Diagnostic Principles

Question 1

what does radiography do?

Answer 1

help diagnose diseases and conditions

Question 2

how and when was radiography discovered?

Answer 2

by Physicist Wilhelm Conrad Rontgen in 1895 when he was experimenting with electron flow in vacuum tubes

Question 3

what is radiation?

Answer 3

• a form of electromagnetic energy
• consists of different types of waves
• made up of particles called photon or quanta

Question 4

what are the 5 types of radiation waves?

Answer 4

• radiowaves
• visible light
• x-rays
• infrared
• ultraviolet

Question 5

what is wavelength?

Answer 5

the distance between two consequtive corresponding points on a wave

Question 6

what is frequency?

Answer 6

the number of cycles of the wave that pass through a stationary point per second

Question 7

how are wavelength and frequency related?

Answer 7

• inversely
• short wl, high f
• long wl, low f

Question 8

how is wavelength measured?

Answer 8

in nanometers

Question 9

what are some properties of x-rays?

Answer 9

• penetrate living tissues and materials
• invisible
• cumulative
• travel at the same speed

Question 10

how are x-rays produced?

Answer 10

when electrons are slowed down or stopped by the atom of the target area inside the x-ray tube head as a result of the high speed collision of atom

Question 11

what is an atom?

Answer 11

made up of electrons, protons, and neutrons

Question 12

what is the melting point and atomic number of tungsten?

Answer 12

high melting point- 3422
atomic number is 74

Question 13

what is bremsstrahlung?

Answer 13

when an electron passes near the nucleus it is slowed and its path is deflected, energy lost is emitted as a bremsstrahlung x-ray photon

Question 14

what are the three main requirements for x-ray production?

Answer 14

• a source of electron production
• a target for the electrons to hit
• a method of moving the electron from the source of the target

Question 15

what is in the x-ray machine?

Answer 15

tube head, a stand, control panel, lead lined table

Question 16

what is a cathode?

Answer 16

• negative part of the x-ray tube
• made up of a coiled tungsten wire filament housed within a molybdenum focusing cup
• weak electric current

Question 17

what is the focusing cup?

Answer 17

• heated tungsten sits within focusing cup
• negatively charged so electrons are repelled into a group in the middle

Question 18

what is mAs?

Answer 18

• milliamperes
• affects the number of x-rays produced

Question 19

what is the anode?

Answer 19

• the target for the electrons
• made of tungsten
• positively charged
• where the x-ray beam originates

Question 20

what is kV?

Answer 20

• kilovolts
• strong electric current is applied between the anode and cathode which makes the anode+ and cathode-

Question 21

what are the two types of anode?

Answer 21

• stationary anode
• rotating anode

Question 22

what is a stationary anode?

Answer 22

• target area is small so lower mA and kV
• heat dispersed is limited
• found in portable x-ray machines

Question 23

what is a rotating anode?

Answer 23

• target spread over a rotating disc
• increased surface area
• angled at 20*
• rotates when exposure is made

Question 24

what is the focal spot - penumbra effect?

Answer 24

• penumbra effect
• penumbra is the lack of detail caused by the focal spot size
• smaller the focal spot, shaper the image
• larger focal spot, lack of detail, more shadow = penumbra

Question 25

how can you reduce penumbra in a radiographic image?

Answer 25

• use a small focal spot
• increase exposure time
• increase added filtration
• align the tube appropriately

Question 26

what is in the x-ray tube head?

Answer 26

• cathode and anode

Question 27

where are the cathode and anode mounted in an x-ray tube head?

Answer 27

In a vacuum inside a pyrex container

Question 28

why is the pyrex container in an x-ray tube head surrounded by oil?

Answer 28

helps with heat dissipation

Question 29

what electrical apparatus is involved in an x-ray circuit?

Answer 29

• step up transformer (turns mains volts into kilovolts)
• step down transformer (reduces mains current from amps to milliamps)
• an auto transformer
• a rectifier circuits

Question 30

what does kV control?

Answer 30

the quality of penetrating power of the x-ray beam

Question 31

what does kV affect?

Answer 31

• scale of contrast (grey)
• radiographic density (black)

Question 32

what does mAs determine?

Answer 32

the tube head current, quality of x-rays

Question 33

what is opacity?

Answer 33

the description of the radiographic appearance of an object - how many x-rays are allowed to pass through that object

Question 34

what are the 5 radiographic opacities?

Answer 34

• metal
• mineral
• fluid
• fat
• gases

Question 35

what are the 3 factors that appearance of an anatomic part on a radiograph is related to?

Answer 35

• density and atomic number
• thickness and shape
• surrounding objects