Diagnostic Imaging AI Flashcards
Why are higher exposure factors needed when using a grid?
Higher exposure factors (higher mAs) are needed when using a grid to increase the quantity of primary X-ray photons.
What is the purpose of the lead shutters in the X-ray collimator?
The lead shutters in the X-ray collimator are used to adapt the size of the radiographic field to the body area being radiographed.
Why are intensifying screens used in conventional (screen-film) radiography?
Intensifying screens are used in conventional radiography to amplify the effect of X-rays, as the radiographic film is poorly sensitive to X-rays.
Where are the intensifying screens integrated in screen-film radiography?
The intensifying screens are integrated into both sides of the light-proof X-ray cassette, with the radiographic film placed in between.
What are the two important properties of intensifying screens?
The two important properties of intensifying screens are speed (ability to produce light and amplify the effect of X-rays) and sharpness (spatial resolution).
When are fast screens preferred in radiography?
Fast screens are preferred for large body parts (abdomen) or when movement artifacts are an issue (thorax).
Why is it recommended to have both fast and slow screens/cassettes available?
It is recommended to have both fast and slow screens/cassettes available to optimize image detail and resolution for different body areas (e.g. long bones).
What are the five sequential steps in film processing?
The five sequential steps in film processing are developing, rinsing, fixing, rinsing, and drying.
What are the two main types of digital radiography systems?
The two main types of digital radiography systems are computed radiography (CR) and direct digital radiography (DDR).
How does computed radiography (CR) work?
Computed radiography (CR) uses imaging cassettes containing a ‘storage phosphor’ plate that stores the absorbed X-ray energy in crystals and is later read by a machine using a laser beam.
What is the key difference between computed radiography (CR) and direct digital radiography (DDR)?
The key difference is that CR systems require a plate reader to scan and erase the storage phosphor plate, while DDR systems capture the radiographic image directly without using a plate reader.
What are some advantages of digital radiography over conventional radiography?
Some advantages of digital radiography over conventional radiography include higher contrast resolution, image manipulation capabilities, fewer exposures needed, quicker process, and easier image storage and sharing.
In what format are digital images stored in digital radiography?
Digital images in digital radiography are stored as computer files in DICOM format.
What is the importance of centring and positioning in radiography?
Centring and positioning in radiography is important to ensure that the body part being radiographed is well positioned and that unwanted rotation is avoided. This helps in obtaining accurate and clear radiographic images.
Give an example of superimposition on a dorsoventral projection of the thorax.
On a dorsoventral projection of the thorax, the sternum should be superimposed with the thoracic spine.
What should be superimposed with each other on lateral projections of the thorax?
On lateral projections of the thorax, the costochondral junctions should be superimposed with each other.
What should be superimposed with each other on lateral projections of the lumbar spine or abdomen?
On lateral projections of the lumbar spine or abdomen, the transverse processes of the lumbar vertebrae should be superimposed with each other.
Why is it important to avoid unnecessary superimposition of the surrounding anatomy onto the radiographic image?
Avoiding unnecessary superimposition of the surrounding anatomy onto the radiographic image is important to obtain a clear and unobstructed view of the specific body part being examined.
What are artefacts in radiography?
Artefacts in radiography are abnormalities or distortions that can appear on a radiograph, which do not represent actual structures. They can affect the appearance of the image and may lead to diagnostic errors if not recognized as artefacts.
What are some examples of artefacts that can occur in digital radiography?
In digital radiography, some artefacts that can occur include grainy images due to under-exposure, loss of structure margins with over-exposure, radiolucent halo surrounding metal implants (Uberschwinger artefact), ghost images from incomplete erasure of the CR plate, and moire artefact (bands seen across the image) resulting from interference between the sampling frequency and grid lines.
What are the biologic effects of X-rays?
X-rays are a form of ionising radiation that can cause harm to living tissues. They can ionise atoms and interfere with the molecular chemistry of cells, resulting in cellular damage. The specific effects depend on the tissue irradiated, characteristics of the radiation, dose received, and duration of exposure.
What is the basic structure of the X-ray tube?
The X-ray tube is composed of the cathode (source of electrons) and the anode (tungsten target), housed in a vacuum glass envelope surrounded by oil and lead housing.
What is the function of the cathode in the X-ray tube?
The cathode is a wire filament made of tungsten and it heats up to form a cloud of free electrons when a small electrical current is passed through it.
What is the function of the anode in the X-ray tube?
The anode is a tungsten target that releases X-rays when collided with accelerated electrons.