DIGITAL �RADIOGRAPHY

• The application of computer technology to radiography has allowed for image acquisition, manipulation storage, retrieval and transmission (teleradiography) to remote sites in a digital format
• The use of computer in radiography has given rise to new diagnostic method,

'THE DIGITAL RADIOGRAPHY'

• Light reacts with photographic film to create a photograph, and x-rays interact with x-ray film to make a radiograph-'film based imaging', where in the image is recorded on a film as an invisible latent image until processed in a dark room

• The replacement of this film based technology with computer based devices that use electronic x-ray detectors to record the x-ray image which is then processed by the computer, and is called as electronic image

​

• Film based images or radiographs are analog images whereas electronic images seen on computer screen are digital image.
• The use of term 'Digital' simply means that the computer has processed the image

Analog and digit images

• Conventional image or analog images consist of the arrangement of silver grains in photographic emulsion .
• Density of silver grains depends on intensity of the x ray beam.
• When viewed on transmitted light ,the pattern of different density is transmitted to the eyes ,percieved as different shades of gray.
• In digital imaging large number of small light sensitive elements is used.

• Generally speaking an analog image is characterized by continuous gradations from one area of the image to next
• An analog image, whether a radiograph or a color photograph, exhibits gradual changes from one color or shade to another
• Thus analog information is in a continuous fashion.
• The digital image results from the conversion of analog data to digital data which is done by the analog to digital converter or FRAME GRABBER

• In digital radiography the images are acquired by using the electronic image receptors called the

- solid state detectors- CCD,CMOS &FPD

- photostimulable phosphor technology

• The image receptors are made up of number of units called as PIXELS that actually stores the information until processed by the computer

WHY DIGITAL X-RAY?

1. Digital X-ray Saves time

​

• There is no delay between exposure and image appearance on computer screen.
• There is no need for time-consuming manual handling of film, imaging plate, film processor or image scanner.

​

2. Digital X-ray is COST EFFICIENT

• Elimination of costs related to X-ray consumables and the maintenance costs of film processing make running a digital practice highly economical
• The increased efficiency through time savings allow for increased patient yield and income.

​

• No chemical X-ray film processing,
• No darkroom
• No safelight/daylight arrangements
• No continuous maintenance and quality control
• No odors and difficult to dispose chemical waste.
• No film storage
• No manual handling of film

3. RADIATION HYGIENIC

• Patient dose decreases dramatically (up to 95%) compared to film based imaging.

4. ENHANCED DIAGNOSTIC QUALITY

• Digital image enhancement provides new dimensions for diagnostics
• Wide dynamic range makes the radiographs less sensitive for imaging parameters.

​

5. CONSISTENT IMAGE QUALITY:

• Digital images are not subject to variations and errors typical to film processing (time, replenishment of processing chemicals, temperature, light leaks)

6. DECISION SUPPORT:

• Digital images can benefit from automatic decision support systems.

7. SECURE STORAGE:

• Reliable electronic database with minimal administration provides an automatic, systematic and practical way to store and archive digital images.
• The user can easily make copies of the images without decreasing the diagnostic quality and the original images are always available.�

8. COMMUNICATIVE:

• Presenting digital images for the patient on a computer screen allows unlimited possibilities to procedure presentations

9. TRANSFERABLE:

• Images can be sent electronically to insurance companies and social security for faster reimbursement�

10.Digital X-ray supports quality oriented working

practices with detailed documentation of the

treatment

ASSEMBLY AND COMPONENTS

The basic components of digital radiographic imaging system are

1. An electronic sensor or detector/camera

2. Analog to digital convertor

3. Central processing unit

4. Monitor and printer

AN ELECTRONIC SENSOR OR DETECTOR

• Fundamentally two different concepts for direct digital image acquisition

1. Solid state detectors(CCD,CMOS & FPD)a cable connects the sensor to a computer and the image is displayed almost immediately on the computer monitor after exposure of the sensor.

2. Photostimulable phosphor or imaging plate (IP) systems: an image plate is exposed to x-rays and a latent image is created and the information contained in the plate is released by exposure to a laser scanner

CCD SENSOR OR DETECTOR

A CCD is an x-ray or a light sensitive array of semiconductors in a silicon chip

• CHARGE COUPLING" is simply a process by which accumulated light or x-ray photons are transferred from one electron well to the next in a sequential manner and finally to the readout amplifier

• Fibro-optically coupled sensors use a scintillation screen (an intensifying screen like lanex) coupled to a CCD
• When x-rays strike the screen material to produce photo electrons, and one x-ray photon will produce hundreds of light photons which are then sensed and stored by the CCD

“Bucket brigade” �

DIGITAL SENSOR

SCINTILLATOR

• Converts X-rays into light (photons)

FIBER OPTIC

• Transmits light to chip
• Stops X-rays

SEMICONDUCTOR CHIP

• Converts light into electrical signal (charge/voltage)

SIGNAL READOUT

• Dedicated electronics
• Conversion to digital
• Transmitted to computer

Scintillator

Fiber optic

Semiconductor

chip (CCD/CMOS)

