Recent Advances In
Imaging Techniques
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy....
Oral
Radiology
Lectures

Recent
Advances
In Imaging
Techniques
www.indiandentalacademy.com
Contents
•

Introduction

•

Importance of radiography in endodontics

•

Conventional techniques
Recent advances in imagi...
•
•
•
•
•

MRI
Cone beam computed tomography
Digital substraction radiography
Conclusion
References

www.indiandentalacade...
INTRODUCTION
We are sick of the roentgen ray ... you can see other people's bones with the
naked eye, and also see through...


X-rays has brought dentists
“out of the dark”, allowing
them to visualize areas not
accessible
by
other
diagnostic mean...
•

The advent of the first oral radiography equipment
permitted visualization for the first time of the changes
that occur...
Importance of Radiography in Restorative
and Endodontics
The three general areas of application are :
i. Diagnosis
ii. Tre...
Application of radiography in
endodontics
DIAGNOSIS
• Identifying caries

TREATMENT
•Determining
length

RECALL

working •...
Basics






Technology systems
- Traditional
- Digital
Traditional machines
- Long cone
- Short cone
Films
- Ultraspee...
Bisecting Angle Technique




This technique, described at the turn of the century by
Price and Cieszynski.
Principle:

...
Film holders or finger holding method


A. The Rinn bisected
angle instrument (BAI).



B. The Emmenix® film
holder.


...
www.indiandentalacademy.com


Horizontal angulation : CR directed
perpendicular throgh the curvature of the
arch and through the contact areas of the...
Improper vertical angulation

www.indiandentalacademy.com
ADVANTAGES




Positioning of the film packet is reasonably comfortable
for the patient in all areas of the mouth.
Posit...
DISADVANTAGES


The many variables involved in the technique often result in the image
being badly distorted.



Incorre...


It is not possible to obtain reproducible views.



Coning off or cone cutting may result if the central ray is not ai...
Paralleling technique


Described by Fitzgerald toward the end of
the 1940s

www.indiandentalacademy.com
Film holders
 A.
Hawe–Neos Superbite
posterior holder (colour coded
red).
 B.
Hawe–Neos Superbite
anterior holder (colou...
www.indiandentalacademy.com













Advantages
Greater geometric accuracy.
Reproducibility.
Less radiation dose (beam is not directed to...
Differences b/n bisecting and parallel angle
technique
Bisecting Angle Technique

Parallel Ray Technique

1) Details obscu...
Localization technique


Is a method to locate the position of a tooth or object in the
jaws



Purpose: To depict the B...
Buccal object rule


Described by Clark in 1910 and refined and amplified by
Richards in 1952 and 1980.



According to ...


With an orthoradial projection
(A) the two objects appear
superimposed.



With an oblique projection (B,
C), the two ...
Central (x-ray) beam passing directly through a root containing two canals
will superimpose the canals on the film. When t...
buccal root during endodontic treatment of a first
upper premolar with two roots

With the standard projection, the roots
...


If this technique is standardized so that the upper
premolars are always radiographed at a slight mesiodistal
angle, th...


DIGITAL RADIOGRAPHY



A digital radiograph consists of a number of pixels(picture elements)
and each pixel is the sma...
www.indiandentalacademy.com


Indirect system



Uses film like photo phosphor plates that are activated using X-rays,
then scanned in special devic...


Principle:



When X-ray beams are irradiated onto Imaging Plate (IP), the X-ray
energy is temporarily stored within t...


Merits:



No chemicals are required for processing.



No film and chemical waste disposal problem.



One of the m...


Ease of positioning the plates as compared to wired sensors used in
direct systems which are difficult to position espe...


Also because of the steps needed to obtain an image, the time needed to take
phosphor plate image is very close to the ...


Principle:



The computer chip which is a Charged Couple Device (CCD)
captures light information that is emitted by a...
Advantages of digital radiography
over conventional radiography :


Working time from image exposure to image display is ...
Radiovisiography


Introduced by Moyer et al in 1989.



Radio part- sensor – Exchangeable scintillation screen,
A fiber...
Digital Radiograph (RVG)
sensor head

object

x-ray
source
scintillator

CCD

fibre optic
layer

transmitter
converter
amp...
Radiovisiography


RVG comprises of four basic components:



An X-ray set with electronic time; an intra-oral sensor; a...


C) Edge detection (Laplacian)- enhances the edges within image but
eliminates detail from the rest of the time.



2) ...


