ch 8: digital dental radiography

basic concepts

-Used to record radiographic images

-No film or processing chemistry is used

-Uses an electronic sensor and specialized computer software that produces x-ray images almost instantly on a computer monitor

-Need: sensor, X-radiation source, computer with imaging software

purpose of digital radiography

-To generate images that can be used in the diagnosis and assessment of dental disease

-Image not radiograph or x-ray film

-Conventional and digital = preferred exposure method is paralleling technique, when possible

use of digital radiography

-To detect lesions, diseases and conditions of the teeth and surrounding structures

-To confirm or classify suspected disease

-To localize lesions or foreign objects

-To provide information during dental procedures

-To evaluate growth and development

-To illustrate changes secondary to caries, periodontal disease, or trauma (follow up)

-To document the condition of a patient at a specific point in time

-To aid in the development of a clinical treatment plan

-Interproximal incipient? Occulsal incipient? Same

digital radiography

A method of capturing a radiographic image using a sensor, breaking it into electronic pieces, called pixels, (silver halide crystals), and presenting and storing the image using a computer

fundamentals of digital radiography

-Image is used to describe the pictures that are produced

-A sensor is placed inside the mouth

-Extra oral can also be produced

-The electronic signal is digitized

radiation exposure

-The sensor is more sensitive to x-rays than conventional film

-Exposure times are 50% to 90% less than required for conventional radiography

-Increased sensitivity = less exposure

-Less exposure = ALARA

x-radiation source

-Most digital radiography systems use a conventional dental x-ray unit as the x- radiation source; x-ray unit mounted to wall

-Only difference:

• The x-ray unit timer must be adapted to allow exposures in a time frame of 1/100 of a second

• If the timer cannot be adjusted the unit needs to be replaced

intraoral sensor

-A small detector that is placed in the mouth of the patient and used to capture the radiographic image

-can be wired or wireless

wired intraoral sensor

-The imaging sensor is linked by a fiber optic cable to a computer.

-Instantly displayed on the computer.

wireless intraoral sensor

-The imaging sensor is not linked by a cable. Uses wi-fi

-Thicker

-More expensive

Two types of direct sensor technologies exist

-Charge-coupled device

-Complementary metal oxide semiconductor/active pixel sensor

Charge-Coupled Device (CCD)

-The “most” common image receptor used in dental digital radiography

-A solid-state detector that contains a silicon chip with an electronic circuit embedded in it

-The electrons that make up the silicon CCD can be visualized as being divided into an arrangement of blocks or picture elements known as pixels

-The x-ray photons that come into contact with the CCD cause electrons to be released from the silicon and produce a corresponding electronic charge

-Each pixel arrangement, or electron well, contains an electronic charge proportional to the number of electrons that reacted within the well

-Each pixel (electronic well) corresponds to a specific area on the linked computer screen

pixel

-A small box or “well” into which the electrons produced by the x-ray exposure are deposited

-Black metallic silver / into sensitivity speck

Complementary Metal Oxide Semiconductor/Active Pixel Sensor (CMOS/APS)

-CMOS alone not useful until APS was developed

-Small pixel size and lower power requirements

-The chip is less expensive to produce

computer with imaging software

-Used to store the incoming electronic signal

-Converts the electronic signal from the sensor into shades of gray that are viewed on the computer monitor

-The imaging software digitizes, processes, and stores information received from the sensor

-An image is recorded on a computer monitor in 0.5 to 120 seconds

-Has split screen, magnification & enhancement

computer

-Each pixel can create 256 shades of gray

-Human eye can perceive 32 shades

-Software is used to enhance

-Allows for manipulation of pixel or group of pixels to allow the human eye to adapt

• Contrast

• Density

• Without additional exposures

types of digital imaging

-direct digital imaging

-indirect digital imaging

types of direct digital imaging

-Charge-coupled device

-Complementary metal oxide semiconductor/active pixel sensor

indirect digital imaging

-Scanning traditional radiographs

-Storage phosphor imaging

-“Inferior to direct”

direct digital imaging

-Components include an x-ray machine, an intraoral sensor, and computer monitor

-A sensor is placed into the mouth of the patient and exposed

-The sensor captures the radiographic image and transmits it to the computer monitor

-Software is used to enhance and store the image

-Once the sensor is exposed the transfer of information is direct

components needed for indirect digital imaging

-Dental x-ray unit

-PSP plate: Photo-stimulable phosphor imaging

-Scanner: Extra step / indirect

-Computer

storage phosphor imaging

-A wireless digital radiography system

-A reusable imaging plate coated with phosphors is used instead of a sensor with a fiber optic cable

-The phosphor-coated plates are flexible and fit into the mouth

-A high-speed scanner is used to convert the information into electronic files

-This type of digital imaging is less rapid than direct digital imaging

storage phosphor process

-Each plate is exposed to radiation and removed from oral cavity

-Placed into an electronic processor (high speed scanner) where a laser scans the plate

-Image is produced on computer screen

-Can take up to 5 minutes

-Images are cleared from the plate by exposure to white light (viewbox)

-Currently have specialized scanners that scan, retrieve and clear the plate

storage phosphor procedure

-Disposable barrier

-Disinfected and reused

-Handled with care

• Bent

• Scratched

-Reused a minimum of 50 times

-Newer “Opposite side toward tube head”

-Some can not tell if image has been exposed backward

-Review mounted film with patient present

sensor preparation

-Each sensor is sealed and waterproofed

-The sensor must be covered with a disposable barrier because it cannot be sterilized. Finger cot can be placed underneath

-Sensors are not autoclavable & should be wiped with iodophor products

-Treat cord with care: make sure patient is not biting on the cord

sensor placement

-The sensor is held in the mouth by bite- block attachments or devices that aim the beam and sensor accurately

-The cord is going out of mouth

-The paralleling technique is the preferred exposure method

-Wired, wireless and PSP plates

advantages of digital radiography

-Superior gray-scale resolution

-Reduced exposure to x-radiation

-Increased speed of image viewing

-Lower equipment and film cost (futuristically)

-Increased efficiency

-Enhancement of diagnostic image

-Effective patient education tool

-Eco-friendly

disadvantages of digital radiography

-Initial set-up costs

-Image quality

• Debatable ???

  • Conventional 12 – 20 lp/mm

  • Digital 6 -- 22 lp/mm but can produce 256 shades of gray

  • Human eye 8 – 10 lp/mm

  • CCD system is more effective in disease detection

-Sensor size

• Gag reflex; Max molars worst, last (true with any x-ray)

-Infection control

-Wear and tear

-Legal issues

• Original digital images can be enhanced

• Software warning; image enhanced/modified

things to remember

-store sensor in holster

-always barrier sensor

-do not autoclave

-do not cold sterile

-do not use cleaning products like bleach

-clean with pre-moistened cavi wipes or advantaclear wipes

-do not pull or kink cable

-do not attach snap-a-ray or hemostat directly

tools for sensor placement

-disposable adhesive tabs and holders

• throw away

-autoclaveable holders

• RINN

-edge ease

• over plastic sleeve not on sensor