Concepts Of Radiologic Science Chapter 1 PDF

CHAPTER 1 CONCEPTS OF RADIOLOGIC SCIENCE NATURE OF OUR SURROUNDINGS Thermal/Heat Energy  The energy in motion at the molecular level Matter  Anyth...

CHAPTER 1 CONCEPTS OF RADIOLOGIC SCIENCE NATURE OF OUR SURROUNDINGS Thermal/Heat Energy  The energy in motion at the molecular level Matter  Anything that occupies space & has mass Nuclear Energy  The energy that is contained within the Atoms nucleus of an atom  The building blocks of matter Electromagnetic Energy Mass  The type of energy that is used in an x-rays  The quantity of matter as described by its energy equivalence Theory of Relativity  The distinguishing characteristic of matter  Albert Einstein  States that matter and energy are Weight interchangeable  The force exerted on a body under the influence of gravity Matter-Energy Equivalence  Formula: E=mc2 MATTER AND ENERGY Radiation Matter  The energy emitted & transferred through  Material substance with mass of which space physical objects are composed Visible Light Atoms & Molecules  Radiated by the sun  The fundamental, complex, building blocks of matter Exposed/Irradiated  Matter that intercepts & absorbs radiation Energy  The ability to do work UV Light  SI Unit: joules (J)  It causes sunburn  In Radiology: electron volt (eV) Ionizing Radiation Potential Energy  Any type of radiation that is capable of  The ability to do work by virtue of position removing an orbital electron from the atom with which it interacts Kinetic Energy  Examples: x-rays, gamma rays & UV light  The energy in motion Ionization Chemical Energy  The removal of an electron from an atom  The energy released by a chemical reaction 1 Particulate-type Ionizing Radiation Page Electrical Energy  Examples: alpha & beta particles  The work that can be done when an electron moves through an electric potential difference (V) STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 1 CONCEPTS OF RADIOLOGIC SCIENCE SOURCES OF IONIZING RADIATION Fluorescence  The emission of visible light only during Natural Environmental Radiation stimulation  Annual Dose: 300 mrem/yr  Cosmic Rays: emitted by sun & stars 1901  Terrestrial Radiation: deposits of uranium,  Roentgen received Nobel Prize in Physics thorium & other radionuclides  Internally-deposited Radionuclides: February 1896 potassium-40 (natural metabolites)  He published and produced the first medical  Radon: largest source x-ray image  The first x-ray examination Man-made Radiation  Annual Dose: 60 mrem/yr DEVELOPMENT OF MODERN RADIOLOGY  Diagnostic X-rays: largest source (39 mrem/yr) Radiography  Uses x-ray film & x-ray tube mounted from NCRP the ceiling  National Council on Radiation Protection &  Provides fixed images Measurements Fluoroscopy MSCT  Conducted with an x-ray tube located under  Multislice Spiral Computed Tomography the examination table  Provide moving images Medical Applications of Ionizing Radiation  Annual Dose: 50 mrem/yr X-ray Voltage  Measured in kVp DISCOVERY OF X-RAYS To provide an x-ray beam that is satisfactory Cathode Rays for imaging, you must supply the x-ray tube  Electrons with a high voltage & sufficient electric current! Sir William Crookes  He invented crookes tube X-ray Current Wilhelm Roentgen  Measured in mA  He discovered x-rays Image Blur November 8, 1895  Caused: long exposure time  Discovery of x-rays  Wurzburg University in Germany Michael Pupin (1896) 2  He demonstrated the use of radiographic Page Barium Platinocyanide intensifying screen  The fluorescent material used by Roentgen Charles L. Leonard (1904)  He demonstrated the use of double emulsion film STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 1 CONCEPTS OF RADIOLOGIC SCIENCE Thomas A. Edison (1898) 1970  He developed fluoroscope  PET & CT were developed  Original Fluorescent Material: Barium platinocyanide 1980  Most Recent: Zinc cadmium sulfide &  MRI become an accepted modality calcium tungstate MEG Clarence Dally (1904)  Magnetoencephalography  The first x-ray fatality Because of effective radiation protection William Rollins practices, radiology is now considered a safe  He demonstrated the first application of occupation! collimation & filtration H.C. Snook (1907) Always practice ALARA: keep radiation  He introduced interrupterless transformer exposures As Low As Reasonably Achievable!  