radiography chapters 8,19,27

basic concepts of digital imaging

• Used to record dental 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

terminology

• 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

purpose and use of digital imaging

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

• 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

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

• To aid in the development of a clinical treatment plan

fundamentals of digital imaging

• A method of capturing an image using a sensor, breaking it into electronic pieces, and presenting and storing the image using a computer

• Image used to describe the pictures that are produced

• A sensor placed inside the mouth

• The electronic signal is digitized

digital imaging radiation exposure

• Digital imaging requires less x-radiation exposure than film-based imaging

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

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

quiptment required for digital imaging

• X-ray unit

• Sensor

  • Charge-coupled device (CCD)

  • Complementary metal oxide semiconductor/active pixel sensor

  • Charge injection device

• Computer

x-ray unit used for digital imaging

• Most digital imaging systems use a conventional dental x-ray unit as the x-radiation source

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

snsor

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

  • Wired

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

  • Wireless

    • The imaging sensor is not linked by a cable

    • Most popular types of direct sensor technologies

      • Charge-coupled device (CCD)

      • Complementary metal oxide semiconductor/active pixel sensor

charge-coupled device (CCD)

• 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

• Pixel

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

  • 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

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

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

  • The chip is less expensive to produce and offers greater durability than the CCD

computer

• 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

• Has split screen and magnification capability

types of digital imaging

• Direct digital imaging

• Indirect digital imaging

  • Scanning traditional images

  • Storage phosphor imaging

direct digital imaging

• Components include an intraoral dental x-ray unit, a sensor, and a computer with imaging software

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

  • The sensor captures the image and transmits it to the computer monitor

  • Software is used to enhance and store the image

indiraect digital imaging

• Components include a CCD camera and a computer

  • An existing x-ray film is digitized using a CCD camera

  • The image is displayed on a computer monitor

storage phosphor imaging

• A wireless digital imaging system

  • This is a reusable imaging plate coated with phosphors 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

intraoral sensor preparation

• 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

  • Rubber finger cot may be placed underneath the disposable barrier sleeve to further protect the wired or wireless sensor, and to prevent cross-contamination

intraoral sensor placemet

• 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 exposure method

advantages. of digital imaging l

• Superior gray-scale resolution

• Reduced exposure to x-radiation

• Increased speed of image viewing

• Lower equipment and film cost

• Increased efficiency

• Enhancement of diagnostic image

• Effective patient education tool

• Eco-friendly tool

disadvantages of digital imaging

• Initial set-up costs

• Image quality

• Sensor size and thickness

• Infection control

• Wear and tear

• Legal issues

basic concepts of paralleling technique

• technique is also known as:

  • Extension cone paralleling technique

  • Right-angle technique

  • Long-cone technique

terminology

• Parallel

• Intersecting

• Perpendicular

• Right angle

• Long axis of the tooth

• Central ray

principles of paralleling technique

• The receptor is placed in the mouth parallel to the long axis of the tooth being radiographed

• The central ray of the x-ray beam is directed perpendicular to the film and the long axis of the tooth

• A beam alignment device must be used to keep the receptor parallel with the long axis of the tooth

• Object-receptor distance

  • Must be increased to keep the receptor parallel with the long axis of the tooth

• Target-receptor distance

  • Must be increased to ensure that only the most parallel rays will be directed at the tooth

beam alignement devices and recpetor holding devices

• A device used to position the receptor in the mouth and retain the receptor in position during exposure

• Examples of commercially available intraoral beam alignment devices

  • Rinn XCP Extension Cone Paralleling System

  • Rinn XCP-ORA One Ring & Arm Positioning System

  • Rinn XCP-DS FIT Universal Sensor Holder

  • Rinn Flip-Ray System

  • Rinn Snap-A-Ray Holder

  • Stabe Bite-block

  • Rinn XCP Extension Cone Paralleling System

    • Three plastic bite-blocks

    • Three plastic aiming rings

    • Three metal indicator arms

  • Rinn XCP-ORA One Ring & Arm Positioning System

    • One ring

    • One arm

    • Rinn XCP-DS FIT Universal Sensor Holder

      • Bite-block that includes self-adjusting clip that stretches to accommodate size of digital sensor

    • Rinn Flip-Ray System

      • Rotating bite-block

      • Ring

    • Rinn Snap-A-Ray Holder

      • Comes in two versions (one for film and one for digital sensors)

