GU Digital Radiography for Dentistry (Fall 2023) PDF

01-Dec-22 1  01-Dec-22 Course Title: Oral &Maxillofacial Radiology I Course Code:OMR212 Topic of Lecture :Digital Radiography Lecturer: Dr. Mushira Dahaba Post :Professor /Program Director F A C U L T Y...

01-Dec-22 1  01-Dec-22 Course Title: Oral &Maxillofacial Radiology I Course Code:OMR212 Topic of Lecture :Digital Radiography Lecturer: Dr. Mushira Dahaba Post :Professor /Program Director F A C U L T Y O F D e n t i s t r y T h e F u t u r e S t a r t s H e r e F A L L 2 0 2 3 Digital Radiography Presented by Prof.Mushira M.Dahaba Oral& Maxillofacial Radiology Department, Faculty of Oral and Dental Medicine , Galala and Cairo University 2  01-Dec-22 Objectives of the Lecture By the end of the lecture, the student should be able to :- 1-Identify difference between analog and digital image, 2-Describe all systems of DR. 3-Compare and contrast between PSP,CCD and film. 4-List applications od DR in dentistry 3  01-Dec-22 Image Receptors Dental images are produced when an object is exposed to x-radiation and the attenuated beam emitted from the object after exposure is received on specific image receptors. Image Receptors Films---------film-based analogue image Sensors, detectors, I mage plates-------Filmless digital image What Is A Digital Image? Matrix. Pixels. It is an image saved in a computer’s memory and is a presentation of a real image as a set of numbers that can be shared and manipulated by a computer. To translate the image into numbers ,it is composed of pixels(the picture elements) arranged in the form of a matrix. Each pixel is considered a digit by the computer. This digit has a color(gray shade) and has a specific position).First digital recetor was used in 1987 for intra-oral imaging. 4  01-Dec-22 Digitization It is any modality or method that creates an image that can be viewed and stored on a computer The electrons that form the electronic image detector are divided into blocks or picture elements called pixels. A pixel is a “box” “well” into which the electrons produced by the x-ray exposure are deposited. A pixel is = digital equivalent of a silver crystal of a film used in conventional imaging. In comparison to conventional film emulsions that contain random arrangement of silver crystals, a pixel is structured in an ordered arrangement. 5  01-Dec-22 Analogue Vs Digital Images Analogue images are produced on dental films and depicted by varying continuous gray shades between the extremes of black &white. Digital image is composed of discrete units of digital information called pixels or picture.They are produced on sensors (CCD,CMOS), image plates or detectors and have varying shades of gray. Analog Vs Digital Images A film is considered as an analog medium; differences in size and distribution of metallic silver results in a continuous density or tone. Digital images are numeric and discrete(separate not continuous): there is spatial distribution of the pixels(picture element)+ there are different shades of gray of each pixel. Each pixel has a row and column coordinate in a matrix, this identifies its specific location in the matrix. 6  01-Dec-22 Analogue Vs Digital Images Analogue images are produced on dental films and depicited by varying gray shades between the extremes of black &white. (these color shades of the image are also referred to as continuous tone image). Digital image is composed of discrete units of digital Information called pixels or picture elements Each pixel carries information about the Digital image is both object ,which is quantified by the computer Discrete anD numeric. in order to produce a digital image. -Each pixel has a column and a row co-ordinate that identify its location in the matrix.. -Each pixel has a value representing degree of brightness of this image. Analogue Vs Digital Images Analogue Image----- received and displayed on a conventional dental film Digital Image----- received on a sensor and displayed on a computer’s monitor 7  01-Dec-22 Why Do We Do Digitization? DR-making the most of your image Limitations of Enhancing CR Diagnostic Qualities Limitations of Conventional Radiography? Variations Disease in Chem 50- 60% Progress Projection Proc. Bone Geometry Loss Sol. Struct. Higher Noise Rad Dose. Static Image Time Consuming 2-D Image 8  01-Dec-22 DR Systems DDR IDR (Filmless) (Film-based) Digital radiography Indirect Direct Semi-direct (Film) (CCD-CMOS-CID) (PSP) 9  01-Dec-22 Indirect acquisition A digital image can be produced by scanning conventional