X-Ray Production

Question 1

What are the principles of x-ray production?

Answer 1

-produced when electricity from the mains transformer into a high voltage current, with some of that energy converting to x-rays
-image is produced by computer manipulation of the data

Question 2

What are the principles of photons?

Answer 2

-travel in straight lines, in the primary beam
-can be absorbed or scattered
-can pass through x-rat and reach x-ray film or by a digital recording system

Question 3

Describe the energy involved in x-rays?

Answer 3

-it’s directly proportional to the frequency
-it’s indirectly proportional to the wavelength

Question 4

What is the frequency involved in x-rays?

Answer 4

-the number of waves that pass a certain point in a specified amount of time

Question 5

What is the wavelength involved in x-rays?

Answer 5

-is the distance between any 2 corresponding points on adjacent waves

Question 6

Why does penetration occur?

Answer 6

-due to high energy

Question 7

What are the effects of using photographic film?

Answer 7

-produces latent or hidden images
-revealed by processing

Question 8

Why is fluorescence used?

Answer 8

-x-rays cause crystals of certain substances to fluoresce
-utilised with digital radiography

Question 9

What are the properties of atoms?

Answer 9

-contain protons which are positively charged in the nucleus

-contain neutrons which have no charge

-contain electrons which are negatively charged and orbit around the nucleus

Question 10

How are x-ray photons produced?

Answer 10

-when rapidly moving electrons are slowed down or stopped

Question 11

What happens when x-ray photons travel at high speeds?

Answer 11

-they collide with other atoms and lose their kinetic energy

Question 12

What happens to the energy produced by x-ray photons?

Answer 12

-transformed into heat and a very small amount into x-ray energy

Question 13

What does the tube head contain?

Answer 13

-cathodes which are negatively charged

-anodes which are positively charged

Question 14

Where are electrons produced?

Answer 14

-at the filament which is a coiled wire made up of tungsten

Question 15

How are electrons produced?

Answer 15

-a small electrical current is applied to the coiled wire filament which is heated and releases a cloud of electrons

-called thermionic emission

Question 16

Why is the focusing cup placed around the filament essential?

Answer 16

-to ensure electrons will reach the target in a narrow beam

Question 17

What is the focusing cup made of and what are its characteristics?

Answer 17

-made of molybdenum

-has a high melting point and is a poor heat conductor
-negatively charged and part of cathode

Question 18

What does the focusing cup do?

Answer 18

-repels electrons causing them to form a narrow beam due to their concave shape

Question 19

What happens to the cloud of electrons produced?

Answer 19

-they are accelerated at high speeds across the tube head to the target (anode)

Question 20

Describe the high electrical potential difference between the filament and the target?

Answer 20

-the negatively charged filament reports the exceptions at the cathode side

-the target becomes positive and attracts electrons to the anode side

Question 21

What are the characteristics of the tungsten?

Answer 21

-high atomic number
-high melting point
-mechanical properties

Question 22

What are the characteristics of the copper block

Answer 22

-good heat conducter
-leads heat away form the target to the cooling fins and surrounding oil

Question 23

What are the characteristics of the target?

Answer 23

-set at an angle of 20 degrees
-allows the area being struck by electrons to be as large as possible

Question 24

What does angulation mean?

Answer 24

-the x-ray beam appears to originate from a much smaller area

Question 25

Why is angulation important?

Answer 25

-keeping the smallest area as possible allows very fine radiographic definition -larger are will reduce radiographic definition substantially leading to a less sharp image

Question 26

What is the glass envelope?

Answer 26

-a glass vacuum tube that contains the anode and cathode of the x-ray tube

Question 27

What is the vacuum and its function?

Answer 27

-a space with all air/gases extracted -allows the x-rays to travel in straight lines, if oxygen were present the x-rays would bounce off the particles and be misdirected

Question 28

What are soft x-rays?

Answer 28

-they do not have enough power to pass through the patient -can lead to scatter or absorption

Question 29

What is the structure and function of the aluminium filter?

Answer 29

-a flat sheet of aluminium -placed over the window -absorbs soft x-rays and prevents them from leaving the tube head

Question 30

How are images formed?

Answer 30

-image is produced when an exposure takes place -image appears black, white and various shades of grey

Question 31

What does x-ray absorption depend on?

Answer 31

-in relation to the tissues their; Atomic number Specific gravity Thickness

Question 32

What is the atomic number in relation to x-rays?

Answer 32

-bone has a higher atomic number than tissues -absorbs more x-ray photons -produces paler areas of radiographs

Question 33

What is specific gravity in relation to x-rays?

Answer 33

-bone has a high specific gravity -soft tissue has a medium specific gravity -gas has a low specific gravity

Question 34

What are the colours of each component seen on images?

Answer 34

Gas is very dark Fat is dark grey Soft tissue or fluid is mild grey Bone is nearly white Metal is white

Question 35

When causes a white appearance on images?

Answer 35

Thicker areas which have absorbed more x-ray photons

Question 36

What causes a grey appearance on images?

Answer 36

Thinner areas which have absorbed less x-ray photons

Question 37

What is the function of kilovoltage?

Answer 37

Determines the speed and energy of which electrons hit the target (penetrating power)

Question 38

What is the function of milliamperage?

Answer 38

Measures the quantity of electrons crossing the tube during an exposure Controls the heating of the filament

Question 39

What is the function of the timer during exposure?

Answer 39

Controls the amount of time that a high voltage is applied for

Question 40

What is the focal-film distance?

Answer 40

The distance between the focal spot and the x-rat film/cassette

Question 41

How would we set kV for patients?

Answer 41

-increased kV for large dog -decreased kV for small or thin dog

Question 42

What impact does incorrect kV setting have?

Answer 42

too low means it’s underexposed too high means it overexposed

Question 43

What does the milliamperage control?

Answer 43

-controls the electrical current to the cathode and thereby the temp of the tube filament -controls the amount of x-rays produced

Question 44

What impact does incorrect milliamperage setting have?

Answer 44

Too low means radiograph will be pale Too high means radiograph will be dark

Question 45

What variables affect the radiography image?

Answer 45

X-ray Be including kV mAs collimation and distance Patient including movement positioning and preparation of the area

Question 46

What are girds?

Answer 46

A flat plate that is placed between the patient and the cassette Can be placed underneath x-ray table or built into it Can be built into the cassette

Question 47

What is the structure of grids?

Answer 47

-alternating strips -materials is able to absorb radiation radiologist interspace -aluminium or carbon plastic fibres scatter will be absorbed by the lead strips