digital imaging

Question 1

basic concepts of digital imaging

Answer 1

• used to record radiographic images
• no film or processing chemistry is used
• uses an electronic sensor and computerized imaging system that produces x-ray images almost instantly on a computer monitor

Question 2

terminology:

Answer 2

• analog image
• bit-depth image
• Charge-coupled device (CCD)
• Digital imaging
• Digital image
• Digital subtraction
• Digitize
• Direct digital imaging
• Indirect digital imaging
• Line pairs/millimeter (lp/mm)
• Pixel
• Sensor
• Storage phosphor imaging

Question 3

brief explanation of why we use digital imaging

Answer 3

• to generate images that can be used in the diagnosis and assessment of dental disease

Question 4

purpose and use

Answer 4

• to detect lesions, disease, and conditions of the teeth and surrounding structures
• to confirm or classify suspected disease
• to provide information during dental procedures
• to evaluate growth and development
• to illustrate changes secondary to caries, periodontal disease, or trauma
• to document the condition of a patient at a specific point in time
• to localize lesions or foreign objects
• to aid in the development of a clinical treatment plan

Question 5

fundamentals of digital imaging

Answer 5

• a method of capturing a radiographic image using a decors, breaking it into electronic pieces, and presenting and storing the image using a computer
• the term image is sued to describe the pictures that are produces instead of radiographs
• a sensor is placed inside the mouth
• the electronic signal is digitized

Question 6

radiation exposure in digital imaging

Answer 6

• the typical sensor is more sensitive to x-rays than conventional film. requires less x-radiation exposure
• exposure times are 50%-90% less than that required for conventional radiography because the sensor is more sensitive to x-rays than conventional film
• ex. conventional intraoral film, which takes 0.5 seconds would take 0.05 seconds to produce and image for digital radiography

Question 7

equipment for digital imaging

Answer 7

• x-ray unit
• sensor: charged couple device (CCD), complementary metal oxide semiconductor/active pixel sensor, charge injection device
• computer

Question 8

x-radiation source

Answer 8

• most digital radiography systems use a conventional dental x-ray unit as the x-radiation source (it is compatible with digital imaging system)
• the x-ray unit timer mist be adapter to allow exposure times in a time Frame of 1/100 of a second
• unit can still be used for conventional radiography

Question 9

intraoral sensor

Answer 9

• a small detector that is placed in the mouth of the patient and used to capture the radiographic image
• wired: the imaging sensor is linked by a fixer optic cable to a computer (8-35 ft in length)
• wireless: the imaging sensor is not linked by a cable

Question 10

what size dimensions are intraoral sensors made?

Answer 10

• most sensors produced in similar dimension to size 0,1,2 and 4 intraoral films

Question 11

most popular types of direct sensor technologies

Answer 11

• charge-coupled device (CCD)

- complementary metal oxide semiconductor/active pixel sensor

Question 12

what is a charged-coupled device (CCD)?

Answer 12

• the most common image receptor used in dental digital imaging
• 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 potential well, contains an electronic charge proportional to the number of electrons that reacted within the well
• each electronic well corresponds to a specific area on the linked computer screen

Question 13

what is a pixel?

Answer 13

a small box or ‘well’ into which the electrons produced by the x-ray exposure are deposited

Question 14

what is a complementary metal oxide semiconductor/active pixel sensor (CMOS/APS)?

Answer 14

• one manufacturer uses a CMOS/APS sensor instead of a CCD

- the tip is less expensive to produce and offers greater durability than the CCD

Question 15

what does the computer do?

Answer 15

• used to store the incoming electronic signal; converts the electronic signal from the sensor into a shade of gray that is viewed on the computer monitor
• the computer digitizes, processes and stores information received from the sensor; an image is recorded on a computer monitor in 0.5 to 120 seconds
• image may be permanently stored in computer, printed or transmitted electronically to insurance companies or referring dental specialties
• has split screen and magnification capability

Question 16

types of digital imaging:

Answer 16

2 methods

• direct digital imaging
• indirect digital imaging (storage phosphor imaging / PSP)

Question 17

what is direct digital imaging? what does this include for components?

Answer 17

• components include an x-ray machine, an intraoral sensor, and a computer monitor
• a sensor with a fixer optic cable linked to the computer is placed into the mouth of the patient and exposed to x-radiation
• the sensor captures the radiographic image and transmits it to the computer monitor within seconds
• software is used to enhance and store the image

Question 18

what is indirect digital imaging?

Answer 18

• storage phosphor imaging (PSP)
• 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 plated are flexible and fit into the mouth
• resembles an intensifying screen used to exposed extra oral film in that it converts x-ray energy into light
• the radiographic images are cleared from the plates by exposure to view box light for several minutes
• 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 (30 secs. - 5 mins)

Question 19

step-by-step procedures

Answer 19

• sensor preparation
• sensor placement
• *it is critical to refer to manufacturer provided instruction booklet for info concerning the operation of the system, equipment preparation, patient preparation and exposure

Question 20

sensor preparation

Answer 20

• each sensor is sealed and waterproofed (the sensor must be covered with a disposable barrier because it cannot be sterilized)
• rigid digital sensors, wired or wireless, must be covered with a disposable barrier sleeve (ribber finger cot may be placed to further protect the wired or wireless sensor, and to prevent cross-contamination)

Question 21

sensor placement

Answer 21

• the sensor is held in the mouth by bite-block attachments or devices that aim the beam and sensor accurately
• the paralleling technique is the preferred method of exposure

Question 22

advantages of digital imaging

Answer 22

• superior to Gray-scale resolution
• reduced exposure to x-radiation
• increased speed of image viewing
• lower equipment and film cost
• increased efficiency
• enhancement of diagnostic image
• effect patient education tool
• eco-friendly tool

Question 23

disadvantages of digital imaging

Answer 23

• initial setup costs
• image quality
• sensor size and thickness
• infection control
• wear and tear
• legal issues