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LC232 X-ray Physics

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Title: LC232 X-ray Physics


1
LC232 X-ray Physics Principles
  • Russell L. Wilson C.R.T.

2
Week 1a Chapter 1 Concepts of Radiologic Science
3
Our Surroundings
  • Everything in the universe can be classified as
    matter or energy.
  • Matter is anything that occupies space and has a
    shape or form.
  • Matter has Mass. This is the quantity of
    matter.The physical properties can be transformed
    in size, shape and form.

4
Energy
  • Energy is the ability to do work. Energy can
    exist in many forms.
  • Potential Energy is the ability to do work by
    virtue of position.
  • Kinetic energy is the energy of motion. It is
    possessed by all matter in motion.

5
Energy
  • Chemical Energy is the energy released by way of
    a chemical reaction.
  • Electrical Energy represents the work that can be
    done when an electron or an electronic charge
    moves through an electronic potential.

6
Energy
  • Thermal (heat) Energy is the energy of motion at
    the atom or molecule level. Thermal energy is
    measured by temperature. The faster the atoms or
    molecule are moving, the more thermal energy or
    heat will be produced.

7
Energy
  • Nuclear Energy is the energy contained in the
    nucleus of the atom.
  • Electromagnetic Energy is the most important
    type of energy for radiology.It is the type of
    energy in an x-ray. In addition to x-ray,
    electromagnetic energy includes radio waves,
    microwaves and visible light.

8
Energy
  • Like matter, energy can be transformed from one
    type to another.
  • Then taking an x-ray, we start with electrical
    energy that is transformed to electromagnetic
    energy. After the x-ray passes through matter, it
    is converted to chemical energy in the film.

9
Mass-Energy Equivalence
  • Frequently matter and energy exist side by side.
    The interchangeability was theorized by Albert
    Einsteins Emc2.
  • The Mass-Energy Equivalence is the basis of
    nuclear power, nuclear medicine and the atom bomb.

10
Radiation
  • Energy emitted and transferred through matter is
    called Radiation.
  • Like ripples or waves are generated when a stone
    is dropped into a still pond.
  • Visible light is a form of electromagnetic energy
    radiated from the sun.

11
Radiation
  • Electromagnetic radiation is referred to as just
    radiation.
  • Matter that intercepts radiation and absorbs part
    or all of it is said to be exposed or irradiated.
  • During radiography, the patient is irradiated.

12
Ionizing Radiation
  • Ionizing radiation is a special type of radiation
    that includes x-rays. It is any kind of
    radiation capable of removing an orbital electron
    from an atom with which it interacts.

13
Ionizing Radiation
  • Ionizing radiation passes close enough the the
    atom with sufficient energy to remove an electron
    from the atom. The free orbiting electron and
    atom become Ion Pairs.

14
Ionizing Radiation
  • X-ray and Gamma Rays are the only forms of
    electromagnetic energy with sufficient energy to
    ionize matter.

15
Other forms of Ionizing Radiation.
  • Alpha and Beta Particles are capable of
    Ionization. These are fast moving particles of
    matter and Not electromagnetic radiation.

16
Sources of Ionizing Radiation
  • Many forms or radiation are harmless but Ionizing
    radiation can injure humans.
  • Natural sources of radiation results in the
    annual exposure of about 300 mrad (3 mGy)
  • A mrad is 1/1000 of a rad. The Rad is the unit of
    radiation absorbed dose.

17
Sources of Ionizing Radiation
  • Radon is the largest component of natural
    radiation. All earth-based materials such as
    concrete, wall board and bricks contain radon. It
    emits alpha particle and therefore contributes
    dose only to the lungs.
  • Naturally occurring radioactive materials
    contribute to natural exposure.

18
Sources of Radiation Exposure
19
Sources of Ionizing Radiation
  • Elevation from sea level will impact exposure to
    natural gamma exposure.
  • Flying cross country or living in the mountains
    will result in a higher level of background
    exposure.
  • During the era of above ground nuclear testing,
    everyone was exposed to 5 mrads/ year.

20
Sources of Ionizing Radiation
  • During the Chernobyl Disaster, the populations
    near the plant received very high exposures.
  • In some areas of India, background radiation is
    over 500 mrads from uranium.
  • Medically employed x-rays constitute the largest
    source of man-made ionizing radiation.

21
The Development of Radiology
  • A brief history

22
Wilhelm Konrad Roentgen, Ph. D
  • Born March 27, 1945
  • Died February 10, 1923
  • The father or modern radiography.
  • Won the Nobel Prize for Physics in 1901

23
History
  • Like Chiropractic, X-ray was discovered in 1895.
  • One November 8, 1895, Dr. Wilhelm Roentgen in
    Germany was experimenting with a Crookes or
    cathode ray tube.
  • The room was dark and the tube was enclosed with
    black photographic paper.