4) Collimation -

Incorporating rectangular collimation to the

RVG sensor would therefore permit a further decrease in...


Demerits:



They are thicker than films and have cables running off the sensors which
some patients don’t tolerate we...
DIRECT DIGITAL SENSORS





CHARGE-COUPLED DEVICE (CCD)
COMPLEMENTARY METAL OXIDE SEMICONDUCTOR
ACTIVE PIXEL SENSOR (CM...


There are two types of digital sensor array designs: AREA AND
LINEAR.



Area arrays are used for intra oral radiograp...
X-RAY IMAGING WITH CCD
SCINTILLATOR
- converts x-radiation to photons
(light)
FIBRE OPTIC LAYER
- conducts photons to CCD
...
www.indiandentalacademy.com
Xeroradiography.


Records images without film.



Consists of image receptor plates –selenium particles.



Latent ima...


Improves visualization of files and canals.



Two times more sensitive than conventional D-speed films.



Disadvant...
DIGITAL SUBSTRACTION RADIOGRAPHY.


This is a technique by which stuctured noise is reduced in order to
increase the dete...


Standard radiographs-are produced with identical exposure geometry.



Reference/baseline image.



Follow up image-f...
Comparing baseline to follow up images made at 3,6,12 months following endodontic
therapy,
Column 3 indicates substracted ...


Applications



Useful in detecting progess of remineralisation and demineralisation
pattern of dentinal caries, diagn...
Computed tomography


Computed tomography (CT) has evolved into an indispensable
imaging method in clinical routine.



...


PRINCIPLE OF COMPUTED TOMOGRAPHY



In conventional CT, the X-ray tube and detector rotate around the
patient with the...
COMPUTED TOMOGRAPHY
Parts of the Equipment;
1.
Scanner ( movable x
ray table + gantry)
2.
Computer system
3.
A display con...
Fig. 4: Schematic illustration showing the continuous
relationship for different projection angles and related
apertures e...
RADIATION DOSAGE FOR CT

Radiation dosage

1.536 rad for
a single section
1.8432 rad for

multiple sections
Estimated dose...
ADVANTAGES


Eliminates the super-imposition of images of structures outside the
area of interest.



Because of the inh...


Excellent differentiation between different types of tissues both
normal and diseased



Images can be manipulated.

...
DISADVANTAGES


Need for contrast media for enhanced soft tissue
contrast.



Tissue non-specificity i.e. it does have a...


The equipment is very expensive.



Very thin contiguous or overlapping slices may result
in a generally high dose inv...




IMAGE RECONSTRUCTION
In CT a cross- sectional layer of the body is divided in to many
tiny blocks.



Each block is...
www.indiandentalacademy.com
Cone-Beam computed tomography


CBCT is an x-ray imaging approach that provides high
resolution 3-dimensional images of t...
www.indiandentalacademy.com


Advantages:



Precise identification and detection of periapical lesions.



Detection of mandibular canal.



Comp...


Micro – CT



Recently, micro-CTs, which essentially comprise a miniaturized
design of the cone beam CTs -typically us...




Micro-CT desk device of Sky-Scan Inc. at the
Institute of Medical Engineering.
The object to be examined is placed o...
TUNED APERTURE COMPUTED TOMOGRAPHY
(TACT)


Improve accuracy in caries diagnosis because of its 3-D or pseudo
3-D capabil...
Fig. 5: Arbitrary example of generalized TACT projection geometry applied to a simple cylindrical object.

www.indiandenta...


TACT useful in



Detection of caries and recurrent caries ,



Periodontal bone loss,



Periapical lesion localiza...
Magnetic Resonance Imaging
Principles:
Magnetism is a dynamic
invisible
phenomenon
consisting of discrete fields of
forces...


The technique is based on the presence of specific magnetic

Magnetic Resonance Imaging

properties found within atomic...
Equipment;
1.
The Gantry ;houses the
patient. Patient is
surrounded by magnetic
coils
2.
Operating console ;
where the ope...


When images are displayed; intense signals show as white and weak
ones as Black and Intermediate as shades of gray.


...
Advantages of MRI
•

It offers the best resolution of tissues of low inherent
contrast.

•

No ionizing radiation is invol...


Complications;



Magnetic forces and radio waves - not know to produce any
biological side effects in man.
Non invasi...












Indications
Assessing diseases of the TMJ
Cleft lip and palate
Tonsillitis and adenoiditis
Cysts and...
d) Ultra sound scanning.


Ultra high frequency sound waves are used.