radiographs after being chemically processed using :  Scanner  transparency adaptor, Or  camera These digitizing systems will transfer the anlog image to a computer where an A-D-C converts the analog image to a digital image. This image can then be manipulated on a computer. Indirect Digital Radiography(Analog to Digital Conversion) 10  01-Dec-22 Advantages Digital image enhancement Sharing images with other specialists. (Teleradiography) Disadvantages Longer time Processing step still exists Films are still used. No reduction in radiation dose Indirect Digital Radiography Analogue Digital Digitization Image Image 11  01-Dec-22 Direct Digital Radiography In this imaging modality, the radiographic film is replaced by a sensor or an imaging plate. They are characterized by Instant Viewing of the image. Can be Used for Intraoral and Extra-oral Views No chemical processing is required Reduction in radiation dose. 12  01-Dec-22 Digital Image Acquisiton – Direct digital imaging – Immediate display on a monitor(without any external device) Charged coupled device Complimentary metal oxide semi conductor active pixel sensor (CMOS-APS) Charge injection devices (CID) – Semi direct imaging – Scanning with laser first and then displayed on a monitor Phosphor storage plate PSP RVG(One of the CCD Systems)(Simple Sum up for PRINCIPLE) 1-Rare-earth intensifying or scintillation screen 2-Fiber –optic system 3-CCD chip 4-Flexible cable 1-X-ray photons reaching the sensor are converted to light by the screen. 2-This light is picked by fiber optic system then to the CCD/CMOS which converts light into electrical charges which once reach the computer , the A-D-C produces a real time digital image on the monitor. 13  01-Dec-22 Image Formation in CCD-DDR Systems occurs through 3 main steps:  The incident x-ray energy is converted into light by a scintillator. The emitted light has to be bundled by an optical lens or optical fiber to fit the size of the CCD chip. CCD subsequently converts the light energy into electrical charges( electronic signals that are carried out by a cable called Analog electronic signal wire. The electronic signals are then transported to the "Analogue to digital converter" ( A-D converter) in the computer where digitization of the electronic signals takes place and a digital image is formed). CCD System (Charged Coupled Device) 14  01-Dec-22 Complementary Metal Oxide Semiconductor (CMOS) CCD, CMOS Merits “-Instant” image -Better resolution than PSP -More durable Limitation -Rigid and thick (3 to 8 mm)(not flexible) -Relatively and initially expensive -Most have wire connecting sensor to computer -Limited active area in comparison to PSP and film 15  01-Dec-22 Semi-direct Digital Radiography PSP All Sizes. 0,1,2,3,4 PSP (photostimulable phosphor) 16  01-Dec-22 Digora (most common PSP System) Plastic Sensor sleeve Digora PSP Systems These systems employ a re-usable photostimulable phosphor imaging plate(PSPP) instead of the film. The plates contain a layer of barium fluorohalide phosphor. The phosphor layer absorbs and stores the x-ray energy emitted from the object(latent image formation) The image plate is then placed in a reader where it is scanned by a laser beam. The stored x-ray energy in the plate is released as light which is detected by a photomultiplier system. This information is then sent to a computer where an A-D- C changes the analog image which is displayed as a digital image on the monitor. 17  01-Dec-22 Digora PSP Systems-Semidirect DR These systems employ a re-usable photostimulable phosphor imaging plate(PSPP) instead of the film. The plates contain a layer of barium fluorohalide phosphor The phosphor layer absorbs and stores the x-ray energy emitted from the object in the form of a latent image.. The image plate is then placed in a laser reader where it is scanned by a laser beam. The laser reader makes the stored x-ray energy in the plate to be released as light which is detected by a photomultiplier system and converted to an analog signal. The signal is then relayed to a computer and and A-D-C displays and processes the image as a digital image on the monitor(1-5 mins according to every manufacturer).Then the image is erased by a halogen lamp and is ready to be reused again. PSP: Photostimulable Phosphor Merits Patient friendly; no change in technique More film sizes to choose from Plates relatively inexpensive ($35+) Wider active area than CCD Limitation Easily damaged More time consuming (laser scan) Less resolution than film and CCD. The plates should be processed directly after exposure as they loose 23% of trapped electrons in first ½ hour & 30% in first hour.. 18 01-Dec-22 19  01-Dec-22 Methods of scanning of phosphor plates : A- Rotating plate scanning. B- Stationary plate scanning. Rotating plate scanner Movement during scanning affect resolution and produce more noise. 