X RAYS

1. X-Ray

2. Objectives:
X-ray tube interactions
Characteristic and
Bremsstrahlung X-rays
X-ray emission spectrum

3. X-ray Imaging System
 PRINCIPAL PARTS
 Operating Console
 High-voltage generator
 X-ray tube
 PRIMARY FUNCTION
 The system is designed to provide a large number of e- at
cathode with high kinetic energy focused to a small target at
anode.

4. How “X-rays” are created
Power is sent to x-
ray tube via cables
mA (milliamperage)
is sent to filament on
cathode side.
Filament heats up –
electrons are
produced
Negative charge

5. How “X-rays” are created
 Positive voltage (kVp) is applied to anode
 Negative electrons are attracted across the tube
to the positive anode.
 Electrons slow down and finally come to rest
 Electron beam is focused from the cathode to
the anode target by the focusing cup

6.  The distance between filament and the x-ray
tube target is 1 cm.
 Velocity of electron is raised from
zero............half the speed of light

7. E- traveling from cathode to
anode
 Projectile electron interacts with
the orbital electron of the target
atom. This interaction results in
the conversion of electron kinetic
energy into thermal energy
(heat) and electromagnetic
energy in the form of infrared
radiation (also heat) and x-rays.

8. Tube Interactions
Heat (99%)
x-rays (1%)

9. Heat
 Most kinetic energy of projectile e- is converted
into heat – 99%
 Projectile e- interact with the outer-shell e- of the
target atoms but do not transfer enough energy
to the outer-shell e- to ionize
 Outer shell electrons are simply raised to an
excited/ higher energy level.

10. Heat production
 Outer shell electrons immediately drop back to
their normal energy level with the emission of
infrared radiation.
 The constant excitation and return of outer shell
electrons are responsible for most of the heat
generation

11. Heat is an excitation
rather than an ionization

12. Heat production
 Production of heat in the anode increases
directly with increasing x-ray tube current
 Doubling the x-ray tube current doubles the heat
produced
 Increasing kVp will also increase heat production

13.  Efficiency of x-ray production is independent of
the tube current
 Efficiency of x-ray production increases with
increasing kVp.
 At 60 kvp.........0.5%
 At 100 kVp.......1%
 At 20 MV..........70%

14. Characteristic Radiation
 Projectile electron interact with inner shell
electron
 Projectile e- with energy high enough to totally
remove an inner-shell electron of the target atom
e.g. tungsten
 Characteristic x-rays are produced when outer-
shell e- fills an inner-shell

16. Only K-characteristic x-rays of
tungsten
are useful for imaging

17. Bremsstrahlung Radiation
Bremsstrahlung is produced by
projectile e- interacting with
the nucleus of a target atom

18. Bremsstrahlung
is a German
word meaning
“slowed-down
Radiation”

19. Bremsstrahlung Radiation
 A projectile e- that completely avoids the orbital
e- as it passes through a target atom may come
close enough to the nucleus of the atom to come
under the influence of its electric field
 projectile e- kinetic energy to EM energy
 electrostatic force

20. Bremsstrahlung Radiations
 As the projectile electron passes by the nucleus, it
is slowed down and changes its course, leaving
with reduced kinetic energy in a different
direction .
 This loss of kinetic energy reappears as an x-ray.

21. X-ray energy
 Characteristic x-rays have very specific energies.
K-characteristic x-rays require a tube potential of
a least 70 kVp
 Bremsstrahlung x-rays that are produced can
have any energy level up to the set kVp value.
Brems can be produced at any projectile e-
value

22. Discrete spectrum
 Contains only specific values

23. Characteristic X-ray
Spectrum
 Characteristic has discrete energies based on the
e- binding energies of tungsten
 Characteristic x-ray photons can have 1 of 15
different energies and no others

24. Characteristic x-ray
emission spectrum

25. Bremsstrahlung X-ray
Spectrum
 Brems x-rays have a range of energies and form a
continuous emission spectrum

26. Factors Affecting
the x-ray emission
spectrum
 Tube current,
 Tube voltage,
 Added filtration,
 Target material,
 Voltage waveform
 The general shape of an emission spectrum is
always the same, but the position along the
energy axis can change

27. Quality
 The farther to the right the higher the effective
energy or quality

28. Quantity
 The more values in the curve, the higher the x-ray
intensity or quantity

29. mAs
 A change in mA results in the amplitude change
of the x-ray emission spectrum at all energies
 The shape of the curve will remain the same