Snook transformer Filtration William D. Coolidge (1913)  It absorbs low energy x-rays  He introduced coolidge x-ray tube  Aluminum or copper Radiology emerged as a medical specialty Collimation because of the snook transformer & the  It restricts the useful x-ray beam Coolidge x-ray tube!  It reduces scatter radiation  It improves image contrast Gustav Bucky (1913)  Example: adjustable light-locating  He invented stationary grid collimators (common)  “glitterblende” Intensifying Screen Hollis Potter (1915)  It reduces x-ray exposure by more than 95%  He invented moving grid Protective Apparel 1921  Lead-impregnated material  Potter-Bucky grid was introduced  Examples: gloves & apron Light Amplifier (1946) Gonadal Shielding  He demonstrated at Bell Telephone  It is used with all persons of childbearing Laboratories age 1950 Protective Barriers 3  Light amplifier was adapted for fluoroscopy  Lead-lined with a leaded-glass window Page  Example: radiographic control console 1960  Diagnostic UTZ & gamma camera appeared ARRT  American Registry of Radiologic Technologists STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 1 CONCEPTS OF RADIOLOGIC SCIENCE TEN COMMANDMENTS OF RADIATION PROTECTION 1. Understand & apply the cardinal principles of radiation control: time, shielding & distance. 2. Do not allow familiarity to result in false security. 3. Never stand in the primary beam. 4. Always wear protective apparel when not behind a protective barrier. 5. Always wear an occupational radiation monitor and position it outside the protective apron at the collar. 6. Never hold a patient during radiographic examination. Use mechanical restraining devices when possible. Otherwise, have parents or friends hold the patient. 7. The person who is holding the patient must always wear a protective apron and, if possible, protective gloves. 8. Use gonadal shields on all people of child bearing age when such use will not interfere with the examination. 9. Examination of the pelvis and lower abdomen of a pregnant patient should be avoided whenever possible, especially during the first trimester. 10. Always collimate to the smallest field size appropriate for the examination. 4 Page STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 2 FUNDAMENTALS OF RADIOLOGIC SCIENCE STANDARD UNITS OF MEASUREMENT  Recent Definition: measured by an atomic clock Physics  The study of interactions of matter & energy Measurement  It has a magnitude & a unit Three Base Quantities  Mass, Length & Time Four Systems of Units  MKS Secondary/Derived Quantities  CGS  The combination of one or more base  British quantities  SI Special Quantities SPECIAL QUANTITIES OF RADIOLOGIC  Exposure, Dose, Equivalent Dose & SCIENCE & THEIR UNITS Radioactivity Radiographic Special Units SI Quantities IBWM Exposure C/kg Air kerma (Gya)  International Bureau of Weights & Dose J/kg Gray (Gyt) Measures Equivalent J/kg Sievert (Sv) Dose Length Radioactivity s-1 Becquerel (Bq)  It is based on speed of light  SI Unit: meter (m) The same system of units must always be used  Platinum-Iridium Bar: represents the when one is working on problem or reporting standard unit of length answers!  Redefinition: wavelength of orange light emitted from an isotope of krypton-86 MECHANICS  One Meter: distance traveled by light in 1/299,792,468 Mechanics  The segment of physics that deals with Mass motion at rest (statics) & objects in motion  One Kilogram: mass of 1000 cm3 of water at (dynamics) 4o C  SI Unit: kilogram (kg) Velocity (V)  Platinum-Iridium Cylinder: represents the  It is sometimes called speed standard unit of mass  The rate of change of its position with time  Units of Weight: Newton (N) & pounds (lb)  Formula: V = d/t o d = distance Time o t = time  It is based on the vibration of atoms of  SI Unit: m/s 5 cesium  British Unit: ft/s Page  Original Definition: based on rotation of Earth on its axis (mean solar day) Velocity of Light  Redefinition: a certain fraction of the  Symbol: c tropical year 1900  c = 3x108 m/s or 1.86x105 mi/s STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 2 FUNDAMENTALS OF RADIOLOGIC SCIENCE Average Velocity Newton’s Third Law: Action/Reaction  Symbol: ῡ  For every action, there’s an equal &  Formula: ῡ = (Vf + Vo)/2 opposite reaction o Vf = final velocity o Vo = initial velocity Weight  SI Unit: m/s  A force on a body caused by the pull of  British Unit: ft/s gravity on it  Symbol: Wt Acceleration  Formula: Wt = mg  The rate of change of velocity with time o m = mass  Symbol: a o g = acceleration due to gravity  Formula: a = (Vf – Vo)/t  SI Units: N or lb o Vf = final velocity o Vo = initial velocity Acceleration Due to Gravity o t = time  Symbol: g  SI Unit: m/s2  Constant in SI Unit: 9.8 m/s2  British Unit: ft/s2  Constant in British Unit: 32 ft/s2  Constant Velocity: zero acceleration Weight is the product of mass & the Isaac Newton (1686) acceleration of gravity on earth: 1 lb = 4.5 N!  He presented the fundamental laws of motion Momentum  The product of mass of an object & its Newton’s First Law: Inertia velocity  A body will remain at rest or will continue  Symbol: p to move with constant velocity in a straight  Formula: p = mv line unless acted on by an external force o m = mass o V = velocity Inertia  SI Unit: kg-m/s  The property of matter that acts to resist a  British Unit: lb-ft/s change in its state of motion  Total p before interaction = Total p after interaction Newton’s Second Law: Force  The force (F) that acts on an object is equal Work to the mass (m) of the object multiplied by  The force applied times the distance the acceleration (a) produced  Symbol: W  Formula: W = Fd Force o F = force  A push or pull on an object o d = distance  Symbol: F 6  SI Unit: J  Formula: F = ma Page  British Unit: ft/lb o m = mass o a = acceleration Power  SI Unit: newton (N)  The rate of doing work  British Unit: pounds (lb)  The quotient of work over time  Symbol: P STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 2 FUNDAMENTALS OF RADIOLOGIC SCIENCE  Formula: P = Work/t = Fd/t Calorie o F = force  The heat necessary to raise the temperature o d = distance of 1 g of water through 1o C o t = time  SI Units: J/s or W Three Ways of Heat Transfer  British Unit: hp  Conduction, Convection & Radiation  One hp: 746 W Conduction Energy  The transfer of heat through a material by  The ability to do work touching Law of Conservation of Energy Convection  States that energy may be transformed from  The mechanical transfer of “hot” molecules one form to another but it cannot be created in a gas or liquid from one place to another or destroyed Thermal Radiation Two Forms of Mechanical Energy  The transfer of heat by the emission of  Kinetic & Potential Energy infrared radiation  An x-ray tube cools primarily by radiation Kinetic Energy  The energy associated with the motion of an Temperature object  It is measured with a thermometer  Symbol: KE  3 Scales: Celsius, Kelvin & Fahrenheit  Formula: KE = ½mv2 o m = mass Converting Fahrenheit (F) to Celsius (C) o v2 = velocity squared  Formula: Tc = 5/9(Tf - 32)  SI Unit: J o Tc = temperature in celsius  British Unit: ft-lb o Tf = temperature in fahrenheit Potential Energy Converting Celsius to Fahrenheit  The stored energy of position or  Formula: Tf = 9/5(Tc) + 32 configuration  Symbol: PE Converting Celsius to Kelvin (K)  Formula: PE = mgh  Formula: K = Tc + 273 o m = mass o K = temperature in Kelvin o g = acceleration due to gravity o h = height Approximate Temperature Conversion  SI Unit: J  From oF to oC: subtract 30 & divide by 2  British Unit: ft-lb  From oC to oF: Double, then add 30 7 Heat Cryogens Page  The KE of the random motion of molecules  The cooling agents used in MRI  Unit: calorie  Liquid Nitrogen: boils at 77 K  Liquid Helium: boils at 4 K STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 2 FUNDAMENTALS OF RADIOLOGIC SCIENCE MATHEMATICS FOR RADIOLOGIC Step 3: x = c/a SCIENCE  Second Rule: when numbers are added to an unknown x, subtract that number from both Fractions sides of the equation  The quotient of two numbers Step 1: x + a = b  x/y: numerator/denominator Step 2: x + a – a = b – a Step 3: x = b – a Proper Fraction  Third Rule: when an equation is