Image Receptors - For Dental Radiology Seminar

 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

The 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)

FIRST “FILM” • Glass plates – Break easily – Difficulty in storage – Expensive

• Cellulose Nitrate – Highly flammable – Easily torn

YEARS

CONCEPTS

PERSONS ASSOCIATED

1895

Discovery of X-rays

Prof. WC Roentgen

1896

First dental radiograph

Dr. O Walkoff

1913

First pre-wrapped dental films

Eastman Kodak Co.

1920

First machine-made films Eastman Kodak Co.

1955

Introduction of D-Films

1981

Introduction of E-Films

2000

Introduction of F-Films

Image Receptors can be classified based on the Diagnostic Technique : 1. X –Ray Radiographic Receptors

2. Specialized X-Ray Radiographic Receptors 3. Radiofrequency Waves Receptors

• The X-Ray Film is the image receptor system used in dental radiology. • The X-Ray Films are classified according to: A.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 Eekta 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. )

Intra-Oral Radiography

Bitewing

Periapical

Occlusal

Bisecting Angle Technique

Topographic

Paralleling Technique

Cross-Sectional

• 2 Digits separated by a Decimal Point LEFT DIGIT (THE TYPE OF FILM) RIGHT DIGIT (THE SIZE OF FILM) 1- Periapical Film 0 ,1, 2, 3, 4 2- Bitewing Film

3- Occlusal Film

• #0 : Children (PA &BW)

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

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

•#3 : Extra long BW •#4 : Occlusal

Periapical Films

Size 0 22x35mm

Child Projection

Size 2 31x41mm

Size 1 24x40mm Anterior adult projection

Standard Adult Projection

Bite Wing Films

Size 0 22x35mm

Child Projection

Size 1 24x40mm Anterior adult projection

Occlusal Films

57x76mm

Size 2 31x41mm Standard Adult Projection

Size 3 27x54mm Anterior adult

Sharpness

Speed Size Of Crystals

A Speed B Speed C Speed D Speed (Ultra Speed) E Speed (Ekta Speed) F Speed (InSight)

The 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.

• it shows the crowns and the interproximal alveolar bone of the both arches on the same film.

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

 These films are of two types: Non Screen Films and Screen Films.  Both are available in various sizes :

•Panoramic

•Lateral Jaw

•Cephalometrics

• TMJ

4 ¾” x 6 ½” 5” x 7” 6 ½” x 8” 8” x 10” 6” x 12” 10” x 12”

•Skull Views

red arrow = head of condyle

black arrow = glenoid fossa

X-rays

• 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 artifacts •Optimum temperature 50˚ to 70˚F and Rel. Humidity 30-50%

Direct Action Film Or Non Screen Film

Indirect Action Film or Screen Film

•Sensitive primarily to x-rays photons

•Sensitive primarily to light photons (Fluorescent Light)

•Used Intra-orally

•Used Extra-orally

•Periapical •Bitewing •Occlusal

•Lateral Oblique •Skull Radiographs •Panoramic Radiographs •All routine Medical Radiographs

Digital Receptors

Direct

Indirect PSP

Solid-State Sensors

CCD (Charged Couple Device)

CMOS (Complementary Metal oxide Sensors)

(PhotoStimulable Phosphorus State Plates)

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 extra oral images

Sensor

Plastic sleeve

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.

Model

Manufa cturer

Pixel Size (μm)

Technology Software

Bit Pixel

Width

Height

File Size (MB)

INSIGHT

KODAK

N/A

SILVER HALIDE

N/A

N/A

3.1cm

4.1cm

N/A

RVG 6000

KODAK

18.5 X 18.5

CMOS

KODAK WINDOWS 6.0.1

8

1200 PIXELS

1600 PIXELS

1.8

PSP VISTASC AN

DUERR

SCAN PITCH 12.5

IMAGE PLATE

DBSWIN V.3.3

16

2476 PIXELS

3195 PIXELS

UPTO 9.3

Results: • 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

• • • • • • • • • •

• • • •

DOSE REDUCTION IMAGE MANIPULATION CONTRAST ENHANCEMENT MEASUREMENT 3-D CONSTRUCTION FILTRATION TIME SAVING STORAGE TELERADIOLOGY ENVIRONMENT FRIENDLY

COST SENSOR DIMENSIONS CROSS INFECTION CONTROL MEDICOLEGAL

(JOURNAL OF ORTHODONTICS VOL.29, 2002, 66-69)

Technique

Source

Image Receptor

Computed tomography (CT)

X-Rays

Very Sensitive Crystal or Gas Detectors

Magnetic Resonance Imaging (MRI)

RF Waves

Special Purpose Receiver Coils

Scintigraphy

Radioactive compounds

Rectilinear Scanner and Gamma scintillation Camera

Diagnostic Ultrasound

Ultra- High Frequency Sound Waves

Transducers

•Hospital 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.

Some of the clinically relevant pathogens that can live on dry inanimate objects are as follows Haemophilus influenzae: Life span 12 days MRSA : Life span 7days-7months E. Coli : Life span 1.5hrs – 16months Strep. Pyogens : Life span 3days - 6.5 months Salmonella typhimurium: Life span 10 days- 4.5 yrs

(RADIOLOGIC TECHNOLOGY VOL. 81 NO. 6, July/August 2010)

• 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 person’s medical and dental records. •The future of digital imaging could include the testing and upgrade of X-Ray equipment and software on-line.

• 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