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Image receptorsPuneet ChoudharyFinal year BDSDayananda sagar college of dental sciencesContents Definition History Highlights in Image Receptors Classification Analog v/s Digital Intra-Oral Radiographs Extra-Oral Radiographs Digital Image Receptors Pathogens on Image Receptors Conclusion References

What is an Image ReceptorThe term Image Receptor refers to any device that changes the x-ray beam into visible image .

Film , Charged-Couple Device (CCD) or Complementary Metal Oxide Semiconductors (CMOS) sensors , or Phosphorescent Screen or a Special detector placed in a table or a Bucky diaphragm (used in direct digital radiography).(http://medical-dictionary.thefreedictionary.com)

HistoryFIRST FILM

Glass plates Break easilyDifficulty in storageExpensive

Cellulose NitrateHighly flammableEasily tornHighlights in History of Image ReceptorsYEARSCONCEPTSPERSONS ASSOCIATED 1895 Discovery of X-raysProf. WC Roentgen1896First dental radiographDr. O Walkoff1913First pre-wrapped dental filmsEastman Kodak Co.1920First machine-made filmsEastman Kodak Co.1955Introduction of D-Films1981Introduction of E-Films2000Introduction of F-Films

Commonly available filmsCLASSIFICATION Image Receptors can be classified based on the Diagnostic Technique :

X Ray Radiographic Receptors

Specialized X-Ray Radiographic Receptors

Radiofrequency Waves Receptors

The X-Ray Film is the image receptor system used in dental radiology.

The X-Ray Films are classified according to:

Their use : a. Intra-oral films i. Periapical films ii. Occlusal films (also called bite film/ topographical film) iii. Bite wing films b. Extra-oral films

B. The coating of emulsion : a. Single Coated : These produce better and sharper images but the exposure to the patient is more therefore mostly used in industrial Radiography.

b. Double Coated: These films have emulsion on both sides . Most dental films are double coated. These allows for less exposure to the patient.

C. The Speed of the film:

a. Slow films: these have very small grain of silver bromide and emulsion is on one side only. Therefore it gives better definition but the exposure required is more and are thus not routinely used. Their speeds are denoted by A, B, C.

b. Fast films: These have a larger grain size and the emulsion is on both sides. Their speeds are D-ultra speed E-ekta speed and F-ultra ekta speed.

c. Hyper speed G: This is a 800-speed film that can half the patient exposure without blurring image quality.

D. Packaging :

a. Single film packet

b. Double film packet: Two films are placed close to each other when they radiographed the second film serves as a duplicate.

E. Use, nonuse of screen: a. Screen Films: i. sensitive to blue light E.g.: calcium tungstate screens (Kodak X-Omat and Ektamat films) ii. Sensitive to green light E.g.: Rare Earth Screens (Kodak Ortho and T-Mat films)

b. Non-screen films

F. Barrier Envelopes

a. With barrier envelopes: these ensures that there is no gross contamination in the dark room.

b. Without barrier envelopes.

( From Textbook of Dental and Maxillofacial Radiology By Karjodkar 2nd ED. )

(THE JOURNAL OF CONTEMPORARY DENTAL PRACTICE VOL 3 - NO.4 - NOV. 15 2002)Intra-Oral RadiographyBitewingPeriapicalOcclusalBisecting Angle TechniqueParalleling TechniqueTopographicCross-SectionalIntra-oral RadiographyANSI Classification of Intraoral film type and sizes 2 Digits separated by a Decimal Point LEFT DIGIT (THE TYPE OF FILM)

1- Periapical Film

2- Bitewing Film

3- Occlusal Film RIGHT DIGIT (THE SIZE OF FILM)

0 ,1, 2, 3, 4 Intraoral Film Sizes #0 : Children (PA &BW)

#1 : Adults PA Anterior (Paralleling Technique) or Children (BW)

#2 : Adults PA (Anterior & Posterior) or BW or Children (Occlusal)

#3 : Extra long BW

#4 : Occlusal

Periapical FilmsSize 022x35mmSize 1 24x40mmSize 2 31x41mm

Child Projection Anterior adult projectionStandard Adult ProjectionBite Wing FilmsSize 022x35mmSize 1 24x40mmSize 2 31x41mmSize 3 27x54mmChild Projection Anterior adult projectionStandard Adult ProjectionAnterior adultOcclusal Films57x76mm

Composition of a Film

Composition of a Film

EmulsionIntraoral Film Speed A Speed B Speed C Speed D Speed (Ultra Speed) E Speed (Ekta Speed) F Speed (InSight) SpeedSize Of CrystalsSharpnessThe most effective means of reducing time of exposure the amount of radiation reaching the patient and the amount of radiation scattered to the dentist is using a higher speed of film.