The reflected sound waves are processed to elec...


US image produced - automatic movement of the crystal over the
tissue of interest.



As each movement gives one image...
CONCLUSION


New approaches to radiography have been and are being
developed.



These are unique; some will improve exi...
References
•

•
•
•

•
•
•

Dental radiography :principles and techniques by Laura
jansen ,Haring.4th edition
Textbook of ...
Thank you!

www.indiandentalacademy.com
Leader in continuing dental education

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Recent advances in imaging techniques/ /certified fixed orthodontic courses by Indian dental academy

  1. 1. Recent Advances In Imaging Techniques INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Oral Radiology Lectures Recent Advances In Imaging Techniques www.indiandentalacademy.com
  3. 3. Contents • Introduction • Importance of radiography in endodontics • Conventional techniques Recent advances in imaging techniques - Digital radiography - Xerioradiography - Computed tomography - TACT • www.indiandentalacademy.com
  4. 4. • • • • • MRI Cone beam computed tomography Digital substraction radiography Conclusion References www.indiandentalacademy.com
  5. 5. INTRODUCTION We are sick of the roentgen ray ... you can see other people's bones with the naked eye, and also see through eight inches of solid wood. On the revolting indecency of this there is no need to dwell. But what we seriously put before the attention of the Government... that it will call for legislative restriction of the severest kind. Perhaps the best thing would be for all civilized nations to combine to burn all works on the roentgen rays, to execute all the discoverers, and to corner all the tungstate in the world and whelm it in the middle of the ocean. EDITORIAL IN PALL MALL GAZETTE LONDON, 1896 www.indiandentalacademy.com
  6. 6.  X-rays has brought dentists “out of the dark”, allowing them to visualize areas not accessible by other diagnostic means. www.indiandentalacademy.com
  7. 7. • The advent of the first oral radiography equipment permitted visualization for the first time of the changes that occur in the bone surrounding the apices of non-vital teeth, as well as the results of endodontic therapy. www.indiandentalacademy.com
  8. 8. Importance of Radiography in Restorative and Endodontics The three general areas of application are : i. Diagnosis ii. Treatment iii. Recall  www.indiandentalacademy.com
  9. 9. Application of radiography in endodontics DIAGNOSIS • Identifying caries TREATMENT •Determining length RECALL working • Identifying new pathosis •Identifying pathosis superimposed •Moving •Determining root and pulp structures anatomy •Locating canals normal •Characterizing structures •Differentiating canals and periodontal ligament spaces •Evaluate healing •Evaluating obturation www.indiandentalacademy.com
  10. 10. Basics    Technology systems - Traditional - Digital Traditional machines - Long cone - Short cone Films - Ultraspeed film - Ektaspeed film (E –film) - F speed (faster film) www.indiandentalacademy.com
  11. 11. Bisecting Angle Technique   This technique, described at the turn of the century by Price and Cieszynski. Principle: www.indiandentalacademy.com
  12. 12. Film holders or finger holding method  A. The Rinn bisected angle instrument (BAI).  B. The Emmenix® film holder.  C. The Rinn Greene Stabe bite block.  D.The Rinn Greene Stabe bite block reduced in size for easier positioning and for use in children www.indiandentalacademy.com
  13. 13. www.indiandentalacademy.com
  14. 14.  Horizontal angulation : CR directed perpendicular throgh the curvature of the arch and through the contact areas of the teeth.  Vertical angulation : CR perpendicular to the imaginary bisector . www.indiandentalacademy.com
  15. 15. Improper vertical angulation www.indiandentalacademy.com
  16. 16. ADVANTAGES   Positioning of the film packet is reasonably comfortable for the patient in all areas of the mouth. Positioning is relatively simple and quick.  If all angulations are assessed correctly, the image of the tooth will be the same length as the tooth itself and should be adequate (but not ideal) for most diagnostic purposes.  Decreased exposure time (short PID) www.indiandentalacademy.com
  17. 17. DISADVANTAGES  The many variables involved in the technique often result in the image being badly distorted.  Incorrect vertical angulation will result in foreshortening or elongation of the image.  The periodontal bone levels are poorly shown.  The shadow of the zygomatic buttress frequently overlies the roots of the upper molars.  The horizontal and vertical angles have to be assessed for every patient and considerable skill is required. www.indiandentalacademy.com
