VET 260 - Exam 1

What is an x-ray?

a form of electromagnetic radiation

what is electromagnetic radiation?

method of transporting energy

What are examples of x-ray properties?

• invisible

• electrically neutral

• have no mass

• travel at speed of light

What kind of damage can x-rays cause to living tissue?

chemical or biological damage

What is an element?

smallest particle of a substance

What is the smallest particle of an element?

atom

atoms contain what? (3)

protons (+), neutrons, and electrons (-)

as the number of protons increase the number of e- _______?

increase

What conversion is used to create x-rays?

conversion of matter into energy

principle characteristic of matter is?

mass or weight

principle characteristic of energy is?

movement

what are the 2 types of energy used in x-ray production?

electrical and electromagnetic

what type of energy travels in waves?

radiant

x-rays are measured by what?

wavelength

what is the name, given to the height of the x-ray wave?

amplitute

what are photons?

bundles of pure energy

as energy increases frequency _______

increases

electromagnetic radiation is a method of transporting _______ through space

energy

x-rays vary in? (2)

wavelength and frequency

what is frequency?

number of waves passing a given point in a certain amount of time

Shorter wavelengths have _______ frequencies that penetrate the tissue _______ effectively.

higher, more

Long wavelengths have ______ frequencies that penetrate the tissue _______ effectively

lower, less

what is the speed of light in m/s?

186,000 m/sec

absorption depends on what 2 factors?

density and energy

darker areas in x-rays indicate what?

x-ray went through patient and reached film

lighter areas on x-rays indicate what?

x-rays were absorbed by patient and did not reach film

Bones will appear dark or light on an x-ray?

light (white)

fat will appear dark or light on an x-ray?

darker

what is the term given when e- are boiled off?

thermionic emission

what is an image of an x-ray called?

radiograph

the x-ray unit is a closed or open circuit?

closed circuit

what are the 3 x-ray generator settings?

voltage (kVp), current (mA), and time

what is needed to produce x-rays?

source of e-

how are x-rays produced?

by directing high speed e- to a metal target (anode)

Describe how an x-ray is created and the path it takes to reach the patient

filaments in focusing cup (cathode) warm up and send high speed e- to target on anode that are converted into x-rays and redirected to the patient

energy is released in what 2 forms? (%)

heat (99%) and x-rays (1%)

what does the voltage control?

penetrability of the x-ray beam

what does the current control?

number of photons and density of the image

what does time control?

time over which exposure exists

what houses the cathode and anode?

special heat resistant glass enclosure

what prevents the radiation from exiting the x-ray tube?

metal housing

what is a component of the x-ray tube that provides an obstacle-free path for the e-?

vacuum

power enters through the anode or the cathode?

cathode

heat will exit through the cathode or the anode?

copper stem of the anode

how can the filament affect the number of e- produced?

the hotter the filament → more e- produced

the higher the voltage the _______ speed of e-, resulting in x-rays of ______ wavelengths and ______ penetrating power and intensity

higher, shorter, greater

where on the anode are x-rays produced?

focal spot of target

the cathode’s large filament is used when?

large body parts are examined

small filament of cathode is used when?

extremeties and small pocket animals

what setting controls which filament is to be used?

milliamperage setting (mA)

what are the 2 kinds of anode?

rotating and stationary anode

what is the benefit of the rotating anode and what is it used for?

dissipates heat as it rotates, used in small animals installed x-ray units

what is the stationary anode used for?

large animal mobile units or dental x-ray machine

which anode is mounted on ball bearings?

rotating anode

what is the range of angle the anode is beveled in?

11 to 15 degrees

what is the anode heel effect

intensity of radiation is greater on CATHODE side

the thickest portion of the animal should be placed on what side? and why?

cathode side, to take advantage of the anode heel effect

what is the line focus principle?

how e- interact with anode and change direction so x-rays are directed to patient

Large focal spots cause what?

penumbra

large focal spot do what concerning heat?

dissipate heat better

what causes a heat bloom?

repeated exposure causes dissipation of heat surrounding the focal spot → enlarged focal spot

what are examples of heat dissipation techniques?

tungsten, copper, oil of ball bearings, rotating anode

potential difference refers to what?

difference between the charge of cathode vs anode

what charge does the cathode have?

negative → houses e-

what is space charge?

when a cloud of e- are produced

off-focus radiation is caused by?

kVp setting too high

kVp controls what? (4)

voltage, penetrating power, quality and contrast

mA controls what? (3)

current, quantity of e- and density

what cells are affected in radiology?

all living cells

which cells are most sensitive to radiation?

rapidly dividing cells (growth cells, gonadal cells, dermis, epithelial cells)

what are the 2 main types of radiation effects?

stochastic (somatic) - occur by chance, late term effect

non-stochastic (deterministic) - short term

What is linear energy transfer?

describes the amount of energy imparted to target

radiation doses are measured with what device?

dosimeter

dosimeters measure exposure to what? (3)

beta, gamma and x-radiation

dosimeters are made to measure what kind of radiation?

scatter or secondary radiation

what are 2 kinds of dosimeters?

thermoluminescent dosimeters → measures intensity of light emitted from crystal when heated

optically stimulated luminescence → absorbs radiation and store energy in form of excited e-

what is the occupational health and safety act?

indicates it is the employer's responsibility to ensure that the healthcare worker is protected against any excessive radiation exposure

what is MPD?

maximum amount of radiation a person can be exposed to in a given period

what is the MPD for VTers?

0.05 S/annually or 0.01 S X age (entire life span)