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LC232 X-ray Physics & Principles. Russell L. Wilson C.R.T. Week 1a Chapter 1 Concepts of Radiologic Science. 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.

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lc232 x ray physics principles

LC232 X-ray Physics & Principles

Russell L. Wilson C.R.T.

our surroundings
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.
  • 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.
  • 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.
  • 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.
  • 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.
  • Like matter, energy can be transformed from one type to another.
  • When 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.
mass energy equivalence
Mass-Energy Equivalence
  • Frequently matter and energy exist side by side. The interchangeability was theorized by Albert Einstein’s E=mc2.
  • The Mass-Energy Equivalence is the basis of nuclear power, nuclear medicine and the atom bomb.
  • 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.
  • 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.
ionizing radiation
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.
ionizing radiation1
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.
ionizing radiation2
Ionizing Radiation
  • X-ray and Gamma Rays are the only forms of electromagnetic energy with sufficient energy to ionize matter.
other forms of ionizing radiation
Other forms of Ionizing Radiation.
  • Alpha and Beta Particles are capable of Ionization. These are fast moving particles of matter and Not electromagnetic radiation.
sources of ionizing radiation
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.
sources of ionizing radiation1
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 particles and therefore contributes dose only to the lungs.
  • Naturally occurring radioactive materials contribute to natural exposure.
sources of ionizing radiation2
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.
sources of ionizing radiation3
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.
wilhelm konrad roentgen ph d
Wilhelm Konrad Roentgen, Ph. D
  • Born March 27, 1845
  • Died February 10, 1923
  • The father or modern radiography.
  • Won the Nobel Prize for Physics in 1901
  • Like Chiropractic, X-ray was discovered in 1895.
  • On 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.
  • 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.
  • 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.
  • 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.
the x ray tube development
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.
the first x ray image
The first x-ray image
  • The first human radiograph was taken on Mrs. Roentgen.
  • It was a 15 minute exposure.
the first x ray image1
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
early x ray machine
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.
the development of modern radiography
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
the development of modern radiography1
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.
the x ray tube development1
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.
the development of modern radiography2
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.
the development of modern radiography3
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.
the development of modern radiography4
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 patient’s skull with fluoroscopy.
the development of modern radiography5
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.
development of modern radiography
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.
development of modern radiography1
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.
the x ray tube development2
The X-Ray Tube Development
  • This is the variety of tube designs available in 1948.
  • The Coolidge tube was still available.
the x ray tube development3
The X-Ray Tube Development
  • Two major hazards plagued early radiography.
  • Excessive radiation exposure
  • Electric Shock
development of modern radiography2
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.
development of modern radiography3
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.
development of modern radiography4
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)
development of modern radiography5
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
development of modern radiography6
Development of Modern Radiography
  • 1983 First tabular grain film emulsion ( Kodak) introduced.
  • 1984 Laser stimulable phosphors for direct digital radiographs appear.
reports of injury
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.
reports of injury1
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.
radiation safety
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.
ten commandments of radiation protection
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.
ten commandments of radiation protection1
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.
ten commandments of radiation protection2
Ten Commandments of Radiation Protection
  • The person holdiing 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.
ten commandments of radiation protection3
Ten Commandments of Radiation Protection
  • Always collimate to the smallest field size appropriate to the examination.

California regulations require three borders of collimation visible on the film.

chapter 2

Chapter 2

Radiologic Quantities and Units

basic math in radiography
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.
  • 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
  • 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.
decimal points
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.
decimal points1
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 0.383=6.58568=6.59
  • 3.1416/1.05=2.992=2.99
  • 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.
  • AX=C ax/a=c/a x= c/a
  • When numbers are added to an unknown, x, subtract that number from both sides of the equation.
  • X + A=B X + A - A= B-A X= B - A
  • When an equation is presented in the form of a proportion, cross multiply and then solve for the unknown, x.
  • x/a = b/c cx=a/b x= ab/c
  • If a grid height is 800 µm and the inter-space is 80µm what is the ratio?
  • 800/80 =10:1
number systems
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 form of a number has little use in radiology except for some characteristics of radiographic film.
number systems1
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.
numeric prefixes
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
radiology terms
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
radiologic units
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) issued 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.
roentgen r gy a air kerma
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
roentgen r gy a
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.
rad rad gy t
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.
rad rad gy t1
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.
rem rem seivert sv
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
curie ci becquerel bg
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.
biologic affects of x radiation
Biologic affects of X-radiation
  • Common affects of early radiography included:
    • burns
    • loss of hair
    • anemia
    • aplastic anemia
    • leukemia
basic radiation protection
Basic 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.
basics radiation protection
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.
basics radiation protection1
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.
basics radiation protection2
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.
basics radiation protection3
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.
end of lecture

End of Lecture

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