Clinical imaging Flashcards
What does MRI stand for?
Magnetic Resonance Imaging
What does CT stand for?
Computed Tomography
What does PET stand for?
Positron Emission Tomography
Who discovered X-rays?
Wilhelm Roentgen
What are the 2 main types of substance used in contrast studies?
Barium and Iodine
What are the strengths of X-rays?
They can show things that destroy white bone (e.g. bone cancer) and are good at showing things surrounded by white bone (e.g. fractures). They are also good at showing things surrounded by black air (e.g. lung cancer)
What are the weaknesses of X-ray?
To be visible on an x-ray, an abnormality must be of a different density to its surrounding tissue, which most things are not.
How are contrasts used to form clearer images on X-rays?
They contain dense elements that can block x-rays
Why are X-rays dangerous?
They use radiation, so can damage cell DNA leading to mutations. This may cause the cell to become cancerous.
Which regulations require the benefit of X-ray to outweigh the risks?
IRMER 2000 (Ionising Radiation Medical Exposure Regulations)
Why are radiographs not sufficient at diagnosing illness?
They take images from only one direction producing an image where all structures between the source and the film are superimposed
How is CT different to X-ray radiographs?
With CT, x-rays are fired from all around the body which produces a cross sectional image with no superimposition
What are the risks of CT scanning?
They give a very large dose of radiation, around the same amount as 250 chest x-rays
What are the weaknesses of CT scanning?
Soft tissue of similar density cannot be distinguishes, such as that in pelvic organs, muscles, tendons and joint cartilage
What are the positives of ultrasound?
Can show pelvic organs, muscles and tendons and is quick and easy to do. It does not use ionising radiation. They can also show abnormal fluid collections
