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Dental Radiography Module 1 > Dental Radiography > Flashcards

Dental Radiography Flashcards

1
Q

What is the definition of Radiography?

A

Uses x-rays to produce images.

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2
Q

What is the definition of Radiology?

A

The use of images to diagnose and treat disease..

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3
Q

What does EMR waves stand for?

A

Electromagnetic Radiation.

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4
Q

what is the definition of EMR?

A
  • Use energy and momentum
  • Electric and magnetic
  • Travel at 90 degrees to each other
  • Wave packets (Photon/Quantum
  • No mass
  • Measured in electron Volts (eV)
  • Can travel through a vacuum
  • Vibrates transferring energy from one place to another without matter being transferred
  • some waves require a medium to travel through eg sound waves
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5
Q

What is a photon?

A

A wave/ energy packet and can be both wave and particle and should the frequency be doubled then the energy of the photon is doubled.

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6
Q

what is frequency?

A
  • number of repetitions in a given time period
  • Greek symbol is Nu or V
  • more repetitions the higher the frequency but a shorter wave length
  • measured in hertz HZ
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7
Q

The shorter a wave length…….?

A

the more dangerous they are

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8
Q

Cancer can be caused by……?

A

Any waves shorter than visible light eg Gamma rays are the shortest then xrays!

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9
Q

What is Ionising radiation?

A
  • It carries more energy than non- ionising radiation
  • can create charged ions by displacing electrons in atoms
  • radiation from radioactive sources and naturally occurring radiation.
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10
Q

What is Ionising radiation used for?

A

used in medicine - Diagnostically, caries in teeth

-Therapeutic, treatment in cancer

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11
Q

What is Non-Ionising Radiation?

A

Changed position of atoms but does not change or alter the make up, structure or properties

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12
Q

Are dental xrays safe?

A

the risk of biological damage is small but there is still a risk

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13
Q

In the UK how many xrays are taken in a year?

A

approximately 20-25 million intra and extra oral a year

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14
Q

In the UK how many fatalities per year?

A

Approximately 10 fatalities per year

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15
Q

All exposures must be kept…..?

A

ALARP as low as reasonably practical

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16
Q

Name X-ray equipment…?

A
  • Tube head
  • positioning arm
  • control panel
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17
Q

All x-ray equipment must be….?

A
  • safe and robust
  • accurate and simple to operate
  • must produce suitable x-rays, both film and digitak
  • small
  • easy to position, move and store
  • stable and balances when positioned
  • outer casing made of lead and checked daily for damages
  • x-ray tube in glass envelope which is filled with oil to remove heat
  • step up transformer which increases the voltage from 240V to 60-90 kV
  • step down transformer which decreases 240V to 7-10V required to heat the filament
  • Spacer cone/beam indicating device
  • Collimator
  • Aluminium filtration removes harmful low energy x-rays (Soft xrays less than 30KeV)
  • Focal spot
18
Q

What happens at the glass envelope inside the xray tube?

A

located at the back of the tube head, completed surrounded by lead which absorbs unwanted x-rays which are travelling in all directions which creates a vacuum.

19
Q

What is a cathode?

A

-made up of a tungsten filament which is centred in a focusing cup
-electrons are produced by the filament and focused onto the target on the anode
-Focussing cup has a negative charge ( same as electrons) and helps direct to target
-

20
Q

What is Thermionic Emission?

A
  • when the exposure button is pressed the electricity flows from the filament in the cathode and the filament gets hot
  • the hot filament then releases electrons which surround the filament
  • the hotter the filament gets the greater number of electrons released
21
Q

What is the anode?

A
  • comprised of a tungsten target on copper base
  • when the electrons from the filament hit the target and generate the xrays, heat is produced
  • the copper target helps take the heat away as it could get to hot
22
Q

What is the focussing cup?

A

Aims the stream of electrons to the focal spot on the target

23
Q

What is the focal point to skin distance?

A
  • Not less than 200mm for kV under 60kV

- Not less than 100mm for kV over 60kV

24
Q

Older pointed xray machines must not be used why?

A

They produce scatter on x-rays

25
Q

Blurring of image is called…?

A

the penumbra effect

26
Q

The collimator should be….?

A

-rectangular with a maximum diameter of 40mm X 50mm, this will ensure that the maximum overlap when using an intraoral film size 2 is 2mm

27
Q

what is Filtration….?

A

-reduces skin dose
-removes non diagnostic/low energy xrays/soft radiation (which is more readily absorbed by patient hence why so damaging
-thickness must be 1.5mm below 70kV
and
2.5mm above 70kV

28
Q

Control Panel must include….?

A

-mains on/off switch with warning light
-Timer electronic impulse or clockwork
Exposure time selector, numerical/ anatomical (picture of teeth)
-exposure warning light with audible signal
May also include
- film speed selector
-patient size selector
-mains voltage compensator
-kilovoltage selector
- Miliamperage switch
-exposure adjustment for digital imaging

29
Q

What is the alternating current in relation to radiography?

A
  • Measured in Voltage (V)
  • half is negative, half is positive current
  • only positive is needed for production of xrays
  • A step up of voltage is needed to eliminate negative
  • equipment is working at peak output at top of cycle measured in kVpeak or kvP
30
Q

Direct Current is used by modern xray machines

A
  • keeps the kV at kVpeak throughout all exposure
  • xray production per unit time is more efficient
  • more high diagnostically useful photons are produced per exposure
  • few lower energy photons are produced
  • shorter exposure time
31
Q

what factors affect the intensity of the beam?

A
  • size of the tube voltage kV
  • size of tube current mA
  • distance from target d
  • time = length of exposure
  • filtration
  • target material
  • tube v waveform
32
Q

in free space xrays travel in straight lines and obey then inverse square law which means?

A

-Intensity=I/d2 which means it decreses the further away it gets from the beam

33
Q

shorter wave lengths=

A

greater energy and can therefore penetrate a greater distance

34
Q

longer wave lengths=

A

low energy and have little penetrating power. (soft energy)

35
Q

Xrays are referred to as….?

A

Ionising radiation

36
Q

xrays can affect film emulsion….?

A

to produce a visual image and can cause certain salts of flourescence

37
Q

In a year approximately how many dental xrays are taken per year?

A

20-25 million

38
Q

How many fatal malignancies a year?

A

10

39
Q

What is a step up transformer?

A

Step up transformer – increase the voltage from 240V to 60-90kv

40
Q

What is a step down transformer?

A

Step down transformer – decreases the 240v to 7-10v required

41
Q

Aluminium Filtration reduces skin dose….

A
  1. 5mm below 70kV

2. 5mm above 70 kV

Dental Radiography Module 1 (10 decks)

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