Maxillofacial imaging receptors/ dental courses

MAXILLOFACIAL
IMAGING RECEPTORS
INDIAN DENTAL
ACADEMY
Leader in continuing
Dental Education
www.indiandentalacademy.com

INTRODUCTION
• When a x ray beam passes through a pt differential
attenuation of x rays by the tissues occur
depending on part being examined.
• Receptors device that receives & records image.
• The image produced by X-rays may be captured on a
film, may be viewed directly (fluoroscopy) or on a
monitor with digital radiology.

HISTORY
• The first X ray detector was the
barium platinocyanide plate used by
Sir Wilhelm Conrad Röentgen in his 1895 experiments
in which he viewed his own hand fluoroscopically.
• To make permanent records of his experiments he
used a film of silver halide photographic emulsion to
radiograph his wife hand

First nobel prize in physics was awarded to him in
1901

• 14 days after discovery of x rays Friedrich Otto
Walkhoff took the first dental radiograph.
• He used an glass plate coated by hand with
photographic silver emulsion as receptor.
• Wrapped it in a rubber dam, held it in his mouth
between his teeth and tongue.

RECEPTORS
CONVENTIONAL
DIRECT
EXPOSURE FILMS
INDIRECT
EXPOSURE FILMS
WITH SCREENS
DIGITAL
SOLID STATE
DETECTORS
STORAGE
PHOSPHORS

DENTAL X-RAY FILM

FILM BASE
• Initially glass plate was used as base
• In 1914 - Cellulose nitrate base
• It was quite flammable
In 1924 safety film – cellulose triacetate
Emulsion would crack & peel away
from base when chemicals were too
hot
RETICULATION

• 1n 1960 – polyester base was developed
• Polyster polyethylene terephthalate ( 0.18 mm)
• Support the emulsion
• Flexible , dimensionally stable
• Uniformly translucent, cast no pattern
• Should not absorb too much light when
radiograph is viewed
• Blue tint is added

EMULSION
Two principal components
1.Photo/ radio sensitive silver halide grains
2.Vehicle matrix :
• Gelatinous / non gelatinous
• Even dispersion of Ag-halide grains
• Ensure better adhesion of emulsion to base
• Absorbs processing solutions, allow them to reach
and react with Ag-halide crystals

• Silver halide grains ( 1 to 1.5 microns) – crystal form
• Contains Ag+ , Br - / I- arranged in cubic lattice
• 90 to 99% silver bromide
• 1 to 10% silver iodide – added to create
imperfections
• Some silver ions moves
into lattice – interstitial Ag+

• Crystals are chemically sensitised by adding sulfur
containing compounds like allylthiourea
It reacts with ag halide – forms silver sulfide
• Usually located on
surface of crystal
sensitivity speck

Single Emulsion :
• Better image detail
• But less dimensional stability
Double Emulsion Film :
• Advantages: less radiation is required to produce
exposure ( ½ exposure)
• Dis. Adv : image is created on both emulsions -
superimposed – slight blurring of edges

DIRECT EXPOSURE FILM/
NON SCREEN FILMS
• Exposed directly to x- rays
• Commonly used for io
• Require more exposure factors
• Prolonged processing time
• Relatively thicker emulsion
• Image detail is excellent

INTRAORAL FILM PACKET
Outer plastic wrapper
Protects film from light,
saliva, mechanical damage
Identification dot
Used for film orientation
Film is encased in protective
black paper wrappers
Protects film base from light,
saliva, damage during opening
Lead foil
Shields film from
back scatter radiaion
Reduces pt exposure
Embossed pattern

FILM SIZES FOR IOPAR
O
1
2
22 x 35 mm
Small children
31 x 41 mm
Standard film size
for adults
24 x 40mm
Children
Anterior teeth

BITE WING VIEW
• Size 0, 1 in children
• Size 2 – for adults
• 27 x 54 mm
Extended size
bitewing

OCCLUSAL VIEW
• Used to visualise large areas of maxilla &
mandible
57 X 76
THREE TIMES LARGER
THAN SIZE 2

SPEED
• Radiographic speed refers to amount of
radiation required to produce an image of
standard density.
• Expressed as reciprocal of exposure in
roentgens required to produce an optical
density of 1 above gross fog
• Speed is controlled by size & shape of
Ag-halide crystals & silver content.

