Orthopantomogram

1. OPG (Orthopantomogram)
Imaging System
MIT -3
Group 3

3. OPG (Orthopantomogram) Imaging System
OPG (Orthopantomogram) is a panoramic dental X-
ray imaging system that provides a single wide view
of:
1. Upper and lower teeth
2. Maxilla and mandible
3. Temporomandibular joints (TMJ)
4. Surrounding jaw structures
It is a 2D imaging technique but covers the entire jaw
in one image.

4. Working Principle of OPG:
 It works on the principle of panoramic
tomography .
 The X-ray tube and image receptor rotate
around the patient’s head.
 A narrow, slit-shaped X-ray beam is
used.
 Only the structures located in the focal
trough (image layer) appear sharp.
 Structures outside this layer appear
blurred.
 Continuous low-dose X-ray exposure is
used during rotation.

5. Components:
1. X rays tube Assembly
2. Collimator
3. Filtration system
4. Rotating arm ( gantry)
5. Image receptor/ detector
6. Patient positioning system
7. Control panel system
8. Computer and image processing
system
9. Display system

6. 1. X-ray Tube Assembly
The X-ray tube is the primary source of X-ray radiation.
Functions
 Produces X-rays by accelerating electrons from
cathode to anode
 Operates at low mA (2–15 mA) and moderate to
high kVp (60–90 kVp)
 Designed for continuous exposure during rotation
Parts
 Cathode: filament and focusing cup (controls
electron flow)
 Anode: tungsten target (produces X-ray photons)
 Tube housing: oil-filled, provides insulation and
heat dissipation

7. 2. Collimator
The collimator is used to shape and limit the X-ray
beam.
Functions
 Converts the X-ray beam into a narrow vertical slit
 Reduces patient radiation dose
 Minimizes scatter radiation
 Improves image contrast and sharpness

8. 3. Filtration System
 Filtration removes low-energy X-ray photons
that do not contribute to image formation.
Types
 Inherent filtration: glass envelope, tube oil,
housing window
 Added filtration: aluminum filters
Functions
 Increases beam quality
 Reduces skin dose
 Produces a more uniform beam

9. 4. Rotating Arm (Gantry)
 The rotating arm supports and moves the tube
and detector.
Functions
 Holds the X-ray tube on one side and the detector
on the opposite side
 Rotates around the patient’s head
 Moves in a pre-programmed curved path
corresponding to the dental arch
 Ensures synchronized movement for panoramic
tomography

10. 5. Image Receptor / Detector
 The image receptor captures transmitted X-rays and
converts them into an image.
Types of Detectors
 Film-based system (older units)
 Digital detectors:
 CCD (Charge Coupled Device)
 CMOS (Complementary Metal Oxide Semiconductor)
 Flat Panel Detectors
Functions
 Converts X-ray photons into electrical signals
 Provides fast image acquisition
 Allows image enhancement and storage

11. 6. Patient Positioning System
 Correct positioning is critical for image accuracy.
Components
 Bite block: stabilizes dental arches
 Chin rest: supports mandible
 Forehead and temple supports: prevent head
movement
 Laser alignment lights:
• Mid-sagittal plane
• Frankfort plane
• Canine line
Functions
 Positions teeth within the focal trough
 Reduces distortion and magnification errors

12. 7. Control Panel
 The control panel allows the operator to
select exposure parameters.
Functions
 Selection of:
 kVp
 mA
 Exposure time
 Program selection (adult, child, TMJ,
panoramic mode)
 Starts and stops exposure

13. 8. Computer and Image Processing Unit
 This unit processes and displays the image.
Functions
 Analog-to-digital conversion (ADC)
 Image reconstruction
 Image enhancement (contrast, brightness, zoom)
 Noise reduction
 Storage and transfer (PACS, DICOM)
9. Display Monitor
 Displays the final panoramic image.
Functions
 High-resolution visualization
 Allows diagnostic interpretation
 Image manipulation by the operator

14. Protective and Safety Components
These ensure patient and operator safety.
Components
 Lead shielding
 Emergency stop switch
 Exposure indicator lights
 Radiation warning labels

15. Clinical Indications of OPG
 Impacted teeth (especially third molars)
 Jaw fractures
 Dental caries (advanced cases)
 TMJ disorders
 Cysts and tumors of the jaw
 Orthodontic treatment planning
 Pre-operative dental assessment

16. Advantages of OPG
 Large field of view
 Entire maxilla and mandible in one image
 Low radiation dose
 Fast image acquisition
 Patient friendly and comfortable
 Useful screening tool
 Detects impacted teeth
 Helps in orthodontic planning
 Digital image storage and processing

17. Disadvantages
 Low image resolution
 Image magnification and distortion
 Positioning errors affect image quality
 No 3D information
 Poor soft tissue visualization
 Not suitable for early caries detection
 Superimposition of structures
 Artifacts from metallic objects

18. Tomography

20. TOMOGRAPHY
Definition
Tomography is an imaging technique used to
obtain cross-sectional (slice) images of the body by
moving the X-ray tube and detector in a
synchronized manner so that structures at a
particular depth are in focus, while structures
above and below that plane are blurred.
👉 The word comes from:
Tomo = slice
Graphy = recording

21. Principle of Tomography
When the X-ray tube and film/detector move in
opposite directions around a pivot point (fulcrum),
Structures lying in the focal plane (layer of
interest) remain sharp,
Structures outside this plane move relative to the
detector and become blurred.
📌 This selective blurring helps visualize a specific
anatomical layer.

22. Basic Components of a Tomographic
System
 X-ray tube
 Patient table
 Film / image receptor / detector
 Fulcrum (pivot point)
 Mechanical linkage for synchronized motion
 Control unit

23. Working of Tomography
 The patient is positioned on the table.
 The level of interest is selected using the fulcrum
height.
During exposure:
 X-ray tube moves in one direction,
 Film/detector moves in the opposite direction.
 Only structures at the selected depth remain
stationary relative to the detector.
 Other structures are blurred due to motion.

24. Advantages of Tomography
✔ Removes superimposition of structures
✔ Better visualization of deep-lying organs
✔ Improves diagnostic accuracy
✔ Useful for complex anatomical regions
Limitations of Tomography
✘ Higher radiation dose than plain radiography
✘ Time-consuming
✘ Motion artifacts possible
✘ Largely replaced by CT in modern practice

25. Thank u 😊