  18. 18.  It is not possible to obtain reproducible views.  Coning off or cone cutting may result if the central ray is not aimed at the centre of the film, particularly if using rectangular collimation.  Incorrect horizontal angulation will result in overlapping of the crowns and roots.  The crowns of the teeth are often distorted, thus preventing the detection of approximal caries.  The buccal roots of the maxillary premolars and molars are foreshortened. www.indiandentalacademy.com
  19. 19. Paralleling technique  Described by Fitzgerald toward the end of the 1940s www.indiandentalacademy.com
  20. 20. Film holders  A. Hawe–Neos Superbite posterior holder (colour coded red).  B. Hawe–Neos Superbite anterior holder (colour coded green).  C. Rinn XCP posterior holder (colour coded yellow).  D . Rinn XCP anterior holder (colour coded blue) with film packet inserted.  E . Unibite posterior holder. www.indiandentalacademy.com
  21. 21. www.indiandentalacademy.com
  22. 22.          Advantages Greater geometric accuracy. Reproducibility. Less radiation dose (beam is not directed towards body trunk, finger not holding film). Superior images of upper molar roots,bone margins ,interproximal margins. A number of commercial devices can hold the film at varying distances from the teeth. Drawbacks Reduced sharpness and resolution. Image size distortion-magnification. www.indiandentalacademy.com
  23. 23. Differences b/n bisecting and parallel angle technique Bisecting Angle Technique Parallel Ray Technique 1) Details obscured by large penumbra 2) Superimposition of zygomatic process 3) Image shape distortion 1) Sharp details because of small penumbra 2) Control of the shadow of the zygomatic process 3) Slight image size distortion 4) Distortion greater in apical zone 5) Anatomical relationships altered 4) Distortion equal throughout the entire image 5) Correct anatomical relationships 6) Crown-root ratio not preserved 6) Crown-root ratio preserved 7) Poor image standardization and reproducibility 7) High image standardization and reproducibility www.indiandentalacademy.com
  24. 24. Localization technique  Is a method to locate the position of a tooth or object in the jaws  Purpose: To depict the B-L relationship or depth of an object .  Two methods :  Buccal object rule  Right angle technique www.indiandentalacademy.com
  25. 25. Buccal object rule  Described by Clark in 1910 and refined and amplified by Richards in 1952 and 1980.  According to this rule, when a radiograph is performed at a certain angle, the object closer to the radiographic source – the buccal object – is displaced in the radiograph in the same direction as the X-ray beam.  Stated more simply as INGLES RULE(MBD)-always shoot from mesial and buccal root will be to the distal. www.indiandentalacademy.com
  26. 26.  With an orthoradial projection (A) the two objects appear superimposed.  With an oblique projection (B, C), the two objects cease to be superimposed and easily become recognizable when the angulation of the X-ray machine is known.  The buccal object (the one closest to the radiographic source) is displaced in the same direction as the X-rays www.indiandentalacademy.com
  27. 27. Central (x-ray) beam passing directly through a root containing two canals will superimpose the canals on the film. When the cone is shifted to the mesial or distal aspect, the lingual object will move in the same direction as the cone; the buccal object will move in the opposite direction (SLOB rule) www.indiandentalacademy.com
  28. 28. buccal root during endodontic treatment of a first upper premolar with two roots With the standard projection, the roots appear superimposed. Angling the X-ray machine in a mesiodistal direction, the buccal root appears close to the second premolar, while the palatal root appears close to the canine. www.indiandentalacademy.com
  29. 29.  If this technique is standardized so that the upper premolars are always radiographed at a slight mesiodistal angle, the buccal roots will always appear to be distal, while the palatal roots will be mesial.  Obviously, if the angle of the X-ray beam was reversed in a distomesial direction, the buccal root would appear close to the canine in the radiograph, while the palatal would appear close to the second premolar. www.indiandentalacademy.com
  30. 30.  DIGITAL RADIOGRAPHY  A digital radiograph consists of a number of pixels(picture elements) and each pixel is the smallest picture element of the image.  DIRECT DIGITAL IMAGING -a digital sensor is used. CCD CMOS STORAGE PSP  INDIRECT DIGITAL IMAGING -imaging plates of various sizes are used in place of x ray film. INPUT IMAGE PROCESSING www.indiandentalacademy.com OUTPUT
  31. 31. www.indiandentalacademy.com
  32. 32.  Indirect system  Uses film like photo phosphor plates that are activated using X-rays, then scanned in special devices that read the image from the plate.  These imaging plates which replace conventional screen film system are a polyester base sprayed and coated with a crystalline halide composed of Europium activated Barium fluorhalide compounds. (BaF Br : Eu2+). www.indiandentalacademy.com