FILM SPEED GROUP SPEED RANGE (
RECIPROCAL OF
ROENTGENS) (1)
ISO speed group
classification for dental
films (2)
A 1.5 - 3
B 3 - 6
C 6-12 7.0 to 14.0
D 12-24 14 to 28
E 24-48 28 to 56
F 48-96 56 to 112
1. National Council On Radiation Protection And Measurements,
Report No 145, Appendix E, 2004
2. Ludlow, Platin, Mol. Characteristics Of Kodak Insight , An F-speed
Intra Oral Film. OOOE, 2001, 91: 120-129

D /
ULTRA SPEED /US
E P / EKTA PLUS
FILM / INSIGHT
F/ INSIGHT
GLOBULAR AG- HALIDE
CRYSTALS
DIAMETER : 1.0MICRO
METER
T- GRAIN EMULSION
FLAT TABULAR CRYSTALS
1.8 MICRO METER.
T- GRAIN EMULSION
FASTEST FILM
IODIDE IS PRESENT IODIDE IS ABSENT IODIDE IS ABSENT
OPTIMAL DOSE – 0.5 Gy 0.25 Gy , 30 to 50% < D DOSE 70% < D, 20% < E

Conventional
silver-halide
crystals are
pebble
shaped
KODAK
T-GRAIN
Emulsion
crystals
Are flat
INSIGHT
ULTRA
SPEED
Coating weights per film side (mg/Cm2 )
Film type Silver Bromide Iodide Emulsion vehicle Overcoat vehicle
Insight (F) 0.8-1.1 0.6-0.75 0 0.6-0.8 0.1-0.2
ULTRASPEED (D) 0.6-0.9 0.6-0.75 0.0-O.02 0.4-0.7 0.1-0.2www.indiandentalacademy.com

Fast film requires relatively low exposure to
produce an optical density of 1…
Slope of curve – contrast
Speed – location of
curve on log exposure
scale

PACKAGING :
• Single film packet
• Double film packet
• SELF DEVELOPING FILMS

SCREEN FILMS
• Used for extraoral views
• manufactured with dyes in the emulsion that absorb
specific wavelengths of visible light.
• Always used in combination with intensifying screens.
( x rays to light )
Screen
Photon
Light
Film

• Light photons are absorbed by emulsion, only outer layer is
affected.
• so thin emulsion on 2 sides is preferred rather than thick
emulsion on one side.
On x ray exposure
Entire crystal
glows, not only
area exposed
&divergence of
light rays
Area of
exposure
on film >
original
area of
crystal
Less
resolution

• Standard silver halide crystals are inherently sensitive to uv,
violet, blue light ( 300-500nm)
SLOW SCREENS
• calcium tungstate
• Barium lead sulphate screens
FAST SCREENS :
• Rare earth screens ( 1970’s) emit light in green, yellow, blue,
ultra violet spectrum
• So sensitising dyes are added
• Green sensitive film – ortho film
• Red sensitive film – pan film (panchromatic)
Spectral sensitivity

Manufact
urer
Name phosphor Spectral
emission
film Speed
class
Du
pont
CRONEX PAR
SPEED
Cawo4
BLUE CRONEX 4 100
CRONEX HI
PLUS
Cawo4
BLUE CRONEX 4 250
QUANTA
DETAIL
YTaO4:Tm UV / BLUE CRONEX 4 100
QUANTA
FAST DETAIL
YTaO4: Nb UV/ BLUE CRONEX 4 400
KODAK
LANEX FINE
Gd2O2S:Tb
Neutral dye GREEN ORTHO G 100
LANEX
MEDIUM
Gd2O2S:Tb
Neutral dye
GREEN ORTHO G
250
LANEX
REGULAR
Gd2O2S:Tb
Yellow dye
GREEN ORTHO G 400

• Kodak ortho G film is replaced by T-Mat G film
• Can be used with all
green-emitting rare-earth
intensifying screens
such as Kodak Lanex screens
• Increased detail by reduced
crossover without a
change in film speed

CROSSOVER
To reduce crossover by
• adding a dye to the film base
• Changing shape of crystals.
• ( tabular)..increase light
absorption www.indiandentalacademy.com

Super HR-U is a high
contrast green sensitive
x-ray film for use with
green-emitting rare earth
screens. The New all-
around x-ray film for
general applications.

HIGH CONTRAST , MEDIUM SPEED FILMS – SKULL RADIOGRAPHY
FAST FILMS – LESS RADIATION EXPOSURE – PANORAMIC IMAGING
LESS CONTRAST, WIDE LATTITUDE – CEPHALOMETRY
Standard “inches”:
• 8” x 10”
• 10” x 12”
• 11” x 14”
• 14” x 17”
Metric:
• 18cm x 24cm
• 24cm x 30cm
• 30cm x 35cm
• 35cm x 43cm
FILM SIZES

• 1977- digital subtraction angiography,- first form of digi
imaging
• 1980 – computed radiography ( storage phosphor
plates)
• 1987 by Francis Mouyen - 1ST digital X-ray sensors for
use in dentistry.
• Radio Visio Graphy (RVG) By Trophy Radiologie
( Kodak Company, Rochester, N.Y. )
• Io use Storage phosphor plate in 1991
DIGITAL RECEPTORS

• SOLID STATE DETECTORS
• CHARGED COUPLE DEVICES (CCD)
• COMPLEMENTARY METAL OXIDE
SEMICONDUCTORS
• FLAT PANEL DETECTORS
• PHOTO STIMULABLE PHOSPHORS

• Electronic elements of a digital sensor are arranged in
a regular grid of rows and columns
• Pixel refers to the spatial
distribution of the
rectangular 2D
grid of sensor elements
• Each pixel has a row and
column that uniquely identifies its location in matrix.