presented in  The quotient is less than one the form of a proportion, cross-multiply & then solve for the unknown x Improper Fraction Step 1: x/a = b/c (cross-multiplication)  The quotient is greater than one Step 2: cx = ab Step 3: x = ab/c Adding/Subtracting Fractions  Find a common denominator then add or Proportion subtract  It expresses the equality of two ratios  x/y + a/b = xb/yb + ay/yb = (xb + ay)/yb Decimal System Multiplying Fractions  System of numbers that is based on  Simply multiply numerator & denominator multiples of 10  (x/y) x (a/b) = xa/yb Decimal to Exponential Form Dividing Fractions  If there are digits to the left of the decimal  Invert the second fraction & multiply point, the exponent will be positive  x/y ÷ a/b = (x/y) x (b/a) = xb/ya  If there are no nonzero digits to the left of the decimal point, the exponent will be Ratio negative  It expresses the mathematical relationship between two similar quantities Planck’s Constant  Symbol: h  Constant: In addition & subtraction, round to the same o 4.15 x 10-15 Ev-s number of decimal places as the entry with the o 6.63 x 10-34 Js least number of digits to the right of the decimal point! Rules of Exponents  Multiplication: 10x x 10y = 10(x+y)  Division: 10x ÷ 10y = 10(x-y) In multiplication & division, round to the same number of digits as the entry with the  Raising to a Power: (10x)y = 10xy least number of significant digits!  Inverse: 10-x = 1/10x  Unity: 100 = 1 8 Page Three Principal Rules of Algebra Graphing  First Rule: when an unknown x is multiplied  It is based on two axes: x-axis & y-axis by a number, divide both sides of the equation by that number Origin Step 1: ax = c Step 2: ax/a = c/a  The point where the two axes meet STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 2 FUNDAMENTALS OF RADIOLOGIC SCIENCE Ordered Pairs  1 Ci: 3.7 x 1010 nuclei disintegration per  (x-axis, y-axis) second (Bq) Radiologic Units TERMINOLOGY FOR RADIOLOGIC  Roentgen, Rad, Rem, & Curie SCIENCE Roentgen/Exposure STANDARD SCIENTIFIC & ENGINEERING  The unit of radiation exposure or intensity PREFIXES  It is defined as a unit of radiation quantity Multiple Prefix Symbol (1928) 1018 exa E  Applies only to x-rays & gamma rays & 10 15 peta P their interaction with air 1012 tera T  Symbol: R 109 giga G  SI Unit: air kerma (Gya) 10 6 mega M o Adoption of Wagner/Archer Method 103 kilo k  1 R: 2.08 x 108 ip/cm3 of air 10 2 hecto h  1 R: 2.58 x 10-4 C/kg (official) 101 deka da 10-1 deci d Rad/Dose 10-2 centi c  The unit of radiation absorbed dose 10 -3 milli m 10-6 micro µ  The quantity of radiation received by the 10 -9 nano n patient 10-12 pico p  It is used for any type of ionizing radiation 10-15 femto f & exposed matter, not just air 10 -18 atto a  Symbol: rad  SI Unit: gray (Gyt)  Special Unit: J/kg Diagnostic radiology is concerned primarily  1 Rad: 100 erg/g or 10-2 Gyt with x-rays. We may consider:  Erg (J): a unit of energy 1 R = 1 rad = 1 rem or 1 mGya = 1 mGyt = 1 mSv)! Rem/Equivalent Dose  The unit of occupational radiation exposure  It is used to expressed the quantity of radiation received by radiation workers & populations  Symbol: rem  SI Unit: Sievert (Sv)  Special Unit: J/kg  Application: occupational radiation monitors 9 Page Curie (Ci/Bq)  A unit of radioactivity  The unit of quantity of radioactive material  Symbol: Ci  SI Unit: Becquerel (Bq)  Special Unit: s-1 STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 3 THE STRUCTURE OF MATTER CENTURIES OF DISCOVERY  Pudding: a shapeless mass of positive electrification Greek Atom  Atomos means indivisible J.J. Thomson (1890)  Four Substances: earth, water, air, & fire  He investigated the physical properties of  Four Essences: wet, dry, hot, & cold cathode rays (electrons)  He concluded that electrons were integral Substances/Elements parts of all atoms  112 identified  92 naturally occurring Ernest Rutherford (1911)  20 artificially produced  Nuclear model  He disproved Thomson’s model An atom is the smallest particle that has all the  He described the atom as containing a small, properties of an element! dense, positively charged center surrounded by a negative cloud of electrons Subatomic