  33. 33.  Principle:  When X-ray beams are irradiated onto Imaging Plate (IP), the X-ray energy is temporarily stored within the crystals.  Next, a He-Ne laser beam is irradiated onto IP, and the X-ray energy stored in the crystals is emitted as fluoroscent blue light.   Fluoroscent optic signals converted to time serial electric signals. A very small amount of stored X-ray energy remains in IP even after the latent image has been converted to light.  This residual energy can easily be eliminated by exposing IP to sunlight. Consequently IP can be used repeatedly. www.indiandentalacademy.com
  34. 34.  Merits:  No chemicals are required for processing.  No film and chemical waste disposal problem.  One of the main advantages is their similarity to film. They are thin or often thinner than film plates.  Elimination of problems that can be caused through processing faults. • Images can be stored together with patient records thus moving the practice towards a truly paperless environment. • The plates are more flexible and thinner than direct type sensors. www.indiandentalacademy.com
  35. 35.  Ease of positioning the plates as compared to wired sensors used in direct systems which are difficult to position especially when assessing posterior teeth.  Unlike direct sensors, plates are relatively inexpensive, which is wise since they typically must be replaced after 500-700 uses.  Demerits:  The plates get easily scratched and while they theoretically can last through 500 uses, damage normally requires their replacement frequently.  Phosphor plates have less resolution in line pairs / mm than sensors. www.indiandentalacademy.com
  36. 36.  Also because of the steps needed to obtain an image, the time needed to take phosphor plate image is very close to the time needed for film.  Examples :- GENDEX DENOPTIX and SOREDEX DIGORA. Direct digital sensor systems  Direct systems use a wire based sensor that contains a computer chip inside a protective casing, the sensor being further connected to the computer. www.indiandentalacademy.com
  37. 37.  Principle:  The computer chip which is a Charged Couple Device (CCD) captures light information that is emitted by a phosphor plate in the sensor, when it is hit by X-rays.  The information is then directly transmitted into the computer, digitized, then displayed as an X-ray image on the computer.  - Examples of leading manufacturers of direct systems are Schick CDR, Trex. Trophy RVG, New Image Ni-Dx, Siemens. Sirona Sidexis, Dexis Digital X-ray Cygnus Ray 2 Sens-A-Ray www.indiandentalacademy.com
  38. 38. Advantages of digital radiography over conventional radiography :  Working time from image exposure to image display is reduced .  Chemical processing is avoided, so there are fewer hazards to the environment and no image errors because of processing.  Exposure to radiation is reduced . Greater dynamic range is available compared with film; overexposure and underexposure are less apt to occur, contrast and density can be enhanced, size can be changed, and colors added.  Cephalometric measurements and analyses can be more easily performed with the aid of task dependent software.  Storage and communication are electronic, so copies of an image can be sent to others without losing the original. www.indiandentalacademy.com
  39. 39. Radiovisiography  Introduced by Moyer et al in 1989.  Radio part- sensor – Exchangeable scintillation screen, A fiber optic, miniature CCD device.  Visio part- stores & converts point by point into one of 256 discrete gray scales.  Graphy part www.indiandentalacademy.com
  40. 40. Digital Radiograph (RVG) sensor head object x-ray source scintillator CCD fibre optic layer transmitter converter amplifier www.indiandentalacademy.com PC quantizer amplifier receiver
  41. 41. Radiovisiography  RVG comprises of four basic components:  An X-ray set with electronic time; an intra-oral sensor; a display processing unit (DPU); and a printer.  Features of RVG:  1) Image Enhancement A) A smoothing (low-pass) filter eliminates ‘noise/scatter’ that may be present within the image;  B) Edge enhancement (high-pass filter) enhances the ‘edges’ between adjacent regions of different grey-level values, but increases the electronic noise level (this feature can be further improved by use of the next method of enhancement) www.indiandentalacademy.com
  42. 42.  C) Edge detection (Laplacian)- enhances the edges within image but eliminates detail from the rest of the time.  2) Radiation dose - The specific radiation dose required is dependent on the area of the mouth to be irradiated, for example the dose required is greater in the maxillary molar region than the lower incisor region.  3) Resolution - The introduction of the ZHR function increased the resolution to 11 line pairs/ mm in this mode. This measurement has been confirmed by Benz and Mouyen. The authors found a resolution of 7 line pairs/ mm in standard mode. www.indiandentalacademy.com