Exposure of sensor with x rays
Release of electron from crystals
Production of electronic charge
each pixel of sensor, absorption of x ray
generate a small voltage
Fluctuation b/w minimum and max
Analog signal
ADC
SAMPLING
( small voltages are grouped
as 1 value)
QUANTIZATION
(Every sampled signal is
assigned a value)
Computer displays a shade
of gray according to no
assigned

Charged couple device
• Thin wafer of silicon - crystals are in pixel matrix
• On x ray exposure - covalent bonds b/n silicon atoms are
broken - e- hole pairs.
e- moves to most positive potential in device - "charge packets.“
( ~pixel)www.indiandentalacademy.com

Image is read by transferring each row of pixel charges from
one to other…Bucket brigade pattern. At end of row -
Transferred to read out amplifier – voltage – ADC

• RVG – by Trophy
• Sens-a-Ray by Regam
• Visualix by Gendex
• Flashdent by Villa
• Sidexis by Siemens
• CDR by Schick

Complementary metal oxide semi conductors
• Silicon -based , differ from CCDs in the way that pixel
charges are read
• Each pixel is isolated from its neighboring pixels and is
directly connected to a transistor.
• The voltage in each transistor can be addressed
separately, read by the frame grabber, and then
stored and displayed as a digital gray value

PHOTO STIMULABLE PHOSPHORS
• The emission by a substance of stored energy as light
is referred to as luminescence
• 1603 - chinese found Bolognese stone (barium
sulfate)which glowed persistently after exposure to
sunlight
• Consists of reusable imaging plate coated with
phosphor instead of sensor
• Flexible, fits into the mouth as a conventional film

Europium doped barium
fluoro halide
Red light
600nm
Trapped e-
~ x ray
exposure
When e-
returns energy is released
300-500nm(green)
Fiber optics
light – electric energy

• IO: barium fluorohalide material + polymer is
spread in thin layer on a polyester base
• Psp plates are available in standard io sizes
• panoramic and cephalometric imaging.

FEATURE FILM CCD / CMOS PSP
RADIATION DOSE higher lower lower
GENERATION OF
VISIBLE IMAGE
Chemical processing Computer computer, scanning
laser
IMAGE VIEWING delayed real time on
computer
delayed, computer
monitor
RESOLUTION 16 -20 lp/mm 8- 10 lp/mm 6-8 lp/mm
CONSTRUCTION thin, flexible thick, rigid thick, rigid
ACTIVE AREA entire surface of film smaller than size of
sensor
entire surface
LIFE SPAN one use reusable
> 10,000?
reusable
unknown
IMAGE
ENHANCEMENT
unchanged Multiple operations. Density, contrast,
magnification +, -
STORAGE pt record Variety of archiving methods, server,zip, cd

Flat panel detectors
• Larger matrix areas with pixel size less than 100µm
• Allows direct digital imaging of larger areas of body
• Two methods
• Indirect using intensifying screens – efficient
• Direct using photoconducting material ( selenium) – high
resolution

CONE BEAM COMPUTED TOMOGRAPHY
TWO TYPES OF DETECTORS
1.X RAY image intensifier tube coupled to ccd with a
fiber optic coupling
2. Flat panel detectors
Cesium iodide
scintillation
crystals
Photodiode
Thin film
transistor made of
amorphous silicon
X rays
Light
Electrical signal

X RAY image intensifier tube coupled to ccd with a fiber optic coupling

XERORADIOGRAPHY
• Electrostatic imaging tech that uses modified
xerographic copying process to record images produced
by x rays
• Selenium coated photo receptor which is uniformly
charged.
• Available in sizes of no.1 & 2 films
• On x ray exposure , selective discharge of charge occurs
• Proportional to radiation striking the plate.
• Charge pattern on plate – latent imagewww.indiandentalacademy.com

Xeroradiographic plate
++ + + + + + + + + + +
Greater charge beneath thick part,
as most radiation was absorbed
Thin part : penetrating radiation
dissipates more charge
At interface electrostatic forces are
distorted.resulting electric field
produce enhancement of edges.
•Periodontal and periapical assesment to show good bony details
•Sialography to show fine duct structures
•Cephalometry to show required soft and hard tissues on filmwww.indiandentalacademy.com