Particles  He called the center of the atom the nucleus  Particles smaller than atom Bohr Atom (1913) Dalton Atom  Miniature solar system  Hook-and-eye affair  He improved Rutherford’s description of the atom John Dalton (1808)  The electrons revolved about the nucleus in  He showed that elements could be classified prescribed orbits or energy levels according to integral values of atomic mass Quantum-chromodynamics (QCD) Dmitri Mendeleev  More accurately described the details of  First periodic table of elements atomic structure Alkali Metals FUNDAMENTAL PARTICLES  Group 1 elements  All soft metals that combine readily with Particle Accelerator oxygen & react violently with water  Atom smasher  It is used in mapping the structure of atomic Halogens nucleus  Group VII elements  Easily vaporized & combine with metals to Nucleons form water-soluble salts  Protons (+) & neutrons (O)  It is composed of quarks & gluons Noble Gas (subatomic particles) 10  Group VIII elements  Highly resistant to reaction with other The fundamental particles of an atom are the Page elements electron, proton & the neutron! Thomson Atom  Plum pudding  Plum: negative electric charges (electrons) STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 3 THE STRUCTURE OF MATTER Electron Number of Protons  Location: orbital shells  Determine the chemical behavior of an atom  Relative: 1  Determine the chemical element  Mass in kg: 9.1 x 10-31  Mass in amu: 0.000549 Isotopes  Number: 0  Same number of protons, but different  Charge: -1 number of neutrons  Symbol: - In their normal state, atoms are electrically Proton neutral; the electric charge on the atom is  Location: nucleus zero!  Relative: 1836  Mass in kg: 1.673 x 10-27 Electron Arrangement  Mass in amu: 1.00728  The number of electrons in the outermost shell of an atom = group in the periodic  Number: 1 table & determines the valence of an atom  Charge: 1  The number of outermost electron shell of  Symbol: + an atom = period in the periodic table Neutron Maximum Electrons Per Shell  Location: nucleus  Formula: 2n2  Relative: 1838  Mass in kg: 1.675 x 10-27 Principal Quantum Number  Mass in amu: 1.00867  The shell number (n)  Number: 1  Charge: 0 No outer shell can contain more than eight  Symbol: O electrons! Atomic Mass Unit Orderly Scheme of Atomic Progression  The mass of a neutral atom of an element  Interrupted in fourth period  Symbol: amu  1 amu: ½ the mass of a carbon-12 atom Transitional elements  Atoms associated with the phenomenon Atomic Mass Number mentioned above  Number of protons plus number of neutrons in the nucleus Centripetal Force  Symbol: A  Center-seeking force  Formula: protons + neutrons  The force that keeps an electron in orbit ATOMIC STRUCTURE Centrifugal Force 11  Flying-out-from-the-center force Page The atom is essentially empty space!  The force that causes an electron to travel straight and leave the atom Neutral Atom  Same number of electrons & protons STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 3 THE STRUCTURE OF MATTER Electron Binding Energy Protocol for Representing Elements in a Molecule  The strength of attachment of an electron to  Upper Left: atomic mass (A) the nucleus  Lower Left: atomic number (Z)  Symbol: Eb  Upper Right: valence state (+/-)  Lower Right: number of atoms/molecules Tungsten (W-74) & Molybdenum (Mo-42)  The primary constituents of x-ray tube target CHARACTERISTICS OF SOME ELEMENTS IMPORTANT TO RADIOLOGIC SCIENCE Barium (Ba-56) & Iodine (I-53) Naturally  Radiographic & fluoroscopic contrast agents Chemical Element Z A Occurring Symbol Isotopes Carbon (C-6) Beryllium Be 4 9 1  The important component of human tissue Carbon C 6 12 3 Oxygen O 8 16 3 Ionization Potential Aluminum Al 13 27 1  The amount of energy (34 keV) necessary to Calcium Ca 20 40 6 ionize tissue atoms Iron Fe 26 56 4 Copper Cu 29 63 2 ATOMIC NOMENCLATURE Molybdenum Mo 42 98 7 Ruthenium Ru 44 102 7 Chemical Symbols Rhodium Rh 45 103 5  The alphabetic abbreviations of an element Silver Ag 47 107 2 Tin Sn 50 120 10 Number & Arrangement of Electrons Iodine I 53 127 1  It determines the chemical properties of an Barium Ba 56 138 7 element Tungsten W 74 184 5 Rhenium Re 