30. mA increase from 200 to
400

31. kVp
 A change in voltage peak affects both the
amplitude and the position of the x-ray emission
spectrum

32. Filtration
 Adding filtration is called hardening the x-ray
beam because of the increase in average
energy
 Filtration more effectively absorb low-energy x-
rays than high energy x-rays
 Characteristic spectrum is not affected & the
maximum energy of x-ray emission is not affected

33. Filtration
 Adding filtration to the useful beam reduces the
x-ray beam intensity while increasing the average
energy (higher quality)
 Lowering the amplitude and shifting to the right

34. What A does this graph
indicate?

35. Target Material
 The atomic number of the target affects both the
quantity and quality of x-rays
 Increasing the target atomic number increases
the efficiency of x-ray production and the energy
of characteristic and bremsstrhlung x-rays

36. Target material

37. Voltage Waveform
 5 voltage waveforms: half-wave rectification, full-
wave rectification, 3-phase/6-pulse, 3-phase/12-
pulse, and high-frequency.
 Maintaining high voltage potential

38. Voltage generators

39. Factors affecting X-Ray beam
quality and quantity
An increase in Results in
Current(mAs) An increase in quantity; no change in
quality
Voltage (kVp) An increase in quantity and quality
Added filtration A decease in quantity and an increase in
quality
Target atomic number(Z) An increase in quantity and quality
Voltage ripple A decrease in quantity and quality

40. Applications
 Radiographs
A radiograph is an X-ray image obtained by placing a part of the patient in front
of an X-ray detector and then illuminating it with a short X-ray pulse. Bones
contain much calcium, which due to its relatively high atomic
number absorbs x-rays efficiently.
Radiographs are useful in the detection of pathology of the skeletal system as
well as for detecting some disease processes in soft tissue.
 X-Ray Astronomy
X-ray astronomy is an observational branch of astronomy which deals with the
study of X-ray observation and detection from astronomical objects. X-
radiation is absorbed by the Earth's atmosphere, so instruments to detect X-
rays must be taken to high altitude by balloons, sounding rockets, and
satellites. X-ray astronomy is the space science related to a type of space
telescope that can see farther than standard light-absorption telescopes,
such as the Mauna Kea Observatories, via x-ray radiation.

41. Computed Tomography
 Computed tomography (CT scanning) is a
medical imaging modality where tomographic
images or slices of specific areas of the body are
obtained from a large series of two-dimensional
X-ray images taken in different directions . These
cross-sectional images can be combined into a
three-dimensional image of the inside of the body
and used for diagnostic and therapeutic
purposes in various medical disciplines
Fluoroscopy
 Fluoroscopy is an imaging technique commonly
used by physicians or radiation therapists to
obtain real-time moving images of the internal
structures of a patient through the use of a
fluoroscope.

42. Radiotherapy
The use of X-rays as a treatment is known as
radiation therapy and is largely used for the
management (including palliation) of cancer; it
requires higher radiation doses than those received
for imaging alone. X-rays beams are used for
treating skin cancers using lower energy x-ray beams
while higher energy beams are used for treating
cancers within the body such as brain, lung,
prostate, and breast
Other Applications
X-Ray Crystallography
X-Ray microscopic analysis
Air port and border security
Radiation Implosion
Roentgen stereophotogrammetry

43. Diagnostic X-rays (primarily from CT scans due to the large dose
used) increase the risk of developmental problems and cancer in
those exposed.
X-rays are classified as a carcinogen by both the World Health
Organization's International Agency for Research on Experimental
and epidemiological data currently do not support the
proposition that there is a threshold dose of radiation below which
there is no increased risk of cancer .However , this is under
increasing doubt.
The risk of radiation is greater to unborn babies, so in pregnant
patients, the benefits of the investigation (X-ray) should be
balanced with the potential hazards to the unborn fetus.
Drawbacks

44. A radiation burn is damage to the skin or other biological tissue
caused by exposure to radiation. The radiation types of greatest
concern are thermal radiation, radio frequency energy,
ultraviolet light and ionizing radiation. High exposure to X-rays
during diagnostic medical imaging or radiotherapy can also
result in radiation burns.

45. PRESENTED BY,
SAHIL RAO
ASAS