Module 2 Flashcards
Who discovered xrays
Wilhelm Rontgen
When were xrays discovered?
1896
Where were xrays discovered
The Glasgow Royal Infirmary
Who took the first Dental Xray
Otto
Walkhoff
Radiography Definition
Uses x-rays to produce images of areas inside
objects
Radiology
Uses images to diagnose and treat disease
What is Electromagnetic radiation is made up from
both electric and magnetic fields
What is a Photon
Waves are energy and momentum from one
point to another known as wave packet
What is a photon is equivalent to
one quantum of
energy
What mass does a photon have
None
What happens to a photon is a frequency is doubled?
The photon is doubled
How is energy of photons measured
In electron volts
What is Frequency
Number of repetitions in a given time period
With frequency what happens with more repetitions
More repetitions = higher frequency = shorter
wave length
What is the estimated individual does from background radiation
2.7mSv per year
ALARP
As Low As Reasonable Practicable
List Xray Equipment in Dental Surgery
• Tube head • Positioning arm • Control panel – Wall mounted – Part of chair – On wheels – Hand held
What is the outer casing of the tubehead
Lead - must be
checked regularly to ensure no cracks or damage
What is the xray tube in and what is it filled with?
A glass envelope which is filled with oil to remove the heat
Step up transformer voltage?
Increases 240V to 60 - 90kv
Step down transformer voltage?
Decreases the 240v to
7-10v required to heat the filament
Aluminum filtration
Removes harmful low energy
x-rays (soft x-rays less than 30kV)
What is a cathode?
A tungsten filament centered in a
focusing cup
How are Electrons are produced?
By the filament and are focused at the
target on the anode (the x-rays
are produced at the anode)
In the Cathode the focusing cup has what charge and why?
The focusing cup has a negative charge – the same as the electrons – this helps direct the electrons to the target
What does the focusing cup do?
Aims the stream of electrons to the focal spot on the target
What happens when the exposure button is pressed?
the electricity flows from
the filament in the cathode – the
filament gets hot
What do electrons do?
Electrons are released which surround the filament
What happens when the filament gets hotter
The hotter the filament gets the
greater number of electrons are
released
What is Anode comprised of?
Comprised of a tungsten target on a copper
base.
What happens when electrons from filament hit the target?
When the electrons from the filament hit the target they generate the x-rays and heat. The copper base removes the heat so as it doesn’t get too hot
High Voltage (kilovoltage, kV)
Connected between the anode and the cathode to accelerate the electrons from the negative filament to the positive target
Kvp or Kilovoltage peak
A Current (milliamperage, mA)
Flows from the cathode to the anode –
Measurement of the quantity of electrons
being accelerated
Spacer Cone or Beam Indicating
Device (BID)
Direction the beam and sets the ideal distance
from the focal spot on the target to the skin
(FSD)
What is the collimator
A metal disc with hole in the middle found by the
window in the lead casing. It limits and shapes
the beam and shapes to the same size as an
intra oral film.
maximum size of the collimator
40 x 50 mm
Aluminum Filtration
moves non diagnostic low energy (soft) xrays which are easily absorbed by the patient and therefore is more damaging
Where is Aluminum Filtration
Found between the collimator and the spacer
cone
List components of Control Panel
- Mains switch
- Timer
- Exposure time selector
- Film speed selector
- Patient size selector
- Mains voltage compensator
- Kilovoltage selector
- Milliamperage switch
- Exposure adjustment for digital imaging
What is Alternating Current
240V current is an alternating current- half is
negative and half is positive.
What is the positive half of alternating current
The positive half only is needed for the production
of x-rays
kV
Size of the tube voltage
mA
Size of the tube current
d
Distance from the target
(t)
Time = length of exposure
How do xrays travel and what is the law?
X-rays travel in straight lines and they obey
the inverse square law – Intensity = I/d² -
they decrease as you get further away from
the beam
What are xrays referred to as?
X-rays are referred to as ionising radiation
How can Xrays affect film emulsion?
X-rays can affect film emulsion to produce a
visual image and can cause certain salts to
fluoresce
