Chapter 1 Book Notes
Nature of our surrouding
matter is anything that occupies space and has mass
all matter is composed of fundamental building blocks called atoms
mass and weight are NOT the same
mass is described by its energy equivalence
weight is force exerted on a body under the influence of gravity
Matter and Energy
matter is anything that occupies space
fundamental complex building blocks of matter are atoms and molecules
the prefix kilo stands for 1000
a kilogram(kg) is equal to 1000 grams(g)
mass remains uncharged regardless of its state it can be transformed from one shape, size, and form to another
energy can exist in several forms
in the SI energy is measured in joules(j)
In X-ray energy is measured in electron volt (eV)
potential energy is the ability to do work by virtue of position (the “potential” to move)
kinetic energy is energy in motion
chemical energy is energy released by a chemical reaction
electrical energy is work that can be done when an electron moves through an electron potential difference (voltage)
thermal energy is energy of motion at the molecular level .. the kinetic energy of molecules
nuclear energy that is contained w/in the nucleus of the atom
electromagnetic energy least familiar form of energy .. most important .. type of energy used in x-ray imaging
electromagnetic energy includes radiowaves, microwaves, ultraviolet, infrared, and visible light .. does not include sound or diagnostic ultrasound
frequently matter and energy exist side-by-side
matter and energy are interchangeable
energy emitted and transferred through space is called radiation
matter that intercepts radiation and absorbs part or all of it is said to be exposed or irradiation
ionizing radiation is a special type of radiation that includes x-rays
ionizing radiation is any type of radiation that is capable of removing an orbital electron from the atom with which it interacts
this type of interaction between radiation and matter is called ionization
ionization occurs when an x-ray passes close to an orbital electron of an atom and transfers sufficient energy to the electron to remove it from the atom
the orbital electron and the atom from which it was separated are called an ion pair
Sources of ionizing radiation
many types of radiation are harmless, but ionizing radiation can injure humans
can be divided into 2 main categories .. natural environmental radiation .. man-made radiation
natural radiation results in an annual does of approx. 3 millisieverts (mSv)
made by human radiation results in 3.1 mSv annually
the mSv is the SI unit of effective dose
natural environmental consists of four .. cosmic rays .. terrestrial radiation .. internally deposited radionuclides .. radon
cosmic rays are particulate and electromagnetic radiation emitted by the sun and stars
terrestrial radiation results from deposits of uranium, throium, and other radionuclides in the earth
largest source of natural radiation is radon
radon is a radioactive gas that is produced by the natural radioactive decay of uranium
radon emits alpha particles which are not penetrating and therefore only contribute to the radiation dose of the lung
these sources result in approx. 300-1000 microsieverts at waist level
diagnostic x-rays constitute the largest man-made source of ionizing radiation
other sources include ( man-made) nuclear power generation, research applications, industrial sources, and consumer items
Discovery of X-rays
during the 1870s and 1880s many university physics labs were investigating the construction of cathode rays through a glass tube known as the Crooks tube
Sir William crooks is who the tube is named after
the tube was the forerunner of modern fluorescent lamps and x-rays tubes
November 8th 1895, wilhelm roentgen was experimenting w/ a type of crooks tube when he discovered x-rays
a plate coasted w/ barium platinocyanide glowed while he was experimenting w/ the fully covered crooks tube
“x” is x-ray stands for the unknown
roentgen reported his findings before the end of 1895
the first medical image was of his wife hand in 1896
Development of medical imaging
there are 3 general types of x-ray exams .. radiography .. fluoroscopy .. computed tomography (CT)
x-ray voltages are measured in kilovolt peak (kVp) .. one kV = 1000v of electric potential
x-ray currents are measured in milliamperage (mA) where the ampere (A) is a measure of electric current
prefix milli = 1/1000 or 0.001
early radiographic procedures often required exposure times of 30mins
one development that helped reduce the exposure the exposure time was the use of a fluorescent intensifying screen in conjunction with the glass photographic plates
Michael pupin is said to have demonstrated the use of a radiographic intensifying screen in 1896
the demonstration of double-emulsion radiography was conducted in 1904 but did not become commercially available until 1918
