Dental Digital Radiography

DENTAL DIGITAL RADIOGRAPHY UNDERSTANDING IN A FEW EASY STEPS. DENTAL DIGITAL IMAGES TODAY PROVIDE ENHANCED RADIATION SAFETY LEVELS AND IMPROVED DIAGNOSTIC PERFORMANCE. IT ALSO FACILITATES MORE CHAIRSIDE TIME TO DEVOTE IN CARE OF DENTAL PATIENTS.

Basic Descriptive Terminology

Radiograph/Dental Image Versus X-rays

A radiograph is a 2-dimensional view film of a 3-dimentional object

With digital radiography (imaging) no film is utilized so the term radiograph is not pertinent.

In digital imaging the term Digital Image is used instead of radiograph and refers to an image composed of pixels. Regular radiographic films received its image density from the silver salts exposure to the x-ray beam and required chemical processing to view on the film.

Dental Image is now used to describe what is viewed on radiographs and/or digital images.

A dental image appears radiolucent (dark or black) where the tissues are thin or very soft and radiopaque (white or light) were tissues are hard or dense like bone for example.

Advantages of Digital Imaging Superior gray scale resolution.

Digital imaging uses up to 256 or more shades of gray. This advantage is critical because diagnosis is often based on contrast discrimination.

Lower Cost and Effective Patient Education Tool.

Reduced exposure to radiation. Its about 50 to 90% less than that required for E-speed film used in conventional radiography.

Increased speed image viewing. Image could be viewed within moments after exposure.

Increased Efficiency. More time available chairside with treatments and dental patient care

Enhancement of diagnostic image.

Conventional dental film only has 16 to 25 shades of gray. It has less ability in capturing great detail or resolution.

Film not as sensitive to energy beam x-ray.

Exposed film had to undergo costly and later environmental impact chemical processing.

Dentist, Assistant and Patient had to wait for dental film processing. Dental films had to be copied and mailed to insurance companies.

Disadvantages of Digital Imaging Initial set-up and training to include regular maintenance and

repair

On the up side it does away with darkroom machines, chemicals and disposal.

Image quality. Human eye can only perceive 8 to 10 lp/mm so debate since regular film radiographs are higher 12 to 20 lp/mm. CCD allows 10 Lp/mm so more closer to what is needed to detect disease. Lp/mm= ability of computer to capture detail of images.

Sensor Size and thickness

Infection control

Legal Issues. Always keep non-enhanced originals saved on computer prior to digital image enhanced for discovery

Infection Control

Wear and Tear

Digital SubtractionA benefit of using Dental Digital Radiography is the enhancements that the software

allows for diagnostic purposes

Digital ImageRadiopaque (white areas) with outer area radiolucent (black or dark gray)

Digital Image Bite-wing Image Radiopaque (white areas) as first image and as normal image view

Bite-wing Image

Digital Subtraction

Bite-Wing Image This digital image has the Digital Subtraction enhancement done after image stored on the computer software. It reverses the shades of gray for diagnostic purposes. Radiopaque (normally white images are now looking translucent (dark or gray)

Review of Basic Terminology for Easier Understanding

Analog image- Image produced by conventional film

Bit-depth image- number of possible gray- scale combinations for each pixel. (e.g., 8 bit-depth image has a gray scale combination of 2 (8) power, which equals 256 shades of gray.

Charged- Coupled device- (CCD) – CCD is an image receptor found in the intraoral sensor. This solid state detector is used in a fax machines, home video cameras and now in digital imaging.

Digital Imaging- a method of capturing a radiographic image with a sensor which gets broken down into electronic pieces to later store and present the image in a computer.

Digital image- An image composed of pixels.

Digital Subtraction- This is a special feature in digital imaging when one reverses the gray scale as an image is viewed, for example, radiolucent images that in the digital image look black will appear white or radiopaque and the areas normally radiopaque (that normally appear white such as gold crowns or fillings will look translucent or radiolucent.

Review of Basic Terminology Part two

Digitize- to convert an image into a digital form.

Direct Digital Imaging- Method of obtaining a digital image in which an intraoral (inside of the mouth) sensor is exposed to x-radiation to capture an image that can be viewed on the computer screen.

Indirect digital imaging- is when we obtain an image that was scanned from an existing film. It is converted into digital form by using a CCD camera. (CCD is an image receptor) It is considered a copy since not the original for was scanned. It’s important to always save original film and digital images for legal purposes and insurance in case of denial on a claim.