75 186 2 Atomic number Gold Au 79 197 1  Number of Protons Lead Pb 80 208 4  Symbol: Z Uranium U 92 238 3 Atomic Mass Number CHARACTERISTICS OF VARIOUS  Number protons plus number of neutrons NUCLEAR ARRANGEMENTS  Symbol: A Atomic Atomic Neutron Arrangement Mass Number Number The atomic number & the precise mass of an Number atom are not equal! Isotope same different different Isobar different same different Carbon-12 Atom Isotone different different same  Its A & Z are equal Isomer same same same 12  Rationale: it is the arbitrary standard for Page atomic measure Technetium-99m (Tc-43)  It decays to technetium-99 Elemental Mass  Energy Emitted:140 keV gamma rays  It is determined by the relative abundance of isotopes & their respective atomic masses STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 3 THE STRUCTURE OF MATTER COMBINATIONS OF ATOMS transforms itself into another atom to reach stability Molecules  It occurs when the nucleus contains too few  The group of atoms of various elements or too many neutrons  The smallest unit of a compound Radioisotopes  Radioactive atoms that have the same Sodium chloride (NaCl) number of protons  Common table salt Uranium (U-92) & Carbon-14 Chemical Compound  Two primary source of naturally occurring  Any quantity of one type of molecule radioisotopes CHON (C-6, H-1, O-8, N-7) Beta Emission  Carbon, Hydrogen, Oxygen, Nitrogen  It occurs in all radioisotopes  90% of the human body  It occurs more frequently than alpha emission Water  Results:  80% of the human body o Loss of small quantity of mass & one unit of negative electric charge Covalent Bond o To increase the Z by one while A  The chemical union between atoms formed remains the same by sharing one or more pairs of electrons o Changing of an atom from one type  Example: H2O of element to another  Neutron undergoes conversion to a proton Ionic Bond  The bonding that occurs because of an Alpha Emission electrostatic force between ions  It occurs only in heavy radioisotopes  Example: NaCl  It is much more violent process  It is consists of 2 protons & 2 neutrons Sodium bicarbonate (NaHCO3)  Atomic Mass Number: 4  Baking soda  Results: o Nucleus loses 2 units of positive The smallest particle of an element is an atom; charge & 4 units of mass the smallest particle of a compound is a o Chemically different atom & an molecule! atom lighter than 4 amu RADIOACTIVITY Radioactive Half-life  The time required for a quantity of Radioactivity radioactivity to be reduced to one-half its  The emission of particles & energy in order original value 13 to become stable  Symbol: T1/2 Page  I-131: T1/2 = 8 days Radioactive Decay/Radioactive Disintegration  C-14: T1/2 = 5730 days  The process by which the nucleus spontaneously emits particles & energy & STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 3 THE STRUCTURE OF MATTER Radioactive Decay Law  Antimatter  It described the rate of radioactive decay & the quantity of material present at any given Electromagnetic Radiation time  Examples: x-rays & gamma rays  Formula: Activity Remaining = Original  They only differ in origin Activity (0.5)n  It is often called photons  n: number of half lives  It has unlimited range in matter TYPES OF IONIZING RADIATION Photons  No mass & no charge Five Physical Characteristics  Travel at the speed of light (c)  Mass, Energy, Velocity, Charge & Origin  c: 3 x 108 m/s or 1.86 x 105 mi/s Particulate Radiation X-rays and gamma rays are the only forms of  It has finite range in matter ionizing electromagnetic radiation of  Examples: alpha & beta Particles radiologic interest! Alpha Particle X-rays  Equivalent to a helium nucleus  Symbol: X  It contains 2 protons & 2 neutrons  Mass: 0  Symbol: α  Charge: 0  Mass: 4 amu  Origin: electron cloud  Charge: +2  Energy: 0-25 MeV  Origin: nucleus of heavy radioactive nuclei  Range: 0-100 m (air); 0-30 cm (soft tissue)  Energy: 4-7 MeV  Ionization Rate: 100 ip/cm (equal to beta  Range: 1-10 cm (air); Primary Voltage  It allows a wide range of time intervals to be (V) selected  Secondary Current (mA) < Primary Current  It is used for rapid serial exposures (A)  Secondary Windings > Primary Windings Most exposure timers are electronic & are  Voltage Waveform: sinusoidal controlled by a microprocessor!  