What is an X-ray image? Flashcards
What is image geometry?
The aim is to achieve that are as geometrically accurate as possible without any distortion.
How can we avoid a distorted image?
The object we are imaging should be as close and parallel to the detector as possible.
If the object is not parallel to the film the image is foreshortened.
If the film is not parallel to the object the image is elongated.
if the x-ray beam is not perpendicular to the object then the image is distorted.
what else can affect the magnification and distortion?
how close the x-ray beam is to the detector. the closer the x-ray beam is to the detector the more distorted the image is.
the x-ray beam is divergent, the further x-ray beam the more divergent it will be minimising distortion.
so what is the ideal position for a geometric image?
the focal point/x-ray beam far from the detector and the object is parallel and close to the detector.
what are the types of imaging we can take?
intra-oral
extra-oral
3D imaging
Give examples of intra-oral radiographs.
periapical
bitewing
occlusal
Give examples of extra-oral radiographs.
planar projections (PA mandible, lateral cephalogram)
panoramic projections (dental panoramic tomograph)
Give examples of 3D radiographs.
cone beam CT
how do you take an intra-oral radiograph?
uses digital imaging
small detectors are placed in a film holder, film holder ensures the detector is a parallel as possible.
this is placed in the mouth.
what is the difference between a periapical and bitewing radiograph?
periapical - full anatomy of the tooth and can be a single part of the jaw (3-4 teeth)
bitewing - a bit of the detector is imaging the top teeth and a bit of the detector is imaging the bottom teeth and it’s only the crowns.
what is the difference between planar projections and panoramic projections?
planar projections - gives a mandible image.
The detector is touching the patient’s face and the x-rays are coming from behind the patient to create a posterior and anterior image of the patient jaw.
panoramic projections - unit will rotate around the patient’s head by 180 degrees, taking x-rays at different angles around the patient. With each degree of rotation, as the x-rays are produced only exposing a narrow slit of the detector, slowly exposing the detector to form the image.
why is a bitewing radiograph more geometrically accurate than panoramic radiography?
because the technique creates geometric distortion.
how does cone bean CT scan work?
3D images is created, as it uses many X-rays from many different angles around the circumference of the patient.
uses high dose as it uses more x-rays.