  43. 43.  4) Collimation - Incorporating rectangular collimation to the RVG sensor would therefore permit a further decrease in radiation dose. Merits:  The image processing time is very short being about 5 seconds.  Sensors can be easily moved from operatory to operatory, allowing the operators to work with a minimum number of sensors and within a computer network environment.  The problems that can be caused through processing faults are eliminated.  It gives opportunity to enhance the images for more precise viewing. www.indiandentalacademy.com
  44. 44.  Demerits:  They are thicker than films and have cables running off the sensors which some patients don’t tolerate well.  The high cost of sensor is another drawback.  There is greater difficulty in placing the sensor with a small percentage of patients due to its rigidity. www.indiandentalacademy.com
  45. 45. DIRECT DIGITAL SENSORS    CHARGE-COUPLED DEVICE (CCD) COMPLEMENTARY METAL OXIDE SEMICONDUCTOR ACTIVE PIXEL SENSOR (CMOS-APS). Photo stimulable phosphor plates (PSP) CHARGE-COUPLED DEVICE (CCD)  The CCD is a solid-state detector composed of an array of X-ray or light sensitive pixels on a pure silicon chip.  A pixel or picture element consists of a small electron well into which the Xray or light energy is deposited upon exposure.  The individual CCD pixel size is approximately 40µ with the latest versions in the 20µ range. The rows of pixels are arranged in a matrix of 512 x 512 pixels. www.indiandentalacademy.com
  46. 46.  There are two types of digital sensor array designs: AREA AND LINEAR.  Area arrays are used for intra oral radiography,  Linear arrays are used in extraoral imaging.  Area arrays are available in sizes comparable to size 0, size 1, and size 2 film, but the sensors are rigid and area for image acquisition. www.indiandentalacademy.com
  47. 47. X-RAY IMAGING WITH CCD SCINTILLATOR - converts x-radiation to photons (light) FIBRE OPTIC LAYER - conducts photons to CCD - stops x-radiation CCD - converts photons to electrons (charge) ELECTRONIC CIRCUIT - amplifies the signal - converts the analog signal to digital www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. Xeroradiography.  Records images without film.  Consists of image receptor plates –selenium particles.  Latent image is converted to a positive image –process called development in processor unit.  Advantages :  Reduced radiation dose.  Image can be produced in 20 seconds.  Edge enhancement effect .  Ability to have both positive and negative prints. www.indiandentalacademy.com
  50. 50.  Improves visualization of files and canals.  Two times more sensitive than conventional D-speed films.  Disadvantages:  Exposure time varies according to the thickness of plate. www.indiandentalacademy.com
  51. 51. DIGITAL SUBSTRACTION RADIOGRAPHY.  This is a technique by which stuctured noise is reduced in order to increase the detectability of changes in the radiographic pattern.  The structured noises are the images which are not of diagnostic value and which interfere in routine interpretation of radiographs,i,e, required areas are enlarged against a background.-  “Image-enhancement method”-area under focus displayed against a neutral background www.indiandentalacademy.com
  52. 52.  Standard radiographs-are produced with identical exposure geometry.  Reference/baseline image.  Follow up image-for comparison.  The difference between original and subsequent images shows up as dark/bright areas.    Bright area-when the change represents-gain Dark area-when the change represents-loss. The strength of digital substraction radiograph is that it cancels out the complex anatomical background against which this change occurs. www.indiandentalacademy.com
  53. 53. Comparing baseline to follow up images made at 3,6,12 months following endodontic therapy, Column 3 indicates substracted of follow up images from baseline radiographprogressive remineralisation of distal root of first molar is seen www.indiandentalacademy.com
  54. 54.  Applications  Useful in detecting progess of remineralisation and demineralisation pattern of dentinal caries, diagnosis of incipient caries.  Assess success of root canal treatment detecting periapical lesions.  90% accurate in detecting as little as 5%mineral loss as compared to conventional radiograph(30-60%loss) www.indiandentalacademy.com
  55. 55. Computed tomography  Computed tomography (CT) has evolved into an indispensable imaging method in clinical routine.  It was the first method to non-invasively acquire images inside the human body that were not biased by superposition of distinct anatomical structures.  CT yields images of much higher contrast compared with conventional radiography.  During the1970s, this was an enormous step toward the advance of diagnostic possibilities in medicine. www.indiandentalacademy.com
