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VET 331 > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

What is the difference between radiography and radiology?

A
  • Radiography = the use of X-rays to create a formed image - Radiology = the interpretation of normal and abnormal findings
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2
Q

What are the basic steps that are involved in the process of radiography? (7 steps)

A
  1. X-ray production 2. Beam attenuation to the patient 3. Image formation (receptors, film screen and digital) 4. Image processing (analogue and digital) 5. Quality assessment and controls 6. Radiation safety 7. Image geometry and patient factors
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3
Q

_________ is the energy that is needed to eject an electron from its shell. It ______ as we go further to the base level of electrons.

A
  1. Binding energy 2. Increases
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4
Q

What does an atom become when it looses electrons ___. How does the net charge becomes more ________.

A
  1. ion 2. positive
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5
Q

What is the formula for velocity of an electromagnetic wave?

A

Velocity = frequency times wavelength

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6
Q

As wavelength decrease. Total energy _____

A
  1. increases
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7
Q

What are the units that are used to measure wavelength, energy and frequency?

A
  1. wavelength unit = meters/nanometers/angstroms 2. Energy unit = eV (electron volts) 3. Frequency = hertz (Hz)
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8
Q

What are the properties of X-rays?

A
  1. Electromagnetic waves – refraction, reflection, propagation & scatter radiation 2. Discrete Energy Bundles – Photoelectric effect (PE), absorption, fluorescence 3. Travel in straight lines 4. Produce small amount of heat passing through the tissue 5. Cannot be focused by a lens – we can only focus the electrons not the beam itself 6. Not affected by electric or magnetic fields 7. Penetrating- high energy, form image meaning potential for safety issues 8. Produce fluorescence 9. Affect film and imaging plates to form an image 10. Ionising- elimination of electrons from energy cells are responsible for the biological effects 11. Biological effects means cell destruction, carcinogenesis and genetic effects
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9
Q

Name A, Z and X

A

A = mass number

Z = atomic number

X = chemical element/symbol

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10
Q

What are the components that are found on the control panel of an X-ray machine?

A
  1. Kilovoltage (kV or KVp- meaning maximum kilovolts)
  2. mA control (millamperage) sometime the seconds control is combined in with this
  3. Time control (either by itself or combined with mA)
  4. Line Voltage control (actual voltage in real time)
  5. Exposure button
  6. Pre-exposure button
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11
Q

i) What are the components of a cathode tube?
ii) Is it postive or negative electrode?
iii) High voltage or a low voltage circuit?

A

i) Coiled filament wire, a focusing cup and small and large focal wires
ii) negative electrode
iii) Low voltage circuit

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12
Q

i) What are the components of an anode?
ii) Is it high/low voltage circuit?
iii) Is it a postive or a negative electrode?

A

i) Target and a focal spot
ii) High voltage circuit
iii) postive electrode

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13
Q

What setting controls the size of the electron cloud?

A

mA setting controls the size of the electron cloud

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14
Q

What is a problem with continually pressing the pre-exposure button?

A

Results in cathode damage

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15
Q

What does the exposure button do?

A

Creates a potential difference across the tube

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16
Q

What is the result on the kinetic energy of increasing the kV controls?

A

Increases kinetic energy on collision

17
Q

What is the charge of the focusing cup around the cathode and what is it’s function?

A

The charge of the focusing cup is negative and the function of it is to focus the electron stream

18
Q

What percentage of energy of anode collisons result in radiation being produced?

A

Only about 1% of collision will result in radiation being produced

19
Q

What are the two different types of radiation that make up the primary X-ray beam, what is the relative percentage of them and what causes them?

A
  1. Bremsstralung radiation (BR) -75 to 90% - collisons with nucleus
  2. Characteristic radiation (CR)- 10 to 25%- inner shell electrons
20
Q

What two factors influence the energy of the Bremsstrahlung radiation and when does the maximum ray beam occur?

A

Energy of BR formed: initial energy of incomming e- and angle of deviation at nucleus. The maximum energy loss occurs with a nucleus collision.

21
Q

What is the effect of changing mAs on the beam?

A
  1. Increases the mAs (increasing size of e- beam and time crossing tube)
  2. Increases collisions at target
  3. Increase number of BR formed
  4. Increasing intensity of the beam (number of BR per area)
22
Q

What is the effect of changing the mAs of the beam on the radiograph?

A

Increases the radiographic density only it has no effect on the energy. It will only increase the film blakcness if the energy of the bremstrunng radiation is high enough energy.

23
Q

What is the effect of increasing the kV value of the primary beam?

A
  • High kV means higher kinetic energy of electron at target
  • Increased BR Max E
  • Increased BR Average E
  • Increased number of BR
24
Q

What is the effect of increasing the kV on the radiograph?

A

Increased energy of the beam: means increased penetration, decreased contrast and increased radiographic density

Increased intensity of the beam: increased radiographic density of the beam

25
Q

What is the caused of the peaks on a primary beam BR spectrum and what causes them?

A

Caused by characteristic radiation and they are equal to the difference in binding energy between shells of electrons

26
Q

What is meant by the heel effect and how can it be used to your advantage?

A

The result of uneven beam density means that the beam has a higher intensity on the cathode side. It can be utilised with thicker body parts

27
Q

What factors influence the maximum exposure times for X-rays?

A
  1. The focal spot size
  2. The heat capacity of the target
  3. Circuits and power supply
28
Q

What is the difference between effective focal spot and the actual focal spot size?

A
  • The actual focal spot is the size of the focal spot whereas the effective focal spot is actual sized viewed from the window
29
Q

Describe one benefit of a large focal spot and one benefit of a smaller focal spot:

A
  • Large focal spot allows for greater heat dissipation and greater overall exposures
  • Smaller focal spots allow increased detail and edge sharpeness
30
Q

What is the benefit of a rotating anode?

A

Rotates during exposures allowing heat to be spread over a much wider area.

31
Q

What is the problem with the use of combined circuits?

A
  1. Combined circuits means lower mA values
  2. kV and mA are no longer independant
  3. Only way to increase it is to increase the time
32
Q
A

VET 331 (36 decks)

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