Types of X-ray machines

1. X-RAY MACHINES -
CONVENTIONAL AND DIGITAL
Dr. Urfeya Mirza
Deptt. of Vety. Surgery
and Radiology

2. INTRODUCTION
• X rays are the ionizing electromagnetic radiation emitted
from a highly evacuated high-voltage tube. Inner orbital
electrons in the target anode are stimulated to emit x-
radiation via bombardment by a stream of electrons from a
heated cathode
• X-rays, like gamma rays, are penetrating and carry
enough energy to ionize atoms in their path. Nearly
identical to gamma rays, x-rays require shielding to reduce
their intensity and minimize the danger of tissue damage to
personnel. Mishaps with x-rays can cause severe
radiation burns and deep tissue damage and can lead to
various cancers

3. X-rays were discovered in 1895 when Wilhelm Conrad
Roentgen observed that a screen coated with a barium salt
fluoresced when placed near a cathode ray tube. Roentgen
concluded that a form of penetrating radiation was being
emitted by the cathode ray tube and called the unknown
rays, X-rays .
First X-ray Image

4. X-RAY MACHINE
An x ray machine is a complex device used in
variety of applications around the world. With the
ability to penetrate hard objects, they are used for
purposes such as to look for broken bones or
problems within the body in the medical
community, air port security check points, in the
industrial QC applications and for research
purposes.

5. PRINCIPLES OF OPERATION
 An x-ray machine is essentially a camera. Instead of
visible light, however, it uses X-rays to expose the film. X-
rays are like light in that they are electromagnetic waves,
but they are more energetic so they can penetrate many
materials to varying degrees. When the X-rays hit the film,
they expose it just as light would
 Since bone, fat, muscle, tumors and other masses all
absorb X-rays at different levels, the image on the film lets
you see different (distinct) structures inside the body
because of the different levels of exposure on the film

6. PRODUCTION OF X-RAY
An x-ray tube requires a source of electrons, a means to accelerate
the electrons, and a target to stop the high-speed electrons.

7.  The filament is heated to boil off electrons which are then accelerated
to the anode
 The filament is contained within the cathode which is cup shaped to
focus the electrons onto the focus spot on the anode
 Tube currents of 50-800 milliamperes are used whereas filament
currents are in the range of 2-5 amperes
 The anode is bevelled at an angle of 12 to 17 degrees in order to
maximise the contact area while focussing the resultant beam
 The anode is usually composed of tungsten or molybdenum as it must
withstand very high temperatures (>3000 degrees C)
 Correct warm up and stand by procedures are essential to maximise
tube and filament life

8.  When the electrons from the cathode are accelerated at
high voltage to the anode:
 99% of the energy is dissipated as heat
(anode materials are selected to withstand the high temperatures they are able
to withstand)
 1% is given off as x-rays.
 The energy of the x-rays (keV) is determined by the
voltage applied (kVp) while,
 The amount of x-rays is determined by the current (mA).

9. Block Diagram of the X-ray
Machine

10. PARTS OF X-RAY MACHINE
X-ray has three main components:
 Operating Console
 High Frequency Generator
 X-ray Tube
Internal
External
Other Parts include:
 Collimator and
 Grid Bucky
 X-ray Film

11.  X-Ray Generator: High voltage generator:
modifies incoming voltage and current to
provide an x-ray tube with the power needed
to produce an x-ray beam of the desired
peak-kilo-voltage (k V p) and current (mA)
and duration (Time).
 Control panel: Permits the selection of
technique factors and initiation of
radiographic exposures mA, kV, Time
 Transformer: Transformers modify the
voltage of incoming alternating-current
(AC) electrical signals to increase or
decrease the voltage in a circuit.

12. …CONT
 Step-up transformer: Supplies the high
voltage to the x-ray tube (voltage increases and
current decreases)
 Step-down transformer: Supplies power to
heat the filament of the x-ray tube (voltage
decreases and current increases)
 Autotransformer: Supplies the voltage for the
two circuits and provide a location for the K v
p meter (indicates the voltage applied across
the x-ray tube)
 Rectifiers: Convert AC into the direct current
(DC) required by the x-ray tube. A rectifier
restricts current flow in an x-ray tube to one
direction (from cathode to anode), thereby
preventing damage to the x-ray tube filament.
Two types: Half wave and Full wave.

13. …CONT
 X-RAY TUBE: It is an
expensive wearing
element in medical
radiological equipment.
It consists of :
 Anode
 Expansion bellows
(provide space for oil
to expand)
 Cathode (and heating-
coil)
 Tube envelope
(evacuated)
 Tube housing
 Cooling dielectric oil
 Rotor

14. vacuum
Protection
housing
Projectile

15. PROTECTING HOUSING

16. …CONT
 High Tension Cable: Special highly insulated
cables Considered are the cable capacitance (130-
230 pF/m) because it affects the average value of
the voltage and current across the x-ray tube
(increases the power delivered to the tube.
 Collimators and Grids: They are used to increase
the image contrast and to reduce the dose to the
patient by mean limiting the x-ray beam to the area
of interest.
 Collimator: It is placed between the x-ray tube
and the patient and Usually provided with an
optical device, by which the x-ray filed can be
exactly simulated by a light filed.
 Grid: It is inserted between the patient and the
film cassette in order to reduce the loss of contrast
due to scattered radiation.

17. …CONT
 X-ray film: X-ray film is a sensitive material (sheet) for the x-ray. A
film that has been exposed to x-rays shows an image of the x-ray
intensity.