Image readout

Direct data link to

the computer

ADVANTAGES

1. Instant images (elimination of the dark room)

2. Consistent quality

3. Image manipulation (image processing)

4. Tele-transmission capability

5. Reduced x-ray absorbed dose to patient

6. Elimination of hazardous chemicals used in film

processing

DISADVANTAGES

1. High initial cost system

2. Unknown life expectancy of CCD sensor

IMAGING PLATE (IP) �(Photostimulable Phosphor system)

• The digital images are obtained on a flat imaging plate (IP) with photostimulable phosphor
• This is referred to as COMPUTED RADIOGRAPHY.
• The use of imaging plate as an x-ray imaging sensor is based on the principle of photostimulable luminescence.
• The imaging plate system was first applied to panoramic radiography and now recently used for intra oral radiography
• The imaging plate is a polyester base sprayed and coated with a crystalline halide composed of Europium activated barium fluorohalide compounds (BaF Br:Ee²⁺).

WORKING MECHANISM

​

​

​

• Unlike the conventional systems which use CCD sensors this new system provides higher quality digital images in similar settings

IMAGING PLATE

​

1. Exposure

2. Prosphor plate stores a latent image

3. Laser beam releases the stored information

• Image readout in a special scanner
• Conversion to digital data

4. Erasure of the plate for reuse

​

A/D converter or Analog-Digital converter or Frame grabber

• An important component of digital radiographic system

​

• In case of the units using the CCD as a sensor, the continuous analog data is converted into digital data by the help of a A/D converter or a frame grabber as computers cannot display an image of analog data

​

• The analog information is converted into discrete units of information

• In case of the photostimulable phosphosystem or imaging plate system, the read out ofx-ray information is converted by a photomultiplier into electrical signals which are then converted into digital signals by an A/ D converter

​

• Once this conversion is done the data can be either stored or displayed on the monitor

Central processing unit or the personal computer

• The central processing unit or a personal computer should be equipped at least with 640 KB internal memory and a fixed dise along with its software.

MONITOR AND PRINTER

• The images are stored in a image, data base on a hard disc or on a magneto-optical device for a long term archiving
• Images can be hard copied by a laser printer, thermal paper printer or dry processing film printer
• Electronic images can also be transferred by telecommunication technology to other locations for viewing and study by several people at the same time.

Types of digital radiography

1. Direct Digital Intra-oral /Extra-oral Radiography

2. Indirect Digital Radiography

3. Digital Subtraction Radiography

4. Digital Panoramic Radiography

Direct digital intra-oral/�Extra-oral radiography

There are fundamentally two different concepts for direct digital image acquisition.

1. The CCD based (charge coupled device)

2. Storage phosphor (SP) system

Systems functioning on CCD technology

R V G : RADiOVISIOGRAPHY :

• In this system an intensifying screen is used for energy conversion from x-ray radiation to light
• A prismatic bundle of fibre optics conveys the light to a CCD detector
• The use of conical fibre optics makes it possible for the system to have a sensitive area on the intensifying screen approximately 17 x 26 mm² despite the smaller size of the detector
• The fibre optics limit the minimum thickness of the detector to approx. 14 mm

​

RVG device is composed of 3 major components:

1. The "Radio" part consists of conventional x-ray generator connected to a highly precise micro processor timer for a very short exposure times and an anatomically adapted sensor with rounded edge.

2. The "Visio" part of the RVG unit stores the incoming signals during exposure and converts them point by point into one of 256 discrete grey levels

3. The "Graph" part of RVG unit consists of a digital mass storage unit that can be connected to various video printout devices or direct photographs of the screen may be made to provide opportunity to access the radiographic information further

ADVANTAGES :

• The RVG system is able to produce -radiographic images immediately after exposure and at considerably lower dose than necessary for x-ray films.
• Image manipulation is possible with the ability to cause contrast enhancement or gray scale reversal.
• Necessary magnification is possible

DISADVANTAGES :

• Decreased image resolution and contrast as compared with conventional films

• Applications :

1. Caries Detection occlusal & secondary caries

2. Detection of periodontal bone lesions-

even 5% bone loss

3. Used in the endodontics for assessment of

canals and better visualization of root canals

4. Periapical lesions, periapical bone loss and

resorption of roots are better visualized

DIGITAL SUBTRACTION RADIOGRAPHY

• Subtraction technique is useful mainly to detect subtle differences between radiographs made of same structures at different times
• Technically it is an image enhancement method that removes the structured noise from the image
• SR accomplished by removing or subtracting all the information that is unchanged from the two images, the result is a third image, the subtracted image, that portrays only the differences between first two images

• DIGITAL PANORAMIC RADIOGRAPHY:

1. To view the entire upper and lower arches

2. To know the exact extent of the lesions

3. Used in the assessment of orthodontic treatment.

4. Used in the determination of the height of the

alveolar bone

5. Used to assess the osteo-integration of implants

6. TMJ view can be better visualized in digital panoramic images.

7. Process of healing of fractures can be better assessed

THANKYOU..!