radiography Flashcards
- List FOUR benefits that digital radiography has over film radiography.
(4 marks)
no need for chemical processing
easy storage and archiving
easy back up of images
images can be integrated into a record
images can be manipulated
- When taking periapical or bitewing radiographs, rectangular collimation is used to shape the X-ray beam so that it matches the shape of the radiographic receptor in the mouth. Explain what the benefit of this is. (2 marks)
reduced radiation exposure
improved image quality = ensures that entire rector ares is exposed uniformly = better clarity and sharpness
- Rectangular collimators contain the metal lead.
What chemical property of lead makes it particularly effective at absorbing X-ray photons?
(1 mark)
high atomic number makes it particularly effective at absorbing x-ray photons
huge proportion of electric effect
- During a radiographic exposure the dentist must not stand too close to the patient or X-ray source. What is the minimum distance recommended by UK guidance? (1 mark)
1.5 m minimum, 2 is ideal
- All medical radiation exposures must be justified. What does the term “justification” mean in the context of deciding whether or not to take a dental radiograph? (1 mark)
weighting the potential benefits against the associated risks while considering all the factors such as diagnostic value, availability of methods and potential radiation exposure
- ALARP is an important phrase in radiation protection. What does this abbreviation stand for? (1 mark)
as low as reasonably practicable
- Which external reference plane of the patient should you position horizontally when setting up for a panoramic radiograph? (1 mark)
frankfort horizontal or occlusal plane
- When you look at the radiograph you have taken, some of the teeth are horizontally distorted. Which positioning error results in the following:
i) The incisor teeth being horizontally magnified (1 mark)
too far forward = excessive anterior position
ii) The posterior teeth on one side being wider than on the other (1 mark)
lateral position error
- The patient is unable to remove their earrings with the result that there are ghost images of the earrings. Give THREE important features that apply to all ghost images. (3 marks)
appear magnified
blurry and fainter = reduced opacity or transparency
higher (due to beam incline)
reversed or mirrored
on the opposite side of true anatomical position
- What panoramic radiograph would you ask to be taken in the following clinical situations:
i) A pre-extraction radiograph for partially erupted 48, when there is no evidence of 38 in the mouth; 48 is to be extracted under local analgesia
(1 mark)
OPT RHS
ii) For a child patient with caries, who cannot tolerate bitewings
(1 mark)
OPT - panoramic
- The maxillary sinus is depicted in a panoramic radiograph. Which margins or walls are seen in the following locations:
i) Horizontally above the roots of the premolars and molars. (1 mark)
ii) Vertically above the third molar region. (1 mark)
i) the inferior border or floor of the maxillary sinus.
ii) zygomatic buttress
- The above xray is 5 years old and the patient represents to the clinic with symptoms of pericoronitis from the partially erupted 48. The patient informs you that 38 was extracted some years ago.
What panoramic programme would be most suitable?
(1 mark)
targeted/limited radiograph of RHS
- Which external reference plane of the patient should you position horizontally when setting up for a panoramic radiograph? (1 mark)
Frankfort occlusal plane
- If the plane referred to in Q3 above is not positioned horizontally, what will be the effect on the occlusal plane in the image?
(1 mark)
tilted or slanted
- The maxillary sinus is depicted in a panoramic radiograph.
Which margins or walls are seen in the following locations:
i. Horizontally above the roots of the premolars and molars.
(1 mark)
AND
ii. Vertically above the third molar region.
(1 mark)
i) inferior margin/ floor
ii) superior margin/roof
c. Give 3 ways the dose to the patient is reduced by normal radiographical techniques.
adjust exposure settings
use of collimation
lead aprons and thyroid collars
d. Describe the process of Compton scatter and how it differs from the photoelectric effect
compton = incoming x-ray photons interact with outer-shell electrons in atom and eject electron from the orbit and create new lower energy x-ray photon
it then loses energy and changes direction
both the incident X-ray photon and the ejected electron conserve momentum but not necessarily energy.
scattered x-ray photon has lower energy and changes direction
photoelectric effect =
incoming X-ray photon is absorbed by an inner-shell electron in an atom, causing the electron to be ejected from the atom.
ejected electron is called a photoelectron and the atom is left in an ionised state
the entire energy of the incident X-ray photon is absorbed by the electron, resulting in the complete removal of the electron from the atom. there is no scattered photon produced in this interaction.
e. What metal is used to absorb the heat generated during X-ray production?
tungsten
f. Name another metal used in X-ray production.
molybdenum
Explain the production and properties of X-rays in dental radiography.
high-speed electrons strike a metal target (anode) within the X-ray tube
it is known as remsstrahlung radiation, results in the generation of X-rays with a broad spectrum of energies.
they penetrate tissues based on their density
they interact by absorption, scattering or transmission, producing an image on the radiographic film
Define a “ghost image” in the context of dental radiography.
ghost image refers to artefacts caused by a dense object outside the primary x-ray beam
it appears as a faint image opposite the actual objects position on the radiograph
what is the purpose of the coin test in dental radiography?
performed to assess the proper functioning of the X-ray tube in dental radiography.
by placing a metal coin (e.g., a penny) on the patient’s skin surface during X-ray exposure, any artifacts caused by malfunctioning or improper alignment of the X-ray tube can be identified on the resulting radiograph.