20  01-Dec-22 CCD PSP FILM Pros & Facilities of Digital Radiography 1- Time saving in comparison to conventional imaging Reduce the long processing time of conventional radiography to seconds. 2- Decreased exposure time (80-90-% reduction in intra-oral digital imaging and 40- 50% reduction in extra-oral digital imaging) 3-Better presentation for patient education,understanding and acceptance of treatment plan. 4-Storage,Archiving and Recall Once stored in a digital format, critical image data can be deleted , modified and recalled 5-Image Compression Process of file reduction.To reduce computer storage space and facilitate image retrieval and transmission. 21  01-Dec-22 6-Teleradiography(distant communication and consultation)and Quick Image Sharing IT’s the transmission of radiological patient images, such as x- rays, CTs, and MRIs, from one location to another for the purposes of sharing studies with other radiologists and physicians. This has the advantages of not losing radiographs in the post and saving time if an urgent appointment is required. 7-Environmental Friendly No processing chemicals are used or disposed of. Both CCD sensors and the PSP plates are capable of being reused for many thousands of exposures. They can, however, become scratched and damaged if not handled carefully. No hazardous effects of lead or silver from the conventional films No need for space occupying darkrooms or costly dryers and daylight loaders. 22  01-Dec-22 8- Fewer files cluttering office space 9- Sensors are available in various sizes 10- Image enhancement and manipulation by software tools (but we can't enhance any technique errors as cone cut or dropped sensor corner) thus decreasing the need of retake and increasing diagnostic capabilities 1-Pseudo-Coloring 23  01-Dec-22 2-Zooming ,Magnification and Flaslighting Zooming and highlighting specific areas Magnification of image in selected area of panoramic image to reveal any abnormalities in bone prior to construction of removable prosthesis. 3-Measuring Tools ;Linear ,angular and Relative Radiometric 24  01-Dec-22 contrast brightness 4-Adjust brightness, contrast 25  01-Dec-22 6-Combining intraoral/radiographic data, Notes (problem, cost, etc.) 7-Pseudo 3D 26  01-Dec-22 8-Negative Conversion 9-Image Analysis using Digital Subtraction: It is done by serially taken two radiographs of the same area in the mouth at the different time intervals. The first image can be subtracted from the second one to identify changes that may have occurred during a certain time period. First image is the baseline image(pre- operative or immediate post operative and second image is the post operative image after a period of time) 27  01-Dec-22 Quantitative DS When nothing has happened in the healing area, the result is zero. When bone loss or bone gain has occurred in the meantime, the result will be different from zero. When there is bone gain (less radiolucent, lighter area in the image, higher pixel gray value in the second image) the outcome will be a value above zero. In case of bone loss, the result is the opposite and a value below zero will be the outcome. Qualitative DS The screen shows a neutral gray in places where nothing has happened. It is darker where material has disappeared and brighter where the amount of tissue or material has increased. 28  01-Dec-22 DS Subtraction radiography. The image to the right is the result of the subtraction of the second image from the first image. Note the dark area indicating bone loss (red arrow) that was not visible on the original image. DS(Geometric Standardization is a Must as well as Exposure Parameters Standardization 29  01-Dec-22 Cons & limitations 1 – higher initial investment Cost - these digital systems are expensive! Furthermore, the sensors for direct sensor systems are very costly and do not come with guarantees for replacement. Cons & limitations 2 – Sensor thickness Discomfort - direct sensor is quite a bit thicker than a traditional film x-ray. Some patients will have trouble tolerating these larger devices. Inaccessible in some areas Active area limitation in CCD.Recently ,they got rid of the cable and got rid of scintillation screen by making the silicon CCD chip more sensitive to x-rays than light thus decreasing the bulk and removing the annoying cable. 