24
History
  • On a table next to the tube was a plate coated
    with barium platinocynide a fluorescent material.
  • Dr. Roentgen observed that when the Crookes tube
    was on, the fluorescent material luminated
    regardless of how far the plate was from the
    tube.

25
History
  • He placed various materials between the tube and
    the plate. The X-light easily penetrated
    cardboard, books, wood and cloth.
  • He had more trouble penetrating metals with the
    densest being opaque.

26
History
  • When he placed his hand near the plate, he
    discovered that skin was almost transparent while
    bone was fairly opaque.
  • In his experiments, he discovered many of the
    principles that we use today.
  • The discovery of X-ray was basically an accident.

27
The X-Ray Tube Development
  • Dr. Roentgen used a Crookes-Hittorf tube to make
    the first x-ray image.
  • Note that there is no shielding around the tube.

28
The first x-ray image
  • The first human radiograph was taken or Mrs.
    Roentgen.
  • It was a 15 minute exposure.

29
The first x-ray image
  • For the first time, we were able to see inside
    the body without surgery.
  • Early x-rays were taken on glass photographic
    plates

30
Early X-ray Machine
  • First U.S. x-ray exam on Feb. 3, 1896 was a wrist
    x-ray taken at Dartmouth College.
  • The maximum power was 50 kV or 50,000 volts and
    low mA.

31
The Development of Modern Radiography
  • Coil and battery type x-ray machine used in the
    Spanish American War of 1898.
  • A series of batteries provided DC power to a
    coil. Operating cost 0.11 per hour

32
The Development of Modern Radiography
  • Static type machine also used by the US Army
    during the Spanish American War.
  • A motor produced DC power for the x-ray tube.

33
The X-Ray Tube Development
  • The Coolidge Hot cathode tube was a major
    advancement in tube Design. The radiator at the
    end of the anode cool the anode.

34
The Development of Modern Radiography
  • This was the recommended design of an early x-ray
    room.
  • The operator had to watch the glow of the tube
    and adjust power during the exposure.

35
The Development of Modern Radiography
  • Lead was placed between the tube and the
    operator.
  • A mirror was used to observe the patient and
    tube.
  • To test the machine, the operator x-rayed their
    forearm.

36
The Development of Modern Radiography
  • If they could see a button through the radius, it
    was operating properly.
  • Another test was to see a watch through the
    patients skull with fluoroscopy.

37
The Development of Modern Radiography
  • 1896 First medical applications of x-ray in
    diagnosis therapy.
  • 1905 Einstein introduced his theory of relativity
  • 1907 Snook interrupterless transformer to make
    high voltage. The capabilities of the transformer
    exceeded the capacity of Crookes tubes.

38
Development of Modern Radiography
  • 1913 Bohr theorizes his model of the atom.
  • 1913 The Crookes cathode ray tube was replaced by
    Coolidge hot cathode tube.
  • 1913 Dr. Gustave Bucky built the first grid.
  • 1918 Double emulsion film by Kodak.
  • 1920 Dr. Hollis Potter put a Grid in a moving
    cabinet to remove grid lines.

39
Development of Modern Radiography
  • 1922 Compton describes scattering of x-rays
  • 1928 The roentgen is defined as the unit of
    measurement of x-ray intensity.
  • 1929 Rotating anode x-ray tube introduced.
  • 1930 Tomography is demonstrated by several
    investigators.

40
The X-Ray Tube Development
  • This is the variety of tube designs available in
    1948.
  • The Coolidge tube was still available.

41
The X-Ray Tube Development
  • Two major hazards plagued early radiography.
  • Excessive radiation exposure
  • Electric Shock

42
Development of Modern Radiography
  • 1942 Morgan exhibits the first electronic
    phototimer.
  • 1942 First automatic film processor
  • 1948 First fluoroscopic image intensifier.
  • 1953 Rad is officially adopted as the unit of
    absorbed dose.

43
Development of Modern Radiography
  • 1956 First automatic roller transport film
    processor introduced by Kodak
  • 1963 Single photon emission computed tomography
    demonstrated.
  • 1965 Ninety second film processor introduced.

44
Development of Modern Radiography
  • 1966 Diagnostic ultrasound enters routine use.
  • 1972 Rare earth radiographic intensifying screen
    are introduced.
  • 1973 Hounsfield completes development of the
    first computed tomography (CT) scanner (EMI)

45
Development of Modern Radiography
  • 1973 Damadian and Lauterbur produce the first
    magnetic resonance image (MRI)
  • 1980 First superconductor MR imager introduced
  • 1981 The International System of Units (SI) is
    adopted by the ICRU
  • 1983 First tabular grain film emulsion

46
Development of Modern Radiography
  • 1983 First tabular grain film emulsion
    ( Kodak) introduced.
  • 1984 Laser stimulable phosphors for direct
    digital radiographs appear.