  56. 56.  PRINCIPLE OF COMPUTED TOMOGRAPHY  In conventional CT, the X-ray tube and detector rotate around the patient with the table stationary.  The X-ray beam is attenuated by absorption and scatter as it passes through the patient with the detector measuring transmission  Multiple measurements are taken from different directions as the tube and detector rotate.  A computer reconstructs the image for this single “slice.” The patient and table are then moved to the next slice position and the next image is obtained. www.indiandentalacademy.com
  57. 57. COMPUTED TOMOGRAPHY Parts of the Equipment; 1. Scanner ( movable x ray table + gantry) 2. Computer system 3. A display console www.indiandentalacademy.com
  58. 58. Fig. 4: Schematic illustration showing the continuous relationship for different projection angles and related apertures existing between transmission radiography at one extreme and conventional computed tomography at the other. www.indiandentalacademy.com
  59. 59. RADIATION DOSAGE FOR CT Radiation dosage 1.536 rad for a single section 1.8432 rad for multiple sections Estimated dose to the centre of the condyle with CT is 180mR www.indiandentalacademy.com
  60. 60. ADVANTAGES  Eliminates the super-imposition of images of structures outside the area of interest.  Because of the inherent high-contrast resolution of CT differences between tissues that differ in physical density by less than 1% can be distinguished.  Very small amounts and differences in X-ray absorption can be detected. This in turn enables:  Detailed imaging of intracranial lesions  Imaging of hard and soft tissues www.indiandentalacademy.com
  61. 61.  Excellent differentiation between different types of tissues both normal and diseased  Images can be manipulated.  Axial tomographic sections are obtainable  Reconstructed images can be obtained from information obtained in the axial plane.  Images can be enhanced by the use of IV contrast media (so altering the patient) providing additional information www.indiandentalacademy.com
  62. 62. DISADVANTAGES  Need for contrast media for enhanced soft tissue contrast.  Tissue non-specificity i.e. it does have ability to highlight any particular organ/ tissue.  Cost concerns . www.indiandentalacademy.com
  63. 63.  The equipment is very expensive.  Very thin contiguous or overlapping slices may result in a generally high dose investigation.  Metallic objects, such as fillings may produce marked streak or star artefacts across the CT image.  Inherent risks associated with IV contrast agents . www.indiandentalacademy.com
  64. 64.   IMAGE RECONSTRUCTION In CT a cross- sectional layer of the body is divided in to many tiny blocks.  Each block is assigned a number proportional to the degree the block attenuated the x-ray beam.  The individual blocks are called “Voxels and Pixels”.  A voxel is a volume element and the pixel is a picture element.  Their composition & thickness along with the quality of the beam determines the attenuation coefficient . www.indiandentalacademy.com
  65. 65. www.indiandentalacademy.com
  66. 66. Cone-Beam computed tomography  CBCT is an x-ray imaging approach that provides high resolution 3-dimensional images of the jaws and teeth.  Provide valuable information not contained in conventional 2 dimensional films.  CBCT shoots out a cone-shaped x-ray beam and captures a large volume of area requiring minimal amounts of generated x-rays.  Within 10 seconds, the machine rotates 360º around the head and captures 288 static images. www.indiandentalacademy.com
  67. 67. www.indiandentalacademy.com
  68. 68.  Advantages:  Precise identification and detection of periapical lesions.  Detection of mandibular canal.  Complete 3-d reconstruction and display from any angle.  Patient radiation dose 5 times lower than normal ct..  Accurate 3d imaging,excellent resolution.  Inherent quickness in volumetric data acqusition and potential for low cost compared to ct  It requires only a single scan to capture the entire object ,with reduced exposure time. www.indiandentalacademy.com
  69. 69.  Micro – CT  Recently, micro-CTs, which essentially comprise a miniaturized design of the cone beam CTs -typically used for non destructive three-dimensional microscopy have become commercially available.  The X-rayed measuring field usually as small as 2 cM3 in volume. www.indiandentalacademy.com
  70. 70.   Micro-CT desk device of Sky-Scan Inc. at the Institute of Medical Engineering. The object to be examined is placed on a rotating specimen holder inside the measurement chamber. The measurement field is about 2cm3 volume. www.indiandentalacademy.com
  71. 71. TUNED APERTURE COMPUTED TOMOGRAPHY (TACT)  Improve accuracy in caries diagnosis because of its 3-D or pseudo 3-D capabilities.  Principle of TACT:  TACT slices can be produced from an arbitrary number of X-ray projections, each exposed from a different angle.  Using the TACT algorithm, it is possible to use one X-ray source and move it through several points in space or use several fixed sources to collect multiple X-ray projections which in turn can be processed to produce TACT slices . www.indiandentalacademy.com