Recetptors used for paralleling technique

• Size 1 receptor

  • Used in the anterior region

  • Long portion in the vertical direction

• Size 2 receptor

  • Used in the posterior region

  • Long portion in the horizontal direction

rules of paralleing technique

• Receptor placement

• Receptor position

• Vertical angulation

• Horizontal angulation

• Film receptor exposure

patient prep

• Procedure

  • Explain the procedures

  • Adjust the chair

  • Adjust the headrest

  • Place and secure the lead apron

  • Remove all objects from the mouth

equiptment prep

• Set the exposure control factors

• Open the sterilized package containing the beam alignment devices, and assemble the devices over a covered work area

exposure sequence for receptor placements

• Anterior exposure sequence

  • Size 1 receptor is small and easier for patient to tolerate

  • Less likely to cause patient to gag

  • Total of 7 anterior placements using the size 1 receptor

    • 4 maxillary exposures; 3 mandibular exposures

• Posterior exposure sequence

  • 8 posterior placements

    • 4 maxillary exposures; 4 mandibular exposures

receptor placement for paralleling technique

• The specific area where the receptor must be positioned before exposure

  • Dictated by teeth and surrounding structures

• Specific placements described in the chapter are for 15-receptor periapical series using size 1 receptors for anterior exposures and size 2 receptors for posterior exposures

modifications in paralleling tecnique

• Shallow palate

• Bony growths

• Mandibular premolar region

shallow palate

• Cotton rolls

  • Two cotton rolls can be used, one placed on each side of the bite-block

• Vertical angulation

  • The vertical angulation can be increased by 5 to 15 degrees

bony growth

• Maxillary torus

  • The receptor must be placed on the far side of the torus and then exposed

• Mandibular tori

  • The receptor must be placed between the tori and the tongue and then exposed

mandibular premolar region

• Receptor placement

  • The receptor must be placed under the tongue

• Film

  • The lower edge of the film can be gently softened to prevent discomfort

advantages of paralleling technique

• Accuracy

  • The image is free of distortion

• Simplicity

  • It eliminates the need to determine horizontal and vertical angulation

  • It eliminates chances of dimensional distortion

• Duplication

  • Comparison of serial images has great validity

disadvantages of paralleling twchnique

• Receptor placement

  • May be difficult

• Discomfort

  • Beam alignment device may cause discomfort

3 dimensional digital imagng terminology

• Cone beam computed tomography (CBCT)

• Cone beam volume tomography (CBVT)

• DICOM data

• Field of view (FOV)

• Multiplanar reconstruction (MPR)

• Plane, axial

• Plane, coronal

• Plane, sagittal

• Resolution, contrast

• Resolution, spatial

• Three-dimensional digital imaging

• Three-dimensional volume rendering

• Voxel

fundamentals of 3 dimensional digital imaging

• Three-dimensional digital imaging

  • A method designed to evaluate the oral-maxillofacial complex

  • Named because it uses a cone-shaped x-ray beam to acquire three-dimensional information

  • Source of radiation rotates around the head of the patient

  • DICOM images

    • These allow practitioner to see field of view in three dimensions

    • They are viewed in three planes: Axial plane, coronal plane, and sagittal plane

    • When viewed together images are referred to as “multiplanar reconstructed images”

    • They can be shared amongst dental professionals

3 dimensional digital imaging traning

• American Academy of Oral and Maxillofacial Radiology (AAOMR) recommends that CBCT images be interpreted only by a board-certified oral and maxillofacial radiologist

• Intersocietal Accreditation Commission (IAC) is a non-profit organization that has developed standards applicable to the minimal requirements for optimum patient care when using dental computed radiography

equiptment

• Specialized equipment

• CBCT machine

  • Comparable in size to a panoramic machine

  • Patient sits, stands, or is placed in a supine position

  • In one rotation, radiation and receptor capture field of view

• Computer

  • Accepts raw data and converts them into stack of axial images

  • Technique is completed during the data reconstruction process

• Viewing software

  • Allows dental practitioner to view axial, coronal, and sagittal images

common uses for three dimesneional imaging

• Greatly improve interpretation, diagnosis, and treatment planning of dental care

• Implant placement

• Extraction or exposure of impacted teeth

• Definition of anatomic structures

• Endodontic assessment

• Airway and sinus analysis

• Evaluation of temporomandibular joint disorders

• Orthodontic evaluation

• Evaluation of lesions and abnormalities

• Trauma evaluation

pateint prep for 3d digital imaging

• Patients may be asked to sit or stand or be placed in the supine position during radiation exposure

• Instructions are given to the patient before exposure to remove jewelry, eyeglasses, and removable dental appliances

• A guide may be placed in the patient’s mouth during the scanning process

• Some specialists may ask that the upper and lower teeth be kept apart

patient positioning

• Patient is instructed to remain still

• Scan times vary from 7 to 30 seconds

• Ergonomic head and chin supports have been designed for improved patient comfort

• Laser beams may be installed to help with proper alignment of clinical structures and to ensure correct anatomic positioning

Advantages of three dimensional digital imaging

• Lower radiation dose

• Brief scanning time

• Anatomically accurate images

• Ability to save and easily transport images

Disadvantages of three dimensional images