2. Principles Of Radiation Protection:
• The imaging procedure should be judged to do more
good (e.g. diagnostic efficacy of the images) than harm
(e.g. detriment associated with radiation induced cancer
or tissue effects) to the individual patient.
• Therefore, all examinations using ionizing radiation
should be performed only when necessary to answer a
medical question, treat a disease, or guide procedure.
• The clinical indication and patient medical history
should be carefully considered before referring a patient
for any X-ray examination.
3. Principles Of Radiation Protection:
• X-ray examinations should use techniques that are
adjusted to administer the lowest radiation dose that
yields an image quality adequate for diagnosis or
intervention (i.e. radiation doses should be "As Low as
Reasonably Achievable“ (ALARA)).
• The technique factors used should be chosen based on
the clinical indication, patient size, and anatomical
area scanned and the equipment should be properly
maintained and tested.
4. Benefits Of X-ray Examinations
1. Non invasively and painlessly help to diagnose the
disease and monitor therapy.
2. Support medical and surgical treatment planning.
3. Guide medical personnel as they insert catheters, stents,
or other devices inside the body, treat tumors, or
remove blood clots or other blockages.
5. Risks Of X-ray Examinations
1. A small increase in the possibility that a person
exposed to X-rays will develop cancer in later life.
2. Tissue effects such as cataracts, skin reddening,
and hair loss, which occur at relatively high levels
of radiation exposure and are rare for many types
of imaging exams.
3. Possible reactions associated with an intravenously
injected contrast agent (dye), that is sometimes
used to improve visualization.
6. Radiology And Children
• Children have an increased
radio sensitivity to ionizing
radiation (on average 2 - 3
times), which creates high
risk, both somatic and
genetic effects of radiation;
• Physical and physiological
differences between adults
and children, including the
closeness of the bodies, as
well as irregular dynamics
of their development, lead
to higher levels of radiation
to children than adults.
7. Methods Of Limiting And Reducing Radiation
Exposure In Children
!!!!! Exclude unnecessary studies or those studies which is
of no need... !!!!!
Not subject to preventive
radiological studies in
children up to 14 years of
age and pregnant women.
Women of child-bearing age should
be questioned about possibility of
pregnancy before abdominal X-ray
8. The risk of developing cancer from medical imaging
radiation exposure is generally very small, and it
1. Radiation dose - The lifetime risk of cancer increases the larger
the dose and the more X-ray exams a patient undergoes.
2. Patient’s age - The lifetime risk of cancer is larger for a patient
who receives X-rays at a younger age than for one who
receives them at an older age (hormonal status and
3. Patient’s sex - Women are at a somewhat higher lifetime risk
than men for developing radiation-associated cancer after
receiving the same exposures at the same ages.
4. Body region - Some organs are more radiosensitive than
Wilhelm Conrad Roentgen - Father of Radiology
Nov 8, 1895 – Discovered unknown radiations with
photographic effect which he named ‘axa rays’
He got the Nobel prize in 1901.
X-rays represent a form of ionizing electromagnetic radiation. They
are produced by an x-ray tube, using a high voltage to accelerate
the electrons produced by its cathode. The produced electrons
interact with the anode, thus producing x-rays. The x-rays
produced include Bremsstrahlung.
An x-ray generator gives power to the x-ray tube. It contains high voltage transformers,
filament transformers and rectifier circuits.
The cathode is the negative terminal of an x-ray tube. It is a tungsten filament and when
current flows through it, the filament is heated and emits its surface electrons by a process
called thermionic emission (TIE).
Kilo voltage :
High voltage, in the kilovolt range (1000 volts), is applied between the cathode and anode.
This causes electrons to move towards the positive terminal (anode) of the tube at a velocity
of half the speed of light (c).
The positive terminal of the tube. Made of a tungsten disc in ordinary diagnostic x-ray tubes.
X-ray Tube :
also called Roentgen tube, that produces X rays by accelerating electrons to a high velocity
with a high-voltage field and causing them to collide with a target, the anode plate.
12. What are x-rays?
X-rays are a type of ionizing
radiation called electromagnetic
X-ray imaging creates pictures of
inside of our body. The images
show the parts of our body in
different shades of black and white.
The most familiar use of x-rays is
checking for fracture, but x-rays are
also used in other ways.
14. In digital radiography the
radiography equipment looks
like a box-like apparatus
containing the recording
material- such as a digital
recording plate against which
the individual places his/her
The apparatus containing the
x-ray tube, usually positioned
about six feet (72 inches) away.
15. Radiography involves exposing a part of
the body to a small dose of radiation to
produce an image of the internal organs.
When x-rays penetrate the body, they
are absorbed in different amounts by
different parts of the organ.
For example: The ribs and spine absorb
much of the radiation and appear white
or light gray on the image.
Lung tissue absorbs little radiation and
appears dark on the image.
How Does The Procedure Work?