47
Reports of Injury
  • The first fatality from radiography occurred in
    1904 when Clarence Daly died from complications
    from experiments in fluoroscopy.
  • Injuries were frequent in the early years in the
    form of
  • Burns, loss of hair and anemia.
  • By 1910, the more powerful Coolidge tube and
    Snook transformer reduced the superficial tissue
    injuries.

48
Reports of Injury
  • Years later blood disorders such as aplastic
    anemia and leukemia were developing in
    radiologists.
  • This resulted in the development of lead aprons
    and gloves.
  • Workers were routinely evaluated for signs of
    effects of radiation exposure and provided
    detection devices.

49
Radiation Safety
  • The attention of radiation safety has been very
    effective. Today it is considered as a safe
    occupation.
  • Today the emphasis has shifted back to the
    patient.
  • The principle of radiation safety is called ALARA
    or As Low As Reasonably Achievable.

50
Ten Commandments of Radiation Protection
  • Understand and apply the cardinal principles of
    radiation control time, distance and shielding.
  • Do not allow familiarity to result in false
    security.
  • Never stand in the primary beam.
  • Always wear protective apparel when not behind a
    protective barrier.

51
Ten Commandments of Radiation Protection
  • Always wear a radiation monitor and position it
    outside the protective apron at the collar.
  • Never hold a patient during a radiographic
    procedure. Use mechanical restraining devices
    when possible. Otherwise, have parents or friends
    hold the patient.

52
Ten Commandments of Radiation Protection
  • The person hold the patient must wear a
    protective apron and if possible protective
    gloves.
  • Use gonadal shields on all patients of child
    bearing age when it will not interfere with the
    examination.
  • Examinations of the abdomen or pelvis should be
    avoided on pregnant patients especially during
    the first trimester.

53
Ten Commandments of Radiation Protection
  • Always collimate to the smallest field size
    appropriate to the examination.
  • California regulation require three borders of
    collimation visible on the film.

54
Chapter 2
  • Radiologic Quantities and Units

55
Basic math in radiography
  • In radiography, some basic math skill are
    required.
  • Some x-ray controls use fractions or decimals to
    enter exposure factors.
  • The geometry of radiography also requires some
    basic math skill.
  • Adjusting factors for changes in distance or
    patient size requires math skill.

56
Fractions
  • Fractions are used generally for exposure time on
    older single phase machines. Therefore the
    ability to multiply a fraction and a whole number
    is important.
  • numerator
  • Fraction ----------------- x/y
  • denominator

57
Fractions
  • A special application of fractions in radiology
    is the ratio.
  • A ratio expresses the mathematical relationship
    between similar quantities.
  • Fractions can be easily converted to decimals if
    the denominator is a power of 10. Otherwise a
    calculator can be used.

58
Decimal Points
  • One can easily get carried away with decimal
    points when using a calculator.
  • Too many points imply greater precision that is
    really there.
  • Addition and subtraction round to the same number
    of points as the entry with the least number of
    decimal points to the right of the decimal place.

59
Decimal Points
  • In multiplication and division, round to the same
    number of digits as the entry with the least
    number of significant figures.
  • 17.24 x 0.3836.585686.59
  • 3.1416/1.052.9922.99

60
Algebra
  • The rules of algebra provides definite ways to
    manipulate fractions and equations to solve for
    an unknown.
  • When an unknown, x, is multiplied by a number,
    divide both sides of the equation by that number.
  • AXC ax/ac/a x c/a

61
Algebra
  • When numbers are added to an unknown, x, subtract
    that number from both sides of the equation.
  • X AB X A - A B-A X B - A

62
Algebra
  • When an equation is presented in the form of a
    proportion, cross multiply and then solve for the
    unknown, x.
  • x/a b/c cxab x ab/c
  • If a grid height is 800 µm and the inter-space is
    80µm what is the ratio?
  • 800/80 101

63
Number systems
  • We use a decimal system where the number is based
    upon multiples of 10.
  • While used in many applications in science and
    physics, the logarithmic for of a number has
    little use in radiology except for some
    characteristics of radiographic film.

64
Number systems
  • 1010
  • The superscript on 10 in the exponential form
    of numbers is called the exponent.
  • It is also referred to as the power of ten
    notation or scientific notation.
  • It makes it easier to write very large or very
    small numbers.