CT
X rays attenuated by
pt tissues
Captured by
detectors
Converted to light
Pmt/ photo diode Electric signal
Detector
electronics digital
signal
Image processor
Complex computational process
Real time, high resolution
images
Scintillation crystals

First two generations:
• thalium activated sodium iodide scintillation crystal
• Photo multiplier tube ( PMT)
Limitations :
• NaI hygroscopic
• Has long after glow, (long scan time )
• PMT are fairly big, so cannot easily fit into large array of
detectors in current ct

Third generation :
• Used xenon gas ionisation chambers
• Photon interacts with gas atom by ionizing atom
• Production of electron – ion pair (e- – anode)
• e- near anode produce electric current (signal from detector)
• Current is directly proportional to intensity of radiation.
• Dis adv : inefficiency
• Due to low density of gases , many photons pass through
chamber undetected.

Fourth generation :
• Scintillation crystals : Cesium iodide
• Bismuth germinate, Cadmium tungstate
• PMT are replaced by silicon photo diodes
• Photo diode converts light signal into electron
flow( current) that is proportional to intensity of
light signal
Adv: small size
• Greater stability
• Low cost

MRI
Receiver coil : a coil positioned within imaging volume & connected to
receiver circuit that is used to detect or receive mr signal.

• RF coils are used for transmitting energy and
receiving signals in MRI
Three categories: Transmit receive coil
• receive only coil & transmit only coil
• Volume coil
• Bird cage coil ( T/R)
• Quadratured coil
• Single turn solenoid
• Surface coil
• Surface coil NMR, saddle coil,
• Phased array coil, linear polarized coilwww.indiandentalacademy.com

surface coils
• Small coils designed to image restricted regions of pts
anatomy
• Variety of shapes, sizes, Can be applied to roi
• Has a good SNR for superficial tissues
Whole volume coils
• Used for surrounding either the whole body or a specific
region
• Used for the phantom of bigger volume
• Has better magnetic field homogeneity than surface coil

Z gradient – slice selection
Y gradient – phase
encoding ( divides slice
into horizontal rows)
X gradient – frequency
encoding (divides slice in
to vertical columns )

Ultrasonography
• Usg is a procedure that uses high-frequency sound
waves ( 1 to 20 MHz) to view internal organs and
produce images of the human body
Electric
impulses
high
frequency
sound
waves
Tissues
interact
with
different
acoustic
impedance
Sonic
waves
reflected
by tissues
as echos
electric
signal
Transducer
Transducer held
against body
Amplified, processed, displayed on a tv monitor/ oscilloscope
Received by Transducer

Electrodes behave as capacitators
Voltage b/n them produce electric field
Backing block : quickly dampens
vibrations
CRYSTAL VIBRATES AND GENERATES SOUND WAVES
Acoustic insulator : rubber/ cork
Prevents sound from passing into
housing
Plastic housing
Parts of transducer

Piezo electric crystals :
• Application of electric field cause a change in dimension – piezo
electric effect
• Piezo electric materials are made up of
inumerable dipoles in geometric pattern
• Barium titanate , lead zirconate titanate
Voltage
cause
realignment
of crystals
Sound
waves
Echos
carry
energy
Physical
compres
sion of
crystals
Induces
voltage
Us signal
Generation
Interacts with
tissues
Realign ment of
dipoles

Special films
Dry Laser films
• High Contrast, High Density Dry Processing Films are
designed for use in specific manufactures Imagers.
• They produce very highest diagnostic grayscale
hardcopy images.(D-Max greater than 3.0)
• low fog and excellent stability.
• Ideal for multi-modality imaging, including
Computed Radiology, CT, MRI, Digital X-Ray and
Ultrasound. www.indiandentalacademy.com

• DRY Laser emulsions are coated on both clear and
blue tinted polyester base.
• The films have a protective coat to provide maximum
protection from scratches and abrasions.

DUPLICATING FILM
• single emulsion film
• emulsion side- shiny, other side – dull
• used to make identical copy of io/eo film.
• Used only in dark room.
• Emulsion side must contact radiograph during
process
• A small photographic printer
with uv light is used.

CONCLUSION
• The limits of our senses were vastly expanded by the
fine work and the great sacrifices of dedicated pioneers,
not only in radiology , but also in physics, mathematics,
and engineering.
• By the second half of the 20th Century ,maxillofacial
radiologists had several great diagnostic tools that
expanded their abilities to examine. These devices
enabled physicians to reach precise diagnosis and to
produce excellent treatment plans

Although ego & economics drive our
every day lives, it is ideals & ideas that
build our future….

Maxillofacial imaging receptors/ dental courses

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Maxillofacial imaging receptors/ dental courses

Semelhante a Maxillofacial imaging receptors/ dental courses (20)

Mais de Indian dental academy

Mais de Indian dental academy (20)

Último

Último (20)

Maxillofacial imaging receptors/ dental courses

Notas do Editor