RAD 350 Chapter 1
I.
Matter – anything that occupies space;
a. Consists of atoms and molecules
b. Primary characteristic is mass – the quantity of matter contained in a
physical object
i. Weight describes mass in an area with a gravitational “pull” (mass
on earth and the moon is the same – but the gravitational pull is
different
ii. Mass also remains the same regardless of physical form (solid,
liquid, gas) and has the same number of particles in any form
II. There are 7 forms of energy
a. Potential – capacity to do work by virtue of position
b. Kinetic – energy of motion
c. Chemical – energy released via chemical reaction
d. Electrical – electrons moving
e. Thermal – heat (motion at the molecular level)
f. Nuclear – energy in the nucleus of an atom
g. Electromagnetic – x-ray and magnetic energy (uv rays, radio waves
microwaves, infrared and visible light)
III. MASS-Energy: Einstein’s theory of relativity E=MC2
a. E= energy, M= mass, C= speed of light ( 3 X 1010 cm/sec; 3 X 108 m/sec)
IV. Radiation = Energy emitted and transferred through space.
a. Electromagnetic radiation (sunlight, microwaves, etc.) has properties of
BOTH electricity and magnetic; solar radiation, etc., CAN BE REFLECTED!
b. DRAW AND LABEL/DESCRIBE AN ATOM!
i. Ionizing radiation = electromagnetic radiation capable of
removing an electron from an atom – results in an ion pair
The ejected electron (negative ion) and the remaining atom with
one more positive charge than negative (positive ion). Ionizing
radiation cannot be reflected, but can interact with matter and
change directions
V.
VI.
Sources of ionizing radiation:
Natural sources:
Cosmic rays = emitted by the sun and stars
Terrestrial = emitted from deposits of uranium,
thorium and other substances in the earth (radon gas
is the largest source – is decayed uranium by-product
and emits alpha particles
Man made ionizing radiation: Medical/dental – 11% of our
annual radiation dose comes from man-made. Also manmade includes airport screening, nuclear power, research,
industrial sources and consumer items (watch dials, exit
signs, smoke detectors, etc.)
Wilhelm Conrad Roentgen discovered x-rays on Nov. 8, 1895 while
working with a Crooks tube in Wurzburg Germany. Many scientists were
playing with Crooks tubes at the time. Roentgen covered the tube with
paper and noticed a glass plate covered with barium platinocyanide on a
nearby table would glow whenever the tube was energized.
a. Interesting facts about the discovery:
i. Were discovered by accident – NOT invented!
ii. Within one month of the discovery, Roentgen had discovered ALL
of the x-ray properties we know today!
1. Injuries to humans began immediately: erythema (skin
reddening), alopecia (loss of hair), anemia (low blood
counts)
Modern Radiography – radiography and fluoroscopy (moving images like a
GI study) Discuss a typical fluoro unit!!!
a. Uses thousands of volts of electricity – “KILOVOLTS” (one kV = 1,000 V
of electric potential) KILO = 1,000
b. Uses current in MILLIAMPS – 1/1,000 of an AMP; MILLI = 1/1,000
c. Intensifying screens – convert x-rays to visible light which exposes the
film
d. Double emulsion film/glass plates further increased the speed of the
process of x-ray imaging and cut radiation exposure in half (1918)
i. Glass plates were discontinued by using a flexible base (cellulose
nitrate) coated with silver halide/bromide crystals. BUT the
Cellulose nitrate was highly flammable and was replaced by
cellulose acetate in 1923. X-ray film base now is made of
polyester
Fluoroscope was invented by Thomas Edison in 1898 (Edison’s assistant
died of radiation related problems in 1904 and Edison stopped all
radiation experiments.
Collimation = controlling the AREA the x-ray beam is permitted to
expose the patient
Filtration of the x-ray beam = absorb LOW energy, non useful x-ray
wavelengths PRIOR to exposing the patient!
Potter-bucky diaphragm
TWO IMPORTANT ITMES ENABLED RADIOGRAPHY TO EVOLVE: SNOOK
TRANSFORMER AND COOLIDGE TUBE
VII. Radiation protection – due to the care of technologists, radiologists and
radiobiologists, medical imaging is considered a safe profession.
a. Practice the “ten commandments of radiation protection” and practice
them! Do NOT become complacent!!!
b. Three “cardinal safety principles: TIME, DISTANCE and SHIELDING are
the standard of safety from ionizing radiation.
c. ALARA principle – as low as reasonably achievable for radiation dose as
there is NO SAFE DOSE AMOUNT!!!
d. Ways to minimize the dosage to you and radiation workers: time,
distance and shielding: wear a lead apron, eyeglasses and gloves during
fluoro, wear a lead apron when doing portables, never hold patients
and always collimate.
e. For patients – always collimate (single MOST important thing a tech can
do to minimize patient exposure), proper technical factors (highest
optimum kVp), use gonadal shields and lead aprons. Also, filtration,
intensifying screens, protective aprons and barriers and limiting the
number of exposures where possible (like on kids and pregnant ladies)