65
Numeric Prefixes
  • In radiology we often must describe very large
    or very small multiples of a standard unit. The
    two most common units are milliapmeres (mA) and
    kilovolt peak (kVp).
  • 70,000 volts 70 x 103 volts 70 kVp
  • The size of a blood cell is about 10 micrometers
    (µ)
  • 10µ 10 x 10-6m 105 0.00001m

66
Numeric Prefixes
67
Radiology Terms
  • The four most common terms for defining radiation
    exposure are
  • Exposure Roentgen Air kerma or gray in air
  • Absorbed dose rad gray in tissue
  • Effective dose rem Seivert
  • Radioactivity currie becquerel

68
Radiologic Units
  • The four units used to measure radiation should
    become a familiar part of your vocabulary. The SI
    International System equivalents will be shown in
    parenthesis.
  • In 1981 the International Commission on Radiation
    Units and Measurement (ICRU) issues standard
    units and they were adopted by all countries
    except the United States. Scientific journal
    usually use the SI but regulatory agencies and
    the governments used the standard units.

69
Roentgen (R) (Gya) Air Kerma
  • The intensity of radiation is measured in
    roentgen or R.
  • One R equals the intensity of radiation that will
    create 2.08 x 1018 ion pairs in a cubic
    centimeter of air.
  • Official definition is 1R 2.58 x 10-4 C/kg
  • To convert R to Gya multiply R x 0.01

70
Roentgen (R) (Gya)
  • Roentgen refers to x-rays and gamma rays and
    their interaction with air.
  • X-ray out put is generally referred to as mR.
  • Radiation exposure rate meters are calibrated in
    R.

71
Rad (rad) (Gyt)
  • For all practical purposes, in diagnostic
    radiology 1R 1 rad 1 rem
  • Biologic effects are usually related to the
    absorbed dose. The rad is the term used to
    describe the amount of radiation received by the
    patient.
  • Roentgen used for gamma or x-ray exposure in air.

72
Rad (rad) (Gyt)
  • The rad is used for any type of ionizing
    radiation and any exposed matter.
  • 1 rad 100 erg/g where erg (joule) is a unit of
    energy and gram ( kilogram) is a unit of mass.
  • 1rad 10-2 Gyt or 0.01 Gyt The t refers to
    tissue where the a stands for air.

73
Rem (rem) Seivert (Sv)
  • The rem is used to express the quantity of
    radiation received by radiation workers and
    populations.
  • Some types of radiation produce more damage than
    x-rays. The rem accounts for these differences
    in biologic effectiveness.
  • The rem is the unit of occupational radiation
    exposure express as effective dose (E).
  • 1 rem 10-2 Sv 0.01 Sv

74
Curie (Ci) Becquerel (Bg)
  • The curie is the unit of radioactivity.
  • One curie is the quantity of radioactivity in
    which 3.7 x 1010 nuclei disintegrate every
    second.
  • One Becquerel 3.7 x 1010 Ci
  • The milliCurie (mCi) and microcurie (µCi) are the
    most common quantities of radioactive material.
  • Radioactivity and curie have nothing to do with
    x-ray.

75
Special quantities of Radiologic Sciences
76
Occupational Exposure
77
Biologic affects of X-radiation
  • Common affects of early radiography included
  • burns
  • loss of hair
  • anemia
  • aplastic anemia
  • leukemia

78
Basics Radiation Protection
  • It is easy to reduce exposure for the patient and
    operator when items designed for this purpose are
    used and understood.
  • Filtration usually aluminum will absorb the soft
    rays to harden the beam.
  • Collimation or cones will restrict the beam.

79
Basics Radiation Protection
  • Collimation will restrict the beam. The use of
    adjustable lead shutters with light control or
    cone will limit the beam to the area of interest.
  • Intensifying screen Today it is the light from
    the screens inside the cassette that produces the
    image on the film.

80
Basics Radiation Protection
  • Intensifying screen Exposure is reduced by 95
    compared to exams performed without screens.
  • Protective apparel Lead impregnated rubber
    aprons are used to protect the operator inside
    the x-ray room.

81
Basics Radiation Protection
  • Gonad shielding Lead is used to block the beam
    from exposing the gonads.
  • Protective barrier Lead is used to protect the
    operator. When behind the barrier, the operator
    should not receive any exposure.
  • Restricted access Only the patient should be in
    the room during exposure.

82
Basics Radiation Protection
  • Restricted access Only the patient should be in
    the room during exposure.
  • If the patient needs to be held during an
    x-ray, The family of the patient and not the
    operator should hold the patient.
  • Lead apron and gloves should be worn by those
    holding the patient. Stay out of the path of the
    beam.

83
End of Lecture
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