Line Pairs/Millimeter (lp/m)- Measurement used to evaluate the ability of the computer to capture the resolution (or detail) of a radiographic image.

Pixel- unit of information in digital images and these discrete units of information are also termed picture elements.

Sensor- for digital imaging this is a small detector that is placed intraoral (inside of the mouth) to capture a radiographic image

Another important term is Storage Phosphor Imaging- when a digital image is obtained by recording it on phosphor- coated plates and then placed into an electronic processor where a laser scans the image in the plate and produces it into a the computer screen. A scan is a copy of the stored original image. One could imagine storing Austin Powers (Mike Myers) Dental image to computer to later show him on monitor. (Image Virgin Media, 1990).

Understanding Digital Imaging in Easy Steps

How does it really work and to what purpose?

Digital imaging main purpose is to generate images that can be used for diagnosis and assessment of dental disease. Also equivalent to conventional film yet more time efficient, economic and with more informational data for diagnostics.

How does Digital Imaging Really Work?1- Dental Imaging works by capturing an image using a sensor that “breaks” the image into electronic pieces or picture elements known as pixels and presenting and storing the image using a computer.

In contrast, film based images are produced when the x-ray photons strike the intraoral film and that information was recorded in the film silver halide crystals latent until we developed the image with processing chemicals. The image taken on film is known as an analog image. Analog images are composed of shades of gray that flow into each other like a cloud of grays.

Digital imaging creates pixels with discrete gray values for each pixel forming a distinct mosaic pattern. This provides a lot more detail and important in dental radiography when we wish to detect disease. In analog image its harder to detect for example a minor radiolucent cyst at the apex of a tooth for has more foggy shades of gray.

Digital Fundamentals 2- As in conventional radiography, an x-ray beam source is needed and in digital imaging we have it strike the sensor using beam alignment devices. This is called Direct Imaging since we place an intraoral sensor to capture directly the image to them transmit to a computer. In indirect imaging, a scan and therefore a copy of a traditional radiograph is done using a CCD camera that digitizes the image to display on computer. A second indirect system is the Photo-Stimulate Phosphor Imaging. (PSP)-On Next slide discussed. The sensor may be wired with a fiber optic cable placed

within the alignment device or work wireless transmitting electronically the image.

The data acquired by the sensor is communicated to the computer in analog form and then converted into digital form by an analog to digital converter. Software is then used to store the image electronically. The image is displayed quickly and ready to be enhanced for interpretation or diagnosis.

With digital imaging the term Image is used (not x-ray or radiograph)

Two Indirect Digital Imaging Systems

Scanning Traditional Films Use of a CCD

Camera and a computer

Considered a copy of an original image

Storage Phosphor Imaging/

A reusable plate coated with phosphors is used instead of a sensor

Its is flexible and inserted in mouth. The plate in then placed in an electronic processor where a laser scans it producing image to view on computer.

The second type of indirect imaging is the Storage Phosphor Imaging

This system uses a reusable imaging plate coated with phosphors acting as the sensor and is wireless for has no cable. The images are cleared when exposed to a view box after several minutes. Once the images are erased the phosphor plate may be wrapped in plastic and sterilized. Description of image on the right: GENDEX DENOPTIX I/O PA USB DENTAL DIGITAL PHOSPHOR PLATE IMAGING X-RAY SCANNER SYSTEM (2011 converted to USB) A laser scans the plate and it takes 30 sec. to 5 min

Sensor with Beam alignment Device

Factoids about Sensors A pixel in the sensor acts like a

well that receives electronic photons from x-ray machine. There it reacts with electrons embedded in the circuit of silicon chip . The pixel plays the role of the silver crystals in a film.

The advantage is that the pixel has a more structured ordered arrangement. (more detail)

The x-radiation after activating the electronic charges in the pixel “well” causes an electronic latent image to be produced then is transmitted and stored in the computer and converted to a visible image on the screen.

You are now more Confident about understanding Dental Digital

Radiography

Dental Assisting is a rewarding field

It is important to be familiar with different techniques, dental office materials and technologies.

With pre- text book reading, understanding of lectures and actual practice you will be on your way to becoming an excellent Assistant

A summary handout is available

References

Joen M. Lannuci, Laura J. Howerton. (2012). Dental Radiography: Principles and Techniques. US: Elsevier

Intellitec Institute

By Theresa Nielsen for Intellitec Dental Assisting 2014