  72. 72. Fig. 5: Arbitrary example of generalized TACT projection geometry applied to a simple cylindrical object. www.indiandentalacademy.com
  73. 73.  TACT useful in  Detection of caries and recurrent caries ,  Periodontal bone loss,  Periapical lesion localization,  Tmj bone change. www.indiandentalacademy.com
  74. 74. Magnetic Resonance Imaging Principles: Magnetism is a dynamic invisible phenomenon consisting of discrete fields of forces. Magnetic fields are caused by moving electrical charges or rotating electric charges. Images generated from protons of the hydrogen nuclei. Essentially imaging of the water in the tissue. www.indiandentalacademy.com
  75. 75.  The technique is based on the presence of specific magnetic Magnetic Resonance Imaging properties found within atomic nuclei containing protons and neutrons,  Inherent property of rotating about their axis  Causes a small magnetic field to be generated around the electrically charged nuclei.  When dipoles exposed within a strong electric field  Orientation in response to the field  Depending on density and spatial relation  Signal interpreted and image produced www.indiandentalacademy.com
  76. 76. Equipment; 1. The Gantry ;houses the patient. Patient is surrounded by magnetic coils 2. Operating console ; where the operator controls the computer and scanning procedure 3. Computer room network. www.indiandentalacademy.com
  77. 77.  When images are displayed; intense signals show as white and weak ones as Black and Intermediate as shades of gray.  Cortical bone and teeth with low presence of hydrogen are poorly imaged and appear black. www.indiandentalacademy.com
  78. 78. Advantages of MRI • It offers the best resolution of tissues of low inherent contrast. • No ionizing radiation is involved with MRI • Direct multiplanar image is possible without reorienting the patient. Disadvantages:   Long imaging time. Potential hazard imposed by the presence of ferromagnetic metals in the vicinity of the imaging magnet. www.indiandentalacademy.com
  79. 79.  Complications;  Magnetic forces and radio waves - not know to produce any biological side effects in man. Non invasive technique and can be used in most patients.   Contraindications;  Patients with cardiac pacemakers. Patients with cerebral metallic aneurysm clips. Slight movement of the clip could produce bleeding Stainless steel and other metals produce artifacts ; obliterate image details of the facial area.*   www.indiandentalacademy.com
  80. 80.           Indications Assessing diseases of the TMJ Cleft lip and palate Tonsillitis and adenoiditis Cysts and infections Tumors Short comings; Inability to identify ligament tears or perforations Dynamics of tissue joint not possible Cannot be used in patients suffering from claustrophobia. www.indiandentalacademy.com
  81. 81. d) Ultra sound scanning.  Ultra high frequency sound waves are used.  The reflected sound waves are processed to electrical signal that is amplified, processed and ultimately displayed on a monitor.  Technique currently in use permit echoes to be processed at a sufficient rate to allow for the perception of motion it is known as Real-time imaging.  US waves are generated by a quartz or synthetic ceramic crystal when it is exposed to an alternating current of 3-10 Mhz. as a result of the piezoelectric effect, the crystal distributes US waves oscillating at the same frequency www.indiandentalacademy.com
  82. 82.  US image produced - automatic movement of the crystal over the tissue of interest.  As each movement gives one image of this tissue (depending on its plane) and there is a frequency of 30-50 images per s, they appear in a screen as moving images.  Useful adjunct to conventional radiography in the management of extensive periapical lesions, as it provides specific information on the size of the lesion www.indiandentalacademy.com
  83. 83. CONCLUSION  New approaches to radiography have been and are being developed.  These are unique; some will improve existing techniques in addition to decreasing the radiation dose to patients.  This new technology includes digital radiography, digital subtraction radiology, and tomography. www.indiandentalacademy.com
  84. 84. References • • • • • • • Dental radiography :principles and techniques by Laura jansen ,Haring.4th edition Textbook of Endodontics by ingle,6th edition Principles and practice of endodontics by walton. 4th edition Radiographic manifestations of periapical inflammatory lesions How new radiological techniques may improve endodontic diagnosis and treatment planning.(endodontic topics 2004) Textbook of Endodontics by Arnaldo Catelucci. Oral radiology :white and pharaoh 6th edition Google n internet sources www.indiandentalacademy.com
  85. 85. Thank you! www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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