16. X-ray Production:
X-rays are produced due to sudden deceleration of fast-
moving electrons when they collide and interact with the
target anode. In this process of deceleration, more than 99%
of the electron energy is converted into heat and less than
1% of energy is converted into x-rays.
17. Image Formation
A radiographic image is created by passing an x-ray beam
through the patient and interacting with an image receptor (a
device that receives the radiation leaving the patient) such as a
film-screen or digital system.
Both the quantity and quality of the primary x-ray beam
affect its interaction within the various tissues that make up
the anatomic part.
18. The absorption characteristics of the anatomic part are
determined by its composition, such as thickness, atomic number,
and tissue density or compactness of the cellular structures.
Finally, the radiation that exits the patient is composed of
varying energies and interacts with the image receptor to
form the latent or invisible image.
The process of image formation is a result of differential
absorption of the x-ray beam as it interacts with the anatomic
The term differential is used because varying anatomic parts
do not absorb the primary beam to the same degree.
Anatomic parts composed of bone absorb more x-ray photons
than parts filled with air.
19. FIGURE : As the primary x-ray beam interacts with the anatomic part,
photons are absorbed, scattered, and transmitted. The differences in the
absorption characteristics of the anatomic part create an image that
structurally represents the anatomic part.
20. Creating A Radiographic Image By Differential
Absorption, These Several Processes Occur:
i. Beam attenuation
ii. Absorption &
i. Beam attenuation: As the primary x-ray beam passes
through anatomic tissue, it loses some of its energy. Fewer x-
ray photons remain in the beam after it interacts with
anatomic tissue. This reduction in the energy or number of
photons in the primary x-ray beam is known as attenuation.
Two distinct processes occur during beam attenuation:
Absorption and Scattering.
21. ii. Absorption: As the energy of the primary x-ray beam is
deposited within the atoms comprising the tissue, some x-ray
photons are completely absorbed. Complete absorption of the
incoming x-ray photon occurs when it has enough energy to
remove (eject) an inner-shell electron.
Scattering: Some incoming photons are not absorbed but
instead lose energy during interactions with the atoms
comprising the tissue. This process is called scattering.
iii. Transmission: If the incoming x-ray photon passes
through the anatomic part without any interaction with the
atomic structures, it is called transmission
24. Properties of X-rays:
i. They have short wavelength of EMS and high frequency.
ii. Requires high voltage to produce x-rays.
iii. Highly penetrating and invisible to eyes.
iv. Liberates small amount of heat when passing through
v. They travel in a straight line with the velocity of light and do
not carry an electric charge with them.
vi. They are capable of travelling in a vacuum.
vii. They are used to capture the human skeleton defects.
viii. Produce chemical and biological changes.
ix. Produce scatter and secondary radiation.
25. Characteristic of X-Ray
i. Moving in a straight line.
ii. Has the power to penetrate an increasingly stronger in
voltage used the higher.
iii. Can penetrate certain objects, such as wood up to several cm.
iv. Not deflected by a magnetic field and electric field.
v. Can detach electrons from the metal are pounded (grind).
26. X-ray Modalities
General Methods Complementary Methods Contrast Media
Radiography Convential linear tomography Barium meal
Fluoroscopy Decubitus Barium enema
27. All X-ray Modalities Work On The Same
An X-ray beam is passed through the body where a
portion of the X-rays are either absorbed or scattered by
the internal structures, and the remaining X-ray pattern is
transmitted to a detector (e.g. film or a computer screen)
for recording or further processing by a computer.
29. Principles Of Radiography
i. Radiation is transmitted to varying degrees depending
upon the density of the material through which it is
ii. Thinner areas and materials of a less density show as
darker areas on the radiograph.
iii. Thicker areas and materials of a greater density show
as lighter areas on a radiograph.
iv. Applicable to metals, non-metals and composites.
Conventional x-ray image are produced using a silver
based photographic emulsion.
Now a days digital recording is being used.
Digital radiography is made by differential absorption
of x-ray beam measured by special phosphor screen
and read by laser.
This can either write the image into film or display on
4 basic densities:
Gas, Fat, Soft tissue and Calcified structures
Gas absorbs less x-ray and appear black.
Calcium absorbs the most and appear white.
Solid soft tissue (except fat), e.g. solid viscera, muscle,
blood, variety of fluids, bowel wall, etc. have similar
absorptive capacity and appear grey.
Fat absorbs fewer x-ray so appears blacker than other
33. Disadvantages of Radiography:
1. Health hazard
2. Sensitive to defect orientation
3. Access to both sides required
4. Limited by material thickness
5. Skilled interpretation required
6. Relatively slow
7. High capital outlay and running costs
34. Basic Concepts!!!
1. One view is no view – use it all!
2. Patterns are your clue
3. Be sure you are looking
4. Know what you’re looking for
5. Know the limits of your test
35. One View Is No View
Posterior sulcus nodule = Cancer (Mass)
41. Review: What Are The 5 Basic Radiographic
Densities From Black To Bright White?
