventional radiography is a major inconvenience, as the entire aseptic procedure is disrupted and time is wasted while the clinician awaits the development of the films several times during the implant placement procedure.

Disadvantages of digital radiography

201501inimage43Digital radiography V: Wall mounted long cone X-ray emitting device

Like any other technology, digital imaging also has some limitations. The initial cost of purchasing and setting up the equipment, as well as the cost of training staff members how to use the equipment represents a disadvantage of digital imaging systems. Sensors are the weakest part of the system due to their relative rigidity and thickness (approximately 5 mm); they can cause discomfort or pharyngeal reflex in patients.

The viewable surface area is smaller than the total size of the sensor and sometimes sensors are not universal and interchangeable between different systems. Digital sensors can’t withstand heat sterilisation; therefore they require complete coverage with disposable plastic sleeves.

201501inimage44Digital radiography VI: Wall mounted short cone X-ray emitting unit

In conclusion, digital radiography is an excellent alternative to film-based radiography and continues to grow in popularity. The diagnostic accuracy achieved with digital radiography is as good as with film in most cases, and the disadvantages associated with earlier types of equipment have been resolved with advances in technology. New software tools are under development by researchers and manufacturers to improve the diagnostic outcome of digital radiography. An area that is continuously under development is the application of artificial intelligence (AI) to the interpretation of digital radiographs.

Digital radiography is becoming popular among dental practitioners. As a new technology, it is under constant improvement and there are many advantages to digital radiography that cannot be achieved by film-based radiography. So, it has the potential to replace film-based radiography completely.

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