30  01-Dec-22 Cons & limitations 3- The cable attached to the sensor is easily damaged 4- Sensor cannot be autoclaved (sterilized) For infection control, a plastic sleeve is fitted over the sensor and part of the cable. Resolution 31  01-Dec-22 Clinical Application of DR in Dentistry Image enhancement and manipulation by software toolscould be applied in all fields of dentistry DR in Prosthodontics Patient’s card, filing system and tool box of one of the 2D-DR soft wares. 32  01-Dec-22 DR in Implantology,why shift from CT to 2D-DR? A CT image for an implant with massive metallic artifacts Linear Measurements for radiographic bone height assessment before Implant Insertion Radiographic height is assessed relative to a reference of known dimensions; metal balls. Standardized measurements are calculated from tangents drawn to the top of the reference tangents drawn to the top of the vital landmarks to assess the height of bone available for implant insertion. 33  01-Dec-22 Linear Measurements for radiographic bone height assessment after Implant Insertion Radiographic height is assessed relative to a reference of known dimensions; metal balls. Standardized measurements are calculated from tangents drawn to the top of the implants to the highest seen AC. 34  01-Dec-22 Radiometric Measurements for radiographic bone density assessment; using the area tool measurements supplied in the tool box in mean gray value(pixels) after surgical intervention.This is relative density DR in TMJ Examination. 35  01-Dec-22 Digital tomograms analyzed using a special software to assess TMJ changes following therapy. Orthodontics;Automated cephalometric landmark identification is an example, other dental examples include caries detection, classification of periodontal disease, detection and quantification of other bone lesions. 36  01-Dec-22 Purchasing a digital Radiography System CCD ~ VS ~ PSP POC CCD PSP Thickness Greater Thickness = Greater x ray Decrease thickness = absorption = faster image Greater patient comfort Connection Direct cable connection = Machine in No direct connection = same room or Cordless machine in different room Noise More Less Distortion Higher Lower Time Real time image No real time, 20 sec delay Active area Decreased (limited) Increased Resolution Increased Decreased Sensitivity Greater = Decrease dose Less 37  01-Dec-22 Conventional Radiography (FSR) Vs Digital Radiography (DDR/Semi Direct) FSR (Film-based System) DR (Filmless-System) 1-The film acts as the medium for 1-The electronic detector acts as the acquisition of images. medium for acquisition of images. 2-The film acts as the medium for 2-The computer’s monitor acts as display of images. the medium for display of images. 3-The film acts as the medium for 3-The computer’s memory acts as storage of images. the medium for storage of images. 4-Acquisition, display, and storage 4-Image acquisition, processing, of images are done by the same display, and archiving—are medium “ film “ which increases individual and separate and the the possibility of loss of some performance of each can be information during image optimized individually for formation. maximum efficiency. 5-Differences in the size and 5-The term digital in digital distribution of black metallic silver imaging refers to the numeric in films result in a continuous format of the image content and density spectrum; images can only its discreteness; images can be be qualitatively evaluated quantified; quantitative evaluation Conventional Radiography (CR) Vs Digital Radiography (DG) CR (Film-based System) DR (Filmless-System) 6-Images cannot be changed in 6-Post-acquisition manipulation of contrast once they have been the Image ; thus avoiding second processed; the only way for exposure (retaking of the image). correction is a second exposure. 7-Long term storage and retrieval 7-Images can be stored on PACS of film is difficult.; CR is not and easily retrieved at a later date compatible with the picture if required. Images can be archiving and communication accessed from any terminal and systems (PACS) by multiple users (telecommunication). 8-Messy Chemicals, needs a 8-Dry processing; no darkroom, no darkroom or daylight loader. chemicals 9-Time consuming 9-Time saving 10-More exposure dose 10- Reduction in exposure dose 11-Film is used once 11- Electronic image receptors are reusable. 38  01-Dec-22 Q ? U ? E ? S ? TI ? O ? N ? S ? ? thank You 39