much of the glass used in radiography came from Belgium and other European countries. this was interrupted during WW1 therefore rads began to make use of film rather than glass plates
the fluoroscope was developed in 1898 by thomas a, eddison
eddison abandoned his x-ray research when his assistant and long-time friend Clarence Dally experienced a severe x-ray burn that eventually required amputation of both arms .. dally died in 1904 and is counted as the first x-ray fatality
a boston dentist William rollins introduced two devices designed to reduce the exposure time of pts. to the x-rays and thereby reduce the possibility of x-ray burn before the turn of the 20th century
rollins found that restricting the x-ray beam with a sheet of lead w/ a hole in the center (a diaphragm) and inserting a leather or aluminum filter improved the diagnostic quality of radiographs
in 1907 H.C. Snook introduced a substitute high-voltage power supply, an interrupts transformer
it was not until the intro of the coolidge tube that the snook transformer was widely adopted
William d. coolidge unveiled his hot-cathode x-ray tube to the medical community in 1913
the hot-cathode tube was a vacuum tube that allowed x-ray intensity and energy to be selected separately & w/ great accuracy
x-ray tubes In use today are refinements of the coolidge tube
in 1913 gustav bucky invented the stationary grid … 2 months later he applied for a patent for a moving grid
in 1915 H. Potter also invented a moving grid
potter recognized bucky’s work and the potter-bucky grid was introduced in 1921
in 1946 the light amplifier tube was demonstrated at the bell telephone lab .. it was adapted by 1950 as image intensifer tube
diagnostic ultrasonography appeared in the 1960s
position emission tomography and x-ray CT were developed in the 1970s
MRI became an accepted modality in the 1980s and currently digital radiography and digital fluoroscopy are rapidly replacing screen-film radiography and image intensified fluoroscopy
Reports of Radiation Injury
the first x-ray fatality in the US occurred in 1904
these injuries usually took form of skin damage (sometimes severe), loss of hair, and anemia
physicians and more commonly pts. were injured primarily because the low energy of radiation then available resulted in the necessity for long exposure time to obtain acceptable images
by 1910 these acute injuries began to be controlled as the biological effects of xrays were scientifically investigated and reported
with the introduction of the coolidge tube and the snook transformer the frequency of reports of injuries to superficial tissues decreased
years later It was discovered that blood disorders such as aplastic anemia and leukemia were occurring in radiologists at a much higher rate than in others
Basic radiation protection
lead impregnated material is used to make aprons and gloves worn by radiologists and radiologic technologists during fluoroscopy and some radiographic procedures
gonadal shielding should be used with all persons of childbearing age or younger when the gonads are in or near the useful x-ray beam and when use of shielding will not interfere with the diagnostic value of exam
the radiographic or CT control console is always located behind a protective barrier
the barrier is lead lined and is equipped with a leaded-glass window
pts who require assistance during examinations should never be held by x-ray personnel .. medical immobilization devices should be used
metal filters usually copper or aluminum are inserted into the x-ray tube housing so that low energy xrays are absorbed before they reach the pt.
collimation restricts the useful x-ray beam to that part of the body to be imaged and thereby spares adjacent tissue from unnecessary radiation exposure
Terminology for radiologic science
two units .. mA and kVp .. by writing 70 kVp instead of 70,000 volt peak
in 1981 the international commission on radiation units and measurements issued standard units based on SI that have been since adopted by all countries except the US
the NCRP and all US scientific medical societies adopted the SI units by the early 1990s
it was not until 2017 that the ARRT adopted SI in their examination process
Air kerma is the kinetic energy transferred from photons to electrons during ionization and excitstion
air kerma is measured in joules per kilogram (J/kg) where 1 J/kg is 1 gray (Gya)
absorbed dose is the radiation energy absorbed per unit mall and has units of J/kg or Gyt
the units Gya and Gyt refer to radiation dose in air and tissue
occupational radiation monitoring devices are analyzed in terms of sievert which is used to express the quantity of radiation received by radiation workers and populations
some types of radiation produce more damage than xrays
the becquerel is the unit of quantity of radioactive material, not the radiation emitted by the material
one becquerel is the quantity of radioactivity in which a nucleus disintegrated every second
radioactivity and the becquerel have nothing to do with xrays