18. SCHEMATIC DIAGRAM (EXTERNAL COMPONENTS)
11. Cassette holder 12. Cable 13. Imaging hand switch 14. Control panel 15. Generator
16. Display screen 17. Stretcher 18. X-ray tube 19. Collimator 20. Cassette 21. Interface
cable 22. trolley 46. Hand grip 66.tube

19. CONVENTIONAL X-RAY MACHINE:
 A conventional system uses an intensifying
screen to create a latent image on x-ray film.
The film is then processed, creating a
manifest image that can be interpreted by a
physician. It is later stored in the file room.

20. LIMITATIONS
Conventional radiography (also known as screen film
radiography SFR) is still used more widely than digital
radiography but this dominance is fast dwindling. The
reasons behind the declining popularity of SFR are —
 Diagnostic image quality is poor
 Fixed non-linear Grey scale response
 Limited potential for reducing dose to the patient
 The images cannot be changed in contrast once they
have been processed
 Film is expensive, uses hazardous materials for
processing
 This method is labour intensive
 Long term storage and retrieval of film is difficult
 SFR is not compatible with the Picture Archiving And
Communication Systems (PACS)

21. DIGITAL RADIOGRAPHY
 X-ray tube is coupled to a
specialized reciever that
changes x-rays into electrical
signals
 Analog image is digitalized &
displayed on integrated
computer screen
 Data is stored in magnetic
optical
discs(MODs),CDs,DVDs
ADVANTAGES :
 No films are required
 No screens are required
 No processing is required
 Brightness & contrast of images

22. Digital systems are traditionally split into two broadly defined
categories:
 Direct radiography(DR)
 Computed radiography (CR)
The detector classification is related with the conversion
process of X-ray energy to electric charge:
 DR technology converts X-rays into electrical charges by
means of a direct readout process using thin-film transistor
(TFT) arrays
 Concerning CR systems they use storage-phosphor image
plates with a separate image readout process, which means
an indirect conversion process

23. DIRECT RADIOGRAPHY
Referred to as “cassette-less” because the detector
is incorporated into the x-ray table or upright wall
unit
 Equipment may be indirect or direct conversion
 Images are ready for viewing within seconds

26. In a system of direct radiography, also called direct capture
radiography, the image receptor is composed of an array of
electronic sensors that respond to the radiation exiting the
patient. These sensors send that information in digital
format to a computer

27. DR / CHARGE COUPLED DEVICE

28. CCD
Lens
Scintillator
X-ray tube
DR / CHARGE COUPLED DEVICE
High Radiation / High Noise Zone
Low Radiation / Low Noise Zone

29. COMPUTED RADIOGRAPHY
 Image obtained using cassettes containing
photostimulable phosphor plates
 CR systems equipment includes reader for image
processing
 Note:
The phosphor plates used in computed radiography
are not as sensitive to light as x-ray, but are
extremely sensitive to scatter radiation.

31. COMPUTED RADIOGRAPHIC MACHINE AT TVCC SKUAST-K

32. X-Ray Digitizer – A scanner used to convert
existing analog images into a DICOM (Digital
Imaging and Communications in Medicine) format.

33. IMAGE MATRIX

34. VIEWING THE IMAGE
 The computer-
processed image can
be viewed on a
computer monitor or
printed on film or
paper
 For an image on a
screen to have the
quality approaching
that of a film image, a
special monitor must
be used with a
resolution of 1024 x
1024 pixels.

35. IMAGE PROCESSING AND POST-PROCESSING
Both allow image manipulation of :
 Density
 Structures demonstrated
 Subtraction permits viewing of bone only or
tissues only
 Contrast enhancement adjusts contrast from very
high to very low

36. Post Processing
Techniques
Subtraction
Contrast
Enhancement
Edge
Enhancement
Black and White
Reversal

37. DIGITAL SUBTRACTION

38. CONTRAST ENHANCEMENT

39. EDGE ENHANCEMENT

40. BLACK AND WHITE REVERSAL

41. DIGITAL IMAGING SYSTEM TECHNICAL
CONSIDERATIONS
 Kilovoltage
May be slightly higher than that used for
conventional radiography
 Centering
Body part of interest must be placed in or near
the center of the detector
 Multiple exposures on one cassette
Although not recommended, if IR is divided for
two separate exposures, the portion not being
exposed must be covered with a lead shield

42. …CONT
 Over- and underexposure
• Degree of image density is not an accurate
indicator of over- or underexposure
• Density may be indicated by a unique number
that correlates to the amount of exposure
 Collimation
• Limit the field of radiation to the anatomy of
interest
• Inadequate collimation can result in
inappropriate contrast

43. …CONT
 Open cassettes
An exposed IR begins to lose the image within
15 seconds of opening the IR
 Grids
• Digital systems are more sensitive to scatter
radiation
• Use grids as appropriate

44. ADVANTAGES OF DIGITAL X-RAY MACHINES:
 The appearance of digital images can be manipulated during and
after processing
 PACS is a network used to manage the images obtained through
DR
 Faster delivery of medical images to the clinicians that evaluate
and report on them. Resulting in faster availability of results
 No lost or misplaced images, which means fewer patients being
postponed or cancelled for consultations or surgery while waiting
for new images
 Flexible viewing with the ability to manipulate images on
screen,which means patients can be diagnosed more effectively
 Instant access to previous images and patient records
 Better collaboration, as PACS can be viewed from multiple
terminals and locations by a range of clinicians, allowing
discussion over diagnoses
 Fewer unnecessary re-investigations, which will in turn reduce the
amount of radiation to which patients are exposed
 No space needed for film storage

45. REFERENCES
 Veterinary radiology by A.P Singh and Jit Singh, 2009
 Selman, J. The Fundamentals of X-Ray and Radium
Physics, 8th Edition, Charles Thomas, 1994
 Internet :
• faculty.mu.edu.sa
• www.pubmed.org
• www.plmer.edu
• www.radiology.org
 Pictures :
 www.hulenhills.com
 www.redwingbooks.com