Amplitude: only difference in the primary & secondary waveform mAs Timer  Functions: Turns Ratio o Monitors the product of mA &  The ratio of the number of secondary exposure time windings to the number of primary windings o Terminates exposure when desired  Examples: 500:1 & 1000:1 mAs value is attained  Directly proportional to the voltage o Provides the highest safe tube  Inversely proportional to the current current for the shortest exposure for any mAs selected Voltage Rectification  Location: secondary side of the high-voltage  It ensures that electrons flow from cathode transformer to anode only  Applications: o Falling-load Rectification o Capacitor discharge imaging system  The process of converting alternating current (AC) to direct current (DC) Automatic Exposure Control (AEC)  A device that measure the quantity of Rectifier radiation that reaches the image receptor  An electronic device that allows current  It automatically terminates the exposure flow in only one direction when the image receptor has received the required radiation intensity Diode  An electronic device that contains two Solid-state Detectors electrodes  It is used to check timer accuracy (as short as 1 ms) Valve Tube  A vacuum tube (original rectifier) HIGH VOLTAGE GENERATOR  It replaced by solid-state rectifier o Composition: silicon High Voltage Generator  It increases the output voltage from the 27 Semiconductor autotransformer to the kVp necessary for x-  Lies between insulators & conductors ray production Page  2 Types: p-type & n-type Three Primary Parts P-type Semiconductor  High Voltage Transformer, Filament  Have loosely bound electrons (free to move) Transformer & Rectifiers  Have spaces called holes (no electrons) STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 6 THE X-RAY IMAGING SYSTEM  Holes: as mobile as electrons Extinction Time  Ending an exposure Solid-state p-n Junction  N-type material placed in contact with p- High Frequency Generator type crystal  It produces a nearly constant potential  It conducts electricity in only one direction voltage waveform  Solid-State Diode: a rectifier  Advantages: o Much smaller & less costly & more Electron flow is used when medical imaging efficient systems are described! o Improves image quality at lower patient radiation dose Half-Wave Rectification  It uses inverter circuits  The voltage is not allowed to swing negatively during the negative half of its Inverter Circuit cycle  A high-speed switchers or choppers that  Diodes: 0, 1 or 2 convert DC into a series of square pulses  60 pulses/second  Disadvantages: Full-wave rectification or high-frequency o It wastes half the supply of power voltage generation is used in almost all o It requires twice the exposure time stationary x-ray! Full-Wave Rectification Capacitor Discharge Generator  The negative half-cycle corresponding to the  Tube voltage falls during exposure inverse voltage is reverse  Approximately 1 kV/mAs  Diodes: 4  120 pulses/second Grid-Controlled X-ray Tube  Advantage:  An automatic lead beam stopper o Exposure time reduced in half  It stops continues x-ray emission of capacitor bank Single-Phase Power  It is designed to be turned on & off very  It results in a pulsating x-ray beam rapidly  Disadvantage:  Applications: o X-ray produced has a value near zero o Portable capacitor discharge imaging systems Three-Phase Power o Digital subtraction angiography  The voltage impressed across the x-ray tube o Digital radiography is nearly constant o Cineradiography  6 pulses/1/60 second  Grid: it refers to an element in the tube that  Advantage: acts as a switch 28 o Voltage never drops to zero during exposure Less Voltage Ripple Page  Disadvantages:  Greater radiation quantity o Its size & cost o Higher efficiency of x-ray production Initiation Time  Starting an exposure STEWART C. BUSHONG SUMMARIZED BY: MEYNARD Y. CASTRO  CHAPTER 6 THE X-RAY IMAGING SYSTEM  Greater radiation quality o Fewer low-energy projectile electrons pass from cathode to anode CHARACTERISTICS OF HIGH FREQUENCY X-RAY GENERATORS Frequency Range Inverter Features