Bite wing films it shows the crowns and the interproximal alveolar bone of the both arches on the same film.

Occlusal Film Shows large parts of Maxillary Arch and Mandibular Arch parts of maxilla and floor of mouth.

Extra-oral films These films are of two types: Non Screen Films and Screen Films.

Both are available in various sizes :

4 x 6 5 x 76 x 88 x 106 x 1210 x 12Panoramic

Lateral JawSkull Views

Cephalometrics

TMJ

Lateral Jaw

Lateral CephalogramPostero-Anterior (PA)

Panoramic

red arrow = head of condyle black arrow = glenoid fossaTMJ

X-raysIntensifying Screens

Layers of Intensifying Screens

Layers of Intensifying Screen

Light Crossover

Anti-CrossoverScreen Speed

Film Storage In a Refrigerator in cool and dry conditions Away from all sources of ionizing radiation Away from chemical fumes Boxes placed on their edges to prevent pressure artifactsOptimum temperature 50 to 70F and Rel. Humidity 30-50%

Direct Action Film Or Non Screen Film Indirect Action Film or Screen FilmSensitive primarily to x-rays photons

Used Intra-orally

Periapical Bitewing OcclusalSensitive primarily to light photons (Fluorescent Light)

Used Extra-orally

Lateral ObliqueSkull RadiographsPanoramic RadiographsAll routine Medical RadiographsDIGITAL IMAGE RECEPTORS ANALOG v/s DIGITAL

The term digital in digital imaging refers to the numeric format of the image content and its discreteness.

Conventional film images can be considered an analog medium in which differences in the size and distribution of black metallic silver result in a continuous density spectrum.

Digital images are numeric and discrete in two ways : 1) in terms of spatial distribution of the picture elements (pixels) and 2) in terms of the different shades of gray of each of the pixels.

A pixel is a small box or well into which the electrons produced by the X-ray exposure are deposited.

A pixel is equivalent of a silver crystal used in conventional radiograph.

As opposed to film emulsion that contains a random arrangement of silver crystals , a pixel is structured in an ordered arrangement.

Production of a Digital image requires a process called Analog to Digital Conversion (ADC). This consists of 2 steps : 1. Sampling 2. Quantization

An analog signal is a continuous electrical wave that varies in response to changes in the sound or image being transmitted. A digital signal is a sequence of pulses. The original information is converted into a series of ON/OFF signals (bits) before being transmitted, sort of like Morse code.

Why is digital better? Digital signals can be sent for longer distances and are less prone to interference than analog signals. And since a digital signal is just a string of numbers, it can be reproduced exactly, an unlimited number of times. By contrast, analog signals cannot be copied perfectly. Each copy of an analog audio or video recording will have deterioration.

Read more: http://askbobrankin.com/analog_to_digital_tv_conversion.html#ixzz1r6iZ9tdQ

Digital Radiography

Digital extra oral images

Charged Couple Device

Charged Couple Device

Charged Couple DeviceComplementary Metal Oxide Semiconductors

PSP (PhotoStimulable Phosphorus State Plates )

SensorPlastic sleeve

PSP (PhotoStimulable Phosphorus State Plates )

PSP (PhotoStimulable Phosphorus State Plates )

Digital Subtraction Radiography

(The Journal of Contemporary Dental Medicine, Vol. 3, number 4, Nov.15 2002) Performance comparison between Three Intra-oral image receptors of different technology :

The intra-oral radiographic receptors evaluated were : The Kodak Insight F speed class film, the Kodak RVG 6000, and the Duerr Vitascan Combi PSP system.For each image the total image quality score (TS) was derived.