3. Soft tissue/fluid
4. Bone / Mineral
42. X-ray Film
Displays the radiographic image and consists of Emulsion
(single or double) of Silver halide crystals (95 % silver bromide
and 5% silver iodide) and Gelatin.
Which when exposed to light, produces a silver ion (Ag+) and
The electrons get attached to the sensitivity specks and attract
the silver ion.
Subsequently, the silver ions attach and clumps of metallic
silver (black) are formed.
i. Base: Supports the fragile photographic emulsion.
ii. Substratum: an adhesive layer containing gelatin and
solvents that bind emulsion and base.
iii. Emulsion: Photosensitive Layer of the film, silver halide and
gelatin are key ingredients.
iv. Protective layer: gelatin super-coat
The total thickness of the film is about 0.25 mm.
44. Super Coating
• Thin layer of Gelatin.
• Protects the emulsion from mechanical damage.
• Prevents scratches and pressure marks.
• Makes the film smooth and slick.
45. X-ray Film
• Produced from the cattle bones.
– Keeps “Silver Halide Grains”
• Well dispersed
• Prevent clumping of grains
– Developing solutions can
penetrate Gelatin rapidly
without damaging the
structure and strength.
– Easily available in large and
• Light sensitive material in emulsion.
– 90-99% Silver Bromide
– 1-10% Silver Iodide – It increases
• Silver Iodo-Bromide crystals are
precipitated and emulsified in
• Precipitation reaction involves
addition of Silver Nitrate to soluble
Halide to form soluble Silver Halide
AgNO3 + KBr AgBr + KnO3
46. Types of x-ray film:
1. Screen type films: faster when used with intensifying
– Orthochromatic (green sensitive)
2. Direct exposure type: used for dental exposures.
47. The Latent Image
Remnant radiation interacts with the silver halide crystals.
Mainly by the photoelectric interaction.
The energy deposited into the film is in the same pattern as
the subject that was exposed to radiation.
This invisible image is known as the Latent Image.
A latent image on photographic (radiographic) film is an
invisible image produced by the exposure of the film to light
48. Formation of latent image:
Metallic silver is black, so it is this metallic silver that
produces black areas on a developed films.
Exposure of silver-iodo-bromide grains to light photons
emitted by screen / direct x-ray exposure initiates the
formation of atomic silver to form a visible pattern.
The Manifest Image:
By chemically processing the latent image it is made visible.
Certain chemicals permanently fixate the image onto the film.
49. Manual film Processing
1. Developing – formation of the
2. Fixing – stopping of
fixing of image on film
3. Washing – removal of residual
4. Drying – warm air blowing
50. Automatic x-ray film processing system
Systems of the Automatic Processor:
1. The Film Feed Section
2. Transport System
3. Temperature Control System
4. Recirculation System
5. Replenishment System
6. Dryer System
7. Electrical System
Different views of the chest can be obtained by changing the relative
orientation of the body and the direction of the x -ray beams:
Described by the path of x-ray beam
i. PA (postero-anterior) view means beam pass from back to
ii. AP (antero-posterior) view means beam pass from front
to the back.
iii. Lateral: right lateral, left lateral.
iv. Oblique: right oblique, left oblique, etc.
Used to take radiographs in bed or operation theatre.
The exposure is long and quality is compromised.
Is a type of medical imaging that shows a real time x-ray image on a
monitor, much like an x-ray movie.
During a fluoroscopy procedure, an x-ray beam is passed through
Fluoroscopic apparatus uses low current (0.5-5 mA) for continuous
In recent years flat panel detectors (which are similar to the digital
radiography used in projection radiography) have been replacing
the image intensifiers.
Resultant images have relatively low signal to noise ratio (SNR) but
are of sufficient quality for patient positioning and certain
59. Image Intensifiers
The image intensifier tube is a complex electronic device
that receives the image forming x-ray beam and converts
it into a visible light image of high intensity.
Within an image intensifier, the input phosphor converts
the x-ray photons to light photons. Which are than
converted to photoelectrons within the photocathode.
60. Image Intensifiers
Through this process, several thousand light photons are
produced for each x-ray photon reaching the input phosphor.
Most modern image intensifiers use cesium iodide for the
input phosphor because it has a high absorption efficiency
and thus decreases patient dose.
IMAGE INTENSIFICATION = photons are amplified + multiplied
61. Applications of Fluoroscopy:
Fluoroscopy is used in many types of examinations
and procedures such as:-
1. Cardiac catheterization.
2. Arthrography (visualization of joint or joints).
3. Lumbar puncture.
4. Placement of intravenous (IV) catheters (hallow tubes
inserted into veins or arteries).
5. GIT investigations.
62. 3. Fluorography
Is photography of X-ray images from a fluorescent screen. It
is commonly used in some countries for chest X-ray
screening, e.g. to diagnose tuberculosis or lung cancer.
The photographic recording of fluoroscopic images on small
film using a fast lens; used in mass radiography of the chest.
Fluorography machines are compact and can be mounted in
a car, this makes it possible to carry out mass research in
those areas where there is no X-ray equipment.