ModelManufacturerPixel Size (m)TechnologySoftwareBit PixelWidthHeightFile Size (MB)INSIGHTKODAKN/ASILVER HALIDEN/AN/A3.1cm4.1cmN/ARVG 6000KODAK18.5 X 18.5CMOSKODAK WINDOWS 6.0.181200 PIXELS1600 PIXELS1.8PSP VISTASCAN DUERRSCAN PITCH 12.5IMAGE PLATEDBSWIN V.3.3162476 PIXELS3195 PIXELSUPTO 9.3Results: Vistascan exhibited the most extended useful exposure range , followed by RVG 6000 and Insight. RVG 6000 exhibited the largest TS values in all tube potential settings except 70kV where Vistascan performed better.Insight performed better than Vistascan only at 60kV and 63kV.Vistascan performed better at 66 and 70kV, Insight at 60and 66kV whereas RVG performed equally well at all tube potential settings, except than at 52 and 70kV

Conclusions : The performance of all receptors tested was greatly dependent on the exposure parameters and mainly on the kV-settings. Overall, the RVG 6000 offered the best image quality at doses somewhere in between those required by the insight and the Vistascan.

( E.Katsoni et al / Health (2011) 56-65 )Advantages & disadvantages of Digital ImagingADVANTAGESDOSE REDUCTIONIMAGE MANIPULATION CONTRAST ENHANCEMENTMEASUREMENT3-D CONSTRUCTIONFILTRATIONTIME SAVINGSTORAGETELERADIOLOGYENVIRONMENT FRIENDLYDISADVANTAGESCOSTSENSOR DIMENSIONSCROSS INFECTION CONTROLMEDICOLEGAL(JOURNAL OF ORTHODONTICS VOL.29, 2002, 66-69)Image receptors in Advanced imagingTechniqueSourceImage ReceptorComputed tomography (CT)X-RaysVery Sensitive Crystal or Gas DetectorsMagnetic Resonance Imaging (MRI)RF WavesSpecial Purpose Receiver CoilsScintigraphyRadioactive compoundsRectilinear Scanner and Gamma scintillation CameraDiagnostic UltrasoundUltra- High Frequency Sound WavesTransducersPathogens on Image ReceptorsHospital acquired infection (nosocomial infection) can cause major illnesses, and may also be fatal.

The leading cause of nosocomial infection is methcillin resistant Staphylococcus aureus (MRSA).

Image receptors are handled by many technologists per day and if the proper hand sanitizing and cleaning of cassettes, etc is not carried out the bacteria can colonize of these inanimate objects for days depending on the type of bacteria.

The CDC hand washing guidelines recommends that hands be washed after every patient. It also recommends the cleaning the image receptors and the radiographic cassettes in radiology.

Haemophilus influenzae: Life span 12 daysMRSA : Life span 7days-7months E. Coli : Life span 1.5hrs 16monthsStrep. Pyogens : Life span 3days - 6.5 monthsSalmonella typhimurium: Life span 10 days- 4.5 yrs

Some of the clinically relevant pathogens that can live on dry inanimate objects are as follows(RADIOLOGIC TECHNOLOGY VOL. 81 NO. 6, July/August 2010)Conclusion There has been a wide research on comparisons of the image receptors used.

The ALARA statement endorses that the doses should be As Low As Reasonably Achievable.

The technology now available now is paper free. It is theoretically possible to store clinical notes/ photographs/ radiographs/ and study models on disc and refer or consult online.

Research is continuing into the development of a credit card sized SMART CARD which could carry a persons medical and dental records.

The future of digital imaging could include the testing and upgrade of X-Ray equipment and software on-line.

References : Oral Radiology : Principles and Interpretation (6th Ed.) - Stuart. C. White , Michael J. Pharoah

Textbook of Dental and Maxillofacial Radiology By Karjodkar (2nd Ed.)

The Journal of Contemporary Dental Practice, Vol 3, Number 4, Nov 15, 2002

Journal of Orthodontics , Vol29, March 2002, 66-69

International Journal of Health Sciences By Qassim University, Vol 4 (2), Nov 2010

E. Katsoni et al / Health, Vol.3, No.1, 56-65, (2011)

Radiologic Technology VOL. 81 NO. 6, July/August 2010

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